Authors

Abstract

Effective cooling is crucial for maintaining suitable thermal environments in greenhouses during hot summers. This study developed a coupled numerical model to investigate the cooling performance of a wet curtain system in a multi-span plastic greenhouse in Weifang, China. Relative deviations were less than 5.88% for wet curtain outlet temperature and below 7% for average greenhouse temperature. Results indicated that the wet curtain reduced the average greenhouse temperature by 2.33 ~ 4.20 ℃, with the maximum reduction of 4.20 ℃ occurring at 12:00. The cooling capacity increased with rising solar radiation in the morning and then diminished in the afternoon. The cooled air entered as a floor-level jet, accumulated near the crop zone, and subsequently rose due to buoyancy, forming two large recirculation vortices that enhanced vertical mixing and improved temperature uniformity. Consequently, the average indoor air velocity increased by 8.38% ~ 22.40% compared to ventilation without the wet curtain. Parametric analysis revealed that the average greenhouse temperature decreased nonlinearly with increasing inlet velocity, and the marginal cooling benefit dropped significantly when the inlet velocity exceeded 0.75 m/s. An optimal inlet velocity range of 0.75 ~ 1.0 m/s is recommended. The model accurately captured the thermal performance and airflow patterns of the greenhouse with wet curtain cooling.

Abstract in Chinese

在炎热的夏季，有效的降温对维持温室适宜的热环境至关重要。本研究建立了一个耦合数值模型，用于研究山东潍坊一座连栋塑料温室中湿帘系统的降温性能。湿帘出口温度的相对偏差小于5.88%，温室平均温度的相对偏差小于7%。结果表明，湿帘使温室平均温度降低了2.33～4.20 ℃，其中12:00时降幅最大，达4.20 ℃。上午降温能力随太阳辐射增强而提高，午后则逐渐减弱。冷却后的空气以贴地射流形式进入温室，在作物区附近积聚，随后因浮力作用上升，形成两个大型回流涡，增强了垂直混合，改善了温度均匀性。因此，与无湿帘的通风相比，室内平均风速提高了8.38%～22.40%。参数分析显示，温室平均温度随入口风速的增加呈非线性下降，当入口风速超过0.75 m/s时，边际降温效益显著降低。推荐的最佳入口风速范围为0.75～1.0 m/s。该模型准确捕捉了湿帘降温温室的热工性能和气流流型。