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Добірка наукової літератури з теми "Contact water heater"

Автор: Grafiati

Опубліковано: 30 травня 2022

Оновлено: 31 травня 2022

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Статті в журналах з теми "Contact water heater"

Paik, S. W., K. D. Kihm, S. P. Lee, and D. M. Pratt. "Spatially and Temporally Resolved Temperature Measurements for Slow Evaporating Sessile Drops Heated by a Microfabricated Heater Array." Journal of Heat Transfer 129, no. 8 (October 27, 2006): 966–76. http://dx.doi.org/10.1115/1.2728904.

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The spatially and temporally resolved evaporation phenomena of a slowly evaporating water droplet are investigated using a microfabricated gold heater array consisting of 32 linear heater elements (100 μm wide and 15 mm long, each). Each of the gold microheater elements works both as a temperature sensor and as a heater. The experiment is performed under a constant voltage mode to examine the spatially resolved temperature history of the droplet contact surface for a period starting at initial contact with the heater and lasting to the point of complete dryout. The raw data obtained from the linear array have been tomographically deconvolved so that the radial temperature profile can be determined assuming a circular droplet contact surface.

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HONG, HIKI, JONG HYUN KIM, JAE DONG CHUNG, HIROYUKI KUMANO, and DOUGLAS REINDL. "FREEZE PROTECTION METHOD USING HOT WATER FOR PASSIVE SOLAR WATER HEATING SYSTEM." International Journal of Air-Conditioning and Refrigeration 20, no. 04 (December 2012): 1250021. http://dx.doi.org/10.1142/s2010132512500216.

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In the present work, a new freeze protection method is introduced with intended applications for passive solar water heaters. Though electro-thermal wire heat tracing is popularly used to prevent freezing with subsequent risk of burst, this approach is problematic due to resistance heater failure and excessive electric power consumption. In the experimental device, hot water in thermal storage tank is used to heat the outlet pipe from the tank when the surface temperature of the pipe falls lower than a pre-determined set point. The cold water pipe to the thermal storage tank is installed in direct contact with the hot water pipe, controlling its temperature by conduction with the hot water pipe.

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Marchenko, G. S., and V. A. Makarenko. "SYSTEMS OF AUTONOMOUS HEATING WITH THE USE OF CONTACT WATER HEATERS." Energy Technologies & Resource Saving, no. 2 (June 20, 2019): 11–15. http://dx.doi.org/10.33070/etars.2.2019.02.

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The article proposed technical solutions for the use of a highly efficient contact water heater for heating systems and hot water supply for civil and industrial buildings. The schemes of the heating complex, separate for heating systems, separate for hot water systems and their description are given. The calculations of the economic efficiency of the contact method of heating are given. The expediency of using water contact heating units is shown. Bibl. 5, Fig. 5.

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Unal, C., V. Daw, and R. A. Nelson. "Unifying the Controlling Mechanisms for the Critical Heat Flux and Quenching: The Ability of Liquid to Contact the Hot Surface." Journal of Heat Transfer 114, no. 4 (November 1, 1992): 972–82. http://dx.doi.org/10.1115/1.2911909.

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We investigated the hypothesis that the critical heat flux (CHF) occurs when some point on a heated surface reaches a temperature high enough that liquid can no longer maintain contact at that point, resulting in a gradual but continuous increase in the overall surface temperature for most power-controlled systems. This hypothesis unifies the occurrence of the CHF with the quenching of hot surfaces by relating them to the same concept: the ability of a liquid to contact a hot surface, generally defined as some fraction of the liquid’s homogeneous nucleation temperature, depending on the contact angle. The proposed hypothesis about the occurrence of the CHF is investigated through a study of the boiling mechanism of the second transition region of nucleate pool boiling of water on copper. An idealized two-dimensional transient conduction heat transfer model was developed to investigate the heat transfer mechanism. The initial macrolayer thickness on the dry portion of the heater, in the second transition region, was found to be bounded between 0 and 11 μm. The radius of the dry patch varied from 15 to 23 mm (60 and 92 percent of the heater radius, respectively) for initial macrolayer thicknesses of 0 and 11 μm, respectively. The results indicated that the critical liquid-solid contact temperature at the onset of CHF (the surface temperature at the center of the dry patch) must be lower than the homogeneous nucleation temperature of the liquid for the pool boiling of water on a clean horizontal surface. The liquid-solid contact temperature was dependent on the initial dry patch liquid macrolayer thickness, varying from 180°C to 157°C for initial macrolayer thicknesses of 0 and 11 μm, respectively. Independent assessment of these values shows good agreement with extrapolated contact temperature data at the onset of film boiling. This indicates that the mechanism for the occurrence of the CHF could be similar to the mechanism generally accepted for the quenching of the hot surfaces. Further study of this mechanism to understand better the observed trends in other experimental results show qualitative agreement with those results. These include a significant decrease in the radius of the dry patch to 4 mm (16 percent of the heater radius) when the thermal conductivity of the heater was decreased to that corresponding to nickel. When the thickness of a copper heater was decreased from 10 mm (representing an infinitely thick medium) to 0.1 mm, a dry patch radius of 2.25 mm (9 percent of the heater radius) was found to be sufficient for the temperature at the center of the dry patch to reach the critical contact temperature. These comparisons are felt to provide some understanding as to why the second transition region has been observed only in limited cases.

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Wang, C. H., and V. K. Dhir. "On the Gas Entrapment and Nucleation Site Density During Pool Boiling of Saturated Water." Journal of Heat Transfer 115, no. 3 (August 1, 1993): 670–79. http://dx.doi.org/10.1115/1.2910738.

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A model to describe the effect of wettability on nucleation site density is presented. First, from Helmholtz free energy analysis, a criterion for the entrapment condition in a uniform temperature field is developed. Second, the stability condition of preexisting gas/vapor nuclei during the heating process and the minimum superheat required to initiate nucleation are determined. The prediction of the entrapment condition and the incipient temperature are consistent with the experimental observations made on surfaces having naturally existing cavities. Third, a naturally formed cavity on a heater surface is modeled as a spherical cavity. The cumulative active nucleation site density for a specified contact angle is expressed in terms of the cumulative density of cavities existing on the surface as Na = Pas · Nas where Nas is the heater surface cumulative cavity density with cavity mouth angles less than a specified value and Pas is a function of contact angle and cavity mouth angle. The model successfully predicts active site densities for different contact angles.

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Muriana, P. M., T. Bowser, C. Davidson, M. Tilahun, and D. E. Gibbs. "‘Flash pasteurization’ of contaminated streams using a direct contact gas-fired water heater." Food Microbiology 20, no. 1 (February 2003): 77–82. http://dx.doi.org/10.1016/s0740-0020(02)00100-4.

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Jotshi, C. K., D. Y. Goswami, J. F. Klausner, and S. Malakar. "A water heater using very high-temperature storage and variable thermal contact resistance." International Journal of Energy Research 25, no. 10 (2001): 891–98. http://dx.doi.org/10.1002/er.727.

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Marchuk, Igor, Andrey Karchevsky, Anton Surtaev, and Oleg Kabov. "Heat Flux at the Surface of Metal Foil Heater under Evaporating Sessile Droplets." International Journal of Aerospace Engineering 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/391036.

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Evaporating water drops on a horizontal heated substrate were investigated experimentally. The heater was made of a constantan foil with the thickness of 25 μm and size of 42 × 35 mm2. The temperature of the bottom foil surface was measured by the infrared (IR) camera. To determine the heat flux density during evaporation of liquid near the contact line, the Cauchy problem for the heat equation was solved using the temperature data. The maximum heat flux density is obtained in the contact line region and exceeds the average heat flux density from the entire foil surface by the factor of 5–7. The average heat flux density in the region wetted by the drop exceeds the average heat flux density from the entire foil surface by the factor of 3–5. This fact is explained by the heat influx from the foil periphery to the drop due to the relatively high heat conductivity coefficient of the foil material and high evaporation rate in the contact line region. Heat flux density profiles for pairs of sessile droplets are also investigated.

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Rajan, V. S. V., and R. Tipman. "A Method for Improving the Quality of Bituminous Froth From Water Extraction of Oil Sands." Journal of Energy Resources Technology 114, no. 4 (December 1, 1992): 261–66. http://dx.doi.org/10.1115/1.2905951.

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Bituminous froths produced from the water extraction of oil sands contain significant quantities of sand and water which must be removed prior to upgrading the bitumen to synthetic crude oil. This paper presents a summary of the study of a simple twostep process for removing most of the solid and water contaminants from the bituminous froth. Low-quality froths containing 10–30 percent bitumen at temperatures of 40–70°C were improved in quality to 50–60 percent bitumen by heating the raw froth to ~ 90°C and settling the product in a gravity settler. The gravity settling vessel incorporated unique features for the introduction of the hot froth into the vessel. Two types of froth heaters were tested: a column heater containing a structured grid packing which used live steam injection, and a shell and tube heat exchanger. Heat transfer data were obtained for both types of heaters in the range of froth flow conditions available in the pilot plant. There was no apparent difference between the two heating modes in terms of the froth quality improvement, but the direct contact heater had the benefit of deaerating the froth. Evaluation of the separation efficiency showed that the gravity separation vessel design performed very well, and hence was incorporated into a commercial froth cleaning plant design. The bitumen separation efficiency was the best for froths containing about 20 percent bitumen. There was no apparent improvement in the froth quality for froths containing over 65 percent bitumen.

