One of the most common PET isotopes, 18F, is mainly produced in liquid targets. The production yield depends linearly on the proton beam current used. However, for a fixed proton-beam energy increasing the current of the proton beam results in depositing increasing amounts of heat into the enclosed water target chamber and eventually in its failure. Hence, understanding the thermodynamics of a water target chamber could lead to a target optimization, removing the maximum amount of heat to balance the pressure, increasing the yield and guaranteeing the stability and durability of the system. Work in modeling the thermodynamic processes in a liquid target has also been per-formed by other groups [1-3] and others such as Steinbach [4] have performed analytical analyses of thermal behavior.