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Re: [Amps] 8877 blower requirement ?

To: amps@contesting.com
Subject: Re: [Amps] 8877 blower requirement ?
From: Steve Thompson <g8gsq@eltac.co.uk>
Date: Fri, 06 Apr 2007 17:09:16 +0100
List-post: <mailto:amps@contesting.com>
>>> http://www.g8wrb.org/data/Eimac/3CX1500A7.pdf
>> As well as a data sheet with airflow figures, you can also find an
>> article describing how to estimate what flow/pressure a blower will
>> produce. In general, CFM ratings are not a useful guide - you need to
>> know if a blower will produce enough pressure.
>  Umm, beg to differ. What actually provides the heat transfer is the 
> mass  flow rate of air (grams per second) and its specific heat. 
> Unfortunately  the mass flow rate of a gas is very difficult to measure.

I don't think we differ. What I meant was that blower cfm ratings
alone are not a useful guide to suitability for a given valve. First
you have to establish if the blower can produce the pressure - then
you can see if there's enough volume/mass flow. Blower cfm ratings are
nearly always into free air, which tells you nothing about the 'load
line'. I have a lovely snail blower with a fancy cast housing and so
on. From memory it's rated at close on 300cfm - but feed it through an
8877 and you're hard pushed to feel any air flow coming out.

Steve

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