By increase in the power of computer systems and enhanced power of the components and their temperature, including the central processing unit (CPU), cooling just by the air is not effective and there is need for more powerful systems to cool down and increase the power of the cooling system. In this article simulation of the heat exchanger material of the fluid cooling system has been studied using the ANSYS-Fluent software. In this kind of heat exchanger, the water based aluminum oxide nanofluid is used instead of water to increase the total heat transfer coefficient and causing decrease in the output temperature and enhancement of fluid cooling system performance. The results with different speeds of 1000 rpm, 1500 rpm and 2000 rpm and for various volume fractions (1-3%) have been obtained. by increase in the rotational speed from 1000 rpm to 2000 rpm the flowing capacity has increased from 0.0138 kg/s to 0.026 kg/s. for the speed of 1000 rpm, the amount of heat transfer has increased about 13% for the 3% volume fraction. By increase in the volume fraction of aluminum oxide nanofluid, the total heat transfer coefficient increases too, and this increase in the coefficient is approximately similar for different speeds and it causes decrease in the output temperature of the radiator fluid پرونده مقاله