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REFINED PROCEDURES IMPROVE REFRIGERATION PROPERTIES RESEARCH.

Damage to the Earth's ozone layer caused by use of chiorofluorocarbons has prompted an international effort to measure and correlate the thermophysical properties of alternative refrigerant fluids such as hydrochloro-fluorocarbons and hydrofluorocarbons. Scientists around the world who compared their measurement results discovered wide discrepancies. For one property, viscosity, data differed by as much as 15 % to 30 % between laboratories.

The situation led the International Union of Pure and Applied Chemistry to conduct a tightly managed round-robin measurement study organized by NIST to attempt to reduce the uncertainties. For this study, samples from a carefully prepared, high-purity source of a refrigerant known as 1,1,1 ,2-tetrafluoroethane, or R134a, were distributed to the nine participating labs in meticulously cleaned containers. Each lab made measurements following procedures that maintained the sample's purity and allowed sample recovery for subsequent analysis.

When these procedures were followed, measurement discrepancies were reduced dramatically. For example, the largest discrepancy for viscosity was 6% using a variety of measurement techniques.

NIST not only contributed measurements as a round robin member but also analyzed the data deviations among all of the laboratories for IUPAC.

The study proved that sample purity must be maintained throughout the measurement process, and even the sample container and measurement apparatus must be regarded as a source of contamination. NIST is now working with IUPAC on the development of improved standard reference correlations based on the study data to enable the design of more efficient and compact refrigeration equipment.
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Publication:Journal of Research of the National Institute of Standards and Technology
Article Type:Brief Article
Geographic Code:1USA
Date:Nov 1, 2000
Words:244
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