Abstract:

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.