EXPERIMENTAL INVESTIGATION OF DOUBLE-PIPE HEAT EXCHANGER WITH HELICAL FINS ON THE INNER ROTATING TUBE

Abstract

Heat exchanger is an important device in all the thermal systems. The heat exchanger is widely used equipment in different industries such as process, petroleum refining, chemicals and paper etc. Energy and material saving considerations as well as environmental challenges in the industry have stimulated the demand for high efficiency heat exchanger. To improve the efficiency of heat exchanger one must think of heat transfer enhancement in heat exchanger. Moreover heat transfer enhancement enables the size of heat exchanger to be considerably decreased. A high rate of heat transfer with minimum space requirement is necessity for compact heat exchanger. In present work, to improve the heat transfer characteristic of the double pipe heat exchanger, the helical fins were installed on the outer surface of the inner tube and the level of turbulence increased by the rotating the inner tube. The length of heat exchanger was 1m and the pitch of helical fins kept constant equal to 17 mm. The convective heat transfer coefficients were obtained for the stationary as well as rotating inner tube for the counter flow mode using water as cold fluid in the tube side and glycerol as hot fluid in the shell side. The flow rate of cold fluid was kept constant and that of hot fluid was varied. The Nusselt number was calculated for the each speed of the rotation and compared with standard values obtained from Dittus-Boelter equation. The helical fins increases heat transfer area and rotation of the inner tube increases the mixing of fluid particles which is necessary for the convection mode of heat transfer. The Nusselt number increased up to 64 % at 100 rpm compared to stationary inner tube with helical fins.