In the last teen years, causes the big energetic and technologic development, there have been considerable efforts put into the use and development of thermographic technologies in many scientific sector. Thermography is a non destructive analysis to study in a simply way the objects' superficial thermal variations. In the field of civil engineering and in the conservation and monitoring of monuments the knowledge of walls thermal behaviour, the knowledge of wall texture and presence of possible plaster defects under a wall painting is very important. The building thermographic survey is quite complicate, because there are many factors that influence the values of measured temperatures. According to this fact, usually the building thermography survey is merely considered qualitative. For a more accurate measurement, the correct emissivity value of the investigated building materials is necessary to consider. Furthermore, for thermal images with many different equipment is necessary to consider different emissivity, one for each material. Consequently investigations of emissivity dependence on different building materials, on color, and on roughness of the same materials are investigated. Many sample walls are built using different materials, colours and roughness. The samples are heated using electrical radiant heater. The measurements are done in nearly steady state and variable conditions using the thermocamera and thermocouples. Markers with note and certified emissivity were used. Moreover two reference emitters with measured emissivity are used: a piece of PVC electrical tape and a piece of paper tape. The experiments ' results show the difficulty to obtain exact values of emissivity for each material. The emissivities don't depend on object's colours only when their material chemical composition is very similar. The emissivity changes when different colours of the same material are charged to massif presence of particular chemical elements. Also the roughness of the surfaces influences emissivity. Many materials and paints are investigated in laboratory and in real building's walls. Finally a quick method for in situ emissivity determination was analized.
Construction Materials in Civil Engineering: Study of Emissivity using Thermography
DESIDERI, UMBERTO;
2009-01-01
Abstract
In the last teen years, causes the big energetic and technologic development, there have been considerable efforts put into the use and development of thermographic technologies in many scientific sector. Thermography is a non destructive analysis to study in a simply way the objects' superficial thermal variations. In the field of civil engineering and in the conservation and monitoring of monuments the knowledge of walls thermal behaviour, the knowledge of wall texture and presence of possible plaster defects under a wall painting is very important. The building thermographic survey is quite complicate, because there are many factors that influence the values of measured temperatures. According to this fact, usually the building thermography survey is merely considered qualitative. For a more accurate measurement, the correct emissivity value of the investigated building materials is necessary to consider. Furthermore, for thermal images with many different equipment is necessary to consider different emissivity, one for each material. Consequently investigations of emissivity dependence on different building materials, on color, and on roughness of the same materials are investigated. Many sample walls are built using different materials, colours and roughness. The samples are heated using electrical radiant heater. The measurements are done in nearly steady state and variable conditions using the thermocamera and thermocouples. Markers with note and certified emissivity were used. Moreover two reference emitters with measured emissivity are used: a piece of PVC electrical tape and a piece of paper tape. The experiments ' results show the difficulty to obtain exact values of emissivity for each material. The emissivities don't depend on object's colours only when their material chemical composition is very similar. The emissivity changes when different colours of the same material are charged to massif presence of particular chemical elements. Also the roughness of the surfaces influences emissivity. Many materials and paints are investigated in laboratory and in real building's walls. Finally a quick method for in situ emissivity determination was analized.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
