Academic literature on the topic 'Refrigerant circulation'
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Journal articles on the topic "Refrigerant circulation"
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Hamad, Ahmed J. "Experimental Investigation of Vapor Compression Refrigeration System Performance Using Nano-Refrigerant." Wasit Journal of Engineering Sciences 2, no. 2 (October 2, 2014): 12–27. http://dx.doi.org/10.31185/ejuow.vol2.iss2.26.
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Experimental investigation of vapor compression refrigeration system performance using Nano-refrigerant is presented in this work. Nano-refrigerant was prepared in current work by mixing 50 nanometers diameter of copper oxide CuO nanoparticles with Polyolester lubrication oil and added to the compressor of the refrigeration system to be mixed with pure refrigerant R-134a during its circulation through refrigeration system. Three concentrations (0.1%, 0.25%, and 0.4%) of CuO-R134 a Nano-refrigerant are used to study the performance of the refrigeration system test rig and to investigate the effect of using Nano-refrigerant as a working fluid compared with pure refrigerant R-134a. The results showed that, the increasing in concentration of CuO nanoparticles in the Nano-refrigerant will significantly enhance the performance of the refrigeration system, as adding nanoparticles will increase the thermal conductivity, heat transfer and improve the thermo-physical properties of Nano-refrigerant. Investigation of performance parameters for refrigeration system using Nano-refrigerant with 0.4% concentration compared with that for pure refrigerant R-134a shows that, Nano-refrigerant has reflect higher performance in range of 10% and 1.5% increase in COP and refrigeration effect respectively and 7% reduction in power consumption for refrigeration system. It can be concluded that, Nano-refrigerants can be efficiently and economically feasible to be used in the vapor compression refrigeration systems.
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OKAMOTO, Yoshiyuki, Masahiko SUZUKI, Kiyoshi KAWAGUCHI, and Kouji KISHITA. "Boiling Refrigerant Type Panel Cooler. Refrigerant Circulation and Cooling Performance." Transactions of the Japan Society of Mechanical Engineers Series B 66, no. 645 (2000): 1447–52. http://dx.doi.org/10.1299/kikaib.66.1447.
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Okamoto, Yoshiyuki, Masahiko Suzuki, Kiyoshi Kawaguchi, and Kouji Kishita. "Boiling refrigerant-type panel cooler (refrigerant circulation and cooling performance)." Heat Transfer?Asian Research 33, no. 2 (2004): 94–105. http://dx.doi.org/10.1002/htj.20003.
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Jiang, Wei Jiang. "The Study of Heat-Engines Based on Refrigerant Phase-Change Circulation." Applied Mechanics and Materials 66-68 (July 2011): 649–53. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.649.
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This paper firstly introduces the principles of Stirling heat engines based on refrigerant phase-change circulation. This heat engines use two external heat reservoire. When the refrigerant in an engine cylinder absorbs heat from high-temperature heat sources, refrigerant is transformed from liquid to gas and the volume of the refrigerant expands to drive the piston apply work. When the refrigerant releases heat to low-temperature sources, the volume of the refrigerant shrinks. Therefore, phase change thermal engine technology using solar energy, industrial waste heat and heat produced by combustion of any fuel to work, no gas emissions, high thermal efficiency and environmental advantages. Thermal phase transition and thus the engine technology will be in the field of energy and power of a cutting-edge technology, great development potential and prospects.
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Chen, J., and H. Kruse. "Calculating Circulation Concentration of Zeotropic Refrigerant Mixtures." HVAC&R Research 1, no. 3 (July 1, 1995): 219–31. http://dx.doi.org/10.1080/10789669.1995.10391320.
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Xie, Y., S. Nagai, T. Okamura, and N. Hirano. "Refrigerant circulation system for cooling a HTS coil." Journal of Physics: Conference Series 1559 (June 2020): 012094. http://dx.doi.org/10.1088/1742-6596/1559/1/012094.
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Sologubenko, O., J. Hemrle, and L. Kaufmann. "Passive system of cooling and refrigerant fluid circulation, assisted by capillary pumping." Journal of Physics: Conference Series 2116, no. 1 (November 1, 2021): 012092. http://dx.doi.org/10.1088/1742-6596/2116/1/012092.
