Frequency response and instantaneous temperature profile of cold-wire sensors for fluid temperature fluctuation measurements

The information of the wire response is necessary for the estimation of corrections and uncertainty of temperature measurements. This paper describes the theoretical response of cold-wire sensors to temperature fluctuations in a fluid flow. Existing transfer functions of cold wires are approximate and implicit functions of frequency. We present the exact solutions of heat conduction equations for a cold wire and stubs taking account of the prong effect. Because the solutions have simple forms of elementary functions, we can easily calculate the frequency response of cold wires. Sample calculations are given under several typical conditions. Also, the instantaneous temperature profiles of a cold wire are obtained for the first time.