On the Conditions of Incipient Subcooled-Boiling with Forced Convection

Generally it is possible to start the boiling at the surface temperature of a heated wall somewhat exceeding the saturated temperature of the liquid, and the heat flux of initial boiling varies depending on the fluid temperature, liquid velocity, system pressure, surface condition of the heated wall, and so on. In this paper, an analytical consideration was tried to make clear the conditions of incipient subcooled-boiling with forced convection, and the equation to estimate the heat flux under that condition was determined. By comparing with the authors' data at atmospheric pressure or the experimental data of previous investigators at higher pressure, it is known that the analytical results agree very well with experimental ones. The relation to estimate the conditions of incipient boiling is as follows ; [numerical formula] where, A : heat equivalent of work, De : hydraulic diameter, Pr : Prandtle number, q : heat flux at incipient boiling condition, γ : latent heat, Ts : saturated temperature, ΔTsub : subcooling, u : velocity, v : specific volume, λ : thermal conductivity, ν : kinematic coefficient of viscosity, σ : surface tension. Suffix ; g : vapour, l : liquid, 0 : value of bulk temperature.