Methodology to develop off-design models of heat exchangers with non-ideal fluids

We demonstrate the proposed methodology by developing numerical models for two PCHEs: (1) an sCO2-sCO2 PCHE operating far from CO2's critical point and (2) an oil-sCO2 PCHE operating close to CO2's critical point, where non-ideal fluid property variations are significant. Test data spans heat loads from 6-48% and 15-39% of name-plate duty for heat exchangers (1) and (2) respectively. Across these operating ranges, the maximum and mean heat transfer prediction residuals are 0.91% and 0.36% for heat exchanger (1) and 3.04% and 1.24% for heat exchanger (2). Additionally, we show that good accuracy can be obtained when using only the channel hydraulic diameter as a fitting parameter. Due to their low computational cost and high accuracy, models developed using the proposed methodology are eminently suitable for off-design modelling and optimisation of the sCO2 closed Brayton cycle and other power cycles or industrial processes where heat exchangers exhibit complex nonlinear behaviour.