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1
Smirnov, V. V., Yu V. Yavorovsky, V. V. Sennikov, and D. O. Romanov. "Comparative analysis of the efficiency of the application of thermal-hydraulic distributor with classical schemes of connecting subscribers." Vestnik IGEU, no. 3 (2019): 5–13. http://dx.doi.org/10.17588/2072-2672.2019.3.005-013.
Повний текст джерелаАнотація:
Analysis of the use of a thermo-hydraulic distributor in district heating schemes showed insufficient study of the mutual influence of the connected circuits, on which the coefficient of hydraulic stability of the heating network depends, and the lack of a comparative analysis of the efficiency of heat supply when using a scheme with a thermo-hydraulic distributor compared to widely used subscriber connection schemes. The purpose of the study is to compare the economic and energy efficiency of the proposed and existing subscriber connection schemes, which is an important task. In laboratory conditions, a wide range of studies have been carried out to study the hydraulic dependence of the contours of the thermo-hydraulic distributor among themselves. Processing of the results was carried out by the method of correlation-regression analysis and mathematical statistics. In a comparative analysis of subscriber connection schemes, methods of physical modeling of thermo-hydraulic modes were used. A comparative analysis showed that the energy efficiency of the scheme with a thermo-hydraulic distributor is higher in heating systems with non-automated subscribers, regardless of the temperature graph of the heating network. When comparing schemes with parallel connection of a hot water heater, it was found that the totality of electricity consumption for coolant circulation and fuel costs for a circuit with a thermo-hydraulic distributor turned out to be less irrespective of the temperature schedule. Statistical research methods confirmed the independence of the circuits and the normal supply of heat to the heating. New solutions have been obtained to increase the hydraulic stability of the centralized heat supply system using a thermo-hydraulic distributor at a heating point – the hydraulic stability coefficient of the heat network during all subscriber operation modes is equal to one. The results of the study can be used in the design of thermal points: the proposed heating system, the consumers of which will provide a stable hydraulic mode; existing heat supply system, the consumers of which must ensure the hydro-stable control of heat.
2
Ketelsen, Søren, Sebastian Michel, Torben O. Andersen, Morten Kjeld Ebbesen, Jürgen Weber, and Lasse Schmidt. "Thermo-Hydraulic Modelling and Experimental Validation of an Electro-Hydraulic Compact Drive." Energies 14, no. 9 (April 22, 2021): 2375. http://dx.doi.org/10.3390/en14092375.
Повний текст джерелаАнотація:
Electro-hydraulic compact drives (ECDs) are an emerging technology for linear actuation in a wide range of applications. Especially within the low power range of 5–10 kW, the plug-and-play capability, good energy efficiency and small space requirements of ECDs render this technology a promising alternative to replace conventional valve-controlled linear drive solutions. In this power range, ECDs generally rely on passive cooling to keep oil and system temperatures within the tolerated range. When expanding the application range to larger power classes, passive cooling may not be sufficient. Research investigating the thermal behaviour of ECDs is limited but indeed required for a successful expansion of the application range. In order to obtain valuable insights into the thermal behaviour of ECDs, thermo-hydraulic simulation is an important tool. This may enable system design engineers to simulate thermal behaviour and thus develop proper thermal designs during the early design phase, especially if such models contain few parameters that can be determined with limited information available. Our paper presents a lumped thermo-hydraulic model derived from the conservation of mass and energy. The derived model was experimentally validated based on experimental data from an ECD prototype. Results show good accuracy between measured and simulated temperatures. Even a simple thermal model containing only a few thermal resistances may be sufficient to predict steady-state and transient temperatures with reasonable accuracy. The presented model may be used for further investigations into the thermal behaviour of ECDs and thus toward proper thermal designs required to expand the application range.
3
Bhatter, Rahul Kumar, Ali Abbas, and Anant Kumar Rai. "Effect of Baffles Position on Thermo-Hydraulic Efficiency of a Solar Air Heater." IOP Conference Series: Materials Science and Engineering 1132, no. 1 (April 1, 2021): 012041. http://dx.doi.org/10.1088/1757-899x/1132/1/012041.
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4
Alam, Tabish, Md Irfanul Haque Siddiqui, Hassan Alshehri, Masood Ashraf Ali, Paolo Blecich, and Kushagra Saurabh. "Exergy-Based Thermo-Hydraulic Performance of Roughened Absorber in Solar Air Heater Duct." Applied Sciences 12, no. 3 (February 7, 2022): 1696. http://dx.doi.org/10.3390/app12031696.
Повний текст джерелаАнотація:
This paper presents the thermo-hydraulic performance of small conical ribs on the absorber plate of a solar energy air heater (SAH) using exergy analysis. Application of conical protrusion ribs on the absorber is an attractive solution for enhancing the thermal performance of a SAH. However, these ribs are also responsible for high friction losses and increased fan power consumption caused by the turbulent air flow. To optimize the rib design, it is vital to consider both thermal and hydraulic performance at the same time. The SAH was assessed using an analytic method which predicts the exergy efficiency under operating parameters (e.g., Reynolds number, solar insolation and temperature increase parameter). The following geometric quantities of ribs were evaluated for optimum exergy efficiency: the relative rib height (e/D), which was in the range between 0.200 and 0.044, and the relative rib pitch (p/e), which was in the range between 6 and 12. The combination of a relative rib height of 0.044 and relative rib pitch of 10 exhibits the highest exergy efficiency of 0.0202. The optimization of the rib geometric quantities parameters was performed by considering the temperature increase parameter, aiming to achieve maximum exergy efficiency. The combination of rib parameters e/D = 0.044 and p/e = 10 are noted to yield best performance when operating at a temperature increase parameter above 0.0141 K∙m2/W.
5
Pugi, L., R. Conti, A. Rindi, and S. Rossin. "A Thermo-Hydraulic Tool for Automatic Virtual Hazop Evaluation." Metrology and Measurement Systems 21, no. 4 (December 1, 2014): 631–48. http://dx.doi.org/10.2478/mms-2014-0055.
Повний текст джерелаАнотація:
Abstract Development of complex lubrication systems in the Oil&Gas industry has reached high levels of competitiveness in terms of requested performances and reliability. In particular, the use of HazOp (acronym of Hazard and Operability) analysis represents a decisive factor to evaluate safety and reliability of plants. The HazOp analysis is a structured and systematic examination of a planned or existing operation in order to identify and evaluate problems that may represent risks to personnel or equipment. In particular, P&ID schemes (acronym of Piping and Instrument Diagram according to regulation in force ISO 14617) are used to evaluate the design of the plant in order to increase its safety and reliability in different operating conditions. The use of a simulation tool can drastically increase speed, efficiency and reliability of the design process. In this work, a tool, called TTH lib (acronym of Transient Thermal Hydraulic Library) for the 1-D simulation of thermal hydraulic plants is presented. The proposed tool is applied to the analysis of safety relevant components of compressor and pumping units, such as lubrication circuits. Opposed to the known commercial products, TTH lib has been customized in order to ease simulation of complex interactions with digital logic components and plant controllers including their sensors and measurement systems. In particular, the proposed tool is optimized for fixed step execution and fast prototyping of Real Time code both for testing and production purposes. TTH lib can be used as a standard SimScape-Simulink library of components optimized and specifically designed in accordance with the P&ID definitions. Finally, an automatic code generation procedure has been developed, so TTH simulation models can be directly assembled from the P&ID schemes and technical documentation including detailed informations of sensor and measurement system.
6
Zhou, Aizhao, Xianwen Huang, Wei Wang, Pengming Jiang, and Xinwei Li. "Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections." Sustainability 13, no. 6 (March 16, 2021): 3255. http://dx.doi.org/10.3390/su13063255.
Повний текст джерелаАнотація:
For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.
7
Alam, Tabish, Chandan Swaroop Meena, Nagesh Babu Balam, Ashok Kumar, and Raffaello Cozzolino. "Thermo-Hydraulic Performance Characteristics and Optimization of Protrusion Rib Roughness in Solar Air Heater." Energies 14, no. 11 (May 28, 2021): 3159. http://dx.doi.org/10.3390/en14113159.
