Note: Descriptions are shown in the official language in which they were submitted.
~L93~3
HEAT EXCHANGER
BACKGROUND OF THE INV~NTION
_
This invention relates to new and useful im-
provements in air to air heat exchangers for use in ex-
changing air between the exterior and interior of a
building.
Normal heat exchangers used for this purpose
merely exhaust inside air through a core and draw cold
outside air through opposing channels so that heat is
picked up by the outside air from the exhausting air
prior to the exhausting air being discharged. Due to
the higher relative humidity of the exhausting warm
air, a considerable amount of moisture is carried there-
by and the heat exchanging core often drops the tempera-
ture of this air be~ow the dew point thus causing the
water or moisture to condense and with cold outside air
passing through the heat exchanger, severe frosting of-
ten occurs. This frosting is so severe that the heat
exchanger becomes inoperative unless defrosting takes
place.
Conventional heat exchangers defrost by re-
versing the flow of air by routing the inside air through
the incoming air channels. Inasmuch as this inside air
3~
~35~33
is often contaminated, the channels normally carrying
the fresh outside air also becomes contaminated. Fur-
thermore, particle deposition can take place with the
subsequent reduction of cross-sectional area of channels
normally carrying the clean air inwardly.
Various methods for defrosting have been pro-
posed bnt all these methods add complication and effi-
ciency. Attempts have been made to manufacture a heat
exchange apparatus of this type which is substan~ially
free from frosting problems but todate have not met with
success.
SUMMARY OF THE INVENTION
It is accordingly one object of this lnven-
tion to provide a heat exchange apparatus which over-
comes these disadvantages and substantially operates
without the problem of frosting thus avoiding the com-
plications necessary for regular deErosting procedures.
The invention provides a heat exchange appa-
ratus for exchanging air between the exterior and inte-
rior of a building comprising an enclosure, a heat ex-
change core mounted within the enclosure, means asso-
ciated with the core dividing said enclosure into a
irst path for conveying outside air into the building
and a second path for conveying inside air to the out-
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side of the building, said second path passin~ through
i the core from an inlet end at which the air is warmest
~o an outlet end at which the air is coldest in heat
exchanging and air impervious relationship with said
first path, and a perforated baffle arranged in the
first path adjacent to and upstream of the core to con-
trol the spread across the core of outside air en~ering
the core and differentially perforated so as to pro-
; vide a greater area of perforation adjacent said inlet
end of the core than at said outlet end.
The baffle therefore controls the spread of
the cold air over the core so that more cold air is di-
rected to the warmer parts of the core. In this way,
the core is used to its maximum extent while prevent-
ing specific areas of the core freezing since immediate-
ly freezing commences, it soon spreads through the core
since the freezing inhibits movement of the warm air
through certain areas thus allowing the core to yet fur-
ther cool.
The baEfle is arranged so that the whole of the
cold air is applied to the surface of the core but is
spread over that surface.
~a ~ C3~
.~.~ ~ v~
_ 4
With the foregoing in view, and other advan-
tages aæ will become apparent to those killed in the art
to which this invention relates as this specification
proceeds, the invention is herein described by reference
to the accompanying drawings forming a part hereof, which
includes a déscription of the best mode known to the
applicant and of the preierred typical embodiment of the
principles of the present invention, in which:
DESCRIPTION OF THE DRAWINGS
___ ~_ _
Figure 1 is a partially schematic side
elevation sectioned in part showing the heat exchanger
installed through the wall of a building.
Figure 2 is a top plan view of the heat
exchanger with the air control valve door in the open
position.
Figure 3 is an isometric view of the core per
se.
Figure 4 iæ a cross-sectional view along the
lines 4-4 oi Figure 3 showing the internal construction
of the core.
In the drawings like characters o~ reference
indicate corresponding parts in the di~ferent figures.
3~93
_ 5 --
DETAILED DESCRIPTION
_
Proceeding therefore to describe the invention
in detail, reierence sbould firs~ be made to Figure 1 in
which 10 illus~rates an outside wall of ~ building and
11, the ceillng of the barn or building. The heat
exchanger assembly collectively designated 12 is prefera-
bly situated adjacent the junction of the wall and ceil-
ing and may be supported by means of struts 13 in a con-
ventional manner with the ma~or portion of the heat
egchanger be~ng situated internally of the building in
the area designated by re~erence character 14.
