Speed of Sound
For the determination of speed of sound (sonic speed, acoustic velocity) for liquids an apparatus is available in our laboratory. For further speed of sound measurements in the liquid and gas phase also to derive ideal gas heat capacities we cooperate with an external laboratory.
- Ultrasonic cell for liquid speed of sound (ThermoVersum Project, up to 200 bar, 273 to 393 K
- Ultrasonic cell for liquid speed of sound (external laboratory, up to 1000 bar, 233 K to 393 K)
- Spherical resonator for vapor speed of sound and derived ideal gas heat capacities (external laboratory, 0.2 to 20 bar, 233 K to 393 K)
Ultrasonic Cell for Liquid Speed of Sound Measurements
The speed of sound data for liquids can be measured
with an automated setup. A speed of sound chamber with two piezoelectric
transducers as transmitter and receiver mounted at opposing walls is the core
of the apparatus. The method for the speed of sound determination operates in
the through-transmission mode and measures the propagation time of short
acoustic pulses which are repeatedly transmitted through the liquid sample. Using
a tunable voltage controlled oscillator this technique was invented by Heimel,
Leopold and Stabinger and is employed for the commercial speed of sound
measurement apparatus DSA 5000 from Anton Paar (Graz, Austria).
The pressure cell (see following figure) is a prototype from the Labor fuer
Messtechnik Stabinger (Graz,
Austria). It is
applicable for speed of sound measurements of liquids between about 700 and
2000 m/s at temperatures between 273 and 393 K and pressures up to 20 MPa. Using
a liquid circulation cryostat/thermostat or an electric heating the cell can be
thermostatted. The temperature is monitored with a Pt100 resistance probe mounted
directly in the pressure cell. For the high pressure measurements the pressure cell is
connected to an electronic controlled piston pump. The pressure is
monitored by a calibrated pressure transducer.
