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 degrees; helix angle, 18 degrees; 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%. (C) 2013 Elsevier Ltd. All rights reserved.