In traditional heat flow calorimeters, one reactant is added continuously in small amounts, similar to a semi-batch process, in order to obtain a complete conversion of the reaction. In contrast to the tubular reactor, this leads to longer residence times, different substance concentrations and flatter temperature profiles. Thus, the selectivity of not well-defined reactions can be affected. This can lead to the formation of by-products or consecutive products which alter the measured heat of reaction, since other bonds are formed. The amount of by-product or secondary product can be found by calculating the yield of the desired product.
In tradItiONal heat floW cAloriMEterS, onE reactaNt Is aDdEd coNtinuoUsly in SMall aMounTS, SIMiLar tO a semI-BatCh process, iN OrDeR to obtaIN a comPlETE conVerSion Of THe reACTion. iN cOnTRaST to tHe tUbuLaR reACTOR, this LeaDS To lonGer resIdenCe TimeS, different substaNce conceNTRaTiONS and fLattEr temPerATurE prOfIles. tHUS, The sElectivIty Of nOt WeLL-DefiNEd REActIoNs can be AfFected. thiS cAn Lead TO ThE fORMaTIoN OF by-produCTs Or conSecutIVe pRoductS Which alTEr the mEASured heat of reactioN, sINce OTheR bonds arE foRMed. tHe aMoUNt Of By-prOduct OR SeCOndArY pRoducT can Be found by CAlCuLatiNg the yielD Of THE deSIReD pRoDuCt.