Ammonium Hydroxide in Ice Rinks' The Ultimate Brine

1
Ammonium Hydroxide in Ice Rinks. The Ultimate
Brine?
The skating and ice hockey club in the small
village of Nittorp, about 100 km east of
Gothenburg, Sweden, faced a problem with its ice
rink. The rink was some 30 years old and
designed to operate with dry expansion of ammonia
in the rink tubes. 1985 it was change from dry
expansion of ammonia to an indirect system with
calcium chloride brine. Unfortunately, the
piping in the rink ½ carbon steel tubes
turned out to be too small. The brine flow was
too low to allow an even cooling of the rink, not
sufficient freezing at the end of the tubes. A
flow reversal system was thus installed with two
sets of pumps, one for each direction. About
every hour the flow was reversed. In 2007 the
evaporator corroded and had to be replaced.
However, the practically only possible material
of the heating surface titanium had a very
long delivery time and is expensive. The
management thus decided to have look at other
possible solutions.
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Replacement for calcium chloride

• The following replacement were considered.
• Ethylene glycol It is an excellent in the
  respect that it has a very large temperature
  range, a 30 solution can be used from -15 C/5
  F to well over 100 C/212 F, but the thermal
  properties are worse than calcium chloride and
  the viscosity is higher.
• Propylene glycol Thermal properties and the
  viscosity are worse than ethylene glycol.
• Potassium formiate Excellent thermal and
  hydraulic properties but corrosive (mild steel,
  zinc) and it also seems to leak more than normal
  (pumps, valves and fitting).
• Methanol-Water Good thermal properties but
  flammable. In some countries, just the mention of
  the word alcohol means that it it could be stolen
  and used as a drink.
• Ammonium hydroxide Excellent thermal and
  hydraulic properties. There were basically three
  consideration.
• - Evaporation
• - Comparison to pure ammonia and the use in
  public spaces.
• Corrosion.
• After a study, it was decided that this was far
  the best option.

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Properties of Ammonium Hydroxide (NH4OH)
NH4OH CaCl2-H2OFreeze- NH3 Bubble- Data
at Fp 10 K CaCl2 Bubble- Data at Fp10
Kpoint conc. point ? Cp ?cP ? ? Conc. point
? Cp ?cP ? ? Fp C C kg/m3 kJ/kg,K kJ/
m3,K W/m, K cP C kg/m3 kJ/kg,K kJ/m3,K W/m,K cP
-50(-58) 23.6 39.7(103) 937 4.37 4095 0.343 25-4
0(-40) 21.1 45.1(113) 939 4.29 4028 0.389 7.1 28.3
gt100 1284 2.685 3448 0.493 15.3-30(-22) 17.7 52.
3(126) 944 4.265 4026 0.421 4.2 25.4 gt100 1248 2.7
9 3482 0.511 8.1-20(-4) 13.4 61.9(143) 954 4.24 4
045 0.459 2.75 21.0 gt100 1199 2.985 3579 0.529 4.5
-10(14) 7.8 75.6(168) 971 4.218 4096 0.511 1.86 1
4.2 gt100 1128 3.33 3756 0.552 2.50 (32) 0 100
(212) 1000 4.194 4193 0.577 1.296 0 100 1000 4.19
4 4193 0.5767 1.3
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Result of the conversion
A manometer, which was not exchanged, was
corroded. 30 years operation with ammonia and
calcium chloride had thoroughly fouled the
circuit. The ammonium hydroxide was black. The
first years could be considered as the cleaning
year. A filtration of the ammonia solution
showed a sludge, similar to the one found in
CaCl2 for ice melting on roads, No measurements
were made of the power consumption but the pumps
were running at lower speed. The impression of
the operators was that the ice formation
responded much quicker than previously to changes
in the brine temperature. This was confirmed,
when one of the pumps failed, thus no flow
reversion. It was not noticed for over a week,
i.e. no major difference between the freezing
behaviour of the inlet and exit of the tubes. An
interesting notice was mad at the ice rink in
Tours, France, converted to ammonium hydroxide a
couple of years ago. A leakage at the rink, was
not discovered for over a year. A calcium
chloride leak would have destroyed the ice. No
smell has been noticed, see also above.
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A covered passage above the rink
The tunnel with the feeding pipes.
The rink
The hall
Identification of some hot spots in an ice rink.