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Claims  |
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We claim:
1. A solar heating panel comprising:
a. a base member formed from an insulating material, said member having
i. a liquid impervious upper surface,
ii. a plurality of spaced apart fluid supply recesses formed in said upper
surface and extending longitudinally therealong,
iii. inlet and outlet manifolds, each manifold extending transversely
across one of the ends of said base member and each manifold being
disposed in fluid communication with each of said recesses,
iv. an inlet port disposed in fluid communication with said inlet manifold,
v. an outlet port disposed in fluid communication with said outlet
manifold,
vi. a fluid return recess formed in the upper surface of said base member
along one side thereof, said fluid return recess being adapted to be
placed in fluid communication with said outlet port, and
vii. a plurality of spaced apart strips formed on the upper surface of said
base member, said strips being disposed intermediate each of said recesses
and adjacent the outer side of the outwardly disposed recesses;
b. a rigid solar heat absorbing member formed from metal and mounted upon
the upper surface of said base member in contacting engagement with each
of said strips,
i. the upper surface of said solar heat absorbing member containing a
black, solar radiation absorbing coating thereon,
ii. said solar heat absorbing member cooperating with said recesses to form
liquid supply channels and a liquid return channel each of which is
isolated one from the other,
iii. each liquid supply channel having a width to depth ratio varying
between approximately 9 and 13.5, and
iv. each liquid supply channel having a mean hydraulic radius varying
between approximately 0.018 and 0.023;
c. an inverted cup shaped member formed from a transparent material and
secured to said base member, said cup shaped member having an upper,
generally planar surface spaced apart from the upper surface of said solar
heat absorbing member, said inverted cup shaped member permitting solar
radiation to pass therethrough and impinge upon said solar heat absorbing
member for all angles of solar radiation impingement from a direction
normal to the upper surface of said solar heat absorbing member plus or
minus less than 90 degrees; and
d. an elastic adhesive means for securing said solar heat absorbing member
to said strips, said adhesive means having flat bonding characteristics
over the environmental temperature range whereby thermal expansion of said
base member relative to thermal expansion of said solar heat absorbing
member occurs while maintaining a general planarity of the upper surface
of said solar heat absorbing member.
2. A solar heating panel as described in claim 1 in which the width to
depth ratio of each liquid supply channel is equal to approximately 10.
3. A solar heating panel as described in claim 1 in which the mean
hydraulic radius of each liquid supply channel is equal to approximately
0.023.
4. A solar heating panel as described in claim 1 including a layer of
transparent material disposed intermediate said upper surface of said
inverted cup member and said upper surface of said solar heat absorbing
member and spaced apart therefrom.
5. A solar heating panel as described in claim 1 in which the upper surface
of said inverted cup shaped member comprises a segment of a generally
spherically shaped surface having a chord to radius ratio of not more than
approximately 0.19.
6. A solar heating panel as described in claim 1 in which each strip
includes means for supporting said solar heat absorbing member in spaced
apart relation above a major portion of the plan surface area of each said
strip.
7. A solar heating panel as described in claim 6 in which each strip is, in
cross-section, generally of an inverted V-shaped configuration.
8. A solar heating panel as described in claim 6 in which each strip
includes boss means formed thereon for supporting said solar heat
absorbing member in spaced apart relation above approximately 85% of the
plan surface area of each said strip by an amount equal to approximately
20% of the depth of said fluid supply recesses.
