ABSTRACT
It is imperative that all pressure vessels be equipped with a relief device to prevent the pressure from exceeding the maximum allowable working pressure of the vessel, with the consequent rupture of the vessel and loss of containment of the contents. The design of a relief system begins with an energy balance on the system to determine the rate of energy input from the source. There are a large number of "models" for two-phase flows, both "frozen" and "flashing," for which the two phases are assumed to be in thermodynamic equilibrium. "Frozen" flows involve nonvolatile liquids and noncondensable gases with constant quality, whereas flashing flows involve a volatile liquid and a change of quality as the liquid flashes. If the entering fluid is a subcooled liquid, the initial quality is zero until the pressure in the nozzle drops to the saturation pressure.
