Refrigeration – Automatic control – By accumulation on freezing surface – e.g. – ice
Patent
1993-11-29
1995-06-13
Tanner, Harry B.
Refrigeration
Automatic control
By accumulation on freezing surface, e.g., ice
62235, 374121, 340581, F25D 2900
Patent
active
054231841
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for measuring the temperature of the ice of artificial ice rinks where water is frozen to ice with the aid of cooling channels arranged in the rink and through which refrigerant is passed by means of a refrigerating system, the temperature of the ice being controlled by regulating the refrigerating effect or refrigerating capacity of the refrigerating system.
The invention also relates to a refrigerating system for carrying out the method.
The surface ice of an artificial ice rink has keen found to generate the lowest friction in contact with the runners of ice skates when the temperature of the surface ice is precisely -2.degree. C. The surface ice is softer at higher temperatures and the skate runners will therefore bite deeper into the ice. At lower temperatures, the ice is hard and affords a poor grip to the skate runners, besides becoming rougher as a result of the small ice crystals that form on the ice surface from the moisture contained in the air. Measurements show a marked change in friction precisely at a temperature of -2.degree. C.
At lower surface ice temperatures, the surface will also absorb more heat from the ambient air and incident heat energy from atmosphere or from the ceiling of an enclosed ice rink. The increased heat load at excessively low surface temperatures has been measured to about 11 W/square meters and degree Celsius. Thus, in the case of an icehockey rink whose surface temperate is too low by 1.degree. C. and which has an area of 1900 square meters, the heat load and refrigerating power requirement is about 21 kW. It will be seen from this that in a normal playing (operating) season of eight months, the refrigerating energy requirement will increase by about 120,000 kWh.
Artificially frozen ice rinks are constructed with densely packed refrigerating channels formed in gravel, concrete, asphalt, aluminium or plastic. An ice layer of 25-60 mm in thickness is frozen on the rink surface. Heat transmitted from the surroundings and absorbed in the surface ice is transported towards the colder refrigerating channels. Adjustment of the temperature in the refrigerating channels will thus regulate the refrigerating effect or capacity of the rink. When the texture difference between surface ice and refrigerating channels is increased, the traction of heat towards the channels and through the rink structure will also increase. This is achieved in practice by incorporating several power stages on the compressors of the refrigerating machine, these compressors functioning to cool down the channel-carried refrigerant to lower temperatures.
In order to maintain the surface ice at a constant temperate, it is necessary to cool off the same amount of heat as that absorbed in the surface. Thus, there must be maintained continuously a refrigerating effect which corresponds to the prevailing heat load on the ice surface.
This is very difficult to achieve and the surface ice will more often than not be at the wrong temperature. The heat load on the surface ice of an outdoor rink can vary from -50 W/square meters in natural cold to +25 W/square meters at high daytime temperatuers and as a reuslt of the influence of the sun's rays, during one and the same calendar day. In the case of enclosed ice rinks, the heat load during matches and while rinsing or washing the ice with water between periods of play can reach to above 200 W/square meters and then at some time prior to or after the matches reach to only about 50 W/square meters. The extent of the difficulty in continuously varying the refrigerating effect to correspond to the heat load is quite obvious.
Even though a surface ice temperate of -2.degree. C. will generate the lowest friction, there are other reasons why other temperatures are desirable during a normal day's operation. When the ice rink is not in use, during daytime periods and also during nighttime periods, the surface ice may be permitted to take a higher temperature, e.g. -0.5.degree. C., so as to reduce the refrigerating capacity required
REFERENCES:
patent: 4270361 (1981-06-01), La Barge
patent: 4690553 (1987-09-01), Fukamizu et al.
patent: 4700548 (1987-10-01), Roche et al.
patent: 4807443 (1989-02-01), Battson et al.
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