摘要
通过建立封闭空气腔二维稳态流动传热模型和温室墙体一维非稳态导热模型,模拟计算封闭腔内空气温度分布,研究了日光温室墙体中覆铝箔封闭空气腔的热工性能。结果表明:壁面覆铝箔可有效减少封闭空气腔的辐射换热量;封闭空气腔的热阻随封闭腔高度的增加而增大,高度达1.5 m后,热阻趋于不变;封闭空气腔的厚度小于0.03 m时,其热阻随厚度增加而增大,厚度超过0.03 m后,热阻逐渐减小;覆铝箔封闭空气腔高度为1.5 m、厚度为0.03 m、内外壁面温差为2~20 K时,热阻为0.70~0.55 K·m^2/W,保温隔热效果相当于0.81~0.64 m厚夯实黏土结构、0.55~0.43 m厚红砖砌体结构墙体或0.20~0.16 m厚煤渣、0.06~0.05 m厚珍珠岩、0.03~0.02 m厚聚苯板隔热材料。3组30 mm厚覆铝箔封闭空气腔加480 mm红砖复合墙体(360 mm红砖墙+3组30 mm封闭空气腔+120 mm红砖墙,240 mm红砖墙+3组30 mm封闭空气腔+240 mm红砖墙),其夜间向室内放热量较单一480 mm红砖墙体提高99.5%~104.2%,与相同结构聚苯板红砖复合墙体无明显差距。
According to building structure and temperature variation of solar greenhouse wall, a two-dimensional steady flow and heat transfer model and a one-dimensional unsteady heat conduction model were established for simulation and study on the thermal performance of an air enclosure covered with aluminum foil, to explore suitable structure of the air enclosure in solar greenhouse wall insulation design. The results revealed that the wall surface covered with aluminum foil could effectively reduce radiation heat in the air enclosure; thermal resistance in the air enclosure increased with the rise of the enclosure height, and when the height reached 1.5 m, thermal resistance tended to be the same; when the enclosure thickness was less than 0.03 m, the air inside enclosure was in the stationary state, with heat conduction and thermal radiation as main heat transfer way, thermal resistance increased with the increasing thickness; when the thickness was more than 0.03 m, air natural connection in the enclosure was enhanced continuously, so convective heat transfer gradually replaced heat conduction, thermal resistance decreased with the increasing thickness. In wall insulation design of solar greenhouse, the suitable height and thickness of air enclosure covered with aluminum foil were 1.5 m and 0.03 m respectively. When temperature difference between inside and outside surface of the enclosure was 2-10 K in the simulation of heat preservation layer, average thermal conductivity was 0.047 W/（m· K）, and thermal resistance was 0.70-0.58 K·m^2/W in the air enclosure, heat preservation and heat insulation effect was equivalent to 0.81-0.67 m thickness of solid clay wall, or 0.55-0.45 m thickness of red brick wall, or 0.20-0.17 m thickness of coal cinder, or 0.06-0.05 m thickness of pearlite, or 0.03-0.025 m thickness of polystyrene board; When temperature difference was 10-20 K in the simulation of thermal conductivity layer, average thermal conductivity was 0.052 W/（m·K）, and thermal resistance was 0.60-0.55 K·m^2/W in the air enclosure, heat preservation and heat insulation effect was equivalent to 0.70-0.64 m thickness of solid clay wall, or 0.47-0.43 m thickness of red brick wall, or 0.17-0.16 m thickness of coal cinder, or 0.06-0.05 m thickness of pearlite, or 0.025-0.02 m thickness of polystyrene board. There are two types of solar greenhouse wall structures： 360 mm thickness of red brick wall ＋ three 30 mm air enclosures covered with aluminum foil ＋120 mm thickness of red brick wall, 240 mm thickness of red brick wall ＋ three 30 mm air enclosures covered with aluminum foil ＋240 mm thickness of red brick wall. The heat released to inside greenhouse form the two walls greatly increased than 480 mm thickness of red brick wall, but was not significantly different from the wall of the same structure composed by red brick wall and polystyrene board. Polystyrene board can be replaced with enclosure of this suitable structure in solar greenhouse wall design.
作者
张潇丹
颉建明
郁继华
吕剑
Zhang Xiaodan Xie Jianming Yu Jihua Lu Jian(College of Horticulture, Gansu Agricultural University, Lanzhou 730070, Chin)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2017年第2期227-233,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家公益性行业(农业)专项资助(201203002)
关键词
墙体
温度
对流换热
日光温室
封闭空气腔
平均导热系数
热阻
walls
temperature
heat convection
solar greenhouse
air enclosure
average thermal conductivity
thermal resistance
