Humidifier

[master53yoda]

Kristofor is dead on about the energy it takes 940 BTUs per pound to turn liquid water to vapor, it either gets the heat from the heater in the humidifier or it reduces the surrounding air to wet bulb temperature (close to dew point) in the case of the ultrasonic units.

[sparkeyjames]

I have a small humidifier that uses a small basin at the bottom channeled into a wick the air is drawn through the wick via a fan with multiple speed settings with or without humidity level sensing. Holds about a gallon of water. In a typical winter day I can go through anywhere from 2 to 3 1/2 gallons of water depending on how fast I run the fan. The downside is it is a bit noisy.

[alpha]

Thanks for the replies. It is terribly confusing. I realized the Aprilaire attached to my furnace was not going to give me enough humidity when it gets really cold.

The small stand alone units seem to all have advantages and disadvantages. Some generate a white dust that makes your house dirty. Some become moldy and require constant maintenance and cleaning. Others require expensive filters that must be replaced.

Sparkyjames, what is the make/model number of your unit? Would you recommend it?

Here is the one I was considering. Does anyone have experience with this one?

http://www.iallergy.com/product380/product_info.html

Bob

[phi1l]

That one is a nice size, although the price seems a bit high to me. It should do well for you. The only problem I see with it, is that you will have to be adding water at least twice a day. It would be nicer to find one that had a large enough reservoir so that you only have to fill it once a day.

I recommend that you empty it out about every week to remove the concentrated salts before they start to precipitate. At least once a week hit it with a shot of microbicide designed for humidifiers. If you live in an area where you need a water softener, use soft water only.

[Woodshark]

Kristofor is dead on about the energy it takes 940 BTUs per pound to turn liquid water to vapor, it either gets the heat from the heater in the humidifier or it reduces the surrounding air to wet bulb temperature (close to dew point) in the case of the ultrasonic units.

In a vacuum or under ideal lab conditions I would agree. I think it would be better to say it takes at least 940 BTU's per pound to turn liquid to vapor. Again under ideal conditions. In real world applications there is heat loss. Since the ultrasonic units are creating a fine mist of cool water droplets and not "boiling" or converting the water to steam, I'm not really sure that applies exactly. I think a ultrasonic unit would use less energy (once again, in the real world applications) if for no other reason then it does release a hot steam but a cool vapor. We don't want the heat, only the water vapor. A steam unit is going to have heat loss and also release hot steam which then gives up this heat energy to the surrounding air.

Not a true equal but a fun comparison. I can bake a potato in my electric oven at 400 degrees for 45 minutes or I cook a potato in my microwave oven for 5 minutes. When I'm done, the inside of both potatoes will be about the same but I bet you due to heat loss and other variables I've used a lot more energy to cook it in the oven over the microwave.

[phi1l]

I will try one more time. This is bringing back way too many bad memories from my chemical engineering thermodynamics class...

It takes about the same amount of energy to change water from the liquid to vapor state. I say about, because the actual heat of evaporation is slightly temperature dependent. So for all practical purposes water absorbs essentially the same amount of energy, independent of the humidifier.

No assuming it's winter & you have some sort of heating system that is maintaining air at a constant temperature. And, that the humidifying unit is in the area where the temperature is being maintained. Any energy consumed by the humidifying unit in the process of vaporizing water water, would eventually end up in the form of waste heat. But that wast heat will be heat that the air heating system will not have to provide. So, in effect, there is no "wasted" energy.

Now, you can talk energy cost, and a heat pump system is going to be much cheaper per BTU than resistive electric heating, so from a cost point of view, a humidifier that contributes as little energy to phase change as possible is most likely to be cheaper to operate over all.

So on that basis, you can expect that the cheapest on a cost per gal. basis will be those that blow room air over a large wet surface. Because they provide non of the phase change energy.

Next I would expect to be the Sonic humidifier, because they transfer energy directly to the water atomizing some any vaporizing some.

And Last would be the steam humidifiers, which supply all the phase change energy.

But that is strictly on a cost basis. Of the energy consumed by a humidification unit, all goes into either phase change from liquid to vapor, or into heating the air in the room. So in effect there is no energy loss.