The heat exchanger includes a casing having an
upper side 15, a lower spaced and parallel side 16, a
rear wall portion 17, a ~ront wall portion 18 and spaced
and para~lel side walls 19.
A conventional heat exchanging core collective-
ly deslgnated 20 is supported within the enclosure by
meAns oi' brackets or plates 21 at an inclined angle as
shown in Figure 1, Figures 3 and 4 show details o~ the
core. The core 20, together with the supporting plates
21 divide the enclosure and the core into an outside air
intake conveying system and an inside air outlet
conveylng system as will hereinafter be described.
The core, includes a plurality of channels
extending longitudinally therethrough in the direction o~
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-- 6
arrow 22 and a plurallty of further channels extending
from the upper side to the lower side of ~he core at
right angles to the ~irst channels and indicated by
reference character 23 and lt should be noted that the
two sets of channels constitute pathways for the movement
of alr at right angles to one another and in heat
e~chan~in~ relationship but that the two pathways are air
impervious to one another so that no actual mi~ing of the
air occurs.
~ The pathway defined by the channels in the
direction o~ arrow 23 consitutes a first path through the
core and the pathway through the other channels in the
direction of arrow 22 constitutes a second path through
the core.
An outside air intake 23' is situated in the
upper side 15 of the enclosure and communicates with an
area 24 defined by the upper side of the core, the
support plate 21 and part of the upper wall 15 and this
area communicates directly with the upper side of the
first path 23 but is completely isolated from the second
path 22 o~ the core.
The lower side of the core e~tends between the
lower wall 16 and a ~urther support plate 21. Together
with the base o~ the core, the base 16 and the further
. .
~9;~3
-- 7
plate 21 define an area 26 which is also completely
sealed off from the second path 22. The areas 24 and 26
and the first path 23 through the core constitute the
aforementioned outside air intake conveying ~ystem.
The front wall 18 of the casing is preferably
hinged vertically on one side as at 25 60 that it may be
swung open for cleaning and Qaintenance as shown in
Figure 2. This front portion includes an inclined
divider 27 thus dividing the ~ront portion lnto an air
discharge section 28 and an air intake section 29 and the
area 26 below the core communicates with this air intake
section 29 and constitutes part of the outside air intake
conveying system hereinbefore mentioned. A fan assembly
3~ is mounted within the section 29 and adjustable air
discharge spouts 31 e~tend from the front wall 32 of this
section as clearly shown in Figures 1 and 2.
The area 28 of the front section 18 includes a
~urther fan assembly 33 drawing air through the open
front end 34 of the section 28 and discharging same into
an area 35 in the front of the casing above the support
plate 21 and the upper wall 15 and through the path 22 of
the core 20. It passes through the core and into a rear
area 36 below the upper and lower plates 21 and the wall
whereupon it passes through a discharge hood 37
~935~13
~ 8 _
situated e~teriorly o~ the building on the outer surface
of the wall 10 and discharges downwardly to the outside
air in the direction of arrow 38.
Outside air at ambient temperature is drawn in
through the intake 23', through the core along the first
path 23 and is discharged via ducts 31 to the interior of
the building, the movement o~ air being controlled by
fan 30.
At the same time, fan 33 draws warm moist air
from the building through the second path o~ the core 20
and discharges same e~teriorly of the building through
the hood 37.
An opening 43 is provided in the casing com-
municating with the section 26. The purpose of the open-
iDg iS fully described in our co-pending application
nu~ber 409,904 . The opening 43 1s covered by a
readily adjustable door 431 (shown in partly open posi-
tion) so that the area oi' opening communicating the area
2~ to the interior of the building can be varied depend-
ing upon requirements. In this way the amount of airdrawn through the heat e~change core 20 by the fan 30 can
be reduced and replaced by air recirculated i'rom the
interior oi' the building.
5~
In addition a further similar opening 44 is
provided in the area 3~ com~unicating the area 36
selectively to the interior of the building. Similarly
the opening 44 can be ~electively covered by a door 441.