9. A solar heating panel comprising:
a. a base member formed from an insulating material, said member having
i. a liquid impervious upper surface,
ii. a plurality of spaced apart fluid supply recesses formed in said upper
surface and extending longitudinally therealong,
iii. inlet and outlet manifolds, each manifold extending transversely
across one of the ends of said base member and each manifold being
disposed in fluid communication with each of said recesses,
iv. an inlet port disposed in fluid communication with said inlet manifold,
v. an outlet port disposed in fluid communication with said outlet
manifold, and
vi. a plurality of spaced apart strips formed on the upper surface of said
base member, said strips being disposed intermediate each of said recesses
and adjacent the outer side of the outwardly disposed recesses;
b. a rigid solar heat absorbing member formed from metal and mounted upon
the upper surface of said base member in contacting engagement with each
of said strips,
i. the upper surface of said solar heat absorbing member containing a
black, solar radiation absorbing coating thereon,
ii. said solar heating absorbing member cooperating with said recesses to
form liquid supply channels each of which is isolated one from the other,
iii. each liquid supply channel having a width to depth ratio varying
between approximately 6.5 to 15.0, and
iv. each liquid supply channel having a mean hydraulic radius varying
between approximately 0.018 and 0.027;
c. an inverted cup shaped member formed from a transparent material and
secured to said base member, said cup shaped member having an upper
generally planar surface spaced apart from the upper surface of said solar
heat absorbing member, said inverted cup shaped member permitting solar
radiation to pass therethrough and impinge upon said solar heat absorbing
member for all angles of solar radiation impingement from a direction
normal to the upper surface of said solar heat absorbing member plus or
minus less than 90.degree.;
d. an elastic adhesive means for securing said solar heat absorbing member
to said strips, said adhesive means having flat bonding characteristics
over the environmental temperature range whereby thermal expansion of said
base member relative to thermal expansion of said solar heat absorbing
member occurs while maintaining a generally planarity of the upper surface
of said solar heat absorbing member; and
e. said base member including a fluid return recess formed in the upper
surface along one side thereof, said fluid return recess being adapted to
be placed in fluid communication with said outlet port, and said solar
heat absorbing member cooperating with said fluid return recess to form a
liquid return channel that is isolated from the liquid supply channels.
10. A solar heating panel comprising:
a. a base member having
i. a liquid impervious upper surface,
ii. a plurality of spaced apart fluid supply recesses formed in said upper
surface and extending longitudinally therealong,
iii. inlet and outlet manifolds, each manifold extending transversely
across one of the ends of said base member and each manifold being
disposed in fluid communication with each of said recesses,
iv. an inlet port disposed in fluid communication with said inlet manifold,
v. an outlet port disposed in fluid communication with said outlet
manifold,
vi. a fluid return along a portion of the base member, said fluid return
being adapted to be placed in fluid communication with said outlet port,
vii. a plurality of spaced apart strips formed on the upper surface of said
base member, said strips being disposed intermediate each of said recesses
and adjacent the outer side of the outwardly disposed recesses,
viii. each strip including, in cross-section, means integral therewith for
supporting said solar heat absorbing member in spaced apart relation above
approximately 85% of the plan surface area of each said strip by an amount
equal to approximately 20% of the depth of said fluid supply recesses;
b. a rigid solar heat absorbing member formed from metal and mounted upon
the upper surface of said base member in contacting engagement with each
of said strips,
i. the upper surface of said solar heat absorbing member containing a solar
radiation absorbing coating thereon,
ii. said solar heat absorbing member cooperating with said recesses to form
liquid supply channels each of which is isolated one from the other;
c. a cover member formed from a transparent material and secured to said
base member, said cover member having an upper, generally planar surface
spaced apart from the upper surface of said solar heat absorbing member,
said cover member permitting solar radiation to pass therethrough and
impinge upon said solar heat absorbing member for all angles of solar
radiation impingement from a direction normal to the upper surface of said
solar heat absorbing member plus or minus less than 90 degrees; and
d. an adhesive means for securing said solar heat absorbing member to said
strips, said adhesive means having flat bonding characteristics over the
environmental temperature range whereby thermal expansion of said base
member relative to thermal expansion of said solar heat absorbing member
occurs while maintaining a general planarity of the upper surface of said
solar heat absorbing member.
11. A solar heating panel as described in claim 10 in which each strip is,
in cross-section, generally of an inverted V-shaped configuration.
12. A solar heating panel as described in claim 10 in which the width to
depth ratio of each liquid supply channel varies between approximately 6.5
to 15.0.
13. A solar heating panel as described in claim 10 in which each liquid
supply channel has a mean hydraulic radius varying between approximately
0.018 and 0.027.
