Heat Transfer Enhancement in Horizontal, Spirally Grooved Evaporator Tubes

抄録

Experimental data of the circumferentially local heat transfer coefficient as well as the circumferentially averaged coefficient were obtained for R-22 and R-12 flowing at mass velocities of 50 to 500 kg/(m²·s), in three types of spirally grooved evaporator tubes oriented horizontally. The heat transfer in the grooved tubes was found to be effectively enhanced over a smooth tube at mass velocities lower than 100kg/(m²·s), but, as the mass velocity increased, the enhancements were rapidly reduced, and then the heat transfer coefficients gradually approached the value in a smooth tube, a simplified model, which took account of the heat transfer through the meniscus liquid film in the grooves, was developed, and thereby the heat transfer characteristics in the grooved tube were explained.