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Resistance in Thermal Systems. 4.4. Thermal Resistance. a measure of an object’s ability to oppose heat transfer. Rthermal = -ΔT/Q (Thermal resistance = temperature drop divided by heat flow rate)—Compare to fluid and electrical—Rfluid = -ΔP/V.
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Thermal Resistance • a measure of an object’s ability to oppose heat transfer. • Rthermal = -ΔT/Q (Thermal resistance = temperature drop divided by heat flow rate)—Compare to fluid and electrical—Rfluid = -ΔP/V
Rthermal = Δx/kA (Thermal resistance = change in thickness of slab divided by constant · Area) • ***the ratio of the prime mover to a flow rate
Units—°C /cal/s or °C·s/cal—°F/Btu/s or °F·s/Btu • Temperature drop across a slab is proportional to the heat flow rate.
Thermal Resistance in Series • Heat flows through each resistance, one at a time, just like current flows through each resistance in a series circuit. • Rtotal = R1 + R2