Module 1.3 Thermal Properties

Maximum Service Temperature

• Maximum usable temperature for a material; beyond which it may degrade or lose performance (“fail”)

• It is the highest temperature at which a material can operate safely and effectively without experiencing significant degradation or failure.

• Often much lower than melting temperature

Heat Capacity (Cₚ) and Units

• The amount of heat required to change the temperature of a unit mass of a substance by one degree Celsius at constant pressure. It is an important property that indicates how much thermal energy a material can store.

• J / (“amount” * K)

Thermal Conductivity (Λ) and Units

• Speed of heat flow at a steady state

• Amount of heat passing through a unit area per unit time under a temperature gradient

• Fourier’s Law: Q = - Λ * (ΔT/Δx)

• Q means heat flux

• Units: W / (m*K)

Thermal Diffusivity (Dₜₕ) and Units

• Ratio of thermal Conductivity divided by heat capacity

• Describes how long it takes to heat a material in transient state

• Units: m²/s

Thermal Expansion Coefficient (α) and Units

• Coefficient of Thermal Expansion (CTE)

• Change in volume of material with change in temperature

• High CTE = more expansion

• Low CTE = less expansion

• ΔL = αLᵢΔT

• Units: 1/K