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From: "William" <wschertz@ispwest.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-814866@logan.com>
Subject: Re: [FlyRotary] EWP: How much is enough
Date: Mon, 21 Mar 2005 21:30:04 -0600
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I know that calculations are frowned upon by some, but the relationship 
between flow rate and delta-T is not rocket science to calculate very 
accurately.

Q = m*Cp*deltaT

Q is the amount of heat needed to be transferred,
m is the mass flow rate
Cp is the heat capacity at the temperature of operation of the fluid
deltaT is the temperature rise/drop across the engine/radiator

The greater the deltaT across the engine/radiator, the *lower* the average 
temperature of the water in the radiator. This is important because in our 
application, the most difficult part is getting the heat out of the radiator 
into the air stream. We would like the greatest temperature difference 
between the water and the air -- if the water going into the radiator is 
200F, and exits the radiator at 170F, we have an approximate driving force 
of 185F - (temp of air).  On the other hand, if we go in at 200F and have a 
60F drop (1/2 the flow rate) then the approximate driving forces is only 
170F - (temp of air).

With the smaller driving force, you need more area, or more air, or colder 
air.

Bill Schertz
KIS Cruiser # 4045

> Graphing the results should tell us what flow will give what deltaT.
>