The exergy efficiency and pumping power of nanofluid through a helically coiled tube heat exchanger under turbulent flow

This paper theoretically examines the effects of water-Al2O3 nanofluid on exergy destruction, exergy efficiency and pumping power in the helically coiled tube heat exchanger under turbulent flow and subjected constant wall condition. The effects of the nanoparticles volume concentration, nanoparticle dimensions, Reynolds number, curvature ratio and dimensionless inlet temperature considered to be the main parameters in this study. It is found that when the Reynolds number increases, dimensionless total exergy destruction decreases. It is observed that by increasing the nanoparticles volume concentration from 2% to 6%, the dimensionless thermal exergy destruction reduces by 3.64% to 20.21 % compared to pure water. Also, it is seen that when nanoparticles dimensions increases, the exergy efficiency increases and pumping power decreases. Finally, the exergy efficiency increases with increasing of curvature ratio and pumping power decreases with increasing of curvature ratio.

Entropy generation of pseudo-plastic non-Newtonian nanofluids in circular duct under constant wall temperature

In this paper the second law analysis of thermodynamic irreversibilities in pseudo-plastic non-Newtonian nanofluids through a circular duct under uniform wall temperature thermal boundary have been carried out for laminar flow condition. This nanofluid consists of sodium carboxymethyl cellulose (CMC)–water and two different types of nanoparticles; namely, CuO and Al2O3. Entropy generation is obtained for various Power law number, various volume concentration of nanoparticles, various dimensionless temperature and various Reynolds number. It is found that with the decreasing Power law number and duct length values, total entropy generation at fixed Reynolds number decreases and with increasing wall temperature values, total entropy generation increases, also entropy generation decreases with increasing volume concentration of nanoparticles