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Abstract We propose a concept design of a cooling system, primarily targeting gas-insulated switchgear enclosures which use a mixture of a refrigerant fluid, such as Novec™ 649, and a non-condensable gas for electrical insulation. The novel open-loop system relies on evaporative cooling assisted by capillary pumping, and refrigerant vapor condensation on the walls of the system enclosure. The results of experiments on a laboratory prototype are presented and discussed. Besides cooling, a major benefit of the system is in facilitating the circulation of the gas mixture in the enclosure.
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Tsoy, Alexandr, Alexandr Granovskiy, Diana Tsoy, and Dmitriy Koretskiy. "Cooling capacity of experimental system with natural refrigerant circulation and condenser radiative cooling." Eastern-European Journal of Enterprise Technologies 2, no. 8 (116) (April 30, 2022): 45–53. http://dx.doi.org/10.15587/1729-4061.2022.253651.
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The surface of the Earth is a source of radiation of thermal energy, which, passing through the atmosphere, is partially absorbed while the bulk of the energy is released into the surrounding outer space. A cooling technique based on this physical phenomenon is known as radiative cooling (RC). It is possible to reduce the consumption of electricity for cooling, as well as to reduce capital costs, by integrating the unit with radiative cooling directly into the circulation circuit of the refrigerant of the refrigeration machine. An experimental refrigeration system has been designed, in which in the cold periods of the year the removal of heat from the cooled object is carried out due to the mode of natural circulation of the refrigerant from the evaporator to the heat exchanger, cooled by radiative cooling. A refrigeration system with natural circulation and radiative cooling of the refrigerant R134a was experimentally studied during the autumn period in Almaty. The experimental study established that the chamber is cooled with the help of the examined system while the temperature in the cooled volume is maintained by 5...7 K above ambient air temperature at night. The dependence of the air temperature in the refrigerating chamber on the temperature of the atmospheric air has been determined. A procedure for assessing the cooling capacity of the system has been devised. The study reported here demonstrated the possibility of using radiative cooling to remove heat under the mode of natural circulation of the refrigerant. The refrigeration system reduces energy consumption in the cold seasons by diverting heat to the environment without the compressor operating
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Lee, Seok-Ju, Hae-Jin Sung, Minwon Park, DuYean Won, Jaeun Yoo, and Hyung Suk Yang. "Analysis of the Temperature Characteristics of Three-Phase Coaxial Superconducting Power Cable according to a Liquid Nitrogen Circulation Method for Real-Grid Application in Korea." Energies 12, no. 9 (May 8, 2019): 1740. http://dx.doi.org/10.3390/en12091740.
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Large-capacity superconducting power cables are in the spotlight to replace existing underground transmission power cables for energy power transmission. Among them, the three-phase coaxial superconducting power cable has the economic advantage of reducing the superconducting shielding layer by enabling magnetic shielding when the three phases are homogeneous without an independent superconducting shielding layer for magnetic shielding. In order to develop the three-phase coaxial superconducting power cable, the electrical and structural design should be carried out to construct the superconducting layer. However, the thermal design and analysis for the cooling of the three-phase coaxial superconducting power cable must be done first, so that the electrical design can be made using the temperature transferred to the superconducting layer. The three-phase coaxial superconducting cable requires a cooling system to circulate the cryogenic refrigerant for cooling below a certain temperature, and the structure of the cable through which the cryogenic refrigerant travels must also be analyzed. In this paper, the authors conducted a longitudinal temperature analysis according to the structure of the refrigerant circulation system of the cable and proposed a refrigerant circulation system suitable for this development. The temperature profile according to this analysis was then used as a function of temperature for the electrical (superconducting and insulating layers) design of the three-phase coaxial superconducting power cable. It is also expected to be used to analyze the cooling structure of the three-phase coaxial superconducting power cable installed in the real grid system.
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Sun, Liying, and Liang Liu. "Establishment and solution of the RNC flow network model." International Journal of Modeling, Simulation, and Scientific Computing 05, no. 04 (September 29, 2014): 1471001. http://dx.doi.org/10.1142/s1793962314710019.
