Bulletin of JSME · 1964 · 200 citations · 0 references
EngineeringMechanical EngineeringPhysicsFluid DynamicsHeat TransferThermodynamicsBoiling Heat TransferFluid PropertiesHeat ConductionHeat Transfer AnalysisHeat Transfer FundamentalsHeat Transfer In FluidsBoilingForced ConvectionHydraulic DiameterLatent HeatLatent Heat TransferSubcooled BoilingSurface TemperatureThermal Conductivity
Incipient boiling can begin when a heated wall exceeds the liquid’s saturation temperature, with the initial heat flux depending on fluid temperature, velocity, pressure, and wall surface condition. The study analytically determines the conditions for incipient subcooled boiling under forced convection and derives an equation to estimate the associated heat flux. They present a correlation for incipient boiling heat flux that incorporates hydraulic diameter, Prandtl number, latent heat, subcooling, velocity, specific volume, thermal conductivity, viscosity, and surface tension. The analytical predictions closely match experimental data at both atmospheric and higher pressures.
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.