Global Effects of MWCNT-W Nanofluid in a Shell & Tube Heat Exchanger

Abstract

Global warming and other problems can be reduced by effectively using the available materials and facilities. Heat exchangers play an important part of the field of energy conservation, conversion and recovery. Shell & tube heat exchangers are widely using in industrial processes and power plants. Suspension of small amounts of nanoparticles into the base fluid called nanofluid can reduce the global energy losses. Thermal conductivity of Multi Walled Carbon Nanotube (MWCNT) is highest among the different nano materials [1]. Therefore, in this paper, the overall performance of a shell & tube heat exchanger has been analytically investigated by using MWCNT-W nanofluid with 0.02-0.1 vol. fractions of MWCNT and compared with water. Mathematical formula, specifications of heat exchanger and nanofluid properties were taken from the literatures to analyze the energy performance and other effects within the system. It is found that for certain mass flow rates of nanofluid and base fluid, the convective heat transfer coefficient increased around 4% to 17% compared to pure water, respectively for 0.02-0.1 vol. fractions of MWCNT in water. However, for constant vol. fractions of MWCNT, convective heat transfer coefficient of the above nanofluid negligibly changed for different mass flow rates. Furthermore, energy effectiveness of the heat exchanger also improved approximately by 3% to 14%, respectively. This energy effectiveness again improved with the decrease of the mass flow rates of nanofluids (tube side) and increase of the mass flow rates of base fluid (shell side). As energy effectiveness is increased by using MWCNT-W nanofluid, therefore, a significant amount of heat losses will be reduced. As a result, with the reduced heat emissions, global warming and greenhouse effects can be reduced by using MWCNT-W nanofluid as working fluid in shell & tube heat exchanger system.