We have used the transient hot-wire technique to make absolute measurements of the thermal conductivity of dry, CO2-free air in the temperature range from 312 to 373 K and at pressures of up to 24 MPa. The precision of the data is typically ±0.1%, and the overall absolute uncertainty is...
Most of the theoretical or semi-theoretical expressions proposed are based on Debye's treatment of heat conductivity (1914), which leads to the equation: (17.4)λ=Λcvρul where cv = specific heat capacity at constant volume (J (kg K)−1); u = velocity of elastic waves (sound ...
In several earlier issues ofElectronics Cooling, I discussed the thermal conductivity of air as a function of temperature and pressure. Therein, it was stated that the temperature dependence cannot be neglected, but that the pressure dependence, under ‘normal’ conditions, is virtually absent...
Online calculator with figures and tables showing air thermal conductivity vs. temperature and pressure. SI and imperial units.
where B is a constant and ΘD is Debye's temperature. This result suggests four criteria for choosing high thermal conductivity materials: (i) low atomic mass, (ii) strong interatomic bonding, (iii) simple crystal structure, and (iv) low anharmonicity. Conditions (i) and (ii) help increase...
air-mediated losses. We find the reduction of the thermal conductivity and its temperature dependence closely correlated with the structure feature size. On the basis of two-phonon Raman spectra, we attribute this behaviour to diffuse (incoherent) phonon-boundary scattering. Furthermore, we ...
2.Physics.a constant that is a measure of a property of a substance, body, or process:coefficient of friction. adj. 3.acting in consort; cooperating. [1655–65; < New Latincoefficient-,s. ofcoefficiēns.Seeco-,efficient] Random House Kernerman Webster's College Dictionary, © 2010 K Dic...
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Natural, biological insulators such as fur and feathers achieve similar effects by dramatically inhibiting convection of air or water near an animal's skin. Light gases, such as hydrogen and helium typically have high thermal conductivity. Dense gases such as xenon and dichlorodifluoromethane have ...
Sapphire is a notable example of variable thermal conductivity based on orientation and temperature, with 35 W/(m·K) along the c-axis and 32 W/(m·K) along the a-axis.[13] Air and other gases are generally good insulators, in the absence of convection. Therefore, many insulating ...