A transient experimental method to determine the overall heat transfer coefficient in a concentric tube heat exchanger

Abstract

An experimental method to determine the overall heat transfer coefficient (U) in a concentric tube, parallel flow heat exchanger is presented. This method is based on transient analysis of such a heat exchanger subjected to an arbitrary temperature change at the inlet of one fluid stream. The transient method of measurement of U can be used for a speedy determination of the thermal performance of a smooth or augmented heat exchanger tube in comparison to a traditional steady-state method. Application of the transient method to a tubular heat exchanger with smooth inner tube is presented. The Nusselt number (Nu) and friction factor (f) obtained for the smooth inner tube over a range of Reynolds number (Re=12,000 - 50,000) are each within ± 5% of Gnielinski's and Filonenko's correlation respectively.