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Abstract
For one polar and several apolar working fluids, the vapor-liquid flow and the heat transfer characteristics in a capillary tube are obtained and compared. The polarity of the working fluid has a close relation to the disjoining pressure, which affects the formation of the liquid film profile greatly. For a polar working fluid (water), the length of the evaporating interfacial region is much longer than those for apolar working fluids. And the thickness of its liquid film increases relatively more gently at the end of the evaporating interfacial region. For different apolar working fluids, the calculation results are similar and the above-mentioned lengths are shorter. The difference is due mainly to the fact that the stronger polar working fluid leads to much stronger disjoining pressure, and the evaporation is choked because the liquid molecules of polar working fluids on the vapor-liquid interface are strongly attracted by the solid wall. The effects of other factors on the length of the evaporating interfacial region and the profile of the vapor-liquid interface are more secondary.