Performance Test And Numerical Analysis Of Microchannel Evaporator Refrigeration System

Micro-channel evaporator is popular for its low cost and weight, compact structure and good heat exchanging effect in refrigeration and air conditioning industry. Micro-Channel evaporator, also known as parallel flow evaporator, whose characteristic is that refrigerant flows into several flat pipes parallel arranged at the same time. As a result of that, the distribution problem of the flow in flat pipes exists during the process of refrigerant flowing. Now, as a hot issues, investigation of micro-channel evaporator is faced with main problems of the distribution of refrigerant flow and the performance of refrigerating system. After a large number of domestic and foreign literature reading,the scheme that conducting secondary throttle by inserting distribution pipe into collecting pipe of micro-channel evaporator is found lacking of further research. Based on those, the application of micro-channel evaporator in refrigerating system is investigated by experiment and simulation in this study.First, the performance of air-conditioning samples using finned-pipe evaporator and micro-channel evaporator with uniform-opening distribution pipes are tested by enthalpy potential experimental method and photos of the micro-channel evaporator are taken by IR camera. The results of the contrast show that the cooling capacity of the latter is 2.24%?3.32% higher than former and the EER(energy efficiency ratio) of the latter is 2.60%?3.53% higher than the former.A same test of micro-channel evaporator air-conditioning sample with uneven?opening distribution pipes is conducted. The results of performance comparison between micro-channel evaporator air-conditioning sample with uneven-opening and uniform-opening distribution pipes shows that the cooling capacity of the latter is 1.61%?2.38% higher than former and the EER(energy efficiency ratio) of the latter is 1.10%-2.18% higher than the former. The contrastive IR imaging results show that the distribution of the refrigerant flow in the latter is more uniform than the former.In order to find the theoretical basis of the experiment results, a further investigation about the distribution law of flow media in micro-channel evaporator is conducted by numerical simulation. In the simulation, the 41 channels of the micro-channel evaporator is simplified to 24 channels for ease of operation. First, a simulation is conducted for two conditions including that openings of distribution pipes are upward when ?=0° and downward when ?=180°. The results show that the distribution of flow media is better when ?=180°.A simulation is conducted for micro-channel evaporator with uniform-opening distribution pipes. The scheme of uniform opening is modified to uneven opening based on the simulation results and goes ahead with another simulation. The distribution uniformity of flow media in the micro-channel evaporator with uniform-opening distribution pipe and micro-channel evaporator with uneven-opening distribution pipe are contrasted by speed nephogram, temperature nephogram and calculation results of flow media non-uniformity in flat pipes of both. The results show that the distribution of flow media in the latter is more uniform than in the former.