Nucleate Pool Boiling Correlation
Pool boiling is evaporation at a solid surface immersed in a bulk-stationary volume of liquid, where fluid motion is only due to natural convection, by opposition to flow boiling, for which forced convection is considered.
Different regimes of pool boiling may be distinguished, depending on the difference between the surface temperature and the saturation temperature of the boiling fluid:
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When the surface temperature is above the saturation temperature of the fluid by less than 10 K, heat transfer is moderate as it mainly occurs between the surface and the liquid phase of the fluid by convection, due to the formation of isolated bubbles at nucleation sites separating from the surface.
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For a temperature difference above 10 K, more nucleation sites become active. This is called the nucleate boiling regime, at which the heat transfer coefficient can reach much larger values. When temperature difference further increases, it causes interference and coalescence of the bubbles, creation of jets and columns, decreasing fluid motion and convective heat transfer. The critical heat flux value is reached when the effect of these interferences cannot be compensated by an increase of the temperature difference. This happens for a temperature difference of about 30 K for water.