An empirical study on flow boiling heat transfer characteristics of R-134a in a tube with novel inclined grooves
Volume Title: 1
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, I.R.Iran
In the present study, the effects of different geometrical parameters on heat transfer coefficient in a novel grooved-tube during flow boiling of R-134a were investigated experimentally. The vapor quality varies within a range of 0.06 to 0.99, the mass flux varies from 16.5 to 105 kg/m2.s and heat flux varies between 3.5 and 25 kw/m2. The test section was made of copper with internal diameter of 20 mm and thickness of 1 mm. A new type of inclined grooves was created on internal wall surface of the tube. The effects of the angle of grooves with centerline of the tube, pitch to width (P/W) ratio of grooves and number of circumferential grooves in cross section of the tube were investigated in boiling flow, experimentally. The angles of grooves were set to three different values of 15, 30 and 45 degrees, the numbers of grooves were determined 4, 6 and 8, and (P/W) ratios of grooves were considered as 3, 5 and 7. The width of grooves was 2 mm and the groove-pitch length was set to 6, 10 or 14 mm in different cases. The experimental results of the present work reveal that heat transfer coefficient in boiling flow of R-134a increases with groove angles and numbers or by decreasing the groove-pitch length.