Temperature Oscillating mini-calorimeter

Abstract

A small scale (100 mL) calorimeter is developed. It includes a glass vessel submerged in a thermostatic bath, a compensation electrical heater, and a control system. The typical operation mode consists on introducing the solvents and part of the reactants into the vessel, to stabilise a temperature of the bath (T _j) some degrees below the desired process temperature (T _p) and to adjust the reaction mass temperature (T _r) to T _p using the electrical heater. An oscillating set point is established for Tr, which produces an oscillating response of the applied compensation power (Q _c). Finally, the rest of reactants are dosed to the vessel. A small deviation of T _r and T _p is observed. Even though it can be avoided improving the tuning of the controller, it can be useful for enhancing the calculation of the heat capacity of the reaction mixture (C _P). The signals of T _r, Q _c and T _j are processed on-line using the FFT (Fast Fourier Transform) method as the mathematical tool used to analyse the data obtained, producing accurate values of the heat evolved (Q _c) by the process, the heat transfer coefficient (UA), and the heat capacity of the reaction mixture (C _P).