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Liu, Sheng Wang, Wei Fang Zhang, and Qing Yun Tang. "An Experimental Setup to Test Thermal Contact Conductance Across Solid/Solid Interface." Advanced Materials Research 291-294 (July 2011): 1293–96. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1293.

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This article describes an experimental setup to measure the TCC between interfaces of two contact solid materials. This apparatus consists of loading and load bearing subsystem, water-cooling subsystem, heating subsystem, temperature measurement and control subsystem and thermal insulation subsystem. A new kind of design scheme of the compensation heater is put forward. An experimental investigation of TCC is conducted with pressed pairs of TC4/30CrMnSi contacts in the range 40~140MPa. The results show that TCC over this condition increases with load, and is greater in the process of unloading than that of loading under the same condition.

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Більше джерел

Дисертації з теми "Contact water heater"

Стіцурін, Владислав Петрович. "Котельня на базі контактних водонагрівачів для теплопостачання житлового масиву в м. Миргороді". Bachelor's thesis, КПІ ім. Ігоря Сікорського, 2019. https://ela.kpi.ua/handle/123456789/28237.

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Дипломний проект першого (бакалаврського) рівня вищої освіти на тему: «Котельня на базі контактних водонагрівачів для теплопостачання житлового масиву в м. Миргороді»: пояснювальна записка на 66 с., 13 рис., 5 табл., 8 бібліографічних найменувань; креслення – 3 арк. ф. А1. Мета проекту – розробити котельню для теплопостачання житлового масиву у місті Миргороді та підібрати котлоагрегати. У дипломному проекті було розраховано максимальні, середні та річні витрат теплоти на опалення, вентиляцію і гаряче водопостачання споживачів житлових та громадських будівель, відповідно до завдання. За результатами цих розрахунків у якості теплогенеруючих пристроїв були підібрані котли загальною номінальною потужністю 3,4 МВт Також була розроблена теплова схема із закритою системою теплопостачання, на основі якої було проведено аеродинамічний та гідравлічний розрахунки, визначено діаметри основних трубопроводів котельні та швидкості теплоносіїв в них. Залежно від потрібного тиску та об'ємної подачі було підібрано допоміжне обладнання, зокрема тягодуттєві пристрої та насоси. За температурним режимом, масовими витратами гріючої і нагріваної води та тепловій потужності нагрівача, було підібрано пластинчастий теплообмінник для системи ГВП. Було надано рекомендації з охорони праці при монтажі обладнання котельні та технічні рішення та організаційні заходи з виробничої санітарії. На кресленнях наведені компоновка обладнення котельні, теплова схема котельні та контактний водонагрівач.
Degree project of the first (Bachelor) level of higher education on the topic: «Boiler room on the basis of contact water heaters for heat supply of the residential area in Mirgorod»: explanatory note for 66 pages, 13 figures, 5 tables, 8 bibliographic names; drawings - 3 s. f. A1 The purpose of the Вegree is to develop a boiler house for heat supply of a residential area in the city of Mirgorod and to pick up boiler units. In the diploma project, maximum, average and annual heat consumption for heating, ventilation and hot water supply of residential and public buildings consumers was calculated in accordance with the task. As a result of these calculations, boilers with a total rated power of 3.4 MW were selected as heat-generating devices. Also, a thermal circuit with a closed system of heat supply was developed, on the basis of which aerodynamic and hydraulic calculations were carried out, the diameters of the main pipelines of the boiler house and the speed of the heat carrier in them were determined. Depending on the pressure and volume required, auxiliary equipment, such as payload units and pumps, was selected. Under the temperature regime, the massive consumption of heating and hot water and the heat capacity of the heater, a plate heat exchanger for the system of high-pressure cookers was selected. The recommendations were given on the safety of work during the installation of boiler equipment and technical solutions and organizational measures for industrial sanitation. The drawings show the arrangement of the boiler equipment, the heating circuit of the boiler house and the contact water heater.
Дипломный проект первого (бакалаврского) уровня высшего образования на тему: «Котельная на базе контактных водонагревателей для теплоснабжения жилого массива в г. Миргороде»: объяснительная записка на 66 с., 13 рис., 5 табл., 8 библиографических наименований, чертежи - 3 л. ф. А1. Цель проекта - разработать котельную для теплоснабжения жилого массива в городе Миргороде и подобрать котлоагрегаты. В дипломном проекте было рассчитано максимальные, средние и годовые расхода теплоты на отопление, вентиляцию и горячее водоснабжение потребителей жилых и общественных зданий, в соответствии с заданием. По результатам этих расчетов в качестве теплогенерирующих устройств были подобраны котлы общей номинальной мощностью 3,4 МВт Также была разработана тепловая схема с закрытой системой теплоснабжения, на основе которой был проведен аэродинамический и гидравлический расчеты, определены диаметры основных трубопроводов котельной и скорости теплоносителей в них. В зависимости от нужного давления и объемной подачи было подобрано вспомогательное оборудование, в частности тягодуттеви устройства и насосы. По температурному режиму, массовыми расходами греющей и нагревов воды и тепловой мощности нагревателя, было подобрано пластинчатый теплообменник для ГВС. Были предоставлены рекомендации по охране труда при монтаже оборудования котельной и технические решения и организационные мероприятия по производственной санитарии. На чертежах приведены компоновка оборудования котельной, тепловая схема котельной и контактный водонагреватель.

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Dery, Tyler Gregory. "Modeling Sensible Heat Driven Direct Contact Membrane Distillation Treatment of Oilfield Produced Water." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2022.

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A model was developed for predicting the performance of direct contact membrane distillation (DCMD) to evaluate the feasibility of using sensible heat to drive DCMD treatment of oilfield produced water. Algorithms for performance prediction of instantaneous and counter-current DCMD flow were developed. These algorithms used equation-based models of heat transfer, mass transfer, concentration polarization, and counter-current flow to predict performance of DCMD systems. The performance prediction model was validated against experimental data from the literature, and limitations to the accuracy of predictions were identified. The model was applied to evaluate performance sensitivity to nine operational parameters. The model was applied to evaluate the feasibility of sensible heat driven DCMD treatment of produced water using DCMD alone and using a reverse osmosis-DCMD hybrid system. The largest water recoveries that were energetically favorable (lower energy demand than reverse osmosis) for sensible heat driven DCMD produced water treatment were 0.5% and 0.75% for 1% and 3.5% NaCl feeds, respectively. As feed NaCl concentration increased, higher recoveries were energetically favorable over RO. A bulk NaCl concentration of 6% was evaluated to simulate the feasibility of further treatment of reverse osmosis retentate using sensible heat driven DCMD. Compared to treatment alternatives of multiple-stage flash distillation (MSF) and multiple-effect distillation (MED), recoveries up to 2.5% were favorable and up to 4.0% were competitive. Due to model limitations, the performance of optimal conditions for sensible heat driven DCMD produced water treatment could not be predicted, so the recoveries presented in this work are likely lower than the expected recoveries for optimal field conditions. Water recovery of produced water using sensible heat driven DCMD is limited thermodynamically to low recoveries, but any treatment using sensible heat that is energetically favorable reflects the utilization of two waste streams (produced water and waste heat) to produce high quality water. Using sensible heat to drive produced water treatment could be useful for providing small quantities of usable water, but would only result in a very small reduction of the volume of produced water needing to be disposed.

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Petrovic-de, With Anka. "Characterisation and modelling of flow mechanisms for direct contact condensation of steam injected into water." Thesis, University of Hertfordshire, 2006. http://hdl.handle.net/2299/14345.

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Direct contact condensation of steam injected into water is a special mode of condensation where condensation occurs on the interface between steam and water. This type of condensation forms an essential part of various industrial applications and correct prediction and modelling of the condensation behaviour is crucial to obtain an optimised design of such devices. While present prediction models for direct contact condensation are valid for a limited range of flow conditions only, the work presented in this thesis provides improved models for direct contact condensation. The models are developed in the form of diagrams and include: a condensation regime diagram, for predicting the condensation behaviour, a steam plume length diagram, for predicting the penetration distance of steam into water, and a heat transfer coefficient diagram. These models are derived using a wide range of data and therefore provide more accurate predictions compared with alternative models available in literature. In contrast to present models, the derived models presented in this work are constructed using an additional physical parameter to describe the process. The diagrams are validated against independent experiments and demonstrate close agreement. Furthermore, the predictions from the condensation regime diagram and steam plume length diagram are self-consistent. The models developed in this study are capable of predicting condensation behaviour for a wide range of initial conditions and can be used in conjunction with computational fluid dynamics techniques for direct contact condensation.

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Wong, Wai-yee Amy, and 黃慧兒. "The effect of water content of heat-cured acrylic resin on processing shrinkage." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31954091.

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Wong, Wai-yee Amy. "The effect of water content of heat-cured acrylic resin on processing shrinkage." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21461764.

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Romine, William Whittington Alan G. "Flow and heat transfer properties of Mono Craters rhyolites effects of temperature, water content, and crystallinity /." Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/5685.

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Анотація:

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 5, 2009). Thesis advisor: Dr. Alan G. Whittington. Includes bibliographical references.

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Hansson, Klas. "Water and Heat Transport in Road Structures : Development of Mechanistic Models." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4822.

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The coupled transport of water and heat, involving freezing and thawing, in the road structure and its immediate environment is important to consider for optimal design and maintenance of roads and when assessing solute transport, of e.g. de-icing salt, from roads. The objective of this study was to develop mechanistic models, and measurement techniques, suitable to describe and understand water flow and heat flux in road structures exposed to a cold climate.

