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Critical heat flux (CHF) describes the thermal limit of a phenomenon where a phase change occurs during heating (such as bubbles forming on a metal surface used to heat water), which suddenly decreases the efficiency of heat transfer, thus causing localised overheating of the heating surface. As the boiling surface is heated above a critical ...
Isotope fractionation occurs during a phase transition, the ratio of light to heavy isotopes in the involved molecules changes. When water vapor condenses (an equilibrium fractionation), the heavier water isotopes (18 O and 2 H) become enriched in the liquid phase while the lighter isotopes (16 O and 1 H) tend toward the vapor phase. [4]
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes.
In systems that utilize boiling, the heat transfer rate is significantly higher than if the fluid were a single phase (i.e. all liquid or all vapor). The more efficient heat transfer from the heated surface is due to heat of vaporization and sensible heat.
The classical Stefan problem aims to describe the evolution of the boundary between two phases of a material undergoing a phase change, for example the melting of a solid, such as ice to water. This is accomplished by solving heat equations in both regions, subject to given boundary and initial conditions. At the interface between the phases ...
The former occurs only if all parts are at the same temperature, but interphase heat transfer also occurs when the temperatures of the individual phases are different. If different phases of the same pure substance are present in a multiphase system, interphase heat transfer will result in a change of phase, which is always accompanied by ...
A condenser is designed to transfer heat from a working fluid (e.g. water in a steam power plant) to a secondary fluid or the surrounding air. The condenser relies on the efficient heat transfer that occurs during phase changes, in this case during the condensation of a vapor into a liquid. The vapor typically enters the condenser at a ...
The critical heat flux is the peak on the curve between nucleate boiling and transition boiling. The heat transfer from surface to liquid is greater than that in film boiling. Nucleate boiling is common in electric kettles and is responsible for the noise that occurs before boiling occurs. It also occurs in water boilers where water is rapidly ...