The $30 includes all the heat energy added to the room period. Draw a closed box around the room with the dehumidifier in it. Whatever energy, ie the $30 worth of electricity, comes into that closed room, is heat that is added to the room.
It's a dehumidifier. It can move 5x, but it's moving it from one side of the unit to the other. The moving doesn't add to or subtract from the heat in the room. What does add to the heat in the room is the $30 worth of electrical energy that is added over the course of a month and which winds up as heat.
Put 10 watthours (or Btus or whatever you want) of electric energy into it.
Get 10 watthours of heat energy dumped to the room as waste.
Also get 50 watthours of heat energy moved from place to place. BUT! That 50 watthours of energy includes the heat in the air moving from front to b ack AND the conversion of water vapor to liquid. The moving of the air doe sn't add to the heat in the room but the condensing of the water does.
at 50 watthours of energy includes the heat in the air moving from front to back AND the conversion of water vapor to liquid. The moving of the air d oesn't add to >the heat in the room but the condensing of the water does.
Wrong. It would be a gross violation of the principle of conservaton of energy if somehow heat was miraculously added to the room. The dehumidifier moves heat from one place to another. The conversion of water vapor to liquid is exactly that, the movement of heat within the room. It does not add or remove heat from the room. Phase changes don't affect the total energy within the assumed perfectly insulated room. The only total heat change in the room in your example is the addition of heat from 10 watthours of electric energy. If it were possible to run that dehumdifier system without putting the 10 watthours of electricity into it, there would be zero net change to the heat in the room by the dehundifier. It moves heat, it doesn't create it.
Trader's right about not changing the total energy.
However, the phase change takes latent heat of vaporization, and changes it to sensible heat (to wit, party of the second part), that being rise in temperature.
Well, of course he's right, you can't get something for nothing.
However, we're talking about the difference between adding 6.5 kWthr/day of heat to the room, from running the equipment, and 12.62 kWthr, from runnin g the equipment plus the latent heat. We agree since cold air goes out one hole and warm air out another the sensible heat is a wash, but I tend to t hink the latent heat actually goes into the room.
of heat to the room, from running the equipment, and 12.62 kWthr, from runn ing the equipment plus the latent heat. We agree since cold air goes out o ne hole and warm air out another the sensible heat is a wash, but I tend to think the latent heat actually goes into the room.
Sigh.... But apparently not. There is no however. In an ideal, perfectly insulated room, unless you put some energy from outside into it, the energy content is fixed. The *only* increase in heat from the dehumidifier is the 6.5kwhr from the electrical energy added to the room. The latent heat doesn't go into the room, it's already there.
y of heat to the room, from running the equipment, and 12.62 kWthr, from ru nning the equipment plus the latent heat. We agree since cold air goes out one hole and warm air out another the sensible heat is a wash, but I tend to think the latent heat actually goes into the room.
Ah. I see what you mean.
Yes, you're right.
But, latent heat has been converted to sensible heat. The air temperature will go up by more than the amount predicted by the 6.5 kWthr of energy add ed; in fact it will go up by double that amount.
That's a new objection. Yes, you can factor that in, but it's a complication that's then hard to account for. The range of possibilities could range from the cold water going straight down a drain, to the cold water accumulating in the bucket inside the dehumidifier, taking on whatever temp exists inside the area that it sits in, then being dumped down a drain, to the water staying in the room and used to water plants. And if it leavest the room, then you have make-up air coming into the room to replace it. That's why I used the simplified model of an ideal, perfectly insulated, closed room. And it seemed like you were OK with that, because it looked like your argument was that the condensation of water vapor out of the air changed the amount of heat in the room regardless of whether that water stayed in the room or left the room. If it stays in the ideal, closed, perfectly insulated room, then the only heat change in the room is the change from the electrical energy flowing into the room to run the dehumidifier. If you want to add the complication of the condensate leaving the room, then yes, that energy transfer would also have to be factored in.
air temperature will go up by more than the amount predicted by the 6.5 kWthr of energy added; in fact it will go up by double that amount.
