Nanofluids: Importance and Application Varinder Singh a , Mr. Sumeet Sharma a ,Dr. D.Gangacharyulu b a Mechanical Engineering Department b Chemical Engineering Department Abstract: In modern days, due to the requirement of the compact systems the heat dissipation rate is point of more concern. Air cooling systems and water cooling systems are not that much effective in small systems because of their size. So it is preferable to use nanofluids in industries for heating and cooling purposes and at the same time cost can also be optimized by reducing the size of system. Nanofluid helps in improving the performance of the thermal systems by enhancing heat transfer rate. Nanofluids are widely used in various applications like as fuel, as coolant in automobiles, in medical and electronic equipments to reduce the thermal resistance. Keywords: nanofluids, heat transfer, coolant Introduction Nanotechnology is the kind of technology which provides the materials with size less than 100 nm called nanomaterial. On the basis of the structure and their properties, nanomaterials are divided into four type of category [1]. Carbon based nanomaterial, metal based nanomaterials and composite. Suspend these nanoparticles into any type of conventional fluid like water, oil, ethylene glycol to make nanofluids. The reason why nano size particles are preferred over micro size particles was well explained [2]. With use of nanoparticles over micro particles, there was a much improvement in thermo physical properties. Some important results are Properties Nanoparticles Microparticles Stability Settle Kinetically stable( long lived in suspension) Conductivity Low High Pump Power High Low Surface/Volume ratio 1 1000 times larger than micro particles Erosion and clogging Yes No Nanofluids can be used for various applications like air conditioning cooling, automotive, power plant cooling, improving diesel generator efficiency etc. because of the unique properties carried by nanofluids [3]. Importance of Nanofluid As we know that now a day sizes of heat transfer devices decreases and at the same time adequate cooling must be provided. It is difficult for the devices to operate under high operating speed, therefore temperature of devises increases to very high value which makes the devices to operate at high power [4]. Due to the poor thermal conductivity of coolant (water, oil etc.), reduced the thermal processing efficiency. Nanofluids enhanced the thermal conductivity of fluids. We can increase the heat transfer rate in thermal systems by adding very small concentrations of nanofluids and can come across the cooling needs of thermal systems. Nanoparticle size plays a vital role in enhancement of thermal conductivity as enhancement in thermal conductivity increased by 40% by particle size below 50 nm [5]. So for lighter size with slow velocity heat exchanger, nanofluids enhanced the thermal