Page 108 - libroRicercaIinnovazione_2016

Department of Engineering, ICT and Technologies for Energy and Transport Patent Title Thermal­hygrometric monitoring of wide surfaces by IR Thermography. Ref. CNR 1721 Assignee(s): CNR CNR Institute: ITC Main Inventor: Paolo Bison Countries: IT Priority date: 05/05/2006 Abstract The present invention refers to a method that allows to measure the air relative humidity, absolute humidity, and dew point by means of a thermographic equipment; this method is relevant – also thanks to a particular device described in this patent ­ for wide surfaces (i.e. a wall), particularly for artistic and historical patrimony. The moisture content of the wall is determined through the distribution and evolution of surface temperature by means of specific algorithms that identify the risk areas. The optical nature of the monitoring makes the scan fast and contactless. Background The main applications of IR thermography for the humidity detection are based on: a) absorption of infrared radiation (optical method); b) variation of the porous material thermal properties depending on the humidity content (dynamic thermal method); c) evaporative cooling (passive thermal method). Technology The method allows to quantitatively determine the main thermo­hygrometric parameters both of the air and of the solid surface. The device, called ‘Irpsicro’, is positioned close to the surface to be monitored and the temperature difference between ‘wet bulb’ and ‘dry bulb’ is measured by an IR camera. At the same time, the moisture content of the surface (i.e. a wall) is measured depending on the thermal effects due to evaporation. Advantages and Applications The evaporative process, due to the migration of salts inside the materials, is the main responsible of the degradation of the surfaces of the artistic and historical patrimony. The key points of the humidity analysis are the knowledge of the water content and of the exchange of vapour between surface and air. All the measurements are carried out with the same instrument reducing the inter­calibration errors. Development stage A prototype of the equipment, with a high level of automation, is available at ITC­CNR in Padova. It consists of a IR camera with microbolometer sensor that is mounted on a pan­tilt head and a grid of ‘Irpsicro’. The instrument was already utilized in several measurement campaigns: Chiesa di Baver (TV), La Torrazza del Castello di Masino (TO), Chiesa di San Vito L’Aquila (AQ), Abbazia di Novalesa (TO), Chiesa di San Gottardo 99 Asolo (TV). It is establishing a new CNR Spin­off.