Solar Space Heating Storage Tank Size [RE-wrenches]

[Travis Creswell, Ozark Solar]

Hello,

Assuming the internal heat exchanger is properly sized I don't understand
why you would want to stir the tank up.  Wouldn't the system work better by
taking advantage of stratification?  For example, you would have the hottest
water near the top ready for use.  If you stirred the tank up wouldn't you
risk not having hot enough water to be usable for space heating?  Sure there
might be more BTU's in the tank but your back up heat source would have to
bring the temp.

A drain back system would eliminate the need for the heat exchanger and, in
my experience, mixes the tank up.

I used flat plates when an external heat changer was the only option. They
simply put every other heat exchanger to shame in terms of efficiency.

Regards,
Travis Creswell
Ozark Energy Services, Inc.




-----Original Message-----
From: Dean T. Newberry [mailto:deant at dcn.org] 
Sent: Sunday, March 07, 2004 9:07 PM
To: RE-wrenches at topica.com
Subject: Re: Solar Space Heating Storage Tank Size [RE-wrenches]

Hi y'All
There are a couple of ways to transfer more energy from a heat exchanger 
in a tank.
The first is to move the water in the tank Grunfoss makes a  vertical 
axis special pump for this. Use a relay to slave it to circulation 
demand on the loop side of the heat exchanger, you only need to stir the 
tank when exchanging heat in or out. .
RBI sells replacement boiler pipes, copper fin tube in various sizes. 
The copper fin tube is what Heat Transfer Products uses in it's tanks to 
promote heat exchange.
I'll see if I can find the formulas for calculating the heat exchange 
given a delta T, heat exchange area and rate of flow on each side of the 
heat exchanger.
Since you are going to pump both sides of the heat exchanger it might be 
cheaper and easier to control with a flat plate heat exchanger.

cul  deant

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