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Re: NFC: [Fwd: Peltier Junctions]
----- Original Message -----
From: Wright Huntley <huntley1 at home_com>
To: <nfc at actwin_com>
Sent: Monday, July 26, 1999 6:41 PM
Subject: Re: NFC: [Fwd: Peltier Junctions]
> > Andrew Dalton wrote:
> > > Based on the information at the Melcor web site, the Peltier junctions
> > > consume about 1.7 watts of electricity (I*V) for every 1 watt of heat
> > > transferred. So the power consumption required for this application
> > > 64*1.7 = 109 W. This will probably require a heat sink and fan on the
> > > hot side of the Peltier junction.
> Something like that is needed on *both* sides. Coupling to the water must
> made that allows low enough temperature difference and enough heat flow to
> get the heat *to* the cold side of the junction.
Correct, but heat transfer on the cold side is easier for a couple of
reasons. First, the hot side has to dissipate 173 watts (for clarification,
see my response to myself), while the cold side has to absorb only 64 watts.
Second, the heat transfer coefficient* on the water side is typically much
greater than the heat transfer coefficient on the air side. A good example
of this is a contrast between a person standing in 40 deg F air vs. swimming
in 40 deg F water.
*This is the liquid-side heat transfer coefficient, and it should not be
confused with the overall heat transfer coefficient that I used in
calculating the heat loss from the aquarium.