www.swimmingpoolnews.co.uk
Condensation DEC 2010 SPN
57 AIR CONDITIONING!
Cutting corners dealing with controlling indoor pool condensation is a false economy when it comes to providing safe swimming facilities for indoor pools. Locating a large pool of warm, heated water within, what is basically just another room, creates a problem which has to be dealt with. So understanding what is going on with the pool atmosphere and knowing how to deal with the humidity is becoming an important skill
A
swimming pool is like a bath tub, but on a much larger scale.
When the pool water is warmed to a usable temperature, typically between 28°C and 30°C, the heated water will emit steam from its surface into the room air. Basically, the water is evaporating and is being transferred from the pool into the air in the room.
Once you accept this simple process then it’s clear why swimming pools have to learn to deal with condensation.
Unregulated, this process will continue with the result that the pool room air quickly becomes over loaded with water vapour. At this stage condensation may be apparent on all internal surfaces of the pool room, leading to rapid deterioration of the decor and possible eventual structural problems.
Therefore, methods of ‘control’ are clearly essential if an indoor pool is to function without critical problems.
Swimming pool environments have also changed significantly in recent years, specially in leisure pools. Higher water temperatures combined with an increase in the number of bathers, has led to higher levels of chemical disinfection.
Chlorine-based disinfectants are the norm, which together with contaminants introduced by bathers, produce chloramines. High air temperatures significantly accelerate corrosion. Atmospheric moisture in pool buildings comes from evaporation of pool water and as droplets from the turbulent water features that have become increasingly common in leisure pools. The atmosphere of indoor swimming pools is one of the most aggressive to be found in a building environment.
Once you understand the problems then there’s a solution not far behind and swimming pool dehumidification products available on the market range from simple small dehumidifiers mounted on the wall in the pool room to advanced full climate control systems located in the plant room and distribute air around the pool hall via a ventilation duct work system. These sophisticated systems now provide air heating, ventilation, air cooling, pool water heating and even now generate their own heat. Two specialist pool companies, Heatstar and Calorex have built up a huge knowledge and understanding of the problems facing pool owners and have developed their own systems
HOW POOLS ARE COPING WITH CONDENSATION AND DAMPNESS
Willowburn Sports Centre, Alnwick. A pair of identical Calorex HRD25 air- handling units have been working perfectly in tandem to maintain ideal atmospheric
conditions offering heat recovery to either the pool water or the pool hall air system depending upon demand at the Willowburn Sports Centre at Alnwick in Northumberland. Two pools operate at different water temperatures i.e. main pool at approx. 28°C and teaching pool at approx. 30°C. Pool hall air temperature is maintained at a minimum of 1°C above the pool water temperature, providing an air change rate of around six per hour in the pool hall, introducing high volumes of fresh air via the plant and controlling humidity levels within a band of 55% to 65% RH.
and products to deal with them.
Calorex Managing Director, Richard Carrington, warns cutting corners on condensation in public swimming pools could spell disaster. “Under the specific temperature conditions near the ceiling, chlorine containing chemical species in vapours from the pool water can condense onto the stainless steel components and dry out. As this can be a repeated cycle, very aggressive concentrations of chlorine-containing species may build up.
“High humidity is the result of evaporation of water into the air that is greatly increased by larger pool surface areas with heavy bathing loads. “Other factors that will increase water evaporation include increased pool water temperature and lowered space temperature. Environmental control systems can prevent the build-up of humidity by controlling the amount of moisture in the air and therefore controlling condensation.
“A typical leisure centre pool can contain up to a million litres of water heated to around 30°C. Water evaporates from the surface at a rate of hundreds of litres every hour. Evaporated water needs to be removed or it will turn to condensation that will immediately start to cause problems.
“At normal pool temperatures, 2 kWh of latent heat is recovered for every three litres of water vapour condensed. The air temperature has been lowered by the removal of sensible heat to enable the dehumidification process to proceed and both the sensible and latent energy come together in the refrigerant gas. This is now raised to a higher temperature by the compressor and used to heat the pool water as well as the pool air. “When the humidity rises above the target level, a compressor is switched on, together with the integral heat pump circuit and the heat recovery dehumidification process starts. Latent and sensible energy available in the moist air is recovered and returned to the pool water and air, via the built-in heat exchangers.
By Alan Lewis
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