Investigation On Heat And Moisture Environment Of Earth-to-Air Heat Exchanger In Solar Greenhouse

Agriculture is the foundation of peace,which is related to human development and social stability.Under the background of the national advocacy of green development,a kind of soil air heat exchanger,as a mechanical agriculture,has been widely recognized and paid attention to in solar greenhouse.Based on this background,the characteristics of heat and moisture in greenhouse under the action of soil air heat exchanger were studied.As the main environment of crop growth in greenhouse,air temperature and humidity have important influence on heat exchanger performance and plant growth.The survey points are set up at the cross section of 0.1m,1.5m and 3.0m on the ground of 4.5m/s and 2.5m/s at the exit of the heat exchanger,and the temperature and humidity changes of each point are monitored,thus the characteristics of the heat and moisture distribution are obtained.In order to further study the heat and moisture distribution characteristics of the solar greenhouse under the action of the soil air heat exchanger in the solar greenhouse,a numerical simulation model of the heat and moisture environment of the solar greenhouse under the action of the soil air heat exchanger is established.The model is based on the CFD(Computational Fluid Dynamics)method and uses FLUENT15.0 to numerically solve the steady-state and unsteady state.Three dimensional numerical simulation of humidity and solar radiation was carried out by using component transport model and DO model respectively.The experimental results show the transition season in Taiyuan,the daytime soil air heat exchanger mainly dehumidification and dehumidification of the indoor air,while heating the indoor air at night.And the effect of cooling and dehumidification in the daytime is more obvious.The operation efficiency of soil air heat exchanger is better than that of cloudy day.A good result has been achieved in the solar greenhouse Z=1.5m,which is away from the ground 1.5m.In the Z direction,when the wind speed of heat exchanger tube is 4.5m/s and 2.5m/s,the effect of air heating is most obvious at Z=7m.When the soil air heat exchanger is used to cool the air in greenhouse,when the wind speed of the heat exchanger tube is 2.5m/s,the best effect is at Z=10m.According to the test results,the rationality of the numerical model is verified,and it is further concluded that the air air heat exchanger in the heat exchanger tube is 4.5m/s in the range of Y=0.5m-2.5m and Z=7.0m for the best effect on the air treatment in the solar greenhouse.