Experimental Investigation of a Miniature Ejector Using Water as Working Fluid

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Jingming Dong ◽  
Qiuyu Hu ◽  
Yuxin Xia ◽  
He Song ◽  
Hongbin Ma ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Working Conditions ◽  
Thermal Energy ◽  
Nozzle Exit ◽  
Cooling System ◽  
Area Ratio ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Condensing Pressure

Abstract This paper presents an experimental investigation of a miniature ejector using water as the working fluid. The investigated ejector cooling system can utilize the thermal energy to be removed to power the cooling system and maintain the temperature of an electronic component below ambient temperature. The effects of working conditions, nozzle exit position (NXP), and area ratio on the coefficient of performance (COP) of ejector performance were investigated. Experimental results show that the miniature ejector can function well when the temperature in the high-temperature evaporator (HTE) ranges from 55 °C to 70 °C and can achieve a COP (coefficient of performance) of 0.66. With an increase of the NXP, the COP decreases, while the critical condensing pressure first increases and then decreases. As the area ratio of the miniature ejector increases, the COP increases, and the critical condensing pressure decreases.

Experimental Investigation of a Miniature Ejector Using Water As Working Fluid

2019 ◽  
Author(s):  
Jingming Dong ◽  
Yuxin Xia ◽  
Hongbin Ma ◽  
He Song ◽  
Zhongxi Zhao ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Ambient Temperature ◽  
Working Conditions ◽  
Nozzle Exit ◽  
Cooling System ◽  
Area Ratio ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Condensing Pressure

Abstract This paper presents an experimental investigation of a miniature ejector using water as the working fluid. The investigated ejector cooling system can be used to keep the temperature of an electric chip below ambient temperature. The authors tested the effects of working conditions, the nozzle exit position (NXP), and the area ratio on the ejector’s performance. Experimental results show that the miniature ejector works well in the high-temperature evaporator (HTE) under temperatures ranging from 55 °C to 70 °C and can achieve a 0.66 coefficient of performance (COP). With the increase of the NXP, the COP decreased, while the critical condensing pressure first increased and then decreased. As the area ratio of the miniature ejector increased, the COP increased, and the critical condensing pressure decreased.

scholarly journals Hybrid thermoelectric ejector - refrigeration system

2017 ◽  
Author(s):  
◽  
Baffoe Obeng
Keyword(s):  
Mathematical Model ◽  
High Temperature ◽  
Theoretical Prediction ◽  
Nozzle Exit ◽  
Cooling System ◽  
Experimental Results ◽  
Working Fluid ◽  
Thermoelectric Cooler ◽  
Refrigeration System ◽  
Waste Energy

A mathematical model is developed to predict the refrigeration performance of an ejector powered by waste energy from a thermoelectric cooler. The model is based on constant pressure mixing process and considers the effect of frictional loss, viscous effect and shock wave phenomenon. Using this model, effects of nozzle exit position, temperatures of low and high temperature evaporators, area ratios, and working fluid on the system performance can be predicted. The components of the ejector were fabricated and an experiment was set up using water as working fluid. At steady state, effects such as operational conditions, nozzle exit position and critical condensing pressure on performance of the system were studied. The experimental results were compared with investigations conducted by other researchers and also with theoretical prediction. Based on the experimental results and theoretical prediction, the performance of a miniature thermoelectric ejector cooler can be determined. While a pump is needed for a conventional ejector cooling system, the investigated system is to utilize the capillary force generated by thermal energy to produce the pumping capability to pump the working fluid from the condenser to both low-temperature evaporator and high-temperature evaporator. A mathematical model is developed to predict the capillary flow and ensure the circulation through the entire system from the condenser, through the lowtemperature evaporator to the high-temperature evaporator. The model can consider the effects of wick structure, vapor pressure, liquid pressure, temperature and flow rate. Using this model, the hybrid ejector system is designed and fabricated. The experimental system to test the prototype is developed and an experiment is conducted subsequently. Using the waste energy generated from the hot side of the thermoelectric cooler, the coefficient of performance (COP) of the hybrid system, i.e., thermoelectric cooler integrated with ejector refrigeration system, can be highly increased. The investigation will result in highly efficient cooling system for electronic cooling.

scholarly journals Experimental investigation of the thermal and mechanical stability of rocks for high-temperature thermal-energy storage

2017 ◽  
Vol 203 ◽  
pp. 373-389 ◽  
Author(s):  
Viola Becattini ◽  
Thomas Motmans ◽  
Alba Zappone ◽  
Claudio Madonna ◽  
Andreas Haselbacher ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Mechanical Stability

ARCTIC: A Rotary Compressor Thermally Insulated µCooler

2005 ◽  
Author(s):  
Joshua D. Heppner ◽  
David C. Walther ◽  
Albert P. Pisano
Keyword(s):  
Hot Spots ◽  
Cooling System ◽  
Heat Removal ◽  
Coefficient Of Performance ◽  
The Arctic ◽  
Working Fluid ◽  
Rotary Compressor ◽  
Speed Increase ◽  
Rotary Engine ◽  
Compressor Design