1) The ideal room has an old man with a cigar who yells at everyone "close the damn door"
2) Most of us humans notice the rise in temperature, rather than the loss of latent heat which was converted away.
The original question was whether the dehumidifier heated up the room, whic h to any common sense person means did the air temperature in the room rise .
And the the original answer was yes, by ONLY the amount of energy added by the mechanical operation of the equipment, which we know is an average 6.5 kWtHr/day. The air temperature in the room would rise exactly the amount p redicted by adding 6.5 kWthr/day.
That was assuming that the air cooled by the cold coil and reheated by the hot coil never left the room and so heat was moved back and forth but never lost or gained.
But as Stormy pointed out that neglected a factor. There is heat recovered by condensing the water vapor into liquid at the same temperature, and it' s a lot of heat. It ends up being an additional 6.1 kWtHr/day.
So I have contended that the temperature in the room will rise by almost do uble the amount of the 6.5kWthr used.
Where did that 6.1 kWthr/day go? It went into the cold coil, circulated th rough the refrigerant, and popped out the hot coil into the room air.
The water it came from can't be reheated and reevaporated, because it went down the drain (at least in my house I have the basement dehumidifier piped to the drain).
By the way, that means a humidifier is roughly 190% efficient at heating yo ur house - you put in 6.5 kWthrs of energy and get back 12.6 kWthrs of heat .
"With a dehumidifier, it's only removing humidity, while adding heat. Does it really add heat? " Words have meaning, especially when you're talking about physics.
That is correct.
No one said that.
Which is, once again, assuming for purposes of discussion, that it's an ideal perfectly insulated, closed room.
Ralph and I always explicity accounted for the 6.1kwhr of incoming electrical energy. In fact, I said it's the *only* increase in heat. There is no extra 6.1 kwh per day of heat.
No, only now are you starting to talk about temperature. I previously pointed out that I thought you were mixing up heat and temperature.
No shit Sherlock. At least that's where most of it went, assuming you're talking here about the actual 6.1 of electrical energy used.
We were talking about an ideal, closed, perfectly insulated room, not your house.
No idea where than number came from. And once again, you're conflating
*heat* and *temperature*. You could get an increase in temperature, but not an increase in heat. Good grief.
ent down the drain (at least in my house I have the basement dehumidifier p iped to the drain).
Doesn't matter. The water can sit in the humidifier reservoir in the room forever. Re-evaporating that water is the ONLY way to lose the 6.1 kWthr h eat gained from condensing that water. That heat was gained from the phase change of the water, not from changing the temperature of the air or water . That's why it is so large, roughly equal to the mechanical energy added. That heat stays in the room but is transferred from the water to the air. So technically yes, it was in the room all along, but it was trapped in t he roughly 1% of air that is water vapor not in the 99% rest of the air.
It is a good thing it is not an ideal closed perfectly insulated room. If it were, assuming a 20x30x8 room, and if I did the math right (you are welc ome to check it) the temperature rise from the electrical energy used would be 160 degrees and from the water condensed, 150 degrees.
went down the drain (at least in my house I have the basement dehumidifier piped to the drain).
Well it does matter. If the water sits in the humififier reservoir, you have a *closed* system. Then, the only heat added to the room is from the electricity consumed. If the water goes out of the room, then you have an array of complex situations to consider.
ed from condensing that water. That heat was gained from the phase change of the water, not from changing the temperature of the air or water. That' s why it is so large, roughly equal to the mechanical energy added. That h eat stays in the room but is transferred from the water to the air.
There you go again, conflating heat with temperature.
So technically yes, it was in the room all along, but it was trapped in t he roughly 1% of air that is water vapor not in the 99% rest of the air.
f it were, assuming a 20x30x8 room, and if I did the math right (you are we lcome to check it) the temperature rise from the electrical energy used wou ld be 160 degrees and from the water condensed, 150 degrees.
Temp rise and heat are two different things, capiche?
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