ASHRAE Journal - February 2009 - (Page 18) In North American Supermarkets By David Hinde, Member ASHRAE; Shitong Zha, Ph.D., Member ASHRAE; and Lin Lan, Associate Member ASHRAE Carbon Dioxide ommercial refrigeration system design in North America has not been subjected to the pressures of HFC bans or high taxation of refrigerants C as in other parts of the world and is still driven primarily by energy consumption and system cost. The recent move towards systems with lower refrigerant charge and lower leakage rates has been, for the most part, voluntary, driven by corporate initiatives that have been focused on the increasing awareness of the effects of greenhouse gas emissions on the environment and climate change. Government regulations have been slow to respond to these concerns and maximum leakage rates are still not mandated for systems operating with HFC refrigerants. However, this is expected to change soon. When the reduction of refrigerant charge is desired, two systems are generally considered: distributed direct expansion systems, and secondary coolant systems. Distributed direct expansion 18 ASHRAE Journal a concern due to the increased number of components, connections, and still large amount of refrigerant-containing piping. Secondary coolant systems offer another alternative that can provide more significant reductions in charge and leakage rate. Introduced in the U.S. in 1996, medium-temperature secondary coolant systems using propylene glycol are gaining wider acceptance and represent a significant portion of business with more than 500 systems installed, primarily in the U.S., with a small percentage of installations in Canada and Mexico. Today, these systems are primarily applied not only for the benefits of HFC charge reduction, but enhanced product quality About the Authors David Hinde is manager, research and development, Shitong Zha, Ph.D., is a research engineer, and Lin Lan is a research engineer at Hill PHOENIX, Refrigeration Systems Division, Covington, Ga. systems have been applied successfully and are available from a variety of manufacturers in various forms. Some moderate decreases in refrigerant charge can be achieved. However, leakage rates remain ashrae.org February 2009 Copyright 2008 Hill PHOENIX, Inc. http://www.ashrae.org
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