Повний текст джерелаАнотація:
To enhance the thermal performance of solar air heaters (SAHs), protrusion ribs on the absorber are considered to be an attractive solution due to their several advantages. These ribs do not cause a significant pressure drop in the SAH duct and help to enhance the heat transfer to flowing air. On the other hand, a degree of roughness of the protrusion rib on the absorber can be produced by pressing the indenting device without adding additional mass. In this paper, the thermo-hydraulic performances of different roughnesses of the conical protrusion rib on the absorber plate have been evaluated by the mutual consideration of thermal as well as hydraulic performance in term of net effective efficiency. Therefore, an analytical technique has been exploited to predict the characteristics of the net effective efficiency under various operating conditions, such as the flow Reynolds number, temperature increase parameter and insolation. The effects of the conical protrusion rib roughness—namely the relative rib pitch (p/e) and relative rib height e/D) in the ranges of 6–12 and 0.200–0.044, respectively—have been evaluated. The highest value of net effective efficiency of 70.92% was achieved at a p/e of 10 and e/D of 0.0289. The optimization of the rib parameters has been carried out in different ranges of temperature increase parameters for the highest values of net effective efficiency. A unique combination of rib parameters—a p/e of 10 and e/D of 0.044—are observed to lead to the best performance when operating a solar air heater with a temperature increase parameter of more than 0.00789 K·m2/W.
8
Singh, Niranjan Ramendra, Singh Onkar, and Janakarajan Ramkumar. "Thermo-Hydraulic Performance of Square Micro Pin Fins under Forced Convection." International Journal of Heat and Technology 39, no. 1 (February 28, 2021): 170–78. http://dx.doi.org/10.18280/ijht.390118.
Повний текст джерелаАнотація:
Thermal management of the new generation’s high performance electronic and mechanical devices is becoming important due to their miniaturization. Conventionally, the plate fin arrangement is widely used for removal of dissipated heat but, their effectiveness is not up to mark. Among different options, the most attractive and efficient alternative for overcoming this problem is micro pin fin heat sink. This paper presents the experimental investigation of square micro-pin fins heat sink for identifying the most suitable pin fin geometry for heat removal applications under forced convection. Twenty five square micro pin fin heat sinks were tested for three different heat load and Reynolds number. The results show that for large fin height lower thermal resistance was observed at the cost of large pressure drop. The dimensionless heat transfer coefficient increases with fin height and Reynolds number while it decreases with increasing fin spacing. The improvement in micro pin fin efficiency were observed by about 2 to 9% owing to presence of fins on the impingement surface, flow mixing, disruption of the boundary layers, and augmentation of turbulent transport.
9
Borek, Kinga. "Influence of liquid-nitrogen freezing of gas-bearing shale rocks on their compressive strength." Mineralogia 49, no. 1-4 (December 1, 2018): 7–16. http://dx.doi.org/10.2478/mipo-2018-0002.
Повний текст джерелаАнотація:
Abstract Any definable relation between falling temperature and the compressive strength of shale rocks should provide a useful predictive tool aiding optimization of the results of hydraulic fracturing. In this research, an automeasuring hydraulic press, a thermo-camera and the Fluent ANSYS software were used. The results of laboratory simulations, and the effects of experiments conducted on shale rocks to determine permanent changes in compressive strength, are presented. As both frozen rocks and rocks returned to room temperature show diminished compressive strength. It is suggested that prior freezing of rocks can increase the efficiency of fracturing.
10
Barreto, Germilly, Paulo Canhoto, and Manuel Collares-Pereira. "Effect of thickness on the thermo-hydraulic performance of porous volumetric solar receivers with different internal geometries." Journal of Physics: Conference Series 2116, no. 1 (November 1, 2021): 012116. http://dx.doi.org/10.1088/1742-6596/2116/1/012116.
Повний текст джерелаАнотація:
Abstract In this work, the effect of thickness on the thermal and hydrodynamic performance of porous volumetric solar receivers made of open-cell silicon carbide (SiC) ceramic foam is investigated using an in-house detailed numerical model. The model is based in a Computational Fluid Dynamics (CFD) technique to solve the volume averaged mass, momentum and energy conservation equations, including the exchange of thermal radiation inside the receiver. A Monte Carlo Ray Tracing (MCRT) method was developed and then used to model the solar radiation transport in the porous media. Two optimised internal geometries (porosity and pores size) of the receiver with adiabatic side-walls are investigated for different thicknesses. Results show that the optimal thickness depends on the porosity and pores size and there is a value from which the thermal efficiency is nearly constant and the pressure drop always increase. It was also found that the thickness should be approximately between 5 and 7 cm for porosity and pores diameter between 0.85 and 0.90 and 3.0 mm and 4.5 mm, respectively, aiming to maximise thermal efficiency by decreasing the transmission losses of solar radiation, and to keep low pressure drop.
11
kumar Goel, Abhishek, S. N. Singh, and B. N. Prasad. "Experimental investigation of thermo-hydraulic efficiency and performance characteristics of an impinging jet-finned type solar air heater." Sustainable Energy Technologies and Assessments 52 (August 2022): 102165. http://dx.doi.org/10.1016/j.seta.2022.102165.
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Boonloi, Amnart, and Withada Jedsadaratanachai. "Variations of heat transfer mechanism and flow structure in a heat exchanger tube fitted with 30° inclined ring." Advances in Mechanical Engineering 12, no. 3 (March 2020): 168781402091148. http://dx.doi.org/10.1177/1687814020911480.
Повний текст джерелаАнотація:
Flow prediction, heat transfer pattern, and thermo-hydraulic efficiency in a heat exchanger tube fitted with vortex generator are chosen for the present research. The 30° inclined ring is opted to develop the performance of the heat exchanger tube. The effects of inclined ring configuration and placement in the heat exchanger tube on the patterns of flow and heat transfer are investigated. The Reynolds number (at the entry zone of the periodic model) in the range of around 100–2000 (laminar flow region) is discussed. The heat transfer ability, pressure loss, and efficiency of the heat exchanger tube fitted with 30° inclined ring are analyzed with the numerical method (finite volume method). The SIMPLE algorithm of the commercial code is picked for the present study. The simulated results in the heat exchanger tube fitted with 30° inclined ring are offered in patterns of streamlines, temperature contour, and Nusselt number contour. From the preliminary result, it is found that the creation model of the heat exchanger tube fitted with 30° inclined ring has sufficient reliance to measure flow and heat transfer profiles. The installment of the 30° inclined ring in the heat exchanger tube leads to greater heat transfer ability and thermo-hydraulic performance because of the creation of the vortex flow and thermal boundary layer disturbance on the heat exchanger tube surface. The heat transfer ability in the heat exchanger tube fitted with 30° inclined ring is found to be around 1.00–10.56 times above the plain circular tube. In addition, the installation of the 30° inclined ring in the heat exchanger tube gives the maximum thermal enhancement factor around 3.18.
13
Birhanu, Zerihun Kinfe, Nils-Otto Kitterød, Harald E. Krogstad, and Anne Kværnø. "Numerical modeling of aquifer thermal energy efficiency under regional groundwater flow: a case study at Oslo Airport." Hydrology Research 46, no. 5 (January 28, 2015): 721–34. http://dx.doi.org/10.2166/nh.2015.119.
Повний текст джерелаАнотація:
The main purpose of this paper is to present a robust forward model for simulating extraction and storage of thermal energy in an aquifer. The model is a local three-dimensional finite element model with boundary conditions derived from an analytic large-scale model based on the regional water balance. Numerical investigations and thermo-hydraulic evaluation of a typical dipole injection/extraction system are presented. Most of the simulation results are focused on the spatio-temporal extension of the hot water plume close to the injection well where the main challenges occur with respect to numerical stability. Because the (aquifer thermal energy storage system is located close to the groundwater divide, the energy recovery is less sensitive to the well configuration with respect to the groundwater flow direction.
14
Polansky, Jiri. "Thermodynamics Cycle of Gas-Cooled Fast Reactor." Mechanics and Mechanical Engineering 22, no. 2 (August 24, 2020): 585–92. http://dx.doi.org/10.2478/mme-2018-0046.
Повний текст джерелаАнотація:
AbstractThis paper deals with the thermo-hydraulic aspect of gas cooled fast 4 generation reactor. The paper is focused on the comparison of direct and indirect strategy of thermodynamics cycle of helium cooled reactor from the thermodynamics and turbomachinary point of view. The analyses respect pressure looses at all major part of the equipment - reactor, heat exchanger, pipe lines, etc. The compressor and gas turbines efficiency are includes in calculation as well. The working fluid in primary circuit is helium. In the secondary circuit a mixture of helium and nitrogen is considered. The Cycle characteristic point and efficiency calculation reflects mixture properties of the real gas. Calculation point out the influence of mixture composition on the basic structural parameters of the turbines, compressor and heat exchangers. Thermodynamics cycle efficiency, specific heat input/output, heat flux and cycle work will be presented as characteristic parameters.
