固化沙蓄热后墙日光温室热工性能试验

结合西北非耕地地区多沙的特点,在因地制宜、就地取材的基础上,该课题组设计了1种以多孔砖和固化沙为后墙结构主要材料的新型复合墙体日光温室。该日光温室有被动蓄热后墙和主动蓄热后墙2种类型,被动蓄热后墙以固化沙为主要蓄热体,主动蓄热后墙在被动蓄热墙体的基础上增设了蓄热循环系统。通过在内蒙古乌海地区进行试验,分析其热工性能,并与当地普通砖墙日光温室性能进行比较分析。试验结果表明,晴天条件下,固化沙被动蓄热后墙温室、固化沙主动蓄热后墙温室、普通砖墙温室的夜间平均气温分别为13.7、17.0、12.8℃。阴天条件下,3座温室的夜间平均气温分别为10.6、13.8、10.0℃。固化沙被动蓄热后墙温室墙体内部恒定温度区域处于500~740 mm之间,蓄热体厚度近500 mm,其中固化沙蓄热体厚度近380 mm。固化沙主动蓄热后墙温室的墙体内部恒定温度区域处于740~1 000 mm之间,蓄热体厚度超过740 mm,其中固化沙蓄热厚度超过620 mm。综上,固化沙主动蓄热后墙日光温室的热工性能明显优于固化沙被动蓄热后墙日光温室及当地普通砖墙日光温室,可满足喜温作物的越冬生产,在西北多沙地区具有一定的实用推广价值。

Thermal performance test of solidified sand heat storage wall in Chinese solar greenhouse

Solar greenhouse has been widely used in the north of China. Chinese solar greenhouse is made of north wall, east wall, west wall, front roof, back roof and heat preservation quilt. The main materials of north wall in traditional Chinese solar greenhouses are soil and brick. However, in the northwest of China, there are many non-cultivated lands with many sands instead of soil resources. In this research, we designed a new kind of north wall (W1) which was made of 2 layers of porous bricks and contained the solidified sands. The solidified sand was in the middle of W1 and the porous bricks were at the outside layers of the solidified sands. The wall thickness was 1000 mm, with 760 mm thick solidified sands and 240 mm thick porous bricks. In order to store more heat into the wall, a new active storage wall (W2) was also developed based on the W1. Compared with the W1, a sand-air heat transfer system was added with 2 axial flow fans and 3-layer air passages, and the air conduits were 80 m long, which was developed to store more heat. The thermal environmental properties of the 2 newly designed greenhouse walls were evaluated in Wuhai (39°39′N, 106°47′E), Inner Mongolia Autonomous Region, China, which were also compared with the local solar greenhouses with porous bricks and EPS (W3). During clear days (for instance, from 9:00 on January 7th, 2016 to the next 9:00), the average daily air temperature in W1, W2, and W3 was 17.2, 20.5 and 16.9℃, respectively with an average outside temperature of -11.3℃. The average night air temperature in W1, W2, and W3 was 13.7, 17.0 and 12.8℃, respectively, indicating that W2 had the best heat storage ability. During cloudy days (for instance, from 9:00 on January 16th, 2016 to the next 9:00), the average night air temperature in W1, W2, and W3 was 10.6, 13.8 and 10.0℃, respectively, indicating that W2 also had the best heat storage ability. In order to have a better understanding of the thermal properties of the 3 greenhouse walls, we selected the indoor temperature data of consecutive 27 days from January 1st to January 27th, 2016. During this period, the minimum average air temperature in W1, W2 and W3 was 10.48, 10.51 and 9.57℃, respectively. The daily average air temperature was 14.97, 17.30 and 14.89℃. Solar greenhouse wall was an important factor for maintaining greenhouse heat balance. Wall heat storage ability was important for the greenhouse performances. The distributions and changes of temperature inside the wall reflected the heat exchange process between the wall and indoor air and had great impacts on the indoor temperature in greenhouses. The internal constant temperature region of the wall W1 was between 500 and 740 mm, and the thickness of the thermal storage body was about 500 mm. For the solidified sand body, the effective thermal storage thickness was up to 380 mm. For the W2, the internal constant temperature region ranged from 740 to 1000 mm, and the effective thermal storage body thickness exceeded 740 mm, among which, the effective thermal storage body thickness of the solidified soil exceeded 620 mm. For the W3, the effective thermal storage body thickness and temperature fluctuations were relatively smaller and the thermal storage capacity was also the smallest. Under sunny days, for the W2, the effective thermal storage body included the 500 mm thick wall body and the inside of the air tubes and their outside up to 200 mm, indicating that active heat storage fan system could significantly improve the wall heat storage capacities in greenhouses. Our results indicate that the new designed greenhouse wall W2 has some important application values.