Although ice baths are in widespread popular use by elite athletes around the world today, it was not long ago that the only way to cool a portable or mobile ice bath was with large amounts of ice. That was before iCool designed and developed the first practical portable cooling system for ice baths. These are the iCool’s that are seen at major sporting facilities all round the world today.
The iCool technology has freed athletes and sports specialists not only from having to find large quantities of ice, but for the first time they have the ability to carry out ice bath recovery and training sessions either at home or in the field accurately and consistently and for as long as the wish, which has not been possible with ice. Today, using an iCool it is practical to carry out tightly controlled ice bath protocols almost anywhere on demand.
The technology developed by iCool to make this possible turned out to be much more difficult than anyone would have expected and this is an explanation of what was involved. Today, more than 70% of the mobile and portable ice bath systems in use around the world are manufactured by iCool, so clearly we are doing something right.
To understand why it was so difficult to develop a practical compact portable system to cool a large amount of water and yet keep it small and mobile, it needs to be understood that water has the highest volumetric heat capacity of all commonly used materials and water has the second highest specific heat capacity of any known substance except ammonia.
What this means is that it takes more energy to cool or heat water than any other material. For example it takes approximately 45 times more energy to cool water than to cool air. So, water contains more heat energy than virtually any other substance or material and to cool it this energy must be removed. In scientific terms this is called negative enthalpy.
A good way to visualise what this means is to imagine your normal domestic refrigerator was filled completely with water instead of well spaced food items. It would take approximately 20 times more energy than your refrigerator is designed for to cool that water as quickly as an iCool could do it.
A standard single person iCool Bath contains approximately 350 L (92 US gallons) of water. Calculating the amount of energy needed to be removed to reduce the temperature of the water involves one of the deepest and most far-reaching concept in physics called thermodynamics and there are an almost infinite number of variables to be considered. In fact this complexity is why it is so hard for scientists to predict the weather which is after all just the circulation of heat energy. Fortunately however we can reduce this complexity down to a fairly simple formula which is accurate enough for our purposes here.
The simplest basic formula for calculating the amount of heat to be removed from the body of water is: Energy = Specific Heat X Weight X Temperature Difference.
Using the Imperial units of measurement used in the USA we can calculate this for 100 gallons of water as an amount of BTU’s required to cool the water by 20°F. Btu means of British Thermal Units and is a widely used measurement of the movement of heat in air conditioning systems. Once we know this number we can convert it to other metric measurement units.
So for 100 gallons:
BTU = 1×100 x 8.34 (weight of Gal of Water) x 20 (20oF drop required) RESULT = 16,680 BTU per 100 Gallons cooled by 20oF
So when cooling a standard iCool pool in the USA, a system capable of 16,680 BTU’s is required to reduce the water temperature in the pool by 20°F in one hour.
In fact, the iCool”Twin” mobile cooling unit is capable of exactly 16,000 BTU's and so can achieve this result comfortable and this is an outstanding achievement for such a compact mobile system. Most standard cooling systems capable of this performance would be several times the size and two or three times the weight. Not only that, the iCool is designed specifically for the purpose and has a large number of features that make it easy to use, totally automatic and reliable.
To convert this to metric units, 16,680 BTU’s is equivalent to 4800 Watts and a drop of 20°F in the range we are interested in is equivalent to 12°C, and as 100 US gallons is roughly equivalent to 350 L of water then we can say that the iCool”Twin” can reduce the water temperature in a standard iCool pool by 12° in the first hour. This in fact is the result we get consistently in real-world testing.
A standard iCool cooling system such as the “Cool” model has a performance around 25% less, however it is lighter and less expensive and completely adequate for most situations. The “Cool” model and the “Dual Temp” model that also has a heating system, to produce a reduction of 9°C in the first hour of cooling a pool of this volume.
