Note: Descriptions are shown in the official language in which they were submitted.
A METHOD FOR PRE~EATING VENTILATION AIR IN A BUILDING
This invention relates generally to a method of
controlling the entry of ventilation air to a building,
and preheating the air with a combination of solar heat
and the natural building heat loss.
BACKGROUND OF THIS JNVENTION
Commercial and industrial buildings require
ventilation, and it is common for the natural leakage
around doors, wall-ceiling joints, etc. found in standard
building construction to allow sufficient ventilation air
to enter the building. A pressure drop from the exterior
to the interior of the building can arise from many
factors, such as high winds, exhaust fans and combustion
air for fuel-burning furnaces. This tends to draw
outside air into the building through any crack or
opening.
The problem with the conventional approach is
that the amount of ventilation air is not controlled, and
additional heat must be provided to heat the outside air
20 to room temperature during the fall, winter and spring
months.
This problem has typically been solved by
installing air make-up fans with gas or electric heaters
to heat the incoming air. When solar panels are used to
25 heat a building, air is re-circulated from the building
through the panels and then back again to the building.
The efficiency of a solar collector is maximized when the
temperature of the air entering the collector is the same
as the ambient temperature. Under normal winter
30 conditions, the ambient temperature is lower than the
room temperature, and therefore a recirculating ~olar
collector operates at a much reduced efficienc~ level in
wintertime.
GENER~L DESCRIPTION OF THIS INVENTION
. . .
In accordance with this invention, instead of
using consumable energy sources like gas or electricity
to heat incoming air, and instead of simply recirculating
interior air from the building through a solar collector
and back to the building, fresh make-up air for
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ventilation purposes is in-troduced into the interior of
-the building after first passing through a solar collector
located on a south-facing wall of the building. The solar
collector can be either a commercially built solar collector,
or a site-built collector consisting of glazing over a
darkened wall. The air thus travels through the air space
defined in ~he collector and enters the building through
a duct system within the interior.
More specifically, this invention provides a
method of preheating ventilation air for a building, com-
prising the steps:
a) providing a vertical, air-heating solar
collector surface on a south facing wall of the building,
in such a way that heat being lost from the interior through
the south-facing wall is available at said surface and
can contribu-te heat to air passing through the solar collector
panel means,
b) providing glazing spaced outward from said
surface,
c) passing outside air through the solar collector
panel means in a generally vertical direction from a lower
inlet, the air passing between said surface and said glazing,
and heating the air with a combination of solar heat and
the heat being lost from the interior through the south-facing
wall, and
d) withdrawing the heated air from the solar
collector panel means at a location near the top thereof
and using air-moving means to expel the heated air into
the interior of the building.
~dditionally, this invention provides apparatus
for preheating ventilation air for a buildin~, comprising:
air-heat.ing solar collector means provided on a south-facing
wall of the building, the solar collector means including
a blackened surface in heat-transfer contact with said
wall, and glazing means spaced from said blackened surface,
an air inlet along the lower edge of said solar collector
means, and an air exit adjacent the top thereof, air-moving
means and duct means arranged to allow heated air to be
withdrawn from the collector means and expelled into the
2a
interior of the building, the air exit communicating with
said air-movlng means.
GENERAL DESCRIPTION OF THE DRAWING
In the drawings:
Figure 1 is a perspective view of a make-up or
ventilation air system for a building, constructed in
accordance with this invention' and
Figure 2 is a graph of a typical collector efficiency
- curve.
DETAILED DESCRIPTION OF THE DRAWING
Attention is now directed to Figure 1, which
shows a partly broken-away perspective view of a system
for performing the present invention. A building wall is
shown in part at 10 in the figure, this being typically a
block construction, or a block-and-brick composite
structure. As with all building walls, even those
well-insulated, a steady heat loss is experienced through
the wall when the outside temperature is below the inside
10 temperature.
