Note: Descriptions are shown in the official language in which they were submitted.
CA 02349343 2001-05-O1
SPECIFICATION
Gas-to-Gas Heat Exchange Element
TECHNICAL FIELD
This invention relates to heat exchange segments, and a
gas-to-gas heat exchange element having a superposition of
the segments.
1o BACKGROUND ART
Conventionally, as is widely known, an air-conditioning
and ventilating fan apparatus used in a house, office or the
like has an air-to-air heat exchanger mounted therein.
Thus, various types of heat exchange elements therefor
are already known. For example, as a typical example, as
disclosed in "Japanese Patent Publication (Unexamined)
H6-101988" or "Japanese Patent Publication (Unexamined)
H5-288488", a heat exchange element has a plurality of heat
exchange segments, with a plurality of hollow resin spacers
secured at predetermined intervals to one surface of a heat
exchange sheet, superposed with directions of total lengths of
the hollow resin spacers staggered alternately by 90 degrees.
However, this known heat exchange element has draw-
backs. The hollow resin spacers of the heat exchange seg-
menu, since they are in the form of commercially available
1
CA 02349343 2001-05-O1
circular straws such as of polypropylene (hereinafter simply
called PP), easily roll and therefore are troublesome to handle
when manufacturing the heat exchange segments, for exam-
ple. When bonding the hollow resin spacers to the heat
exchange sheet, the bonding areas are insufficient and it is
difficult to secure them with sufficient strength. Therefore,
to increase the strength of the segments, an increased num-
ber of hollow resin spacers must be bonded, which results in
an increases material cost. A disposal of used heat exchange
l0 elements results in an increased quantity of waste.
It is also known to form the hollow resin spacers in
other shapes than circular, that is to say angular such as
square or triangular, or elliptical (as disclosed in "Japanese
Patent Publication (Unexamined) 562-29898", for example).
Such angular hollow resin spacers are custom-made and
expensive. Elliptical hollow resin spacers may be obtained
by appropriately deforming commercially available circular
straws such as of PP, but fail to eliminate the above-noted
drawback of bonding area shortage.
This invention has been made having regard to the state
of the art noted above, and its object is to provide a heat
exchange element, which uses compressed elliptical hollow
spaces to facilitate handling in time of manufacturing
exchange segments, and secures sufficient boding strength
with bonding areas increased when the spacers are bonded to
2
CA 02349343 2001-05-O1
heat exchange sheets.
DISCLOSURE OF THE INVENTION
To fulfill the above object, this invention employs the
following construction.
A gas-to-gas heat exchange element comprising a
superposition of heat exchange segments each having a
plurality of hollow resin spacers secured at predetermined
intervals to either surfaces of heat exchange sheets, wherein
1o said hollow resin spacers have a compressed elliptical
shape, and arranged with flat portions thereof contacting said
heat exchange sheets.
According to the heat exchange element of this inven-
tion, the hollow resin spacers of compressed elliptical shape,
not possible to roll, are easy to handle when manufacturing
the heat exchange element. The bonding areas between the
hollow resin spacers and heat exchange sheets are increased
to obtain sufficient bonding strength. Based on this, a
reduced number of hollow resin spacers may be secured. The
hollow resin spacers of compressed elliptical shape may be
obtained by deforming commercially available straws, for
example.
In the gas-to-gas heat exchange element according to
this invention, a plurality of first hollow resin spacers may be
secured at predetermined intervals to the heat exchange
3
CA 02349343 2001-05-O1
sheets to form gas flow channels opening in one direction only
longitudinally of said first hollow resin spacers, and a plural-
ity of second hollow resin spacers may extend in a direction
crossing a longitudinal direction of said first hollow resin
spacers and secured at predetermined intervals to the heat
exchange sheets. This construction has the following func-
tion and effect. Gases may be supplied for heat exchange to
the gas flow channels formed between the first hollow resin
spacers, and to the gas flow channels formed between the
l0 second hollow resin spacers extending in the direction cross-
ing the longitudinal direction of the first hollow resin spacers.
