Last Man Posting

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Bellhead
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Re: Last Man Posting

#14641 Post by Bellhead »

Looks more like an industrial dehumidifier to me. Think air conditioner, but it doesn't make anything colder, just takes the water out of the air. We have a small one in the basement to keep mold from growing.

Explanation of dehumidifiers to follow in really small text:
When a fluid, be it liquid of gas, expands, it cools off, since that heat energy must be dispersed to the new volume. Also, when a liquid boils, it absorbs heat, and when it condenses, it releases heat. That's why sweat works. In an air conditioning scenario, a fluid (typically referred to as Freon) changes from a gaseous state to a liquid in the Condenser, releasing heat and making it feel hot, then changed back in the Evaporator by changing pressure and releasing heat, and making it feel cold. Cold surfaces will naturally cause water to condense, so water will continually drip from an air conditioner when used in humid environments.
Now, if you put the evaporator right before the condenser in the direction of airflow, you end up with a fairly neutral overall temperature change, but you also end up a surface cold enough to condense water out of the air. That's basically all a dehumidifier is, with a bucket or some such to catch that water.

End of explanation.
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Technic[Bot]
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Re: Last Man Posting

#14642 Post by Technic[Bot] »

I think I can do better:
A tiny explanation of dehumidifiers:
Spoiler!
In a cooling with dehumidification warm and wet air enters the system at a fixed relative humidity, there it is cooled eventually reaching the 100% relative humidity point. Any further cooling will cause the water to condense. In this process air remains saturated, until the final stage is achieved, this saturated air is then released back into the environment and condensed water is removed. Since the now drier air is quite cool it may be directed to a heating element to raise it temperature a bit before sending it back to the room.

Psychrometric chart for the process:
Image

References:
Website
For book nerds: Çengel, Y., Boles, M. and Kanoglu, M., n.d. Thermodynamics. Chapter 14 Air conditioning
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Re: Last Man Posting

#14643 Post by Bellhead »

OBJECTION!

*ahem*

Your explanation makes no indication of how the air is cooled, and states that the "saturated" air is what is dryer, and what is released, which is not quite true, as "saturated" implies that it is carrying a liquid (water, in this case) in some way, which is the opposite of what's happening.

This explanation also implies that the cooler, dryer air has the option of returning to the room as cooler air, whereas nearly all dehumidifiers put both the evaporator and condenser in the same air path (typically almost against one another), meaning that option is not possible.

And given that air must move through the condenser for the evaporator to function, some air must be heated by necessity, so simply letting that cooler air escape into the room would require a separate system that would only release warm air, completely negating the cooling effect anyway.
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Re: Last Man Posting

#14644 Post by Technic[Bot] »

In most air conditioning systems the cooling element is analyzes as ideal or separated. If you are conditioning air for people you can use a heat pump (basically a fridge) to move the heat from the air to somewhere else. But the source maybe anything: peltier cells, chemical reactions, or a plain old fridges. And may be completely separated from the air flow, i.e. use refrigerant in a closed loop.

Yes on cooling systems the idea is to take non saturated air ( air not on 100% humidity) and cooling it under its dew point to condense the water and then collect and remove manually. This air has 100% relative humidity, but lower specific humidity than in the beginning, despite air being in a saturated state there is less water in the air after the process, so you can simply recirculate the air until you get your desired specific humidity. Standard dry air, 0% humidity simply does not occurs naturally.

Finally can then add a heating element after cooling or as you said simply force the air through the condenser coil to reheat, this is more of a air conditioning thing, people like 25 °C and 50% relative humidity. But for an industrial dryer people may not care if it gets a bit cold. However reheating exhaust air in the condenser coil will lower cost and most residential dehumidifiers seem to be built that way. In any case as a dehumidifier in a closed room will eventually heat said room as all the energy is being put out of the water and back into the room.
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Re: Last Man Posting

#14645 Post by Foxx Trotter »

Since I've been away for awhile, I decided to come back and take the lead for a little bit. :mrgrin:
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Re: Last Man Posting

#14646 Post by Kellard »

Oh hi Marc
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Re: Last Man Posting

#14647 Post by Technic[Bot] »

After that commercial break we return to our regularly scheduled programming.

:raine:
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Re: Last Man Posting

#14648 Post by Neutral Smith »

You have a schedule?
If it moves but shouldn't: Duct tape. If it doesn't move but should: WD-40. With a hammer everything fits, and if it still doesn't fit: bigger hammer. If it can't be fixed with a hammer it's an electrical problem.

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Re: Last Man Posting

#14649 Post by Bellhead »

A stopped clock is right twice a day: And that's when I leave wherever I am, and go to the only other place I ever go.

6:00. Time to leave. AM or PM, doesn't matter.
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Re: Last Man Posting

#14650 Post by Technic[Bot] »

Yes I do!
9am 6pm work.
6pm 11pm still working but I am not supposed to
11pm - 7 am sleep. Errr.... late night work that is the only time to clean the roof!
7am 9am Pre work workout while working.
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Re: Last Man Posting

#14651 Post by Kellard »

I have a schedule. I'm just awful at following it.
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Bellhead
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Re: Last Man Posting

#14652 Post by Bellhead »

That's why my schedule only has one time on it.

Also, I have one of These. It's... far more helpful than I'd like to admit..
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Re: Last Man Posting

#14653 Post by Technic[Bot] »

Ever since the pandemic started it has been harder for me to keep the track of time. All days fell the same, the only reason I do not forget what days it is is because my computer has a calendar on it.
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Re: Last Man Posting

#14654 Post by Kellard »

Hmmmm
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Re: Last Man Posting

#14655 Post by Technic[Bot] »

"Hmmm...."

- Sir Kellard of Catarina

can't shake the feeling i made that joke before
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