Enhancement of Heat Transfer in a Rouletted Copper Tube Employing Delta Winglet Twirled Type Insert

Abstract

Heat transfer is a process or a system of thermal engineering that concerns the generation, use, conversion, transfer, internal or external molecular formation and exchange of thermal energy (heat) between physical systems. The research work has been experimented for the turbulent flow heat transfer in a tube having delta winglet twisted tape and then separately with water as working fluid. The test section consisted of a circular copper tube of 26.6 mm inner diameter, 900 mm length with five K-type thermocouples. Bulk temperature and pressure drops have been measured. Material of both the delta winglet twisted tape insert was stainless steel. Delta winglet twisted tape insert had a length of 795mm, width of 20mm, thickness of 2mm, pitch length of 120mm, twist ratio of 6 while wire coil insert had the same length as that of delta winglet twisted tape insert, wire diameter of 1mm, mean coil diameter of 22mm and pitch length of 30mm. Heat transfer rate, convective heat transfer coefficient, Nusselt’s number, friction factor and heat transfer efficiency have been calculated to analyze heat transfer performance of circular copper tube fitted with or without inserts in turbulent regimes (4000<Re<15000). Nusselt’s numbers for combination of delta winglet twisted tape and wire coil insert, wire coil insert only, delta winglet twisted tape insert only increased by 1.29 to 1.47, 1.19 to 1.34 and 1.10 to 1.15 times respectively than the plain tube. They increased by 17.95% to 27.61%, 15.97% to 20.20%, 8.90% to 12.02% and average of 21.65%, 17.44%, 8.95% respectively than the plain tube. Heat transfer rates also increased by 1.12 to 1.20, 1.06 to 1.09 and 1.03 to 1.05 times respectively compared to the plain tube. Heat transfer efficiencies increased by 1.36% to 1.62%, 1.24% to 1.47% and 1.14% to 1.34% respectively compared to the plain tube. Friction factors increased by 1.44 to 1.62, 1.34 to 1.43, 1.22 to 1.27 times respectively compared to the plain tube. The delta winglet twisted tape was the best arrangement for the enhancement of heat transfer rate as compared to the other inserts.