15
Boonloi, Amnart, and Withada Jedsadaratanachai. "Thermo-hydraulic performance improvement, heat transfer, and pressure loss in a channel with sinusoidal-wavy surface." Advances in Mechanical Engineering 11, no. 9 (September 2019): 168781401987257. http://dx.doi.org/10.1177/1687814019872573.
Повний текст джерелаАнотація:
Thermal efficiency development in a square channel heat exchanger attached with sinusoidal wavy surface is presented numerically. The affectation of flow attack angles ( α = 30°, 45°, and 60°), flow directions or sinusoidal wavy surface arrangements (V-apex directing downstream named “V-Downstream” and V-apex indicating upstream named “V-Upstream”), and amplitude ratios (blockage ratios = 0.10, 0.15, 0.20, and 0.25) for heat transfer and flow structure are examined for laminar flow regime ( Re = 100–1000). The physical model for the present investigation is validated with the correlation data. The current problem is resolved with the finite volume approach (semi-implicit method for pressure-linked equations algorithm). The computational information is illustrated in forms of flow topology and heat transfer mechanism in the square channel heat exchanger. The understanding of flow topology and heat transfer mechanism in the square channel heat exchanger is important knowledge to develop the heat transfer coefficient in the heat exchanger. The present of the sinusoidal wavy surface in the square channel heat exchanger can expand the heat transfer coefficient greater than the plain channel in all examples ( Nu/ Nu0 > 1). The maximal heat transfer rate is around 5.58 times above the plain square unit with the optimal performance around 1.98.
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Wang, Guiqing, Cong Qi, Maoni Liu, Chunyang Li, Yuying Yan, and Lin Liang. "Effect of corrugation pitch on thermo-hydraulic performance of nanofluids in corrugated tubes of heat exchanger system based on exergy efficiency." Energy Conversion and Management 186 (April 2019): 51–65. http://dx.doi.org/10.1016/j.enconman.2019.02.046.
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Kumar, Raj, Sushil Kumar, Rahul Nadda, Khusmeet Kumar, and Varun Goel. "Thermo-hydraulic efficiency and correlation development of an indoor designed jet impingement solar thermal collector roughened with discrete multi-arc ribs." Renewable Energy 189 (April 2022): 1259–77. http://dx.doi.org/10.1016/j.renene.2022.03.037.
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Ouabouch, Omar, Imad Ait Laasri, Mounir Kriraa, and Mohamed Lamsaadi. "Modelling and Comparison of the Thermohydraulic Performance with an Economical Evaluation for a Parabolic Trough Solar Collector Using Different Nanofluids." International Journal of Heat and Technology 39, no. 6 (December 31, 2021): 1763–69. http://dx.doi.org/10.18280/ijht.390609.
Повний текст джерелаАнотація:
This study examines the three-dimensional heat transfer and flow characteristics of nanofluids in a parabolic trough solar collector under turbulent flow conditions, whereas a non-uniform focused heat flux was applied to the absorption pipe. CuO/water, Al2O3/water, TiO2/water, and SiO2/water are studied numerically. The dynamic and thermal fields are determined by the Reynolds number varying between 50000 ≤ Re ≤ 250000, while the volume concentration of nanofluids is the following: 3% CuO, 6% Al2O3, 4.82% SiO2 and 3.15% TiO2, the nanoparticle size of 30 nm by means of Finite Element Method (FEM). Effects of various parameters such as volume fraction of nanoparticles (φ), various Reynolds numbers and type of nanoparticle on thermo-hydraulic performance of the parabolic solar collector are studied. The average Nusselt number, heat transfer coefficient, average friction factor, pressure drop, temperature and velocity distribution are illustrated using four different types of nanofluids and four different volume fractions of nanoparticles with various Reynolds numbers. According to the final results, both TiO2 and CuO nanofluids have better performance in terms of thermal and hydraulic efficiency and evaluation economic performance compared with other nanofluids studied.
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Shalaginova, Zoya I., and Vyacheslav V. Tokarev. "Development of methods for modeling dynamic thermo-hydraulic conditions for assessing the quality of functioning of heat supply systems." E3S Web of Conferences 219 (2020): 01008. http://dx.doi.org/10.1051/e3sconf/202021901008.
Повний текст джерелаАнотація:
A simulation dynamic model of thermo-hydraulic conditions of heat supply systems (HSS) is presented. The model makes it possible to analyze in time HSS operating conditions with arbitrary configuration and structure, dissimilar loads of heat consumers, taking into account the transport lag of the coolant, cooling along the length of the pipelines, under different weather conditions, disturbances in the system and a given control scenario in the control nodes. To assess the quality, indicators of the degree of heat supply to consumers are proposed. Formulas are given for determining the total, average and average expected deficit (excess) of heat, as well as heat losses in the network, for a calculated period of time under the given control rules. It is proposed to evaluate the efficiency of the operating conditions by the coefficient of efficient use of energy for the billing period. To take into account the real cost of heat, a mathematical model and a method for calculating nodal prices are presented.
20
Nagrath, Vishwas, Seyed Hunzela Haq, Harshit Mishra, and Adil Wazeer. "Theoretical Study on Methods to Increase the Efficiency and Performance of Solar Air Heater." Asian Review of Mechanical Engineering 9, no. 1 (May 5, 2020): 1–4. http://dx.doi.org/10.51983/arme-2020.9.1.2477.
Повний текст джерелаАнотація:
Due to the low thermal performance of solar air heater, different methodologies are adopted to increase its performance namely fins, artificial roughness etc. Thermal performance is obtained for different values of Reynolds number, emissivity of a plate, tilt angle and by employing different kinds of artificial roughness. There are numerous techniques which can be used on the absorber plate to increase the efficiency and Thermo-hydraulic performance of the solar air heater. We can use single roughness geometry or can combine two different roughness geometries also to get best output. By defining different correlations of heat transfer and friction factor in roughened ducts of solar air heater, we can get the best artificial roughness that can be utilized in the solar air heater. By selecting the coating material, we can improve the performance of solar air heater. As we must use our energy for future purpose, we have to store it and for that thermal energy storage materials are used. This is also one of the techniques to increase the effectiveness of solar air heater. In this article, focus has been given on study of methods of increasing the performance of solar air heater such as providing artificial roughness, increasing the collector aspect ratio etc.
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Araújo, António. "Thermo-Hydraulic Performance of Solar Air Collectors with Artificially Roughened Absorbers: A Comparative Review of Semi-Empirical Models." Energies 13, no. 14 (July 9, 2020): 3536. http://dx.doi.org/10.3390/en13143536.
Повний текст джерелаАнотація:
Due to the poor thermal characteristics of the air, the absorber roughness of solar air collectors is commonly artificially increased in order to enhance the heat transfer to the air stream. However, this is also accompanied by an undesirable increase in the pumping power due to increased friction losses. As a result, several authors have experimentally investigated several ways of maximizing the heat transfer while minimizing the friction losses of different absorbers, resulting in the development of semi-empirical functions relating the Nusselt number (a measure of heat transfer) and the friction factor (a measure of friction losses) to the Reynolds number and the roughness parameters considered for each absorber. The present paper reviews, considering the publications from the last ten years, these semi-empirical functions. Moreover, the optimum roughness parameters and operating conditions of the absorbers were estimated by finding the maximum values of two performance parameters (the thermo-hydraulic efficiency and effectiveness), calculated using the semi-empirical functions, in order to classify the absorbers in terms of their energy characteristics. This approach proves to be a rather effective way of optimizing the roughness characteristics of solar air collector absorbers. It is also concluded that, considering the range of absorbers analyzed here, generally, multiple V-shaped ribs with gaps provide the most effective roughness geometry.
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Fan, Fan, Cong Qi, Jinghua Tang, Qi Liu, Xuehui Wang, and Yuying Yan. "A novel thermal efficiency analysis on the thermo-hydraulic performance of nanofluids in an improved heat exchange system under adjustable magnetic field." Applied Thermal Engineering 179 (October 2020): 115688. http://dx.doi.org/10.1016/j.applthermaleng.2020.115688.