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Refrigerant natural circulation (RNC) system is a closed loop recycling system which is composed of evaporator, condenser, gas pipe and the liquid pipe. The difference in indoor and outdoor temperatures will lead to the refrigerant phase-change, and the gravity difference caused by different heights of condenser and evaporator will make the low boiling point refrigerants carry on natural circulation to realize the indoor heating or cooling. In order to analyze the effect of changes in the RNC system upon the working conditions of the indoor and outdoor units as well as the function of the indoor unit, this paper describes the incidence relations among the various components of the RNC system, and establishes gas–liquid two-phase fluid network mathematical model by using the method of fluid network; besides utilizing the model, it also conducts simulator investigation of coupling characteristics of the RNC system's refrigeration condition, and makes an analysis of indoor temperature, indoor unit's air volume, the number of indoor units and the indoor unit capacity and other factors' changes on the coupling characteristics of the RNC system. The results show that under refrigeration conditions, the increase in the air volume of a single indoor unit or room temperature will result in an increase in the cooling capacity of its own indoor units, a decrease in the cooling capacity of other indoor units and a reduction in the total cooling capacity of indoor units of the RNC system; however, the decrease in the outdoor units' inlet temperature will lead to a drop in the evaporation temperature of the system and increase in the cooling capacity.
Dissertations / Theses on the topic "Refrigerant circulation"
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Maprelian, Eduardo. "Experimentos de perda de refrigerante total e parcial no reator IEA-R1." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/85/85133/tde-05072018-162522/.
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A segurança de instalações nucleares é uma preocupação mundial que tem crescido, sobretudo, após o acidente nuclear de Fukushima. O estudo de acidentes em reatores nucleares de pesquisa tal como o Acidente de Perda de Refrigerante (APR), considerado por muitas vezes um acidente base de projeto, é importante para garantir a integridade da instalação. O APR pode levar ao descobrimento parcial ou total do núcleo do reator e, como condição de segurança, deve-se garantir que haja a remoção do calor de decaimento dos elementos combustíveis. Esse trabalho teve o objetivo de realizar experimentos de descobrimento parcial e total no Elemento Combustível Instrumentado (ECI), construído no Instituto de Pesquisas Energética e Nucleares (IPEN), a fim de estudar os possíveis APRs em reatores de pesquisa. Uma seção de testes, denominada STAR, foi projetada e construída para simular os APRs. O ECI foi irradiado no núcleo do reator IEA-R1 (IPEN) e inserido na STAR, que ficou totalmente imersa na piscina do reator. No ECI, foram instalados termopares para medição das temperaturas do revestimento e do fluido em várias posições axiais e radiais. Foram realizados experimentos para cinco níveis de descobrimento do ECI, um total e quatro parciais, em duas condições distintas de calor de decaimento. Na análise dos resultados, verificou-se que os casos de descobrimento total foram os mais críticos, ou seja, as temperaturas do revestimento foram as maiores quando comparadas com os casos de descobrimentos parciais. Adicionalmente, foi realizada a simulação numérica de dois experimentos com o código RELAP5, cujos resultados demonstraram ótima concordância com os dos níveis experimentais, e temperaturas maiores que as experimentais. As máximas temperaturas do revestimento alcançadas em todos os experimentos ficaram bem abaixo da temperatura de empolamento do combustível, que é de 500°C. Assim, a STAR provou ser um aparato experimental seguro e confiável para a realização de experimentos de perda de refrigerante.The safety of nuclear facilities has been a growing global concern mainly after the Fukushima nuclear accident. Studies on nuclear research reactor accidents such as the Loss of Coolant Accident (LOCA), considered many times a design basis accident, are important for guaranteeing the integrity of the plant. A LOCA may lead to the partial or complete uncovering of the fuel assemblies and assured decay heat removal is a safety condition. This work aimed to perform partial and complete uncovering experiments in the Instrumented Fuel Assembly (IFA) designed at the Instituto de Pesquisas Energéticas e Nucleares (IPEN) in order to study possible LOCAs in research reactors. A test section for experimental simulation of Loss of Coolant Accident named STAR was designed and built. The IFA was irradiated in the IEA-R1 and installed in the STAR, which was totally immersed in the reactor pool. Thermocouples were installed in the IFA to measure the clad and fluid temperatures in several axial and radial positions. The experiments were carried out for five levels of uncovering of IFA, being one complete uncovering and four partial uncovering, in two different conditions of decay heat. In the results analysis was observed that the cases of complete uncovering of the IFA were the most critical ones, that is, those cases presented higher clad temperatures when compared with partial uncovering cases. Additionally, a numerical simulation of two experiments was carried out by using the RELAP 5 code. The numerical results showed an optimum agreement with the experimental levels results and greater than the experimental temperatures. The maximum clad temperatures reached in all experiments were quite below the fuel blister temperature, which is 500 °C. Therefore, the STAR has proven to be a safe and reliable experimental apparatus for conducting loss of coolant experiments.
