Direct contact condensation of binary mixtures

Abstract

A boundary-layer analysis of direct contact condensation of binary vapor mixtures on a laminar coolant flowing in a duct is presented. The binary mixture condensate may be immiscible or miscible in the coolant. Both condensable components are, however, assumed completely miscible. The analysis includes also effects of forced convection of the vapor and interfacial resistance at the vapor-liquid interface. The analysis assumes constant properties which are evaluated at an appropriate reference state. The boundary-layer equations were solved numerically in a transformed coordinate system which admitted a similarity solution for short ducts and when the surface resistance is negligible ( B = ∞). The solution is demonstrated for the condensation on water at atmospheric pressure of the immiscible mixture CS 2-CC1 4. For the case of B = ∞ and at the leading edge, the analysis predicts and appreciable reduction in the condensation fluxes as compared to the maximum values obtained when the vapor bulk temperature exists at the interface. This reduction is dependent on the mixture composition and the maximum thermal driving force ( T ∞ − T 0). The effect of the forced convection is found appreciable only for relatively small values of ( T ∞ − T 0). The effect of the surface resistance is observed to be appreciable near the leading edge. The results indicate also that the similarity solution may be extended up to ξ = 0.1.