Time Variation of Nucleate Boiling Heat Transfer of Water

Abstract

Boiling heat transfer is greatly affected by ease of bubble formation conditioned by surface quality and contamination of the heating surface. This tendency is represented quantitatively as the proportionality constant ζ=αR/Δθ² where α=coefficient of heat transfer, R=radius of heating surface and Δθ=temperature difference between heating surface and boiling liquid. ζ decreases with time from the initial value ζ₀ to the final value ζ_∞ corresponding to the steady state of boiling. This process can be written ζ/ζ_∞=1+{(ζ₀-ζ_∞)/ζ_∞}e^-kt, k=1.5 1/h It is shown that k is independent of the applied heat flux, surface quality of the heating surface and presence of solute, unless it deposits scale on the heating surface. The cause of the variation of ζ is desorption of adsorbed gas during exposure of the freshly polished heating surface to the atmosphere.