THERMAL-ANALYSIS OF THE PERFORMANCES OF HELICAL-TYPE, ROUGHENED, DOUBLE-PIPE HEAT-EXCHANGERS

Parallel-type heat exchangers with artificially roughened elements on the outer surface of the inner tube were designed to investigate the effect of augmentation heat transfer on this kind of heat exchanger. The objective is to evaluate the possibility of replacing classical heat exchangers with the aim of improving heat transfer performance and material cost reduction. The Nusselt numbers for water flows with a helical angle alpha equals 65 degree , a pitch-to-height ratio p/e equals 1. 45, and two aspect ratios (shellside diameter to tubeside diameter) of D//0/D//i equals 2. 68 and 5. 1 are obtained and a comparison of these results with those for a smooth tube at the same aspect ratios is also discused.