| Forced convection heat transfer with condensation of mixture gases is commonphenomena, extensively existing in oil gas condensation reclovery, air-conditioning andrefrigeration, industrial recovery of waste heat. The present essay is focused on theforced-convection heat transfer with condensation of humid air or mixture gasescomposed of humid air and alkane. Characterstics of heat and mass transfer offinned-tube heat exchangers were studied based on the combined therotical andexperimental methods.The mathmetical model was built and the phase interface characteristics of humidair coming across the cold wall were numerically analyzed. The effects of thecondensate subcooling on the condensate film development and on the condensationheat transfer were discussed. Momentum, energy and mass transfer characteristics wereanalysed for different conditions and the effects of neglecting the condensate film on thenumerical solutions of humid air condensation heat transfer were specified.Numerical models, respectively on condensation occurring or no condensation,were built for humid air forced-convection heat transfer on circular fins, due to themeaning of fin efficiency on the finned-tube heat exchangers during engineeringapplication. Shortage of the Modified Schmidt model was numerically analyzed.Combined with the analytical solution and the numerical results, the heat transfer finefficiency and mass transfer fin efficiency were discussed and the meaning of heat andmass transfer fin efficiency on the humid air dehumidification was revealed. Anaccurate but simple fin efficiency model was put forward, based on the equivalent finefficiency. Heat transfer equations of the temperature difference method and theenthalpy difference method were comparatively analyzed and the heat transfer equationof mixture gas, typical of more than two components, was deduced, according to theheat and mass transfer characteristics of circular fin. Then, the fin transportationcapacity to heat and mass transfer for mixture of alkane vapor and humid air wasanalyzed.Test setup was built to realize the visulazation observation on the condensate filmof humid air condensation. The fin-side forced-convection condensation heat transferand flow pressure drop were experimentally studied for humid air on six types of finned-tube heat exchangers. The analysis of the condensation occurring or nocondensation conditions on fin pitches, hydrophilic fin surface and fin structures wasmade based on the form of the heat transfer equation with condensation occurringdiscussed. The Lewis number was analyzed for different conditions. |
