Condensation of hydrocarbons – A review

Hydrocarbons are one of the candidates for refrigerants of next generation heat pump and refrigeration systems. Although the hydrocarbons have superior thermophysical properties as a refrigerant to fluorocarbons and are widely used in domestic refrigerators, their flammability prevents their wide application to larger systems, such as residential and packaged air conditioners, car air conditioners, heat pumps, etc. In this paper, recent studies on condensation of hydrocarbons are reviewed since it is one of the key technologies. For in-tube condensation, heat transfer coefficients of smooth tubes are correlated well with previously proposed equation developed with data of the fluorocarbons. On the other hand, few data are available for enhanced tubes. In the case of condensation on a horizontal tube, heat transfer of smooth tube is explained well by the Nusselt theory. However, different heat transfer characteristics appear for enhanced tubes. Since blended hydrocarbons would be used to obtain suitable properties, models of mixed vapor condensation are also reviewed.