Further, the first hollow resin spacers may have a
dimension between flat surfaces of the compressed elliptical
shape different from a dimension between flat surfaces of the
compressed elliptical shape of said second hollow resin
spacers. This construction achieves an excellent heat
exchange where an inflow resistance of one gas and an out-
flow resistance of the other gas are in an unbalanced relation-
ship.
In the gas-to-gas heat exchange element according to
this invention, the heat exchange sheets may have patterns of
embosses formed thereon. Then, the heat exchange sheets
have an increased rigidity and are difficult to deform. Where
a heat exchange is effected between gases supplied to the gas
flow channels formed between the hollow resin spacers, a
4
CA 02349343 2001-05-O1
situation in which the lower heat exchange sheet and heat
exchange sheet are deformed to contact one another is
prevented. The heat exchange sheets have increased surface
areas, and the gases may be caused to flow as divided or
meandering in the gas flow channels, thereby extending flow
paths. As a result, an improvement is made in heat transfer
and moisture transfer properties.
Preferably, one end of each heat exchange sheet is
secured only to a flat portion of one of the hollow resin spac-
ers, or to a flat portion and a curved portion (r-portion) of one
of the hollow resin spacers. The former is advantageous
from the viewpoint of reducing the amount of use of the heat
exchange sheets. The latter is advantageous in securing
strength and in heat-exchange performance.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a heat exchange segment
in a first embodiment
Fig. 2 is a sectional view of a hollow resin spacer
Fig. 3 is a perspective view of a heat exchange element
in the first embodiment
Fig. 4 is a cross-sectional view of an air-conditioning and
ventilating fan apparatus
Fig. 5 is a view showing a way in which heat exchange
sheets are secured a first hollow resin spacer of compressed
5
CA 02349343 2001-05-O1
elliptical shape
Fig. 6 is a view showing another way in which the heat
exchange sheets are secured to the first hollow resin spacer of
compressed elliptical shape
Fig. 7 is a perspective view of a heat exchange segment
in a second and a third embodiments
Fig. 8 is a perspective view of a heat exchange element
in the second and third embodiments
Fig. 9 is a plan view showing an emboss pattern formed
on an upper heat exchange sheet
Fig. 10 is a plan view showing an emboss pattern
formed on a lower heat exchange sheet
Fig. 11 is a view showing a height of an emboss formed
on the lower heat exchange sheet
Fig. 12 is a view showing gas currents
Fig. 13 is a plan view showing another emboss pattern
formed on the lower heat exchange sheet
Fig. 14 is a plan view showing another emboss pattern
formed on the lower heat exchange sheet
Fig. 15 is a view showing a contact between embosses
Fig. 16 is a view showing gas currents in a location
having no emboss
Fig. 17 is a view showing gas currents in a location
having embosses
Fig. 18 is a view showing first and second hollow resin
6
CA 02349343 2001-05-O1
spacers superposed in the third embodiment and
Fig. 19 is a plan view of an air-conditioning and
ventilating fan apparatus in the third embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of this invention will be
described in detail hereinafter with reference to the drawings.
First Embodiment
In Fig. l, a heat exchange segment 1 has three first
hollow resin spacers 2a to which a lower heat exchange sheet
3a and an upper heat exchange sheet 3b are secured, and
three second hollow resin spacers 2b secured to the upper
heat exchange sheet 3b.
The first hollow resin spacers 2a are arranged equidis-
tantly, and the second hollow resin spacers 2b also are
arranged equidistantly. An appropriate adhesive is used to
secure the first hollow resin spacers 2a and heat exchange
sheets 3a and 3b, as well as the heat exchange sheet 3b and
the second hollow resin spacers 2b.
