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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

AN INTEGRATED THERMAL SENSOR BASED ON MEMS FOR TEMPERATURE AND HEAT FLUX MEASUREMENTS OF JET IMPINGEMENT COOLING OF CO2 AT SUPERCRITICAL PRESSURES

Kai Chen
Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Key Laboratory for CO2 Utilization and Reduction Technology of Beijing, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

Rui-Na Xu
Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Key Laboratory for CO2 Utilization and Reduction Technology of Beijing, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

Pei-Xue Jiang
Beijing Key Laboratory for CO2 Utilization and Reduction Technology Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

Abstract

Jet impingement heat transfer at supercritical pressures is crucial in hydrothermal spallation drilling with supercritical water jets and thermal protection of scramjet. Thermal measurements at high pressure environment becomes more difficult due to severe sealing and strength requirements. This paper developed an integrated thermal sensor based on Micro-Electron Mechanical System (MEMS) processing technologies for temperature and heat flux measurements of jet impingement cooling of CO2 at supercritical pressures. The integrated thermal sensor was manufactured with BF-33 borosilicate glass of 0.5 mm because of its low thermal conductivity coefficient and good performance for thermal shock. A layer of serpentine platinum heating film of 350 nm was sputtered at the bottom of BF-33 to provide uniform heat flux and the radial conduction in the BF-33 plate was restricted by the small thickness and low thermal conductivity of BF-33. Annulus platinum thermal resistors of 50 nm were sputtered on the upper surface of the BF-33 plate at different radial locations to get the temperature distribution of the jet impingement surface. A layer aluminum film was evaporated on the leads of the annulus platinum thermal resistors to reduce the influence of lead resistance on temperature measurements. The results of local jet impingement cooling at subcritical pressures showed good agreement with experimental results of existing literature. Variations of heat transfer coefficients with jet inlet temperature were observed at supercritical pressures and the maximum heat transfer coefficient occurred when the inlet temperature was higher than the pseudocritical temperature and the surface temperature lower than that.

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