Experimental assessment of convective heat transfer and pressure drop correlation of R1234ze(E) for a supercritical heat exchanger in the organic Rankine cycle

Abstract

In the supercritical organic Rankine cycle, the process of absorbing heat from a heat source occurs in the supercritical region. The supercritical heat exchanger, which is responsible for heat exchange between the heat source and working fluid in the supercritical region, is a crucial component of this cycle. In this study, the correlation of the Nusselt number and Darcy’s friction factor was proposed, according to the experimental result of the heat transfer and pressure drop of the supercritical R1234ze(E) for the temperature ranges below and above the pseudo-critical temperature. Correlations of the Nusselt number and Darcy’s friction factor agree with the experimental results within ±20 %. Supercritical heat exchangers were designed and tested using the proposed correlations. The developed supercritical heat exchanger satisfied the condition within a -0.5 % margin of error, based on the heat exchange rate between the design and experimental results.