On the Possibility of Enhancing Heat Transfer in a Pipe Flow by Rectangular-Wave Pulsation

Abstract

We investigated how much heat transfer in a pipe can be enhanced by rectangular-wave pulsation generated by opening and closing the valve. The variation of the heat transfer coefficient corresponding to the sudden acceleration and deceleration of the flow was successfully reproduced using the previously derived dimensionless formulae. Thus, it was possible to predict the heat transfer enhancement from Reynolds numbers and periods when opening and closing a valve. The results showed that when pulsating between laminar and turbulent flows, the heat transfer enhancement becomes larger when the average Reynolds number is in the transition regime. In addition, it was shown that the heat transfer is likely to be enhanced when the Reynolds number at the valve open is higher and the opening period is shorter.