Abstract
Thermal control by IR devices is a fairly difficult task, because it depends on a large number of external factors. The greatest error of contactless temperature measurement method is unknown or variable emissivity of the surface of the object. This is due to the fact that the ability of the object to emit infrared radiation can vary because it is depended on the material, properties of the surface, observation direction, and in the case of some materials – on temperature. Technological audit was conducted to identify the variation characteristics of emissivity coefficient in terms of thermal control. The aim of audit was to determine the effect of observation angle on the emissivity coefficient. Using thermal imager and auxiliary equipment it was found that with the measurement error is increased with increase of observation angle and may reach 50 %. The authors conducted a series of experiments confirming the effect of observation angle on accuracy of temperature measurement, and proposed dependencies allowing to reduce the value of absolute error of measurement using IR devices to several degrees that in relative form less than 1 %. Research results will improve the accuracy of temperature measurement by taking into account an effect of observation angle on emissivity coefficient of the object, normalize image thermograms for different sections of the object, as well as the select possible defective areas on the thermogram to determine the uniformity of thermal field.
Highlights
As we know, the basic industries of Ukraine are widely use energy-intensive high-temperature processes: melting and surface treatment of metal parts and others
There are processes that occur at much lower temperatures (250...500 °C), but they belong to the high-temperature, because the tempera ture is a major factor in the intensification of the processes for obtaining maximum yield of the finished product with high technical and economic indicators
– actual temperature measured by contact thermo meter; – temperature measured by thermal imager at different observation angles; – temperature measurement taking into account ob servation angle
Summary
The basic industries of Ukraine (metal lurgy, chemical industry, construction materials industry and mechanical engineering) are widely use energy-intensive high-temperature processes: melting and surface treatment of metal parts and others These processes require careful adherence to recommended temperature, because tempera ture control – the most important and universal means of increasing the process rate and increase the yield of the finished product. Non-contacting and speed of temperature control by devices that are detected a radiation in the infrared and light range, high resolution, providing detection of local and temporary differences of temperatures on objects of control, visualization of thermal fields are the main ad vantages of these devices for thermal control [2] The use of such devices requires paying attention to instru mental and methodical errors that affect the accuracy of temperature measurement.
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