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Emisivita a absorptivita tepelného záření povrchů konstrukčních kovů za velmi nízkých teplot
Musilová, Věra ; Hanzelka, Pavel ; Králík, Tomáš ; Srnka, Aleš
Comparison of thermal radiation properties of surfaces of several metals commonly used in cryogenics is presented. We have measured heat absorbed by a surface of Cu, Al and stainless steel kept at a temperature of about 5 K - 10 K. The source of heat was a parallel black surface placed in a small distance from a tested sample. As a result of our measurement, the dependences of absorptivity on the temperature of the heat radiation source are plotted between 30 K and 140 K. The influence of different types of metal treatment, e.g. chemical and mechanical surface finish and annealing, on radiation heat transfer is presented
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Zařízení pro měření tepelné emisivity při nízkých teplotách
Králík, Tomáš ; Hanzelka, Pavel ; Musilová, Věra ; Srnka, Aleš
In the described device, the thermal emissivity or absorptivity of the sample is measured by substitution of the radiative heat flow between two parallel surfaces by thermal output of a heater. Fast measurements of the mutual emissivity for the range of the temperature of the radiating surface 25 K - 150 K are possible. The absorbing surface has a temperature between 5 K and 10 K when LHe is used as cryoliquid. The desired measurement sensitivity is 1 mK for temperature and 0.1 mikroW for heat power, respectively. The diameter of the whole device is 50 mm and so it is possible to use a commercial Dewar can for the cooling. The form of the sample is a circular plate 40 mm in diameter and 1 mm in thickness with one tested side. The emissivity and its temperature dependence for various surface treatments can be checked immediately before application in a cryogenic system
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