Freezing and thawing was accounted for by implementing new routines in two numerical models (HYDRUS1D/2D). The sensitivity of the model output to changes in parameter values and operational hydrological data was investigated by uncertainty and sensitivity analyses. The effect of rainfall event characteristics and asphalt fractures on the subsurface flow pattern was investigated by scenario modelling. The performance of water content reflectometers (WCR), measuring water content, was evaluated using measurements in two road structure materials. A numerical model was used to simulate WCR sensor response. The freezing/thawing routines were stable and provided results in agreement with laboratory measurements. Frost depth, thawing period, and freezing-induced water redistribution in a model road was greatly affected by groundwater level and type of subgrade. The simulated subsurface flow patterns corresponded well with published field observations. A new method was successful in enabling the application of time domain reflectometer (TDR) calibration equations to WCR output. The observed distortion in sampling volume for one of the road materials could be explained by the WCR sensor numerical model. Soil physical, hydrological, and hydraulic modules proved successful in simulating the coupled transport of water and heat in and on the road structure. It was demonstrated in this thesis that numerical models can improve the interpretation and explanation of measurements. The HYDRUS model was an accurate and pedagogical tool, clearly useful in road design and management.

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Persson, Tony. "Evaporation and Heat-flux Aggregation in Heterogeneous Boreal Landscapes." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4326.

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The boreal forests represent 8 % of all forested areas on the earth and have a significant role in the control of greenhouse gases and an impact on global climate change. The main objective of this thesis is to increase the understanding of how evaporation and heat-flux processes in the boreal forest zone are affecting the regional and global climate.

A meteorological mesoscale model with an advanced land-surface parameterization has been utilized to study aggregation of fluxes of water vapour and heat. The model has been compared against four other methods for flux estimation in a southern boreal landscape. The results show that the mesoscale model is successfully reproducing 24-hour averages of fractionally weighted mast measurements of sensible and latent heat flux.

The model was also evaluated against in-situ observations of surface fluxes and other meteorological variables. The results reveal that a correct initialization of soil moisture is crucial to simulate a realistic partitioning of the sensible and latent heat fluxes. Significant differences in surface fluxes and friction velocities between two apparently similar forest sites indicate the need for careful assessment of areal representativity when comparing mesoscale model results with in-situ observations.

A parameterization for the absorption of solar radiation of high-latitude sparse forests was implemented and tested in the model that significantly improved the simulation of high wintertime midday sensible heat fluxes. A scheme for heat storage in vegetation was also implemented which improved the results, but the scheme needs further evaluation for high latitude forests.

Two commonly used strategies for the description of land-surface heterogeneity, the effective parameter approach and the mosaic approach, were tested in the mesoscale model against airborne observations of sensible and latent heat fluxes. The results show that the mosaic approach produces better results especially when small lakes are present in model grid-squares.

Norra halvklotets barrskogsbälte representerar 8 % av all skogsbeklädd mark på jorden och har stor betydelse för kontrollen av växthusgaser och påverkan på globala klimatförändringar. Syftet med denna avhandling är att öka förståelsen av hur avdunstning och värmeflöden i den boreala skogszonen påverkar klimatet regionalt och globalt.

En meteorologisk mesoskalemodell med en avancerad landyteparameterisering har använts för att studera aggregering av avdunstning och värmeflöden. Modellen jämfördes med fyra andra metoder för uppskattning av värmeflöden i den boreala skogszonens södra delar. Resultaten visade att mesoskalemodellen reproducerar 24-timmarsmedelvärden av sensibelt och latent värmeflöde från areellt viktade mastmätningar med bra resultat.

Modellen utvärderades även mot markbaserade mätningar av sensibelt och latent värme och andra meteorologiska variabler. Resultaten visar att en korrekt initialisering av markvatteninnehållet är avgörande för att simulera en realistisk uppdelning av de sensibla och latenta värmeflödena. Markanta skillnader i markyteflöden och friktionshastigheter mellan två liknande skogsmätstationer påvisar nödvändigheten av en noggrann bedömning av den areella representativiteten när man jämför resultat från mesoskalemodellen med markbaserade mätningar.

En parameterisering för absorption av solstrålning i glesa skogsbestånd på höga breddgrader infördes och testades i modellen vilket markant förbättrade simuleringen av de höga sensibla värmeflöden som observerats vid middagstid på vintern. Ett uttryck för att beskriva värmelagring i vegetationen infördes också vilket förbättrade resultaten, men uttrycket behöver vidare utvärdering för skogsbestånd på höga breddgrader.

Två ofta använda strategier för att beskriva markytans heterogenitet, effektiva parametermetoden och mosaikmetoden, testades i mesoskalemodellen mot flygburna observationer av sensibla och latenta värmeflöden. Resultaten visar att mosaikmetoden ger bättre resultat särskilt när mindre sjöar förekommer i modellrutorna.

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Hauck, Tiburski Julia. "Comprehensive study of the heat resistance of dried Bacillus subtilis spores." Thesis, Dijon, 2013. http://www.theses.fr/2013DIJOS071/document.

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En réponse à un stress nutritif, les espèces du genre Bacillus sont susceptibles de former desspores métaboliquement dormantes résistantes à d’autres formes de stress. Ces spores peuventse retrouver à forte concentration dans beaucoup d’aliments secs, ce qui peut provoquer desintoxications alimentaires ou dégrader les aliments lorsqu’ils sont réhydratés. Comme leurdestruction est très difficile, la plupart des méthodes couramment utilisées pour décontaminerles aliments secs sont peu efficaces. L’objectif de ce travail est de comprendre l’influence del’hydratation de la spore sur l’inactivation des spores sèches de B. subtilis. Une étudefondamentale a été menée en soumettant les spores placées dans les capsules d’AnalyseEnthalpique Différentielle à différent traitements thermiques et en associant simultanémentles thermogrammes obtenus à la viabilité des spores traitées. Les résultats montrent lapersistance d’une teneur en eau relativement élevée dans le protoplaste des spores équilibréesà faible aw (0,13). De plus, une relation forte a été mise en évidence entre la teneur en eau duprotoplaste de la spore et sa sensibilité thermique. La spectroscopie IR à transformée deFourier a montré que cette sensibilité est fortement reliée à la dénaturation/agrégation desprotéines et à la libération de l’acide dipicolinique. Ces résultats ont finalement permis dedévelopper un procédé d’inactivation thermique sous pression (entre 2 et 7 bar) des sporessèches. Le maintien d’une pression d’azote dans le réacteur chauffé permet d’empêcherl’évaporation de l’eau du protoplaste des spores et donc de favoriser leur inactivation. A termeet après développement, ce procédé peut être un moyen original de décontaminationd’aliments secs
In response to starvation, species from the genre Bacillus are able to form metabolicallydormant spores which are very resistant to multiple forms of stress. They are found in quitehigh concentrations in some dried foods which, upon rehydration, may lead to food deterioration or food-borne diseases. Moreover, their destruction is rather difficult and mostof the techniques commonly used to treat dry foods result in a very low spore inactivation.The aim of this work is to better understand the role spore hydration in the inactivation ofdried Bacillus subtilis spores. A fundamental study was conducted using DifferentialScanning Calorimetry pans as reactors to perform a heat treatment in dried spores andsimultaneously relate the thermograms to spore viability. Results show the persistence of arelatively high water concentration in the core of extremely dry spores. Besides, a strongrelation between this core water concentration and spore thermal sensitivity wasdemonstrated. This destruction was found to be highly related to proteindenaturation/aggregation and dipicolinic acid release through Fourier Transform InfraredSpectroscopy analysis. From this fundamental study, a procedure for the inactivation of driedspores using low pressures (2-7 bar) and high temperature was developed. The systemconsisted of a heated reactor in which gaseous nitrogen was compressed to prevent theevaporation of water from the spores and so favor spore inactivation (> 5 log10). This methodof inactivation could be an interesting new way to optimize the decontamination of driedfoods

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Alanazi, Mohammed Awwad. "Non-invasive Method to Measure Energy Flow Rate in a Pipe." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/103179.

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Current methods for measuring energy flow rate in a pipe use a variety of invasive sensors, including temperature sensors, turbine flow meters, and vortex shedding devices. These systems are costly to buy and install. A new approach that uses non-invasive sensors that are easy to install and less expensive has been developed. A thermal interrogation method using heat flux and temperature measurements is used. A transient thermal model, lumped capacitance method LCM, before and during activation of an external heater provides estimates of the fluid heat transfer coefficient h and fluid temperature. The major components of the system are a thin-foil thermocouple, a heat flux sensor (PHFS), and a heater. To minimize the thermal contact resistance R" between the thermocouple thickness and the pipe surface, two thermocouples, welded and parallel, were tested together in the same set-up. Values of heat transfer coefficient h, thermal contact resistance R", time constant �[BULLET], and the water temperature �[BULLET][BULLET], were determined by using a parameter estimation code which depends on the minimum root mean square RMS error between the analytical and experimental sensor temperature values. The time for processing data to get the parameter estimation values is from three to four minutes. The experiments were done over a range of flow rates (1.5 gallon/minute to 14.5 gallon/minute). A correlation between the heat transfer coefficient h and the flow rate Q was done for both the parallel and the welded thermocouples. Overall, the parallel thermocouple is better than the welded thermocouple. The parallel thermocouple gives small average thermal contact resistance average R"=0.00001 (m2.�[BULLET][BULLET]/W), and consistence values of water temperature and heat transfer coefficient h, with good repeatability and sensitivity. Consequently, a non-invasive energy flow rate meter or (BTU) meter can be used to estimate the flow rate and the fluid temperature in real life.
MS

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Книги з теми "Contact water heater"

Brazeau, Stéphanie, and Nicholas H. Ogden, eds. Earth observation, public health and one health: activities, challenges and opportunities. Wallingford: CABI, 2022. http://dx.doi.org/10.1079/9781800621183.0000.