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Radchenko, Mykola, Eugeniy Trushliakov, Andrii Radchenko, М. І. Радченко, Є. І. Трушляков, and А. М. Радченко. "Enhancing heat efficiency of air coolers of air conditioning systems by injector refrigerant circulation." Thesis, 2020. http://eir.nuos.edu.ua/xmlui/handle/123456789/4340.
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Radchenko, M. Enhancing heat efficiency of air coolers of air conditioning systems by injector refrigerant circulation = Підвищення теплової ефективності повітроохолоджувачів систем кондиціонування інжектором / M. Radchenko, E. Trushliakov, A. Radchenko // Матеріали XI міжнар. наук.-техн. конф. "Інновації в суднобудуванні та океанотехніці". В 2 т. – Миколаїв : НУК, 2020. – Т. 1. – С. 581–491.Анотація: Один з найпривабливіших резервів підвищення ефективності систем кондиціонування та їх застосування в різних областях полягає в ефективній роботі повітряних охолоджувачів (випарників холодоагенту). Концепція доопрацювання ефективної роботи випарників холодоагенту з неповним випаровуванням холодоагенту за рахунок рециркуляції рідкого холодоагенту інжектором (реактивним насосом) знайшла новий імпульс для подальших застосувань у зовнішніх повітряних переробних установках, щоб відповідати різним нагріванням зовнішнього тепла відповідно до фактичних кліматичних умов Умови в приміщенні відповідали різним тепловим навантаженням у приміщеннях в системах кондиціювання без змінного холодильного потоку. Запропонована концепція підвищення теплової ефективності теплообмінників з киплячими холодоагентами всередині каналів розроблена для вирішення проблеми нерівномірного розподілу холодоагенту у впускних колекторах (головках) для мікроканальних теплообмінників або між котушками холодоагенту та нерівними зовнішнім боковим нагріванням повітря на змійовиках холодоагенту шляхом переповнення їх за допомогою рециркуляції рідкого холодоагенту, що забезпечує виключення кінцевої стадії висихання випаровування холодоагенту з низькою інтенсивністю передачі тепла. Таким чином, за рахунок виключення внутрішньої проблеми нерівномірного розподілу холодоагенту та низької інтенсивності передачі тепла випаровуванням холодоагенту в каналах загальна проблема підвищення ефективності теплообмінників киплячим холодоагентом всередині каналів перетворюється на зовнішню проблему передачі тепла на повітряній стороні.
Abstract: One of the most attractive reserves of enhancing the efficiency of air conditioning (AC) systems and their application in various fields consists in efficient operation of air coolers (refrigerant evaporators). A retrofit concept of efficient operation of refrigerant evaporators with incomplete refrigerant evaporation due to liquid refrigerant recirculation by injector (jet pump) has found a new impulse for further applications in outdoor air processing units (OAPU) to match varying outdoor heat loads according to actual climatic conditions and for indoor air coils to match varying indoor heat loads in ductless Variable Refrigerant Flow (VRF) AC systems. A proposed concept of enhancing heat efficiency of heat exchangers with boiling refrigerants inside channels is intended to solve the problem of uneven refrigerant distribution in inlet manifolds (headers) for microchannel heat exchangers or between refrigerant coils and of uneven outside air heat loads on refrigerant coils by over filling them through liquid refrigerant injector recirculation that provides excluding the final dry-out stage of refrigerant evaporation with low intensity of heat transfer. Thus, due to excluding the internal problem of refrigerant uneven distribution and low intensity of heat transfer of refrigerant evaporation in channels the general problem of enhancing the efficiency of heat exchangers with boiling refrigerants inside channels is transformed into the external problem of heat transfer on air side.
