Why are the Units for Thermal Conductivity W/mK?
Posted by jpluimers on 2026/08/21
Related to Thermal conductivity – Wikipedia and List of thermal conductivities – Wikipedia is [Wayback/Archive] Why are the Units for Thermal Conductivity W/mK?
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The transfer of heat energy is defined as heat flux, Q. By definition, this is the flow of heat energy through a defined area over a defined time. So, the units for Q are Joules (energy) divided by area (square meters) and time (seconds). Joules/(m^2∙sec). Since power is defined as energy divided by time and 1 Watt is equal to 1 Joule/second, Q can also be expressed as Watts/m^2 .
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Fourier’s Law defines the ability of a specific material to transfer heat. It defines the heat flux, Q, through a material in terms of the cross-sectional area through which the heat energy transfer occurs, A, and the temperature gradient over which the transfer occurs, ∆T/∆x:
Q=-κA ∆T/∆x (1)
k is the proportionality constant for this relationship, known as the thermal conductivity. It is a characteristic property of a material. The units of the individual components of Equation (1) can be written out (with Q defined in terms of power):
Watts =κ∙m^2∙K/m (2)
When the units of length are cancelled out, Equation (2) becomes:
Watts/m=κ∙K (3)
Solving for the thermal conductivity, k:
κ=Watts/(m∙K) (4)
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Via [Wayback/Archive] w/mk – Google Search
Because of [Wayback/Archive] Aukuoy 3 Pack 12.8W/mK Thermal Conducting Pads, 100 x 100 x 0.5mm/1mm/1.5mm High Temperature Heat Resistant Silicone Grease Thermal Pads for PC Laptop Heat Sink CPU GPU LED SSD IC SMD Cooler: Amazon.de: Computer & Accessories.
Though I doubt the Silicone Grease used has indeed such a high Thermal Conductivity of 12.8 W/mK. Given the specifications at [Wayback/Archive] Thermal Paste (MG Checmicals) I estimate it more to be like 1.28 W/mL.
–jeroen
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