Heat Exchange in Adiabatic Calorimeters

Area of Science:

• Thermodynamics
• Physical Chemistry
• Calorimetry

Background:

• Accurate heat flow measurement is crucial in calorimetry.
• Adiabatic calorimeters aim to minimize heat exchange with surroundings.
• Understanding transient heat flow is key to improving calorimeter design and accuracy.

Purpose of the Study:

• To describe heat flow in adiabatic calorimeters using linear partial differential equations.
• To analyze and minimize heat exchange errors in intermittent heating methods.
• To differentiate and account for various heat exchange effects in adiabatic calorimetry.

Main Methods:

• Mathematical modeling of heat flow using linear partial differential equations.
• Analysis of transient heat exchange during heating periods.
• Comparison of intermittent and continuous heating methods.
• Experimental design for accounting for heat exchange effects.

Main Results:

• Transient heat exchange at the start and end of heating can be canceled in intermittent calorimetry.
• Remaining heat exchange is consistent between intermittent and continuous heating.
• Heat exchange can be attributed to shield-environment gradients and heater-induced temperature rises.
• Shield-environment effects are corrected by fore/after periods or heating rate variation.
• Heater effects can be corrected using empty calorimeter measurements.

Conclusions:

• Intermittent heating offers a method to cancel transient heat exchange errors in adiabatic calorimeters.
• A comprehensive model accounts for residual heat exchange, improving thermal property measurements.
• The study provides a framework for accurate calorimetric measurements by addressing heat exchange phenomena.