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Title: The measurement of rotational relaxation times in gas mixtures at elevated temperatures
Author: Blacker, Stephen G.
ISNI:       0000 0001 3466 409X
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1977
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The design, construction and use of an apparatus for the measurement of ultrasonic absorption and velocity dispersion in gas mixtures at elevated temperatures is described. The apparatus was used to measure rotational relaxation times in mixtures of normal hydrogen and argon at 293, 473 and 673 °K. The apparatus was capable of operation at temperatures from room up to 1000 °K and at pressures from one atmosphere down to ~ 0.015 of an atmosphere. It operated at a sound frequency of ~1 MHz, giving a frequency to pressure ratio (f/p) of between 1 and 65 MHz per atmosphere. A variable path length technique was employed. Bursts gated from a 1 MHz reference sine wave were amplified and transmitted, via fused quartz buffer rods, through the heated gas. Detection was achieved by mixing the received signal with the reference signal in a Phase-Sensitive Detector, the output of which was sampled and averaged by a Boxcar Integrator. The output of the Boxcar Integrator was digitised and recorded on punched tape for computer analysis which, with a knowledge of the sound frequency, yielded values of absorption coefficient and velocity. These were plotted as functions of f/p with temperature as a parameter. Calibration runs are described. These were performed on pure argon to determine the precision of measurements and, by comparison with other work, the accuracy of results obtained. Finally the results for mixtures of normal hydrogen and argon are presented and discussed. Values of rotational relaxation time and collision number for these mixtures are obtained and compared with available theoretical predictions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available