화학공학소재연구정보센터
International Journal of Heat and Mass Transfer, Vol.40, No.14, 3395-3406, 1997
Free and Forced-Convection Laminar-Film Condensation on Horizontal Elliptic Tubes
Laminar film condensation on a horizontal elliptical tube in a pure saturated vapor was analyzed for conditions of Free and forced convection. For free convection, a simple Nusselt type analysis was used. For forced convection, estimation of the interfacial shear stress was made in two ways : the first used an asymptotic value of the shear stress under conditions of infinite condensation rate and the second was based on simultaneously solving the two-phase vapor boundary-layer and condensate equations. Effects of surface tension and pressure gradient in the condensate film were also included. For free convection, an elliptical tube with the major axis vertical showed an improvement of nearly 11% in the mean heat-transfer coefficient when compared to a circular tube of equivalent surface area. For forced convection with the same approach velocity as for a circular tube, a small decrease (approximate to 2%) in the mean heat-transfer coefficient resulted. However, for the same pressure drop, heat transfer performance for an elliptical tube increased by up to 16%.