Study On Enhanced Heat Transfer Of Tubular Indirect Evaporative Cooler

After the reform and opening up,China’s economy is developing at a rapid pace,energy supply is becoming more and more tense,and the energy crisis is imminent.China’s construction industry consumes the most energy,accounting for more than 30%of the total domestic energy consumption,of which the energy consumed by air-conditioning is the largest in the construction industry,up to about 60%.Therefore,reducing air conditioning energy consumption is an effective way to reduce building energy consumption.Lanzhou City,as one of the first 79 pilot cities for the statistical energy consumption of buildings identified by the Ministry of Housing and Urban-Rural Development,the city government and the people feel a long way to go.Lanzhou is located inland and is a temperate continental climate.The temperature difference is large,the precipitation is less,the climate is dry,the wind and sand are more dusty and the water quality is not good.Combined with the climatic characteristics of Lanzhou and the analysis of the performance of evaporative cooling units commonly used,tubular indirect evaporative cooling air conditioning units can not only exert their own advantages,but also have strong applicability to poor outdoor conditions.This paper introduces the research progress of tubular indirect evaporative coolers at home and abroad,and proposes the research purposes,methods,significance and current problems in the field of tubular indirect evaporative cooler Enhanced heat transfer.This study details the numerical simulation of tubular indirect evaporative cooler using ANSYS14.5.The establishment process of the primary air numerical model of the tubular indirect evaporative cooler with the enhanced heat transfer model inserted spiral inside the tube and the external heat transfer model of the external wing structure is studied.The simulation results of the temperature distribution cloud map and the path temperature distribution curve change graph were analyzed.At the same time,the simulation results of the application of the light pipe tubular indirect evaporative cooler are compared with the tubular indirect evaporative cooler with the inserted spiral or the external wing structure.The three models have a length of 1200 mm and a primary air inlet temperature of 40 0 C.It is concluded that:(1)The exit temperature of the light pipe cylinder model is about 38.684 ℃,and the temperature drop is 1.316 ℃,3.29%.(2)The outlet temperature of the in-tube enhanced heat transfer model is 35.660 ℃,and the temperature drop is 4.34 ℃,which is 10.85%lower.(3)The external heat transfer model of the tube is 38.576 ℃,the temperature drop is 1.424 ℃,3.56%.Finally,this study proposes a coupled enhanced heat transfer structure with interpolated spiral-coupling external wing type,and takes the optimal parameter setting scheme of the tubular indirect evaporative cooler as the objective,and selects the tubular structural parameters as the influencing factors of the test were simulated by the orthogonal design test method.Through the analysis of the orthogonal test results,it is found that:(1)For the inlet-to-outlet temperature ratio,the primary and secondary order of influence of each factor is:helix number>helix diameter>fin ratio(fin surface area/light pipe)External surface area>>wing structure radius heart distance,the optimal horizontal combination is:helix number 17,helix diameter D=4,wing ratio(fin outer surface area/outer tube surface area)L1 is 22.5,wing type The structural radius center distance L is 2d1.(2)Simulation experiments found that the relatively optimal parameter setting of the coupled tube evaporative heat exchanger heat transfer structure can reduce the outlet temperature to 33.044 ℃,the temperature drop is 6.956 ℃,a decrease of 17.39%,compared to a separate tube or the outer structure of the pipe is arranged,and the heat exchange effect is greatly enhanced.