外保温连栋温室光热环境及保温性能分析

Analyzing light and thermal environment and insulation performance of a multi-span greenhouse with external insulation

为解决中国北方地区连栋温室冬季加温能耗大、盈利性和可持续性差等问题,该研究以降低屋面热损失为出发点,设计了大屋面外保温连栋温室,将外保温系统创新应用于连栋温室,并在山东寿光地区,以文洛型连栋温室为参照,对该温室光热环境及保温性能进行试验测试与分析。结果表明:1)连续40d白天(10:00—16:00),外保温连栋温室作物冠层上方平均太阳辐射为152 W/m^(2),总透光率(含天沟下方)为40%,比文洛型连栋温室高7个百分点。外保温连栋温室跨中采光最佳,跨东、跨西及天沟下方太阳辐射强度与跨中相比分别减少17%、29%及46%。2)太阳升起后,外保温连栋温室东、西屋面外保温被依次收拢,09:30—12:00室内气温升速为1.9℃/h,较文洛型连栋温室低0.3℃/h,收拢保温后10min内室内气温骤降幅度比文洛型连栋温室低0.3℃。温室采用空气内循环加温,地面出风,再由设备间风机组内侧窗回风;加温期间(20:00—07:00)室内空气水平方向平均温差不超过1.2℃,垂直方向不超过1.0℃。外保温连栋温室水平方向气温分布均匀,垂直方向温差小于文洛型连栋温室。3)夜间,外保温连栋温室平均气温为13.1~16.1℃,室内外平均温差为12.8~21.0℃,覆盖外保温被的屋面平均热通量为50.0~97.7W/m^(2),单层玻璃屋面为217.6~367.9 W/m^(2),覆盖外保温可减少75%的玻璃屋面热损失。同期,采用双层内保温的文洛型连栋温室屋面平均热通量为141.1~232.2 W/m^(2),外保温连栋温室与之相比屋面热损失降低36%,具有更佳的保温性能。加温期间外保温连栋温室平均热量投入实测为74.5W/m^(2),并维持17.4℃的室内外平均温差,能耗较低。最后拟合了室内外温差对不同温室屋面热通量的影响,外保温连栋温室具有更高的拟合优度。该研究为连栋温室低碳节能发展提供了新型温室结构,也为外保温连栋温室的优化设计和工程应用提供了数据基础。

Large-scale greenhouse can be expected to serve as the future direction in the horticulture industry.However,the multi-span greenhouses can consume a large amount of energy for heating in winter in northern China,resulting in low profitability and sustainability.In this study,a multi-span greenhouse was designed with large roofs and external insulation,in order to reduce the heat loss of the greenhouse roof.The external insulation system was innovatively applied to the multi-span greenhouse.The greenhouse design was expected to improve thermal insulation performance and reduce heating energy consumption.A field test was carried out in Shouguang,Shandong Province,China.Taking the Venlo-type multi-span greenhouse in the same area as a reference,a systematic investigation was made on the light and thermal environment,thermal insulation performance of the multi-span greenhouse with external insulation.The experimental data were analyzed from continuous 40 winter days.The results show that:1)The average solar radiation was 152 W/m^(2) above the crop canopy inside the tested greenhouse during the day(10:00-16:00),and the total light transmittance was 40%,which was 7 percentage points higher than that of Venlo type multi-span greenhouse.The best daylighting was found in the middle of the greenhouse span,due to the influence of the gutter.The solar radiation intensity at the east and west of the greenhouse span and under the gutter was reduced by 17%,29%,and 46%,respectively,compared with the middle.2)There was the folded in turn for the external thermal blankets covering the east and west greenhouse roofs after the sun rose.Specifically,the indoor air temperature rose at 1.9/h from 09:30 to℃12:00,which was 0.3/h slower than that of the Venlo℃-type one.However,the sudden drop in the air temperature of the multi-span greenhouse with the external insulation was reduced by 0.3 within 10 min after folding insulation℃devices.The tested greenhouse was heated by the internal air circulation,with the air coming out from the ground and then returning to the equipment room through the inner side windows.During the heating period(20:00-07:00),the average temperature difference of indoor air in the horizontal direction did not exceed 1.2,without exceeding 1.0℃℃in the vertical direction.The uniform distribution was observed in the horizontal temperature of the multi-span greenhouse with the external insulation.The vertical temperature difference was smaller than that of the Venlo-type one.3)The average air temperature at nighttime inside the multi-span greenhouse with external insulation ranged from 13.1 to 16.1,and the average temperature difference between indoor and outdoor air was 12.8℃-21.0.The average heat℃flux of the glass roof that was covered with the external thermal blanket was 50.0-97.7 W/m^(2),while the single-layer glass roof was 217.6-367.9 W/m^(2).The greenhouse covering with the external thermal blanket was reduced by 75%in the heat loss of the glass greenhouse roof.At the same time,the average heat flux was 141.1-232.2 W/m^(2) in the Venlo-type one with double-layer indoor thermal screens in use.The roof heat loss of the multi-span greenhouse with the external insulation was reduced by 36%,indicating a better insulation performance.The mean heat energy input of the multi-span greenhouse with external insulation was measured to be 74.5 W/m^(2) during the heating period,maintaining an average temperature difference between indoor and outdoor air of 17.4.Thus,the℃energy consumption of heating the multi-span greenhouse with the external insulation was low.Finally,the fitted influence of indoor and outdoor air temperature differences on the heat fluxes of greenhouse roofs was presented,and the tested greenhouse showed better goodness of fitting.This finding can provide a new type of greenhouse structure for the low-carbon and energy-saving production of multi-span greenhouses.A data basis can also be offered for the optimal design and engineering application of the multi-span greenhouse with external insulation.