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Katzeff, Steven. "An investigation into the efficiency of systems for circulating refrigerant through evaporators in the ice-making plant at the ERPM Gold Mine." Thesis, 2012. http://hdl.handle.net/10539/11185.
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Although comparisons of relative energy efficiency and cost effectiveness for
small gas and mechanically pumped liquid overfeed refrigeration systems
(arrangements) have been performed, no such comparison has been reported for
large batch type ice-making systems. The ice-making plant at the Far East Vertical
Shaft, East Rand Proprietary Mines (ERPM) Ltd, South Africa, which produced
ice in a batch-type process for cooling its underground workings, utilizes cold
flash gas to pump liquid refrigerant to and through its ice-building evaporators.
Each of this plant’s three operating units manufactured up to 1000 tons of ice per
day to adequately cool this gold mine’s underground workings. For one unit of
this plant, this investigation models the functioning of the existing ‘cold gas’
pumping arrangement, supported by test data. It then investigates, through similar
modelling, a more conventional ‘hot gas’ pumping arrangement, and two possible
mechanically pumped arrangements for this unit, functioning under similar
conditions. The models provide a thermodynamically meaningful comparison of
the different liquid overfeed refrigerant pumping arrangements, principally in
terms of their energy efficiency and electrical cost effectiveness. They predict that
under similar operating conditions, the current cold gas pumping arrangement is
more energy efficient and electrically cost effective than both hot gas and
conventionally mechanically pumped arrangements. This agrees with the
suggestions and conclusions of previous investigations performed on smaller
refrigeration systems. However, compared to a theoretical fully mechanically
pumped arrangement, the existing cold gas pumped system is predicted to incur
larger unproductive refrigeration demand and higher annual electrical operating
cost.
Books on the topic "Refrigerant circulation"
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American Society of Heating, Refrigerating and Air-Conditioning Engineers. Method of testing forced circulation air cooling and air heating coils. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 2000.
Find full textConference papers on the topic "Refrigerant circulation"
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Field, Brandon S., and Pega Hrnjak. "Visualization of Two-Phase Refrigerant and Refrigerant-Oil Flow in a Microchannel." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43471.
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Visualizations of adiabatic two-phase refrigerant flow in a glass channel of diameter 0.5 mm have been made for three refrigerants: R134a, Propane (R290), and Ammonia (R717), representing a wide span of fluid properties, which covers most of the refrigerants commercially in use. In these visualizations four flow regimes were observed: bubble-slug, slug, slug-annular, and annular. These flow regimes were compared to various flow maps, including some developed for small channels. Flow visualizations were also made with mixtures of R134a and 68-weight POE oil at oil circulation rates of approximately 0.5, 1.5 and 3 percent. This is of interest when considering refrigeration systems, which have a small percentage of oil in circulation that travels through system and through the heat exchangers. When the refrigerant is in a liquid state, this presents little variation in fluid properties, because the concentration is so small. However, when the refrigerant is partly vapor, the oil concentration in the remaining liquid can have significant effect on the fluid properties. In addition, the saturation temperature and pressure of the oil-refrigerant mixture changes with concentration, where a single-phase vapor is never observed in flows of oil-refrigerant mixtures, even at temperatures exceeding the saturation temperature of the pure mixture. This effect is known as “apparent superheat”.
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Sun, Li-ying, and Zui-liang Ma. "Study on the Refrigerant Natural Circulation System Performance in Calefaction Condition." In 2010 International Conference on E-Product E-Service and E-Entertainment (ICEEE 2010). IEEE, 2010. http://dx.doi.org/10.1109/iceee.2010.5661194.
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Wujek, Scott S., Predrag S. Hrnjak, and Christopher J. Seeton. "Online Measurement Techniques for Determining Oil Circulation Rate." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37640.
