Commercial HVAC Humidfication System Efficiency

[bigAlittlee]

Trying to come up with arguments for various methods of humidification in large scale (high-rise building) HVAC systems.

I don't know the answer myself and will be spending the next couple hours trying to find it and was wondering if anyone had any good information or opinions on preferred humidification methods.

Because we are in the LEED world, energy cost difference is key and I am having a hard time understanding the impact on an energy model, considering ASHRAE 90.1 doesn't specify a baseline design for humidification systems.

Basically, the project in question is in China, where steam humidfication is the standard, and I was to present an arguement that a steam or fogger system would be more energy efficient.

Anyone have any thoughts or suggestions?

Thanks.

 

[KiwiMace]

I can't say i've ever calculated this but...

Given that (deliberate) humidification in comfort systems almost always goes with heating, it would make sense that direct injection of steam would be more efficient on the airside part of the equation as the steam injection would not require the addition of heat that comes with misting water at a lower temp which evaporatively cools the air.

The waterside of the equation says that cold/room temp clean water is a lot less energy intensive to produce than clean steam - there might be the same kJ/kgK (Btu/lbm.degF) to make water at a given temp vaporize into steam, however misting is done at the point of use, and the steam has substantial production and transportation losses.

Overall, I think a misting recirculating water system would work more efficiently, particularly when the water is substantially warmer than the air - preheated even.

Other high efficiency systems like ultrasound are a maintenance joke and i'm not sure would peg out on a whole building scale anyway.