Analysis on thermal and flow behavior of triple concentric tube heat exchanger handling MWCNT-water nanofluids

Abstract

Design of heat exchangers and heat transfer enhancement methods are struggling to meet out the cooling demand of present scenario. Many researchers suggested that the addition of nanosized solids particles into traditional base fluids resulting the higher heat transfer rate than the existing coolants and named the new fluids as nanofluids. In this investigation, the effect of microwave carbon nanotube (MWCNT)-water nanofluids on heat transfer rate, pressure drop and pumping power of a triple concentric tube heat exchanger are experimentally investigated and compared the results of MWCNT-water nanofluids with water. The MWCNT-water nanofluids were prepared by two step method at the volume concentrations of 0.2%, 0.4%, and 0.6%. The range of target fluid mass-flow rate is in the range of 0.026 to 0.039 kg per second and the constant heat flux condition is considered. On experimentation, it is noted that the effectiveness and presure drop of 0.6% MWCNT-water based nanofluids are 27% and 21% greater than water at the maximum mass-flow rate. The reason for improved heat transfer rate of nanofluids is because of higher thermal conductivity, Brownian motion, lower boundary-layer thickness, and lower specific heat capacity of nanofluids. Also found that the pumping power increases with increasing volume concentration and pumping power is 25% higher than water at the 0.6% nanofluids. Therefore, the MWCNT-water nanofluids are good choice for replacing water as coolant in triple concentric tube heat exchanger.