Experimental study of effects of baffle helix angle on shell-side performance of shell-and-tube heat exchangers with discontinuous helical baffles

Flow resistance and heat transfer of several shell-and-tube heat exchangers with discontinuous helical baffles are experimentally studied and compared at the five helix angles of 8°, 12°, 20°, 30° and 40°. The second-law based thermodynamic analysis is employed to analyze the effects of baffle helix angle on the irreversible loss of heat exchangers. The results indicate that the shell-side pressure drop and heat transfer coefficient of the heat exchanger with smaller helix angle are higher than those with larger helix angle at a given shell-side volume flow rate. However, in the condition of the same shell-side Reynolds number, the flow resistance with larger helix angle is lower and the heat transfer performance is better. The heat exchanger with helical baffles at 40° helix angle presents the best comprehensive performance among the five testing heat exchangers. In the second-law thermodynamic comparisons, the irreversibility of heat exchanger is estimated by the theories of entropy generation and entransy dissipation. Experimental analysis shows that in the same heat transfer area and under the same working conditions, the shell-and-tube heat exchanger with smaller helix angle baffles produces less irreversibility in the heat exchange process. In addition, the heat exchangers with helical baffles are more effective under certain conditions of low shell-side Reynolds number.