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Refrigeration and air-conditioning (AC) systems employ refrigerant as the working fluid; however, a portion of oil is discharged from the compressor as part of the compression process and also circulates through the system. This small amount of parasitic fluid causes heat transfer and pressure drop correlations that were developed for pure refrigerant flow to fail and needs to be determined for proper design of heat exchange equipment and connection piping. It is desired to be able to measure the small concentrations of oil circulating as a component of the working fluid online in real time. The oil in circulation as a fraction of the total fluid flow rate is termed the oil circulation rate or oil circulation ratio (OCR). The goal of this study was to determine which combination of fluid property measurements could be used to accurately and precisely quantify OCR. Oil, which is needed to lubricate the compressor, is carried with the refrigerant throughout the system. Oil affects fluid properties such as enthalpy, thermal conductivity, and viscosity and can impact the ability to accurately measure heat exchanger and system performance. Fluid property and flow maps have been developed for various refrigerant-oil mixtures; in combination with these maps the ability to accurately measure OCR online may prove to be a powerful tool in quickly measuring, analyzing, and improving system performance. Without this ability to accurately measure the oil circulation rate over the range of operating conditions, it is impossible to create accurate thermodynamic balances based entirely on the properties of the refrigerant portion of the working fluid. The refrigerant-lubricant mixture selected for this study is a commonly used mixture for automotive AC systems: R134a with ND-8 oil. In a typical air conditioner, utilizing R134a with ND-8, a single phase exists only in subcooled portions of the condenser and the liquid line. Therefore, the experiments were conducted at typical automotive AC conditions between 20 °C and 45 °C, pressures ranging from the saturation pressure up to 1900 kPa, and an OCR between 0% and 12%, and a fixed mass flux of nominally 300 kg/m2s. For a single phase fluid comprised of two components, it is necessary to measure three independent fluid properties to completely describe its state. Since the temperature and pressure are easily obtainable, additional readily available properties to determine the liquid composition were selected: density, ultra-violet light absorptivity, and refractive index. The accuracy and precision of calculating the OCR with these measurements are compared analytically and experimentally. The experimental apparatus was located within an environmental chamber which was capable of controlling the temperature over the range of test conditions. The working fluid was circulated using an oil free gear pump and the pressure of the mixture was controlled via a hydraulic cylinder which was attached to a variable pressure source. Precise quantities of oil were incorporated into the working fluid with a high pressure liquid chromatography pump. A length of clear nylon tubing permitted flow visualization.
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Middleton, Bobby D., Patrick V. Brady, and Serafina Lawles. "The Sandia National Laboratories Natural Circulation Cooler." In ASME 2021 Power Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/power2021-65399.
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Abstract Sandia National Laboratories (SNL) is developing a cooling technology concept — the Sandia National Laboratories Natural Circulation Cooler (SNLNCC) — that has potential to greatly improve the economic viability of hybrid cooling for power plants. The SNLNCC is a patented technology that holds promise for improved dry heat rejection capabilities when compared to currently available technologies. The cooler itself is a dry heat rejection device, but is conceptualized here as a heat exchanger used in conjunction with a wet cooling tower, creating a hybrid cooling system for a thermoelectric power plant. The SNLNCC seeks to improve on currently available technologies by replacing the two-phase refrigerant currently used with either a supercritical fluid — such as supercritical CO2 (sCO2) — or a zeotropic mixture of refrigerants. In both cases, the heat being rejected by the water to the SNLNCC would be transferred over a range of temperatures, instead of at a single temperature as it is in a thermosyphon. This has the potential to improve the economics of dry heat rejection performance in three ways: decreasing the minimum temperature to which the water can be cooled, increasing the temperature to which air can be heated, and increasing the fraction of the year during which dry cooling is economically viable. This paper describes the experimental basis and the current state of the SNLNCC.
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Toyama, Toshiyuki, Takashi Uekawa, Susumu Hiodoshi, and Shigeki Hagiwara. "A Theoretical and Experimental Procedure for Designing of Oil Circulation Ratio Reduction." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42957.