2o Thus, as shown, gas flow channels 4a are formed that
open in one direction only longitudinally of the first hollow
resin spacers 2a (Y-direction in the figure). The second
hollow resin spacers 2b have longitudinally opposite ends
thereof disposed in the direction (X-direction in the figure)
perpendicular to the longitudinal direction (Y-direction in the
7
CA 02349343 2001-05-O1
figure) of the first hollow resin spacers 2a.
The first and second hollow resin spacers 2a and 2b,
with a sectional shape as shown in Fig. 2, are of compressed
elliptical shape having a 6mm r surface-to-surface dimension
La and a 2mm flat surface-to-surface dimension Lb, for
example.
Generally, La/Lb is 2 to 5. Such first and second
hollow resin spacers 2a and 2b of compressed elliptical shape
may be obtained by deforming commercially available circular
to PP straws or polyethylene terephthalate (hereinafter called
simply PET) straws.
As noted above, the heat exchange segment 1 according
to this invention has the first and second hollow resin spacers
2a and 2b of compressed elliptical shape. Therefore, where,
for example, heat exchange sheets 3a and 3b formed of a
paper material such as paper impregnated with calcium
chloride to have heat transfer property, moisture permeabil-
ity and fire resistance are bonded to the first hollow resin
spacers 2a, large bonding areas may be secured therebetween
2o to obtain sufficient bonding strength.
Based on this, a reduced number of the first and second
hollow resin spacers 2a and 2b are needed for production of
each heat exchange segment. Thus, where a plurality of
heat exchange segments 1 are superposed as shown in Fig. 3,
relatively large gas flow channels 4a and 4b may be formed to
8
CA 02349343 2001-05-O1
realize a reduced pressure loss.
The first and second hollow resin spacers 2a and 2b of
compressed elliptical shape, not possible to roll, are easy to
handle when manufacturing the heat exchange segments 1.
Further, where a heat exchange element 5 is formed by
superposing the heat exchange segments l, the compressed
elliptical shape stabilizes the shape maintenance of heat
exchange element 5. Thus, the heat exchange element 5
obtained has excellent shape stability, not easily collapsible.
to The first hollow resin spacers 2a and second hollow
resin spacers 2b have an excellent gastight feature at oppo-
site ends thereof to prevent gas leakage. This completely
prevents gas mixing between one gas flow channel and
another gas flow channel.
In addition, the first and second hollow resin spacers 2a
and 2b of compressed elliptical shape have a strong flexing
resistance in the direction of width (direction La in Fig. 2),
and therefore have characteristics similar to those of rigid
spacers. Moreover, because of the small thickness (dimen-
sion Lb in Fig. 2), the heat exchange element 1 may be formed
by superposing an increased number of heat exchange seg-
ments 1. Since the first hollow resin spacers 2a and second
hollow resin spacers 2b are arranged in the relationship
perpendicular to one another, the heat exchange segments 1
obtained have appropriate rigidity not easily deformable.
9
CA 02349343 2001-05-O1
In superposing the heat exchange segments 1, a suitable
adhesive is used to secure the heat exchange segments 1
together. Thus, the heat exchange element 5 of layer struc-
ture is obtained easily as seen in Fig. 3 showing a perspective
view thereof. A heat exchange sheet 3c is bonded to the
uppermost heat exchange segment 1.
With this heat exchange element 5, heat exchanging
gases are supplied to the gas flow channels 4b extending in
one direction and the other gas flow channels 4a formed
l0 perpendicular thereto. That is, for example, indoor air
(unclean air) may be supplied to the gas flow channels 4b
extending in one direction, and outdoor air (fresh air) to the
other gas flow channels 4a for heat exchange.
This state is shown in Fig. 4. In this figure, an
air-conditioning and ventilating fan apparatus 12 attached to
an outer wall 11 of an office or the like has a heat exchanger
14 and a ventilator 15 mounted in a casing 13. The heat
exchange element 5 is mounted in the heat exchanger 14.
