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 (hfT), overall heat transfer coefficient (Uo), and actual heat transfer (qfT) have been observed for ZnO-W and lowest effectiveness (ε), hfT, Uo and qfT have been found for SiO2-W. Approximately, 50%, 15%, and 9% enhancement in hfT 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 qfT 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.