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The relationship between thermal conductivity and conductance is analogous to the relationship between electrical conductivity and electrical conductance. Thermal resistance is the inverse of thermal conductance. [6] It is a convenient measure to use in multicomponent design since thermal resistances are additive when occurring in series. [7]
The SI unit of absolute thermal resistance is kelvins per watt (K/W) or the equivalent degrees Celsius per watt (°C/W) – the two are the same since the intervals are equal: ΔT = 1 K = 1 °C. The thermal resistance of materials is of great interest to electronic engineers because most electrical components generate heat and need to be cooled.
Interfacial thermal resistance is a measure of an interface's resistance to thermal flow. This thermal resistance differs from contact resistance, as it exists even at atomically perfect interfaces. Understanding the thermal resistance at the interface between two materials is of primary significance in the study of its thermal properties.
Installed faced fiberglass batt insulation with its R-value visible (R-21) [1]. The R-value (in K⋅m 2 /W) is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive [2] flow of heat, in the context of construction. [3]
The thermal contact conductance coefficient, , is a property indicating the thermal conductivity, or ability to conduct heat, between two bodies in contact. The inverse of this property is termed thermal contact resistance.
Electrical conductivity of water samples is used as an indicator of how salt-free, ion-free, or impurity-free the sample is; the purer the water, the lower the conductivity (the higher the resistivity). Conductivity measurements in water are often reported as specific conductance, relative to the conductivity of pure water at 25 °C.
Measurements of thermal conductivity are also subject to contact resistance, with particular significance in heat transport through granular media. Similarly, a drop in hydrostatic pressure (analogous to electrical voltage ) occurs when fluid flow transitions from one channel to another.
So that practical clothing may be described conveniently by a range of small integers, the unit of thermal resistance, to be called the “tog”, is the resistance that will maintain a temperature difference of 0.1°C. with a flux of 1 watt per square metre, or in more practical terms, 10°C. with a flux of 1 watt per square decimetre.