The opening 44 allows an Qdjustable proportion of the air
passing through the core 20 from the interior of the
building to be recirculated back into the interior o~ the
building rather than e~it through thQ nozzle 37. Such
recirculated air is cooled by the block 20 and hence a
prop^rtion of the ~oisture contained in the air will have
been condensed out and deposited in the core for ejection
through a nozzle 39.
Turning now to the details of the heat e~change
core 20, this is shown in detail in Figures 3 and 4 and
comprises a plurality of separate cells 50, each formed
from a single aluminum sheet folded to form a tubular
conduit of slot shaped cross-section defined by two long
sides 51 and two short sides 52. The seam or overlapplng
section in the folded sheet is arranged at the bottom of
the cell remote from the air inlet 23'. The length of
the cell 50 from one end to the other end defines the
length 0!~ the block 20 in regard to the path 22 and the
width of the sides 51 transverse to the path 22 defined
~935~3
-- 10 --
the length o~ the core 20 relative to the path ~3.
The number of cells contained in the block can
vary in accordance with the air flow required. Each cell
50 is separated ~rom the ~ext cell by ~hree spacers 53
and 54 (Figure 3, and 55 ~Figure 4)0 The spacers 53 and
55 are secured in position by a resilient set material
which bonds the spacer into position and provides air
sealing around the ends of the tubular cells 50. A cas-
ing SG, 57 is wrapped around the outside of the core at
respective ends so as to clamp the cells together to form
the core. The resilient set material is indicated at 58
in Figure 4.
The end of the core 20 adjacent the fan 33 onto
which air in the path 22 is directed is provided with
sheet metal covers 59 ~nd 60. The covers 59 comprise
U-shaped members e~tending over the spacers 55 so that
each cover S9 extends from the interior of one tubular
cell 50 to the interior of the ne~t adjacent cell 50 in
close contact with the adjacent walls of the two cells 50
as to bridge the gap and direct air smoothly into one or
other of the cells. Two covers 60 are provided across
the top and the bottom of the core ad~acent the fan 33 to
provide smooth clean lines covering the casing 57 and
~35~
resilient material 5B and directing air properly into the
cells 50. The covers 59 and 60 act to prevent the ac-
cumulation of dirt and other debris carried from the
interior of the building by the ~an 33.
It will be noted that the sides 52 of the
tubular cell~ 50 remote from the seam are presented for-
wardly to~ard the flow of air in the path 23 ~rom the
inlet 23'. That is, the cold air coming from the
e~terior o~ the building first encounters the transverse
surfaces provided by the sides 52 and impinges thereon.
In addition the warm air from the interior o~ the build-
ing forwarded by the fan 33 is directed into the core
along the tubular cells 50 at an angle thereto so as to
impinge upon the other face o~ the sides 52. It will be
noted from Figure 1 particularly that the fan blades of
the fan 33 are substantially vertical whereas the upper
surfaces 52 lies at an angle to the horiæontal so that
the air transported in a substantially horizontal direc-
tion by the ian 33 impinges upon the sur~aces 52 at an
angle thereto. Thus the face oi' the sufaces 52 remote
irom the cold inlet air is swept by the ~arm interior air
continually ~o as to maintain the ~ur~ace 52 at a su~
cient temperature to avoid ~rosting. This applies also
to the upper portions o~ the ~urfaces 51 which are also
~i~935~3
12 -
~ree from the seam and hence ef~ective heat exchangers.
It will be noted also that only a single sheet of metal
separates the incoming cold air ~rom the outgoing warm
air and ~hus heat exchange is ef~ective and rapid in view
o~ the high thermal co~ductivity o the metal.
Furthermore, in order to ensure that ~rosting
does not occur during normally e~pected termperature
ranges, the apparatus can be organized so that a greater
volume of air is passed through the core 20 along the
path 22 than along the path 23. For this purpose it wlll
be noted that the area o~ the tubular cells i6 greater
than the area between the cells thus providing a greater
total area for the path 22 than ~or the path 23. In ad-
dition the fan 33 is preferably oi' a greater fan blade
diameter than the fan 30 so that it acts to propel a
larger volume o~ air. Furthermore the volume o~ air
passing through the core along the paths 22 and 23 can be
~odi~ied by opening and closing the openings 43 and 44,
Finally the amount oi~ air drawAn along the path 23 by the
Pan 30 can be reduced by partially closing a door 42 to
vary the inlet opening 23'. In practice it is pre~erred
that the volume of air passing along the path 22 is oi'
the order o~ twice the volume o~ air passing along the
path 23.
