Analysis Of Soil Heat Transfer And Hourly Calculation Of Soil Heat Transfer In A Single-slope Solar Greenhouse

As an important part of facility agriculture in China,the solar greenhouse has made great contributions to the “vegetable basket project” for urban residents.With regard to the problems of soil deep temperature,heat storage and release in the thermal environment of a solar greenhouse,the indoor microclimate and soil temperature distribution were measured in the single-slope tested solar greenhouse,an onedimensional soil periodic heat transfer model was established in the single-slope solar greenhouse,the condition of the air temperature and soil temperature and the soil heat transfer characteristics in the single-slope solar greenhouse were discussed by means of field test and theory analysis.Several environmental parameters,such as air temperature,relative humidity,solar radiation and soil temperature,were measured in the single-slope tested solar greenhouse in Shandong Jianzhu University in Jinan,Shandong province(40 m length and 8 m span,unplanted greenhouse).The results showed that the north wall(thermal storage wall)outperformed soil under the same area in terms of regulating indoor air temperature in the solar greenhouse on sunny days,And vice versa.The maximum temperature difference in the east-west direction of the soil temperature(0.1-0.5 m deep)of the solar greenhouse with 40 m length was not more than 3℃;the maximum temperature difference between the north and the south of the planting area with a span of 8 m was less than 4℃,and the surface soil temperature at the north soil was higher than that at the south soil;however,with the increase of soil depth,soil temperature curves tended to be stable and consistent.Based on the fact that is the small temperature difference of soil temperature along the length and span direction,a single-slope solar greenhouse one-dimensional periodic soil heat transfer model was established to investigate the variations of soil temperature periodically in the single-slope solar greenhouse,the hourly heat transfer of single-slope solar greenhouse soil,and so on.Compared with the field test results,the relative root mean square error of the heat transfer model was less than 10%,which verified the accuracy of the mathematical model.The calculation of one-dimensional soil periodic heat transfer in the single-slope solar greenhouse indicated that in the presence of solar radiation,the solar radiation absorbed by the soil of solar greenhouse was mainly used for the soil heat loss due to water evaporation and the soil surface heat transfer to the deep soil(i.e.the soil heat storage);in the absence of solar radiation,the heat transferred from the deep soil to the soil surface was mainly used for thermal radiation on the soil surface and other surfaces in the single-slope solar greenhouse.