Experimental characterization of a double tube heat exchanger with inserted twisted tape elements

Abstract The aim of this paper was to study the influence on thermo-hydraulic performance of different configurations of regularly spaced twisted tape elements (TTEs) inserted into a smooth double tube heat exchanger (DTHX). In order to emulate the behavior of high-viscosity food-industry fluids, a 60° brix solution of water and sugar was used as the Heat Transfer Fluid (HTF). A total of 320 experimental tests were carried out, varying the flow velocity (Reynolds number) and the TTE configuration. We report the results from nine different configurations, including different twisted tape element pitches and free-space lengths. Finally, the results from each case were correlated for Nusselt number and friction factor using the minimum variance methodology. The agreement between the results obtained from the experimental data and those obtained from the proposed correlations is reasonable, with an absolute average relative derivation of less than 9.5% for the heat transfer rate and 15% for the friction factor.