Forced convection behavior of a dielectric fluid (FC-77) in a 2:1 rectangular duct

The present study numerically investigates the effect of variable viscosities of water and a dielectric fluid (FC-77) on the heat transfer and friction factor for laminar flow in a rectangular channel. The present numerical results of local Nusselt numbers for FC-77 significantly exceed the value obtained with a constant-property fluid or water. The increase in the Nusselt numbers for FC-77 results from two factors: the low thermal conductivity of FC-77 and an increased velocity gradient caused by decreasing viscosity near the top wall. However, the actual heat transfer rate for FC-77 is much smaller than for water because of its low thermal conductivity. Also, the present study examines the wisdom of using dimensionless and dimensional heat transfer coefficients in relation to the design of liquid-cooling module involving dielectric fluids or water.