Recommend a dehumidifier for drying clothes in an apartment

K.Flyer

We used to get a lot of calls from management companies and apartment owners asking us to check out the reasons for mould on the inside walls of the apartments / houses suspecting there would be a leak somewhere.
Most of the time the mould was caused by people drying clothes on radiators or on clothes horses with some other form of air directed at them. Because buildings are becoming more and more air tight the moisture has nowhere to go, so it gets absorbed into the plaster and causes very unhealthy mould problems.
In our own home we used to have an old tumble dryer with the open ven and it was quite expensive to use. When it broke we got a new B rated condensor dryer and its much cheaper to run and all the moisture is contained in a tank to be emptied out.
The machine has a multitude of settings for so many types of clothes and they are now washed, dried and folded in less than a few hours and they are never shrunk or damaged if used correctly.
For all of that my recommendation is a good quality condensor dryer.

metroburgers

Anyone have a simple but effective D.I.Y. dehumidifier (wardrobe type) solution I could make e.g. 2 litre/silica gel combo that actually works?

Gatling

Has anyone found the dehumidifier's ease chronic lung condition's such as asthma when using one

The_Conductor

Gatling wrote: »

Has anyone found the dehumidifier's ease chronic lung condition's such as asthma when using one

It depends on the dehumidifier- and whether you're using the filter associated with a particular model or not, but yes, it can help- providing you use it properly. Obviously different models may work differently. My one has a Heppa 9 filter system (don't ask me what this means).

Piliger

So we have a recommendation for a Dimplex Dehumidifier and a Mitsubishi.

Does anyone else have a recommendation for a good desiccant model that is quiet ?

The_Conductor

Another compressor based unit- this time from Aldi.
On sale this Sunday (the 6th of October)

Link here

This one has a special setting for drying clothes on a clothes horse.

Tails142

I use a delonghi one, works fine. Bought it in argos so probably paid over the odds for it. Originally bought it to deal with damp issues (old building) but now use it to dry clothes too

Piliger

Hi guys after doing a bit of research it seems to me that with an apartment like mine, that is rarely warm in the winter, a normal compresor dehumidifier would not work at it's best. It needs a much warmer room to work right.

However there is such a thing as a Desiccant Dehumidifier which does not use a compressor. It uses a water absorbing material that is rotated and it absorbes and then is 'cleaned' of the water as it circulates. Hence it is also much quieter. This kind of device works independent of the temperature and in my apartment where it is usually 12 degrees or so through the winter, that seems a better choice.

I found this page with an interesting video. It appears it is available from "Afloat" in Dunleary. I am thining it might be the best choice for me.

Tails142

The Delonghi I have is a dessicant type model - http://www.argos.ie/static/Product/partNumber/0523044/c_1/1%7Ccategory_root%7CHome+and+furniture%7C14417894/Trail/searchtext%3EDELONGHI.htm

Like I said, can probably find it cheaper somewhere other than Argos if you try. Like you've probably read they are more efficient and slightly heat the air which helps remove moisture.

MicktheMan

Piliger wrote: »

in my apartment where it is usually 12 degrees or so through the winter

:eek::eek:
so that's why you have mould on your walls!

Piliger

MicktheMan wrote: »

:eek::eek:
so that's why you have mould on your walls!

Yeah ... It's murder trying to stay warm with the tiny heater and two of the walls are outside and I am convinced they are not insulated.

Hugh_H

I wrote an essay about this for a thermodynamics project. Here's the google doc where I was saving my work
https://docs.google.com/a/ucdconnect.ie/document/d/1Je-qvxndKMKzYrHL6bJ0rKm-05qehls-kc7ktHDyeEY/edit
half of it is calculations which you'll probably want to gloss over. The key points are:
Using a dehumidifier requires less energy than using a tumble dryer but the tumble dryer uses so little to begin with you're only saving a few cents.
Having a small fan blowing over the clothes will reduce drying time significantly and a fan+dehumidifier will use less electricity than a dehumidifier alone but you'll need to turn the clothes around so that both sides get the fan blowing on them. Don't use a fan without a dehumidifier because the room will get too humid and drying will be slow.
Clothes will dry faster in a cold room than in a hot room because hot air holds less water vapour than cold air. Of course putting the clothes near the heat source will make them dry faster but I don't know if this will cost less.

Piliger

Hugh_H wrote: »

hot air holds less water vapour than cold air.

MicktheMan

Hugh_H wrote: »

Clothes will dry faster in a cold room than in a hot room because hot air holds less water vapour than cold air.

:eek::eek::eek:
Wrong. Plain wrong

The_Conductor

Piliger and MicktheMan- perhaps you might be interested in reading about the myths that you seem to have bought into....... A good first step would be the 'Bad Clouds' website- which attempts to debunk meteorology myths about clouds forming in cooler air- a theory which oddly enough seems to be pervasive.

MicktheMan

The_Conductor wrote: »

Piliger and MicktheMan- perhaps you might be interested in reading about the myths that you seem to have bought into....... A good first step would be the 'Bad Clouds' website- which attempts to debunk meteorology myths about clouds forming in cooler air- a theory which oddly enough seems to be pervasive.

Hugh is correct.

Hugh is not correct. He stated that "hot air holds less water vapour than cold air".

1. Air does not "hold" water vapour. Water vapour is a constituent of air. The amount of water vapour depends on the temperature of the air and the availability of moisture.

2. At a defined barometric pressure, warm air will contain more water vapour than cooler air, for example: air temp of 20 degC at its dewpoint will contain 17.3 g/m3 versus 9.4 g/m3 at 10 degC. This is fact, not myth.

