Experimental assessment of Al2O3 and Cu nanofluids on the performance and heat leak of double pipe heat exchanger

The aim of the study is to experimentally investigate and compare the influence of two different nanofluids (Cu/water and Al2O3/water) on the performance of a double pipe heat exchanger at different volume concentrations and flow rates. Effect of varying hot-side inlet temperature is also tested for the selected concentrations. The nanofluid, pumped on the shell-side of the heat exchanger, has a Reynolds number ranging from 7000 to 15,000 while, for each Reynolds number, the concentration of the nanoparticles ranges from 0.26% - 0.83% on volume basis. Results indicated that presence of nanoparticles within the base fluid can offer a great potential for energy transfer. Observation of experimental outcomes shows notable enhancement in the Nusselt number when increasing the mass-flow of the nanofluid. The enhancement registered for the above mentioned range of Re and concentration are up to 13% for Al2O3 and 23% for Cu. Experimental results show a considerable improvement in the effectiveness (up to 7% for aluminum oxide and 10% for copper). Also, the performance enhances with the augmentation of the hot-side inlet temperature. Heat leak from the shell-side (cold fluid) to atmosphere is observed to be enlarged when nanoparticle is employed and is proportionally related to the concentration. It is also monitored that the heat leak within aluminum oxide nanofluid is greater than the copper nanofluid.