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Abstract This book contains 4 chapters that discuss in the context of both the One Health concept and the SDG initiative, remote sensing can provide solutions to the priority of assessing and monitoring public health risks, and it can play an important role in supporting decision making to reduce health risks within our shared ecosystems. The growing awareness of complex but causal interactions among these realms has motivated professionals in a wide range of sectors to adopt the One Health approach, which promotes intersectoral collaboration to address health issues at the human-animal-environment interface. In its 2030 Agenda for Sustainable Development, the United Nations specifically identifies "strengthening the capacity of all countries, in particular developing countries, for early warning, risk reduction and management of national and global health risks" as part of their Good Health and Well-being Sustainable Development Goal (SDG). As examples presented in this book reveal, the risk of infectious disease emergence increases with a wide range of conditions and variables, including those associated with humans, animals, climate, and the environment. This book examines several priority themes to which EO and geomatics can make important contributions: mosquito-borne and tick-borne diseases; water-borne diseases; air quality and extreme heat effects; geospatial indicators of vulnerable human populations.

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I, Merts, and Meat Industry Research Institute of New Zealand., eds. Thawing of meat in water and by direct contact with heated plates. Hamilton, N.Z: MIRINZ Food Technology & Research, 1998.

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Benestad, Rasmus. Climate in the Barents Region. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.655.

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The Barents Sea is a region of the Arctic Ocean named after one of its first known explorers (1594–1597), Willem Barentsz from the Netherlands, although there are accounts of earlier explorations: the Norwegian seafarer Ottar rounded the northern tip of Europe and explored the Barents and White Seas between 870 and 890 ce, a journey followed by a number of Norsemen; Pomors hunted seals and walruses in the region; and Novgorodian merchants engaged in the fur trade. These seafarers were probably the first to accumulate knowledge about the nature of sea ice in the Barents region; however, scientific expeditions and the exploration of the climate of the region had to wait until the invention and employment of scientific instruments such as the thermometer and barometer. Most of the early exploration involved mapping the land and the sea ice and making geographical observations. There were also many unsuccessful attempts to use the Northeast Passage to reach the Bering Strait. The first scientific expeditions involved F. P. Litke (1821±1824), P. K. Pakhtusov (1834±1835), A. K. Tsivol’ka (1837±1839), and Henrik Mohn (1876–1878), who recorded oceanographic, ice, and meteorological conditions.The scientific study of the Barents region and its climate has been spearheaded by a number of campaigns. There were four generations of the International Polar Year (IPY): 1882–1883, 1932–1933, 1957–1958, and 2007–2008. A British polar campaign was launched in July 1945 with Antarctic operations administered by the Colonial Office, renamed as the Falkland Islands Dependencies Survey (FIDS); it included a scientific bureau by 1950. It was rebranded as the British Antarctic Survey (BAS) in 1962 (British Antarctic Survey History leaflet). While BAS had its initial emphasis on the Antarctic, it has also been involved in science projects in the Barents region. The most dedicated mission to the Arctic and the Barents region has been the Arctic Monitoring and Assessment Programme (AMAP), which has commissioned a series of reports on the Arctic climate: the Arctic Climate Impact Assessment (ACIA) report, the Snow Water Ice and Permafrost in the Arctic (SWIPA) report, and the Adaptive Actions in a Changing Arctic (AACA) report.The climate of the Barents Sea is strongly influenced by the warm waters from the Norwegian current bringing heat from the subtropical North Atlantic. The region is 10°C–15°C warmer than the average temperature on the same latitude, and a large part of the Barents Sea is open water even in winter. It is roughly bounded by the Svalbard archipelago, northern Fennoscandia, the Kanin Peninsula, Kolguyev Island, Novaya Zemlya, and Franz Josef Land, and is a shallow ocean basin which constrains physical processes such as currents and convection. To the west, the Greenland Sea forms a buffer region with some of the strongest temperature gradients on earth between Iceland and Greenland. The combination of a strong temperature gradient and westerlies influences air pressure, wind patterns, and storm tracks. The strong temperature contrast between sea ice and open water in the northern part sets the stage for polar lows, as well as heat and moisture exchange between ocean and atmosphere. Glaciers on the Arctic islands generate icebergs, which may drift in the Barents Sea subject to wind and ocean currents.The land encircling the Barents Sea includes regions with permafrost and tundra. Precipitation comes mainly from synoptic storms and weather fronts; it falls as snow in the winter and rain in the summer. The land area is snow-covered in winter, and rivers in the region drain the rainwater and meltwater into the Barents Sea. Pronounced natural variations in the seasonal weather statistics can be linked to variations in the polar jet stream and Rossby waves, which result in a clustering of storm activity, blocking high-pressure systems. The Barents region is subject to rapid climate change due to a “polar amplification,” and observations from Svalbard suggest that the past warming trend ranks among the strongest recorded on earth. The regional change is reinforced by a number of feedback effects, such as receding sea-ice cover and influx of mild moist air from the south.

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Jha, Vivekanand. Acute kidney injury in the tropics. Edited by Norbert Lameire. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0241.

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The spectrum of acute kidney injury (AKI) encountered in the hospitals of the tropical zone countries is different from that seen in the non-tropical climate countries, most of which are high-income countries. The difference is explained in large part by the influence of environment on the epidemiology of human disease. The key features of geographic regions falling in the tropical zones are climatic, that is, high temperatures and absence of winter frost, and economic, that is, lower levels of income. The causes and presentation of tropical AKI reflect these prevailing cultural, socioeconomic, climatic, and eco-biological characteristics.Peculiarities of tropical climate support the propagation of several infectious organisms that can cause AKI and the disease-transmitting vectors. In contrast to the developed world, where AKI usually develops in already hospitalized patients with multiorgan problems and iatrogenic factors play a major role, tropical AKI is acquired in the community due to issues of public health importance such as safe water, sanitation, infection control, and good obstetric practices. Infections such as malaria, leptospirosis, typhus, HIV, and diarrhoeal diseases; envenomation by animals or insects; ingestion of toxic herbs or chemicals; intravascular haemolysis; poisoning; and obstetric complications form the bulk of AKI in the tropics. Poor access to modern medical facilities and practices such as seeking treatment from traditional faith-healers contribute to poor outcomes.AKI extracts macro- and microeconomic costs from the affected population and reduces productivity. Improvement in the outcomes of tropical AKI requires improvement in basic public health through effective interventions, and accessibility to effective medical care.

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Frid, Christopher L. J., and Bryony A. Caswell. Marine Pollution. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198726289.001.0001.

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We use more than 100 000 chemicals in our daily lives to promote health, treat disease, facilitate transportation, use in industrial processes, grow food and access clean water. While these developments have improved human lives, many of these compounds ultimately end up in our seas and oceans where they represent a threat to marine life, ourselves and our continued use of the oceans to treat our waste, provide us with food and offer us recreation. Many of the pollution problems of previous decades seem to have been resolved, in the developed world, or at least managed to minimise their environmental impacts. However, despite treatments being available that reduce their damaging qualities, a potent mixture of toxic compounds enter the marine environment every day along with other potentially harmful additions including heat, noise and light and non-native species. The question thus arises: is pollution a problem that has really been solved? How well are we managing traditional pollutants? What are the challenges we still face today? What are the upcoming marine pollution challenges that face society? This volume describes the different marine pollutants, the science behind measuring their ecological impacts and how they are monitored in the environment, including traditional and new management approaches. This is an up-to-date account of marine pollution within the broad ecological and social context of a growing, technologically advanced, global population.

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Hopkins, Graeme, and Christine Goodwin. Living Architecture. CSIRO Publishing, 2011. http://dx.doi.org/10.1071/9780643103078.

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Extensively illustrated with photographs and drawings, Living Architecture highlights the most exciting green roof and living wall projects in Australia and New Zealand within an international context. Cities around the world are becoming denser, with greater built form resulting in more hard surfaces and less green space, leaving little room for vegetation or habitat. One way of creating more natural environments within cities is to incorporate green roofs and walls in new buildings or to retrofit them in existing structures. This practice has long been established in Europe and elsewhere, and now Australia and New Zealand have begun to embrace it. The installation of green roofs and walls has many benefits, including the management of stormwater and improved water quality by retaining and filtering rainwater through the plants’ soil and root uptake zone; reducing the ‘urban heat island effect’ in cities; increasing real estate values around green roofs and reducing energy consumption within the interior space by shading, insulation and reducing noise level from outside; and providing biodiversity opportunities via a vertical link between the roof and the ground. This book will appeal to a wide range of readers, from students and practitioners of architecture, landscape architecture, urban planning and ecology, through to members of the community interested in how they can more effectively use the rooftops and walls of their homes or workplaces to increase green open space in the urban environment.

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Bridges, John C. Evolution of the Martian Crust. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190647926.013.18.

