Hot wire anemometer with sine modulation of wire temperature

Author: J. Kielbasa

The paper demonstrates a method for simultaneous measurements of flow velocity v and the temperature of the medium Tg by means of a single-wire probe operating in a CTA configuration where the overheating ratio is modulated sinusoidally.

Assuming that parameters a and b in the King's equation (1) are not directly related to the temperature of the flowing medium, it becomes readily apparent that variations in power losses due to the change of the overheating ratio do not depend on the temperature of the medium Tg (Fig 2).

When power losses are expressed in terms of instantaneous overheating ratio N(t) and voltage across the hot wire Uw and the voltage developed in Fourier series, the relationships between the zero order component Uo and the first order component U1 of the voltage across the hot wire and the flow velocity v and medium temperature Tg can be found.

Thus obtained two nonlinear algebraic equations allow for simple computation of flow velocity v and medium temperature Tg.