NOVELTY - Fluid dielectric coolant (A) comprises an emulsion comprising a polar internal phase (comprising an azeotropic mixture) and a hydrocarbon external phase, where the azeotropic mixture includes one or more polar compounds such as water and/or alcohol.    USE - (A) is useful in evaporative cooling process of fuel cells (claimed).    ADVANTAGE - (A) insulates areas of the fuel cell stack having high electric potential from those of low potential, and eliminates any performance loss caused by shunt currents on the header area of the stack, as well as hydrogen and oxygen evolution and plate dissolution. Consequently, corrosion inhibitors need not be added to prohibit oxygen degradation of fuel cell components.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a fuel cell configured to react fuel with oxygen to generate an electric current and at least one reaction product comprising an electrochemical catalytic reaction cell configured to include a fuel flowpath, an oxygen flowpath, and a coolant flowpath fluidly decoupled from the fuel flowpath and the oxygen flowpath, and the coolant flowpath comprising a coolant isolation manifold, where the coolant isolation manifold includes (A); and    (2) a method for cooling a fuel cell comprising providing a fuel cell configured to react fuel with oxygen to generate an electric current and at least one reaction product, where the reaction product is waste heat, configuring the fuel cell to comprise an electrochemical catalytic reaction cell configured to include a fuel flowpath, an oxygen flowpath, and a coolant flowpath fluidly decoupled from the fuel flowpath and the oxygen flowpath, configuring the coolant flowpath to define a coolant isolation manifold, the coolant isolation manifold including an inlet, an outlet and (A); providing a recirculation assembly comprising a recirculation flowpath, a pump, and a radiator and configuring the recirculation assembly so that the recirculation flowpath fluidly connects the coolant isolation manifold inlet and outlet; evaporating the polar internal phase in the coolant isolation manifold, where the latent heat of the polar internal phase draws the waste heat from the fuel cell producing a heated vapor; circulating the heated vapor from the coolant isolation manifold outlet to the radiator via the recirculation flowpath, where the heated vapor is cooled and condensed to form a condensed liquid; and re-emulsifying the condensed liquid in the fluid dielectric coolant and returning the fluid dielectric coolant to the coolant isolation manifold inlet.