The European Union fluorinated greenhouse gases (F-gas) regulation of 2014 limited the amount of ozone depleting substances which could be sold in the EU from 2015 onwards, aiming to gradually phase down their use in steps, to target a reduction to one-fifth of 2014 sales by 2030. This triggered a change in refrigeration technologies and refrigerant gases for use in cooling systems.
The response of the commercial and industrial refrigeration sector has been to transition from traditional fluorinated gases toward both natural and synthetic refrigerants, with low Global Warming Potential (GWP). For industrial applications, ammonia has remained viable as a refrigerant gas, and will continue to be used in the long term. The design and supply by OEM’s, of compressors for refrigeration by ammonia (R717), is evidence of its longevity in this application.
Nynas naphthenic oils are compatible with ammonia refrigerant, and are commonly used in piston refrigeration compressors. NYNAS NYFROST™ wax free oils have a low pour point, resulting in a good flow at low temperatures. The low viscosity index results in improved heat transfer efficiency, and the low aniline point ensures that contaminants remain within the solution. These combined characteristics serve to enhance the reliability of the compressors.
NYFROST™ refrigeration compressor oil has undergone full scale trial runs at ice making and cold storage facilities, over a 3-month period. The piston compressors had been in service for several years, and close monitoring of the oil was undertaken during the trial run.
The results indicate that the oil is beginning to thicken and absorb water; however, no acidification (which is an indication of chemical oxidation) of the oil has occurred. A typical operating temperature and pressure of the compressor were maintained throughout the 3-month trial run.
Furthermore, laboratory analysis of the miscibility gap between ammonia and NYNAS NYFROST™ oil indicates that at ambient temperature (20°C), approximately 1% of the R717 is miscible in the oil, and at 40°C, approximately 2% R717 is miscible in the oil.
Naphthenic oils will continue to have a beneficial role in the refrigeration industry, with both laboratory and full-scale testing indicating a good performance of the lubricant in piston compressors for refrigeration with ammonia.
Author: René Abrahams
René Abrahams is Technical Advisor Naphthenics for the lubricant industry, currently based in Singapore on assignment supporting Nynas sales activities in the APAC region. An analytical chemist with 15 years’ experience in the downstream oil industry, focusing on naphthenic applications since 2011.