venting a dryer indoors SOLAR.KnowledgePublications.com

venting a dryer indoors
19 nov 1996
>>>>maybe you can vent the dryer inside, or put a clothesline in your new
>>>>sunspace above the porch.
>>> 
>>>actually, i have done that.  i have the dryer hose capped off with an old
>>>nylon that i clean out every 3 or 4 loads.  the heat and moisture discharge
>>>right into the house.

>>if you make your house a lot tighter, you may want to try to condense
>>the moisture output of the dryer, instead of letting the vapor loose
>>in the house. 
 
>the moisture is already a problem.  if i made a plexiglass box with a
>slanted top, attached the hose to the lower side, and had the air discharge
>under the point of entry, would that take most of the moisture out?
 
>                    /                    |
>                  /                      |
>                /                        |
>              /   shallow angle          |
>            /      15-20 deg.            |
>          /                              |
>        /                                |
>      /                                  |
> 1  -|                                   |
> --> |                                   |
>    -|                                   |
>     |                                   |
>  2 -|                                   |
> <-- |                                   |
>    -|                                   |
>     |                 3                 |
>     |-----------------------------------|    
 
>   1 is dryer air going in (moisture)
>   2 is exhaust from unit, hopefully dryer than 1
>   3 pool of water dripping off of angled top
 
>is this a good idea, or will it not work?

not a bad idea in principle, but why the slanted top? it looks like a solar
still with no sun :-) could you use a long and large diameter exhaust hose or
pvc drainpipe ($4 for a 4" diameter 10' length) running around the basement
ceiling instead, with a continuous downslope towards a bucket below the end,
inside the house? the heat transfer area needs to be large enough to reduce
the temperature of the airstream to less than 212 f, so the water vapor will
condense. water will drip from the end of the pipe when it's working correctly.
a 4.5 kw electric dryer makes about 15k btu/hr of heat, enough to evaporate
15 pounds (2 gallons) of water per hour or to completely heat a well-insulated
house. disgusting. why not use a clothesline, or vent the dryer inside a
sunspace, and let the moisture collect and run down the glazing and onto the
ground? or try harder to recover that heat for the house in the winter. is
bombing iraq to keep the price of heating oil low a simpler solution?

as i recall, swedish asko dryers vent inside the house and condense water
vapor from damp clothing into a cup. the clothes start out dryer than most,
after a faster than normal spin cycle in asko washing machines. 

cooling 4.5 kw dryer air to 212 f in a 68 f room requires a heat conductor with
area a and air film surface resistance r such that (212-68)a/r = 15000 btu/hr,
ie 144a/r = 15k or a = 104r. if r = 2/3 (still air), a = 70 ft^2, eg 3 55
gallon drums in series. or 70' of 4" diameter black plastic spiral drainhose.
moving air past the pipe at 6 mph decreases the surface air film r-value to
about r0.2, so a might be 20' of 4" pvc drainpipe or 6" poly film duct inside
20' of 10" poly film duct (unpunched v4-10 convection tubing at $0.29/linear
foot from d & l grower supplies at (800) 732-3509) with a 500 cfm fan at one
end (eg grainger's $60 560 cfm 36 watt 4c688 fan), perhaps in series with
grainger's $6.46 2e250 160 f cooling thermostat near the tube output.

nick

nicholson l. pine                      system design and consulting
pine associates, ltd.                                (610) 489-0545 
821 collegeville road                           fax: (610) 489-7057
collegeville, pa 19426                     email: nick@ece.vill.edu

computer simulation and modeling. high performance, low cost, solar heating and
cogeneration system design. bsee, msee. senior member, ieee. registered us
patent agent. solar closet paper: http://leia.ursinus.edu/~physics/solar.html
web site: http://www.ece.vill.edu/~nick