Development of an Advanced Ejector Cooling System
Date Issued
2005
Date
2005
Author(s)
Hu, Sheng-Shiung
DOI
zh-TW
Abstract
Some crucial problems hinder conventional ejector cooling system (ECS) from putting in use, like reliability of the mechanical circulating pump, stability of the back pressure of ejector, and heat recovery from solar energy or waste heat etc.
Taking reliability of the mechanical circulating pump and heat recovery problems into account, a new ECS is proposed. This new ECS utilizes a multi-function generator (MFG) to eliminate the mechanical circulating pump. The MFG is designed based on the pressure equilibration between high and low pressure through heating and cooling process. In this design, an ECS that contains no moving components and is entirely powered by heat can be achieved. A prototype using refrigerant R141b a working fluid was constructed and tested in the present study. The experimental results show that the system coefficient of performance (COP) is 0.225 and the cooling capacity is 0.75 kW at generating temperature (Tg) 89oC, condensing temperature (Tc) 37 oC and evaporating temperature (Te) 8.5 oC. It is shown that a continuous operation for the generation of cooling effect in an ECS with MFG can be achieved. This cooling machine can be very reliable since there is no moving part.
With the phasing-out of CFCs and HCFCs on the basis of the Montreal and subsequent international Protocols, an environment friendly refrigerant, R365mfc, for substituting R141b is studied. Comparisons of physical properties, theoretical performance of ECS and experiment tests with R141b and R365mfc are made. The results show R365mfc needs bigger geometric design parameter of the ejector A3/At at the same generating temperature, condensing temperature and evaporating temperature. In the same A3/At, R141b has higher cooling capacity and COP while R365mfc has higher critical condensing temperature. Experiment results show, the ECS with R365mfc and ejector A-G, the COP is 0.107 and the cooling capacity is 0.32 kW at Tg =89.7oC, Tc =36.7 oC and Te =8.2 oC. In the same ejector A-G, the COP with R365mfc is lower then R141b, but the COP with R365mfc can be improved by changing ejector into higher A3/At ratio.
A new cooling tower adopting cellulose pads as filling material to deal with the stability problem of the back pressure of ejector is also proposed. A correlation equation for a fundamental cellulose cell (0.3m 0.3m 0.15m) within ±5% is acquired and the prediction of the outlet temperature of the cooling tower using the correlation is also within ±5% error. According to ASHRAE test conditions, the dry-bulb temperature should be oC and the wet-bulb temperature should be oC, in our test, the new cooling tower with cellulose pad has better performance and smaller size than the same scale commercial cooling tower. For about 10kW heat-transfer rate, the size of the new cooling tower with cellulose pad is only half of the size of the commercial one.
This research successfully proposed (1) a new ECS with MFG to eliminate the mechanical circulating pump; (2) studies and tests of ECS with R365mfc for substituting R141b; (3) a new cooling tower adopting cellulose pads as filling material to deal with the stability of the back pressure of ejector. Hence, this research does significant contributions to the promotion of the ECS.
Subjects
噴射器
製冷
無動件
熱能驅動
ejector
cooling
no moving part
heat-driven
SDGs
Type
thesis
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