GREENSPAN ACOUSTIC VISCOMETER FOR GASES

Double Helmholtz acoustic resonators, first proposed by Greenspan for measuring the viscosity of gases, were tested with helium, argon, and propane. Two different resonators were tested extensively with all thr ee gases. For each of these instruments, the results for the viscositi es of the three gases were consistent within +/-0.5% at pressures span ning the range 25-1000 kPa. Without calibration, the viscosities deduc ed from one viscometer were systematically 1% larger than data from th e literature; the viscosities from the second viscometer were systemat ically 3% larger than data from the literature. Ii the systematic diff erences were removed for each viscometer by calibration with a single gas at a single temperature and pressure, then nearly all the results for both instruments would have fallen within +/-0.5% of the data from the literature. In these viscometers, the test gases are in contact w ith robust metal parts only; thus, these instruments are applicable to a very wide variety of gases over a very wide range of temperatures.