Effects of temperature and heat release volume of north wall and soil on night air temperature in solar greenhouse with thick earth wall

To investigate the reason of low air temperature in solar greenhouse at night which leads crops vulnerable to cold damage and freezing damage, the effects of temperature and heat release volume of the north wall and soil on night air temperature were examined under different weather conditions, with the heat flow process of solar greenhouse as trial subject and unsteady heat conduction theory as the research basis. The weather conditions mainly referred to the solar radiation intensity during the day and the external temperature at night. The results showed that the temperature integrals of the north wall and soil under the four types of weather conditions were 162.92°C, 91.68°C, 141.6°C and 142.02°C, and the night air temperature integrals of solar greenhouse were 133.3°C, 57.33°C, 105.4°C and 116.9°C, respectively; while the integral of heat release volumes of the north wall and soil were 2427.96, 3406.56, 3273.18 and 2220.29 W, respectively. These results demonstrated that the temperature of the north wall and soil have a direct effect in the night air temperature of solar greenhouse, and the heat release volume is linear correlated with temperature difference between the north wall and soil and the greenhouse air. When heat absorption of north and soil during daytime is insufficient to compensate heat release of greenhouse at night, night air temperature will decrease, and heating is necessary. © 2020, Asian Association for Agricultural Engineering. All rights reserved.