Study On Performance Of Heat Recovery System Of Heat Pipe With Compound Evaporative Cooling

With the rapid development of China’s national economy,the total energy consumption is large and the intensity is high,which brings great pressure to achieve peak carbon neutrality.Building HVAC system energy consumption accounts for a large proportion,HVAC system for industrial buildings to create suitable production conditions,but also for civil buildings to create a comfortable space,reduce HVAC system energy consumption,improve system energy efficiency,to develop resource-saving and environmentally friendly society is very important.Heat recovery of heat pipe is an effective energy saving technology.By using the principle of heat evaporation of phase change working medium in pipe and cold coagulation,the amount of exhaust air cooling can be recovered through phase change of working medium without power device,so as to achieve the effect of energy saving.However,it can only recover sensible heat and is seldom used in air conditioning system.At the same time,in the industrial buildings,there are a lot of low temperature and humidity industrial exhaust,they typically require only after spray to meet environmental requirements by the atmospheric emissions,these industrial exhaust after spray evaporative cooling,the temperature will reduce further,a number of large civil building there are a large number of low temperature and humidity exhaust,will be spray evaporative cooling,the exhaust temperature will also be further reduced.The difference in temperature between fresh air and exhaust air can be enlarged and the efficiency of heat recovery can be improved by heat pipe heat recovery between exhaust air and exhaust air after spray evaporation cooling.In this paper,the evaporative cooling device and heat pipe heat exchanger are combined to form the exhaust air heat recovery system to recover the exhaust air cooling amount,improve the performance of the heat recovery system,and have a good effect of energy saving and carbon reduction.The experimental platform of heat pipe heat recovery system with compound evaporative cooling was set up,and the effects of liquid filling rate and fresh air temperature on heat recovery performance of compound system were studied.The mathematical model of the composite system was established,and the effects of different wind speed,fresh/exhaust air ratio,tube row number of heat pipe exchanger,transverse tube spacing and fin spacing on the heat recovery performance of the composite system were studied and optimized.The following conclusions are obtained:(1)The heat recovery performance of the composite system is obviously better than that of the traditional heat pipe heat recovery system.Under the rated condition,the sensible heat exchange efficiency of the composite system can reach 1.64 times that of the traditional heat pipe heat recovery system,and the energy saving is 1.9 times that of the traditional heat pipe heat recovery system.With the increase of liquid filling rate,the sensible heat exchange efficiency of the composite system increases gradually,and then decreases when it reaches a critical value.The best filling rate range is 30%～50%.(2)The sensible heat exchange efficiency of the composite system and the single heat pipe heat exchanger decreases with the increase of wind speed,but the heat exchange rate increases with the increase of wind speed,and the increase speed gradually slows down.The wind speed should be set in the range of 1.5m/s～2.5m/s.With the increase of the fresh/exhaust air ratio,the sensible heat exchange efficiency of the composite system and the single heat pipe heat exchanger gradually decreases and the reduction rate slows down.The new/exhaust air ratio should be set between 1.1 and 1.2,and not higher than 1.23.(3)The structure of heat pipe exchanger has great influence on the heat recovery performance of composite system.The sensible heat exchange efficiency of the composite system and the single heat pipe exchanger increases with the increase of the number of tube rows,the number of tube rows should not be less than 6,but should not be more than 8.With the increase of the horizontal pipe spacing,the horizontal pipe spacing should be set between35 mm and 45mm;With the increase of the fin spacing decreases,the fin spacing should not be greater than 3.29 mm.Through the research of this paper,the application scenario of heat pipe is enriched,which provides a reference for the heat recovery and energy saving technology of the air conditioning system of industrial and civil buildings.