Microscale cooling to date relies largely on passive on-chip cooling in order to move heat from hot spots to alternate sites. Such passive cooling devices include capillary pump loops (CPL), heat pipes, and thermosiphons. Recent developments for active cooling systems include thermal electric coolers (TECs) for heat removal. This paper focuses on the design of an active microscale closed loop cooling system that uses a Rankine vapor compression cycle cooling system. In this design, a rotary compressor will generate the high pressure required for efficient cooling and will circulate the working fluid to move heat away from chip level hot spots to the ambient. The rotary compressor will leverage technology gained from the Rotary Engine Power System (REPS) program at the UC Berkeley, most specifically the 367 mm3 displacement platform. The advantage of a Wankel (Maillard) compressor is that it provides six compression strokes per revolution rather than a single compression stroke common to other popular compressors such as the rolling piston. The current Wankel compressor design will achieve a theoretical compression ratio of 8:1. The ARCTIC (A Rotary Compressor Thermally Insulated μCooler) system will be a microscale hybrid system consisting of some microfabricated (or MEMS) components including microchannels, in plane MEMS valves, and potentially MEMS temperature, pressure and flow sensors integrated with mesoscale, traditionally machined steel components, including the compressor itself. The system is designed to remove between 25-35 W of heat at 1000 rpm using R-134a but the system is easily scaleable through a speed increase or decrease of the compressor. Further, the current compressor design has a theoretical coefficient of performance (C.O.P.) of approximately 2, a significant improvement over comparable TECs with C.O.P.s of approximately .05-.1. Finally, a thermal circuit analysis determines that the time constant to achieve refrigeration temperature in 12 seconds is possible.

Improvement of Heat Transfer Performance of Loop Heat Pipe for Electronic Devices

2011 ◽  
Author(s):  
Tomonao Takamatsu ◽  
Katsumi Hisano ◽  
Hideo Iwasaki
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Thermal Energy ◽  
Heat Load ◽  
Cooling System ◽  
Electronic Devices ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Reserve Area ◽  
Heat Transport Capability

In this paper is presented the results on performance of the cooling model using Loop Heat Pipe (LHP) system. In recent years, ever-ending demand of high performance CPU led to a rapid increase in the amount of heat dissipation. Consequently, thermal designing of electronic devices need to consider some suitable approach to achieve high cooling performance in limited space. Heat Pipe concept is expected to serve as an effective cooling system for laptop PC, however, it suffered from some problems as follows. The heat transport capability of conventional Heat Pipe decreases with the reduction in its diameter or increase in its length. Therefore, in order to use it as cooling system for future electronic devices, the above-mentioned limitations need to be removed. Because of the operating principle, the LHP system is capable of transferring larger amount of heat than conventional heat pipes. However, most of the LHP systems suffered from some problems like the necessity of installing check valves and reservoirs to avoid occurrence of counter flow. Therefore, we developed a simple LHP system to install it on electronic devices. Under the present experimental condition (the working fluid was water), by keeping the inside diameter of liquid and vapor line equal to 2mm, and the distance between evaporator and condenser equal to 200mm, it was possible to transport more than 85W of thermal energy. The thickness of evaporator was about 5mm although it included a structure to serve the purpose of controlling vapor flow direction inside it. Successful operation of this system at inclined position and its restart capability are confirmed experimentally. In order to make the internal water location visible, the present LHP system is reconstructed using transparent material. In addition, to estimate the limit of heat transport capability of the present LHP system using this thin evaporator, the air cooling system is replaced by liquid cooling one for condensing device. Then this transparent LHP system could transport more than 100W of thermal energy. However, the growth of bubbles in the reserve area with the increase in heat load observed experimentally led to an understanding that in order to achieve stable operation of the LHP system under high heat load condition, it is very much essential to keep enough water in the reserve area and avoid blocking the inlet with bubbles formation.

Thermoelectric Air-Conditioning System: Building Applications and Enhancement Techniques

2019 ◽  
Vol 27 (02) ◽  
pp. 1930002 ◽  
Author(s):  
Aklilu Tesfamichael Baheta ◽  
Kar Kin Looi ◽  
Ahmed Nurye Oumer ◽  
Khairul Habib
Keyword(s):  
Air Conditioning ◽  
Phase Change Materials ◽  
Cooling System ◽  
High Reliability ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Future Research ◽  
Thermoelectric Cooling ◽  
Air Conditioning System ◽  
System Building

The high reliability, the absence of working fluid and auxiliary pipes in the thermoelectric cooling application have attracted the attention of researchers in the last two decades. However, the use of thermoelectric air-conditioning system for building application has not been entirely explored due to its low coefficient of performance (COP) compared to the conventional air conditioning system. To overcome this primary limitation, different COP enhancement techniques of thermoelectric for air conditioning system building application are made available. This paper provides the recent development of thermoelectric air conditioning system in building applications, such as thermoelectric radiant panel ceiling, thermoelectric air duct system and thermoelectric cooling facades. It also provides the different strategies to enhance its performance in order to fit this technology in real building applications such as the integration of water-cooling system, phase change materials, evaporator cooling system and nanofluid micro-channel heat sinks. Lastly, the challenges of thermoelectric air-conditioning systems and future research directions are discussed.

