CFD ANALYSIS OF NANO FLUID ACROSS IN LINE TUBE BANKS OF HEAT EXCHANGER

Authors: Vinod mahajan, Dr.Ankur geete, Seshagiri rao G.V.R

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Abstract

Abstract: In the present work, laminar cross flow forced convective heat transfer of nano fluid over tube banks with Circular geometry under constant wall temperature condition is investigated numerically. In this study nanofluid instead of pure fluid, as external cross flow, because of its potential to increase heat transfer rate of the system. The effect of the nanofluid on the compact heat exchanger performance was studied and compared to that of a conventional fluid. The two dimensional steady state Navier-Stokes equations and the energy equation governing laminar incompressible flow are solved using a finite volume method for the case of flow across an in-line bundle of tube banks as commercial compact heat exchanger. The nanofluid used was copper water 1% and the performance was compared with water. In this paper, the effect of parameters such as tube shape circular and heat transfer comparison between nanofluid and pure fluid is studied. Temperature profile, heat transfer coefficient and pressure profile, Nusselt Number were obtained from the simulations and the performance was discussed in terms of heat transfer rate and performance index. The increase in Reynolds number caused an increase in the heat transfer rate and a decrease in the overall bulk temperature of the cold fluid.

Introduction

Flow past tube banks with Circular configurations have wide ranging practical applications, such as in heat exchangers, cooling and heating equipments. There are two important phenomena happening in a heat exchanger: fluid flow in channels and heat transfer between fluids and channel walls. Thus, improvements to heat exchangers can be achieved by improving the processes occurring during those phenomena. Firstly, the rate of heat transfer depends on the surface area to volume ratio, which means the smaller channel dimensions provide the better heat transfer coefficient. Secondly, improving the properties of the heat transfer fluids (nanofluids) can yield higher heat transfer coefficient in a heat exchanger. Nanofluids are colloidal dilute dispersion of nanoparticles (generally less than 5% in volume) such as metals, oxides, carbides, or carbon nanotubes in conventional coolants or base fluids such as water, ethylene glycol, and oil. Miniaturization of electronic components has led to the demand for development of new compact heat exchangers and also cooling fluids with higher heat transfer performance. Modification of thermo physical properties for liquid coolants by adding some solid particles is the main subject of nanofluids. The idea of using metallic particles to increase the thermal conductivity of fluids is not a new concept. By knowing the fact that metals in solid form have much higher thermal conductivity than fluids, Maxwell (1873) who was the one originally proposed the idea of using metallic particles to increase the thermal properties of fluids.

Conclusion

Numerical simulation has been investigated on heat transfer characteristics and pressure drop of Cu/water nanofluid in compact heat exchanger with circular tube shapes and an inline Arrangement of tubes under steady state laminar fluid flow. The numerical results reveal the Enhancement in heat transfer, with respect to the base fluid, identified to characterize nanofluid. Heat transfer enhancement is increasing with the nanoparticle and using circular tube geometry.