Using Temperature Sensitive Paint (TSP) to map surface temperature

Abstract

UNSW Canberra has previously conducted considerable research into temperature surface-mapping techniques. The experimental mapping of surface temperature is a useful tool to verify the theoretical thermal behaviour calculated by generated simulations. The purpose of this research project was to trial the use of temperature sensitive paint (TSP) to achieve this task. The aims of this research were to assist in integrating this new capability into UNSW Canberra. This was achieved by calibrating the paint, then testing it on a nozzle test case to determine its accuracy, practicability, and suitability. This then aided in providing recommendations on future uses of the TSP. Another aim for this project was to develop an experimental method for using TSPs. TSPs are advantageous over other methods of temperature mapping as they provide a relatively non-intrusive, real-time approach with a relatively simple experimental setup. TSPs are made by embedding temperature sensitive luminescent molecules in an oxygen impermeable polymer binder. These molecules are excited by light of a certain wavelength, and when deactivating they may emit luminescent light. An effect known as thermal quenching leads to the decreasing in luminescent intensity with an increasing temperature. This is measured by capturing the intensity of the light using a DSLR camera and post-processing is used to give a measure of the intensity ratio. The relationship between the intensity ratio and temperature was plotted to find the calibration function of the paint. For this experimental research, TSP was applied to the surface of a test nozzle and its luminescent intensity was monitored throughout the use of the nozzle. The calibration function was then applied to the data to map the temperature distribution along the nozzle surface over time. The results were verified by an IR camera. It was found that with the method used the TSP data had a large variance, which contributed to an uncertainty of ±5°C. While the results from the TSP followed the same trend as the data from the IR camera it was found that the TSP was not very suitable to the test case chosen and would be more suited to applications that had higher operating temperature with a larger range. It was concluded that the TSP is more useful in providing a map of the distribution of the surface temperature, and not accurate in providing point temperatures.