ISSN Online: 2377-424X
ISBN Print: 0-89116-559-2
International Heat Transfer Conference 8
NUCLEATE AND FILM BOILING HEAT TRANSFER IN R11: THE EFFECTS OF ENHANCED SURFACES AND INCLINATION
Resumo
A study of pool boiling heat transfer in R11 is reported as function of surface characterization and inclination. Two specially prepared metal sprayed surfaces and flat copper and steel surfaces were subjected to heat fluxes to 180 kW/m2 with surface orientations varying from horizontally facing downward (180°), to vertical (90°), to horizontally facing upward (0°). The resulting nucleate boiling curves display considerable boiling hysteresis with the hysteresis temperature difference decreasing with increase in angle of inclination. Minimum film boiling heat fluxes and temperature differences generally decrease with increase in angle of orientation. At 0° as surface roughness and porosity are increased the minimum film boiling heat flux and temperature differences increase. For 180° the minimum heat flux is only slightly affected by surface characteristics whereas the surface superheat is moderately influenced as compared to 0°. The results obtained are compared with values determined from existing theoretical and experimental work.