Hydrothermal performance and irreversibility production of distilled H₂O flowing in outwardly-corrugated converging pipes

Abstract

The study of performance parameters that characterize the convective heat transfer performance (CHTP) and entropy production rates (EPR) of fluids is of great importance in science and engineering due to its widespread applications in the design of new thermal devices. This study considers the turbulent CHTP and EPR of distilled ${\mathrm{H}}_2\mathrm{O}$ flowing in outwardly-corrugated converging pipes (OCCPs) and investigates the influence of the diameter ratio DR ($1\le \mathrm{\text{DR}}\le 2$) on the behavior of performance parameters against the Reynolds numbers (Re) within the range (${5.0\times 10}^3\le \mathrm{\text{Re}}\le {5.0\times 10}^4$). The governing equations and boundary conditions are solved with the use of SST $k-\omega$ turbulence model. The considered OCCP is designed such that its average diameter is 0.03m while its normalized length is 26.6. It is obtained that increasing DR enhances the average Nusselt number (Nu), Poiseuille number (fRe), and EPR whereas the reverse is the case for thermal effective number ($I^G$), Bejan number (Be), and performance evaluation criterion (PEC). At $\mathrm{\text{Re}}={2.0\times 10}^4$ in OCCPs of DR = 1.00, 1.25, 1.50, 1.75, and 2.00, EPR is increased by factors 0.88, 1.42, 2.64, 4.84, and 9.61; fRe is improved by factors 3.39, 8.54, 16.27, 27.74, and 49.22; and Nu is enhanced by factors 1.28, 1.31, 1.34, 1.37, and 1.43, respectively. The enhancement is attributed to the flow acceleration, vortices production, and high mixing rate of the hot fluid near the wall with the cold fluid at the core fluid zone. Finally, and among other things it is revealed that the OCCPs of DR = 1.00, 1.25, and 1.50 are advantageous ($I^G>1$) over the straight tube within the range $5\times {10}^3\le \mathrm{\text{Re}}<2.25\times {10}^4.$

Keywords:

• Converging pipe
• hydrothermal performance
• irreversibility production
• outward corrugation
• turbulent flow

Disclosure statement

No potential conflict of interest was reported by the author(s).