[Beowulf] Re: "hobbyists"

Robert G. Brown rgb at phy.duke.edu
Wed Jun 25 14:34:21 EDT 2008


On Wed, 25 Jun 2008, Kilian CAVALOTTI wrote:

> For washing machines the energy efficiency scale is calculated using a
> cotton cycle at 60°C (140°F) with a maximum declared load. This load is
> typically 6 kg. The energy efficiency index is in kW·h per kilogramme
> of washing.
> """
> http://en.wikipedia.org/wiki/European_Union_energy_label

Yeah, I saw your post.  Vincent left off the "hour" from kW-hours.  That
makes more sense.

>> If it IS heating water, then you need to be very careful.  It takes a
>> certain number of joules to heat water, period.
>
> Yes, but again, to produce that certain amount of heat, it may require
> more or less electric energy depending on the efficiency of the
> conversion. Although I assume most components probably do about the
> same, ball park. I would think efficiency is more a determinant factor
> in motors, for instance.

All energy conversion for heating water with electricity is joule
heating, almost certainly.  So it is one to one -- one joule of energy
as electricity to add one joule of heat to the water.  Efficiency
variation only associated with variations in e.g. insulation of the
reservoir.

The motors might have differential efficiency, but a factor of three is
a LOT.  That a suggests completely different process.

    rgb

>
> Cheers,
>

-- 
Robert G. Brown                            Phone(cell): 1-919-280-8443
Duke University Physics Dept, Box 90305
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Web: http://www.phy.duke.edu/~rgb
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