Experimental evaluation on flow boiling heat transfer of R290/POE-oil working fluid for absorption refrigeration in smooth horizontal tubes

Abstract

The research on working fluids of refrigerant/absorbent mixture is important for the development of the absorption refrigeration area. R290/POE-oil mixture is a new potential working fluid, in which R290 (propane) is the refrigerant and POE oil is the absorbent. This refrigerant/oil working fluid has a wide operating range, low generation temperature, and no corrosion to metals. Flow boiling heat transfer performance of the new working fluid in smooth horizontal tubes has been experimentally investigated in this paper. The R290 concentration for the experimental working fluid was selected as 11 wt%. The test sections were horizontal smooth stainless steel annular tubes with outer diameters of 6, 8 and 10 mm. The boiling saturation pressures in the test sections coincided with the actual operation of the absorption refrigeration cycle, which were set as 1.2 MPa, 1.3 MPa, 1.4 MPa, respectively, corresponding to boiling temperatures 55.3 °C, 58.7 °C, 62.5 °C. The mass fluxes were 166 kg m−2s−1, 221 kg m−2s−1, 276 kg m−2s−1, 332 kg m−2s−1 and 387 kg m−2s−1. The effects of heat flux, vapor quality, mass flux, boiling temperature and tube diameter on the flow boiling heat transfer coefficient were displayed and analyzed. Experimental results show that heat flux, mass flux and vapor quality have obvious effects on the coefficients; the nucleate boiling mechanism plays an important role, and the convective boiling mechanism plays a significant role in the boiling process. The present study is of good significance to the application of R290/POE-oil working fluid and the design and optimization of the finned-tube generators in absorption refrigeration systems.