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This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Mars, which has a tenth of the mass of Earth, has cooled as a single lithospheric plate. Current topography gravity maps and magnetic maps do not show signs of the plate tectonics processes that have shaped the Earth’s surface. Instead, Mars has been shaped by the effects of meteorite bombardment, igneous activity, and sedimentary—including aqueous—processes. Mars also contains enormous igneous centers—Tharsis and Elysium, with other shield volcanoes in the ancient highlands. In fact, the planet has been volcanically active for nearly all of its 4.5 Gyr history, and crater counts in the Northern Lowlands suggest that may have extended to within the last tens of millions of years. Our knowledge of the composition of the igneous rocks on Mars is informed by over 100 Martian meteorites and the results from landers and orbiters. These show dominantly tholeiitic basaltic compositions derived by melting of a relatively K, Fe-rich mantle compared to that of the Earth. However, recent meteorite and lander results reveal considerable diversity, including more silica-rich and alkaline igneous activity. These show the importance of a range of processes including crystal fractionation, partial melting, and possibly mantle metasomatism and crustal contamination of magmas. The figures and plots of compositional data from meteorites and landers show the range of compositions with comparisons to other planetary basalts (Earth, Moon, Venus). A notable feature of Martian igneous rocks is the apparent absence of amphibole. This is one of the clues that the Martian mantle had a very low water content when compared to that of Earth.The Martian crust, however, has undergone hydrothermal alteration, with impact as an important heat source. This is shown by SNC analyses of secondary minerals and Near Infra-Red analyses from orbit. The associated water may be endogenous.Our view of the Martian crust has changed since Viking landers touched down on the planet in 1976: from one almost entirely dominated by basaltic flows to one where much of the ancient highlands, particularly in ancient craters, is covered by km deep sedimentary deposits that record changing environmental conditions from ancient to recent Mars. The composition of these sediments—including, notably, the MSL Curiosity Rover results—reveal an ancient Mars where physical weathering of basaltic and fractionated igneous source material has dominated over extensive chemical weathering.

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Частини книг з теми "Contact water heater"

Li, Feng, Lin Duanmu, Lin Fu, and Xiling Zhao. "Performances of Gas-Water Direct-Contact Heat Transfer." In Springer Proceedings in Energy, 63–77. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-00662-4_6.

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Winkelman, L., A. McAuley, G. Sims, B. Abbott, and J. McPhee. "Residual Water Content in a Lyophilized, Heated Coagulation Factor Concentrate." In Cryopreservation and low temperature biology in blood transfusion, 215–24. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4613-1515-5_20.

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Prakhova, M. Yu, E. A. Khoroshavina, and A. N. Krasnov. "Control System for Gas Transfer by Gas Gathering Header in the Context of Water Accumulation." In Lecture Notes in Electrical Engineering, 189–96. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-39225-3_21.

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Kluitenberg, Gerard J., and Joshua L. Heitman. "Effect of forced convection on soil water content measurement with the dual-probe heat-pulse method." In Environmental Mechanics: Water, Mass and Energy Transfer in the Biosphere, 275–83. Washington, D. C.: American Geophysical Union, 2002. http://dx.doi.org/10.1029/129gm23.

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Tabatabaei, Seyed Amin, and Jan Treur. "Analysis of Electricity Usage for Domestic Heating Based on an Air-to-Water Heat Pump in a Real World Context." In 2nd International Congress on Energy Efficiency and Energy Related Materials (ENEFM2014), 587–96. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-16901-9_72.

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Graham, Alan. "Context." In Late Cretaceous and Cenozoic History of North American Vegetation (North of Mexico). Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195113426.003.0006.

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The interaction between vegetation and the environment over time is one of the most complex of the Earth’s integrated systems. In addition to the direct methodologies of paleopalynology and paleobotany, there are other techniques that provide independent sources of information for interpreting this interaction. These include paleotemperature analysis, sea-level changes, and faunal history. The first two are also forcing mechanisms as discussed in Chapter 2, but for this survey the summary curves can also serve as convenient context information. Each is a vast subject with an extensive literature, and all are presently generating considerable discussion. For paleotemperature analysis, unsettled issues include the extent of temperature change in equatorial waters during the Early and Middle Tertiary, which would affect the poleward transport of heat by conveyer-belt mechanisms. Estimates range from surface waters as warm or warmer than the present to considerably cooler. For the Neogene, CLIMAP estimates based on the ecology of coccolithophores, diatoms, radiolarians, and especially foraminifera are that temperatures in the tropics did not cool significantly; modeling results, terrestrial paleontological evidence, and new Barbados coral data suggest they cooled by ~5°C. There is uncertainty as to when glaciations began on Antarctica; recent estimates range from the Early Eocene to late Middle Eocene to Middle Oligocene (45-35 Ma; Birkenmajer, 1990; Leg 119 Shipboard Scientific Party, 1988). This affects interpretation of 18O values during the Paleogene because they could reflect temperature alone or could be due to ocean water temperature and ice volume changes. Another challenge is to unravel the extent to which benthic temperature records track insolation-induced changes in water temperature versus new thresholds in ocean bottom-water circulation. Discussions of sea-level fluctuation are presently focused on their causes during the preglacial Early Cenozoic. In faunal history the timing of the North American Land Mammal Ages (NALMAs) or provincial ages are being revised. For vegetational history much of the older literature describes events in terms of geofloras, but this conceptual context, at minimum, requires substantial renovation, and the boreotropical hypothesis is emerging as an alternative for envisioning biotic events in the high northern latitudes.

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Lu, Yili, Wei Peng, Tusheng Ren, and Robert Horton. "Applications of Thermo-TDR Sensors for Soil Physical Measurements." In Soil Science - Emerging Technologies, Global Perspectives and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.100285.

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Advanced sensors provide new opportunities to improve the understanding of soil properties and processes. One such sensor is the thermo-TDR sensor, which combines the functions of heat pulse probes and time domain reflectometry probes. Recent advancements in fine-scale measurements of soil thermal, hydraulic, and electrical properties with the thermo-TDR sensor enable measuring soil state variables (temperature, water content, and ice content), thermal and electrical properties (thermal diffusivity, heat capacity, thermal conductivity, and bulk electrical conductivity), structural parameters (bulk density and air-filled porosity) and fluxes (heat, water, and vapor) simultaneously. This chapter describes the theory, methodology, and potential applications of the thermo-TDR technique.

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Zaporozhets, Valentina. "Preserving and Adapting Non-Traditional Practices: Family Stories of the Healer’s Descendants." In Slavic & Jewish Cultures Dialogue Similarities Differences, 338–50. Sefer; Institute of Slavic Studies, Russian Academy of Sciences, 2020. http://dx.doi.org/10.31168/2658-3356.2020.17.

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The publication presents the materials of field research conducted by the author in 2000 in the Yaroslavl region (town Poshekhonye). The author investigates the folk medicine treatment methods of representatives of several generations of the same family, whose members are descendants of a famous local healer of the 19th century. In the published texts, we are talking about a variety of practices used in everyday life by members of this family: psychological assistance (hypnosis, extrasensory methods); non-contact massage; accompanying practices (fortune-telling, collecting herbs for magical actions); magic rituals (transfer of “knowledge”, love spells, magic with water).

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A. Harris, Stuart. "Causes and Mechanisms of Global Warming/Climate Change." In The Nature, Causes, Effects and Mitigation of Climate Change on the Environment. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.101416.

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Comparison of the average mean surface air temperature around the world during 1951–1978 with that for 2010–2019 shows that the bulk of the warming is around the North Atlantic/Arctic region in contrast to the Antarctic ice sheet. Obviously, the temperature change is not global. Since there is a substantial difference between solar heat absorption between the equator and the poles, heat must be moving to the North Pole by surface ocean currents and tropical cyclones. The cold, dry Arctic air coming from Siberia picks up heat and moisture from the open oceans, making the sea water denser so that the warm water sinks slowly down to c. 2000 m. A deep-water thermohaline flow (THC) transports the excess hot (c. 18°C) water south to Antarctica. It is replaced by a cold (c. 2°C) surface water from that area. The latter quickly cool western Europe and Siberia, and glaciers start to advance in Greenland within about 10 years. The THC flow decreases in Interglacials, causing the increased build-up of heat in the Northern Hemisphere (c. 60% currently stored in the Atlantic Ocean), and the ice cover in the Arctic Ocean thaws. Several such cycles may take place during a single major cold event.

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"Chapter 34. Electricity,Water, Gas And Heat Supply Contracts." In The Draft Civil Code of the People's Republic of China, 259–61. Brill | Nijhoff, 2011. http://dx.doi.org/10.1163/ej.9789004190429.i-550.105.

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Тези доповідей конференцій з теми "Contact water heater"

Gotovsky, M. A., V. F. Ermolov, V. E. Mikhailov, Yu G. Sukhorukov, and N. N. Trifonov. "Analysis of the Possibility of Water Induction in Turbine From Direct Contact Water Heater at Load Shedding Power." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63833.

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Direct-contact heaters of feed water are especially popular as low-pressure heaters (LPH). These devices are successfully used in Russia during a long time both for conventional and nuclear power plants. Moreover, abilities of such devices to operate as deaerators led to the development deaeratorless schemes. One of most important conditions of reliable operating of such LPH is the prevention of damage of steam turbines, because of back flow of wet steam to the turbine. In this paper processes of boiling up are considered in direct contact LPH-2 which occur during stopping of turbine and its specific features concerned with dependence of sonic speed two-phase flow on vapor and liquid volumetric portions during flow enter in compensating tubes. Computer analysis showed, that the rate of generation of steam in the superheated water depends on the pressure exceptionally strong. Zone of churn flow regime, which is formed in the upper part of the condensate tank appears very sensitive instrument of flow rate control. As it is shown in such a situation, the system becomes self-governing and will not miss a steam consumption, which leads to the entrance some part of churn regime zone to pressure equalizing tubes. The calculations show that the safety can be ensure even in the conditions when backpressure valve absent. Such the conclusion is confirmed by the experience on operation direct contact LPH in Russian power plants.

