Calorimetry heat balance

Hub, L. and T. Kupr, "Heat Balance Calorimetry and Automation of the Testing Procedure," in Proceedings of the Runaway Chemical Reaction Hazard Symposium, IBC, London, England (1987). 

The third calorimetric method is called heat balance calorimetry. This is actually not a very well chosen name, because the evaluation of measurements according to the previously described calorimetric methods are based on the heat balance in absolutely the same way as this method is. However, this name has established itself world-wide. 

Kramer,S. (2005) Heat Balance Calorimetry and Multirate State Estimation Applied to Semibatch Emulsion Copolymerisation to Achieve Optimal Control. PhD Thesis, University of Dortmund. 

In heat-balance calorimetry, eqs. (71) and (72) are coupled with the energy balance in the jacket to produce Eq. (73), where is the mass of cooling fluid in the jacket, the mass flow rate of cooling fluid in the jacket, its specific heat capacity, ive the inlet jacket temperature and the outlet jacket temperature. 

Heat-balance calorimetry allows the simultaneous estimation of U and Qj., provided that — Tas could be accurately measured. Therefore, heat-balance calorimetry is best suited for large-scale industrial reactors because a significant difference between the jacket inlet and outlet temperatures is necessary, and this is the case in industrial reactors. The advantage of this approach is that a-priori information of the overall heat-transfer coefficient is not necessary and hence it is more robust and reliable than heat-flow calorimetry. 

Two methods are used to compute the heat of reaction, Q, depending if only Equation 7.1 is solved, namely, the heat balance of the reactor content, or either Equations 7.1 and 7.2 are simultaneously solved [6]. The first method is known as heat flow (flux) calorimetry and the second as heat balance calorimetry. 

Different alternatives have been presented to circumvent this issue in heat flow calorimetry. A priori off-line determination of the dependence of UA [9], adaptive calorimetry using an additional off-line measurement [12] and cascade state estimation observers [14] proven to work, will be discussed in the following section. Obviously, another alternative is to use heat balance calorimetry and to solve the energy balances given by Equations 7.1 and 7.2 simultaneously to compute the evolution of the heat of reaction, Qp and the overall heat transfer coefficient, UA. This approach will be addressed in Section 7.2.3. 

Heat balance calorimetry is based on an energy balance on the cooling jacket using Equation 7.2 in order to identify the term that can then be used in Equation 7.1 to calculate Q. The energy balance on the cooling jacket in Equation 7.2 can be simplified in many cases using a pseudo-steady-state approximation and substituting Equation 7.10 for the difference in heat flow in and out of the jacket ... 

Contrary to lab reactors in which heat balance calorimetry cannot be applied, because the large flow rates of the heating/ cooling fluids makes T. T., in industrial scale reactors,... 

Eurthermore, with certain reasonable approximations, heat balance calorimetry can be used with a minimum of effort in industrial reactors. The heat loss term in the energy balance, <2i ss is typically proportional to the surface area of the reactor (Eq. 7.11). Since the specific surface area per unit volume in large reactors is very small, the loss term, even if nonzero, is small with respect to the heat generation term. This means that as a first approximation, if the reactor is operating at a steady state or under isothermal conditions, one can simplify the energy balance to... 

Esposito M, Sayer C, Hermes de Araujo PH. In-line monitoring of emulsion polymerization reactions combining heat flow and heat balance calorimetry. Macromol React Eng 2010 4 682-690. 

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