Authors:G. De Domenico, D. Lister, G. Maschio, and A. Stassi
A simple method for the on-line calibration, in which both the heat transfer coefficient and the heat capacity of the reactor
contents are determined, is described for laboratory scale heat transfer calorimeters. The calorimeter is operated in the
isoperibolic mode for the calibration and a constant power is supplied to a resistor placed inside the reactor. The reactor
heat balance differential equation is used to produce a set of linear simultaneous equations with each data acquisition cycle
giving one equation. The heat transfer coefficient and the heat capacity are obtained from this set of equations by linear
least squares. The application of the calibration procedure is illustrated by experiments in which the heat of reaction is
determined on-line fora simulated reaction with first order kinetics and for the hydrolysis of acetic anhydride.
Authors:C. Ampelli, D. Di Bella, D. Lister, G. Maschio, and J. Parisi
A small ultraviolet-visible absorption spectrometer which uses fibre optic coupled immersion probes has been incorporated
into a laboratory scale reaction calorimeter. The combined instrument has been tried out using the hydrolysis of acetic anhydride
as a test reaction. With the calorimeter operating in the isoperibolic mode good agreement is found for the pseudo-first order
reaction rate constant as determined from spectroscopic and calorimetric measurements. Experiments have been made in order
to follow the reaction indirectly using optical pH measurements with acid-base indicators. The possibility of determining
the temperature dependence of the rate constant in a single experiment has also been investigated.
Using flexible heat flux sensors mounted on the lateral and bottom of outside reactor wall, a new approach is developed for
isothermal calorimetric technique to overcome the disadvantages of heat flow calorimetric methods. Although the proposed system
needs a calibration procedure before or after the reaction completion to evaluate the lateral heat transfer area, the measurement
is versatile and totally independent of the reaction media, jacket fluid, and the variations of heat transfer coefficient.
Knowledge of the variations of the heat transfer coefficient is essential for the effective control and scale up of a reactor
and can be inferred by the new method during the reaction. The stirrer power and the heat loss can be determined easily as
well. No pre-calibration is needed for the sensors and no heating element is applied inside the reactor for temperature control.
Experiments are carried out to validate the performance of the new proposed technique. With the help of a heater, the heat
generated in the reactor is measured at various levels of power input. The predicted heater power inputs are in good agreement
with the corresponding heat inputs. The relative detection limit in the range of 0.8–1 W L−1 is expected for this technique. Using the hydrolysis of acetic anhydride, the heat of reaction at 25°C is determined, which
is within the range reported in the literatures. The capability of the system to deal with the variations in the overall heat
transfer coefficient is also demonstrated using a simulated reaction.