A ceramic porous wick is proposed in this book as an alternative to wicks made of sintered metal and plastic materials for applications in LHPs and CPLs. A theoretical and experimental analysis is presented. First, the heat and mass transfer in a flat capillary evaporator formed by a single or double-layered porous wick is analyzed. The wick has a shape of a flat disc and it is assembled between the liquid and vapor channels. An external heat input is applied in the upper surface of the wick, where the working fluid evaporates. The mass and heat transfer are modeled using the mass and energy macroscopic conservation equations. The models developed allow to verify the effect of design variables, such as working fluids, dimensions, permeability, average pore radius and thermal conductivity of the wick, in the performance of the capillary evaporator. For the experimental analysis, performance tests of two LHPs using acetone and water as working fluids were carried out for power inputs up to 25 W and performance tests of one CPL using water were carried out for power inputs up to 30 W.