This remarkable performance remains constant until installation losses begin to become important when the water temperature reaches a level substantially below the environment temperature. If no precautions are taken then this begins to occur when the water temperature is about 5°C below the ambient temperature and increases as the differential grows larger. Typically in the second hour of cooling, once this temperature differential is passed, between 25% and 30% of the work be- ing done by the cooling systems is being lost and therefore this portion of the energy is not cooling the water. This gives the impression that the cooling systems are slowing down, but in fact this is not the case, it is just that more and more energy is being lost to the environment.
So clearly it can be seen that although the iCool’s can do an excellent job in most situations the rate of cooling can be substantially improved and the amount of energy needed to do the job substantially reduced by paying attention to insulating the pool.
There are of course other things that need to be considered to improve efficiency such as high ambient temperatures and poor ventilation, but for cooling a large volume of water to very low temperatures, attention to insulation gives the best result.
The above simplified formula can be extrapolated to give a guide to the use of iCool’s for much larger pool’s. Using the larger capacity iCool “Twin” it is quite practical to cool much larger volumes of water, but of course it take proportionally longer. For such large pools the installations are normally more permanent and therefore the fact that it takes a few hours longer for the initial cooldown does not cause any problems.
Because of the extreme thermal inertia of water and the high cooling capacity of an iCool, once the desired temperature has been reached a system can very comfortably maintain the water temperature accurately even with the substantial heat load of several athletes using the system at the same time.
To stress, the one thing that will shorten the cooling time and reduce the amount of energy needed is to make sure that the pool is well insulated. The greatest loss is usually through the floor, especially a concrete floor as the concrete can provide a very large amount of heat back into the pool. It is also important to prevent droughts blowing over the water surface. This can be prevented by a simple cover.
The following table can be used as a reasonable guide to the available performance of each iCool model in various sized pools.
The table assumes that
a) The ambient temperature is in the range of 20 to 30°C (68°F-86°F).
b) The system has good ventilation to allow the heat to be dissipated.
c) The pool liner is not in direct contact with the floor. (at least an insulating mat is used).
d) If the pool is not an iCool inflatable pool which has a good built in insulation factor then the outer walls of the pool have an insulating material to prevent large losses due to condensation on the outer surfaces.
The table sets out the expected time taken to reduce the water temperature from 30C to 10°C (86°F to 50°F) which covers the most common conditions for most users.
|Pool Size||Compact "Cool"||Compact "Dual Temp"||Compact "Twin|
|350 Litre iCool Inflatable||2 Hrs 30 Mins||2 Hrs 30 Mins||2 Hrs 00 Mins|
|500 Litre iCool 4 Person Pool||3 Hrs 30 Mins||3 Hrs 30 Mins||2 Hrs 30 Mins|
|800 Litre Spa 8 Person Pool||5 Hrs 30 Mins||5 Hrs 30 Mins||4 Hrs 00 Mins|
|1000 Litre Spa 8-10 Person Pool||7 Hrs 00 Mins||7 Hrs 00 Mins||5 Hrs 00 Mins|
|1250 Litre Spa 8-10 Person Pool||8 Hrs 30 Mins||8 Hrs 30 Mins||7 Hrs 00 Mins|
|1800 Litre Spa 10-12 Person Pool||11 Hrs 00 Mins||11 Hrs 00 Mins||9 Hrs 00 Mins|
Please note that the times are derived from actual tests, whereas the times in red are calculated times only and would need to be verified by testing although we expect actual results obtained to be close to these times. Our research indicates that cool down times shown can be reduced further by setting up in an area with lower ambient temperature such as an air conditioned room or stadium, good ventilation and good insulation to prevent sweating and condensation on the pool outer surface and a cover on the top of the pool.
Cool down times obtained with the iCool’s is usually significantly faster than standard industrial chilling systems with similar power usage, resulting in much lower electricity costs. Purchase price is much lower than commercial fixed installations. Reliability and service life is at least as good as installed industrial systems. The major components in all iCool's are rated at between 10,000 and 20,000 hours of use before overhaul. Maintenance is much simpler and more flexible because an iCool cooling unit can be replaced in minutes not days.