Question: How do domestic chemical dehumidifiers work?

[Donwill]

Before asking the question let me explain what I know of them.

Basically they have a wheel which is charged with a dessicant such as Silica Gel or Lithium chloride or some other reversible hygroscopic compound. Air is drawn in from the room by a fan and passes through a sector of the slowly revolving wheel which absorbs the water vapour before being passed out again to the room in a dryer state, so far so good.

Now the water which has been absorbed by the hygroscopic material in the wheel needs to be removed, which is done so I understand, by heating it up in another sector of the revolving wheel which would drive the water off in a vapour state. The water ends up eventually in a liquid state in a reservoir which is periodically emptied.

That being the case the sensible heat applied to increase the temperature of the dessicant in that sector of the wheel AND the latent heat released in condensing the water vapour must be contained in and increases the temperature of the room. However:-

Q.) There must be another stage surely, which condenses the water vapour to the liquid state, how is it powered ? Is it a refrigeration coil, a peltier device or what? How do they do it?

Don

[Stuart Noble]

The one I had was just a fan and a refrigeration coil with a container under it to collect the water. Maybe they're more sophisticated nowadays.

[Bob Minchin]

I assume (always dangerous!) that the hot, moisture laden air then goes into a condenser in close thermal contact with the air maybe even a heat exchanger connected to the incoming air path which would stay at a relatively constant temperature ie room temperature.

Bob

[js.b1]

I did wonder if it was peltier.

However I did notice what appeared to be glass fibre covered wires visible near the Ruby-Dry outlet. The heat output is high, so it may simply be a heater rather than peltier (which might be insufficient re wattage, but otherwise useful re one-side heats & one-side cools re condensation).

If you go to the EHS (think that is the company) and look up the exploded diagrams, X-Dry I think is on there, it will give an idea of what is actually inside. More parts than you think from memory.

[Donwill]

You could be right Bob, I had a look at the EHS site as suggested by JS bl and came across a drawing on:

does seem to suggest a close proximity to the inlet air. Cheers Don

[NT]

AFAIK, and I lack experience with them, there are 2 ways the output damp is handled. One is to just vent the hot damp air outside, the other is to heat it hot in a small volume of air so the resulting hot damp air is very high in moisture. Then simply cooling it to room temp causes the precipitation, plus a small volume of damp air released.

NT