You would really need the isothermal calorimetry data at several temperatures to compute an activation energy. Then you can apply the basic principles of chemical engineering to numerically integrate over time the heat generation due to the reactions. You will need to specify the boundary conditions and geometry of your specimens. This can be done fairly straightforward in COMSOL or other 3-D computational packages. See the publications by Emilio Hernandez-Bautista that are available from his ResearchGate page and were part of his Ph.D. thesis