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This report demonstrates the successful development of a design method reducing oil circulation ratio (hereafter OCR) in swing compressors, based on calculations from a simplified model and an actual experiment. The developed OCR analysis tool features the addition of oil circulation flow rate circuit to the oil supply circuit that diagnoses the pump, the oil feeding passage, and the bearings by electrical circuit. The oil circulation flow rate is affected by refrigerant flow. In consideration of the complementary effects of refrigerant gas and oil circulation flow rate, including wall impingement of oil droplets, the gravity of oil droplets, and buoyancy, calculations can be conducted as separation efficiency ratio. In the experiment, the behavior of oil droplets in refrigerant in a compressor outfitted with pressure-proof glass was observed with a high-speed camera. It was thereby ascertained that the predicted speed of oil droplets and the actual speed in the compressor were almost the same. The effects of a drop in oil level during operation due to the oil circulation flow rate can be taken into account, something previously impossible with conventional circuits. The conclusive analytical precision of OCR is a range of 30–115Hz with a margin of error of ±0.3wt%. Using this method, design points that have substantial impact on OCR reduction can be clarified. With structural changes to the motor-rotor as suggested from the analysis, OCR can be reduced. Consequently, a significant reduction in the period necessary for compressor development has been achieved.
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Ibrahim, Talaat A. "Experimental Assessment and Thermal Performance of an Ammonia-Water Absorption Heat Pump." In ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90486.
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In this paper, an experimental assessment and thermal performance of a prototype ammonia-water absorption heat pump are carried out. The experimentations are conducted for different operating conditions such as: filling up concentration (40 and 47%), inlet brine temperature (-5, +5 and +15 °C) and inlet cooling water temperature (20 [25], 30 and 40 °C). The effects of performance parameters like refrigerant vapor concentration leaving rectifier, mass fraction spread and specific solution circulation ratio are also investigated. The results are divided into two categories. The first one is an external analysis of the absorption system considering thermal loads and system performance. However, the second one represents the internal analysis of the heat pump taking into account the temperature glide and degree of subcooling. Little effect is found for the filling up concentration on the thermal loads for different heat pump components as well as the heating capacity and the coefficient of performance. The refrigerant vapor concentration of the refrigerant vapor should not be less than 0.999 to avoid the effect of temperature glides on the system performance. Temperatures of the cooling water, brine and generator all have large effects on the system performance as any sorption system. Inaccurate expansion valve control leads to lower heating COP. Controlling the mass fraction spread or the specific circulation ratio affects considerably thermal loads of different absorption system components. The control of these two parameters can be accomplished by controlling the solution pump and flow rates in the solution loops.
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Mackenzie, Pat T., Paul A. Lebbin, Steven J. Eckels, and Mohammad H. Hosni. "The Effects of Oil in Circulation on the Performance of an Automotive Air Conditioning System." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56778.
Full textAbstract:
An automotive air conditioning system was subjected to varying percentages of oil in circulation (OIC) to investigate its impact on the evaporator, the condenser, and cycle performance. Since automotive air conditioning systems do not typically use oil separators, the compressor lubricant circulates through the system and effects evaporator, condenser and cycle performance. The OIC of the system was controlled by means of an oil separator installed in a parallel line at the compressor outlet allowing variable amounts of refrigerant to pass through the separator. The separated oil was returned upstream of the compressor inlet. It was found that the amount of OIC had an impact on the air conditioning system’s performance. The information presented allows the designer to judge the performance merits of installing an oil separator in an actual automotive air conditioning system of the type that was being simulated. The test system was built on a workbench to facilitate installation of various sensors to measure temperatures, pressures, relative humidity, flow rates, and power consumption. The workbench was placed across two environmental chambers such that the environmental conditions at the evaporator and condenser could be independently controlled. A test matrix of varying refrigerant flow rates, air flow rates, environmental conditions, and OIC were designed to simulate a range of car speed conditions that would be encountered in practice. An analysis was performed on the data collected from the workbench and the equations used in that analysis are presented in the paper. Although the results show some increase in heat transfer performance and cycle efficiency the overall improvements were moderate.
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Elatar, Ahmed, Kashif Nawaz, Bo Shen, Van Baxter, and Omar Abdelaziz. "Characterization of Wrapped Coil Tank Water Heater During Charging/Discharging." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71818.
