Viscosity of new refrigerants

Abstract

Measurements of the viscosity of several environmentally-acceptable refrigerants that have been made in recent years are reviewed. In particular, a detailed survey of the results for R134a in the liquid phase is presented because, for this fluid, the greatest number of independent experimental results is available. It is shown that there are significant discrepancies between the results of various authors and that they lie outside the bounds of the mutual uncertainty claimed. The nature of the discrepancies between any two sets of results is shown to be systematic whether they have been performed in similar or different types of instrument. For R32 and R125 in the liquid phase, where there are very many fewer experimental results available, the situation is essentially the same. It is argued that these discrepancies arise from a lack of proper precautions in the performance of the measurements either because of difficulties associated with the purity of the samples employed or because, in some instruments, there has been insufficient attention devoted to discrepancies among the results of research workers with established records of high-quality measurements are damaging to the external perception of the science of viscometry and that remedial action to remove the difficulties is essential and urgent. Specific recommendations for such action are made.