Yes, that's correct. The head seen by the pump is a combination of static
head (the difference in height between the level of fluid on the suction
side and the level of the fluid on the delivery side) and dynamic head,
which is causied by the friction experienced by the fluid as it flows
through the block, hoses, radiator etc. In this case, static head is
negligible. Dynamic Head is proportional to the square of the flow rate.
The relationship between head and flow through a system is known as the
system curve. In theory, your calculated heads are correct if your
assumption for the initial head is correct. Actually, the dynamic head at
idle will be minimal - certainly measured in inches, I would think, rather
than feet. Remember, the system pressure can never rise above the pressure
rating of the radiator cap.
-----Original Message-----
From: Randall Young <randallyoung@earthlink.net>
To: 'Triumphs List' <triumphs@autox.team.net>
Date: Thursday, March 18, 1999 8:48 PM
Subject: RE: Electric Waterpumps
>
>Sorry !
>Forgot it's a closed system ! The height of the radiator has nothing to do
>with the head at the pump. Guess I'm getting too senile to think about new
>things <g>
>
>Randall
>
>On Thursday, March 18, 1999 4:05 PM, Randall Young
>[SMTP:randallyoung@earthlink.net] wrote:
>> Well, the rough approximation of a pint's a pound (the world 'round)
>seemed good enough for the precision required, and I DID assume a reduced
>head of 2 ft at 1250 rpm. This has to be about the minimum head, because
>of the height of the radiator.
>>
>> In fact, the head has to be roughly 2 ft at minimum rpm (500), so if it's
>proportional to the square of the speed, it already has to be 12.5 ft by
>1250 rpm, and 200 ft (over 80 psi) at 5000 rpm ! Somehow, I don't think
>the relation holds over this range <g>
>>
>> Several people have corrected my misunderstanding about the origins of
>this engine.
>> Thanks to all of you. However, does anyone know how much power it made
>in "Standard Vanguard" trim (ie as originally designed) ?
>>
>> Randall
>>
>> On Thursday, March 18, 1999 1:43 PM, Michael Marr [SMTP:mmarr@idcnet.com]
>wrote:
>> > 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.
>> >
>> >
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