为合理确定墙体蓄热层厚度,该研究提出了蓄热层确定方法,并利用土墙(顶宽2.0 m、底宽5.3 m)在晴天的温度变化对该方法进行了检验。根据墙体保温蓄热特性,其蓄热层可认为是:1)室内侧墙体在白天结束(保温被闭合)时刻与白天起始(保温被揭开)或夜间结束(次日保温被揭开)时刻温度之差大于1℃的区域(该方法简称为“温差法”);或2)室内侧墙体一天内温度波幅大于1℃的区域(该方法简称为“温波法”)。根据温差法和温波法所确定的土墙蓄热层厚度分别为30和40 cm。考虑到墙体对温度波的相位滞后作用,根据温差法所获得的结果偏小。最后,该研究基于一维差分法提出了蓄热层厚度计算模型,计算得到土墙蓄热层厚度为38.5 cm,与试验结果一致。
A wall of the Chinese solar greenhouse (hereafter referred as “solar greenhouse”) included the heat storage layer, heat insulation layer and heat preservation layer. The heat storage layer was part of the wall exposed to the indoor environment of solar greenhouse and mainly used to store and release heat during daytime and night time, respectively. The objective of this study was to develop methods to identify the heat storage layer of solar greenhouse wall and then estimate its width. An earth wall with the top and bottom widths of 2.0 and 5.3 m was used. Firstly, it was proposed that the heat storage layer of wall was identified as: 1) The indoor part of the wall, of which the temperature at the end of daytime was 1℃ higher than that at the start of daytime or at the end of night time; or, 2) The indoor part of the wall, of which the temperature fluctuation was over 1℃ during a day. Based on the measured earth wall temperature in a sunny day, the earth wall temperature at the end of daytime was higher than those at the start of daytime and at the end of night time. But with the increase in depth of earth wall, the wall temperature at the end of daytime got close to those at the start of daytime and at the end of night time. At the earth wall depth of 30 cm, the wall temperature at the end of daytime was only 1.0 and 0.4℃ higher than those at the start of daytime and at the end of night time, respectively. According to the first method, the width of heat storage layer was estimated as 30 cm. On the other hand, the temperature fluctuation of the wall decreased with the increase in the wall depth as well. The temperature fluctuation at the earth wall depth of 30 and 40 cm were 3.3 and 0.9℃, respectively. Based on the second method, the width ofheat storage layer was estimated as 40 cm. It was noticed that the maximum temperature at the earth wall depth of 30 cm appeared during the period from 20:00 to 23:00. It was 1.4℃ higher than that at the start of daytime. The results indicated tha