Study On Heat And Mass Transfer Characteristics Of Humid Air In Tube-fin Evaporator

Affected by global warming,the energy consumption of refrigeration and air conditioning continues to increase.Under the background of energy shortage,the research of the tube-fin evaporator what is a key component of energy consumption in refrigeration and air-conditioning systems,can improve the energy efficiency of the system and achieve energy-saving and emission-reduction effects.The study of the main heat resistance of the finned tube heat exchanger on the wet air side is of great significance for the improvement of air heat and mass transfer performance.Analysis of the effect of circular and elliptical tube evaporator structures on the moisture resistance,heat and mass transfer characteristics and comprehensive performance parameters under different intake air parameters which can facilitate the design and application of tubular fin evaporators.Based on the analysis of the mechanism of the wet air heat and mass transfer process,this paper establishes a numerical model of the condensation mass transfer of moist air.The experimental and literature results verify that the numerical model is correct and reasonable.Analyzed the numerical simulation results of the circular and elliptical tube fin evaporator under different inlet parameters were obtained:?1?The dimensionless number of resistance?f?,heat transfer factor?jh?and mass transfer factor?jm?on the moist air side in tube fin evaporator will decrease with the increase of the distance from the center of the tube and Re_DC,and increase with the increase of the diameter of the tube.The ratio of ellipse major and minor axis?a/b?has a great influence on the performance of the evaporator with a large equivalent diameter elliptical tube on the moist air side:as the a/b values increase,f decreases,jh and jm increase.The number of jh and jm will all increase with the increase of relative humidity.The comprehensive parameters?j/f?will decrease with the increase of the equivalent diameter of tube and Re _DC,increase with the increase of distance from the center of the tube.The j/f of elliptical tube evaporator increases with the increase of ratio of ellipse major and minor axis.The equivalent diameter of tube has a greater effect on the comprehensive performance parameters of the evaporator than the distance from the center of the tube.?2?Evaporator fin efficiency decreases with increasing Re _DCC and distance from the center of the tube,and increases with increasing the diameter of the tube.As the relative humidity of the inlet increases,the efficiency of the fins of the small-diameter evaporator decreases,and the efficiency of the fins of the large-diameter evaporator is approximately constant.The elliptical tube evaporator fin efficiency increases as a/b increases.In large-diameter elliptical evaporators,the effect of a/b is negligible.?3?The Le_f of the tube fin evaporator decreases with the increase of the center distance of the tube and Re_DC.The Le_f of circular tube evaporator with small diameter and small tube center distance will increase with Re_DC increase then decrease;The Le_f of circular tube evaporator with large diameter and small tube center distance will increases with increasing Re _DC.The Le_f of elliptical tube evaporator with small diameter and large axial ratio will increase with Re _DC increase then decrease.Under Re _DC>2000 conditions,the Le_f of elliptical tube evaporator with the large tube center distance increases with increaseing the Re _DC.?4?The f of circular tube evaporator is larger than the elliptical tube evaporator,and the jm,jh,fin efficiency,j/f are all smaller than the elliptical tube evaporator.The j/f of circular tube evaporator with laeger tube center distance is more than the elliptical tube evaporator with small tube center distance.Under the condition of large Re_DC,the inlet wind velocity has little effect on the mass transfer coefficient of the elliptical tube evaporator with large equivalent diameter and small tube center distance.