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Zhao, Ning, Leixin Guo, Cong Qi, Tiantian Chen, and Xin Cui. "Experimental study on thermo-hydraulic performance of nanofluids in CPU heat sink with rectangular grooves and cylindrical bugles based on exergy efficiency." Energy Conversion and Management 181 (February 2019): 235–46. http://dx.doi.org/10.1016/j.enconman.2018.11.076.
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Kumar, Raj, Erdem Cuce, Sushil Kumar, Sashank Thapa, Paras Gupta, Bhasker Goel, C. Ahamed Saleel, and Saboor Shaik. "Assessment of the Thermo-Hydraulic Efficiency of an Indoor-Designed Jet Impingement Solar Thermal Collector Roughened with Single Discrete Arc-Shaped Ribs." Sustainability 14, no. 6 (March 17, 2022): 3527. http://dx.doi.org/10.3390/su14063527.
Повний текст джерелаАнотація:
This study illustrates the impact of single discrete arc-shaped ribs (SDASR)-type artificial roughness on the performance of a jet impingement solar thermal collector (JISTC). The impact of parametric variations of SDASR on the Nusselt number (Nusdr), friction factor (fsdr), and thermohydraulic performance (ηsdr) is examined. The spacer length (Ssdr) of the SDASR was changed from 0 mm to 300 mm in stages of 100 mm during the experiment. The fixed parameters of the SDASR were a relative discrete distance Dd/Lv of 0.67, relative discrete width gw/Hr of 0.87, relative rib height Hr/H of 0.047, relative rib pitch Pr/H of 1.7, angle of an arc αsdr of 60°, jet diameter ratio Dj/Dhy of 0.065, streamwise pitch ratio X/Dhy of 1.72, and spanwise pitch ratio Y/Dhy of 0.82. The Reynolds number Re was altered from 3000 to 19,000. The Nusdr and fsdr of a JISTC with a roughened absorber plate was found to be enhanced by 5.25 and 5.98 times as compared to an STC without artificial roughness. The optimal findings of Nusdr, fsdr, and ηsdr were achieved at Ssdr = 0 mm. The maximum value of the ηsdr obtained at Ssdr = 0 mm was 2.9.
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Almurtaji, Salah, Naser Ali, Joao A. Teixeira, and Abdulmajid Addali. "On the Role of Nanofluids in Thermal-hydraulic Performance of Heat Exchangers—A Review." Nanomaterials 10, no. 4 (April 11, 2020): 734. http://dx.doi.org/10.3390/nano10040734.
Повний текст джерелаАнотація:
Heat exchangers are key components in many of the devices seen in our everyday life. They are employed in many applications such as land vehicles, power plants, marine gas turbines, oil refineries, air-conditioning, and domestic water heating. Their operating mechanism depends on providing a flow of thermal energy between two or more mediums of different temperatures. The thermo-economics considerations of such devices have set the need for developing this equipment further, which is very challenging when taking into account the complexity of the operational conditions and expansion limitation of the technology. For such reasons, this work provides a systematic review of the state-of-the-art heat exchanger technology and the progress towards using nanofluids for enhancing their thermal-hydraulic performance. Firstly, the general operational theory of heat exchangers is presented. Then, an in-depth focus on different types of heat exchangers, plate-frame and plate-fin heat exchangers, is presented. Moreover, an introduction to nanofluids developments, thermophysical properties, and their influence on the thermal-hydraulic performance of heat exchangers are also discussed. Thus, the primary purpose of this work is not only to describe the previously published literature, but also to emphasize the important role of nanofluids and how this category of advanced fluids can significantly increase the thermal efficiency of heat exchangers for possible future applications.
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Goodarzi, Marjan, Iskander Tlili, Zhe Tian, and Mohammad Reza Safaei. "Efficiency assessment of using graphene nanoplatelets-silver/water nanofluids in microchannel heat sinks with different cross-sections for electronics cooling." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 1 (June 22, 2019): 347–72. http://dx.doi.org/10.1108/hff-12-2018-0730.
Повний текст джерелаАнотація:
Purpose This study aims to model the nanofluid flow in microchannel heat sinks having the same length and hydraulic diameter but different cross-sections (circular, trapezoidal and square). Design/methodology/approach The nanofluid is graphene nanoplatelets-silver/water, and the heat transfer in laminar flow was investigated. The range of coolant Reynolds number in this investigation was 200 ≤ Re ≤ 1000, and the concentrations of nano-sheets were from 0 to 0.1 vol. %. Findings Results show that higher temperature leads to smaller Nusselt number, pressure drop and pumping power, and increasing solid nano-sheet volume fraction results in an expected increase in heat transfer. However, the influence of temperature on the friction factor is insignificant. In addition, by increasing the Reynolds number, the values of pressure drop, pumping power and Nusselt number augments, but friction factor diminishes. Research limitations/implications Data extracted from a recent experimental work were used to obtain thermo-physical properties of nanofluids. Originality/value The effects of temperature, microchannel cross-section shape, the volume concentration of nanoparticles and Reynolds number on thermal and hydraulics behavior of the nanofluid were investigated. Results are presented in terms of velocity, Nusselt number, pressure drop, friction loss and pumping power in various conditions. Validation of the model against previous papers showed satisfactory agreement.
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Karmveer, Naveen Kumar Gupta, Md Irfanul Haque Siddiqui, Dan Dobrotă, Tabish Alam, Masood Ashraf Ali, and Jamel Orfi. "The Effect of Roughness in Absorbing Materials on Solar Air Heater Performance." Materials 15, no. 9 (April 24, 2022): 3088. http://dx.doi.org/10.3390/ma15093088.
Повний текст джерелаАнотація:
Artificial roughness on the absorber of the solar air heater (SAH) is considered to be the best passive technology for performance improvement. The roughened SAHs perform better in comparison to conventional SAHs under the same operational conditions, with some penalty of higher pumping power requirements. Thermo-hydraulic performance, based on effective efficiency, is much more appropriate to design roughened SAH, as it considers both the requirement of pumping power and useful heat gain. The shape, size, and arrangement of artificial roughness are the most important factors for the performance optimization of SAHs. The parameters of artificial roughness and operating parameters, such as the Reynolds number (Re), temperature rise parameter (ΔT/I) and insolation (I) show a combined effect on the performance of SAH. In this case study, various performance parameters of SAH have been evaluated to show the effect of distinct artificial roughness, investigated previously. Therefore, thermal efficiency, thermal efficiency improvement factor (TEIF) and the effective efficiency of various roughened absorbers of SAH have been predicted. As a result, thermal and effective efficiencies strongly depend on the roughness parameter, Re and ΔT/I. Staggered, broken arc hybrid-rib roughness shows a higher value of TEIF, thermal and effective efficiencies consistently among all other distinct roughness geometries for the ascending values of ΔT/I. This roughness shows the maximum value of effective efficiency equals 74.63% at a ΔT/I = 0.01 K·m2/W. The unique combination of parameters p/e = 10, e/Dh = 0.043 and α = 60° are observed for best performance at a ΔT/I higher than 0.00789 K·m2/W.
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Karmveer, Naveen Kumar Gupta, Md Irfanul Haque Siddiqui, Dan Dobrotă, Tabish Alam, Masood Ashraf Ali, and Jamel Orfi. "The Effect of Roughness in Absorbing Materials on Solar Air Heater Performance." Materials 15, no. 9 (April 24, 2022): 3088. http://dx.doi.org/10.3390/ma15093088.
Повний текст джерелаАнотація:
Artificial roughness on the absorber of the solar air heater (SAH) is considered to be the best passive technology for performance improvement. The roughened SAHs perform better in comparison to conventional SAHs under the same operational conditions, with some penalty of higher pumping power requirements. Thermo-hydraulic performance, based on effective efficiency, is much more appropriate to design roughened SAH, as it considers both the requirement of pumping power and useful heat gain. The shape, size, and arrangement of artificial roughness are the most important factors for the performance optimization of SAHs. The parameters of artificial roughness and operating parameters, such as the Reynolds number (Re), temperature rise parameter (ΔT/I) and insolation (I) show a combined effect on the performance of SAH. In this case study, various performance parameters of SAH have been evaluated to show the effect of distinct artificial roughness, investigated previously. Therefore, thermal efficiency, thermal efficiency improvement factor (TEIF) and the effective efficiency of various roughened absorbers of SAH have been predicted. As a result, thermal and effective efficiencies strongly depend on the roughness parameter, Re and ΔT/I. Staggered, broken arc hybrid-rib roughness shows a higher value of TEIF, thermal and effective efficiencies consistently among all other distinct roughness geometries for the ascending values of ΔT/I. This roughness shows the maximum value of effective efficiency equals 74.63% at a ΔT/I = 0.01 K·m2/W. The unique combination of parameters p/e = 10, e/Dh = 0.043 and α = 60° are observed for best performance at a ΔT/I higher than 0.00789 K·m2/W.
