Where heat transfer occurs at a temperature of saturation liquid, evaporation or condensation (mass transfer) will occur at the interface level, depending on the direction of the heat flow. In such cases, the convective heat transfer fluid is accompanied conductivity on the surface or of a thin layer of liquid. Since the latent heat and density of the liquid is much more sensible heat and vapor density, heat transfer rates are much higher. You can speed this process by forming a heat exchanger rights (where it is a solid), to improve drainage of condensate or escape of steam bubbles. The total heat transfer will be the sum of two components.
Speed two-phase heat transfer depend on the properties of volatile liquid, interface dimensions, rate of flow, and the degree to which the transmission interface covered with liquid. The driving force of evaporation or condensation, the difference in the pressure of steam at saturation and interface temperatures.
Equations for special liquids on the basis of the interpretation of experimental data and with convective теплопередачи.
Mass transfer may occur from a mixture of gases, such as the condensation of water from humid air. In this case, the couple must go through the air, and mass transfer speed will depend on the concentration of vapours in the air. In the air-water vapor mixture, mass transfer speed is approximately proportional to the speed of heat transfer on this simplifies the interface and predicting the performance of air conditioning coils.
Fundamentals