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

摘要

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/(m~2-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 25 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.