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Muzzioli, Gabriele, Luca Montorsi, Andrea Polito, Andrea Lucchi, Alessandro Sassi, and Massimo Milani. "About the Influence of Eco-Friendly Fluids on the Performance of an External Gear Pump." Energies 14, no. 4 (February 3, 2021): 799. http://dx.doi.org/10.3390/en14040799.
Повний текст джерелаАнотація:
This paper wants to investigate the effects of eco-friendly fluids on the thermo-fluid-dynamic performance of external gear pumps in order to provide a first response to the increasingly urgent demands of the green economy. A computational fluid dynamics (CFD) approach based on the overset mesh technique was developed for the simulation of the full 3D geometry of an industrial pump, including all the characteristic leakages between components. A sensibility analysis of the numerical model with respect to different fluid properties was performed on a commonly used mineral oil, showing the key role of the fluid compressibility on the prediction of the pump volumetric efficiency. Moreover, the influence of temperature internal variations on both fluid density and viscosity were included. The BIOHYDRAN TMP 46 eco-friendly industrial oil and olive oil were further considered in this work, and the results of the simulations were compared for the three fluid configurations. A slightly lower volumetric efficiency was derived for the olive oil application against the other two conditions, but suggestive improvements were produced in terms of pressure and temperature distributions. Therefore, based on the obtained results, this paper encourages research activity towards the use of eco-friendly fluids in the hydraulic field.
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Tan, A. S. T., J. Janaun, H. J. Tham, N. J. Siambun, and A. Abdullah. "Performance enhancement of a baffle-type solar heat collector through CFD simulation study." IOP Conference Series: Materials Science and Engineering 1195, no. 1 (October 1, 2021): 012040. http://dx.doi.org/10.1088/1757-899x/1195/1/012040.
Повний текст джерелаАнотація:
Abstract The application of solar energy conversion has been extensively utilized as an alternative energy source to generate heat. This approach would be a step towards sustainable energy development particularly in the manufacturing industry with energy-intensive process. In this paper, thermal enhancement on the key component of a solar energy device – solar heat collector (SHC), has been evaluated by proposing a baffle-type SHC with various geometric configuration in the air passage namely longitudinal baffle and transversal baffle. The performance of SHC is evaluated in term of efficiency, temperature distribution, airflow pattern and pressure drop across the collector outlet through Computational Fluid Dynamic (CFD) investigation. It was observed that maximum collector efficiency was achieved in the Longitudinal-SHC (L-SHC), with a value of 46.2 % followed by Transversal-SHC (T-SHC) and without baffles. Maximum drying temperature at the collector outlet was 332.43 K for L-SHC, showing temperature rise of 0.35 % and 4.21 % from T-SHC and without baffles, respectively. The velocity vector indicated that turbulence flow was created in the T-SHC which consequently improved the heat transfer. Whereas in L-SHC, enhancement was achieved through the prolonged heating time in the passage. Considering the thermo-hydraulic performance factor evaluated, these enhancement features had diminished the effect of pressure drop.
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Sarafraz, M., Alireza Dareh Baghi, Mohammad Safaei, Arturo Leon, R. Ghomashchi, Marjan Goodarzi, and Cheng-Xian Lin. "Assessment of Iron Oxide (III)–Therminol 66 Nanofluid as a Novel Working Fluid in a Convective Radiator Heating System for Buildings." Energies 12, no. 22 (November 13, 2019): 4327. http://dx.doi.org/10.3390/en12224327.
Повний текст джерелаАнотація:
This work investigates the use of iron oxide (III)–therminol 66 oil-based nanosuspensions in a convective heating system with potential heating applications in the buildings sector. In an experimental study, characteristics of nanofluids were measured, including heat capacity, thermal conductivity, and density. The influences of mass flow rate and concentration of nanofluid on various parameters were quantified, such as pressure loss, friction coefficient, and heat transfer rate. For a concentration of 0.3 wt.%, the heat transfer increased by 46.3% and the pressure drop increased by 37.5%. The latter is due to the higher friction and viscosity of the bulk of the nanofluid. Although the pressure drop is higher, the thermo-hydraulic efficiency still increased by 19%. As a result, iron oxide (III)–therminol 66 presented reasonable thermal performance, higher heat transfer coefficient, and a lower pressure drop value (19% better performance in comparison with water) for the air–liquid convective system. Results also showed that for nanosuspensions at 0.3 wt.%, the friction factor of the system increased by 10% in comparison with the performance of the system with water.
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Qi, Cong, Maoni Liu, and Jinghua Tang. "Influence of triangle tube structure with twisted tape on the thermo-hydraulic performance of nanofluids in heat-exchange system based on thermal and exergy efficiency." Energy Conversion and Management 192 (July 2019): 243–68. http://dx.doi.org/10.1016/j.enconman.2019.04.047.
Повний текст джерела
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Kumar, Birendra, Rajen Kumar Nayak, and S. N. Singh. "Experimental Analysis of the Thermo-Hydraulic Performance on a Cylindrical Parabolic Concentrating Solar Water Heater with Twisted Tape Inserts in an Absorber Tube." Zeitschrift für Naturforschung A 73, no. 5 (May 24, 2018): 431–39. http://dx.doi.org/10.1515/zna-2018-0023.
Повний текст джерелаАнотація:
AbstractA twisted tape inserted in an absorber tube may be an excellent option to enhance the performance of a cylindrical parabolic concentrating solar collector (CPC). The present work is an experimental study of the flow and heat transfer with and without twisted tape inserts in the absorber tube of a CPC. Results are presented for mass flow rates of water, ṁ=0.0198–0.0525 kg/s, twist ratio, y=5–10 and Reynolds number, Re=2577.46–6785.55. In the present study, we found that the outlet water temperature, collector efficiency and Nusselt number (Nu) are higher in the twisted tapes as compared to those without the twisted tape inserts in the absorber tube of the CPC. For fixed mass flow rate of water ṁ, the To and η increased with the decrease in twist ratio, y, and is higher in lower twist ratio, y=5, of the twisted tapes. The whole experiment was performed at the Indian Institute of Technology (ISM) in Dhanbad, India during the months of March–April 2017. Based on the experimental data, the correlations for the Nu and friction factor were also developed.
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Boonloi, Amnart, and Withada Jedsadaratanachai. "Forced convective heat transfer and thermal efficiency assessment in square channel equipped with 10° wavy thin rib." Advances in Mechanical Engineering 12, no. 12 (December 2020): 168781402098526. http://dx.doi.org/10.1177/1687814020985267.
Повний текст джерелаАнотація:
Forced convective heat transfer and thermo-hydraulic efficiency in the heat exchanger square channel (HESC) inserted with 10° wavy thin rib (WTR) are reported numerically. The effects of rib height, pitch distance and flow velocity on flow and heat transfer profiles are considered. The rib height to the channel height; e/H or HR, is varied in the range 0.05–0.30, while the rib pitch to the channel height; P/H or PR, is varied in the range 0.50–1.25. The air velocity in the HESC inserted with the WTR is considered in terms of Reynolds number. The Reynolds numbers (Re = 100–2000) for the present investigation is analyzed at the inlet condition. The finite volume method (commercial code) with SIMPLE algorithm is picked to solve the present problem. The numerical model of the HESC inserted with the WTR is validated for both grid independence and verification of the smooth HESC. The numerical results of the HESC inserted with the WTR are printed in terms of flow and heat transfer profiles. The values of Nusselt number, friction factor and thermal efficiency factor in the HESC inserted with the WTR are also plotted. As the numerical result, it is found that the WTR in the HESC can produce the vortex flow that the reason for the enhancements of heat transfer and efficiency. The increment of the heat transfer ability in the HESC is detected when increasing rib height and Reynolds number. In addition, the greatest thermal efficiency factor in the HESC inserted with the WTR is around 3.43 at HR = 0.20, PR = 1, and Re = 2000.
