Investigation of thermohydraulic characteristics of a novel triple concentric pipe minichannel heat exchanger

Abstract

In this paper, a novel triple concentric pipe minichannel heat exchanger (TCPMHE) is presented and built, which is a combination of concentric pipe heat exchanger and minichannel heat transfer technology. A range of experimental investigations are further systematically performed by varying the volume flow rate of hot water (Vh), inner annulus size (Si) and hot fluid inlet temperature (th, i) to evaluate the heat transfer and flow characteristics of TCPMHE. And the results are comprehensively compared with the double concentric pipe minichannel heat exchanger (DCPMHE), aiming to offer some references for the concentric pipe heat exchanger and minichannel heat transfer technology in further industry application. Results indicate that the friction factor (f) values for both DCPMHE and TCPMHE are almost equal under the same operating conditions. Although the Nusselt number (Nu) values of DCPMHE are 21.8%-50.7% higher than those of TCPMHE, the effectiveness (ε) values of TCPMHE are all much higher than those of DCPMHE under the same conditions, and the enhancing factor (η) ranges from 1.45 to 1.65. Compared with the DCPMHE, the volumetric heat transfer capacity of the TCPMHE is improved by up to 65.4% at Si = 0.5 mm, th,i = 60 ℃ and Vh = 209 L·h−1. In addition, the dimensionless correlations for inner annulus hot fluid Nu, ε, and f of TCPMHE were established, and the maximum deviations are ± 8%, ± 5% and ± 11% for Nu, f, and ε, respectively, which indicates that the predicted values from the correlations agree well with the measured results.