Heat transfer and fluid flow characteristics of two-phase impinging jets were experimentally investigated under a fixed pumping power condition. The effects of dimensionless pumping power (P-pump* = 1.4 x 10(11)-2.8 x 10(12)) and the volumetric fraction (beta = 0.0-1.0) on the Nusselt number were considered. Air and water were used as the test fluids. The results showed that the Nusselt number increased with volumetric fraction, attained a maximum value at around 0.2-0.3 of the volumetric fraction, and then decreased. By observing flow patterns, the optimum value of the Nusselt number was found to be in the bubbly flow region. Based on the experimental results, correlations for the normalized stagnation and average Nusselt numbers of impinging jets were developed as a function of the volumetric fraction alone. (C) 2010 Elsevier Ltd. All rights reserved.