FREE CONVECTIVE CONDENSATION IN A VERTICAL ENCLOSURE

Free convective condensation in a vertical enclosure was studied numer ically and the results were compared with experiments. In both the num erical and experimental investigations, mist formation was observed to occur near the cooling wall, with significant droplet concentrations in the bulk. Large recirculation cells near the end of the condensing section were generated as the heavy noncondensing gas collecting near the cooling wall was accelerated downward. Near the top of the enclosu re the recirculation cells became weaker and smaller than those below, ultimately disappearing near the top of the condenser. In the experim ent the mist density was seen to be highest near the wall and at the b ottom of the condensing section, whereas the numerical model predicted a much more uniform distribution. The model used to describe the form ation of mist was based on a modified critical saturation model (MCSM) , which allows mist to be generated once the vapor pressure exceeds a critical value. Equilibrium, nonequilibrium, and MCSM calculations wer e performed, showing the experimental results to lie somewhere in betw een the equilibrium and nonequilibrium predictions of the numerical mo del. A single adjustable constant (indicating the degree to which equi librium is achieved) is used in the model in order to match the experi mental results. (C) 1997 Elsevier Science S.A.