Experimental Study on Heat Transfer and Fluid Flow in Vertical Rifled
In this paper, heat transfer and fluid flow monitoring experiments for pressure drop and efficiency were performed to investigate the fluid flow characteristics of rifled tubes in comparison with a smooth tube. The rifled tube has an outer diameter of 25mm, maximum inner diameter of 18.8 mm; minimum inner diameter of 17.50mm, rib height of 0.6835, rib width of 9.25, helix angles 60 o and the number of starts is four. The smooth tube has an outer diameter of 26.7mm and an inner diameter of 18.88 mm, with a wall thickness of 3.91mm. The experiments were conducted on a vertical orientation of the steel tubes (rifled and smooth) under varying flow rate of 15, 30, 40, 50, 60 and 70. The fluid used is 131.64 litres of water and the initial temperature is 25oC. The fluid is raised to an average temperature of 33oC during the experimental study. During the experiment, it was found that at 360 mins for the smooth tube, an increase in flow rate does not affect the time for the fluid (water) to attain a temperature of 33oC. For the rifled tube, as the flow rate increases, the time for the fluid (water) to attain a temperature of 33oC also increases. This is as a result of the effect of ribbing the tube. The time taken to attain the optimum temperature of 33oC is shorter using the rifled tube than the smooth tube. The rifled tube has heat transfer efficiency higher than the smooth tube. The pressure drop and the energy consumed by using the rifled tube were also found to be less than that of the smooth tube. The pressure drop increase factor was found to be 0.85 in the spirally rifled tube as compared to the smooth tube at the different flow rates. The enhancement effect of ribbing the tube is apparent.