Experiment Research Of Dynamic Heat Transfer Characteristics For Earth-air Heat Exchanger In Greenhouse Under Coupled Heat And Moisture Transfer

Underground soil layer has strong absorption of heat，release and heatstorage capacity coupled with the temperature wave attenuation and delay，thetemperature is constant throughout the year relative to outdoor temperature.Earth-air heat exchanger is a kind of renewable energy utilization way becauseof using soil in geothermal energy storage to cool or heat air. Research of heattransfer characteristics inside the greenhouse is rare at home and abroad. In thispaper，we made experimental research of dynamic heat transfer characteristicsfor EAHE in Greenhouse in north of China in summer under coupled heat andmoisture transfer.The article describes the earth-air heat exchanger in the experiment andnumerical simulation research at home and abroad briefly. The air temperatureand humidity in different location of pipe as well as soil temperature were testedand analysised by the statistical software SPSS under different air velocity of0.5m/s、1.5m/s and4.5m/s through the EAHE which had been set up.The results showed that the EAHE had a good effect on air cooling for greenhouse in summe. The longer the length of heat exchange pipe，the smallerand lower outlet air temperature is. Meanwhile，the cooling effect was moreobvious during the day. At the same time，the higher of the air velocity，thehigher of the outlet air temperature，so did the volatility. Heat transfer rateincreases with the air velocity in a certain range. The process of heat transfer iscooling and humidification and the latent heat could not be neglected as theamount was large. The EAHE running for long time would lead to the increaseof soil temperature and decrease of EAHE efficiency. The datas of air coolingand heating in pipe were fitted by the mean of statistical software SPSS as wellas the significance of fitting formula was tested. From the prospective offormula and heat transfer rate，the best entrance air velocity when air be heatedand coolled were respectively3.8m/s，5.9m/s. Combining with the literature [44]，it can cause thermal interference under the condition of laying pipe spacing of1.0m and heat transfer effect will decline.