Partitions 20-23 are arranged to define a passage 16 for
supplying indoor air to the gas flow channels 4b extending in
one direction and a passage 17 for discharging the air there-
from, and a passage 18 for supplying outdoor air to the other
gas flow channels 4a and a passage 19 for discharging the air
therefrom.
The heat exchange element 5 is expendable and is
to
CA 02349343 2001-05-O1
replaced with a new one as necessary. At this time, the heat
exchange element, which is elastically deformable in the
direction of superposition, may easily be detached from and
attached to an element mounting portion of heat exchanger
14. An old heat exchange element 5 replaced is discarded.
Having described one embodiment hereinbefore, this
invention allows two or more, i.e. a desired number, as neces-
sary, of first and second hollow resin spacers 2a and 2b to be
selected for the heat exchange segment 1.
l0 The second hollow resin spacers 2b, apart from the
arrangement in the direction (X-direction in the figure)
perpendicular to the longitudinal direction (Y-direction in the
figure) of the first hollow resin spacers 2a, may be arranged
in a non-perpendicular direction as in a rhombic heat
exchange segment, for example. In other words, the second
hollow resin spacers may be arranged in a direction crossing
the longitudinal direction (Y-direction in the figure) of the
first hollow resin spacers 2a, depending on the shape of the
heat exchange segment seen in plan view.
Apart from obtaining the first and second hollow resin
spacers 2a and 2b of compressed elliptical shape by deforming
commercially available circular PP straws or PET straws, the
first and second hollow resin spacer 2a and 2b of compressed
elliptical shape may be molded by other methods. In this
case, Ca0 powder or CaCOs powder may be mixed into a
11
CA 02349343 2001-05-O1
molding material to improve fire resistance, adhesive prop-
erty and strength. Adhesive property may be improved by
mixing Ca0 powder or CaCOs powder since powder such as
Ca0 powder or CaCOs powder can roughen the surfaces.
These exchange segments 1 may have any shape in plan
view, such as square, rectangular, rhombic or the like. The
heat exchange sheets 3a, 3b and 3c may be formed of other
materials than the paper impregnated with calcium chloride.
The dimensions of the compressed elliptical shape may be
varied as appropriate.
In addition, the heat exchange sheets 3a and 3b are
secured (usually bonded) to the first hollow resin spacers 2a
of compressed elliptical shape, preferably as shown in Figs. 5
and 6.
Fig. 5 shows one end of each of the heat exchange sheets
3a and 3b secured only to a flat portion of a first hollow resin
spacer 2a of compressed elliptical shape (the other end not
shown being secured likewise). Fig. 6 shows one end of each
of the heat exchange sheets 3a and 3b secured to a flat por-
tion and an r-portion of a first hollow resin spacer 2a of com-
pressed elliptical shape (the other end not shown being
secured likewise). Instead of dividing into the heat exchange
sheets 3a and 3b, one heat exchange sheet may be wrapped
on and bonded to the first hollow resin spacers 2a.
The construction noted above in which the opposite ends
12
CA 02349343 2001-05-O1
of the heat exchange sheets 3a and 3b are completely secured
to the first hollow resin spacers 2a can eliminate the draw-
backs of the opposite ends of the heat exchange sheets 3a and
3b not being completely secured (the ends of the heat
exchange sheets 3a and 3b being secured only to the flat
portions and not secured to the r-portions as shown in Fig. 5,
for example). Such drawbacks are that, where the heat
exchange segments are superposed, the free ends of the
sheets not secured become obstructive to gas currents to
to lower heat exchange performance, or the free ends of the
sheets flap to generate an unpleasant sound (noise). It is
thus preferable to secure the opposite ends of heat exchange
sheets 3a and 3b completely.
The former (Fig. 5) is advantageous from the viewpoint
of reducing the amount of use of heat exchange sheets 3a and
3b. However, the latter (Fig. 6) is advantageous in securing
(usually bonding) strength.
