A surface tension analyzer specially designed to handle volatile fluids such as refrigerant 134a (R-134a) has been designed and constructed. Surface tension is greatly affected by temperature and the contaminants in the liquid. A relatively simple and practical method was developed to measure the surface tension of a small sample of volatile liquid, and to determine whether it had become contaminated with dissolved oil, grease or a surface active agent. The maximum bubble pressure method was selected and the apparatus constructed was tested using distilled water and methanol. The experimental difficulties overcome in the design and the operation of the device are discussed and sample measurements for water, methanol, and R-134a are presented. The device works well with volatile fluids and the uncertainty of the measurements is less than ±2%.

Reprinted from the International Journal of Heating, Ventilating, Air-Conditioning and Refrigerating Research, Vol. 7, No. 1, January 2001, pp. 3-14.

Units: SI