Thin film heat transfer gauges for short duration transient measurements
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Surface temperature or heat flux measurement has always been one of the major requirements in many scientific and engineering applications and will continue to claim its position in the coming decades too. Certain applications demand transient measurements even in the order of milliseconds and accordingly the techniques used there must have response time fast enough to trace similar variations. In this regard, thin film sensors are the most suitable candidates because of their extremely small thickness which allows them to measure temperature quickly yet accurately. Several practical purposes starting from measurement of surface temperature, heat flux in internal combustion (IC) engines, gas turbine blades to high speed flight experiments utilizes thin film sensors, better known as thin film gauges (TFG). These TFGs are inherently resistance temperature detectors (RTD) consisting of a thin metallic film (silver/copper/platinum) topped over the surface of substrates of low thermal conductivity (pyrex/macor). They are advantageous in terms of response time, application range and small dimensions. However, these gauges are passive in nature and need to be powered by a constant current source. Furthermore, the measured time-dependent surface temperature of the gauge with the known thermal properties of substrate material, allows estimation of heat flux applied (both steady and transient) on the surface from any source. The purpose of this thesis is to provide a mature approach to the fundamentals of TFGs, right from their modeling, fabrication, characterization to application. Sufficient effort has been laid in this thesis to achieve some amount of expertise in fabricating efficient TFGs.
Supervisors: Niranjan Sahoo and Aynur Unal