Full textAbstract:
Heat pump water heaters (HPWH) are an energy efficient method for water heating compared to conventional electric water heaters. A wrapped coil around the water tank is often used as the condenser for the heat pump for such applications. Thermal stratification, caused by varying heat transfer rate from the condenser to the water depending on the phase of the refrigerant and the wrap configuration, is often observed inside the tank, especially for HPWHs using CO2 as the refrigerant. The current study investigates the impact of the charging/discharging process on thermal stratification. A series of simulations were conducted based on the draw patterns recommended by the DOE method of test for rating water heater performance. We also analyzed the water circulation patterns during charging/discharging process. The thermal stratification was adversely affected because of the circulation even when the Heat Pump (HP) was operational. It was observed that a relatively higher charge/discharge flow rate disrupts the thermal stratification quickly and thus lowers the supply water temperature. Furthermore, the duration of charging/discharging also plays an important role. It was noticed that the back flow has insignificant effect on the supply water temperature if charging/discharging time is relatively small. However, the effect was obvious for larger water draw flow rates that last for longer time.
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Cho, Honggi, and Keumnam Cho. "Mocrochannel Evaporators of the Residential Air-Conditioner." In ASME 2007 5th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2007. http://dx.doi.org/10.1115/icnmm2007-30032.
Full textAbstract:
The objective of present work was to evaluate the performance of microchannel evaporators of the residential air-conditioner using R-22. Six prototype evaporators were manufactured and tested with psychrometric calorimeter test facilities. The test was conducted in two different ways. Each evaporator consisted of two parallel flow type heat exchangers connected with several return pipes. The heat exchanger had 41 microchannel tubes that had 8 rectangular ports with the hydraulic diameter of 1.3 mm. For the vapor compression system (VCS), the flow area ratio and the number of return pipe had a great effect on the cooling capacity. Type 3 with the flow area ratio of 73/ 58% showed best cooling capacity. The effect of the number of circuit and merging manifold on the cooling capacity was relatively small. For the refrigerant circulation system (RCS), the cooling capacity of the test evaporators was a little bit changed as the mass flow rate and inlet quality increased. The effect of mass flow rate on the cooling capacity was slightly superior to that of inlet quality. The effect of the number of circuit on the cooling capacity was different with the result of the VCS, while the effect of merging manifold was negligible. The cooling capacity proportionally increased as the vertical inclination angle of the evaporator increased due to gravity force.
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Amalfi, Raffaele L., Todd Salamon, Filippo Cataldo, Jackson B. Marcinichen, and John R. Thome. "Ultra-Compact Micro-Scale Heat Exchanger for Advanced Thermal Management in Datacenters." In ASME 2020 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ipack2020-2542.
Full textAbstract:
Abstract The present study is focused on the experimental characterization of two-phase heat transfer performance and pressure drops within an ultra-compact heat exchanger (UCHE) suitable for electronics cooling applications. In this specific work, the UCHE prototype is anticipated to be a critical component for realizing a new passive two-phase cooling technology for high-power server racks, as it is more compact and lighter weight than conventional heat exchangers. This technology makes use of a novel combination of thermosyphon loops, at the server-level and rack-level, to passively cool an entire rack. In the proposed two-phase cooling technology, a smaller form factor UCHE is used to transfer heat from the server-level thermosyphon cooling loop to the rack-level thermosyphon cooling loop, while a larger form factor UCHE is used to reject the total heat from the server rack into the facility-level cooling loop. The UCHE is composed of a double-side-copper finned plate enclosed in a stainless steel enclosure. The geometry of the fins and channels on both sides are optimized to enhance the heat transfer performance and flow stability, while minimizing the pressure drops. These features make the UCHE the ideal component for thermosyphon cooling systems, where low pressure drops are required to achieve high passive flow circulation rates and thus achieve high critical heat flux values. The UCHE’s thermal-hydraulic performance is first evaluated in a pump-driven system at the Laboratory of Heat and Mass Transfer (LTCM-EPFL), where experiments include many configurations and operating conditions. Then, the UCHE is installed and tested as the condenser of a thermosyphon loop that rejects heat to a pumped refrigerant system at Nokia Bell Labs, in which both sides operate with refrigerants in phase change (condensation-to-boiling). Experimental results demonstrate high thermal performance with a maximum heat dissipation density of 5455 (kW/m3/K), which is significantly larger than conventional air-cooled heat exchangers and liquid-cooled small pressing depth brazed plate heat exchangers. Finally, a thermal performance analysis is presented that provides guidelines in terms of heat density dissipations at the server- and rack-level when using passive two-phase cooling.