空气流速对温室地下蓄热系统加温时热湿传递的影响

Effects of Air Velocity in Heat Exchanging Pipes to Heat Exchanging and Water Vapor Transformation of Underground Heat Storage System in Greenhouse during Heating

为确定温室地下蓄热系统换热管道空气流速对其加温运行时热量交换和水蒸气迁移的影响,测试了该系统以不同换热管道空气流速蓄热后,夜间加温时换热管道进出口空气温度与湿度、地坪温度、室外温度,计算了换热管道进出口处空气的含湿量、焓、蓄热功率。结果表明,在冬季晴朗的天气下,系统以0.6、1.0、1.5、2.0、2.5、2.8 m/s的换热管道空气流速白昼蓄热后,夜间以与蓄热时相同的空气流速加温时,温室内低温高湿空气流经换热管道后,温度、焓显著增加,相对湿度明显降低,加温功率随换热管道流速增加而增加,平均加温功率分别达1.0、1.6、3.2、6.4、7.2、7.7 kW;当换热管道空气流速小于2 m/s时,加温效果不显著;当换热管道空气流速大于2.5 m/s时持续加温能力差;在满足作物夜间生长所需温度条件时,应以2.0 m/s的换热管道空气流速加温。

Effects of the air velocity in heat exchanging pipes on heat exchanging and water vapor transformation was studied in double-film covering greenhouse during heating at night in winter. The temperature and humidity in inlet and outlet of heat exchanging pipes, floor temperature in heat storage greenhouse and outside temperature were measured at different air velocities in the heat exchanging pipes. The humidity ratio, enthalpy of inlet and outlet of heat exchanging pipes and the power for heating were computed. The results showed that the temperature and enthalpy of cold air with high humidity flowing through heat exchanging pipes increased apparently and the humidity reduced when the air velocities in heat exchanging pipes were respectively 0.6 m/s, 1.0 m/s, 1.5 m/s, 2.0 m/s, 2.5 m/s and 2.8 m/s during heating at night after heat saving in clear days. The power for heating was enhanced with the increase of the air velocity in heat exchanging pipes. The average power for heating is 1.0 kW, 1.6 kW, 3.2 kW, 6.4 kW, 7.2 kW and 7.7 kW respectively. The heating effects is not distinct when the air velocity in heat exchanging pipes is less than 2 m/s, while the continuity for heating is poor when the air velocity in heat exchanging pipes is higher than 2.5 m/s. Therefore the rational air velocity in heat exchanging pipes is 2.0 m/s for heating at night when the temperature satisfies the growing requirements of the crops.