EXPERIMENTAL STUDY ON POOL BOILING HEAT TRANSFER OF R134a-OIL MIXTURES OUTSIDE SINGLE HORIZONTAL ENHANCED TUBES

摘要

Lubricant oil's existence would make an effect on in pool boiling heat transfer. Different oil concentration and heat transfer condition have different effect. In this paper, heat transfer coefficients are experimentally determined for three horizontal enhanced tubes (E21(C3), E22(A1), E23(B4)) with R134a-oil mixtures. The evaporation temperatures are at 10°C and 5°C, respectively and the refrigerant velocity is ranged from 1.5 m/s to 3.5m/s. The results show that the reinforcement magnification of E21, E22 and E23 is 3.703, 3.035 and 2.709, respectively. The heat transfer coefficients with 100ppm increase to 103.7%～107.% (the evaporation temperature is at 5°C) and 100.8%～110.9% than that of (the evaporation temperature is at 5°C) with 50ppm. The paper may play a foundation for design of evaporator.