HEAT-TRANSFER WITH POOL BOILING OF HYDROCARBONS AND HALOGENATED REFRIGERANTS AT A PLAIN AND A HIGH-PERFORMANCE FINNED TUBE

Heat transfer with pool boiling of five hydrocarbons and two halogenated refrigerants was measured for a plain and a high performance finned tube over an extended range of heat fluxes and saturation pressures. The finned tube with T-shaped cross sections of the fins contains additional cavities at the bottom of the channels between the fins to enhance heat transfer (type: GEWA-TX). For the plain tube, the influence of heat flux, saturation pressure and thermophysical properties of the boiling liquid can be represented in a rather uniform manner with all of the nine substances. In the case of the finned tube, the corresponding relations are more complex than is known from traditional finned tubes, because of the special form of bubble release with this tube. Compared to the plain tube, the finned tube investigated seems to be favourable when used for hydrocarbons and the new refrigerants, and for boiling conditions at comparatively low saturation pressures.