HEAT TRANSFER IN POOL BOILING OF BINARY AND TERNARY NON-AZEOTROPIC MIXTURES

摘要

Heat transfer coefficients in nucleate pool boiling of binary and ternary non-azeotropic hydrocarbon mixtures were obtained experimentally using a vertical electrically heated cylindrical carbon steel surface at atmospheric pressure with several surface roughnesses. The fluids used were Methanol/1-Pentanol and Methanol/1-Pentanol/1,2-Propanediol at constant 1,2-Propanediol mole fraction of 30percent. Heat fluxes were varied in the range 20 to 235 kW/m~(2). The cylindrical heater surface was polished to an average surface roughness of 0.2 (mu)m, and sandblasted yielding surface roughness of 2.98 and 4.35 (mu)m respectively. The experimental results were compared to available prediction correlations, indicating that the correlations based on the boiling range are in better qualitative agreement than correlations based on the phase envelope. Increasing the surface roughness resulted in an increase in the heat transfer coefficient, and the effect was observed to be dependent on the heat flux and fluid composition.