Temperature oscillating mini-calorimeter

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 T_r, 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).