The energy efficiency of water chillers used to cool large commercial buildings soon may get a big boost if a method developed by the U.S. Department of Commerce, National Institute of Standards and Technology (NIST) pans out in research using full-scale chiller systems, the NIST reports.
The method could save as much as 1% of the 300 billion kWh used each year by chillers, equivalent to 920,000 barrels of oil daily, according to Mark Kedzierski, NIST mechanical engineer, and developer of the technique.
The method stems from earlier NIST research designed to optimize the mixtures of chiller refrigerants with lubricants. The research showed that small amounts of some lubricants can enhance evaporator heat transfer and increase chiller efficiency. Additional research into the process showed that the most efficient heat transfer took place when the surface tension, viscosity, composition and chemical characteristics of the added oil complemented those of the chiller’s base lubricant.
In a recent paper, Kedzierski describes the NIST energy-saving method and details rules that have been developed to select the best oil additive based on the type of chiller lubricant.