The numeral 12 designa-tes a portion of the wall
10 which has been blackened by the application of paint
or other suitable solar-collective coating, rendering the
portion 12 of the wall 10 highly absorptive in the
visible and infra-red region of the spectrum. A
plurality of glazing panels 14, which may be of glass,
plastic or other suitable transparent material, is
located in spaced relation outwardly from the blackened
portion 12 to define a plurality of air passageways 16
between each g]azing panel 14 and the wall 10, the
passageways 16 being separated by partitions 18 (one
being visible in the Figure) which act to support the
glazing panels 14 along their ver-tical edges. The
specific support structure between the partitions 18 and
the glazing panels 14 does not form a part o~ this
invention, and need not be described in detail. The
important point is that the passageways 16 have an access
at the bottom to allow entry of outside air. If desired,
a screen 19 may be provided at the bottom of passageways
16, to prevent entry by birds, insects and the like.
At the top, the passageways 16 defined between
the panels 14 and the wall 10 communicate with the
interior of a hood unit 20 which is triangular in section
and includes a sloping upper wall 22 and a substantially
horizontal bottom wall 23. The bottom wall 23 extends
from the outer edge 25 of the upper wall 22 to the upper
edges o~ the panels 14. Inwardly, the hood unit is
secured in air-tight manner against the wall 10 above the
blackened portion 12 thereof, and has flanges 27 for this
i8~S
purpose. Alternatively, the hood unit 20 could include a
vertical inner wall to be placed directly against the
wall 10 of the building. End walls 28, of which one is
seen in the figure, complete the hood unit 20 and allow
it to define a substantially air-tight chamber into which
air from the passageways 16 empties.
Communicating with the internal chamber in the
hood unit 20 is a fan housing 30 which contains a
conventional fan or air-impeller (not visible) and
includes motorized dampers 32 which allow air from the
interior of the building to be mixed with heated air
coming from the hood unit 20.
Communicating with the housing 30 is a fabric
air duct 34 which is preferably flame retardant and made
Of polyfabric, the duct 34 being suspended by a plurality
of duct hangers 36 from a suitably strung support wire or
rod 38. The air duct 34 has a plurality of openings 40
through which the heated outside air can pass from the
duct 34 into the interior of the building. By
appropriately sizing the openings 40, the air can enter
the interior of the building as a high-velocity air jet,
thus promoting good mixing within the interior of the
building, and minimizing stratification.
It will be understood that, by placing
blackening material on the portion 12 of the wall lO,
i.e. directly in contact with the wall 10, the outside
air moving upwardly along the passageways 16 will derive
heat not only from the sun's energy, but also from the
heat being lost from the interior of the building through
the wall 10. This, however, would be the case with any
design of solar collector, so long as the wall lO were in
heat communication with the collector portion of the
solar collector.
It is preferred that the duct 34 be located at
ceiling le~rel within the building, for the sake of
convenience, however other levels could also be utilized.
The fan within the housing 30 would typically be sized to
meet the ventilation requirements and eliminate the
negative pressure problem if such exists. ~ positive
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pressure can be achieved with outside air entering the
building through the fan in the housing 30, the air being
heated by the solar heat, the building heat loss, and
stratified heat found near the ceiling. Air can then
leave the building through the cracks and openings where
previously air had entered.
It will be noted that the hood unit 20
overhangs the panels 14, and thus a shadow is cast upon
the panels 1~ during late spring and early summer, when
the sun at mid-day is quite high in the sky. This
automatically avoids solar heating of the air during the
hotter portion of the year. In any event, with the sun
being located high in the sky, and the panels 14
vertical, only a small portion of the sun's radiation
would enter the solar collector, even if it could fall
upon the panels 14.
Referring to Figure 2, it can be seen that a
typical solar collector operates near or at maximum
efficiency when the fluid (air) inlet temperature equals
the ambient temperature. In a typical solar heating
installation, internal air is recirculated, and assuming
that the space temperature is 20C while the outside
temperature is -10C, there is a difference of 30C. The
maximum solar insolation in round numbers is
approximately 1000 watts per square meter. The situation
just deEined would give .03 on the X scale which, in the
case of this collector curve , would yeild an efficiency
of 32~. In the present invention, on the contrary, in
which the inlet temperature and the ambient temperature
are the same, the X scale position is 0, resulting in the
maximum efficiency oE 55~.
While one embodiment of this invention has been
illustratecl in the accompanying drawing and described
hereinabove, those skilled in the art will appreciate
that changes and modifications may be made therein
without departing from the essence of the invention as
set forth in the appended claims.
