Christmas parties in most cases represent a feast with entertainment program of varying degrees of ingenuity. But we at Mail.Ru Group decided to make something more interesting sports and technological. So in our gym there was a real ice rink. About how it is arranged, read under the cut.

Technology

The size of the mounted skating rink will be 12 x 23 m. For comparison, on average, “street” skating rinks have a size of 20 x 40 m. How can a full-fledged skating rink be made in a normal room? First, the floor is covered with thermal insulation about 5 cm thick and an airtight film. Thermal insulation is needed not only to protect the floor, but also to prevent heat transfer. The room is warm, and if you do not make a protective layer, then the cold will go to the floor and have to use a much more powerful refrigeration unit.


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The so-called ice-mats, which are original porous mattresses in which parallel long tubes of small diameter are laid in parallel, are placed on top of the film.



The total length of the tubes in our rink is 8.7 km. At the ends of the ice mats, all the tubes are connected to a single closed loop, which includes the refrigeration unit (aka chiller). It cools the coolant (polypropylene glycol), which circulates through the tubes of ice-mats. Above, ice-mats are filled with water, which gradually cools and eventually freezes.



The rink will freeze for three days, and during this time about 15.2 tons of ice will be created, that is, 276 square meters with a thickness of about 6 cm. The surface immediately turns out to be sufficiently level so that you can roll without prior alignment.



But you will have to update the rink every day, because under the influence of ice skates ice crumbles, irregularities appear. People who will update the ice, called aismakera. Their main tools are special devices, which are T-shaped tubular mops. A series of small holes were made in a transverse crossbar with a width of about one meter, through which water with a temperature of +55 degrees is applied to the attached strip of fabric. This fabric is pulled over the ice, evenly wetting the surface. Water fills the hollows, floods the top layer of ice, and then quickly freezes. The result is a perfectly smooth roller.

Refrigeration unit

The principle of operation of the chiller in brief is as follows: the compressor pumps the freon vapor into the condensation compartment under pressure. As the name implies, here Freon is condensed and fed to the so-called thermal expansion valve and evaporator. The latter is, in fact, a heat exchanger in which polypropylene glycol is cooled to -7 ... -12 degrees (freon boils at a temperature of -15 ... -18 degrees). Then freon vapors from the evaporator are fed back to the compressor - the cycle is closed. The refrigeration unit during ice freezing consumes about 100 kilowatts per hour, and its cooling capacity is 150 kilowatts per hour. To maintain frozen ice, about 50 kilowatts per hour is spent.



By the way, despite the large area of ​​ice, the temperature in the room almost does not decrease due to the effective system of air ventilation of the building. Instead, the humidity will rise, since the ice will not so much melt as it will immediately evaporate.

Interesting Facts

• The sides of the skating rink are not attached to the floor, they are held at the expense of freezing in the ice. Also, a grid with the Mail.Ru Group logo is frozen into the ice - it can be clearly seen from the surrounding gymnasium of the gallery.
• A team of 8 people mounted the skating rink for the day, but the dismantling will take about 30 hours, because you have to gently prick ice and take it out of the building on carts. Before this, the ice is "perekalivayut", that is, it is cooled to the lowest possible temperature. At the same time the ice becomes much more fragile and it becomes easier to break. In addition, cooling allows you to insure against premature melting of ice.
• By the way, an open-air rink in Gorky Park is now made using the same technology. There, ice-mats are applied mainly black. However, black ice mats are visible through the ice, and the surface of the rink turns out to be dark - respectively, it absorbs infrared radiation better and heats up more intensively. Therefore, ice is simply painted with special white paint. Indoors, you can get by with dark ice mats, since a significant proportion of infrared radiation will be delayed by glazing.
• On such artificial ice rinks, it is desirable to maintain the minimum possible ice thickness. The reason is purely practical: daily leveling of the surface using the above-described "mops" leads to a gradual increase in the thickness of the ice. And since it is a good thermal insulator, in order to maintain the required temperature it is also necessary to gradually increase the capacity of the refrigeration unit. This means an increase in the already very large energy consumption. To avoid this, you can use special "combines" for rollers, which first cut the top layer of ice, and then fill irregularities.
• If some overly zealous user digs a hole in the ice (which is quite possible) and damages one of the tubes in the ice-mat, then the coolant will fall on the ice. At first it will look like a puddle of water, and then it will begin to be absorbed, turning ice into porridge. This site must be quickly localized and collect all spilled coolant. Since its freezing temperature is much lower than that of water, there will simply be no ice in this place.
• Different kinds of sports maintain different temperatures of ice. For the same hockey, it is lower, so that the ice becomes tougher. For figure skating, on the contrary, ice is maintained at a higher temperature. Although often the skaters themselves are asked to make the ice necessary rigidity. Skaters have their own temperature. All these differences affect not only the mechanical properties of ice, but also the speed of skiing. This is also influenced by the purity of the water used for pouring. The more impurities in it, the lower the slip speed.

By the way, all the photos on the ice skates that you take on New Year's Eve can be your ticket to the most geeky rink in Moscow. Add to the photo tag #happygeeks, for the most fun, cool we will give skates and choose five, whom we invite to the Moscow office of Mail.Ru Group.