Theoretical And Experimental Research Of New Type Of Hybrid Evaporative Cooling

Marine air conditioner is an indispensable device of the ship,which requires lots of energy for its normal operation.Nowadays,compressed air-conditioner is widely adapted on board,which is not only expensive,but also possess the risk of leakage of refrigerant.Based on evaporative cooling technology,a new type of hybrid evaporative air conditioner is developed.It is such a kind of environmental friendly and energy saving facility that water is employed as the refrigerant.Through the evaporation of water,heat is taken away.Hybrid evaporative air conditioner consists of two sections:dry section and wet section.Ambient air will primarily flows into wet section,decreases its temperature due to the evaporation of water.Then it will pass through dry section,cooled further by the plate.This paper deals with performance and heat transfer mechanism of evaporative air conditioner theoretically and experimentally:(1)Establish the continuity,momentum and energy partial differential equations of air flowing in dry and wet passages.;(2)The formulas of outlet air dry bulb temperature and cooling efficiency of evaporative cooling are derived,Therefore,the influences of dry bulb temperature,relative humidity,plate gap and wind speed on the performance of evaporative air conditioner are analyzed theoretically.The heat transfer resistance of evaporative air conditioner is investigated,which will provide a reference for optimizing evaporative air conditioner.(3)From the experimental point of view,the effects of inlet air dry bulb temperature,relative humidity and spray water density on the performance of evaporative air conditioner are researched.Based on the experimental data obtained,the errors between theoretical and experimental values are calculated and the reasons are figured out.Through research,the following conclusions can be drawn:(1)In the laminar flow state,the Nussle number in the process of air flowing in the dry channel is 7.55.(2)From the theoretical point of view,with the increase of the inlet air dry bulb temperature,temperature difference between inlet and outlet will increase,while cooling efficiency of the evaporative air conditioner hardly changes;As the increase of relative humidity of imported air,temperature difference will be reduced,while cooling efficiency will be constant;When the gap of plate is narrowed,both temperature difference and cooling efficiency will decrease;With the increase of wind speed,both temperature difference and cooling efficiency will decrease.(3)The resistances of convective heat transfer in the dry and wet channels are the major thermal resistances of the evaporative air conditioner,while the thermal resistances of the water film and aluminum plate are the minor.As a consequence,narrowing the space of the channel is an effective method to reduce the total resistances.(4)The following conclusions can be concluded from the experimental results:The influence of inlet air dry bulb temperature on temperature difference and cooling efficiency are similar with theoretical analysis;With the increase of relative humidity of imported air,both temperature difference and cooling efficiency will decrease;Temperature difference and cooling efficiency will be enlarged as the spray density increase before it reach the optimal state.(5)For inlet air dry bulb temperature,the range of error of temperature difference between theoretical and experimental results is 0.42℃～0.73℃;As to cooling efficiency,the range of error is 6.11%～9.06%For relative humidity,the range of error of temperature difference between theoretical and experimental values is 0.52℃～1.27℃,while the range of error of cooling efficiency is 6.98%～22.4%.