Enhancement of heat transfer with nanofluids

Abstract

The present dissertation reports the experimental study pertaining to enhanced heat transfer performance of nanofluids compared to water in several thermal devices. The objective of the present study is to analyze the thermal performance of nanofluids for various practical applications including heat exchanging equipments, automobile radiators, flat plate solar collector and cooling of electronics components. In this study, efforts have been made to study the heat transfer performance of various thermal devices. Tests have been performed to study the forced convection and heat transfer characteristics of Al2O3/water and carbon nanotube/water nanofluids through uniformly heated horizontal circular pipe with helical twisted tape inserts (HI). The experiments are performed with varied range of particle volume concentration (0.15%, 0.45%, 0.60% and 1%) and helical tape inserts of twist ratio (TR) = 1.5, 2.5 and 3. Next, an experimentally study has been carried out to evaluate the convective heat transfer characteristics of CNT/water and Al2O3/water and nanofluids in an automobile radiator. The effects of various parameters, namely synthesis method, variation in pH values and nanoparticle concentration on the Nusselt number are examined through the experimental investigation. The comparison of thermal performance for CNT/water and Al2O3/water nanofluids is reported in the present investigation. The heat pipes are integrated into flat plate solar water heater to evaluate the thermal performance of solar flat plate collector. Here, two different fluids such as: CNT/water nanofluids and pure water are used as working fluid in the heat pipe. The effect of the tilt angle, filling ratio, nanoparticle concentration and coolant flow rate onthe thermal performance of the solar collector has been discussed in the study. Further, an attempt has been made to evaluate the thermal performance of nanofluid (CNT/water) charged heat pipe with phase change material (PCM) as energy storage material (ESM) for electroniccooling. Tests are conducted for two different ESM (water and paraffin), different fan speeds and heating powers in the PCM cooling module. The temperature variations in PCM are obtained during charge/discharge processes. Keywords: Nanofluid, CNT/water, Al2O3/water, heat transfer, helical screw tape inserts Nusselt number, Reynolds number, friction factor, thermal performance, automobile radiators, heat pipe, solar flat plate collectors, phase change material, electronics cooling