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Loginov, N., A. Mikheyev, and T. Vereshchagina. "ON DEVELOPMENT OF HEAT PIPES FOR NUCLEAR POWER PLANTS." PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES: NUCLEAR AND REACTOR CONSTANTS 2021, no. 3 (September 26, 2021): 158–66. http://dx.doi.org/10.55176/2414-1038-2021-3-158-166.
Повний текст джерелаАнотація:
The article discusses the designs of two nuclear reactors cooled by heat pipes with liquid metal coolants. Both designs were developed at IPPE JSC. The first design is a research reactor with a capacity of 1.2 MW. Evaporating sodium is used as a coolant in the core. The evaporating eutectic sodium-potassium alloy is used as a coolant in the secondary loop. The third loop contains gas as working fluid of the Stirling or Brighton cycle. The report presents the results of thermo-hydraulic experiments that confirmed the main design parameters. The second design called RIFMA is an innovative super small NPP with direct conversion of thermal energy into electricity and is supposed, in particular, to be used in the Arctic region. Thermal power is 100 kW, efficiency is not less than 10 %. Molybdenum heat pipes filled with lithium are used to transfer heat from the core. To convert energy, thermophotovoltaic converters are proposed. They are cooled by low-temperature heat pipes that remove residual heat and transfer it to air radiators. A nuclear power plant concept and three versions of the core are presented.
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Jasiński, Piotr Bogusław. "Numerical Study of Heat Transfer Intensification in a Circular Tube Using a Thin, Radiation-Absorbing Insert. Part 2: Thermal Performance." Energies 14, no. 15 (July 27, 2021): 4533. http://dx.doi.org/10.3390/en14154533.
Повний текст джерелаАнотація:
This article is the second part of the work under the same title, which is based on the results of the research presented in the previous article: “Numerical study of heat transfer intensification in a circular tube using a thin, radiation-absorbing insert. Part 1: Thermo-hydraulic characteristics”. Part 1 presents an analysis of pressure drops and heat transfer intensification in a round tube with an insert, using the phenomenon of radiation absorption. In this paper, an analysis of the tested insert’s thermal performance (PEC) is presented, taking into account the criterion of equal pumping power. The tests were carried out for the range of Re = 5000–100,000 numbers, for various insert diameters (from 20% to 90% of the pipe diameter) and a constant temperature difference between the wall and the gas ∆T = 100 °C. The highest Nu numbers were observed for inserts with dimensionless diameters of 0.3 and 0.4, while the highest flow resistance was observed for inserts with diameters of 0.6 and 0.7 of the channel diameter. The thermal efficiency was calculated in two ways, as was the associated Nu number. These results significantly differed from each other: the maximum PEC values for method (I) reached 2, and for method (II) to 8. The common feature for both calculation methods was the fact that the maximum values of the Nu number and the thermal efficiency were observed for small Re numbers; however, as the Re number increases, PEC and Nu number decrease strongly.
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Maghsoudi, Peyman, Sadegh Sadeghi, Qingang Xiong, and Saiied Mostafa Aminossadati. "A multi-factor methodology for evaluation and optimization of plate-fin recuperators for micro gas turbine applications considering payback period as universal objective function." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 5 (July 19, 2019): 2411–38. http://dx.doi.org/10.1108/hff-04-2019-0333.
Повний текст джерелаАнотація:
Purpose Because of the appreciable application of heat recovery systems for the increment of overall efficiency of micro gas turbines, promising evaluation and optimization are crucial. This paper aims to propose a multi-factor theoretical methodology for analysis, optimization and comparison of potential plate-fin recuperators incorporated into micro gas turbines. Energetic, exergetic, economic and environmental factors are covered. Design/methodology/approach To demonstrate applicability and reliability of the methodology, detailed thermo-hydraulic analysis, sensitivity analysis and optimization are conducted on the recuperators with louver and offset-strip fins using a genetic algorithm. To assess the relationship between investment cost and profit for the recuperated systems, payback period (PBP), which incorporates all the factors is used as the universal objective function. To compare the performance of the recuperated and non-recuperated systems, exergy efficiency, exergy destruction and corresponding cost rate, fuel consumption and environmental damage cost rates, capital and operational cost rates and acquired profit rates are determined. Findings Based on the results, optimal PBP of the louvered-fin recuperator (147 days) is slightly lower than that with offset-strip fins (153 days). The highest profit rate is acquired by reduction of exergy destruction cost rate and corresponding decrements for louver and offset-strip fins are 2.3 and 3.9 times compared to simple cycle, respectively. Originality/value This mathematical study, for the first time, focuses on introducing a reliable methodology, which covers energetic, exergetic, economic and environmental points of view beneficial for design and selection of efficient plate-fin recuperators for micro gas turbine applications.
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P, Jayesh, Mukkamala Y, and Bibin John. "Design and testing of energy-efficient heat exchangers for Newtonian and non-Newtonian fluids – A review." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 236, no. 3 (October 4, 2021): 575–606. http://dx.doi.org/10.1177/09576509211047000.
Повний текст джерелаАнотація:
Heat transfer enhancement, pumping power and weight minimization in enhanced heat exchangers has long been achieved by deploying tubes with internal surface modifications like microgrooves, ribs, fins, knurls, and dimples with and without tube inserts. This article presents a very extensive review of experimental and computational studies on heat transfer enhancement, which covers convectional and unconventional working fluids under different fluid flow conditions. Compound augmentation with tube surface modifications and inserts has yielded enhancements in the overall heat transfer coefficient of over 116% in the fully developed turbulent flow regime. Exotic fluids like nano-coolants deployed in spiral grooved mircofin tubes yielded 196% enhancement in tube side heat transfer rate for concentrations as low as 0.5% by volume, while the thermal efficiency index measuring the overall enhancement in relation to the pumping power was 75%. However, reviews that address the combined effect of unconventional fluids, surface modifications and tube inserts on the overall thermo-hydraulic performance of annular heat exchangers seem to be limited. Further, nano-coolants aren’t frequently used in the process industry. The goal of this study is to document and evaluate the impact of cost-effective and energy-saving passive enhancement techniques such as tube surface modifications, tube inserts, and annular enhancement techniques on annular heat exchangers used in the process industries with Newtonian and non-Newtonian fluids. This review should be useful to engineers, academics and medical professionals working with non-Newtonian fluids and enhanced heat exchangers.
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P, Jayesh, Mukkamala Y, and Bibin John. "Design and testing of energy-efficient heat exchangers for Newtonian and non-Newtonian fluids – A review." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 236, no. 3 (October 4, 2021): 575–606. http://dx.doi.org/10.1177/09576509211047000.
Повний текст джерелаАнотація:
Heat transfer enhancement, pumping power and weight minimization in enhanced heat exchangers has long been achieved by deploying tubes with internal surface modifications like microgrooves, ribs, fins, knurls, and dimples with and without tube inserts. This article presents a very extensive review of experimental and computational studies on heat transfer enhancement, which covers convectional and unconventional working fluids under different fluid flow conditions. Compound augmentation with tube surface modifications and inserts has yielded enhancements in the overall heat transfer coefficient of over 116% in the fully developed turbulent flow regime. Exotic fluids like nano-coolants deployed in spiral grooved mircofin tubes yielded 196% enhancement in tube side heat transfer rate for concentrations as low as 0.5% by volume, while the thermal efficiency index measuring the overall enhancement in relation to the pumping power was 75%. However, reviews that address the combined effect of unconventional fluids, surface modifications and tube inserts on the overall thermo-hydraulic performance of annular heat exchangers seem to be limited. Further, nano-coolants aren’t frequently used in the process industry. The goal of this study is to document and evaluate the impact of cost-effective and energy-saving passive enhancement techniques such as tube surface modifications, tube inserts, and annular enhancement techniques on annular heat exchangers used in the process industries with Newtonian and non-Newtonian fluids. This review should be useful to engineers, academics and medical professionals working with non-Newtonian fluids and enhanced heat exchangers.
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Elistratova, Y., A. Seminenko, V. Minko, and R. Ramazanov. "FEATURES OF LIQUID FLOW DISTRIBUTION IN PLATE HEAT EXCHANGERS REFERENCES." Bulletin of Belgorod State Technological University named after. V. G. Shukhov 5, no. 12 (January 8, 2021): 47–55. http://dx.doi.org/10.34031/2071-7318-2020-5-12-47-55.
