An experimental study on the effects of different geometrical parameters on flow boiling pressure drop in a novel grooved tube

All methods for enhancing the heat transfer are accompanied by pressure drop increment penalty. In the present research, the effects of different geometrical parameters on frictional pressure drop in a novel grooved-tube under flow boiling of R-134a were investigated experimentally. The mass flux varies from 16.5 to 105 kg/m2s, the vapor quality varies within a range of 0.06 to 0.99, and heat flux varies between 3.5 and 25 kW/m2. The test sections were the tubes with internal diameter of 20 mm made of copper sheets with thickness of 1 mm. A new type of inclined grooves was created on internal wall surface of the tubes. 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. The angles of grooves were set to three different values; 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 results of the present work reveal that frictional pressure drop increases with groove angles and numbers or by decreasing the groove-pitch length. Finally, an empirical correlation for frictional pressure drop of boiling flow in this type of grooved tube was developed using the present experimental work.

کلیدواژه ها:

Boiling ، Grooved tube ، Pressure drop ، Correlation ، R-134a.