ABSTRACT
The onset of thermal crisis consists of an abrupt worsening of heat transfer between a heating wall and a coolant liquid, generally with undesired consequences. In systems with imposed heat flux, the consequent sharp increase of temperature may lead to wall fusion or to its deterioration. A pool-boiling situation is considered, with a horizontal heating wall submerged in a liquid at saturation temperature. The main parameters which influence thermal crisis in pool boiling are pressure, subcooling and heater geometry. Forced convection critical heat flux is generally correlated to the following parameters: quality, subcooling, mass velocity, pressure, duct geometry and orientation, flow direction, and overall thermal power. Upward and downward flows have obviously different phase distributions and, as a consequence, different qualities. The Helmholtz instability criterion refers to the equilibrium of two counter-flowing streams of fluids of different densities, separated by an interface run by moving waves.