Повний текст джерелаАнотація:
The relevance of the work of information and diagnostic systems in the field of monitoring of plate heat exchange equipment is considered. The reliability of the monitoring devices requires an accurate mathematical description of the thermo hydrodynamic processes in the heat exchange channels. The classical description of these processes implies a uniform distribution of the flow rate of the working medium along the length of the plate package, which in turn implies equal conditions for the formation of salt deposition products on the heating surfaces of the plate heat exchanger. The use of dependencies that take into account the equality of costs for a package of plates reduces the reliability of diagnostics of the efficiency of hot water devices of the plate type. Since the geometric space formed by the plates is represented by parallel channels connected by sections of transit collectors, the method of resistance characteristics is proposed as a method of hydraulic calculation of the distribution features of liquid flows through heat exchange channels. The dependence of the design features of the location of the interplate channels relative to the input of the coolant into the distribution manifold is revealed. It is found that, the flow rate of the circulating coolant is less in the channels most remote from the inlet pipe than in the nearest channels. The hypothesis of the influence of the relative position of the channels in relation to the inlet pipe is confirmed by numerical studies of the hydrodynamic regime of the plate heat exchanger.
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Deponte, H., W. Augustin, and S. Scholl. "Development of a quantification method for fouling deposits using phosphorescence." Heat and Mass Transfer 57, no. 10 (March 26, 2021): 1661–70. http://dx.doi.org/10.1007/s00231-021-03053-6.
Повний текст джерелаАнотація:
AbstractParticulate fouling on structured surfaces is typically quantified using the integral thermal or mass-based fouling resistance. The observed geometries may be structures that can improve the heat transfer in heat exchangers (e.g., dimples), cavities in components, or more complex geometries. However, due to limited accessibility or the requirement for a locally resolved measurement, the existing quantification methods may not be applicable to structured surfaces. For this reason, a new method is needed for the quantification for fouling deposits. In this study, dimpled surfaces were evaluated by measuring the integral thermal and mass-based fouling resistance and comparing it with the local fouling resistance inside and around the dimple. This comparison was carried out online with the Phosphorescent Fouling Quantification method developed for this purpose, using phosphorescent particles to quantify the deposited mass. The mass-based fouling resistance can be calculated using computer-aided image analysis. The measurements for the evaluation were conducted on dimpled surfaces, which produced a characteristic fouling pattern. With the new method a reduced surface coverage from up to 33.3 % was observed, which led to lower fouling resistances downstream of the dimple compared to a plain surface. These results confirm earlier numerical and experimental findings, suggesting an advantage of dimpled surfaces over other surface structures with respect to thermo-hydraulic efficiency as well as reduced fouling. Thus, the Phosphorescent Fouling Quantification method provides the possibility of calculating values for local fouling resistances on structured surfaces, as well as the possibility of optimizing surface structures to minimize fouling propensity.
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Hermes, Christian J. L., Joel Boeng, Diogo L. da Silva, Fernando T. Knabben, and Andrew D. Sommers. "Evaporator Frosting in Refrigerating Appliances: Fundamentals and Applications." Energies 14, no. 18 (September 21, 2021): 5991. http://dx.doi.org/10.3390/en14185991.
Повний текст джерелаАнотація:
Modern refrigerators are equipped with fan-supplied evaporators often tailor-made to mitigate the impacts of frost accretion, not only in terms of frost blocking, which depletes the cooling capacity and therefore the refrigerator coefficient of performance (COP), but also to allow optimal defrosting, thereby avoiding the undesired consequences of condensate retention and additional thermal loads. Evaporator design for frosting conditions can be done either empirically through trial-and-error approaches or using simulation models suitable to predict the distribution of the frost mass along the finned coil. Albeit the former is mandatory for robustness verification prior to product approval, it has been advocated that the latter speeds up the design process and reduces the costs of the engineering undertaking. Therefore, this article is aimed at summarizing the required foundations for the design of efficient evaporators and defrosting systems with minimized performance impacts due to frosting. The thermodynamics, and the heat and mass transfer principles involved in the frost nucleation, growth, and densification phenomena are presented. The thermophysical properties of frost, such as density and thermal conductivity, are discussed, and their relationship with refrigeration operating conditions are established. A first-principles model is presented to predict the growth of the frost layer on the evaporator surface as a function of geometric and operating conditions. The relation between the microscopic properties of frost and their macroscopic effects on the evaporator thermo-hydraulic performance is established and confirmed with experimental evidence. Furthermore, different defrost strategies are compared, and the concept of optimal defrost is formulated. Finally, the results are used to analyze the efficiency of the defrost operation based on the net cooling capacity of the refrigeration system for different duty cycles and evaporator geometries.
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Chennu, Ranganayakulu. "Numerical analysis of compact plate-fin heat exchangers for aerospace applications." International Journal of Numerical Methods for Heat & Fluid Flow 28, no. 2 (February 5, 2018): 395–412. http://dx.doi.org/10.1108/hff-08-2016-0313.
Повний текст джерелаАнотація:
Purpose The purpose of this study is to find the thermo-hydraulic performances of compact heat exchangers (CHE’s), which are strongly depending upon the prediction of performance of various types of heat transfer surfaces such as offset strip fins, wavy fins, rectangular fins, triangular fins, triangular and rectangular perforated fins in terms of Colburn “j” and Fanning friction “f” factors. Design/methodology/approach Numerical methods play a major role for analysis of compact plate-fin heat exchangers, which are cost-effective and fast. This paper presents the on-going research and work carried out earlier for single-phase steady-state heat transfer and pressure drop analysis on CHE passages and fins. An analysis of a cross-flow plate-fin compact heat exchanger, accounting for the individual effects of two-dimensional longitudinal heat conduction through the exchanger wall, inlet fluid flow maldistribution and inlet temperature non-uniformity are carried out using a Finite Element Method (FEM). Findings The performance deterioration of high-efficiency cross-flow plate-fin compact heat exchangers have been reviewed with the combined effects of wall longitudinal heat conduction and inlet fluid flow/temperature non-uniformity using a dedicated FEM analysis. It is found that the performance deterioration is quite significant in some typical applications due to the effects of wall longitudinal heat conduction and inlet fluid flow non-uniformity on cross-flow plate-fin heat exchangers. A Computational Fluid Dynamics (CFD) program FLUENT has been used to predict the design data in terms of “j” and “f” factors for plate-fin heat exchanger fins. The suitable design data are generated using CFD analysis covering the laminar, transition and turbulent flow regimes for various types of fins. Originality/value The correlations for the friction factor “f” and Colburn factor “j” have been found to be good. The correlations can be used by the heat exchanger designers and can reduce the number of tests and modification of the prototype to a minimum for similar applications and types of fins.
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Shang, Lizhi, and Monika Ivantysynova. "Scaling Criteria for Axial Piston Machines Based on Thermo-Elastohydrodynamic Effects in the Tribological Interfaces." Energies 11, no. 11 (November 19, 2018): 3210. http://dx.doi.org/10.3390/en11113210.
Повний текст джерелаАнотація:
In lieu of reliable scaling rules, hydraulic pump and motor manufacturers pay a high monetary and temporal price for attempting to expand their production lines by scaling their existing units to other sizes. The challenge is that the lubricating interfaces, which are the key elements in determining the performance of a positive displacement machine, are not easily scalable. This article includes an analysis of the size-dependence of these units with regard to the significant physical phenomena describing the behavior of their three most critical lubricating interfaces. These phenomena include the non-isothermal elastohydrodynamic effects in the fluid domain, and the heat transfer and thermal elastic deflection in the solid domain. The performance change due to size variation is found to be unavoidable and explained through fundamental physics. The results are demonstrated using a numerical fluid–structure–thermal interaction model over a wide range of unit sizes. Based on the findings, a guide to scaling swashplate-type axial piston machines such as to uphold their efficiency is proposed.
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Guevara Morel, Carlos, Jobst Maßmann, and Jan Thiedau. "Numerical Analysis of the integrity of potential host rocks – modelling thermo-hydro-mechanical processes in the containment providing rock zone." Safety of Nuclear Waste Disposal 1 (November 10, 2021): 173–74. http://dx.doi.org/10.5194/sand-1-173-2021.
