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Attempts for investigation of flows forced convective heat transfer using nanofluids have been made by numerous researchers in the recent years‎. ‎Utilizing nanofluid as a working fluid in lots of the literatures is greatly recommended To achieve higher efficiency in cooling systems. ‎ The present study surveys laminar flow forced convective heat transfer of Al‎2‎O‎3-‎water nanofluid, numerically under variable heat flux‎. Classical models which have been widely utilized for evaluating thermophysical characteristics of a nanofluid are used in the study and the effects of nanofluid heat transfer characteristics are assessed‎. ‎Two types of the pipe consist of finless tube and finned pipe are investigated‎. ‎Effects of the parameters such as variable heat flux parameter‎, ‎nanoparticle concentration‎, ‎and the Reynolds number are also assessed‎. ‎The numerical results demonstrate that the convective heat transfer coefficient of nanofluid in the both type pipes increases in accordance with volume concentration as well as Reynolds number of nano‎-particles. Furthermore‎, ‎the average convective heat transfer coefficient in the finless pipe is the same as the constant heat flux case; but‎, ‎thermal efficiency of the finned pipe under variable heat flux has higher value in comparison with the constant heat flux case‎.