The motivation for this paper comes from the consideration of vertical shell and tube vaporizers where the shell side fluid receives uncontrolled heat input from the hot tube side fluid. The even distribution of tubes in this type of exchanger can result in volumetric boiling, and therefore, significant level swell similar to the situation that occurs during a bulk uncontrolled exothermic reaction in a vessel. Therefore, the pressure relief device on this type of equipment must consider the possibility of two-phase flow. Given this, new simplified equations are derived for the required relieving rate assuming the contents act as a boiling vapor- liquid homogeneous fluid during emergency venting. Unlike previous work in this area, the expressions presented here account for a temperature dependent heat source. Since the homogeneous vessel assumption is employed, the equations are applicable to any indirectly heated equipment whose contained fluid is expected to exhibit homogenous character due to equipment geometry, equipment internals, or simply the fluid properties.

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