677 / 2019-04-29 21:50:32

Numerical study on the heat transfer characteristics of carbon dioxide at supercritical pressure in discrete double inclined internal ribbed pipe

Supercritical CO2,transfer enhancement,Numerical simulation, Discrete double inclined rib,Longitudinal swirl flow

全体主题 > 数值模拟、建模与CFD

Supercritical carbon dioxide is a superior choice for refrigeration systems, energy utilization and new power cycle, because it is easy to reach critical points with good thermos physical properties. However, supercritical carbon dioxide in pipe is prone to occur heat transfer deterioration under the action of buoyancy. Adding fins into the tube will effectively inhibit heat transfer deterioration at supercritical pressure, which can improve the heat transfer coefficient and reduce the wall temperature significantly. This paper presents the results of a numerical study on heat transfer enhancement and the flow structure in a heat exchanger pipe fitted with discrete double inclined ribs characterized by a discrete and inclined distribution. The results show that rib-induced vortices significantly weaken the buoyancy effect of flow and convection heat transfer. When the cutting angle of the rib is 45 degrees, the effect of heat transfer strengthening is the best. By increasing the height of the rib or reducing the space between the ribs, the convection heat transfer in the ribbed tube can be further improved. Through the analysis of buoyancy effect and the influence of vortex structure on the flow field, the mechanism of heat transfer enhancement is preliminarily recognized. The conclusions given here can help engineering design of supercritical heat transfer applications more effectively.