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Re: Chilling truth
- To: Aquatic-Plants at actwin_com
- Subject: Re: Chilling truth
- From: Paul Sears <psears at nrn1_NRCan.gc.ca>
- Date: Tue, 10 Jun 2003 14:45:24 -0400 (EDT)
- In-reply-to: <200306101056.h5AAu8Gr019632@otter.actwin.com> from "Aquatic Plants Digest" at Jun 10, 2003 06:56:08 AM
What a mess! Let's start from square one and get away from
the obsolete units that caused the problem in the first place.
1 "ton" of chilling is 3.5 kW of chilling.
1 watt (W) is one Joule per second
1 BTU is 1055 Joules
1 horsepower is 746 W
1 boiler horse power is an even more obsolete unit and was in effect
the amount of heat applied to the boiler so that an engine could provide
1 horsepower. Since boilers and engines had different efficiencies,
this could lead to problems. I'm not touching that one again.
A mechanical chiller works by moving heat from a low temperature
to a higher temperature. The work applied by the motor appears as
heat in the heat output. A chiller with a COP (coefficient of
performance) of 3 will use 1 unit of mechanical energy to remove
3 units of heat energy from the place to be chilled and will produce
3+1=4 units of heat energy at the place where heat is dumped.
COP's depend heavily on the actual system and the temperatures
involved, but 3 to 4 is typical. Note that COP is dimesionless.
Convert everything to watts, and it's easy.
Chiller efficiencies are sometimes reported as "SEER" instead
of COP. The SEER is a ratio of heat removal in BTU/h to mechanical power in
watts. Divide the SEER by (3600/1055 = 3.412) to get the COP.
Why are we using nineteenth century units in the twenty-first
psears at nrn1_nrcan.gc.ca, 613-996-4171, facsimile / télécopieur 613-996-9400
Natural Resources Canada, 1, Haanel Drive, Nepean, Ontario K1A 1M1
Ressources naturelles Canada, 1, Haanel Drive, Nepean, Ontario K1A 1M1
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