A Review on Theoretical and Experimental Studies on Improving the Thermal Conductivity Coefficient of Nanofluids

Conventional heat transfer fluids, such as water, oil and ethylene glycol, are used in a variety of industries, such as chemical processes, refrigeration, cooling and heating processes, transportation, power plants and micro-sized industries with a low-heat transfer characteristic. Increasing the coefficient of thermal conductivity is the key idea to improving the heat transfer properties of conventional fluids. Solid particles have higher thermal conductivity than the base fluid, as a consequence it is expected that the heat transfer coefficient could be increased by suspending solid particles in the base fluid. Nanofluids, which are diluted suspensions containing nano-particles, seem to be a hopeful option for next generation of thermal systems. However, there are several researches reported the various parameters affecting heat transfer coefficient of nanofluids. In spite of several models have been proposed to predict their thermal conductivity coefficient, still a unique model that can predict all possible heat transfer mechanisms of nanoparticles is lacking.