Development of MiST-IR : multi-spectral infrared thermography

Abstract

In this thesis, I present a new diagnostic technique for interrogating boiling heat transfer phenomena. The technique, called Multi-Spectral Infrared Thermography or MiST, builds on previous diagnostic techniques for measuring the 2-D wall temperature distribution or the 2-D phase distribution of the fluid above the surface. These methods make use of infrared thermography, a well developed practice involving the use of a high-speed infrared camera to collect visual data. By analyzing the data with both qualitative and quantitative tools, insights into boiling heat transfer mechanisms can be gained. In addition to the MiST technique, a refined infrared camera calibration model is presented for accurately determining the wall temperature. MiST is a new technique that allows for the simultaneous measurement of both the temperature distribution and the phase distribution. This is in sharp contrast to previous techniques which have only allowed the measurement of one or the other. MiST uses a highly engineered, semi-transparent, thin-film heater to enable the simultaneous measurement of the two properties. The heater separates the two signals, one from the temperature and one from the phase, by taking advantage of two regions of the electromagnetic spectrum. By spectrally separating the two signals, no limitation in resolution or field of view is made. The refined camera calibration model presented builds on previous work, which quantified the radiation captured by the camera and used a coupled radiation and conduction model to back out the complete axial temperature distribution within the heater. The new model refines the older version by taking into account spectrally varying optical properties within the heater. The spectral data is easily acquired with a Fourier transform infrared spectrometer, and fed into the radiation model for enhanced accuracy. The development of MiST presents new opportunities in boiling heat transfer for insight into a complex phenomena. The use of MiST in boiling and condensation experiments will lead to the development of new heat transfer models, and can provide high-resolution data for computational fluid dynamics models. MiST presents the logical progression forward in boiling diagnostic tools as it provides enhanced data acquisition opportunities when compared to it's legacy versions.