Assessment of Overall Heat Transfer Coefficient Models to Predict the Performance of Laboratory-Scale Jacketed Batch Reactors

Abstract

Heat transfer models for agitated, jacketed, laboratory-scale batch reactors are required to predict process temperature profiles with great accuracy for tasks associated with chemical process development such as batch crystallisation and chemical reaction kinetics modelling. The standard approach uses a reduced model which assumes the system can be adequately represented by a single overall heat transfer coefficient which is independent of time, however the performance of reduced models for predicting the evolution of process temperature is rarely discussed. Laboratory scale (0.5 and 5 l) experiments were conducted using a Huber thermoregulator to deliver a thermal fluid at constant flow to a heat transfer jacket. It is demonstrated that the relative specific heat contribution of the reactor and inserts represent an increasing obstacle for these transient models with decreasing scale. However, a series of experiments implied that thermal losses were the limiting factor in the performance of a single coefficient reduced model at laboratory-scale. A diabatic model is presented which accounts for both thermal losses and the thermal inertia of the reactor vessel and inserts by incorporating a second coefficient and a modified heat capacity term. The mean absolute error in predicted process temperature was thereby reduced by a factor of eight, from 2.4 to 0.3 K, over a 150 min experiment.

Predici as a Polymer Engineers’ Tool for the Synthesis of Polymers via Anionic Polymerization

“…These values of the thermal transmittance correspond to data known from the literature for batch reactors. 67 After the polymerization is started, the thermal transmittance decreases with increasing conversion due to the change of the viscosity.…”

An Integrated Continuous Flow Micro-Total Ultrafast Process System (μ-TUFPS) for the Synthesis of Celecoxib and Other Cyclooxygenase Inhibitors

“…Pyrazole derivatives are conventionally prepared by condensation of a diketone with hydrazine using ethanol or water as a solvent under reflux conditions. , Active pharmaceutical ingredient (API) manufacturing is usually performed at multiple locations in noncontinuous or “batch” synthesis involving extraction, product separation, and formulation. − The main disadvantages of the batch approach include long production times, the high cost of transportation, and the potential disruption of the supply chain. , …”

CFD modelling of conjugate heat transfer in a pilot‐scale unbaffled stirred tank reactor with a plain jacket

“…Mathematical models for heat transfer in batch STRs with various levels of sophistication have been developed in the past. Lumped‐parameter models are the most common type of model used for predicting the variation of process temperature with time, which assumes a perfect mixing leading to a uniform temperature in the vessel at a given instance of time, uniform flow and temperature distribution in the jacket, and a steady state overall heat transfer coefficient. These models also include conjugate heat transfer between the jacket and process side using individual heat transfer coefficients and wall resistance and the thermal inertia of the vessel wall .…”

“…Lumped‐parameter models are the most common type of model used for predicting the variation of process temperature with time, which assumes a perfect mixing leading to a uniform temperature in the vessel at a given instance of time, uniform flow and temperature distribution in the jacket, and a steady state overall heat transfer coefficient. These models also include conjugate heat transfer between the jacket and process side using individual heat transfer coefficients and wall resistance and the thermal inertia of the vessel wall . These assumptions are far from reality and highly inadequate for simulating heat transfer in large‐scale STRs where some regions are mixed better than others, and so the temperature at some positions in the process may be significantly under or over the temperature that would occur in a perfectly mixed system.…”