Experimental Study On Heat Transfer And Dehumidification Characteristics Of Evaporation Coil With Two Different Refrigeration Circuits

Finned tube heat exchanger is widely used in the field of air conditioning,its flow and heat transfer characteristics have a significant impact on the energy efficiency of refrigeration system.In order to further improve the performance of a fresh air unit and optimize the unit design,in this paper,a parallel first forward and then reverse evaporation coil is proposed,which is compared with the full countercurrent evaporation coil,the heat transfer performance and dehumidification performance of two groups of evaporation coils under different operating conditions are experimentally studied.This paper analyzes and studies the influence of process and loop design on finned tube heat exchanger,the performance experimental devices of full countercurrent evaporation coil and parallel first forward then reverse evaporation coil are designed,the two groups of evaporation coils are experimentally studied in the enthalpy difference laboratory,the heat transfer performance and dehumidification performance of two groups of evaporation coils under different operating conditions are compared and analyzed.The experimental results show that: With the increase of the head-on wind speed,the cooling capacity of the full countercurrent evaporation coil tends to the maximum when the head-on wind speed is 2.8m/s,and the parallel first forward then reverse evaporation coil tends to the maximum when the head-on wind speed is 3.0m/s,the dehumidification capacity of the two groups of evaporation coils tends to the maximum when the head-on wind speed is 2.8m/s;Compared with the full countercurrent evaporation coil,the parallel first forward then reverse evaporation coil increases the heat transfer performance and weakens the dehumidification performance.With the increase of compressor frequency,the heat exchange and dehumidification performance of parallel first forward then reverse evaporation coil is faster than that of full reverse flow evaporation coil,which is more suitable for operation at the frequency of high-pressure compressor.When the relative humidity increases from 35% to 50%,the cooling capacity of the full countercurrent evaporation coil increases rapidly,and the relative humidity increases from 25% to 50%,the cooling capacity of the parallel type first forward and then reverse evaporation coil increases rapidly,the cooling capacity and dehumidification capacity of the two groups of evaporation coils begin to reach the maximum when the relative humidity is 50%,the relative humidity of parallel first forward then reverse evaporation coil is lower than that of full reverse flow evaporation coil when entering wet condition and the heat exchange and dehumidification performance of the two groups of evaporation coils begins to weaken when the relative humidity is 50%.Keep the air inlet dry bulb temperature at 35℃,the wet bulb temperature at 28.1℃,and the compressor frequency at 100 Hz,under different head-on wind speeds,compared with the full countercurrent evaporation coil,the parallel first forward then reverse evaporation coil has an average increase of 9.40% in cooling capacity,6.16% in dehumidification capacity and 12.36%in air side pressure drop;At the same time,when the head-on wind speed is 2.2m/s,under different compressor frequencies,compared with the full countercurrent evaporation coil,the parallel first forward then reverse evaporation coil has an average increase of 4.90% in cooling capacity,4.70% in dehumidification capacity and 11.60% in air side pressure drop;When the head-on wind speed is 2.2m/s and the compressor frequency is 90 Hz,under different relative humidity,compared with the full countercurrent evaporation coil,the cooling capacity of the parallel first forward then reverse evaporation coil increases by 6.80%,the dehumidification capacity increases by 13.73% and the air side pressure drop increases by 10.50%.It can be seen that the parallel first forward then reverse evaporation coil has better heat exchange and dehumidification performance than the full countercurrent evaporation coil under different operating conditions,but the air side pressure drop increases.The research conclusion of this paper is to reasonably design the finned tube heat exchanger circuit and improve the performance of air conditioning equipment,so as to reduce the system energy consumption and provide data support and reference.