I~ order to prevent excess air being drawn out
5~3
- 13 ~
of the building thus reducing the static pressure within
the building to a level where the fan 33 is unab~e to
draw the ~ull volume of air, the openings 43 and 44 can
be adjusted. Specifically uncovering the opening 43 acts
to reduce the amount of air drawn through the core 23 by
the fan 30. Uncovering the opening 44 acts to return
some o~ the air passing along the path 22 back to the
interior of the rooM. In this way the heat exchanger
itself can be adjusted to control the volume of air
passing along the paths 22 and 23 ~uch that the former is
of the order of twice the latter while drawing the same
amount of air through the inlet 23' as it is ejected
through the nozzle 37. Of course a compensation for the
temperature difference must be taken into account in any
calculations since this will affect the instantaneous
volume of any particular quantity of air.
Alternatively the heat e~changer may be adjust-
ed to pump a greater volume of air ~rom the interior of
the building than it draws into the building with the
2~ balancing amount of air being drawn into the building
~rom other ventilation sources without any attempt to
heat the air as lt is drawn in.
Referring again to Figure 2, immediately up-
stream of the core 20 in the path of the outside air
~L9~
entering from the inlet 23' is provided a baffle plate ~1
including a plurality of holes 62 through which the air
passes in its movement to the front face of the core 20.
The holes at the right-hand end of the baf~le plate 61
are of a larger diameter than those at the le~t~hand end
such that the holes are gradated ~rom 1.5 inch diameter
down to 1-0 inch diameter in three or more zones. This
increased proportion of hole area per unit area at the
right-hand end of the core insures that the air is dis-
tributed across the face of the core with more of thecold air going to the warmer end oi' the core adjacent the
warm air inlet than goes to the colder end oi' the core
adjacent the warm air outlet. The ratio of the total
hole area to the total area of the plate is of the order
o~ 1 to 4 and this has been found to provide suitable
distribution o~ the air across the core ~ace.
It will be appreciated that the distribution of
air provided by the baffle ~1 assists in the avoidance of
icing since less air is directed to the cold end ofr the
core where icing is most likely to occur. The hole sizes
stated are only one example and in practice the variation
in hole size is calculated in accordance with ~easured
temperature drop across the heat e~change core ~rom the
warm air inlet to the warm air outlet. In an alternative
5~3
_ 15
arrangement (not shown) the increased proportion of
perforation at the right hand end can be provideed by
increasing the number of holes rather than increasing
the diameter of the holes.
THE SUPPLEMENTARY DISCLOSURE
Figure 5 is a partially schematic side eleva-
tional view similar to Figure 1 showing a modified heat
exchanger, the cross section being taken along the line
5-5 of Figure 6.
Figure ~ is a cross sectional view along the
line 6-6 of Figure 5.
Figures 5 and 6 show a modified arrangement
of a heat exchanger which is particularly useful for
acting as an air to air heat exchanger from a home or
other building which does not involve the ejection of
polluted or contaminated air.
The structure of the heat exchanger is sub-
stantially the same as that shown in Figures 1 through
4 apart from the following modifications:
The inside air inlet 70, the inside air outlet
71, the outside air inlet 72 and the outside air out-
let 73 are all modified to receive ducting so that the
heat exchanger generally indicated at 12 can be mounted
:Lnside the building with connections to duct work com-
~L~ 5~3
- 16
municating to suitable locations within the building
and communicating to an inlet and outlet outside the
building. For this purpose the outside air inlet 72
is positioned on a rear surface 74 of the heat exchanger
rather than in the upper surface as shown in Figure 1.
The most important difference is that the
housing includes devices which separate the second path
through the core that is the warm air path into three
separate portions indicated at 75, 76 and 77. This is
achieved initially by a divider plate 78 which separates
the portions 75 and 76 so that the warm air inlet 70
from the fan 33 communicates the warm air to one side
of the divider 78 so that they can only enter the por-
tion 75. At the end of the portion 75 that is at the
end of the core remote from the inlet 70, a part cylin-
dric~l plate 79 is mounted the length of which is co-
extensive with the height of the core and the radius of
which is suitable to turn the air exiting from the
first portion 75 into the second portion 76 for move-
ment back through the core in the opposite direction tothe Eirst portion.
