[USMA:27065] Re: Air conditioners

[CarletonM]

In a message dated 2003-09-27 12:53:09 Eastern Daylight Time, [EMAIL PROTECTED] writes: On Tue, 23 Sep 2003, john mercer wrote: > Could someone please tell me what the SI unit is for measureing the output > of airconditioners? The most revealing measurement is "Coefficient of Performance (COP)" which is defined as the time rate of heat energy removed divided by the time rate of electrical energy input to operate the compressor, blower, and controls. Since both time rates are power (watts (W) in SI), the COP ratio is in units of W/W which makes COP a "unitless" number. Prof Eugene (Gene) Mechtly, College of Engineering University of Illinois at Urbana-Champaign I had to buy a generator last week because of Hurricane Isabel and its power failures.   Believe it or not, there were a few to choose from.  I wanted the most efficient one.  The clerk at Home Depot was clueless.   I told him, "This is easy, just quit using your archaic unit called 'horsepower'.  A horsepower is actually defined as 746 watts.  So this generator has a 10 'horsepower' engine.  This is atually 7460 watts.  The electrical output is 6250 watts.  So it's about 85% efficient.  The little one over here has a 3 'horsepower' motor and only puts out 1000 watts -- less than 50% efficient."   The only reason we are stuck with horsepower is the same reason the Canadians are stuck with pounds in the grocery.  A horsepower seems bigger than 0.746 KW, and a pound seems cheaper than a kg:  the uneducated are made happy.   Carleton