Enhancement of thermal performance of a shell and helically coiled tube heat exchanger using al2o3 water nanofluids

Abstract

Research studies on heat transfer enhancement have gained serious newlinemomentum during recent years and have been proposed many techniques by newlinedifferent research groups. Conventional heat transfer fluids have inherently newlinelow thermal conductivity that greatly limits the heat exchange efficiency. newlineMoreover, the cooling capacity of conventional heat transfer fluids and redesigning newlineof heat exchangers have reached their limitations. A novel fluid newlinewith higher thermal conductivity has been developed to overcome these newlineproblems. The dispersion of 1-100nm sized solid nanoparticles in the newlinetraditional heat transfer fluids, termed as nanofluids, exhibit substantial higher newlineconvective heat transfer than that of traditional heat transfer fluids. newlineIn this experimental investigation, the two passive heat transfer newlineenhancement techniques such as helically coiled tube and Al2O3 water / newlinenanofluids are taken together to study the heat transfer and pressure drop. newlineThe Al2O3 water / nanofluid at 0.1%, 0.4% and 0.8% particle volume newlineconcentration have been prepared by using two step method in this newlineinvestigation. The dry Al2O3 nanoparticles and dispersed Al2O3 nanoparticles newlinein distilled water have been characterized by using X-Ray Diffraction (XRD) newlineand Scanning Electron Microscope (SEM). It is found that the average newlineparticle size is between 45- 50nm and the particles are uniformly dispersed in newlinedistilled water. The thermal conductivity and viscosity of nanofluid have been newlinemeasured by using KD2 thermal analyzer, and Brookfield viscometer newlinerespectively. It is found that the thermal conductivity and viscosity newlineincrease with increasing particle volume concentration. The stability of nanofluids have been studied by using UV -Visible spectrophotometer, pH newlinemeter and photo capturing techniques under static and flow conditions. It is newlinestudied that the 0.4% and 0.8% nanofluids are stable for 30 days from the date of newlinepreparation except 0.1% volume concentration. newline