Journal of Material Science and Mechanical Engineering (JMSME) Print ISSN: 2393-9095; Online ISSN: 2393-9109; Volume 2, Number 9; April-June, 2015 pp. 82-86 © Krishi Sanskriti Publications http://www.krishisanskriti.org/jmsme.html Role of Nanofluids on Heat Transfer Enhancement in Helical Coil Heat Exchangers Sonam Sandhu 1 , Munish Gupta 2 and Vinay Singh 3 1,2,3 Deptt of Mech Engg, GJUST Hisar E-mail: 1 sandhusonam022@gmail.com, 2 mcheeka1@gmail.com, 3 theahlawat89@gmail.com Abstract—Nanofluids are abeyance of metallic or non-metallic nanoparticles (1-100nm) in base fluid and are synthesized to provide considerable preferences over conventional heat transfer fluids. By improving thermophysical properties of nanofluid, heat transfer characteristics can be increased. This paper depicts a complete review on nanofluids challenges and applications. Forced convective heat transfer with nanofluids in helical coil heat exchanger is also presented and reviewed. Also, challenges on applications of nanofluids has been reviewed and presented. This paper illustrates latest advancements in study of nanofluids, as well as preparation methods, working for heat transfer improvements, and utilization in heat transfer field. Keyword: Nanofluids, Synthesis, Helical Coil heat exchanger 1. INTRODUCTION Due to energy disaster and energy dissipation in various industries, heat transfer has been emerged as an utmost crucial and relevant area in engineering sciences i.e. mechatronics , microelectronics, electronic component, power generation, air conditioning, petrochemical, oil gas industry .For enhancing the rate of heat transfer ,addition of solid particles into heat transfer media is a new invention.. In spite of major attention to use suspended millimeter sized particles is that they possess plausible to cause various problems such as clogging, large pressure drop, erosion, settlement of particles, sedimentation of particles [28]. To overwhelm the shortcoming faced by micro/macro sized particles, Choi [1] Argonne National Laboratory USA has dispersed nanosized particles in range of 1-100 nm into base fluids. Reasons for using these nanofluids are superior properties such as long-lasting stability, enhancement in heat transfer, high thermal conductivity; reduce clogging, less energy for pumping the fluid and ultimately reduction in cost. Nanofluids i.e. water, polymer solution, bio-fluids, ethylene glycol and oil, that are the cessation prepared by scattering nanometer-sized solid particles such as metals (Gold, copper, Silver, Iron ); carbide ceramics ( titanium carbide, silicon carbide); oxide ceramics ( copper oxide, aluminum oxide); semiconductor (Titanium oxide); nonmetal includes graphite, single-,double-, or multi- walled carbon nanotubes and composite materials such as nanoparticles core-polymer shell composites. Nanofluids posses the following benefits [26]: Specific surface area is higher as compared to conventional fluids, large heat transfer surface, decreased particles obstruction, decreased scattering stability accompanying main particles. Also because of Brownian motion miniaturized pumping power is required, hence stronger system miniaturization, fast cooling and heating, superior lubrication to suit the different applications. Except these, they have adjustable properties such as thermal conductivity and varying particles .Due to these applications, nanofluid successively used in lighter and shorter heat exchangers . 2. SYNTHESIS OF NANOFLUIDS Two methods have been used in production of nanofluid: one step and two step technique. Two step method is superior for preparation of nanofluid. Initially, with the help of chemical or physical method they are produced as dry powder. By utilizing exhaustive magnetic force mixing, ultrasonic stirring, homogenizing and ball milling, high share agitation in second processing step, dispersion of exhaustive nanosized powder will be done into base fluid. By using two step method, suspension of prepared TiO 2 in water will be done by Murshed et al [2].In the one step method, nanoparticles produced and scattered directly into base fluid at the same time. Single step is also called as VEROS (Vacuum Evaporation onto a Running Oil Substrate) a method which was developed by Akoh et al [3].Benefits of such technique is agglomeration of nanoparticles are minimized. Modified VEROS method which was developed by Eastman et al [4].This method includes direct condensation of Cu vapour into nanoparticles by contacting it with flowing low-vapor-pressure liquid (EG).A novel one-step chemical method for preparing copper nanofluids by reducing CuSO4.5H2O with NaH2PO2.H2O in ethylene glycol under microwave radiation was presented by Zhu et al [5]. Their results showed that the properties of nanofluids and reaction rate are the two factors which are affected by insertion of NaH2PO2.H2O and the ratification of microwave irradiation. This method is compatible with only single low vapor pressure fluids [30].