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Sulaiman, Muhamad Zuhairi, Masahiro Takamura, Kazuki Nakahashi, and Tomio Okawa. "Boiling Heat Transfer and Critical Heat Flux Enhancement of Upward- and Downward-Facing Heater in Nanofluids." In 2012 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icone20-power2012-54842.

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Boiling heat transfer (BHT) and critical heat flux (CHF) performance were experimentally studied for saturated pool boiling of water-based nanofluids. In present experimental works, copper heaters of 20 mm diameter with titanium-oxide (TiO2) nanocoated surface were produced in pool boiling of nanofluid. Experiments were performed in both upward and downward facing nanofluid coated heater surface. TiO2 nanoparticle was used with concentration ranging from 0.004 until 0.4 kg/m3 and boiling time of tb = 1, 3, 10, 20, 40 and 60 minutes. Distilled water was used to observed BHT and CHF performance of different nanofluids boiling time and concentration configurations. Nucleate boiling heat transfer observed to deteriorate in upward facing heater, however, in contrast effect of enhancement for downward. Maximum CHF for upward- and downward-facing heater are 2.1 and 1.9, respectively. Reduction of mean contact angle demonstrate enhancement on the critical heat flux for both upward-facing and downward-facing heater configuration. However, nucleate boiling heat transfer shows inconsistency in similar concentration with sequence of boiling time. For both downward- and upward-facing nanocoated heater’s BHT and CHF, the optimum configuration denotes by C = 400 kg/m3 with tb = 1 minute which shows the best increment of boiling curve trend with lowest wall superheat ΔT = 25 K and critical heat flux enhancement of 2.02 times.

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Kapitz, Marek, Adam Becker, and Stefan aus der Wiesche. "Influence of Wall Thermal Conductivity During Pool Boiling on Large Diamond and SiC Heaters." In ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ht2012-58047.

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The results of pool boiling experiments with synthetic (CVD) diamond and silicon carbide (SiC) heaters are presented for water as boiling liquid. The diamond and SiC heaters varied considerably in thermal conductivity, but they had smooth, nearly identical surfaces, also in regard to their contact angles for water. Temperature sensors and electric heating wires were directly vapor-deposited underneath the surfaces. The experiments were carried out with comparable large heaters (15mm × 15mm) for pure water under atmospheric pressure (1bar) in a pool boiling cell. The heat transfer characteristics including the corresponding boiling curves were obtained. In a prior work, it was found that the influence of the thermophysical wall properties might be substantial in case of special heater geometries leading to trapped bubbles, but no significant differences between both materials were observed in case of conventional heater configurations.

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Moon, Sung Bo, Seong Dae Park, Hyung Wook Park, and In Cheol Bang. "CHF Enhancement of Pool Boiling in Graphene Oxide Nanofluid With Chemical Reduction." In ASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/mnhmt2013-22051.

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Graphene oxide (GO) can be deposited on a heater surface to produce nanoscale structures that enhance the thermal limit of the heater. GO has shown a very unique feature showing CHF enhancement without wettability improvement in terms of apparent advancing contact angle unlike any other typical nanoparticles. Many studies have analyzed the reason for the enhanced critical heat flux (CHF) of the heater. Three major models have been used for studying the enhanced CHF of the heater in many heat transfer studies: wettability of surface (contact angle), Rayleigh–Taylor instability wavelength, and thermal activity. In this study, scanning electron microscopy (SEM) images and the contact angle were taken to explain the enhanced wettability of a heater surface in a GO nanofluid. GO is composed of carbon and oxygen. This material has good affinity with water because of its polarity. In an electric field, GO reduces into reduced graphene oxide (RGO). This chemical reduction on the surface may be one factor that enhances the CHF. To examine how a GO nanofluid can enhance CHF to more than twice its original magnitude, a wettability model was applied that uses the contact angle of the nichrome wire heater surface after the CHF experiment. The reason why the wettability model could not completely account for the CHF enhancement in a GO nanofluid was also determined. The reduction of GO was considered to explain CHF enhancement.

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Moharana, Manoj Kumar, Rohan M. Nemade, and Sameer Khandekar. "Phase-Change Heat Transfer of Ethanol-Water Mixtures: Towards Development of a Distributed Hydrogen Generator." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17668.

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Hydrogen fuel from renewable bio-ethanol is a potentially strong contender as an energy carrier. Its distributed production by steam reforming of ethanol on microscale platforms is an efficient upcoming method. Such systems require (a) a pre-heater for liquid to vapor conversion of ethanol water mixtures (b) a gas-phase catalytic reactor. We focus on the fundamental experimental heat transfer studies (pool and flow boiling of ethanol-water mixtures) required for the primary pre-heater boiler design. Flow boiling results (in a 256 μm square channel) clearly show the influence of mixture composition. Heat transfer coefficient remains almost constant in the single-phase region and rapidly increases as the two-phase region starts. On further increasing the wall superheat, heat transfer starts to decrease. At higher applied heat flux, the channel is subjected to axial back conduction from the single-phase vapor region to the two-phase liquid-vapor region, thus raising local wall temperatures. Simultaneously, to gain understanding of phase-change mechanisms in binary mixtures and to generate data for the modeling of flow boiling process, pool-boiling of ethanol-water mixtures has also been initiated. After benchmarking the setup against pure fluids, variation of heat transfer coefficient, bubble growth, contact angles, are compared at different operating conditions. Results show strong degradation in heat transfer in mixtures, which increases with operating temperature.

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Narabayashi, Tadashi, Yoichiro Shimazu, Toshihiko Murase, Masatoshi Nagai, Michitsugu Mori, and Shuichi Ohmori. "Development of Technologies on Innovative Simplified Nuclear Power Plant Using High-Efficiency Steam Injectors: Part 10—Application to a Small District-Heating Reactor." In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89753.

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A steam injector (SI) is a simple, compact and passive pump and also acts as a high-performance direct-contact compact heater. This provides SI with capability to use as a passive ECCS pump and also as a direct-contact feedwater heater that heats up feedwater by using extracted steam from the turbine. In order to develop a high reliability passive ECCS pump and a compact feedwater heater, it is necessary to quantify the characteristics between physical properties of the flow field. We carried out experiments to observe the internal behavior of the water jet as well as measure the velocity of steam jet using a laser Doppler velocimetry. Its performance depends on the phenomena of steam condensation onto the water jet surface and heat transfer in the water jet due to turbulence on to the phase-interface. The analysis was also conducted by using a CFD code with the separate two-phase flow models. With regard to the simplified feed-water system, size of four-stage SI system is almost the same as the model SI that had done the steam and water test that pressures were same as that of current ABWR. The authors also conducted the hot water supply system test in the snow for a district heating. With regard to the SI core cooling system, the performance tests results showed that the low-pressure SI core cooling system will decrease the PCT to almost the same as the saturation temperature of the steam pressure in a pressure vessel. As it is compact equipment, SI is expected to bring about great simplification and materials-saving effects, while its simple structure ensures high reliability of its operation, thereby greatly contributing to the simplification of the power plant for not only an ABWR power plant but also a small PWR/ BWR for district heating system.

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Zhou, Xian, Hua Liu, Lin Fu, and Shigang Zhang. "Experimental Study of Natural Gas Combustion Flue Gas Waste Heat Recovery System Based on Direct Contact Heat Transfer and Absorption Heat Pump." In ASME 2013 7th International Conference on Energy Sustainability collocated with the ASME 2013 Heat Transfer Summer Conference and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/es2013-18316.

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Condensing boiler for flue gas waste heat recovery is widely used in industries. In order to gain a portion of the sensible heat and latent heat of the vapor in the flue gas, the flue gas is cooled by return water of district heating through a condensation heat exchanger which is located at the end of flue. At low ambient air temperature, some boilers utilize the air pre-heater, which makes air be heated before entering the boiler, and also recovers part of the waste heat of flue gas. However, there are some disadvantages for these technologies. For the former one, the low temperature of the return water is required while the utilization of flue gas heat for the latter one is very limited. A new flue gas condensing heat recovery system is developed, in which direct contact heat exchanger and absorption heat pump are integrated with the gas boiler to recover condensing heat, even the temperature of the return water is so low that the latent heat of vapor in the flue gas could not be recovered directly by the general condensing technologies. Direct contact condensation occurs when vapor in the flue gas contacts and condenses on cold liquid directly. Due to the absence of a solid boundary between the phases, transport processes at the phase interface are much more efficient and quite different from condensation phenomena on a solid surface. Additionally, the surface heat exchanger tends to be more bulky and expensive. In this study, an experimental platform of the new system is built, and a variety of experimental conditions are carried out. Through the analysis of the experimental data and operational state, the total thermal efficiency of the platform will be increased 3.9%, and the system is reliable enough to be popularized.

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Oda, Kei, Hiroyasu Ohtake, and Koji Hasegawa. "Effect of Pressure on Boiling Heat Transfer Mechanism by Using MEMS Technology." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30558.