14. A solar heating panel comprising:
a. a base member having
i. a liquid impervious upper surface,
ii. a plurality of spaced apart fluid supply recesses formed in said upper
surface and extending longitudinally therealong,
iii. inlet and outlet manifolds, each manifold extending transversely
across one of the ends of said base member and each manifold being
disposed in fluid communication with each of said recesses,
iv. an inlet port disposed in fluid communication with said inlet manifold,
v. an outlet port disposed in fluid communication with said outlet
manifold,
vi. a fluid return recess formed in the upper surface of said base member
along one side thereof, said fluid return recess being adapted to be
placed in fluid communication with said outlet port, and
vii. a plurality of spaced apart strips formed on the upper surface of said
base member, said strips being disposed intermediate each of said recesses
and adjacent the outer side of the outwardly disposed recesses;
b. a rigid solar heat absorbing member formed from metal and mounted upon
the upper surface of said base member in contacting engagement with each
of said strips,
i. the upper surface of said solar heat absorbing member containing a solar
radiation absorbing coating thereon,
ii. said solar heat absorbing member cooperating with said recesses to form
liquid supply channels and a liquid return channel each of which is
isolated one from the other;
c. a cover member formed from a transparent material and secured to said
base member, said cover member having an upper, generally planar surface
spaced apart from the upper surface of said solar heat absorbing member,
said cover member permitting solar radiation to pass therethrough and
impinge upon said solar heat absorbing member for all angles of solar
radiation impingement from a direction normal to the upper surface of said
solar heat absorbing member plus or minus less than 90 degrees; and
d. an adhesive means for securing said solar heat absorbing member to said
strips, said adhesive means having flat bonding characteristics over the
environmental temperature range whereby thermal expansion of said base
member relative to thermal expansion of said solar heat absorbing member
occurs while maintaining a general planarity of the upper surface of said
solar heat absorbing member. |
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Claims |
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Description |
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FIELD OF THE INVENTION
This invention relates to a method and panel for use in transferring heat
to or from a liquid, said liquid being heated by solar radiation energy.
BACKGROUND OF THE INVENTION
Heretofore numerous methods and apparatuses for heating a liquid through
utilization of solar radiation waves have been proposed and constructed.
Each of these methods and apparatuses have, however, proved to be
disadvantageous for one or more reasons. Some prior art methods and
apparatuses have been ineffective due to the type of materials used. Other
prior art methods and apparatuses have been ineffective due to the
configuration of the fluid supply channels or passageways involved. Still
other prior art apparatuses have been ineffective due to the overall
configuration thereof. Other prior art apparatuses have been ineffective
due to the small quantity of liquid that can be processed therethrough.
Additionally, each of the prior art methods and apparatuses has been
relatively expensive and, in some cases, difficult to maintain adequately
for long operating periods. Illustrative prior art methods and apparatuses
are shown in U.S. Pat. Nos. 679,451, 1,250,260, 2,358,476, 2,553,302,
3,076,450, 3,077,190, 3,145,707, 3,190,816 and 3,387,602.
The method and solar heating panel of this invention overcomes the
disadvantages referred to above by providing a panel which is inexpensive
to manufacture, has a relatively long operating life and yet which is
highly efficient in heating liquid through the utilization of solar
radiation energy.
