Phase-Change Heat Transfer Measurements Using Temperature-Sensitive Paints

Abstract

Techniques based on temperature-sensitive paints (TSP) to measure time-resolved temperature and heat transfer distributions at the interface between a wall and fluid during pool and flow boiling are described. The paints are excited using ultraviolet (UV) light emitting diodes (LEDs), and changes in fluorescence intensity are used to infer local temperature differences across a thin insulator from which heat flux distribution is obtained. Advantages over infrared (IR) thermometry include the ability to use substrates that are opaque to IR (e.g., glass, plexiglass and plastic films), use of low-cost optical cameras, no self-emission from substrates to complicate data interpretation, high speed, and high spatial resolution. TSP-based methods to measure wall heat transfer distributions are validated and then demonstrated for pool and flow boiling.

Heat transfer coefficient: a review of measurement techniques

“…This type of temperature sensor is widely used as a mechanical switch for temperature control, usually, know as thermostats. [10] Few millimeters/minutes 0.1 °C Biomaterial [11,12] Few millimeters/seconds 0.1 °C Gas thermometers [13] Centimeters/minutes 0.001 K Acoustic [14][15][16][17][18] Centimeters/milliseconds 0.1 °C Electrical Thermocouple [19,20] 0.02-5 mm/50 ms-1 min 0.1 °C RTD [20,21] Few millimeters/minutes 0.001 °C Thermistor [13,21] 1-10 mm/20-300 s 0.01 °C (low span, 50 °C) Semiconductor junction [22] Few millimeters/minutes 0.5 °C Optical Optical fiber [23,24] millimeters 1D/millisecond 0.05-0.1 °C Thermoreflectance [25][26][27] 10 μm/down to ms 0.1-1.1 °C Liquid crystal [28][29][30][31] 2D/less than 1 s 0.5-0.9 °C Thermo-and photoluminescence [32][33][34][35] 2D observed temperature fields 1-31 °C Interferometry [36][37][38] 2D/milliseconds or less 2% (temperature in K) IR thermography [39][40][41] 40 μm-1 mm (2D)/down to ms 18 mK Temperature-sensitive paints (TSP) [41] 5 μm-1 mm (2D)/down to ms 0.4 °C 2.1.1.3 Gas thermometers Such mechanical thermometers are based on the variation in the pressure or volume when a fluid changes the temperature [13]. Basically, two types of fluid states are used, gas state or saturated state.…”

“…Hashimi et al [41] studied the dynamics of convective boiling in microchannels using two distinct techniques for two-dimensional unsteady surface temperature measurements, namely (1) infrared thermography and (2) thermal sensitivity paints. They measured the heat transfer during the passage of a Taylor bubble.…”

“…Optical techniques for temperature measurement are a set of emerging techniques that potentialize new applications hardly solved by mechanical or electrical temperature sensors. Their main advantages are noncontact temperature measurements, easy integration for obtaining high-resolution 2D temperature fields, fast response time and high immunity to electromagnetic interference [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41].…”

“…The working principle of this technique is the presence of infrared radiation detectors that can sense the infrared radiation from the body whose temperature is measured [39][40][41]. Sensors can be quantumtype or thermal type [13].…”

“…Hashini et al [41] evaluated the temperature-sensitive paints (TSP) technique applied to temperature measurements in pool and flow boiling experiments. The method uses a blue UV light to stimulate paint molecules for the emission of radiation at a longer wavelength.…”