Experimental study on the heat transfer characteristics of nanorefrigerants in an internal thread copper tube

The flow boiling heat transfer characteristics of four nanorefrigerants in an internal thread copper tube were experimentally studied. The nanorefrigerants were Cu-R141b, Al-R141b, Al2O3-R141b, and CuO-R141b. The performance of refrigerants that were added with nanoparticles at different mass fractions, quality, and mass fluxes was analyzed. The experimental parameters were as follows: nanoparticle mass fractions, 0.1 wt.%, 0.2 wt.%, and 0.3 wt.%; quality values, 0.3-0.8; and mass fluxes, 120, 210, and 330 kg m−2 s−1. The specifications of the copper tube test section were as follows: length, 1400 mm; outside diameter, 9.52 mm; inner diameter, 8.22 mm; bottom wall thickness, 0.4 mm; tooth depth, 0.25 mm; total wall thickness, 0.65 mm; tooth apex angle, 40°; helix angle, 18°; and thread number, 60. Results showed that the maximum heat transfer coefficient of the four kinds of nanorefrigerant increased by 17-25%, the average heat transfer coefficient increased by 3-20%, and the maximum heat transfer coefficient of Cu-R141b nanorefrigerant increased by 25%.