SUMMARY OF THE INVENTION
The solar heating panel of this invention comprises a base member formed
from an insulating material and having a liquid impervious upper surface,
a rigid solar heat absorbing member formed from a metal and containing a
black, solar radiation absorbing coating on the upper surface thereof, an
inverted cup shaped member formed from a transparent material and secured
to said base member, an elastic adhesive means for securing said solar
heat absorbing member to said liquid impervious upper surface, said
adhesive means having flat bonding characteristics (i.e., the strength of
the bond remains essentially unchanged) over the environmental temperature
range in which said panel will be used whereby thermal expansion of said
liquid impervious upper surface relative to thermal expansion of said
solar heat absorbing member takes place without adversely affecting the
general planarity of the upper surface of said solar heat absorbing
member. The base member includes a plurality of spaced apart fluid supply
recesses formed in the liquid impervious upper surface thereof. The base
member also includes inlet and outlet manifolds formed in the liquid
impervious upper surface each of which is disposed in fluid communication
with each of said recesses. The base member also includes inlet and outlet
ports disposed, respectively, in fluid communication with the inlet
manifold and the outlet manifold. The base member preferably includes a
fluid return recess formed in the upper surface thereof along one side
thereof. The base member also includes a plurality of spaced apart strips
formed on the liquid impervious upper surface, said strips being disposed
intermediate each of said recesses and adjacent to the outer side of the
outwardly disposed recesses. The solar heat absorbing member cooperates
with the recesses of said base member to form liquid supply channels and a
liquid return channel each of which is isolated one from the other. Each
liquid supply channel has a width to depth ratio varying between 6.5 and
15 and a mean hydraulic radius varying between approximately 0.018 and
0.027. The inverted cup shaped member is configured to eliminate shadow
areas in order to permit solar radiation to pass therethrough and impinge
upon said solar heat absorbing member for all angles of solar radiation
impingement from a direction normal to the upper surface of said solar
heat absorbing member plus or minus less than 90.degree.. The solar
heating panel member may also include an additional layer of transparent
material disposed in spaced apart relation to the upper surface of said
inverted cup shaped member and the upper surface of said rigid solar heat
absorbing member and spaced apart from same.
The method of this invention for heating a liquid comprises forming one or
more obstruction free, longitudinally extending liquid passageways one
side of each of which is formed from a metallic material wherein the outer
surface of said metallic material contains a black, solar radiation heat
absorbing coating and each passageway having a width to depth ratio
varying between approximately 6.5 to 15.0 and a mean hydraulic radius
varying between approximately 0.018 to 0.027, exposing the black, solar
radiation heat absorbing coating of said metallic material to solar
radiation energy, and heating a liquid by passing same through said
passageways and simultaneously maintaining a substantially constant
cross-sectional area flow path through said passageways. By such means,
the said liquid is accelerated as same flows from one end of said
passageway to the other end thereby reducing or eliminating the formation
of eddy currents or "dead" liquid pockets which reduce the quantity of
fluid that can flow therethrough as well as adversely affecting the
efficiency of heat transfer to the liquid flowing therethrough.
A primary object of this invention is to provide a new, novel and more
efficient method and solar heating panel for transferring heat to and from
a liquid flowing through said path and utilizing solar radiation energy to
heat said liquid.
Another object of this invention is to provide a method and panel as
aforedescribed which are greatly improved in efficiency of operation.
Another object of this invention is to provide a method and panel as
aforedescribed in which each liquid supply channel has a width to depth
ratio varying between approximately 9 and 13.5.
Another object of this invention is to provide a method and panel as
aforedescribed in which each liquid supply channel has a width to depth
ratio equal to approximately 10.
Another object of this invention is to provide a method and panel as
aforedescribed in which each liquid supply channel has a mean hydraulic
radius varying between approximately 0.018 and 0.023.
Another object of this invention is to provide a method and panel as
aforedescribed in which each liquid supply channel has a mean hydraulic
radius equal to approximately 0.023.
Another object of this invention is to provide a solar heating panel as
aforedescribed in which the liquid impervious upper surface is formed from
a metal.
Another object of this invention is to provide a solar heating panel as
aforedescribed in which the liquid impervious upper surface is formed from
a rubber material.
Another object of this invention is to provide a solar heating panel as
aforedescribed in which the upper surface of said inverted cup shaped
member comprises a segment of a generally spherically shaped surface
having a chord to radius ratio of not more than approximately 0.19.
Another object of this invention is to provide a solar heating panel as
aforedescribed in which each strip is configured to support said solar
heat absorbing member in spaced apart relation above a major portion of
the plan surface area of said strip.
