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Thermal resistance
Intermediate
Resistances add like resistors in series.
R = L/kAR = L/kA, and for layers in series the resistances add. Insulation aims for large R.
Double glazing traps a low-k air gap.
Heat flow = ΔT/R_total.
In more detail
Thermal resistance measures how much a material or layer resists heat flow. For a slab, R = L/(kA), and heat flow is the temperature difference divided by R.
Real-world uses
- Building insulation is rated by thermal resistance, often called the R-value.
- Electronic heat sinks are designed to have low thermal resistance.
- Builders calculate the total thermal resistance of a wall made of brick, insulation and plaster to estimate heat loss.
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Frequently asked questions
Is high resistance good for insulation?
Yes. High thermal resistance means less heat flows through the material.
How does thickness affect resistance?
Thicker layers have higher resistance because heat must travel further.
How do thermal resistances combine in a wall?
Layers in series add their resistances, just like resistors in a circuit.
Related topics in Heat & Thermodynamics
Phase diagrams · Triple and critical points · Conduction · Convection · Radiation · Stefan–Boltzmann law