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Subject:
Re: How to drain a tank of water at a constant rate?
From:
Chuck Howarth <[log in to unmask]>
Reply To:
Informal Science Education Network <[log in to unmask]>
Date:
Thu, 19 Aug 2010 09:22:52 -0700
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ISEN-ASTC-L is a service of the Association of Science-Technology Centers
Incorporated, a worldwide network of science museums and related institutions.
*****************************************************************************

So here's another idea:

Imagine your system as an hourglass, with two identical tanks connected by the 1" drain hole.  The whole system is closed, with air-filled expansion chambers top and bottom.  The two expansion chambers are connected by a hose.  

As water drains from top to bottom, pressure in the lower tank increases, and that pressure is then transmitted back to the top through the expansion chambers.  Net effect is that pressure is always constant at the top, so the flow rate should be as well.

I have no idea if that would actually work.....

On Aug 19, 2010, at 8:07 AM, Peter Ford wrote:

> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related institutions.
> *****************************************************************************
> 
> Hi all,
> 
> Here’s the technical dilemma that I’m trying to solve.
> 
> I want to drain a tank of water, from the bottom, at the same rate regardless of how much water is in the tank. So whether there is 5” or 20” of water in the tank it will drain at ½ gal a minute (values are somewhat arbitrary for this example).
> 
> So how can I do this? I’ve tested Pressure-Compensating Orifice from McMaster but that didn’t work (I think the pressure is to low for them to work). I have seen devices that automatically regulate but they are for larger industrial systems (and cost a lot), or they are for higher pressure systems.
> 
> For more specificity it’s a 11” diameter tank and I’m draining through a 1” valve. The water height varies between 4” to 30”
> 
> Any solutions, or ideas, would be appreciated.
> 
> Thank you in advance.
> -Peter
> 
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Chuck Howarth, Vice President
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For information about the Association of Science-Technology Centers and the Informal Science Education Network please visit www.astc.org.

Check out the latest case studies and reviews on ExhibitFiles at www.exhibitfiles.org.

The ISEN-ASTC-L email list is powered by LISTSERVR software from L-Soft. To learn more, visit
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