This paper analyzes the operational characteristics and limits of a loop heat pipe (LHP) with Rat porous elements in the condenser and evaporator. A mathematical model, based on the nodal method, was developed to simulate the thermal and hydrodynamic behavior of this: specific type of LHP. Previously, the model was verified and validated by experiential data [I. Muraoka. F.M. Ramos, V. Vlassov. Int. Commun. Heat Mass Transfer 25 (1998) 1085]. The dryout failure mechanisms of this device were investigated and its operational limits identified in terms of the heat load dissipated in the evaporator and the heat sink temperature at the condenser. Three distinct operational regimes were identified and characterized, taking into account the volume of vapor in the liquid core of the evaporator and the capillary pressure limit.