DYNAMICS OF HEAT TRANSFER WITH PULSATILE " FLOW IN A CIRCULAR TUBE

Abstract

Experimental investigation on the dynamics of heat transfer, under constant wall temperature condition, in pulsatile flow of a Newtonian fluid (water) in a circular tube is presented in the present work. Sinusoidal perturba-tions in the fluid Evelocity were superimposed by means of a mechanical pulsation generator. Experiments were conducted with mean flow Reynolds number ranging from 1000' to 25000. Three different pulsation frequencies were used and these were 0.1, 0.5 and 1.0 Hz. Velocity amplitude varied from 0 to 1.0 in steps of 0.2. Time average heat transfer rate and overall heat trans-fer coefficient were calculated on the basis of time average velocity and time average tenperature Enhancement factors both for the heat transfer rate and the overall heat transfer coefficient were also calculated on the above basis. Experimental results show superimposed pulsations enhance heat transfer. The enhanCement is influenced strongly by the velocity amplitude and over the range of parameters studied increases with the increase in velocity amplitude. The effect of mean flow Reynolds number and pulsation frequency are relati- vely snail. Over the range of frequency studied, quasi-steady state hypothesis to describe the pulsating heat transfer is found not to te applicable. However, the results are explained qualitati-vely with the help of wall layer oscillations.