Temperature maps measurements on 3D surfaces with infrared thermography

Abstract

The use of the infrared camera as a temperature transducer in wind tunnel applications is convenient and widespread. Nevertheless, the infrared data are available in the form of 2D images while the observed surfaces are often not planar and the reconstruction of temperature maps over them is a critical task. In this work, after recalling the principles of IR thermography, a methodology to rebuild temperature maps on the surfaces of 3D object is proposed. In particular, an optical calibration is applied to the IR camera by means of a novel target plate with control points. The proposed procedure takes also into account the directional emissivity by estimating the viewing angle. All the needed steps are described and analyzed. The advan- tages given by the proposed method are shown with an experiment in a hypersonic wind tunnel

3D temperature map reconstruction of a ceramic shell mold in investment casting process

“…The black dots are necessary because their emissivity is much higher (ϵ≈0.9) than the aluminum one (ϵ≈0.3) allowing to visualize the control points in the IR images as required by the calibration procedure [11]. These black dots have a spacing of 35mm and a diameter equal to 10mm resulting in a resolution of 4/5 pixels on the IR sensor, optimal for the calibration as suggested by Cardone et al [11]. a) b) Fig.…”

“…Nevertheless, the infrared data are in the form of 2D images while the ceramic shell mold is a highly three-dimensional body and a reconstruction of the temperature map is necessary. In literature a methodology to rebuild temperature maps on the surface of 3D objects is presented by Cardone et al [11]. Their procedure is based on an optical calibration of the IR camera by means of a target plate with control points and takes also into account the directional emissivity by estimating the viewing angle.…”

“…The aim of this paper is to reconstruct the 3D temperature map of the ceramic shell mold before the beginning of the casting by using the 3D reconstruction procedure discussed by Cardone et al [11]. The 3D temperature map is then discussed and analysed in order to find the regions of the mold that more preserve the temperature of the preheating furnace.…”

IR thermography in heat transfer measurements on a wing leading edge surface internally impinged by a row of air jets

“…The investigation is carried out with infrared thermography (IRT) applied to the heated thin foil technique [10]; this has required a specific setup and test procedure as will be described in the following sections 2.1 and 2.2. It is worth noting that the experimental apparatus is similar to that used by Meola et al [12], but with the substantial novelty that the temperature maps are rebuilt on the object mesh grid according to Cardone et al [11].…”

“…In this work the heat transfer performance of rows of circular jets internally impinging on the airfoil leading edge region is experimentally studied by means of infrared thermography with the heated thin foil heat transfer sensor [10]; the Nusselt number distribution is shown in 3D rebuilding [11]. Furthermore, a new data correlation between the average Nusselt number and the Reynolds number, by accounting for the impingement angle, is proposed.…”