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EN
During the temperature measurements by means of infrared camera the temperature of surrounding elements must be known. In the case of thermovision inspections of the objects exposed to open air space, the surroundings consists of two elements, it is the ground and hypothetical sky surface. The sky temperature measured by long-wave IR camera is of apparent character because it expresses the thermal radiation of the sky within the spectral operational range of this camera i.e. 7.5÷13 μm. The abovementioned spectral range is coincident with so called atmospheric window within which the thermal radiation of the sky is relatively low. The emissivity of atmosphere within this window is low in the central part and high near the limits of the aforementioned range. In relation with the detector characteristic of the IR camera it causes underestimation of the measured sky temperature. This work deals with the analysis of influence of the IR camera detector characteristic on the results of determination of sky temperature and its thermal radiation intensity.
PL
Znajomość cieplnej emisji nieboskłonu jest niezbędna w obliczeniach radiacyjnej wymiany ciepła pomiędzy obiektami w otwartej przestrzeni i otoczeniem. Praca dotyczy zastosowania wyniku pomiaru temperatury nieboskłonu za pomocą kamery termowizyjnej do określenia gęstości cieplnego promieniowania nieboskłonu. Temperatura nieboskłonu jest temperaturą pozorną, wynikającą z intensywności jego promieniowania. Artykuł dotyczy problemu pomiaru tej temperatury i zawiera propozycję jego rozwiązania.
EN
The work deals with measurement of the apparent temperature of the sky with use of a long-wave (LW) infrared camera and determination of the sky thermal radiation intensity. Convective and radiative heat transfer takes place between a heat pipeline and the surrounding on the external pipeline shell. In the case of a low temperature of the sky, the radiation heat exchange is very intensive and the temperature of the top part of the horizontal pipeline is much lower than the bottom part and can drop below the atmospheric air temperature. The aforementioned phenomenon causes difficulties during evaluation of the quality of the pipeline thermal insulation and determination of the pipeline heat losses. The occurrence of this phenomenon strongly depends on the intensity of thermal radiation of the sky. The paper contains a description of the method for determination of the sky thermal radiation intensity on the basis of sky temperature measurement with the use of an LW infrared camera. To verify the developed method, the results obtained with the use of the LW infrared camera and measurement results obtained by means of a pyrgeometer were compared. The result of this comparison is quite satisfactory.
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