Functional forms for mixed convective heat transfer and evaporation from an air-water interface were obtained. To obtain these functions, heat transfer and evaporation rates from the air-water interface of an evaporating body of water were quantified in a wind/water tunnel in the presence of an oleyl alcohol monolayer on the water surface. The Nusselt (Nu) and Sherwood (Sh) numbers, parameterizing the dimensionless heat and mass transfer respectively, for transport from the water bulk to air were expressed as functions of the air side Rayleigh (Ra) and Reynolds (Re) numbers. The Nu and Sh were calculated for a range of Ra from 1.1 × 107 to 4.1 × 107 and a range of Re from 0 to 3.5 × 105. Power law Nu(Ra) and Nu(Re) relationships parameterizing natural and forced convective heat transfer respectively were then obtained as were Sh(Ra) and Sh(Re) relationships parameterizing natural and forced convective evaporation. Mixed convective Nu(Ra, Re) and Sh(Ra, Re) functions were formulated using a vectorial additive model having an exponent of four. These functions predicted the experimentally obtained Nu(Ra), Nu(Re), Sh(Ra) and Sh(Re) relationships with reasonable accuracy. From the Nu(Ra), Nu(Re), Sh(Ra) and Sh(Re) results as also from the results of the mixed convective equations, it was concluded that the mixed convective regime lay between 1 3 m/s i.e. 0.6× 105 < Re < 2.1× 105 for both heat and mass transfer. To obtain repeatable results and for these results to be applicable to field conditions, a monolayer of oleyl alcohol was applied to the water surface to maintain spatially and temporally consistent surface conditions. An IR camera was used to visualize the surface flow and to judge the homogeneity of the surfactant film. It was found that the oleyl alcohol monolayer applied to the water surface formed a homogenous surfactant film thus ensuring consistent conditions for all experiments.

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Heat transfer in electronic equipment, 1991

Citations

Mixed convective heat transfer and evaporation at the air-water interface

References

Mixed convective heat transfer and evaporation at the air-water interface

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