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Thermal mass for large thermosyphon solar air heater

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Posted by David Delaney on November 14, 2003, 7:16 pm
 
I have just published (on my web site) two new
documents on the design of a thermal mass for a
large thermosyphon air heater.  URLs, titles, and
first paragraphs appear below.

I would welcome comments.

David Delaney, Ottawa

First document:

http://geocities.com/davidmdelaney/thermal-mass/concrete-block-thermal-mass.html

Title: A concrete-block thermal mass with large
air-concrete surface area David Delaney Ottawa,
November 14, 2003.

First paragraph:

I spent some time with a CAD program searching for
a suitable design for a thermal mass constructed
from common concrete building blocks. The thermal
mass needed to be highly permeable to air flow
vertically and horizontally in any north-south
vertical plane, and needed to have a large
air-concrete surface area per block.  This note
presents the best tradeoff I could find between
permeability, a large air-concrete surface area,
and stability.  The block stack described here has
an average air-concrete surface area of 3.48 ft2
per 8"x8"x16" concrete block. I found one stacking
method that produced 4.5 ft2 per block, but it
looked too unstable.

End of first paragraph.

Second document:

http://geocities.com/davidmdelaney/thermal-mass/two-part-heat-store.html

Title: An economical heat store with large thermal
mass, low resistance to air flow, and large
heat-transfer surface area. David Delaney November
14, 2003

First paragraph:

This article describes a heat store designed to
collect energy from a solar air heater. The air
heater is to be located below the heat store, and
is to supply warm air to it by natural convection.
The intended general arrangement of the solar air
heater and the heat store are described in
reference [2]. The heat store requires a large
thermal mass, a large mass-air surface area for
heat transfer, and low resistance to air flow. I
propose a heat store having two constituent
heat-storing masses. One of the constituents, a
very permeable stack of concrete building blocks,
has a large concrete-air heat-transfer surface
area and a small thermal mass. The other
constituent, a stack of drums of water, has a
large thermal mass and a small drum-air
heat-transfer surface area. Both constituents
share a single insulation envelope and operate
within a single unpartitioned volume of air.  For
carefully chosen circumstances, the performance of
the two-component heat store should be similar to
the performance of a heat store having the sum of
the surface areas and the sum of the thermal
masses of the two constituent heat storing masses.
This composite concrete-water heat store requires
much less mass and space than a heat store
constructed from either concrete or water alone.

End of first paragraph.

Posted by Slow Joe on November 15, 2003, 5:18 am
 
One of the problems with concrete blocks is the dust they produce.
Each block should probably be dipped in some kind of surface sealant
to prevent the release of concrete dust, if you plan on circulating
air from your heater space into your living or working space.

regards,
Joe

----------------
It matters not how experienced you are, nor how dedicated to the task. If you're
not having fun, you are doing it wrong.

Posted by David Delaney on November 15, 2003, 5:40 am
 On Sat, 15 Nov 2003 05:18:20 GMT,
pokeeejoe@yahoo.com (Slow Joe) wrote:


Will the dust matter when all air movement over
and through the blocks is by natural convection?
Will the air not move too slowly to pick up the
dust?

Do you have any particular surface sealants in
mind?

David Delaney, Ottawa

Posted by Slow Joe on November 15, 2003, 2:22 pm
 On Sat, 15 Nov 2003 00:40:24 -0500, David Delaney


Any air movement at all, will carry dust.

No. I never looked into concrete surface sealants for high temperature
use.

regards,
Joe

----------------
It matters not how experienced you are, nor how dedicated to the task. If you're
not having fun, you are doing it wrong.

Posted by daestrom on November 15, 2003, 7:09 pm
 

Perhaps simple latex paint would do the trick?  Certainly cheap and safe for
home use.

daestrom



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