内置折边扭带管内高湿气体对流凝结换热与流动特性

对高湿气体在内置折边扭带管内对流凝结换热与流动特性进行了实验研究。分析了壁面温度、水蒸气含量、进口温度、气流速度等对高湿气体对流凝结换热的影响,降低壁面温度、提高水蒸气含量对流和凝结换热均提高,但对强化凝结换热尤其明显。引起扭带管内冷凝液膜状态变化的参数有扭曲比y和扭带与管壁间隙b。y越低气流旋转越强,导致液膜加厚而引起传热量降低和流动阻力增加;b较小时液膜积存在扭带端部,不仅降低传热面积而且无气流穿越扭带端部,b较大时旋转气流能穿越扭带端部,减薄管表面液膜厚度,强化凝结换热。

Thermal and hydrodynamic performance of high humidity gas convection-condensation in a tube with edgefold-twisted-tape

Thermal and hydrodynamic performance of high humidity gas convection-condensation in a tube with edgefold-twisted-tape inserts was investigated experimentally, in which the main experimental parameters are wall temperature, vapor content, velocity and inlet temperature of the mixture.It is found that decreasing wall temperature and increasing vapor content enhance both convection and condensation, especially for vapor condensation.Structure parameters, such as the twist ratio and clearance between tube and tape, may change the condition of condensation film in the tube.The results show that higher twist ratio leads to higher swirl flow intensity and thicker condensation film, which decrease the heat transfer and increase the pressure drop.When the clearance between tube and tape is small, the condensation film may remain at the tip of tape and prevent the gas flowing through.When the clearance is large, the gas can flow through the tip of tape easily and the thickness of condensation film is small, so that the heat transfer is intensified.