scholarly journals Exergetic performance analysis of low GWP alternative refrigerants for R404A in a refrigeration system

2021 ◽  
Author(s):  
Mehmet Altinkaynak
Keyword(s):  
Cooling System ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Refrigeration System ◽  
Alternative Refrigerants ◽  
Condenser Temperature ◽  
Parametric Analyses ◽  
Low Global Warming Potential ◽  
Very High

Abstract According to the regulation of European Union laws in 2014, it was inevitable to switch to low global warming potential (GWP) fluids in the refrigeration systems where the R404A working fluid is currently used. The GWP of R404A is very high, and the potential for ozone depletion is zero. In this study, energetic and exergetic performance assessment of a theoretical refrigeration system was carried out for R404 refrigerant and its alternatives, comparatively. The analyses were made for R448A, R449A, R452A and R404A. The results of the analysis were presented separately in the tables and graphs. According to the results, the cooling system working with R448A exhibited the best performance with a coefficient of performance (COP) value of 2.467 within the alternatives of R404A followed by R449A and R452A, where the COP values were calculated as 2.419 and 2.313, respectively. In addition, the exergy efficiencies of the system were calculated as 20.62%, 20.22% and 19.33% for R448A, R449A and R452A, respectively. For the base calculations made for R404A, the COP of the system was estimated as 2.477, where the exergy efficiency was 20.71%. Under the same operating conditions, the total exergy destruction rates for R404A, R448A, R449A and R452A working fluids were found to be 3.201 kW, 3.217 kW, 3.298 kW and 3.488 kW, respectively. Furthermore, parametric analyses were carried out in order to investigate the effects of different system parameters such as evaporator and condenser temperature.

scholarly journals Investigating thermal performance of an ice rink cooling system with an underground thermal storage tank

2017 ◽  
Vol 36 (2) ◽  
pp. 314-334 ◽  
Author(s):  
Hakan Tutumlu ◽  
Recep Yumrutaş ◽  
Murtaza Yildirim
Keyword(s):  
Energy Storage ◽  
Analytical Model ◽  
Thermal Performance ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage Tank ◽  
Cooling System ◽  
Operating Time ◽  
Ambient Air ◽  
Coefficient Of Performance

This study deals with mathematical modeling and energy analysis of an ice rink cooling system with an underground thermal energy storage tank. The cooling system consists of an ice rink, chiller unit, and spherical thermal energy storage tank. An analytical model is developed for finding thermal performance of the cooling system. The model is based on formulations for transient heat transfer problem outside the thermal energy storage tank, for the energy needs of chiller unit, and for the ice rink. The solution of the thermal energy storage tank problem is obtained using a similarity transformation and Duhamel superposition techniques. Analytical expressions for heat gain of the ice rink and energy consumption of the chiller unit are derived as a function of inside design air, ambient air, and thermal energy storage tank temperatures. An interactive computer program in Matlab based on the analytical model is prepared for finding hourly variation of water temperature in the thermal energy storage tank, coefficient of performance of the chiller, suitable storage tank volume depending on ice rink area, and timespan required to attain an annually periodic operating condition. Results indicate that operation time of span 6–7 years will be obtained periodically for the system during 10 years operating time.

Thermal Energy Storages Analysis for High Temperature in Air Solar Systems

2012 ◽  
Author(s):  
Assunta Andreozzi ◽  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Salvatore Tamburrino
Keyword(s):  
High Temperature ◽  
Mass Flow ◽  
Thermal Energy ◽  
Solid Material ◽  
Solid Matrix ◽  
Working Fluid ◽  
Storage Medium ◽  
Governing Equations ◽  
Solar Systems ◽  
Porosity Effect

In this paper a high temperature thermal storage in a honeycomb solid matrix is numerically investigated and a parametric analysis is accomplished. In the formulation of the model it is assumed that the system geometry is cylindrical, the fluid and the solid thermophysical properties are temperature independent and radiative heat transfer is take into account whereas the effect of gravity are neglected. Air is employed as the working fluid and the solid material is cordierite. The evaluation of the fluid and thermal behaviors are accomplished assuming the honeycomb as a porous medium. The Brinkman-Forchheimer-extended Darcy model is used in the governing equations and the local thermal non equilibrium is assumed. The commercial CFD Fluent code is used to solve the governing equations in transient regime. Numerical simulations are carried out with storage medium at different mass flow rates of the working fluid and different porosity values. Results show the effects of storage medium, different porosity values, porosity effect and mass flow rate on stored thermal energy and storage time. Results in terms of temperature profiles and stored thermal energy as function of time are presented.

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