Study On The Influence Of Humidair Inlet Velocity Non-uniformity On Performance Of Heat Exchanger On Humid Condition

The heat transfer performance of heat transfer is affected not only by heattransfer area, but also is associated with velocity distribution of incoming air. In fact,the air where come from the upstream fan of heat exchanger is non-uniform, the airhumid is relatively high in the summer, evaporator in the air conditioner indoor unitrun on humid condition, so it is worthy to research the influence of humid airnon-uniform velocity distribution on heat exchanger.Proceed from the classic heat and mass transfer equations, deduced heat balanceequations in finned-tube heat exchanger on humid condition, calculated the influenceof velocity on heat and mass transfer in finned-tube heat exchanger with iterativemethod, when the coming air velocity range from1~2.6m/s. Under the differentvelocity, the critical point between dry condition and humid condition is different, too.The wind speed is higher, it’s becoming humid condition in higher humidity; on thecontrary, the lower the wind speed, it’s becoming humid condition just in lowerhumidity. The amount of dehumidification and latent heat transfer is concave functionof wind speed, the peak point move right with increasing of humidity of air，when thehumidity of air increase to enough high, there’s no peak point appeared, the slope ofcurve tends to0. In the range of0.8~3.0m/s which is the general inlet velocity in heatexchanger, when the relative humidity of coming humid air is lower than60%, theamount of dehumidification is reduced with the increase of wind speed; while whenthe relative humidity of coming humid air is higher than70%, the amount ofdehumidification is increased with the increase of wind speed.The sensible heat transfer difference due to non-uniform velocity distribution isincreased with the increase of the relative humidity, the latent heat transfer differenceand the total heat transfer difference is reduced with the increase of the relativehumidity. Humid air non-uniform velocity distribution mainly affect the latent heattransfer and mass transfer, especially when the relative humidity is low, it’s necessaryto consider the influence of velocity non-uniform distribution.The numerical results show that latent heat transfer decreased and sensible heattransfer increased with the increase of wind speed. There’s nearly no difference onsensible heat transfer due to velocity non-uniform distribution, total heat transferdifference mainly comes from latent heat transfer. The condensation of vapor mainlyoccurred after the first row of tubes, the condensation rate of vapor is relatively higheron the windward side, while it is relatively lower on the leeward side.