Key Factors Study On Affecting Heat Transfer Performance Of Dew Point Indirect Evaporative Cooler

With the increasing clean demand and low carbon development in China,evaporative cooling technology has gradually become a key technology to reduce the energy consumption of building air conditioners.In order to make the evaporative cooling supply air temperature as close as possible to the dew point temperature limit,the study of the dew point indirect evaporative cooler is particularly important.In order to enhance the heat transfer of the dew point indirect evaporative cooler,this paper analyzes three key influencing factors that affect its heat transfer efficiency: core material,water distribution form and air flow path structure.In terms of core material: the fractal fiber theory was used to analyze the polymer fiber material.Establish a fractal thermal model of fiber material and perform a series of derivation calculations.It is concluded that the effective thermal conductivity of the polymer fiber material is?0.057(7)?(28)KmW(8).The factors influencing the thermal conductivity of polymer fiber materials are.the porosity of the plant fiber material,the thermal conductivity of the material in the pore cavity,the thermal conductivity of the fiber matrix and the thermal conductivity of the polymer material.In terms of water distribution form : spray water distributor used in the countercurrent dew point indirect evaporative cooler prototype is optimized and replaced,and the nozzle of the water distribution device is replaced.It is found that the same is the case that spray for 8 seconds and stop for 1 minute.The solid conical nozzle has a poor water effect,while the spiral nozzle has a large amount of water.The water volume in the center of the nozzle is 8 seconds and 62 ml,and the spray uniform distribution coefficient is 1.35.A spiral nozzle can be used to replace the solid cone nozzle used in the current dew point indirect evaporative cooler.The hose watering method was tested and it was found that the hose cloth also had some unevenness.The intermittent water distribution time of the spray water was tested on the composite dew point indirect evaporative cooler.The test results showed that the wet bulb efficiency and the temperature drop range of the cooler were both smaller in the case of the currently applied spray for 8 seconds and stop for 1 minute.When thetemperature of the inlet dry bulb temperature is 40 °C,the cooling temperature of the cooler for spray 10 seconds and stop 1 minute is 15.8 °C,the wet bulb efficiency is134.1%,and the water consumption is small,4.81 L/h.Therefore,spraying for 10 seconds and stop 1 minute can replace the intermittent water distribution time of the current dew point indirect evaporative cooler for spray 8 seconds to stop for 1 minute.In terms of air flow path structure: Temperature field simulation is performed for the channel unit of the counter-flow dew point indirect evaporative cooler.It is found that under standard dry conditions,the simulated dry bulb temperature of the primary air outlet is 22 ° C ~ 24 ° C,which is almost the same as the actual test results,and the model accuracy is high.Through the analysis of the temperature field on the side of the wet channel,it is found that the uniformity of the water distribution of the water distribution device has a certain influence on the heat exchange efficiency of the cooler.This paper has a total of 58 pictures,3 tables,and 66 references.