Another object of this invention is to provide a solar heating panel as
aforedescribed in which each strip, as configured, supports said heat
absorbing member above approximately 85% of the plan surface thereof by a
distance equal to approximately 20% of the depth of the fluid supply
recess of said panel.
Another object of this invention is to provide a method for heating a
liquid as aforedescribed in which the step of heating a liquid includes
maintaining a substantially non-turbulent flow of said liquid through said
passageway.
Other objects and features of this invention will become apparent by
reference to the following specification and to the drawings.
IN THE DRAWINGS
FIG. 1 is a perspective view of a solar heating panel constructed in
accordance with the subject invention;
FIG. 2 is an exploded view of the solar heating panel shown in FIG. 1;
FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 4;
FIG. 4 is a plan view, partially broken away, of two interconnected solar
heating panels constructed in accordance with this invention;
FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 4;
FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 4;
FIG. 7 is an enlarged, fragmentary, cross-sectional view of a modified
embodiment of the panel shown in FIG. 2 taken transversely of the solar
heating panel;
FIG. 8 is an enlarged, fragmentary, cross-sectional view of an additional
embodiment of the panel shown in FIG. 2 taken transversely of the solar
heating panel;
FIG. 9 is an enlarged, fragmentary, cross-sectional view showing the
configuration of the currently preferred embodiment of a strip useful in
this invention; and
FIG. 10 is an enlarged, fragmentary, cross-sectional view showing another
embodiment of a configuration of a strip useful in this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The method and solar heating panel of this invention is especially adapted
to heat an enclosure, such as a house or the like, by extracting heat
energy from a liquid that has been heated by solar radiation. The solar
heating panels of this invention are considerably less expensive than
prior art heating panels, have a relatively long operating life and are of
increased efficiency in operation.
Referring now to the drawings, a solar heating panel 14 is shown comprising
a base member 16, a solar heat absorbing member 18, an inverted cup shaped
member 20 and an elastic adhesive means 22 (see panel 14' of FIG. 7).
The base member 16 is preferably formed as a composite member. The base
member 16 is formed to provide a liquid impervious upper surface 24. The
base member may be formed by vacuum forming an outer skin from a plastic
material, such as an acrylic, for the base member 16. It is believed that
the outer skin may also be formed from a polycarbonate. Said outer skin
will be liquid impervious. The outer skin, as formed, will then be filled
with an insulating material (such as a urea formaldehyde); however, the
composite base member will exhibit good insulative properties thereby
minimizing loss of heat therethrough. A plurality of laterally spaced
apart fluid supply recesses 26, see FIGS. 2 and 4, are formed in the
liquid impervious upper surface 24 and extend longitudinally of said base
member 16. An inlet manifold 28 and an outlet manifold 30 are also formed
in the liquid impervious upper surface 24 of said base member 16. Each
manifold 28 and 30 extend transversely across one of the respective ends
of said base member 16 and, also, is disposed in fluid communication with
each of said fluid supply recesses 26. The base member 16 also includes an
inlet port 32 disposed in fluid communication with the inlet manifold 28
and an outlet port 34 disposed in fluid communication with the outlet
manifold 30. The base member 16 preferably includes a fluid return recess
formed in the liquid impervious upper surface 24 of said base member along
one side thereof, the right hand side as viewed in FIG. 4. The fluid
return recess 36 is adapted to be placed in fluid communication with an
outlet port 34 such as through the use of a hollow tubular member 38. A
plurality of spaced apart strips 40 are formed on the liquid impervious
surface 24 of said base member 16. The planar strips 40 are disposed
intermediate each of the recesses 26 and 36 and adjacent the outer side of
the outwardly disposed recesses 26 and 36.
The solar heat absorbing member 18 is formed from metal having good heat
conducting characteristics such as aluminum. It has been found that the
upper surface of the member 18 should be maintained generally planar in
order to obtain an efficient operation of the panel 14. Thus, the member
18 is rigidly formed to resist bowing thereof as a result of thermal
expansion or contraction of the upper surface 24 relative to the thermal
expansion or contraction of the member 18. The upper surface of the member
18 contains a black, solar radiation absorbing coating 42 thereon.
