Heat perception and materials
Thermal Effusivity & Contact Temperature Calculator
Thermal conductivity describes how readily heat moves through a material. Thermal effusivity combines conductivity, density and specific heat to describe how strongly a material exchanges thermal energy with another body during transient contact.
Compare two materials
Why effusivity matters during touch
Two objects can sit at the same room temperature yet feel different when touched because the early heat exchange depends on more than temperature alone. A material with greater thermal effusivity can exchange energy with the contacting body more strongly during the initial transient.
Why this is different from conductivity
Conductivity describes heat flow through a material under a temperature gradient. Effusivity combines conductivity with volumetric heat capacity, so it captures both the ability to conduct energy and the ability to absorb or release energy without a large temperature change.
Why this calculator should not be treated as a skin-temperature predictor
Human touch introduces living tissue, finite contact areas, pressure, moisture, circulation and sensory processing. The interface-temperature equation is useful for understanding the material physics behind the sensation, but it cannot predict exactly how cold or warm an object will feel to a person.
Sources and further reading
- Heat exchange between a bouncing drop and a superhydrophobic substrate - includes the semi-infinite-body contact-temperature relation based on thermal effusivity.
- Active IR Thermography Evaluation of Coating Thickness by Determining Apparent Thermal Effusivity - describes thermal effusivity as e = √(ρCk).
Related reading
Explore heat perception, review thermal conductivity, or compare effusivity with thermal diffusivity.