Experimental study of heat transfer and pressure drop analysis of the air/water two-phase flow in a double tube heat exchanger equipped with dual twisted tape turbulator: Simultaneous usage of active and passive methods

Abstract

In this paper, simultaneous use of active and passive methods for enhancing the thermal performance of a double-tube heat exchanger was investigated. This was done by injecting air bubbles into the working fluid and utilizing a dual twisted tape turbulator. Effects of these two procedures on the Nusselt number and pressure drop were evaluated when applied simultaneously. We further studied the effect of cold water flow rate on thermal parameter. The results indicated that the Nusslte number increases with the decrease of turbulator ratio and increases with the increase of bubble injection flow rate, cold water flow rate and the Reynolds number. The findings further showed that the simultaneous use of the two methods could increase the Nusselt number by 98–114%, 3–14%, and 20–39% compared to the cases with a simple tube heat exchanger, a turbulator-equipped heat exchanger (without bubble injection), and a heat exchanger with bubble injection (without turbulator), respectively.