Experimental investigation on Al2O3-W, SiO2-W and ZnO-W nanofluids and their application in a shell and tube heat exchanger

In this research, overall performance of a shell and tube heat exchanger operated with Al2O3-W, SiO2-W, and ZnO-W nanofluids were experimentally investigated. Al2O3-W and SiO2-W nanofluids were prepared without using any surfactant. The polyvinylpyrrolidone (PVP) surfactant was used to stabilize ZnO-W and Fe3O4-W nanofluids. Photo capturing method was used to justify the stability. However, Fe3O4-W nanofluid has not been stabilized by PVP so it was not considered for further analysis. Highest convective heat transfer coefficient (h(fT)), overall heat transfer coefficient (U-o), and actual heat transfer (q(fT)) have been observed for ZnO-W and lowest effectiveness (epsilon), h(fT), U-o and q(fT) have been found for SiO2-W. Approximately, 50%, 15%, and 9% enhancement in h(fT) have been found for ZnO-W, Al2O3-W, and SiO2-W nanofluids, respectively. About 35%, 26%, and 12% improvement of Uo were observed accordingly for using the above-mentioned nanofluids and q(fT) also improved around 51%, 32%, and 26%, respectively compared to water. Experimentally, in case 1 (at constant shell side fluid flow of 4 lpm with different tube side fluid flow from 2 to 8 lpm), highest performance can be attained at 6 lpm using 0.3 vol.% of ZnO-W (with PVP) nanofluid. Likewise, highest performance reached at 7 lpm using 0.5 vol.% of Al2O3-W and SiO2-W. In case 2 (at the constant tube side fluid flow of 4 lpm with different shell side fluid flow from 2 to 8 lpm), highest performance can be achieved at 8 lpm for all nanofluids. However, overall performance of the shell and tube heat exchanger can be improved about 35% by using ZnO-W (with PVP) nanofluids. (C) 2016 Elsevier Ltd. All rights reserved.