The heat transfer co-efficient (HTC) was measured in nanofluids made from ethylene glycol water mixture dispersed with different amounts of graphite nanoparticles (GRNP) at different flow rates (Reynolds number Re = 50 to 800) and temperatures range between 10 to 85 °C. It was observed that the HTC was highly dependent on the Re with two regimes. HTC was found to follow the power law of the type (HTC) = A (Re)χ where the exponent χ was dependent on Re range, composition and temperature. In the high Re regime, the exponent was of the order of 0.5 while at low Re regime (Re < 150) the χ value was 0.85 to 0.92. The HTC at low Re values could be correlated with the thermal conduction process and Brownian motion, while at high Re, random motion could be prevailing. The results have been compared with the reported data for carbon nanotubes (CNT) for which also the exponent was much more than 0.333 which is indicated in the standard Sieder-Tate equation. Thus, the overall variation of HTC with Re appears to be HTC= A Reχ where χ assumes values depending on the regimes of Re viz. low, intermediate and high Re with χ ≈ 0.92, 0.3 < χ <0.5 and χ ≥ 0.85 respectively.