At the front end of the core, the air exit-
ing from the second portion 76 enters a chamber defined
by the top wall of the enclosure, by the divider 78 and
~ 5 ~ 3
17
by a bottom support surface 80 so that it returns in a
direction parallel to the portion 75 along the third
portion 77 to the outlet 71.
The outlet 71 is confined to one third of the
end wall 74 and lies alongside the cylindrical deflector
plate 79.
Air entering from outside the building through
the cold air inlet 72 enters the chamber defined above
the core by the enclosure and encounters a baffle plate
61A having the same function as the baffle plate 61 in
Figure 1. In this case, however, the baffle plate 61A
is attached to the core and is closely spaced from the
upper surface of the core and lies parallel thereto. The
spacing in one example of the order of 1 inch and the
baffle plate is supported relative to the core by divi-
der plates 81, 82 which lie longitudinally of the core
and at right angles to the baffle plates 61A. The divi-
der plates 81, 82 are located at the transverse extent
of the core necessary to divide the portions 75, 76 and
77 one from the other. Thus, the cold air in the cham-
ber indicated at 83 above the baffle plate 61A enters
one or other of the portions 75, 76 and 77. The whole
of the upper face of the core is however available for
the cold air to enter.
5~3
- 18
As mentioned in relation to the baffle 61 of
Figure 1, the baffle 61A is also differentially perfora-
ted. In the example shown, the area above the portion
75 has the largest holes and also the largest number
of holes so that more air from the chamber 83 enters the
core at the portion 75 than at the portion 76 or the
portion 77. The number of holes as shown is constant
along the length of the portion 75 but it is possible
also to gradate the hole size from the inlet end of the
portion 75 to the outlet end thereof. In a similar man-
ner the holes in the baffle above the portion 76 are of
larger diameter than those above the portion 77 so that
the volume of air entering the portions 75~ 76 and 77
are gradated. The number of holes can be calculated in
accordance with measured temperatures in the respective
portions and if required a full gradation throughout
the whole of the warm air path of the holes can be cal-
culated by computer in accordance with inlet and outlet
temperatures of the warm air path.
The Ean 33 has a considerably larger capacity
than the fan 30 in view of the greater restriction to
air Elow provided by the long path of the portion 75,
76 and 77. The length of the warm air path is in view
of these portions increased relative to the cold air
35~3
- 19
path so that it is at least three times greater than the
cold air path~ This increase in length causes a con-
siderable increase in velocity of the air as it passes
through this path and this velocity increase assists in
sweeping the heat exchange surfaces of the core and in
mixing the air to provide the best heat transfer to the
surface.
In contrast, the cold air path comprises a
single path through the core of shorter lengths and the
whole of the inlet cold air is exposed to the whole of
the upper surface of the core. This arrangement is pro-
vided in order to reduce or avoid freezing of the core
since freezing will occur if a large amount of cold air
is ducted through a small portion of the core. In such
a circumstance, the large amount of cold air will over-
come the heat supplied to that area of the core by the
warm air and will commence freezing of the moisture in
the warm air thus blocking part of the core. Once part
of the core is frozen in this way the remainder will
quickly follow.
A door 43A is provided in the cold air path
downstream of the core to allow the entry and mixing
into that path of air from inside the building. It will
of course be appreciated that when the paths of air are
5~3
_ 20
designated warm and cold it is intended to refer to the
operation of the device during cold weather. However,
the device can of course be used in warm weather when
the interior of the house or building is coplder than
the outside. In this case the door 43A can be used to
introduce cold basement air into the air entering the
building for circulation around the building. The door
43A instead of being of the slide type shown in Figure 1
is of the awning type.
Since various modifications can be made in
my invention as hereinabove described, and many appa-
rently widely different embodiments of same made withln
the spirit and scope of the claims without departing
~rom such spirit and scope, it is intended that all
matter contained in the accompanying specification shall
be interpreted as illustrative only and not in a limit-
ing sense.
