Engineering America's (5th) Favorite Sport
It’s the most wonderful time of year again! It’s playoff hockey season! I still vividly remember my first ever hockey game in 1999 at the then-Gaylord Entertainment Center, referred to as the GEC by locals (and pronounced as a single syllable word, “geck”). Besides being utterly transfixed by this new sport, I was amazed by how a giant ice rink had magically replaced what I could have sworn was a concert stage back when it was barely jacket season outside. Even today as a Boston-area resident and frequent supporter of the Boston Bruins (though never over my hometown Preds), I’m still amazed walking into TD Garden and seeing the freshly prepped indoor ice rink ready to go where a basketball court stood just 24 hours before (and that it’s still somehow warmer in an ice arena than it is outside). So how do they do it all?
First things first: the design of a rink in general! An ice rink is essentially a refrigerator on a massive scale. This massive refrigerator is built atop insulation layers (3) of sand, gravel, and polystyrene foam covering a heated concrete foundation (4). This concrete foundation ensures the rink’s insulation sublayers are not compromised or damaged by the freezing structure above it. Over the insulation layers, a matrix miles long of piping is encased by another concrete slab (2), the “chilled concrete slab.” The ice rink’s skating surface (1) is formed on top of this chilled concrete slab, layer by layer.
Now comes the differentiator between our massive refrigerator-ice rink and your everyday refrigerator: an ice rink is cooled through an indirect refrigeration cycle. Through our matrix of subfloor piping, a secondary freezing solution is pumped. The type of solution varies by rink, but common mediums are brine water and glycol. After pumping through the chilled concrete slab - removing heat as it flows - the secondary solution flows through a chiller. The most common chiller design is the “shell-and-tube” variety where your solution is pumped through several small pipes within a larger single pipe filled with refrigerant. Inside the chiller, a refrigerant absorbs heat from the “warm” solution, which eventually causes the refrigerant to boil. Once the secondary solution pumps through the chiller, it is sent back out to the rink’s chilled concrete slab to continue the cycle, whereas the now-vaporized refrigerant moves to the system’s compressor. In the compressor, our refrigerant is pressurized, superheating the gas. At this point, it moves to the condenser where the pressurized gas is cooled through a heat exchanger with either air, water, or a combination of the two. This causes the refrigerant to condense back into its liquid form, ready to return to the chiller for more heat absorption.
Once the ice rink system is installed, it’s time to make some ice! Workers will create the ice layer by layer, painting the rink at around ½ inch of thickness. Once the rink is painted, up to another dozen or so layers are added to bring the total thickness to between ¾ inch and 1- ½ inches.
Our indirect refrigeration process will run continuously 24/7 while the ice rink is installed, with minute adjustments in conjunction with the building’s HVAC system to accommodate for outside humidity and temperature and the ice sport anticipated. (Did you know there are different ice temperatures preferred for ice hockey vs ice skating?) If the surrounding air is allowed to get too warm or the humidity too high, fog will develop on the ice – which, though cool to see, greatly hampers any sport being played. Click here1 for a glimpse at the fog-filled 1988 Stanley Cup Final Game 4 between the Boston Bruins and the Edmonton Oilers.
Once all that is set, transforming a multipurpose arena from an ice rink to hard floor or vice versa is technically quite simple, though it can be very time-consuming. The not-so-secret secret is that once a rink is filled at the beginning of a season, it’s rarely ever drained before the end of the season. The floor of the basketball court, concert venue, or speaker event is simply laid over a layer of composite mats on top of the ice rink. Seating is then adjusted per the event and voila! It’s showtime! Here’s a great video of the complete transformation from the Bruins configuration to the Celtics configuration of TD Garden2.
Many thanks to the fine folks of HowStuffWorks.com3, RefrigerationSchool.com4, and AthleticBusiness.com5 for providing such great overviews on ice rink design. If you’re interested in reading about the next generation system for ice rinks, Machine Design6 has a great intro article on the benefits of CO2-based systems over the traditional ammonia-based systems linked below.
-Casandra Ceri, Jr. Mechanical Engineer
1 oilerfanatic1. “Oilers-Bruins in the Fog - 1988 Stanley Cup.” YouTube, 4 June 2016, www.youtube.com/watch?v=aC06By4HNAA&t=42s. 01 May 2018
2 Rock, Michael. “TD Boston Garden Changes From Ice To Parquet Floor [VIDEO].” FUN 107, 11 Nov. 2013, http://fun107.com/td-boston-garden-changes-from-ice-to-parquet-floo/
3 Russell-Ausley, Melissa. “How Ice Rinks Work.” HowStuffWorks, HowStuffWorks, 1 Apr. 2000, https://entertainment.howstuffworks.com/ice-rink.htm
4 Nguyen, Oanh. “Ice Hockey Rink Refrigeration.” Refrigeration School, Inc. (RSI), 30 May 2017, www.refrigerationschool.com/blog/hvacr/ice-hockey-rink-refrigeration/
5 Steinbach, Paul. “Understanding Recreational Ice Refrigeration.” Athletic Business, Oct. 2000, https://www.athleticbusiness.com/Stadium-Arena/understanding-recreational-ice-refrigeration.html
6 Scully, Leah. “Why Ice Rinks Choose Carbon Dioxide for Climate Control.” Machine Design, 18 Aug. 2017, http://www.machinedesign.com/mechanical/why-ice-rinks-choose-carbon-dioxide-climate-control