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Conditions for the use of infrared camera diagnostics in energy auditing of the objects exposed to open air space at isothermal sky

Kruczek T.

Archives of Thermodynamics

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2015

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Vol. 36, no. 1

67--82

EN

Convective and radiation heat transfer take place between various objects placed in open air space and their surroundings. These phenomena bring about heat losses from pipelines, building walls, roofs and other objects. One of the main tasks in energy auditing is the reduction of excessive heat losses. In the case of a low sky temperature, the radiation heat exchange is very intensive and the temperature of the top part of the horizontal pipelines or walls is lower than the temperature of their bottom parts. Quite often this temperature is also lower than the temperature of the surrounding atmospheric air. In the case of overhead heat pipelines placed in open air space, it is the ground and sky that constitute the surroundings. The aforementioned elements of surroundings usually have different values of temperature. Thus, these circumstances bring about difficulties during infrared inspections because only one ambient temperature which represents radiation of all surrounding elements must be known during the thermovision measurements. This work is aimed at the development of a method for determination of an equivalent ambient temperature representing the thermal radiation of the surrounding elements of the object under consideration placed in open air space, which could be applied at a fairly uniform temperature of the sky during the thermovision measurements as well as for the calculation of radiative heat losses.

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Wpływ temperatury otoczenia badanego obiektu na wynik termowizyjnego pomiaru temperatury

Kruczek T.

Napędy i Sterowanie

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2010

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R. 12, nr 5

121-124

PL

Termowizyjna technika pomiaru temperatury znalazła wiele zastosowań nie tylko w różnych dziedzinach nauki i ogólnie w diagnostyce cieplnej, ale również jako narzędzie pomiarowe w systemach sterowania i kontroli jakości produktów oraz przebiegu procesów technologicznych.

EN

Several important parameters influence the results of thermovision measurement of the temperature. Among these parameters the ambient temperature may be specified. The surrounding of the object examined usually consists of several elements. The method of expressing the radiation influence of these elements on measurement result by means of one ambient temperature has been presented. Additionally, for evaluating sensitivity of the measurement results to the accuracy in the determination of the ambient temperature a method has been developed and numerical calculations have been carried out.

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Wyznaczanie radiacyjnej temperatury otoczenia przy pomiarach termowizyjnych w otwartej przestrzeni

Kruczek T.

Pomiary Automatyka Kontrola

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2009

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R. 55, nr 11

882-885

PL

Jednym z parametrów wpływającym na wyniki termowizyjnego pomiaru temperatury jest temperatura otoczenia. W przypadku pomiarów w otwar-tej przestrzeni (budynki, rurociągi i in.) otoczenie składa się z dwóch elementów: nieboskłonu i gruntu. Elementy te mają na ogół różne tempe-ratury. W pracy przedstawiono sposób pomiaru temperatury nieboskłonu, a następnie metodę wyznaczania temperatury izotermicznego otoczenia badanego obiektu zastępującego układ dwóch elementów otoczenia o różnych temperaturach: podłoża i nieboskłonu. W oparciu o opracowany model przeprowadzono obliczenia numeryczne, a wyniki przedstawiono na wykresach. Umożliwiają one określenie zastępczej temperatury otoczenia przy pomiarach termowizyjnych w otwartej przestrzeni.

EN

During the thermovision inspection a few important parameters influence the results of temperature measurements. Among these parameters the emissivity of surface under consideration as well as the temperature of the ambient elements can be specified. In the case of overhead heat pipelines, convective and radiative heat transfers take place between thermal pipeline and its surroundings. Generally, the ambient of the external overhead pipeline consists of two surfaces: hypothetical sky and ground surface, Figs. 1, 2a. The method concerning the determination of apparent temperature of the hypothetical sky surface has been developed. The method is based on radiosity balances formulated for each considered element [1]. In this method the radiation of atmosphere towards the ground surface is substituted by the radiation of the assumed artificial surface, Fig. 1. As a result, the ambient system of two surfaces having different temperatures is obtained, Fig. 2a. Next, this system is converted into one-surface system and a method of expressing the radiation influence of these elements on the measurement result by means of one ambient temperature is developed. The aforementioned temperature is called an equivalent ambient temperature and can be calculated on the basis of equation (22). Numerical calculations have been carried out for the assumed typical data and results are shown in diagrams of Figs. 3, 4, 5. The diagrams allow estimating properly the representative ambient temperature in the case of infrared measurements of temperature in open air space.