An endothermic reaction is a reaction that absorbs heat in order to take place. My chemistry book states it specifically as "a process in which heat flows from the surroundings into the reaction system." An easy way to identify this is through the sign of delta H for the equation. If it is positive, the reaction is endothermic. EX: When you mix ammonium nitrate and water (the stuff inside of "cold packs"), an endothermic reaction takes place. The reaction absorbs heat making the surrounding area feel colder (thus making "cold packs" function the way they do). Check this weblink for getting complete analysis.
Is this a transient analysis? If so you can calculate the amount of energy released / absorbed over time. Enter the change in Q over time (Heat Source / Parameters Q / dependency). Will this work for your application?