Hugh_H

I said "hold" water because I am on boards.ie not physicsforums.com. It's easier for people to depict.

MicktheMan

Hugh_H wrote: »

I said "hold" water because I am on boards.ie not physicsforums.com. It's easier for people to depict.

Fair enough.
Can you explain your assertion that hot air contains less water vapour than cold air.

Hugh_H

Oh, my apologies. I looked over the calculations again and the rate of heat transfer is proportional to the difference between the vapour mass fraction just above the surface of the clothes and the vapour mass fraction in the surrounding air. Using this table http://www.tis-gdv.de/tis_e/misc/klima.htm I calculated the vapour mass fractions and it shows that the evaporation rate does increase if the temperature of the room and clothes is increased.
What I was getting mixed up with is that if you had the clothes and the room at 20 degrees then they would dry faster than having clothes at 20 degrees and the room at 30 degrees. This is because the higher air temperature would increase the partial pressure of the gaseous water in the air and decrease the tendency for water to evaporate.
I had it correct in the essay but it got mixed up in my head since I wrote that part a week ago.
I hope the essay was helpful for OP anyway.

Piliger

The_Conductor wrote: »

Piliger and MicktheMan- perhaps you might be interested in reading about the myths that you seem to have bought into....... A good first step would be the 'Bad Clouds' website- which attempts to debunk meteorology myths about clouds forming in cooler air- a theory which oddly enough seems to be pervasive.

Hugh is correct.

No he was wrong - and an honours degree in Chemistry (organic) + a degree in physics + analytical lab experience says so.

Piliger

Hugh_H wrote: »

I said "hold" water because I am on boards.ie not physicsforums.com. It's easier for people to depict.

And it is factually accurate.

Piliger

Hugh_H wrote: »

Oh, my apologies. I looked over the calculations again and the rate of heat transfer is proportional to the difference between the vapour mass fraction just above the surface of the clothes and the vapour mass fraction in the surrounding air.

Correct. Broadly speaking, the principle will be that heat is transferred faster when there is a larger temperature difference.

Using this table http://www.tis-gdv.de/tis_e/misc/klima.htm I calculated the vapour mass fractions and it shows that the evaporation rate does increase if the temperature of the room and clothes is increased.

Sort of, yes. See below.

What I was getting mixed up with is that if you had the clothes and the room at 20 degrees then they would dry faster than having clothes at 20 degrees and the room at 30 degrees. This is because the higher air temperature would increase the partial pressure of the gaseous water in the air and decrease the tendency for water to evaporate.

This is not true at all.

You have described two scenarios,

a) Clothes at 20C, Air at 20C
b) Clothes at 20C, Air at 30C.

If the pressure is the same in both, the air movement is the same in both, and the starting moisture content of the air is low in both, then there is no doubt whatsoever that the moisture will evaporate faster in the scenario with the higher air temperature.

It is straight forward physics. Not only will the warmer air have a higher capacity to absorb moisture than the cooler air, but the temperature differential will speed the heating of, and thus the evaporation at, the surface of the clothes, thus drying the clothes faster.

Either you mis-stated your post above, or your calculations are wrong.

FMartinp

What about the Dimplex Clothes Air Dryer that lies flat on the ground under a clothes horse and costs 0.1c per hour to run on electricity?

Zulu

Piliger wrote: »

..... and an honours degree in Chemistry (organic) + a degree in physics + analytical lab experience says so.

Ooohhhhhh well la-de-da.:rolleyes:

Hugh_H

Piliger wrote: »

No he was wrong - and an honours degree in Chemistry (organic) + a degree in physics + analytical lab experience says so.

I cannot hear degrees speaking to me, they don't say so. I'm interested in reasons you have why I'm wrong not your degrees. You sound arrogant by mentioning your degrees as if they give weight to your evidence. All you are doing is making those who don't know psychrometrics believe you, not because of what you have to say, but because of your qualifications. They will only guess you are correct because they can't review your evidence. Well you cannot convince me in such a way.
The vapour mass fraction which I'm calling z is equal to w/(1+w) where w is the absolute humidity in kg/m^3.
The vapour just above the surface of the clothes is pretty much 100% relative humidity and the ambient air is 50%.
For clothes at 20 degrees, using the table I gave a link to earlier, w=0.0173. z=0.0173/1.0173=0.01701
For air at 20 degrees. w=0.0087. z=0.00862
For air at 30 degrees. w=0.0152. z=0.01497

The rate of evaporation is proportional to the difference between vapour mass fractions.
At 20 degrees it's 0.01707-0.00862=0.00839
At 30 degrees it's 0.01707-0.01497=0.00204

The difference is larger at 20 degrees so the evaporation is faster.

I think where you misunderstood the scenario is that the clothes are constant at 20 degrees. This plays no role in real life evaporation which is why I didnt mention it in my "key points" earlier but it was a scenario of interest which I mentioned in the essay. You jumped in to criticize my findings without understanding what I was saying first.

Piliger

Hugh_H wrote: »

I cannot hear degrees speaking to me, they don't say so. I'm interested in reasons you have why I'm wrong not your degrees. You sound arrogant by mentioning your degrees as if they give weight to your evidence.

Oh yeaaah.... Education ???? what arrogance !!!!

What a hoot you are.

Zulu

Piliger wrote: »

Oh yeaaah.... Education ???? what arrogance !!!!

What a hoot you are.

You posted the academic equivalent of saying you score loads of sexy women/are a navy seal.

It was all a bit sad really.

The_Conductor

Ok- enough. If you want to take this elsewhere- we have a physics forum under the Science category- the Accommodation and Property Forum is not an appropriate venue.

Regards,

The_Conductor.