Preferably, the coating 42 comprises a special layer of spectrally
absorbent black paint. The solar heat absorbing member 18 securely bonded
to the liquid impervious surface 24 of the base member 16 by an elastic
adhesive means 22. As bonded, the solar heat absorbing member cooperates
with the recesses 26 and 36 formed in the liquid impervious upper surface
surface 24 to form a plurality of liquid supply channels 44 and a liquid
return channel 46, see FIGS. 3 and 7. This construction isolates each of
the channels 44 and 46 one from the other.
The inverted cup shaped member 20 is formed from a transparent material
such as glass or plastic. The material selected must be resistant to
weathering, ultraviolet radiation, breakage, cracking and pitting which
might otherwise result from hail or wind storms. The upper surface 48 of
said member 20 is of a slight "dome" configuration, i.e., it is the
segment of a generally spherically shaped surface having a chord to radius
ratio of not more than approximately 0.19. It has been found that the
upper surface 48 of said member 20 has, when viewed in cross-section, a
generally convex surface having a radius of curvature of approximately
3.65 meters (135 inches). Such a configuration provides good strength
characteristics for member 20 to resist forces due to thermal expansion
and contraction and, also, to enable automatic drainage of moisture from
the upper surface thereof. The upper surface 48 is disposed in spaced
apart relation to the coating 42 of said member 18. It has been found that
good results are obtained from a panel 14 of this invention where the
upper surface 48 of member 20 is maintained approximately 4.4 cm (13/4
inches) above the coating 42 formed on member 18. As shown in FIG. 7 an
additional layer 50 of transparent material may also be disposed in spaced
apart relation to both the upper surface 48 and the coating 42. The layer
50 is spaced from the layer 48 by a distance of approximately 2.54 cm (1
inch). The transparent member 20 permits the solar radiation energy to
pass therethrough and impinge upon the coating 42 of the member 18. At the
same time, said member 20 particularly the upper surface 48, effectively
precludes reflection of long wave solar radiation waves (i.e., longer than
approximately 3 microns) outwardly through the upper surface 48. The use
of the additional layer 50 formed from transparent material further
reduces the reflection of solar radiation waves (particularly the longer
length waves) from the coating 42 of member 18 outwardly of the member 20.
It will be noted that the use of the inverted cup shaped member 20 as
described above and shown in the drawings enables solar radiation waves to
pass therethrough and impinge upon the coating 42 of the solar heat
absorbing member 18 for all angles of solar radiation impingement from a
direction normal to the upper surface of the member 18 plus or minus
slightly less than 90.degree.. More specifically, solar radiation waves
will impinge upon the coating 18 for all angles of solar radiation
impingement from a direction normal to the upper surface of the member 18
down to, but not including, 90.degree., i.e., waves which are directed
slightly less than tangential to the coating 42. This means that solar
radiation waves will impinge upon the coating 42 for the longest period of
time possible for any proper orientation of the panel 14 relative to the
force of solar radiation waves.
In order to obtain solar radiation impingement across the entire surface of
the coating 42 of member 18 for the longest period of time possible as
referred to above, the upper surface of the member 18 must be maintained
generally planar. More specifically, if the upper surface of the member 18
bowed in either direction, there will be reduction in the amount of time
that solar radiation waves may impinge thereon. It has been found that the
upper surface of the member 18 may be maintained generally planar by using
an elastic adhesive means having flat bonding characteristics over the
environmental temperature range to be encountered during use of the panel
14. For example, the elastic adhesive means 22 must not become embrittled
at low temperatures, i.e., down to approximately -29.degree. C. to
-34.degree. C. (-20.degree. to -30.degree. F.), nor become unnecessarily
soft at high temperatures, i.e., up to approximately 176.degree. C.
(350.degree. F.). Moreover, the bonding characteristics must remain
essentially unchanged over this environmental temperature range. Finally,
the adhesive means must stretch or deform when subjected to a force
resulting from the unequal expansion of the members 16 and 18 and yet
return to its former configuration when such force has been eliminated
upon a change in thermal conditions which produced such unequal expansion.
