Sensible and latent loads of clothes dryers

[turbA]

Hi all!

I am doing a preliminary design for a space containing a clothes dryer. Can anyone give me typical values for the latent and sensible heat given off by a dryer?

Thank you!

 

[tombmech]

It's trivial. The heating and moisture removal goes out the dryer vent. Typically, a dryer vent is a minimum code requirement anyway. The motor may add some waste heat to the space, but that's it. You could count some for exfiltration by opening and closing the door, but event that's negligible if you let it run to completion.

 

[MintJulep]

I disagree. The surface of a drier in operation gets warm. There must be sensible heat released into the space.

 

[IRstuff]

We don't run our dryer on hot days because the house gets hotter when we do.

TTFN

 

[TD2K]

The surface of my drier does get warm but not hot to the touch. Call it 100F. Call room temperature 70F. Call the drier 4' high by 3' wide by 3' wide. For four sides and the top, that's 45 ft2. Natural convection, allow 1 BTU/hr/ft2/F which is likely on the high side.

1350 BTU/hr as a rough guess. That's 0.4 kW and I suspect my numbers are on 'comfortably' on the high side.

I've got a Carrier design manual at home, will see if they provide any figures.

 

[imok2]

Clothes Drying
Based on four people with laundry
Natural Gas Clothes Dryer = 8 therms per month
or about 26,000 BTU/day

 

[tombmech]

TD2K has done the most reasonable estimate, except that the assumption of surface temperature may not apply to the four sides. In that case, since he already allowed that his estimate was "comfortably" on the high side, I submit that it's still trivial. Even if the case was several dryers concentrated in one spot, it may still be better to estimate the periodic opening/closing of the door. This was not that case, however - "dryer" was singular, not plural.

At something less than 400 Watts ("comfortable" allowance from TD2K's estimate), by the time you count the diversity (intermittent, infrequent operation), you really are at a trivial amount. In any event, the latent load is zero as well.

As for making the house noticeably warmer, some installations may have made mistakes - such as exposed duct runs or crawl space/basement/attic venting that can re-radiate back into the conditioned space. Or, in some cases, the dryer vent may dump onto the outdoor unit of the A/C system. Any of these may adversely affect space load.

The Carrier design books (several versions), ASHRAE Handbooks, and ASHRAE load manuals were checked before my first post. An estimate is not there - and is itself an indication of the load effect.

 

[CarolinaPE]

I tend to agree with tombech, particulary if the use is intermittent. If it was a laundromat then that would be different. Worst case I may give it an equipment load of 800-1000 btu. Most all is going out the vent. Heck people expect a room like that to get hot and will not spend much time there anyways!

 

[IRstuff]

Room? What room? it's in the middle of my downstairs hallway.

TTFN