Second Embodiment
As in the first embodiment, a heat exchange element 5
in the second embodiment is formed by superposing heat
exchange segments 1. Further, in the second embodiment,
as shown in Fig. 7, heat exchange sheets 3a and 3b constitut-
ing each heat exchange segment 1 have emboss patterns
formed thereon. That is, the lower heat exchange sheet 3a
has embosses 25a formed in a predetermined pattern thereon
13
CA 02349343 2001-05-O1
(see Fig. 10). The upper heat exchange sheet 3b has
embosses 25b formed in a predetermined pattern thereon (see
Fig. 9).
Consequently, the heat exchange sheets 3a and 3b have
a further reinforced rigidity and are difficult to deform.
Where a heat exchange is effected between gases supplied to
gas flow channels 4a and 4b shown in Fig. 8, a situation in
which the lower heat exchange sheets 3a and heat exchange
sheets 3b are deformed to approach and contact one another
is prevented substantially completely.
The heat exchange sheets 3a and 3b have increased
surface areas for contacting the gases undergoing the heat
exchange. As indicated by arrows in Figs. 9, 10 and 12, the
gases may be caused to flow as divided or meandering in the
gas flow channels 4a and 4b, thereby extending flow paths.
As a multiplier effect of these, an improvement is made in
heat transfer and moisture transfer properties.
Assuming that, in Fig. 11, the lower heat exchange
sheet 3a and upper heat exchange sheet 3b have a spacing G
therebetween, the embosses 25a and 25b have a height H in a
range of at least 0.3G up to 0.7G. However, where necessary,
the range may be at least 0.3G to less than l.OG.
The embosses 25a and 25b divide the gas currents in the
flow channels into branching or meandering gas currents and
up and down gas currents flowing over the embosses (see Fig.
14
CA 02349343 2001-05-O1
12), resulting in varied flow velocities and directions to gener-
ate turbulence in the flow channels. This breaks boundary
layers caused by laminar flows occurring with flat paper.
Consequently, efficient counter currents are formed in
the flow channels by various combinations of perpendicular
currents along the gas flow channels 4a and 4b, branching or
meandering currents, and up and down currents. This
further improves the heat transfer and moisture transfer
properties.
As in the first embodiment, the heat exchange segments
1 are superposed by securing the heat exchange segments 1 to
one another with a suitable adhesive or adhesive tape.
Thus, the heat exchange element 5 of layer structure is
obtained easily as seen in Fig. 8 showing a perspective view
thereof. A heat exchange sheet 3c not having embosses
formed thereon is bonded to the uppermost heat exchange
segment 1.
As in the first embodiment, the heat exchange element 5,
with the emboss patterns formed, is used in an
air-conditioning and ventilating fan apparatus 12 attached to
an outer wall 11 of an office or the like. The shape of heat
exchange segment 1, securing of heat exchange sheets 3a and
3b to the first hollow resin spacers 2a and other aspects are
the same as in the first embodiment. Further, apart from
the above-noted aspects of the second embodiment, the follow-
CA 02349343 2001-05-O1
ing aspects may be cited regarding emboss pattern forms and
emboss arrangements.
The embosses 25a on the lower heat exchange sheet 3a
and the embosses 25b on the upper heat exchange sheet 3b
may be formed in predetermined patterns as necessary. Fig.
13 and 14 show other patterns of embosses 25a. The em-
bosses 25b also may be formed in the same patterns, but their
phase may be shifted or the direction of the pattern may be
varied.
l0 The embosses 25a and 25b may have any shape in verti-
cal section such as circular or truncated cone shaped, and any
shape in plan such as point-shaped, linear, dashed or
cross-shaped. The heat exchange sheets 3a, 3b and 3c may
have uneven surfaces with a crepe (gathering) in creases.
The embosses 25a and 25b may be formed on opposite
surfaces of both or one of the lower heat exchange sheet 3a
and upper heat exchange sheet 3b as necessary. Further,
where the embosses 25a are formed on opposite surfaces of
the lower heat exchange sheet 3a, the upper heat exchange
sheet 3b may have no embosses if such are not needed.
