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This paper summarises the main results of a research work about the heat transfer enhancement and its theoretical estimation, in the two-phase thermal control with dielectric refrigerant fluids. The authors consider pool boiling applications at atmospheric conditions and without supplementary energy. Two methods are considered to enhance the heat transfer: the use of the finned surfaces and the natural re-circulation of the condensed fluid, pool boiling with controlled return (PBCR). First of all the purpose is to evaluate the possibility of a thermal dissipation comparable with the one obtainable by means of the boiling water at atmospheric pressure, about 1 MW/m2; secondly, to increase the knowledge about the burn-out incipience. A detailed experimental analysis of the burn-out incipience is performed using a single fin. Moreover the objective is to propose theoretical methods to estimate the critical heat flux related to finned surfaces as well as a possible approach to perform a 'nearly optimum' design of fins and fin arrays in pool boiling

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