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Temperature control by humidification

Humidity control can control more than just humidity, says John Barker
Value engineering has traditionally been a tool reserved for larger scale commercial projects, but the struggling economy means that cost cutting is now an integral part of any construction plan. Rather than a post pricing activity as has historically been implemented, value engineering is being employed upfront, pre-submission of pricing to clients

The concept of using humidifier technology to control temperature is not new, but the push for energy efficiency and increasingly simple controls have meant that it is growing in popularity.
Humidity technology's ability both to heat and/or cool the air can be best explained by detailing two applications which show how adding moisture to the air can result in differing conditions for different applications.

Generating steam

Steam rooms in wellness centres primarily use isothermal electrode boiler humidifiers to generate the steam within the treatment room. By controlling the electrode boiler on temperature the generator humidifies to 100 per cent RH (relative humidity), creating the steam-filled room that is so relaxing within a Turkish bath.

However, if we keep the humidifier runnning and keep it delivering steam after it has achieved 100 per cent RH it will have an effect on the temperature within the room. Evaporation cannot take place in this saturated condition so heat is generated and increases the steam room temperature to around the desired 40 deg C while also maintaining the steamy environment. The ingress of fresh air into the steam room is carefully regulated so that the temperature set point is only just achieved to ensure that steam production is constant and maintains the foggy atmosphere.

At the other end of the temperature scale, adiabatic cold water sprays or evaporative humidifiers are used to provide cooling where traditional air conditioning would be prohibitively expensive.

Large print factories and many other industrial processes where the presses or machinery generate excessive heat require humdity control and cooling - direct humidification can provide both. Typically, 6-10 deg C of cooling is possible by using the evaporation of water via fine sprays installed at high level where the cool water requires heat energy from the surounding air to enable the water to change its state into a gas - humidified air. Taking this heat energy to change the state of water cools the air, not the coolness of the water itself.

Maximising cooling effect

Evaporative humidifiers placed within air handling units can humidify return air up to very high humidity, achieving the maximum cooling effect which, when passed through a heat exchanger, cools incoming air by transferring heat energy.

A 1kW pump is all that is required to operate a high pressure water system or evaporative humidifier but it generates hundreds of kilowatts of cooling which is very energy efficient.

The effectiveness, efficiency, low capital cost and possible energy savings are all reasons why consideration should be made when selecting a humidification system alongside a heating or cooling system. Temperature and humidity are always linked psychometrically, but they also go hand in hand physically, with one helping the other to ensure the most effective system.

The author is sales director at Humidity Solutions
3 January 2013

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