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Post by Andrew on Sept 12, 2013 6:59:06 GMT
I am convinced that a dehumidifier warms the air it dries, more than the power required by the dehumidifier.
Obviously there is no free lunch here. We need a source of heat to provide humid air that contains the latent heat of condensation, that we are going to use to heat our room.
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Post by nonentropic on Sept 12, 2013 9:58:09 GMT
and so, its simple science the water in the air condenses and the liberate energy of condensation adds to the energy dissipated by the compressor etc.
no mystery here.
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Post by numerouno on Sept 12, 2013 13:06:36 GMT
The practical dehumidifier works by cooling down a mechanical part and driving air to condense on it.
Any heat contained by the moisture in the air will also condence on this surface, only making the task of cooling harder.
You will end up using external energy both to overcome the reclaimed heat contents of the air, and to also cool it down to below the condensation point that you would need to do anyway.
The world would love free heating energy, but a dehumidifier is not the way to do it.
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Post by Andrew on Sept 12, 2013 15:59:16 GMT
The practical dehumidifier works by cooling down a mechanical part and driving air to condense on it. Any heat contained by the moisture in the air will also condence on this surface, only making the task of cooling harder. You will end up using external energy both to overcome the reclaimed heat contents of the air, and to also cool it down to below the condensation point that you would need to do anyway. The world would love free heating energy, but a dehumidifier is not the way to do it.
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Post by Andrew on Sept 12, 2013 16:12:19 GMT
The practical dehumidifier works by cooling down a mechanical part and driving air to condense on it. Any heat contained by the moisture in the air will also condence on this surface, only making the task of cooling harder. You will end up using external energy both to overcome the reclaimed heat contents of the air, and to also cool it down to below the condensation point that you would need to do anyway. The world would love free heating energy, but a dehumidifier is not the way to do it. Why do you keep repeating this silliness about free energy?? A dehumidifier is a heat pump and there is nothing free about heat pumps The dehumidifier has a cold side and a hot side. The air enters the cold side and exits via the hot side. Any heat removed on the cold side must reappear on the hot side. The dry air contains less hidden heat so heat must have appeared somewhere else.
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Post by nonentropic on Sept 12, 2013 21:50:50 GMT
spot on
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Post by numerouno on Sept 12, 2013 23:35:20 GMT
Andrew, the heat in the moist air will be dissipated at the point where the cooling and condensing takes place. This heat retrieved there actually counteracts what you want, which is to keep the temperature cool so that the dehumidifier can continue to operate. Yes, the heat will have appeared, only to be eliminated right on the spot.
In the end, you will spend energy to defeat the energy you are gaining, and for the rest of the device to operate by shifting the heat.
At the end of the day, you will have spent far more energy than would have been necessary had we had a perfect device that would "know" only the heat contained in the moisture. Most of the hot air at the other end is just casual heat transfer that is necessary for the operation but does not add positively to the overall heat budget, only the losses are drawn from the utility anyway and will be billed.
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Post by nonentropic on Sept 13, 2013 0:14:04 GMT
Numerouno that's just drivil
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Post by numerouno on Sept 13, 2013 0:37:13 GMT
"Numerouno that's just drivil"
Is that related to "drivel"?
In that case then, please provide links to a proper study that says there is free heating energy to be had.
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Post by magellan on Sept 13, 2013 3:01:28 GMT
Having heated with wood (both in solid and pellet form), corn and other sorts of organic material for many years, placing a pot of water on the stove was to keep the air from drying out too much. I didn't get nose bleeds from dry air, but the rest of the family were more sensitive. Itchy skin, dry eyes and throat though were common for everyone. A humidifier had to be used at times. But there are other reasons. More humid inside air makes you feel warmer. One week in Arizona at 85F, then a week in Louisiana at the same temp and it really isn't difficult to understand.
But that's not all; dry air does not retain heat well, so it inevitably goes to the ceiling and finds the cold spots, leaving the space where you live colder. More humid air allows the heat to be better distributed. I've taken measurements in years past and that is the case.