The use of silicone adhesive such as G. E. silicone RTV-630, manufactured
by General Electric Company, has been found to be suitable for this
application.
An important feature of this invention it to utilize liquid supply channels
which enable the transfer of heat energy from the member 18 to the
individual molecules of liquid in order to raise the temperature of the
liquid to a desired level while same is flowing through said channels. It
has been unexpectedly found that same may be accomplished through the use
of fluid supply channels or passageways which are generally rectangular in
cross-section and have a width to depth ratio varying between
approximately 6 and 15 and a mean hydraulic radius varying between
approximately 0.018 and 0.027. The mean hydraulic radius is defined as the
cross-sectional area of the fluid supply channel or passageway divided by
the wetted perimeter thereof. Preferably, the width to depth ratio of each
liquid supply channel or passageway should vary between approximately 9
and 13.5 and excellent results have been obtained where the width to depth
ratio equals approximately 10. Preferably, the mean hydraulic radius of
each liquid supply channel should vary between approximately 0.018 and
0.023 and excellent results have been obtained where the mean hydraulic
radius is equal to approximately 0.023.
The solar heating panels of this invention are preferably installed on the
upper surface of a roof in a manner to permit impingement of solar
radiation waves on the coating 42. For existing structures, the solar
heating panels may be installed on the upper surface of the roof of said
structure. For newly built structures, the solar heating panel of this
invention may be formed as an integral part of the roof. The flow of
liquid through solar heating panels mounted on a roof as aforedescribed is
against the force of gravity, i.e., upwardly from the lower most portion
of a solar heating panel to the upper most portion thereof. In this
manner, it is possible to maintain the liquid supply channels and the
liquid return channel completely full of liquid and thereby eliminate the
presence of air and gas bubbles to obtain a high degree of efficiency in
operation of said panels.
Understandably, the performance of a solar heating panel will depend upon a
number of factors such as the ambient temperature, the presence or absence
of clouds, particulate matter, water vapor and the like in the atmosphere
which would interfere with the transmission of solar radiation waves
therethrough, the angle of impingement of the solar radiation waves upon
the coating 42 of the solar heat absorbing member 18 and the amount and
efficiency of insulation used. The efficiency of the panel, on the other
hand, depends upon a number of other factors such as its geometry, fluid
contact to absorber surface ratio, flow rate and minimization or
elimination of "dead" liquid pockets associated with the sides of the
liquid flow channels. Applicants understand, however, that the amount of
heat energy thought to be available at a position above the atmosphere
under ideal conditions is 119.8 calories per square centimeter per hour
(442 BTU per hour per square foot) which is sometimes referred to as the
"Solar Constant." Applicants have been able to extract slightly more than
78.6 calories per square centimeter per hour (290 BTU per hour per square
foot) under as ideal conditions as was achieved in May, 1974, at Denver,
Colorado, but below the atmosphere. It will be understood, however, that
reduced performance for a solar heating panel constructed in accordance
with this invention resulted where less than ideal conditions were
encountered, i.e., a cloudy sky, different impingement angle and the like.
Nevertheless, applicants are not aware of any other solar heating panel
capable of operating with the degree of efficiency as has been achieved
with the solar heating panel of this invention.
It will be noted that FIG. 7 shows a solar heating panel 14' similar to the
solar heating panel of FIG. 2 except for the addition of the additional
layer 50 of transparent material disposed intermediate the upper surface
48 of base member 20 and the upper surface of the solar heat absorbing
member 18.
In FIG. 8 is shown another embodiment of a solar heating panel 14". The
solar heating panel 14" is similar to the solar heating panel 14 of FIG. 3
except that the liquid impervious upper surface 24' is formed from a layer
of a suitable material such as metal or rubber. The layer 24' of material
is secured to the base member 16' by an elastic adhesive means 22 as
already described above.
In FIG. 9 is shown the currently preferred embodiment of a strip 40' to be
incorporated in a panel constructed in accordance with this invention.
