Design,Manufacture And Performance Study Of Ceramic-based Thick Film Heat Flux Sensor

With the rapid development of science and technology and modern industry,the phenomenon of heat transfer exists in many production processes,especially in aerospace,energy construction,nuclear power engineering and other ultra-high temperature working conditions,the need to solve the heat transfer problem is more urgent.In recent years,heat flow density measurement technology has become the focus of research at home and abroad,and some progress has been made,but the country is still in a relatively backward situation.The main problem is that the more advanced heat flux sensors on the market are produced abroad,expensive,and over a certain working temperature need to connect the water-cooling system,inconvenient to use,not suitable for installation and testing in a narrow space.Therefore,this paper focuses on optimizing the structure size and improving the working temperature,using alumina ceramics as the substrate combined with screen printing process for the design and manufacture of high temperature thick film thermopile type heat flow sensor.The main research includes the following aspects:(1)Analyze the thermoelectric conversion mechanism of temperature sensor and heat flux sensor,including the working principle of thermocouple and the working principle of thermopile type heat flux sensor;complete the overall design scheme of heat flux sensor,including the selection of substrate material,thermoelectric material,thermal resistance layer material and preparation process as well as the construction of calibration platform.To lay the theoretical foundation for the preparation of heat flux sensor with working temperature not less than 1200℃ and heat flow density not less than 200 kW/m2.(2)The preparation of thick film electrode layer is completed by screen printing process and high temperature sintering technique,and the preparation of thermal resistance layer is carried out by air compressor and spray gun.Microscopic characterization analysis of Pt,Pt/Rh and SiO2 at different stages are carried out to provide microscopic support for the subsequent high temperature performance test.The results show that the electrode film layer and thermal resistance layer have a dense structure and no peeling phenomenon.(3)According to the overall design plan requirements,a temperature-heat flow density test calibration platform was built,mainly consisting of a muffle furnace,a standard S-type thermocouple,a signal collector,a prepared heat flow sensor,a standard heat flow meter and a computer.The test results show that the prepared heat flow sensor has good repeatability at 501200℃ and 2-283.3 kW/m2 test environment,the maximum output potential is 1.4126 mV with good linearity,and the sensitivity distribution of the sensor is in the range of 3.50-7.08×10-3 mV/(kW/m2).On this basis,a 1200℃ high-temperature durability test was conducted with a retention time of 4 h,and its output had the same variation trend as that of the standard heat flow meter.In order to better grasp the performance of the sensor,we also conducted a dynamic response time test,where a heat gun simulated the generation of transient heat flow as the excitation source,and the results showed that the response time of the thick film heat flux sensor was about 1.18 s.