Experimental studies on heat transfer augmentation for flow of liquid through circular tubes using twisted gi wires with and without baffles as insert

Abstract

This project deals with the use of twisted GI wires as passive heat transfer augmentation device. Effect of twisted GI wires without baffles and with baffles, with varying baffle spacing, was studied experimentally in a double pipe heat exchanger. Effect of insert with three different baffle spacing (24cm, 12cm, 6cm) were studied. The effect of turbulence created by twisted wires & baffles on Nusselt number was compared with that of smooth tube. Based on constant flow rate, the nusselt numbers were found to be 1.23-1.42, 1.32-1.5 &1.49-1.65 times the smooth tube values for baffle spacing of 24cm, 12cm and 6cm respectively. Based on increase in nusselt number and performance evaluation of inserts with different baffle spacing, it was concluded that insert with baffle spacing 6cm performs much better than the inserts with baffle spacing 12cm or 24cm or without baffles. Continuous research is going on to improve its effectiveness by increasing fluid turbulence, generating secondary flow patterns, reducing the thermal resistance and increasing the heat transfer surface area.