Evaporation by Natural Convection

[摘要] From the analogy between heat transfer and evaporation, the rate of evaporation from a finite pan by natural convection was obtained as follows:where E is the rate of evaporation in g•cm-2•see-1, C0, C∞ are vapour concentrations at the surface of water and in the air respectively, _??_θ0-θ∞, θ0, θ∞ being temperatures at the surface of water and in the air respectively, d is diffusivity, _??_; kinematic viscosity, β; expansion coefficient of air, g; acceleration of gravity and x is the radius of the pan in cm.Experiments were carried out by using a pan of radius 1.83cm. The range of _??_=θ0-θ∞ observed was from 0.1° to 50°C, in which θ∞ was about 20°C. The experimental result was expressed by while the theoretical formula for the pan at θ∞=20°C isBoth results agree fairly well, but the experimental result gives about 21% smaller rate of evaporation than the theoretical formula.

[学科分类] 大气科学