Thermal Flow Sensors for Harsh Environments

Flow sensing in hostile environment is of increasing interest for applications in automotive, aerospace, and chemical and resource industries. Compared to their counterparts, thermal flow sensors are attractive candidates due to the ease of fabrication, lack of moving parts and higher sensitivity. Recently, a number of thermal flow sensor prototypes have been reported in the literature demonstrating the measurement of fluid flows under hostile conditions. This paper summarizes the concept of thermal flow sensing, operational modes and transduction mechanisms. Then, the choice of materials and their corresponding properties are presented in details. The paper also reports recent progress in the development of thermal flow sensors for harsh environment. In addition, the issues and considerations in packaging are reviewed. Finally, we conclude the review with the future prospects.

Download Full-text

MEMS flexible thermal flow sensor for measurement of boundary layer separation

Modern Physics Letters B ◽

10.1142/s0217984916501773 ◽

2016 ◽

Vol 30 (15) ◽

pp. 1650177 ◽

Cited By ~ 3

Author(s):

Jui-Ming Yu ◽

Tzong-Shyng Leu ◽

Jiun-Jih Miau ◽

Shih-Jiun Chen

Keyword(s):

Boundary Layer ◽

Boundary Layer Separation ◽

Flow Sensor ◽

Thermal Flow ◽

Sensing Element ◽

Suction Surface ◽

Flow Sensors ◽

Micro Electro Mechanical Systems ◽

Thermal Flow Sensor ◽

Mems Technology

Micro-electro-mechanical systems (MEMS) thermal flow sensors featured with high spatial resolutions, fast frequency response and minimal interference with fluid flow have been applied widely in boundary-layer studies and aerodynamic flow sensing and control due to the inherent outstanding performances. In this study, MEMS thermal flow sensors were designed and fabricated on a flexible skin using the MEMS technology. The dimension of a single sensing element was 200 [Formula: see text]m × 260 [Formula: see text]m, which had a resistance of about 200 [Formula: see text] after annealing. By configuring thermal flow sensors in either a single thermal flow sensor and a thermal tuft sensor, separation points of a two-dimensional (2D) LS(1) 0417 airfoil at various angles of attack could be precisely detected. The experimental results show good agreement with the hot wire sensor and particle traced flow visualization in detecting the separation point on the suction surface of the airfoil.

Download Full-text

Investigations into packaging technology for membrane-based thermal flow sensors

Journal of Sensors and Sensor Systems ◽

10.5194/jsss-4-45-2015 ◽

2015 ◽

Vol 4 (1) ◽

pp. 45-52 ◽

Cited By ~ 3

Author(s):

G. Dumstorff ◽

E. Brauns ◽

W. Lang

Keyword(s):

Cross Section ◽

Experimental Results ◽

Flow Sensor ◽

Channel Cross Section ◽

Thermal Flow ◽

Specific Design ◽

Flow Sensors ◽

Packaging Technology ◽

Thermal Flow Sensor ◽

Fluid Properties

Abstract. A new packaging method to mount a membrane-based thermal flow sensor, flush with the surface, is presented. Therefore, a specific design for the housing is shown, which is also adaptable to other conditions. It has been experimentally shown that it is important to mount the sensor flush with the surface. In addition, the experimental results are discussed. If a membrane-based thermal flow sensor is not mounted flush with the surface, vortices can occur (depending on velocity and fluid properties) or the reduction in the channel cross section plus a decrease in sensitivity have to be taken into account.

Download Full-text

Design, Simulation, and Fabrication of a Copper–Chrome-Based Glass Heater Integrated into a PMMA Microfluidic System

Micromachines ◽

10.3390/mi12091067 ◽

2021 ◽

Vol 12 (9) ◽

pp. 1067

Author(s):

Santiago Tovar ◽

Cesar A. Hernández ◽

Johann F. Osma

Keyword(s):

Heat Transfer ◽

Heating Surface ◽

Fluid Flows ◽

Microfluidic System ◽

Heat Transfer Process ◽

Heater Surface ◽

Thermal Flow ◽

Flow Rates ◽

Thermal Flow Sensor ◽

Heating Behavior

In this paper, the development of a copper–chrome-based glass microheater and its integration into a Polymethylmethacrylate (PMMA) microfluidic system are presented. The process highlights the importance of an appropriate characterization, taking advantage of computer-simulated physical methods in the heat transfer process. The presented system architecture allows the integration for the development of a thermal flow sensor, in which the fluid flows through a 1 mm width × 1 mm length microchannel across a 5 mm width × 13 mm length heating surface. Using an electrothermal analysis, based on a simulation and design process, the surface heating behavior curve was analyzed to choose a heating reference point, primarily used to control the temperature point within the fluidic microsystem. The heater was characterized using the theory of electrical instrumentation, with a 7.22% error for the heating characterization and a 5.42% error for the power consumption, measured at 0.69 W at a temperature of 70 °C. Further tests, at a temperature of 115 °C, were used to observe the effects of the heat transfer through convection on the fluid and the heater surface for different flow rates, which can be used for the development of thermal flowmeters using the configuration presented in this work.

Download Full-text