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Operating principle of snowmelters

Any snowmelter is a container with heat source which converts snow into water.

For turning snow into water it is required to heat the snow from ambient temperature to00 C and then a phase shift from solid body to liquid is to be made. However, this process is energy consuming. Exact calculation of heat amount required for snow melting becomes difficult because water in state of solid body is ice and snow is a composite substance comprising small crystals of ice formed in the atmosphere from steam, which is gaseous state of water.

 

H2O molecules in the air incorporate near the crystallization centers into a hexagonal lattice which forms ice crystals making a snowflake. The amount of heat or energy required to turn ice into water is a well known quantity, i.e. 330 kJ/kg. For comparison, iron transition from solid state into fluid state requires less energy: 270 kJ/kg. Therefore, in order to melt one kg ice cube, it should be heated by heat source of 91,5 W during one hour. For demonstration purposes, imagine a light bulb of 100 candles. It consumes the same amount of energy required to melt one kg of ice. Less energy is needed for snow to melt and it depends on many factors: snow density, amount of impurities and type of these impurities. Therefore, it should be kept in mind that it is hard to melt snow free of charge.

 

A vivid example was spring of 2011 in St. Petersburg when everybody could see a mixture of snow and mud in the places made ready earlier in spring for storage. This mixture was continuing to melt till midsummer regardless of warm spring and hot weather in early summer. Now the task is to choose an optimal source of energy and use this energy for snow melting with maximum efficiency. Heat from combustion of different types of fuel can be the source of energy: Diesel, gas, oil residue, solid fuel. Heat from fuel combustion can be transmitted: Directly, with the help of heat exchanger or through water heating. Electric energy can be also used and heat can be transmitted with the help of tubular electric heaters. Design, dimensions and capacity shall depend on the type of the source of energy to be used. In any case, about 25 kW*h shall be required to melt 1 m3 of snow. Although a large amount of energy is required to melt snow, this type of disposal in big cities is 2-3 times more effective than snow removal.

 

Apart from reducing direct costs related to snow removal, hidden consequences should be considered as well. Environment is affected seriously at the sites where snow is kept because it is brought along with mud. A vivid example is a snow disposal site on Krestovsky Island in St.Petersburg where the trees finally died. Snow removal with large dump trucks make traffic situation, which is already bad, even worse. Firstly, the traffic jams increase. Secondly, due to gas emissions into the atmosphere road pavements and buildings are damaged. Snow melting gives more regular load to sewage system.