Study Of Airside Heat And Mass Transfer Characteristics Of Plain Finned Tube Heat Exchangers In Wet Conditions

Heat exchangers, as the heat transfer equipments, are widely used in HVAC (Heating, Ventilating and Air Conditioning) field. With the rapid development of the national economy, air-conditioner comes into not only our home, but also the large indoor entertainment venues, shopping market. It’s bound to cause a great deal of energy consumption. Finned tube heat exchangers, as the most common components in refrigeration and air conditioning systems, play a key role in reducing energy consumption. So detailed analysis of heat and mass transfer of the finned tube heat exchanger is an effective means to optimize its structure, and then get our ultimate aim-energy conservation.The main parameters that affect the performance of finned tube heat exchanger are fin shape, fin pitch, fin thickness, arrangement of tube rows, tube diameter, wet and dry bulb temperature, air flow rate and so on. Recently, it can be seen from the large number of domestic and foreign research information, that there are less researches on condensation heat transfer of finned tube heat exchanger, and most researchers concentrate on the experiment and simulation of dry air flow and heat transfer. However, there is really a certain amount of water vapor in the air environment, and water vapor condensation on the finned tube heat exchanger is a common phenomenon, which happens in various fields of refrigeration. Compared with dry conditions, there is conservation of mass and energy (latent heat) in wet conditions, which is the characteristics of heat and mass transfer of moist air.In this paper, the research question is the condensation heat transfer characteristics of two rows plain finned tube heat exchanger in wet conditions. By adding UDF (User-Defined Function), Computational Fluid Dynamics (CFD) method is used to simulate and analyze the performance under different inlet velocity and different relative humidity of moist air. The simulation results show that mass fraction of h2o decreases gradually along the air flow direction in wet conditions. The sensible heat transfer coefficient is almost equal to that in dry conditions, but the total heat transfer coefficient is far greater than that in dry conditions, when the relative humidity of inlet air is60%, the ratio is about1.86. Relative humidity of inlet air has important effects on the total heat transfer coefficient. Wall temperature has certain effects on the total heat transfer coefficients, but has little effects on the sensible heat transfer coefficient. In wet conditions, heat transfer effect of staggered plain fin is slightly better than that of aligned plain fin, and fin pitch has little influence on the total heat transfer coefficient.