Laminar film condensation with vapour drag on a flat surface

Abstract

k. L. 1, m. NOMENCLATURE dimensionless friction drag number ( = pr,h;J’/ @,I; diameter of the porous tube: equivalent diameter of rectangular condensation duct (= 4 x cross sectional area/ perimeter): shear force at liquid-vapour interface; friction factor under suction conditions: friction factor in the absence of suction: gravitational acceleration: average condensation heat transfer coefficient between x = 0 and x = I: terminal condensation heat transfer coefficient at x = 1: liquid-vapour enthalpy change modified for liquid film undercooling ( = h,, + $cPO,): thermal conductivity of liquid: length of the porous tube; total length of the condensation test section: condensate mass flow rate per unit width at section .Y; Nu, Nu,. average Nusselt number (= hlik): terminal Nusselt number (= h,l/k): Re,. Reynolds number of air in suction experiments ( = pED/pc); Re,, ‘two-phase’ Reynolds number (pii,,l/p): Sh. the condensation group p’g sin ~h~,rs/4~k0,: t,. t,, saturation temperature, wall temperature: u, local weighted mean air velocity along tube in suction experiments: a,. weighted mean vapour velocity in condensation duct; Ud. velocity at liquid-vapour interface: L’,. suction velocity of air normal to, and at. the porous wall: x, axial distance from beginning of condensation section, or from entry of porous tube: 8. suction coefficient (= o,/ii); 8. ii,. liquid film thickness at X. at Y = 1;