| The traditional active heat storage type solar greenhouse has problems such as high temperature and humidity in winter,uneven airflow,and time-consuming and labor-intensive construction.Based on the previous research,this paper designs a three-dimensional heat storage circulation system and applies it in the time-and labor-saving modular solar greenhouse,firstly,we establish a heat transfer model and verify and optimize this model by CFD software simulation,meanwhile,we investigate the thermal environment of different modular heat storage wall solar greenhouses(soil module solar greenhouse SG,water module solar greenhouse WG,stone module solar greenhouse PG)by combining with the field test.The overall performance of this modular solar greenhouse was evaluated by heat transfer efficiency and construction cost analysis.The main results are as follows.(1)Firstly,through the comparison of indoor and outdoor temperatures of the pre-test greenhouse,it was found that the average nighttime temperature of the three greenhouses was 13-15℃higher than the outdoor temperature,and the average nighttime temperature of SG was better than that of WG and PG in different types of weather.then the heat transfer model was established according to the system design,and the simulation was verified by CFD software,and the simulation results showed that the average error of airflow field,temperature and humidity field of the three greenhouses were The simulation results show that the average errors of airflow and temperature and humidity fields of the three greenhouses are less than 15%,and the results are in good agreement,which shows that the model can reflect the temperature changes inside the greenhouse well.(2)From the thermal performance analysis of the greenhouse,according to the performance of air inlet and outlet temperatures and the duration of heat storage and release in different weather,the thermal insulation performance of SG was slightly better than that of WG and PG,and then it was calculated by the formula that the airflow in PG was uniformly lower.The typical heat storage in sunny days of the three greenhouses are 485.88,475.42,314.58 MJ;the heat release are 104.22,113.45,105.10MJ;the typical heat release in cloudy days are 44.09,57.29,72.71 MJ;from the viewpoint of energy efficiency ratio,the typical heat storage stages in sunny days are62.75,61.97,16.88.16.88,6.13,5.96,1.89 for the typical sunny day heat release stage and 18.23,18.14,4.77 for the typical cloudy day heat release stage,respectively,through the heat storage and release efficiency of 19.01%,18.60%,26.69%respectively,which illustrates the low overall thermal insulation of PG.Combined with the greenhouse construction cost analysis,SG was 25.5 and 12.7 RMB/m~2 lower than WG and PG,respectively,indicating that the overall performance of SG was better than the other two greenhouses.(3)The comparison of the environmental parameters inside the traditional thick-walled solar greenhouse(G1)and the modular heat storage wall solar greenhouse(G2)shows that the temperature performance of the two greenhouses is not much different during the day(temperature<1℃),while G2 is 3.77℃higher than G1 at night,and the comparison of the temperature at different depths of the back wall and soil shows that the night temperature performance of G2 is better than G1,which is more suitable for crop growth and fruit production,and it is also calculated that The heat storage and energy efficiency ratio of G2 system are higher than that of SG,which verifies the reliability of this optimized scheme to improve the pipe diameter of 200 mm.To sum up,the modular heat storage wall solar greenhouse can improve the uneven air flow and increase the active heat storage and release to a certain extent,so as to improve the thermal performance in the greenhouse,achieve the effect of energy saving and cost reduction,and can be popularized and applied in a certain area. |
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