Tumble dryers revisited.

[T i m]

Hehe. I have the single version of that so I'm ready to go on the single TD 'Start' button. ;-)

Cheers, T i m

[T i m]

Interesting, thanks and bookmarked (for general projects etc).

Cheers, T i m

[ARW]

You'll be telling us next that you cannot get pregnant if you have sex whilst stood up.

[tabbypurr]

Incorrect. Unlike you I've experimented with clothes drying by fans.

NT

[T i m]

You don't live near a wind farm do you and are confused what they are? ;-)

So, when we dry clothes outdoors we absorb energy from the environment as the water evaporates. If we raise the airflow we also raise the rate of evaporation and so also lower the temperature of the clothes further (and how people make basic camping coolers with a rag and some water).

So, if you were to blow air though a (moving?) container of clothes, what would stop them cooling down to the point where they could freeze? Worse if you were recycling the air?

Given both of our de-humidifiers (working on the same principal of a liquid evaporating cooling a surface) often go into defrost mode if they are in an unheated room in the winter, what is to stop the clothes simply freezing up, if you don't introduce heat energy into the system to stop that?

I don't know the answers, I'm just asking the questions? ;-)

Cheers, T i m

[tabbypurr]

The faster the wind blows, the faster heat is transferred from ambient to t he water in the clothes. I've subjected clothes to some pretty strong winds and afaik they've not frozen. I suppose if they did they'd thaw again almo st instantly.

The same basic principle applies to evaporation, the faster the wind speed the faster the evaporation. Fans dry clothes with a small fraction of the e nergy use of heat. Whoever designs tumble dryers must be stuck in the 20th century, they're abysmally slow and inefficient compared to their potential . And they damage clothes more than necessary.

NT

[T i m]

Ok.

Ok.

So, for water to make the leap to vapour it must take energy from the environment to do so. If that environment is open and therefore potentially limitless then I could see that being the case. I'm not sure how it might fair in an enclosed world (especially if the air was trapped etc).

True ... but isn't that only true because it moves the water vapour away from the clothes and increase the supply of low level energy?

I wonder why they haven't made a wind turbine model though?

Would it have to be much bigger to get sufficient airflow ... and sound like a jet taking off?

I now a fan + de-humidifier make for a good low energy clothes dryer but the separation has to be done manually. Maybe you would need to try the concept in one of those skydiving machines first? ;-)

Cheers, T i m

[dennis]

You haven't pegged them out on a line in January when its 1C then. They freeze if its windy.

[T i m]

And of course at those thresholds it's a vicious circle. Increase the wind speed and whilst that increases the amount of low level energy to help the evaporation process, it also increases the evaporation process that increases the chill factor (latent heat of vaporisation) and in turn lowering the temperature in the water in the clothes.

So what we need is some way to heat some more heat energy into the clothes to keep the temperature up and make them dry faster, even when it's cold outside. ;-)

Cheers, T i m

[tabbypurr]

if you enclosed the air it would quickly saturate, and no further evaporation occurs

I'm not clear what that means, or what significant difference it makes what's happening at the microscopic level

maybe have never done the basic experiments to see how windspeed, tumble speed and heat all affect drying times, with wind speed going up to much higher than today's machines.

the machine no. the fan yes

large fans move lots of air without that noise

I've tried dehumidification with & without fans. Dehumidification does improve drying speed but not greatly, and the cost is pointless once you've got a fan.

NT

[tabbypurr]

I expect we've all done that. It's of no relevance though.

[tabbypurr]

High airspeed at 1C means any frosting will be thawed out rapidly. But no-one runs TDs at 1C afaik.

NT

[dennis]

No its just proof that what you said isn't true!

[tabbypurr]

oh dear

[Vir Campestris]

AFAIK they all leak humidity.

I'd design it with a closed cycle air system. They don't seem to do that

- they heat fresh air, then cool it again on the way out to extract some of the moisture. Not all of it.

Andy

[T i m]

I think our vented TD also leaks a little bit of humidity but most of that is probably because it's not pretty old and quite worn (felt seals etc).

Luckily, dealing with the potential issues of condenser dryers can now wait for a while as we got the old vented one going (again). ;-)

Cheers, T i m