A complete anal. of the heat flow equation in reaction calorimetry with supercrit. fluids is presented. An esp. developed reaction calorimeter is employed to study the challenges introduced by the supercrit. state of the reaction mixt. and the particularities that they generate in the calorimetric calcns. As a model reaction the free radical dispersion polymn. of Me methacrylate is chosen. Each term of the heat flow equation is optimized with special attention to the accumulation term and the injection term. The overall heat transfer coeff., being the most important variable of the heat flow equation, is estd. using four different approaches, both theor. and exptl. Moreover, the injection phase of addnl. reactants is shown to generate undesirable temp. oscillations and an optimized injection strategy is found to eliminate the erroneous calorimetric calcns. As a result the enthalpy of reaction and the heat released by the reaction are very accurately estd.