Heat Transfer Enhancement of Two-Phase Flow with Turbulent Promoters

Abstract

This study investigates the enhancement of two-phase heat transfer in refrigeration system using turbulent promoters, specifically twisted tape and perforated twisted tapes. The heat transfer enhancement with respect to vapor quality during the flow boiling of R-407C is investigated using twisted tape inserts in a horizontal tubular evaporator with an inner diameter of 13.40 mm and a length of 2 meters. This study looks at how things work when the heat flux is between 3 and 9 kW/m², the mass flux is between 120 and 280 kg/m²·s, and the working pressures are 3, 5, and 7 bar. The void fraction of the air ranges from 0.05 to 0.95. The data show that as the quality of the gas improves, the heat transfer coefficient also improves, especially at higher pressures. The performance of heat transfer is greatly improved when twisted tape pieces are used, especially in areas with lower air quality. The average improvement in heat transfer seen with twisted tapes was between 35% and 60%. At 7 bar pressure, the best performance was seen. When you compare twisted tape to perforated twisted tape, you can see that twisted tape inserts improve heat transfer the most, which makes them perfect for evaporative cooling uses. The study comes to the conclusion that twisted tape pieces are especially helpful for improving heat transfer when the air quality and pressure are higher.