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ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

EFFECT OF LUBRICATING OIL ON THE EVAPORATING HEAT TRANSFER AND PRESSURE DROP OF CARBON DIOXIDE IN A MICRO-CHANNEL TUBE

Get access (open in a dialog) DOI: 10.1615/IHTC13.p14.180
8 pages

Résumé

In this paper, the effect of PAG oil on the evaporation heat transfer and pressure drop characteristics of carbon dioxide has been investigated in a multi-channel micro-tube. The aluminium tube has 3 channels with a square cross section. It has a hydraulic diameter of 2mm, a wall thickness of 1.5mm, and a length of 5m. The heat fluxes ranges from 4 to 12 kW/m2; mass fluxes 450−750 kg/m2s; evaporative temperatures 0−10°C; and qualities from zero to superheated state. The heat transfer coefficients measured were in the range of 4−25 kW/m2K. For the qualities lower than about 0.5, the heat transfer coefficient was found to increase with the quality, which is assumed to be the effect of convective boiling. For the qualities higher than about 0.5, a slight drop in heat transfer coefficients was observed due to local dry-out. The presence of oil showed an interesting trend with mass fluxes. At low mass flux (450 kg/m2s) the presence of PAG oil decreases the HTC. However, the HTC was increased with PAG oil at high mass flux (750 kg/m2s). The pressure drop increases with the quality and mass flux. If the mass flux increases from 450 to 750 kg/m2s, the pressure drop becomes about 1.7 times for pure CO2 and 2.0 times for CO2-oil mixture. The presence of oil turned out to increase the pressure drop by 60−70%.