Development of absolute hot-wire anemometry by the 3ω method

Abstract

We have developed hot-wire anemometry applying the 3omega method. The approach is based on the same heat transfer process as traditional anemometry, but substituting the constant current by a sinusoidal current and using synchronous detection to measure the conductive-convective exchange coefficient and the gas flow rate. Our theoretical model is tested with air flow at 300 K under atmospheric pressure: The experimental results are in agreement with the numerical simulation, justifying the technical choices in the 3omega method and the approximations made. The effectiveness of the 3omega method for measuring the flow rate and the conductive-convective exchange coefficient between the hot wire and flowing gas is discussed.

The 3-Omega Method for the Measurement of Fouling Thickness, the Liquid Flow Rate, and Surface Contact

“…Ref. [10] uses a wire as an alternative to a thin film; however, this leads to a complicated data analysis that involves the frequency dependence of the 3 ω signal. The method in ref.…”

“…In modified configurations, it has also been applied to the measurement of the thermal conductivity of gases [6,7] and fluids [8,9], also including fluids in flow [9]. For the past decade, the 3 ω method has been investigated with respect to the measurement of flow speeds [10,11], liquid levels [12], and has been used as a sensor for the measurement of cell viability [13]. …”

High‐resolution wind speed measurements using actively heated fiber optics

“…We employ an energy balance approach to quantify the convective energy transport from the heated cable by the moving air, which is a unique function of wind speed and temperature difference between the cable surface and the air. The governing energy balance equations are based upon fundamental heat flow principles for a horizontally oriented heated FO cable and can be expressed as the rate change of internal energy E (J) stored in a FO cable segment [ Polyanin , ; Heyd et al ., ]: where c p , (J kg −1 K −1 ) is FO cable specific heat capacity, ρ (kg m −3 ) is FO cable density, V (m 3 ) is FO cable segment volume, T (K) is FO cable segment temperature, t (s) is time, K s (J s −1 m −1 K −1 ) is FO cable thermal conductivity, R (m) is radial direction, z (m) is axial direction, and Q (J s −1 ) is the sum of incoming and outgoing energy fluxes. Equation assumes that energy changes as a result of mechanical work done on the system can be neglected.…”

Improved 3-omega measurement of thermal conductivity in liquid, gases, and powders using a metal-coated optical fiber

“…3,7,9,26 Metal-coated 3ω improves THW and solid-wire 3ω's heater by using a micron-scale metal-coated optical fiber rather than a thin solid metal wire. The thinner metal-cross-section results in signal improvements due to increased axial electrical and thermal resistance.…”