Повний текст джерелаАнотація:
Abstract. The disposal of heat-generating nuclear waste in deep geological formations is an internationally accepted concept. Several repository systems are under discussion in Germany, whereby claystone, salt or crystalline rock could act as the host rock. In this contribution we focus on repository systems where the Containment Providing Rock Zone (CRZ) ensures safe enclosure of the waste and thus the geologic barrier is essential. Even though the various rock types considered differ substantially in their mechanical, hydraulic, thermal and chemical behavior, they must all meet the same safety requirements as defined by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) in 2020. As part of these safety requirements, it must be shown that the integrity of the CRZ is guaranteed for the verification period, i.e. the retention of the properties essential for the containment capacities must be demonstrated over 1 million years. Therefore, the formation of new pathways must be avoided and temperature development must not significantly impair the barrier effect. The anticipated stresses and fluid pressures should not exceed the dilatancy strength and the fluid pressure capacity, respectively. In order to assess the compliance of these requirements, numerical modelling is an essential and powerful tool. Even though great progress has been made regarding the efficiency of computational methods, multiphysical modelling on different length scales over long time periods is still a challenging task. Moreover, since readily available solutions do not exist, adapted methods have to be developed and evaluated, in order to verify concepts and numerical implementations. The BGR gained experience in the field of thermal, hydraulic, mechanical (THM) numerical analysis of the integrity of the CRZ in salt rock and clay stone joined research projects on German disposal options. For crystalline rocks, first concepts are currently being developed within the CHRISTA II project. Compared to clay stone and salt rock, special features have to be taken into account: First of all, crystalline rock is characterized by fractures and other discontinuities. Thus, it cannot be assumed that an undisturbed area of sufficient size can be found for the entire nuclear waste. Consequently, several smaller CRZs must be defined, each providing undisturbed rock. Numerical analysis must deal with smaller CRZs and mechanical and hydraulic boundary conditions that are influenced by fractures. In addition, the processes in the individual CRZs may influence each other (e.g. Temperature distribution). Preliminary modelling approaches and results of numerical THM analyses, considering an upscaled fracture network, are presented.
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Pavese, Valeria, Dean Millar, and Vittorio Verda. "Mechanical Efficiency of Hydraulic Air Compressors." Journal of Energy Resources Technology 138, no. 6 (June 27, 2016). http://dx.doi.org/10.1115/1.4033623.
Повний текст джерелаАнотація:
After air and water mixing, the process of gas compression in the downcomer shaft or pipe of a hydraulic air compressor is considered nearly isothermal due to (i) the mass flow rate of water being typically of three orders higher than that of the gas it compresses, (ii) water having a heat capacity approximately four times that of air, and (iii) the intimate contact and large heat transfer area between the gas phase and the liquid phase of the bubbly flow. A formulation for estimation of the efficiency of a closed- or open-loop hydraulic air compressor, expressed in terms of the principal hydraulic air compressor design variables, is presented. The influence of a hitherto underappreciated factor affecting the performance of these installations, such as the solubility of the gas being compressed in the water, is explored. A procedure for estimating the yield of compressed gas, accounting for these solubility losses, is explained and used to determine the mechanical efficiency of historical hydraulic air compressor installations from reported performance data. The result is a significant downward revision of hydraulic air compressor efficiency by approximately 20% points in comparison to most reported efficiencies. However, through manipulation of cosolute concentrations in the water, and the temperature of the water (through regulation of the ejection of compression heat), the mechanical efficiency can be increased to the formerly reported levels. The thermo-economic implication of these efficiency determinations is that in a modern context, hydraulic air compressors may be able to outperform conventional mechanical gas compression equipment.
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Egorov, Kirill, and Larisa Stepanova. "Research of Thermo-Hydraulic Pin-Type Radiator Efficiency for Electronic Device Cooling." Science and Education of the Bauman MSTU 15, no. 11 (December 3, 2014). http://dx.doi.org/10.7463/1115.0817314.
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Arunachala, U. C. "Experimental Study With Analytical Validation of Energy Parameters in Parabolic Trough Collector With Twisted Tape Insert." Journal of Solar Energy Engineering 142, no. 3 (January 21, 2020). http://dx.doi.org/10.1115/1.4045825.
Повний текст джерелаАнотація:
Abstract Thermo-hydraulic performance evaluation of parabolic trough collector is important while introducing heat transfer augmentation techniques to it. In the present outdoor experimental study, the role of twisted tape is justified in laminar flow-based parabolic trough collector. For the Re range of 544–1742 and solar beam radiation of 400–750 W/m2, the use of twisted tape (twist ratios: 5.2, 4.1, and 2.7) resulted in maximum instantaneous efficiency of 22.3%, 29.5%, and 40%, respectively, against 19.1% with plain receiver. The effect of pressure drop rise on system performance due to twisted tape is found to be insignificant as effective thermo-hydraulic efficiency recorded are 21.8%, 29.3%, and 39.7%, respectively, with maximum uncertainty involved of 1.01%. In view of the importance of system performance evaluation over a wide range of operating parameters and limitation of outdoor experiments, an analytical model has been developed which followed the similar trend. The model takes into account various operating conditions, viz. laminar, twisted tape-based laminar and turbulent flow condition as well as air-in-annulus and evacuated receiver cases. Using the model (laminar region) in both plain and twisted tape cases, the maximum percentage deviation in the prediction of exit fluid temperature (in °C) and effective thermo-hydraulic efficiency are 1.6 and 13.3, respectively. Further, for a turbulent case, the maximum percentage deviation in exit temperature (in °C) noticed is 2.9. Hence, the developed analytical model is having a good agreement with the experimental outcomes.
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Kannan, C., M. Mohanraj, and P. Sathyabalan. "Experimental investigations on jet impingement solar air collectors using pin-fin absorber." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering, July 8, 2020, 095440892093530. http://dx.doi.org/10.1177/0954408920935301.
Повний текст джерелаАнотація:
In this paper, the performances of a novel jet impingement solar air collector (JISAC) using flat and pin-fin absorbers were experimentally investigated. The experimental observations in a JISAC have been made under the climatic conditions of Coimbatore city in India during the year 2019. The thermo-hydraulic analyses were conduced to study the influence of pressure drop across the perforated jet plate. The effects of solar irradiation, ambient temperature, ambient wind velocity and air mass flow rate through the JISAC duct using flat and pin-fin absorbers were studied. The air mass flow rate through the JISAC was optimized to 0.025 kg/s based on the experimental trials. Thermodynamic performance comparisons have been made among the flat and pin-fin absorbers. The results showed that, the JISAC using pin-fin absorber has 2–7°C higher air temperature at the outlet with 3–7%, 2–6% and 2–6% improved energy efficiency, thermo-hydraulic efficiency and exergy efficiency, respectively when compared to the JISAC using flat absorber. The pressure drop across the JISAC duct is about 90% higher when compared to the conventional solar air collectors. The pressure drop through the jet plate has increased the air velocity impinging on the absorber. As a result, the heat transfer coefficient between air and the absorber has been significantly improved.
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Madhukeshwara, Nanjundappa, A. Alhadhrami, Hassan A. H. Alzahrani, and B. H. Prasanna. "Thermal–hydraulic analysis of a solar air heater fitted with a wire-roughened absorber plate." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering, December 9, 2021, 095440892110590. http://dx.doi.org/10.1177/09544089211059044.
Повний текст джерелаАнотація:
This study is to evaluate heat transmission and friction in a rectangular solar air heater with a V-shaped wire rib roughness on the absorber plate that operates in fully formed turbulent flow. Additionally, studies are performed to generate prediction equations for the average friction factor, Stanton number, and efficiency index. The Reynolds number [Formula: see text]–[Formula: see text], angle of attack [Formula: see text]20[Formula: see text]–90[Formula: see text]), relative roughness pitch [Formula: see text]–[Formula: see text], relative roughness height [Formula: see text]–[Formula: see text], and the aspect ratio [Formula: see text]–[Formula: see text] was varied. The efficiency index [Formula: see text] is commonly employed as a thermo-hydraulic performance metric. It is computed as [Formula: see text]. The wire roughness and airflow parameters [Formula: see text] are optimized to maximize heat transfer while retaining minimal friction losses. On the basis of resemblance criteria, average Stanton numbers, average Nusselt numbers, and even average friction factors are derived. The results are compared to those obtained with a smooth absorber duct under similar airflow circumstances in order to assess the increase in heat transfer coefficient and friction factor. The [Formula: see text], and [Formula: see text] have a significant influence on thermo–hydraulic performance, according to these studies. With [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text], the optimal configuration geometry for wire roughness and solar air heater duct is identified.