基于 CFD 的日光温室墙体蓄热层厚度的确定.

The performance of greenhouse wall thermal storage and release capacity depends on the characteristics of the wall material and the thickness of the thermal storage layer. Determining the thickness of the solar greenhouse thermal storage layer is of great significance for promoting the improvement of the solar greenhouse wall. Parametric model according to the actual size and correlation of the test greenhouse was created based on the solar radiation and air temperature. Thickness of the wall thermal storage layer in different months was simulated in this study. In this paper, January 9th, February 9th, March 6th, and April 6th, 2018 in Urumqi was selected as typical sunny days. The solar radiation on the greenhouse floor and wall surface were used as the input condition, and the outdoor air temperature was the boundary conditions. The internal temperature field including each depth of 0, 10, 20, 30, 40, 50 cm of the greenhouse wall from 9:00 to next day 9:00 were simulated by using Autodesk CFD software. In order to ensure the consistency of CFD geometric models within one day and full release of heat from the greenhouse wall at night, no covering insulation quilt was carried out during the greenhouse test. The accuracy of simulated values was verified by comparing with the measured values. The results showed that the simulation results of the greenhouse wall were agreed well with the test results. The average error of each layer on January 9th, February 9th and March 6th was below 1.5 °C. The error and simulated results lags between the test results and the simulated results on April 6th is large. The trend becomes more pronounced as the depth and wall temperature increased. Under the combined influence of greenhouse wall materials, structures, and light and temperature environments, greenhouse wall heat transfer is a complex unsteady process. The brick wall greenhouse was similar to the soil wall greenhouse. The wall could be divided into “insulation layer, stable layer and heat storage layer”. The thickness of each layer was related to the thermal properties of the wall heat storage material and insulation material. The wall temperature fluctuation was more obvious in the depth range of 0-30 cm according to the temperature field of the wall, the temperature attenuation factor of each layer and the delay time. When the wall depth was more than 30 cm, the greenhouse wall temperature fluctuations was relatively flat and the amplitude is small. As the temperature rose, the internal temperature of the greenhouse wall increased overall, and the temperature fluctuations of the various layers were small. The thickness and fluctuation of the greenhouse heat storage layer were less affected by the external light and temperature environment in the case of the greenhouse structure and insulation performance unchanged. In summary, it was feasible to simulate the change of greenhouse wall temperature field. It was reliable that the thickness of greenhouse wall thermal storage layer determined according to the temperature field variation of greenhouse wall. Solar greenhouse temperature environment dynamic simulation model based on greenhouse structure parameters and environmental parameters also could be established in other regions through the methods provided in this paper. It can provide basis and reference for the improvement and optimization of greenhouse wall structure. [ABSTRACT FROM AUTHOR]