Numerical Study of Compact Heat Exchanger Designs for Generation IV Supercritical Carbon Dioxide Power Conversion Cycles

Geometrical effects on the local heat transfer coefficient (HTC) and pressure drop for supercritical carbon dioxide in printed-circuit heat exchangers are numerically quantified. Combinations of different operating pressures (7.5 to 10.2 MPa), mass fluxes [326 to 762 kg/(m2⋅s)], and the enhanced wall treatment k-ε and shear stress transport k-ω turbulence models are investigated using a finite-volume framework. Three different channel geometries are used: a nonchamfered zig-zag (ideal case), a chamfered zig-zag (prototype case), and an airfoil (ideal case). The simulations are compared with experimental results and empirical correlations. A new correlation is developed based on the numerical data obtained and published experimental data for the zig-zag channels. The results show that the local HTC increases with an increase in operating pressure or an increase in mass flux for each channel. The HTC of the zig-zag channel is found to be approximately 2.5 times that of the airfoil; however, the pressure drop is 4.0 to 8.3 times higher. Based on these results, the area goodness ratios of the nonchamfered and chamfered zig-zag channels are respectively 2.65 and 1.57 times larger than that of the airfoil.