Skating rinks maintain their frozen surfaces even in warm air because the temperature beneath the ice is so cold that the ice is not affected significantly by moderate temperatures above it.
Thus a burst of sunshine over an outdoor rink, which allows skaters to shed their sweaters, cannot succeed in melting the ice.
In a figure skating rink the ice is generally about 2 inches thick; permanent ice hockey rinks use slightly thicker ice. It lies on a concrete floor through which runs a maze of 3/4 to 1 inch diameter pipes.
The pipes are placed crosswise rather than lengthwise and lie no more than 2 inches apart; an Olympic size rink of 185 feet by 85 feet has 7 to 11 miles of pipes embedded in its concrete floor. A very cold brine solution, or a glycol solution similar to the antifreeze used in cars, is continuously pumped through the pipes.
The solution draws off heat from the floor, as chillers run by compressors cool the solution to –5 to –15 degrees Fahrenheit each time it circulates. The warmer the air above the ice, the more solution is pumped through the pipes.
