The Viscosity of Steam and Water at Moderate Pressures and Temperatures

The paper reports the results of an investigation of the viscosity of steam and compressed water. The measurements were carried out by means of an oscillating-body-type viscometer in order to develop an alternative method of measurement to the usually employed capillary viscometer, and also to provide an independent check on published data. The results for compressed water, obtained with the aid of an oscillating sphere, represent absolute measurements, and cover a range from 3 to 340 atm and from 20 to 186 C. The viscosity of water is shown to have a negative pressure coefficient below 35 C and a positive coefficient above that temperature. The maximum change in viscosity, at any given temperature over the pressure range covered is 5 per cent. The results show good agreement with previously published data and the deviations of experimental points from smoothed curves do not exceed 0.05 per cent. Although the present instrument is severely limited in range, the feasibility of measurements at elevated temperatures and pressures by means of the oscillation-type viscometer is clearly demonstrated. Particularly striking is the reproducibility and self-consistency of the results obtained.