EFFECTS OF THE POLARITY OF WORKING FLUIDS ON VAPOR-LIQUID FLOW AND HEAT TRANSFER CHARACTERISTICS IN A CAPILLARY

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 working fluid has close relation with the disjoining pressure, which effects the formation of liquid film profile greatly. For the polar working fluid (water), the length of the evaporating interfacial region is much longer than those of apolar working fluids. And its thickness of 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 mainly due to 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 is strongly attracted by the solid wall. The effects of other factors on the length of the evaporating interfacial region and the profile of vapor-liquid interface are more secondary.