Enhancement in heat transfer when fluid is injected tangentially has been experimentally studied. The experiments were conducted on electrically heated tubes with different diameters and air as the test fluid. The effects of tube diameter, injector diameter, momentum flux ratio, and Reynolds number have been studied parametrically. The results show that with tangentially injection, significant enhancement in heat transfer is possible. The enhancement is strongly dependent on the ratio of the rates of tangential and total momentum fluxes but is weakly dependent on Reynolds number. The tube diameter and the number of injectors do not affect the heat transfer enhancement. with an optimum design of the injectors, as much as 35% to 40% enhancement on a constant pumping power basis has been obtained.

KEYWORDS: heat flow, heat transfer fluids, heat transfer coefficient, injectors, Reynolds numbers, performance, friction factor, optimisation, diameter