Evaporation heat transfer and Pressure loss in micro-fin tubes and a smooth tube

마이크로핀관과 평활관에서의 증발열전달과 압력손실 특성

Evaporation heat transfer coefficient and pressure loss were measured for three different micro-fin tubes and a smooth tube. The experiments were carried out with R-22 over a wide range of vapor Quality, mass velocity and heat flux. Heat transfer coefficient of the tube with slightly modified fin shape was found to be higher than that of the commercial reference tube by 60%. The improvement of heat transfer has been achieved without noticeable increase of pressure loss. Heat transfer coefficient was increased with increasing quality, refrigerant mass flux, and heat flux. However, the effect of refrigerant mass flux and heat flux was not great. Heat transfer coefficient at bottom was lower than that at top of the tube in low quality region, which suggested the existence of stratification in the micro-fin tube. Pressure drop was linearly increased with increasing refrigerant quality and was proportional to about square of mass flux.