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Since boiling heat transfer has a high heat transfer coefficient, it has been used as a cooling technique for high-temperature bodies and it has been investigated for more than 70 years [1]. However, it has not yet been fully clarified: because the boiling phenomena are affected by many factors, such as the coalescence of bubbles, the fluid convection, the heat conduction and the physics on the contact of the gas, the liquid and the solid phase, boiling phenomena are considerably complicated. The present paper investigated an effect of pressure on boiling heat transfer mechanism by using the MEMS technology. And, boiling heat transfer enhancement in water under low pressure and low boiling temperature was examined experimentally. Steady state pool boiling experiments were conducted by using a copper thin-film and a silicon wafer for the test heater and pure water at atmospheric condition for the test liquid. The system pressure was 0.010, 0.10 and 0.15 MPa, respectively. The heaters were made of a printed circuit board and a commercial silicon wafer. The width was 7.5 mm, the length was 10 mm. The test sections were arranged for horizontal position facing upward. The test heaters had an artificial cylindrical-cavity of 0.010 or 0.040 mm in diameter; the cavities were fabricated by using the MEMS technology, i.e., wet etching technology and deep RIE. The test heaters were heated by Joule heating of d.c. current from a low-voltage high-current stabilizer. The heating rate of the heater was determined from supplied current and voltage. The temperature of the heater was obtained by referring to the measured electric resistance. The present experimental results showed the boiling bubble grew up to about 20 mm in diameter then the bubble released without coalesce of bubble under low pressure condition. Thus, the bubble coalesce was slight. From the experimental results, the gradient of boiling curve by using the copper thin-film was about 3: the heat transfer characteristic was dominant to nucleate boiling. On the other hand, the gradient of boiling curve by using the Silicon wafer (Non-cavity) was about unity: the heat transfer was dominant to heat convection of single-phase flow. According to the present observation of the boiling bubbles, the boiling heat transfer was dominant to latent heat: the ratio of the phase change and the convection was about 90 % and 10 %, respectively. The heat transfer ratio of the convection increased as the system pressure increased.

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Bentley, Jonathan, and Jie Cui. "Heat Transfer Modeling in a Double Wall Helical Coil Heat Exchanger." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50542.

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Double wall helical coil heat exchangers are widely used in a variety of applications. These heat exchangers are used anywhere that requires an added layer of protection from cross-fluid contamination such as in indirect water heaters. Here, the coil is heating a potable water tank with coil water which is often infused with a glycol mixture. Since contamination of the potable water would be detrimental to human health, the added protection of a double wall coil is necessary. Unfortunately, the double wall coil is inherently difficult to design due to unknown intertubular contact. This intertubular contact is hidden in nature and difficult to evaluate by nondestructive means. This paper uses STAR-CCM+ to create a computational fluid dynamic model of the double wall helical coil in respect to GAMA indirect water heater continuous draw test conditions. Using CFD, the model is validated with single wall helical coil Nusselt number correlations determined from experimentation. Then, a parametric study is performed to determine what parameters of the coil can be changed to effectively overcome the intertubular thermal loss. From this study, it is found that tube length has a linear positive relationship with coil output density and can be used to calculate necessary lengths for a desired output. Also, it was found that the experimental Nusselt number correlations identify with the results calculated by the double wall CFD model when intertubular contact percentage is used as a correction factor.

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Coursey, Johnathan S., and Jungho Kim. "Critical Heat Flux Enhancement Through Improved Surface Wettability With Surface Oxides and Nanofluids." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32045.

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Surface wetting characteristics have been shown to affect the critical heat flux (CHF) observed during boiling. Surface oxidation is known to improve the ability of the fluid to wet the surface thus enhancing CHF. Nanofluids have also shown potential to enhance CHF, but the mechanisms are poorly understood. This study is targeted towards investigating whether or not nanofluids improve CHF by altering the surface energy. The surface energy of a heater was altered by oxidizing the surface to varying degrees or depositing metal onto the surface, and was characterized by measuring the advancing three-phase contact angle. Boiling curves were determined for water and ethanol based nanofluids with aluminum oxide nanoparticle concentrations from 0.001 g/l to 0.5 g/l as well as pure fluids on surfaces of varying surface energy. A 2.7 cm2 copper heater (polished or oxidized) was used for the water-based measurements. A 1.1 cm2 thick-film heater coated with glass and/or gold was used for the ethanol-based measurements. Boiling curves obtained using these fluid/surface combinations are discussed.

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Звіти організацій з теми "Contact water heater"

Lever, James, Austin Lines, Susan Taylor, Garrett Hoch, Emily Asenath-Smith, and Devinder Sodhi. Revisiting mechanics of ice–skate friction : from experiments at a skating rink to a unified hypothesis. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/11681/42642.

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The mechanics underlying ice–skate friction remain uncertain despite over a century of study. In the 1930s, the theory of self-lubrication from frictional heat supplanted an earlier hypothesis that pressure melting governed skate friction. More recently, researchers have suggested that a layer of abraded wear particles or the presence of quasi-liquid molecular layers on the surface of ice could account for its slipperiness. Here, we assess the dominant hypotheses proposed to govern ice– skate friction and describe experiments conducted in an indoor skating rink aimed to provide observations to test these hypotheses. Our results indicate that the brittle failure of ice under rapid compression plays a strong role. Our observations did not confirm the presence of full contact water films and are more consistent with the presence of lubricating ice-rich slurries at discontinuous high-pressure zones (HPZs). The presence of ice-rich slurries supporting skates through HPZs merges pressure-melting, abrasion and lubricating films as a unified hypothesis for why skates are so slippery across broad ranges of speeds, temperatures and normal loads. We suggest tribometer experiments to overcome the difficulties of investigating these processes during actual skating trials.

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Guidati, Gianfranco, and Domenico Giardini. Joint synthesis “Geothermal Energy” of the NRP “Energy”. Swiss National Science Foundation (SNSF), February 2020. http://dx.doi.org/10.46446/publication_nrp70_nrp71.2020.4.en.

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Near-to-surface geothermal energy with heat pumps is state of the art and is already widespread in Switzerland. In the future energy system, medium-deep to deep geothermal energy (1 to 6 kilometres) will, in addition, play an important role. To the forefront is the supply of heat for buildings and industrial processes. This form of geothermal energy utilisation requires a highly permeable underground area that allows a fluid – usually water – to absorb the naturally existing rock heat and then transport it to the surface. Sedimentary rocks are usually permeable by nature, whereas for granites and gneisses permeability must be artificially induced by injecting water. The heat gained in this way increases in line with the drilling depth: at a depth of 1 kilometre, the underground temperature is approximately 40°C, while at a depth of 3 kilometres it is around 100°C. To drive a steam turbine for the production of electricity, temperatures of over 100°C are required. As this requires greater depths of 3 to 6 kilometres, the risk of seismicity induced by the drilling also increases. Underground zones are also suitable for storing heat and gases, such as hydrogen or methane, and for the definitive storage of CO2. For this purpose, such zones need to fulfil similar requirements to those applicable to heat generation. In addition, however, a dense top layer is required above the reservoir so that the gas cannot escape. The joint project “Hydropower and geo-energy” of the NRP “Energy” focused on the question of where suitable ground layers can be found in Switzerland that optimally meet the requirements for the various uses. A second research priority concerned measures to reduce seismicity induced by deep drilling and the resulting damage to buildings. Models and simulations were also developed which contribute to a better understanding of the underground processes involved in the development and use of geothermal resources. In summary, the research results show that there are good conditions in Switzerland for the use of medium-deep geothermal energy (1 to 3 kilometres) – both for the building stock and for industrial processes. There are also grounds for optimism concerning the seasonal storage of heat and gases. In contrast, the potential for the definitive storage of CO2 in relevant quantities is rather limited. With respect to electricity production using deep geothermal energy (> 3 kilometres), the extent to which there is potential to exploit the underground economically is still not absolutely certain. In this regard, industrially operated demonstration plants are urgently needed in order to boost acceptance among the population and investors.

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Lichter, Amnon, Joseph L. Smilanick, Dennis A. Margosan, and Susan Lurie. Ethanol for postharvest decay control of table grapes: application and mode of action. United States Department of Agriculture, July 2005. http://dx.doi.org/10.32747/2005.7587217.bard.

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Original objectives: Dipping of table grapes in ethanol was determined to be an effective measure to control postharvest gray mold infection caused by Botrytis cinerea. Our objectives were to study the effects of ethanol on B.cinerea and table grapes and to conduct research that will facilitate the implementation of this treatment. Background: Botrytis cinerea is known as the major pathogen of table grapes in cold storage. To date, the only commercial technology to control it relied on sulfur dioxide (SO₂) implemented by either fumigation of storage facilities or from slow release generator pads which are positioned directly over the fruits. This treatment is very effective but it has several drawbacks such as aftertaste, bleaching and hypersensitivity to humans which took it out of the GRAS list of compounds and warranted further seek for alternatives. Prior to this research ethanol was shown to control several pathogens in different commodities including table grapes and B. cinerea. Hence it seemed to be a simple and promising technology which could offer a true alternative for storage of table grapes. Further research was however required to answer some practical and theoretical questions which remained unanswered. Major conclusions, solutions, achievements: In this research project we have shown convincingly that 30% ethanol is sufficient to prevent germination of B. cinerea and kill the spores. In a comparative study it was shown that Alternaria alternata is also rather sensitive but Rhizopus stolonifer and Aspergillus niger are less sensitive to ethanol. Consequently, ethanol protected the grapes from decay but did not have a significant effect on occurrence of mycotoxigenic Aspergillus species which are present on the surface of the berry. B. cinerea responded to ethanol or heat treatments by inducing sporulation and transient expression of the heat shock protein HSP104. Similar responses were not detected in grape berries. It was also shown that application of ethanol to berries did not induce subsequent resistance and actually the berries were slightly more susceptible to infection. The heat dose required to kill the spores was determined and it was proven that a combination of heat and ethanol allowed reduction of both the ethanol and heat dose. Ethanol and heat did not reduce the amount or appearance of the wax layers which are an essential component of the external protection of the berry. The ethanol and acetaldehyde content increased after treatment and during storage but the content was much lower than the natural ethanol content in other fruits. The efficacy of ethanol applied before harvest was similar to that of the biological control agent, Metschnikowia fructicola, Finally, the performance of ethanol could be improved synergistically by packaging the bunches in modified atmosphere films which prevent the accumulation of free water. Implications, both scientific and agricultural: It was shown that the major mode of action of ethanol is mediated by its lethal effect on fungal inoculum. Because ethanol acts mainly on the cell membranes, it was possible to enhance its effect by lowering the concentration and elevating the temperature of the treatment. Another important development was the continuous protection of the treated bunches by modified atmosphere that can solve the problem of secondary or internal infection. From the practical standpoint, a variety of means were offered to enhance the effect of the treatment and to offer a viable alternative to SO2 which could be instantly adopted by the industry with a special benefit to growers of organic grapes.

