Simulation of Vapor-Liquid Separation in the Orifice-Baffle Header under Various Operating Conditions

Abstract

Vapor-liquid separation during condensation enables the enhancement of heat transfer coefficient and reduction in pressure drop simultaneously. The vapor-liquid separator is vital to the performance of such a liquid-separation condenser (LSC). It should fulfill the functions of allowing the condensate to drain away as much as possible from the separator and leaving only vapor to continue condensing afterwards. However, due to the intensive interactions between the liquid and vapor, it is really hard to achieve perfect vapor-liquid separation, adding new uncertainties to the maldistributions in the branch outlets of a parallel condenser. To discover more insights of the flow conditions in the header and phase distributions, the characteristics of the orifice-baffle header are studied by using CFD and the mechanistic model for the droplet analysis is established by means of force balance in this paper. A parametrical analysis is carried out to discover the effects of operating conditions. It is found that the maximum vapor-liquid separation efficiency (η) is 51.94% as the inlet mass flow rate (ṁin) is 12 g/s. The vapor leakage from the orifice because of the liquid impact is one of the main reasons that deteriorate the vapor-liquid separation performance. Moreover, the vortex in the header increases the local mass flux, thereafter decreasing the droplet diameter. With the increasing of ṁin, the dominant force of the droplet in the vertical direction switches from FG to FD2.

Keywords

• condenser
• vapor-liquid separation
• simulation
• separation efficiency