Toward calibration-free wall shear stress measurement using a dual hot-film sensor and Kelvin bridges

Abstract

Combined heat transfer and wall shear stress measurements on the inner wall of a fully developed turbulent air flow in a round pipe were presented in this paper. The heat transfer was measured using a flush-mounted dual hot-film sensor composed of a non-electric conductive membrane sandwiched in between two thin nickel films. Each of the two films was installed in a branch of a separate Kelvin bridge, and operated at a same temperature; the bottom film served as an active heat insulator so that the Joule heat from the upper film transferred only to the air. Both theoretical analysis and measurements indicated for , where was the averaged Nusselt number and was the Péclet number. A calibration-free technique for wall shear stress measurement based only on measuring the Joule heat flux was found to be feasible, providing the Péclet number was in the range of 300–2500 and the film temperature was sufficiently large.

Highly Sensitive Flow Sensor Based on Flexible Dual-Layer Heating Structures

“…However, they did not fabricate the dual-layer hot film sensor or verify the simulation results practically. Gao Nan et al bonded two overlapped nickel films on the double surfaces of a polyimide (PI) film to obtain a sandwiched hot film sensor and carried out calibrations in a small wind tunnel [ 25 , 26 ]. However, the heat-insulating layer of their sandwiched structure sensor was thick, leading to a large size of the sensor (22 mm in width and 1.75 mm in length) and a compromised heat-insulating effect of the guarding heater.…”

Thermal Conductivity Gas Sensor with Enhanced Flow-Rate Independence

“…Currently, as one of the important detection principles of MEMS sensors, thermal detection has been widely used in fluid sensing fields, especially in gas-related detection, such as gas flow [ 1 , 2 , 3 ], thermal conductivity [ 4 , 5 , 6 ], shear-stress [ 7 , 8 , 9 ], and vacuum [ 10 , 11 , 12 ], etc. Compared to normal chemical sensors, thermal MEMS sensors have the advantages of broad-spectrum, fast response, low power consumption, and long-term stability, becoming a major, long-standing research focus [ 13 , 14 , 15 ].…”

An Indirect Method for Determining the Local Heat Transfer Coefficient of Gas Flows in Pipelines

“…This can be useful in the study of hypersonic flows. Determining heat flow in spacecraft [22], the cylinders of reciprocating internal combustion engines [23,24] and complex channels [25] have also been studied separately. Several studies are related to the study of heat transfer in microchannels through numerical modeling and experimental techniques [26][27][28][29][30].…”