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Seginer, Ido, Daniel H. Willits, Michael Raviv, and Mary M. Peet. Transpirational Cooling of Greenhouse Crops. United States Department of Agriculture, March 2000. http://dx.doi.org/10.32747/2000.7573072.bard.

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Background Transplanting vegetable seedlings to final spacing in the greenhouse is common practice. At the time of transplanting, the transpiring leaf area is a small fraction of the ground area and its cooling effect is rather limited. A preliminary modeling study suggested that if water supply from root to canopy is not limiting, a sparse crop could maintain about the same canopy temperature as a mature crop, at the expense of a considerably higher transpiration flux per leaf (and root) area. The objectives of this project were (1) to test the predictions of the model, (2) to select suitable cooling methods, and (3) to compare the drought resistance of differently prepared seedlings. Procedure Plants were grown in several configurations in high heat load environments, which were moderated by various environmental control methods. The difference between the three experimental locations was mainly in terms of scale, age of plants, and environmental control. Young potted plants were tested for a few days in small growth chambers at Technion and Newe Ya'ar. At NCSU, tomato plants of different ages and planting densities were compared over a whole growing season under conditions similar to commercial greenhouses. Results Effect of spacing: Densely spaced plants transpired less per plant and more per unit ground area than sparsely spaced plants. The canopy temperature of the densely spaced plants was lower. Air temperature was lower and humidity higher in the compartments with the densely spaced plants. The difference between species is mainly in the canopy-to-air Bowen ratio, which is positive for pepper and negative for tomato. Effect of cooling methods: Ventilation and evaporative pad cooling were found to be effective and synergitic. Air mixing turned out to be very ineffective, indicating that the canopy-to-air transfer coefficient is not the limiting factor in the ventilation process. Shading and misting, both affecting the leaf temperature directly, proved to be very effective canopy cooling methods. However, in view of their side effects, they should only be considered as emergency measures. On-line measures of stress: Chlorophyll fluorescence was shown to accurately predict photosynthesis. This is potentially useful as a rapid, non-contact way of assessing canopy heat stress. Normalized canopy temperature and transpiration rate were shown to correlate with water stress. Drought resistance of seedlings: Comparison between normal seedlings and partially defoliated ones, all subjected to prolonged drought, indicated that removing about half of the lowermost leaves prior to transplanting, may facilitate adjustment to the more stressful conditions in the greenhouse. Implications The results of this experimental study may lead to: (1) An improved model for a sparse canopy in a greenhouse. (2) A better ventilation design procedure utilizing improved estimates of the evaporation coefficient for different species and plant configurations. (3) A test for the stress resistance of transplants.

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Zevotek, Robin, Keith Stakes, and Joseph Willi. Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival: Full-Scale Experiments. UL Firefighter Safety Research Institute, January 2018. http://dx.doi.org/10.54206/102376/dnyq2164.

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As research continues into how fire department interventions affect fire dynamics in the modern fire environment, questions continue to arise on the impact and implications of interior versus exterior fire attack on both occupant survivability and firefighter safety. This knowledge gap and lack of previous research into the impact of fire streams has driven the need for further research into fire department interventions at structure fires with a focus on hose streams and suppression tactics. As the third report in the project “Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival”, this report expands upon the fire research conducted to date by analyzing how firefighting tactics, specifically suppression methods, affect the thermal exposure and survivability of both building occupants and firefighters in residential structures. • Part I: Water Distribution • Part II: Air Entrainment • Part III: Full-Scale Residential Fire Experiments. This report evaluates fire attack in residential structures through twenty-six full-scale structure fire experiments. Two fire attack methods, interior and transitional, were preformed at UL’s large fire lab in Northbrook, IL, in a single-story 1,600 ft2 ranch test structure utilizing three different ventilation configurations. To determine conditions within the test structure it was instrumented for temperature, pressure, gas velocity, heat flux, gas concentration, and moisture content. Ad- ditionally, to provide information on occupant burn injuries, five sets of instrumented pig skin were located in pre-determined locations in the structure. The results were analyzed to determine consistent themes in the data. These themes were evaluated in conjunction with a panel of fire service experts to develop 18 tactical considerations for fire ground operations. As you review the following tactical considerations it is important to utilize both these research results and your per- sonal experience to develop your department’s polices and implement these considerations during structural firefighting.

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Shomer, Ilan, Ruth E. Stark, Victor Gaba, and James D. Batteas. Understanding the hardening syndrome of potato (Solanum tuberosum L.) tuber tissue to eliminate textural defects in fresh and fresh-peeled/cut products. United States Department of Agriculture, November 2002. http://dx.doi.org/10.32747/2002.7587238.bard.

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The project sought to understand factors and mechanisms involved in the hardening of potato tubers. This syndrome inhibits heat softening due to intercellular adhesion (ICA) strengthening, compromising the marketing of industrially processed potatoes, particularly fresh peeled-cut or frozen tubers. However, ICA strengthening occurs under conditions which are inconsistent with the current ideas that relate it to Ca-pectate following pectin methyl esterase (PME) activity or to formation of rhamnogalacturonan (RG)-II-borate. First, it was necessary to induce strengthening of the middle lamellar complex (MLX) and the ICA as a stress response in some plant parenchyma. As normally this syndrome does not occur uniformly enough to study it, we devised an efficient model in which ICA-strengthening is induced consistently under simulated stress by short-chain, linear, mono-carboxylic acid molecules (OAM), at 65 oC [appendix 1 (Shomer&Kaaber, 2006)]. This rapid strengthening was insufficient for allowing the involved agents assembly to be identifiable; but it enabled us to develop an efficient in vitro system on potato tuber parenchyma slices at 25 ºC for 7 days, whereas unified stress was reliably simulated by OAMs in all the tissue cells. Such consistent ICA-strengthening in vitro was found to be induced according to the unique physicochemical features of each OAM as related to its lipophilicity (Ko/w), pKa, protonated proportion, and carbon chain length by the following parameters: OAM dissociation constant (Kdiss), adsorption affinity constant (KA), number of adsorbed OAMs required for ICA response (cooperativity factor) and the water-induced ICA (ICAwater). Notably, ICA-strengthening is accompanied by cell sap leakage, reflecting cell membrane rupture. In vitro, stress simulation by OAMs at pH<pKa facilitated the consistent assembly of ICAstrengthening agents, which we were able to characterize for the first time at the molecular level within purified insoluble cell wall of ICA-strengthened tissue. (a) With solid-state NMR, we established the chemical structure and covalent binding to cell walls of suberin-like agents associated exclusively with ICA strengthening [appendix 3 (Yu et al., 2006)]; (b) Using proteomics, 8 isoforms of cell wall-bound patatin (a soluble vacuolar 42-kDa protein) were identified exclusively in ICA-strengthened tissue; (c) With light/electron microscopy, ultrastructural characterization, histochemistry and immunolabeling, we co-localized patatin and pectin in the primary cell wall and prominently in the MLX; (d) determination of cell wall composition (pectin, neutral sugars, Ca-pectate) yielded similar results in both controls and ICA-strengthened tissue, implicating factors other than PME activity, Ca2+ or borate ions; (e) X-ray powder diffraction experiments revealed that the cellulose crystallinity in the cell wall is masked by pectin and neutral sugars (mainly galactan), whereas heat or enzymatic pectin degradation exposed the crystalline cellulose structure. Thus, we found that exclusively in ICA-strengthened tissue, heat-resistant pectin is evident in the presence of patatin and suberinlike agents, where the cellulose crystallinity was more hidden than in fresh control tissue. Conclusions: Stress response ICA-strengthening is simulated consistently by OAMs at pH< pKa, although PME and formation of Ca-pectate and RG-II-borate are inhibited. By contrast, at pH>pKa and particularly at pH 7, ICA-strengthening is mostly inhibited, although PME activity and formation of Ca-pectate or RG-II-borate are known to be facilitated. We found that upon stress, vacuolar patatin is released with cell sap leakage, allowing the patatin to associate with the pectin in both the primary cell wall and the MLX. The stress response also includes formation of covalently bound suberin-like polyesters within the insoluble cell wall. The experiments validated the hypotheses, thus led to a novel picture of the structural and molecular alterations responsible for the textural behavior of potato tuber. These findings represent a breakthrough towards understanding of the hardening syndrome, laying the groundwork for potato-handling strategies that assure textural quality of industrially processed particularly in fresh peeled cut tubers, ready-to-prepare and frozen preserved products.

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