Experimental investigation of pressure drop and heat transfer in high temperature supercritical CO2 and helium in a printed-circuit heat exchanger

Abstract

An ASME code compliant heat exchanger was manufactured for testing between high-temperature (up to 550 °C) helium and supercritical CO2 test facilities at Georgia Institute of Technology. The multi-layerd printed-circuit heat exchanger (PCHE) consists of 17 photo-chemically etched plates which were diffusion-bonded together. Pressure losses and heat transfer measurements have been conducted for a zig-zag flow-path geometry etched into the bonded shims. These measurements have been presented in dimensionless form to facilitate comparison with thermohydraulic correlations available in the literature. The use of two fluids with drastically different properties in the same 37° zig-zag channel geometry provides a unique method of exploring the effect of working fluid on PCHE performance. Fanning friction factor and Nusselt numbers are determined for supercritical CO2 between Reynolds number of 500–18,000, spanning laminar, transition, and turbulent regimes. The same friction and heat transfer figures of merit are presented for helium operating between Reynolds number 400–3200, spanning laminar and transition turbulent regimes. Two different exponential models were fitted to the supercritical CO2 and helium friction data showing an agreement with the measurements to within ±10% over the range of test conditions. The model fitted to the heat transfer data is in agreement with the measurements to within ±15% of the range of test conditions. To enable reproducibility of the data, the methods used to define dimensions related to thermohydraulic calculations is discussed in details, and the dimensions provided by the engineering drawing of the exchanger are validated using high resolution computed tomography of the component. Finally, a detailed analysis of the thermohydraulic performance of the headers is given with the goal of setting a benchmark performance for comparison with other designs.