Experimental Research On Thermal Characteristics Of Earth-Air Heat Exchanger Under The Role Of Thermal And Moist Environment In Solar Greenhouse

Under the situation that the global food demand is soaring,the agricultural development pattern of efficient solar greenhouse has been the one of important strategies for crop production throughout the year.However,with the rapid progress of solar greenhouse,the problem of high-energy consumption caused by it has gradually attracted researchers’ attention.The dilemma of energy shortage is the focus of China’s economic advance and social progress.Greenhouses driven by renewable sources such as geothermal energy could be a reliable alternative for the traditional farming practice,especially in the era of energy shortage.In light of such requirement,a double-layer Earth-Air Heat Exchanger(EAHE)system has been proposed to simultaneously promote energy conservation and improve the level of environmental microclimate control-level in facility agriculture under cold regions of China.The research mainly on EAHE,which was applied in solar greenhouse under cold regions of China,was elaborated under different operation modes in this article.Results showed the operating EAHE had some disturbance on soil temperature and moisture.The intermittent operation and different modes would boost the soil regeneration.Compared to the soil temperature,the delay and attenuation of the moisture field were more serious in soil with an internal heat source.The disturbance failed to cause fluctuation for soil temperature at the position of Y=0.50 m,the moisture field fluctuation was not obvious at Y=0.37 m,however.Maximum temperature variations provided by EAHE,1 m buried depth,were 9.81 ℃ and-10.88 ℃ under autumn and summer respectively.However,the soil temperature of 2 m underground the greenhouse could reach below 20 ℃ in summer and up to 13 ℃ in winter.The EAHE had smooth dehumidification performance,and the dehydration quantity up to 2149 g/day in M2 daytime.Meanwhile,latent heat occupied a large proportion in heat transfer progress of EAHE.Ignoring the latent heat will lead to a wrong evaluation of the system performance.The maximum average heat transfer capacity of EAHE was 18086.2 W under different modes and the corresponding COP was 8.07,indicating the high efficiency of EAHE.Research results are of great significance in supporting simplified design tools in EAHE,building a more comprehensive database of EAHE and serving agricultural production.