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©2016 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 58, no. 10, October 2016

Jörgen Rogstam, Member ASHRAE

About the Author
Jörgen Rogstam is managing director of EKA (Energi & Kylanalys) in Stockholm.

The industry is most likely experiencing a shift in the way artificial ice rinks are refrigerated. After the first ice rink system using carbon dioxide (CO2) as secondary refrigerant was built in 1999, it wasn’t until 2010 that the first ice rink using a transcritical CO2 system was realized. This article discusses the rationale behind using CO2 in ice rinks and the most important steps of the evolution of the technology.

The history and evolution of ice rinks is well documented by Martin in “Evolution of Ice Rinks”1 where it is concluded that the first known ice rink was The Glaciarium in London in 1876. Technically it is described as “Copper pipes were laid down, and through these, a mixture of glycerine and water was circulated after having been chilled by ether.” Most modern ice rinks could be described similarly, although the fluids would be different.

 

Refrigerants

In the early days of refrigeration history, starting in the 19th century, only natural fluids were available. In the beginning of the 20th century, chemical science learned to create substances with more suitable properties such as R-12 and R-22. Today, R-22 is subject to phaseout according to the Montreal Protocol, but it is still in use in many ice rinks throughout North America. A review of the EPA’s list of acceptable substitutes will push many in the refrigeration industry toward natural refrigerants. Among the natural alternatives, only a few are suitable for ice rink refrigeration, and the following are normally considered: ammonia, hydrocarbons, and CO2.

In the industrial refrigeration sector (which includes ice rinks), ammonia has been widely used for decades. In recent times, we have seen a growing interest in using CO2 as refrigerant in many applications, especially in the commercial sector. This interest is present in the industrial sector as well, which will have considerable implications for the business.

 

Carbon Dioxide in the Refrigeration Industry

The history of CO2 can be divided into two parts. The first is well described by Bodinus, who explained how the systems evolved and developed during the 19th and 20th centuries. He concluded this era ended when the interest in CO2 virtually disappeared in the 1950s since synthetic refrigerants were introduced and took over (Figure 1).

At the end of the 1980s, Norwegian professor Gustav Lorentzen brought up the idea of using CO2 again, which introduced the second era of the history of CO2. He investigated how CO2 technology could be used in different applications and published many articles. In 1993 he stated that “CO2 is as close to the ideal refrigerant as it is possible to come….” One aspect of CO2 that he discussed was how heat may be reclaimed, as well as the associated control strategies to optimize the process.

 

Properties of Carbon Dioxide

Carbon dioxide is a natural, nonflammable and nontoxic substance that offers technical advantages when compared to other natural alternatives. Regarding toxicity, codes such as the International Mechanical Code (IMC) and the European corresponding EN378 do impose certain safety measures for using CO2 as a refrigerant.

The challenge with CO2 basically stems from the fact that it has a critical point at a temperature of about 31°C (88°F) with a corresponding absolute pressure of about 74 bar (1070 psi). At conditions above the critical point, the difference between liquid and vapor disappears and no condensation occurs. With proper design, CO2 systems offer good efficiency and low cost in many applications.

 

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