Hot films - Effects of probe reversal and flow oscillation
Abstract
Under conditions of steady and pulsating flow in liquids, cylindrical film probes have been found to possess a directional calibration which can be explained by considering the distribution of the local Nusselt number over the heated film. Under low-frequency pulsating conditions, the probe signal at the flow reversal point can be less than, equal to, or greater than the true zero-velocity signal. It is suggested that this frequency-dependent discrepancy is the resultant of swirl around the wire and the conduction of heat to the fluid immediately adjacent to the wire before natural convection can establish a steady state. Within the range of pulsations studied (0-0.24 Hz), the dynamic and steady flow calibrations were coincident at velocities above approximately 3.0 cm/s.
- Publication:
-
Journal of Physics E Scientific Instruments
- Pub Date:
- November 1976
- DOI:
- 10.1088/0022-3735/9/11/005
- Bibcode:
- 1976JPhE....9..921H
- Keywords:
-
- Cylindrical Bodies;
- Heat Transfer;
- Hot-Film Anemometers;
- Liquid Flow;
- Oscillating Flow;
- Reversed Flow;
- Calibrating;
- Flow Stability;
- Flow Velocity;
- Free Convection;
- Laminar Flow;
- Nusselt Number;
- Signal Analysis;
- Steady Flow;
- Instrumentation and Photography