International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 04 | Apr 2020 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 1889 Concept of Nano Fluid in Heat Transfer Applications: A Review Reyaj Ahmad Zahid 1 , Nikesh Kumar Ojha 2 , Vishal Shankar Srivastava 3 1 Lecturer, Department of Mechanical Engineering, Govt. Polytechnic, Kuru, Pindra, Varanasi, India 2 Assistant Professor, Department of Mechanical Engineering, TMU, Moradabad, UP, India 2 Assistant Professor, Department of Mechanical Engineering, GL Bajaj Institute of Engineering, UP, India ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract - Heat transfer is an important field for the object of increasing the efficiency of thermal device. One of the way of increasing heat transfer rate by the use of Nano fluid. Nanoparticles result in the increase of thermal conductivity, heat capacity, viscosity, density of Nano fluid. The increase in these parameter of base fluid, increase the rate of heat transfer. This paper presents the increased efficiency, effectiveness in different device by the use of Nano fluid and presents many experimental results on different thermal device which had performed by a number of researchers. Thus availability of a thermal device can be increased and increased availability will help us reduction in carbon emission, pollution and entropy of this earth. Key Words: Nano fluid; Nanoparticles; Thermal conductivity; collectors; solar still; solar pond. 1. INTRODUCTION In 21 centuries, energy has become back bone of a nation. The resources of energy are classified into two parts, Renewable energy and Non-renewable energy. In whole world, most of the countries are dependent on the non-renewable energy. But the sources of non-renewable energy are limited. Thus it become necessary either shift on the renewable energy or effective utilization of non- renewable energy. Effective utilization of non-renewable energy includes increased efficiency of heat engine, effectiveness of heat exchanger etc. so that reduces the irreversibility. This can be done by using of Nano fluid. The use of Nano fluid improves the thermal conductivity, viscosity, density, specific heat etc. which improves the heat transfer rate. We use this increased heat transfer rate in many applications such as solar still, heat exchanger, solar collectors, solar pond, photovoltaic thermal system, vapour absorption refrigeration system, thermal energy storage etc. In this manner we can achieve the maximum utilization of energy in order to reduce the wastage of energy and cost of energy source. 2. NANO FLUID Nano fluid is the name conceived by Choi and Eastman [1] in 1995 at the Argonne National Laboratory (ANL), USA, to Describe a fluid in which nanometer-sized particles are suspended. Nano fluids are a class of heat transfer fluids created by dispersing solid nanoparticles in traditional heat transfer fluids. Nano fluids are a new class of fluid introduce by modern nanotechnology engineered by mixing nanometre-sized materials (nanoparticles, Nano rods, Nano sheet, nanofibers and nanotubes) in base fluids. In other words, Nano fluids are nanoscale colloidal suspensions containing condensed nanomaterial. There is an existence of a double phase system, one is solid phase and other is liquid phase. Nano fluids possess enhanced thermos-physical properties such as, specific heat capacity, density, thermal diffusivity, viscosity, and convective heat transfer coefficients, thermal conductivity compared to those of base fluids like water, ethylene glycol and oil etc. 2.1 Types of Nano fluids Nano fluids can be normally classified into two categories • Metallic Nano fluids • Non-metallic Nano fluids. Metallic Nano fluids are those fluid in which containing metallic nanoparticles such as Cu, Al, Zn, Ni, Si, Fe, Ti, Au and Ag etc. while non-metallic Nano fluids are those fluid in which containing non-metallic nanoparticles such as copper oxide (CuO), aluminum oxide (Al2O3), and silicon carbide (SiC, ZnO, TiO2) etc. and are also includes as non-metallic Nano fluids such as Carbon Nanotubes (Single Wall Carbon Nano Tube (SWCNT), Double Wall Carbon Nano Tube (DWCNT) and Multi Wall Carbon Nano Tube (MWCNT)), nanoparticles core polymer shell composites, semiconductors (TiO2) etc. 2.2 Properties of Nano fluids 1) Thermal conductivity: The thermal conductivity is one of the important parameters for heat transfer enhancement, some studies have been done on thermal conductivity of Nano fluids. All experimental results have indicated the enhancement of thermal conductivity by addition of nanoparticles. For example, Wang et al. [2], Lee et al. [3], and Das et al. [4] measured the thermal conductivity of Nano fluids containing Al2O3 and CuO nanoparticles and investigated the effect of the base fluid on the thermal conductivity of the Nano fluids. Xie et al. [5] examined the effect of base fluid on thermal conductivity of Al2O3 Nano fluid. Li et al. [6] investigated on the temperature dependency of thermal conductivity enhancement of Al2O3/water and CuO/water Nano fluids.