Indoor Environment Simulation And Experiment Study On A Novel Removable North Wall Greenhouse

Southern of Jiangsu Province(Southern Jiangsu)located at southeast coast in China.It is divided by Nanjing,Zhenjiang,Changzhou,Wuxi and Suzhou on the administrative divisions.The weather of Southern Jiangsu is hot in summer while in winter there’s low temperature.Plastic greenhouse is the main horticulture facility for crop production in summer.In order to improve the indoor temperature in winter,double cover even multi covers are used to produce crop.But at the same time,double covers result in the light intensity declined that effect the photosynthetic performance of crop inside greenhouse.So the problem of low temperature and less illumination exited in plastic greenhouse is needed to be solved.Traditional solar greenhouse in North area has the advantage of large illumination;less heat loss and well heat keep performance.The plastic greenhouse costs low and get better effect of natural ventilation.This study combined the advantages of solar greenhouse and plastic greenhouse,composed a novel greenhouse with removable north wall which can used both in summer and winter.The new type of greenhouse has the same structure as traditional solar-greenhouse.But its north wall and north roof are covered by insulation material.In winter,the material can play the important role of thermal insulation in order to improve the temperature of indoor at night.While in summer,the material was removed for ventilation and cooling.Due to a lot of manpower,material and finacial resources would be spent for the construction of the novel greenhouse and the observation of the indoor environment,thus thermal performance in winter and ventilation effect of the novel greenhouse should be studied before construction.This study compared the effect of heat preservation in winter and ventilation and cooling in summer of the novel greenhouse、traditional solar-greenhouse and plastic greenhouse based on the theory of Computational Fluid Dynamics(CFD).It aims to provide theoretical basis for the construction of the novel greenhouse.Under the feasible condition in theory,the novel greenhouse was built in Changshu,Jiangsu province,China.The indoor and outdoor environment was monitored all aroud the year.Based on CFD,the novel greenhouse and plastic greenhouse was studied in summer while the novel greenhouse and double tunnel was studied in winter.Taking the outdoor climate paraments as variable boundary contion,the field of indoor air temperature and velocity was simulated and tested by experiment datas.The effect of heat preservation in winter and ventilation and cooling in summer of the novel greenhouse was comparative studied under three weather conditions(sunny,cloudy,rainy).The results are as follows:1.The result of numemrical simulation about novel greenhouse,traditional solar greenhouse and plastic greenhouse shows that there was no obvious difference in heat keep performance between novel greenhouse and traditional solar greenhouse in winter.But compared with plastic greenhouse,the novel greenhouse had higher indoor temperature during nighttime and coule provide better environment for crop production in winter.In summer,there are no obvious differences between both in indoor temperatures and ground temperatures of the novel greenhouse and plastic greenhouse when the vents are closed.While when the vents are opened,the new type greenhouse is superior to plastic greenhouse in interior temperature distribution.According to the result,the construction of the novel greenhouse is feasible.2.Under three weather conditions in summer,the result of the comparision between novel greenhouse and plastic greenhouse shows that there was no obvious temperature difference of the two horticulture facilities during nighttime in sunny day and cloudy day.But the difference increased after sunrise and both showed that the temperature inside novel greenhouse was lower than plastic greenhouse.In sunny day,the maximum value of temperature difference between the two greenhouses was 7.1 ℃ while the value was 4.8 ℃ in cloudy day.The average value of the temperature difference throughout the day was 2.3 ℃ in sunny day and 1.9 ℃ in cloudy day.There’s no obvious difference between novel greenhouse and plastic greenhouse in rainy day.According to the result,the application of novel greenhouse is feasible in summer.3.In winter,the average indoor temperature of novel greenhouse was 5.6 ℃ higher than double covered plastic greenhouse throughout the day.The larger difference between the two greenhouses was showed in the nighttime(0:00～7:00 and 17:00～24:00).And the average temperature difference in night was 6.8 ℃.In cloudy day,the average temperature inside novel greenhouse was 5.9 ℃ higher than double tunnel and 7.1 ℃ higher in night while in rainy day the values were 3.6 ℃ and 3.5 ℃ respectively.According to the result,the thermal insulation performance of novel greenhouse was better than double covered plastic greenhouse.