Thermal inertia is a term commonly used to describe the observed delays in a body's temperature response during heat transfers. The phenomenon exists because of a body's ability to both store and transport heat relative to its environment. Since the configuration of system components and mix of transport mechanisms (e.g. conduction, convection, radiation, phase change) vary substantially between instances, there is no generally applicable mathematical definition of closed form for thermal inertia.[1]
Bodies with relatively large mass and heat capacity typically exhibit slower temperature responses. However heat capacity alone cannot accurately quantify thermal inertia. Measurements of it further depend on how heat flows are distributed inside and outside a body.
Whether thermal inertia is an intensive or extensive quantity depends upon context. Some authors have identified it as an intensive material property, for example in association with thermal effusivity. It has also been evaluated as an extensive quantity based upon the measured or simulated spatial-temporal behavior of a system during transient heat transfers. A time constant is then sometimes appropriately used as a simple parametrization for thermal inertia of a selected component or subsystem.
- ^ Sala-Lizarraga, Jose; Picallo-Perez, Ana (2019). Exergy Analysis and Thermoeconomics of Buildings. Elsevier. pp. 272–273. doi:10.1016/B978-0-12-817611-5.00004-7. ISBN 9780128176115. S2CID 210737476.