Research On Structure And Performance Of Air Cooler In Indirect Cooling Refrigeration System

In view of the indirect cooling refrigeration system has more advantages than the direct cooling refrigeration system,so on the issue of environmental protection and energy saving,many civilian cold storages are changed to indirect cooling refrigeration systems.Considering that it is composed of dual systems on the refrigerant side and the refrigerant side,if you try to improve its operating efficiency,you can also start with the two systems separately.Starting from the refrigerant side system,this subject has carried out related researches on the structure and performance of air coolers by combining experiments and simulations.Taking the fin-tube air cooler as the research object,in the existing technology to improve the operating efficiency of the heat exchanger,taking into account the actual cost and other practical problems,the experiment is done by arranging different pipe-side flow paths,and setting different fan frequencies and warehouse temperatures to the air.The structure and performance of the cooler are optimized.The experiment mainly studied the influence of flow path layout,fan frequency,and storage temperature on the performance and system of the three-row tube fin-tube air cooler.Aiming at the influence factors of gravity effect,forward flow and reverse flow arrangement,five air cooler flow paths are arranged,and the influence of each factor on the performance of the cooler is discussed.After the experimental conditions are determined,the selection of heat exchange equipment is completed,the experimental platform is set up,and the pipeline leak detection is completed,after the initial operation of the system,the air cooler with five flow paths is modeled and simulated,and the air cooler is simulated.The simulation of the model obtains the changing trends of the cooling capacity and heat transfer coefficient of the air cooler side with various working conditions in five different flow path arrangements,and compares them with the experimental results.The experiment tested the change trend of the performance parameters of the air cooler with five flow path arrangements under different storage temperatures and fan frequencies to obtain the best operating conditions for the air cooler,and the heat transfer coefficient of the air cooler under each flow path layout,Cooling capacity,and system power consumption and other important parameters are comprehensively considered to make a reference for the selection of the best flow path layout of the three-row air cooler.Through the experimental and simulation research on the fin-tube air cooler,the conclusions are as follows:(1)Under the same experimental requirements,a comparative study of three-row tubefin-tube air coolers under five flow path arrangements found that in a single-flow arrangement,the heat transfer temperature difference in the counter-flow arrangement is 1.26%higher than that in the downstream arrangement.4.44%,and the heat transfer coefficient is slightly larger than the latter,and the system power consumption is 4.9%～9.48% lower,and the refrigerant pressure drop is larger by 13.95%～15.2%,so the countercurrent arrangement has better heat exchange performance;in the countercurrent arrangement In the process,as the number of processes increases,the heat transfer temperature difference on the refrigerant side will increase,and because the refrigerant flow rate remains unchanged,the heat transfer coefficient will decrease with the increase in the number of flow paths.At this time,the heat transfer temperature difference will increase.The cooling capacity has a great influence,which will increase the cooling capacity,and the system power consumption will also increase,and the pressure drop on the refrigerant side will decrease;in the three-process arrangement,it can be found that the flow path and the reverse flow path are arranged under the effect of gravity.In comparison,its cooling capacity is 1.27% to 4.95% lower,and when the former cools the air,there is a large difference in heat transfer performance on different wind sides,which is unfavorable for heat transfer.(2)Under the optimal fan operating frequency,during the same working condition,the temperature of the refrigerant side of the three-row tube-fin-tube air cooler under the five flow path arrangements has different changes in the temperature along the side of the refrigerant.Among them,the single process is smooth.Nearly 90% of the temperature rise process of the refrigerant carrier in the flow arrangement occurs in the windward and middle side tube side,while the temperature of the refrigerant carrier in the leeward side tube side changes very little,indicating that the heat exchange is extremely uneven;in the countercurrent flow path,With the increase in the number of processes,the slope of the curve of the refrigerant side temperature with the tube pass is increasing,but the overall change trend is the same.Based on the analysis of the change in the temperature of the refrigerant in each tube,it is found that as the number of processes increases,The temperature change of each wind side pipeline gradually tends to be uniform.Among them,the layout of the three processes is the best.The temperature rise of the refrigerant on the windward side can reach25% of the total temperature rise.In the multi-process countercurrent arrangement,no matter which process,The change trend of the temperature of the refrigerant is almost the same;in the three-process flow path considering the gravity effect,each process is located on a different wind side,resulting in uneven heat exchange.Among them,the temperature rise of the refrigerant is the largest on the windward side.The heat is the best,while the temperature rise of the refrigerant on the leeward side is small,the heat exchange is poor,and the overall heat exchange process is extremely uneven.Therefore,it is necessary to avoid this type of arrangement in the flow path arrangement.(3)Under different fan frequencies,the layout of each flow path showed a similar change trend.Among them,the heat transfer coefficient of the air cooler showed an increasing trend with the increase of wind speed,because as the wind speed increased,the air side The heat transfer coefficient increases,so the total heat transfer coefficient will increase;the heat transfer temperature difference on the air cooler side shows a decreasing trend with the increase of wind speed;the cooling capacity of each flow path arrangement increases first and then decreases with the increase of air volume At 30 Hz,it reaches its peak value.At this time,the cooling capacity is greatly affected by the heat exchange temperature difference;the power consumption of the system also increases with the increase of the fan frequency.The change trend of the system COP is consistent with the change trend of the cooling capacity,and reaches at 30 Hz.Peak value,at this time the cooling capacity is large,but the power consumption is small.