Determination of Temperature Distributions for the Sky Based on the Results of Measurement with an Infrared Camera
The surroundings of objects in an open atmospheric space usually consist of a hypothetical surface of the sky and the surface of the ground. The aim of thermovision examination of objects located in open atmospheric space, especially buildings, is to determine the amount of heat loss or to assess the insulation quality parameters of walls, roofs and other building partitions. The tested surfaces, including elements of the outer shell of buildings, are often located at different angles to the ground surface and the sky. For the needs of thermovision testing of the considered objects and calculations concerning the radiation heat transfer, it is necessary to know the radiation parameters of the sky. These parameters include the equivalent radiative ambient temperature needed for thermovision measurements (including the temperature of the sky and the ground) and the overall radiative ambient temperature, which determines the heat loss by radiation from the tested surface. The article describes the method of determining the values of these temperatures on the basis of measuring the temperature of the sky with the use of a long-wave infrared camera and calculations. In order to verify the developed method, the results obtained with the use of the above-mentioned method were compared with the results obtained with the use of a pyrgeometer. The verification comprised the comparison of the heat flux of radiation from the sky, calculated on the basis of infrared camera measurements, with the energy flux emitted by the sky and measured with a pyrgeometer. The result of the verification is satisfactory.