Investigation of the effect of lattice structure on the fluid flow and heat transfer of supercritical CO2 in tubes

Abstract

• Combined experimental and numerical methods to study supercritical heat transfer. • Effects of composite vortex on supercritical fluid and heat transfer were studied. • BCC lattice was used for supercritical CO 2 heat transfer experiment. • Experimental section was fabricated by SLM metal additive manufacturing. • The heat transfer deterioration was suppressed with an acceptable pressure drop. Under specific conditions of low mass flux and high heat flux, heat transfer deterioration (HTD) occurs in tubes, which is detrimental to the supercritical CO 2 heat exchanger. To suppress the HTD and promote the overall heat transfer capability of supercritical CO 2 in a vertical heated tube, the effect of the body-centered cubic (BCC) lattice structure on the fluid flow and heat transfer characteristics were studied. The BCC lattice structure was applied to a supercritical heat transfer experiment by exploiting selective laser melting (SLM) metal additive manufacturing. The results of the experimental and numerical studies indicate that the BCC lattice structure can effectively suppress the HTD by generating a composite vortex composed of a horseshoe vortex at the leading edge of the lattice ligaments, the streamwise vortex at the trailing edge of the ligaments, and the counter-rotating longitudinal vortex at the center of the ligaments. The vortex system strengthens the local turbulence intensity and enhances flow mixing, thus weakening the buoyancy effect and suppressing the HTD. Compared with the smooth tube, the average heat transfer coefficient of the tube with BCC lattice structure increased by up to 100%, whereas the pressure drop increased by 13.5%.