The present study investigates the influence of variable viscosity of temperature-dependent fluids on the laminar heat transfer and friction factor in a 2:1 rectangular duct. The H1 thermal boundary condition corresponding to axially constant heat flux and peripherally constant temperature was adopted for a top-wall-heated configuration. The governing conservation equations of mass, momentum, and energy were solved using a finite volume method, and the range of the Prandtl number was from 7 to 15,000. The present numerical results of local Nusselt numbers for FC-77 (a dielectric fluid) and oil showed 70-80% enhancement over those of a constant property fluid and 40-50% enhancement over water, and gave excellent agreement with recent experimental results. The heat transfer enhancement from the heated top wall was due to an increased velocity gradient coupled with decrease of viscosity near the wall. The study proposes a new correlation for local Nusselt numbers in the 2:1 rectangular duct, which covers both thermally developing and thermally fully developed regions. Consequently, a temperature-dependent viscous fluid with a non-circular duct is proposed for use in the design of a liquid cooling module for the computer industry and in compact heat exchangers in general.
ASJC Scopus subject areas
- Mechanical Engineering