Actually, the fuel flow rate was .5 PINTS/BHP/Hr, not lbs/BHP/Hr. Thus,
under the conditions you have stated and using my initial assumptions, the
heat equivalent of 24 BHP would be about 61,100 BTUH. This would require a
cooling water mass flow rate of 51 lbs/min, or a volume flow rate of 6.1
gpm. HP consumed by the pump would be .027 BHP. At twice the speed, the
BHP would be .22 BHP and the flow rate would be 12.2 gpm, with a heat
rejection capacity of 122,000 BTUH, and at four times the speed the BHP
would be 1.75 BHP, flow rate 24.4 gpm and heat rejection capacity of 244,000
BTUH. HOWEVER, all this assumes that the TDH, which is determined by the
pressure drop across the system, stays constant, which it doesn't. In fact,
the pressure drop is dependent upon flow rate through the system and varies
as the square of the flow rate. So, as the speed doubles, power increase
eight times and pressure drop increases four times. This is why variable
speed pumping is used in large variable flow pumping applications in
industry - a 4,000 HP pump running at half capacity will only require 500 HP
if run at variable speed, whereas it will consume almost the full 4000 HP if
the flow rate is changed by throttling the flow with a valve. See, you
didn't know we had such a high-tech, energy efficient device on our cars,
did you?
BTW, the TR engine was originally a saloon car engine that just happened to
be applied to a Fergusson tractor back in the late forties - it was never
developed from the tractor engine.
-----Original Message-----
From: Randall Young <randallyoung@earthlink.net>
To: 'Michael Marr' <mmarr@idcnet.com>; Triumphs List
<triumphs@autox.team.net>
Date: Thursday, March 18, 1999 12:44 PM
Subject: RE: Electric Waterpumps
>So, another way to look at this is :
>
>>From the same factory chart, full power at 1250 rpm is about 24hp = about
>12 lb/hr fuel.
>If 1/3 of the input heats the water, then using your equation, with a 2 ft
>head and 20 deg rise gives us .0067 hp for the pump.
>Then, using the cube law, a 4 times increase in pump speed takes a 64 times
>increase in power, for .43 hp at 5000 rpm. 7000 rpm takes 175 times as
>much, or over 1 hp.
>
>Still not a lot, but noticeably higher.
>
>Of course, for any of this have any meaning, we have to assume that someone
>actually engineered the water pump, instead of just building something and
>finding that it worked "good enuf". Considering that the 4cyl TR engine
>was originally a tractor engine that produced maybe 45hp at the flywheel,
>and AFAIK the water pump is still the same, I'm not sure that's a good
>assumption <g>
>
>Randall
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