I see this every year in my lab when the humidity increases as Spring sets in. It's supposed to be "climate controlled", but I end up having to manually adjust the dehumidifier to take the moisture out of the air to prevent rusting of the equipment (note to self; complain to maintenance dept). It also feels cooler even though the temperature does not change (kept at 70-72F).
As they say, it ain't the heat, it's the humidity.
What's the primary purpose of an air conditioner? To remove humidity. Cool air blowing through the vents is the secondary effect. In a room at 75F with 20% humidity it will feel cooler than at 60%.
I must agree with Numo in principle regardless.
If the inside of your home has excessively high humidity in the cold winter months, better check for leaks and drafts and poor insulation. I could see the use of a dehumidifier to remove the moisture to levels that don't promote mold, dust mites and condensation on the windows, but to actually warm your house at less cost? Wouldn't a window A/C unit be all the rage for heating your home?
It seems to me with a dehumidifier all you're doing is exchanging heat (energy) from one location to another, not outputting more heat (energy) than what is being input; that would be perpetual motion. 15+ years of heating with a stove doesn't lead me to believe removing humidity makes it warmer, or at least feel like it.
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Post by Andrew on Sept 13, 2013 4:21:40 GMT
Andrew, the heat in the moist air will be dissipated at the point where the cooling and condensing takes place. This heat retrieved there actually counteracts what you want, which is to keep the temperature cool so that the dehumidifier can continue to operate. Yes, the heat will have appeared, only to be eliminated right on the spot. In the end, you will spend energy to defeat the energy you are gaining, and for the rest of the device to operate by shifting the heat. At the end of the day, you will have spent far more energy than would have been necessary had we had a perfect device that would "know" only the heat contained in the moisture. Most of the hot air at the other end is just casual heat transfer that is necessary for the operation but does not add positively to the overall heat budget, only the losses are drawn from the utility anyway and will be billed. 1. I am not claiming such a device can economically heat our home. However heat available is input energy plus latent heat extracted during cooling and then produced as sensible heat upon reheating the air. 2. We are using a heat pump 3. >>the heat will have appeared, only to be eliminated right on the spot. As with ice making no heat appears. When we make ice the temperature remains higher during cooling. >>you will spend energy to defeat the energy you are gaining, If the cold side of the heat pump is warmer due to latent heat, then the hot side must be warmer. The same principle applies to a ground source heat pump. The warmer the ground water the higher the temperature available to heat our home.
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Post by numerouno on Sept 13, 2013 4:25:50 GMT
Andrew, you have, as it were, both the inside and the outside heat pump units inside the same house in the "dehumidifier heat pump" scheme. Therefore, what you actually gain in heat are the losses of the system.
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Post by Andrew on Sept 13, 2013 4:37:21 GMT
Andrew, you have, as it were, both the inside and the outside heat pump units inside the same house in the "dehumidifier heat pump" scheme. Therefore, what you actually gain in heat are the losses of the system. Losses of the system? I am finding it hard to follow what you are saying. With the usual scientific use of the word 'losses', with a dehumidifier there are effectively no losses. Essentially all of the energy that is going into that dehumidifier comes out of it to warm the room. 1. If the air was dry then in theory heat produced on the warm side could only come from heat removed on the cold side In practice since the motor is heating the refridgerant we can expect the warm side to be warmer than otherwise. Warming energy produced is equal to input energy only. 2. If we then switch to humid air then the cold side becomes warmer than for dry air, and the warm side must become hotter. Warming energy produced is equal to input energy plus latent heat of condensation. 3. To rehumidify the room we would need to allow the water to evaporate into the dry room, whereupon the water would become colder, and the air coming in contact with the colder water would become colder
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Post by numerouno on Sept 13, 2013 10:49:37 GMT
Essentially all of the energy that is going into that dehumidifier comes out of it to warm the room.
Oh noes, I thought there would be a storage cabinet for it!
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Post by Andrew on Sept 13, 2013 13:41:05 GMT
Essentially all of the energy that is going into that dehumidifier comes out of it to warm the room.Oh noes, I thought there would be a storage cabinet for it! You were using the word 'losses' in a confusing manner and i sought to ensure we were understanding each other
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