More specifically, the strip 40' as shown in FIG. 9 is, in cross-section,
generally of an inverted V-shaped configuration. The elastic adhesive
means 22 is disposed intermediate the lower surface of the solar heat
absorbing member 18 and a major portion (and preferably 85% or more) of
the plan surface area of said strip 40'. The distance separating the lower
surface of member 18 and the side 52 of each strip 40' is equal to
approximately 20% of the depth of the fluid supply recesses formed in the
liquid impervious upper surface 24".
In FIG. 10 is shown another embodiment of a strip 40" configured for
incorporation within a solar panel constructed in accordance with this
invention. The strip 40" contains boss means 54 for supporting the lower
surface of member 18 in spaced apart relation above a major portion
(preferably 85% or more) of the plan surface area of strip 40". The
distance separating the lower surface of member 18 and a major portion of
the upper surface of strip 40" is equal to approximately 20% of the depth
of the fluid supply recesses formed in the liquid impervious upper surface
24'".
As shown in FIGS. 2-4, the fluid return recess 36 is preferably formed in
the liquid impervious upper surface 24. Formation of the fluid return
recess 36 in said liquid impervious upper surface has been found to be
additionally beneficial in improving the overall efficiency of a solar
heating panel constructed in accordance with this invention since the
liquid does not lose any heat in flowing therethrough; rather, a slight
increase in heat of the liquid normally occurs. It will be understood,
however, that the fluid return recess is constructed of a sufficient size
to permit the return of the entire quantity of liquid flowing through the
plurality of fluid supply channels formed in the solar heating panel 14.
It will also be understood that the fluid return channel is not
constructed to have the width to depth ratios or the mean hydraulic radius
as described above with respect to the fluid supply channels. Finally, it
will be appreciated that the fluid return channel may comprise a separate
liquid conveyance means (not shown) formed outside of the solar heating
panel 14. For example, tubular member 38, see FIG. 4, may extend
longitudinally of the solar heating panel 14 back to a reservoir (not
shown) of heated liquid. Additionally, the upper most panel of one or more
series connected panels may be constructed in such a way that the liquid
flow passage represented by tubular member 38 may be formed within the
panel itself to provide fluid communication directly between the outlet
manifold 30 and the liquid return channel 36.
Illustrative dimensions of a solar heating panel constructed in accordance
with this invention are as follows:
Width of panel - 22 inches (56 cm.)
Length of panel - 4 feet (122 cm.)
Number of liquid supply channels - 19
Width of each liquid supply channel - 0.5 inches (1.3 cm.)
Depth of each liquid supply channel - 0.05 inches (0.127 cm.)
Width to depth ratio of each liquid supply channel - 10
Mean hydraulic radius of each liquid supply channel - 0.023
Flow through 19 liquid supply channels - 1 gallon per minute (3.8 liters
per minute)
Reynolds number - 1708.
Solar heat absorbing member - aluminum alloy 47 inches .times. 22 5/8
inches .times. 0.032 inches (119.4 cm. .times. 57.5 cm. .times. 0.081 cm.)
The method of this invention enables the efficient heating of a liquid
through the utilization of solar radiation energy. The method of this
invention comprises forming an obstruction free, longitudinally extending
liquid channel or passageway one side of which is formed from a metallic
material having good heat conducting characteristics, such as aluminum.
The outer surface of the metallic material contains a black, solar
radiation heat absorbing coating thereon. The coating is essentially
nonreflective and, thus, is highly efficient in absorbing heat energy from
solar radiation. Each liquid passageway is formed with a width to depth
ratio varying between approximately 6.5 and 15.0. Each liquid passageway
also has a mean hydraulic radius varying between approximately 0.018 and
0.027. Liquid passageways which are rectangular in cross-section and being
formed from 0.4 inches (1.02 cm.) to 0.6 inches (1.52 cm.) wide and 0.04
inches (0.102 cm.) to 0.05 inches (0.127 cm.) deep meet the aforementioned
criteria. The black, solar radiation | | |
