How can thermal conductivity help you have a smooth skate?
Ice skating is a popular and enjoyable activity for many people during the winter months. A nice, smooth ice surface is something that we have come to expect when we are skating at an indoor rink, regardless of whether we are recreational skaters, or professional hockey players. For many of us, the most we see of the technology that it takes to keep an ice surface in good condition is the Zamboni. However, this is just the tip of the iceberg. Modern ice rinks are state of the art, carefully designed buildings that can cost hundreds of thousands of dollars a year to operate.
Below the ice rink surface is a system of layers that ensure the ice surface stays at the correct temperature to produce a safe, smooth surface for skating (Figure 1). In most rinks, a layer of concrete lies directly below the ice surface. Cooling pipes connected to the refrigeration system used to cool the ice surface run throughout this concrete block. Energy costs to run this cooling system are one of the largest portions of a rinks operating budget. Therefore, improving the efficiency of this system can save rinks a lot of money!
The use of concrete in this system is one of the few applications for concrete where a high thermal conductivity is desired. For most concrete uses, engineers want the concrete to have a low thermal conductivity. For example, a building constructed with concrete walls that have a low thermal conductivity will lose less heat in the winter, and therefore have lower heating costs. However, in the case of the ice rink, a low thermal conductivity concrete will put more strain on the cooling system. The pipes embedded in the concrete often contain brine, which is used as a secondary coolant in the refrigeration system. The purpose of this brine is to pull and absorb heat away from the ice surface as it passes underneath it. The brine then releases the heat when it reaches the chiller. This is where thermal conductivity plays such an important role in the efficiency of a cooling system. The higher the thermal conductivity of the concrete, the more heat the brine is able to pull away from the ice surface. The more heat that the brine absorbs, the less energy is needed for evaporation in other parts of the refrigeration system.
Although most thermal research in regards to concrete focuses on lowering the thermal conductivity, some research has been done to produce a concrete product specifically for use in ice rink floors. In 2012, researchers in Sweden produced a concrete that contained iron ore, a highly conductive material. Using the Hot Disk TPS, they determined that the thermal conductivity of their product was 58% higher than that of conventional concrete. They then designed two experimental floor plans that could make the most efficient use of their product. Theoretical modelling revealed that this novel concrete and the improved floor design increased the efficiency of the refrigeration system, which in turn decreased energy costs. The technology used in ice rinks is evolving all the time, and no doubt new discoveries will help to reduce costs even more.
The next time you go skating or attend a hockey game, take a moment to think about the amount of work that went into designing such a simple looking ice surface. Thermal conductivity can have an impact in many different areas of our lives, and the more we understand it, the more we can use it to our advantage!
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For more information on ice rink design and refrigeration systems visit these pages: