Parr is thrilled to announce the latest addition to our reactor systems, which enables users to determine reaction enthalpy using power compensation calorimetry. This innovative technique offers a direct and intuitive way to quantify process power and calculate the enthalpy of the reaction.

The power compensation calorimetry feature involves a reaction vessel with a circulating jacket that is isothermally controlled. The jacket is typically set to a temperature just below the desired reaction temperature, while the process temperature is regulated by adjusting the power to an electrical heater located inside the reaction vessel. This heater, also known as a compensation or trim heater, automatically varies its electrical power to maintain the desired process temperature as the process heat load changes. The heat liberated or absorbed by the process is determined from the difference between the initial electrical power and the demand for electrical power at the time of measurement. This technique requires no calibration before or during the process and is frequently used to obtain rapid results.

Power compensation calorimeters attain thermal equilibrium more quickly than heat flow or heat balance calorimeters, making them advantageous for measuring heat flow from short-lived reactions. With the ability to study factors influencing reaction mechanisms and kinetics, verify the completion of a reaction in real-time, and establish cooling power needed to maintain safe and effective process conditions, reaction calorimetry provides a wide range of benefits.

The power compensation calorimetry feature requires three fundamental components or subsystems: a jacketed vessel with a constant temperature circulating bath, an appropriately sized and configured trim or compensation heater equipped with a regulated power supply, and a Parr 4871 Process Controller to control and coordinate the overall operation of the system.

To showcase the results of this new feature, we present a plot showing the transient temperature changes in a reactor equipped to perform power compensated calorimetry. The 4547 jacketed reactor used here has an internal volume of 1.2 L and was half full of water. Data were recorded at one minute intervals while the set point bias was toggled 1.5 C. The y-axis is the trim heater power (watts).

Invest in Parr’s reactor systems with power compensation calorimetry feature today to take advantage of this direct and intuitive method for quantifying process power and calculating the enthalpy of the reaction.