[Greenbuilding] A solar air heater with a Scandinavian breathingwall deep mesh

[Douglas E Lamb]

Thx, for the insights.
It's going to take a few days to rummage through the masses of information
you've so generously assembled on you site.
It had to take some years to developed you data base.
Great work by-the-way.
 
Regards,
Doug Lamb
614.323.2005
douglaslamb at columbus.rr.com
 
 

  _____  

From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of nick
pine
Sent: Monday, January 23, 2012 4:12 PM
To: greenbuilding at lists.bioenergylists.org
Subject: [Greenbuilding] A solar air heater with a Scandinavian
breathingwall deep mesh



Deep Mesh Solar Air Heating Collector -- Test 1

 

Nick Pine proposes a solar home heating concept using solar heating system
that is aimed at producing a very high solar fraction with relatively
inexpensive solar air heating collectors. In order to accomplish the high
solar fraction, the system must include several days worth of heat storage
for extended cloudy periods -- a large storage capacity.

The physical size of this large heat storage depends on the maximum
temperature that the storage can be raised to -- higher temperatures store
more heat in less space. But, producing higher temperatures normally means
that the solar air heating collectors would operate less efficiently as the
losses out the collector glazing go up with collector temperature -- thus
the desire for high storage temperatures can result in an undesirable
increase in collector area.

There is a potential collector design that may produce the desirable higher
collector temperatures at good efficiency. This design uses several layers
of mesh for the absorber. The advantages are said to be: 1) the pressure
drop caused by the mesh spreads the airflow evenly over the full surface of
the absorber, and 2) the first layer of mesh acts as a radiation shield to
reduce the radiation from the hotter inner layers toward the glazing. The
first layer of mesh runs relatively cool in part because in this heating
scheme, the air introduced into the collector is relatively cool (70F) room
air -- this cooler first layer of mesh thus reduces losses out the glazing.

So, in an ideal design, 70 F room temperature air is introduced between the
glazing and the first (south most) layer of mesh. This coolish air spreads
evenly over the full mesh surface because of the mesh pressure drop. Even
though the airflow rate is low (to achieve higher temperatures), the first
layer of mesh runs at a low temperature because of the relatively cool 70F
air, and the ability of the mesh absorbers to provide very even airflow over
the full surface. As the air progresses through the layers of mesh, it heats
up, and since flow rate is low, the residence time is long and the air heats
up to high temperatures (say 140+F). This hot air is then passed through an
air to water heat exchanger and the hot water produced goes to heating the
heat storage. By using the hottest air to heat the storage, the max storage
temperature can be higher and it can store more heat. The still warm air
leaves the heat exchanger and is blown into the house for immediate space
heating. 

A key element in making this scheme work is the low flow, deep mesh
collector that operates efficiently while producing high temperatures. This
test is a starting point in trying to see if this can be accomplished in a
collector that is straight forward and inexpensive to build. My standard air
heating collector which has just 3 layers of aluminum screen mesh is the
starting point. The idea is to see how well it does in achieving the high
temperatures AND high efficiency, and to identify changes that might make it
do better, and possibly test those.

On this page: 


-  <http://www.builditsolar.com/Experimental/DeepMeshCol/#Collector>
Collector Description 


-  <http://www.builditsolar.com/Experimental/DeepMeshCol/#Setup> Test Setup 


-  <http://www.builditsolar.com/Experimental/DeepMeshCol/#Results> Results
(temperatures, flow rates, heat out, efficiency, glazing temperature) 


-  <http://www.builditsolar.com/Experimental/DeepMeshCol/#Where> Where to go
from here? 


-  <http://www.builditsolar.com/Experimental/DeepMeshCol/#Details> More
detail in some areas 


-  <http://www.builditsolar.com/Experimental/DeepMeshCol/#Puzzle> A glazing
temperature puzzle 


First  <http://www.builditsolar.com/Experimental/DeepMeshCol/Nick01.htm>
comments from Nick on this test...


http://www.builditsolar.com/Experimental/DeepMeshCol/120116Test.htm
 
Nick
 
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