In other words, regarding the pattern shape and
arrangement of the embosses, a relationship should be main-
tained in which the same patterns do not overlap in the
direction of superposition of the segments. Thus, the pat-
terns may be shifted in phase or varied in direction to avoid a
16
CA 02349343 2001-05-O1
state as shown in Fig. 15.
Fig. 16 shows gas currents through a location without
the embosses 25a and 25b. Fig. 17 shows gas currents
through a location with the embosses 25a and 25b. (Though
embosses 25b are not shown in Fig. 17, the same currents
occur where the embosses 25b are formed.) It will be under-
stood that the latter has an advantage over the former in that
turbulence can break boundary layers that lower heat trans-
fer and material transfer performance.
l0 Third Embodiment
As in the first embodiment and second embodiment, a
heat exchange element 5 in the third embodiment is formed
by superposing heat exchange segments 1. As in the second
embodiment, as shown in Fig. 7, heat exchange sheets 3a and
3b constituting the heat exchange segment 1 have emboss
patterns formed thereon.
The first hollow resin spacers 2a have an r surface-to-
surface dimension La equal to that (La) of the second hollow
resin spacers 2b. In the third embodiment, the second
hollow resin spacers 2b have a flat surface-to-surface dimen-
sion Lb 1.2 to 1.3 times as large as that (Lb) of the first hollow
resin spacers 2a.
The second hollow resin spacers 2b may, for example,
have a 5.Omm r surface-to-surface dimension La, a 2.Omm flat
surface-to-surface dimension Lb, a O.lmm thickness, and a
17
CA 02349343 2001-05-O1
171mm total length. The first hollow resin spacers 2a may,
for example, have a 5.Omm r surface-to-surface dimension La,
a l.6mm flat surface-to-surface dimension Lb, a O.lmm thick-
ness, and a 171mm total length.
As in the first embodiment, the heat exchange segments
1 are secured to one another by using a suitable adhesive or
adhesive tape.
Thus, the heat exchange element 5 of layer structure is
obtained easily as seen in Fig. 8 showing a perspective view
l0 thereof. A heat exchange sheet 3c not having embosses
formed thereon is bonded to the uppermost heat exchange
segment 1. This heat exchange element 5 defines gas flow
channels 4a having a smaller opening area, and gas flow
channels 4b having a larger opening area.
That is, the gas flow channels 4a and gas flow channels
4b have the same horizontal dimension but, as shown in Fig.
18, the dimension Ga in the direction of height of gas flow
channels 4b (Z-direction) is larger than the dimension Gb in
the direction of height of gas flow channels 4a (Z-direction).
2o This effects an excellent heat exchange where an inflow
resistance of one gas (e.g. gas A) and an outflow resistance of
the other gas (e.g. gas B) are in an unbalanced relationship.
Specifically, Fig. 19 illustrates a heat exchange between
gas A (outdoor air) flows in from outside partitioned by an
outer wall 11 and gas B (indoor air) discharged outdoors from
18
CA 02349343 2001-05-O1
the room. Air is free under atmospheric pressure with no
outdoor obstruction, and only a small resistance is applied to
the inflow of outdoor air. On the other hand, a larger resis-
tance is applied to the outflow of indoor air, depending on a
room size, a spatial relationship with adjoining rooms, an
airtight condition, and opening and closing of doors. Gas B
(indoor air) flows through the gas flow channels 4b of heat
exchange element 5 having the larger opening area than the
gas flow channels 4a through which gas A (outdoor air) flows.
to Consequently, a heat exchange is performed while maintain-
ing a pressure loss difference OP not exceeding 3Pa.
The illustrated air-conditioning and ventilating fan
apparatus has an exhaust fan 15a, a suction fan 15b, a filter
26 and heat exchange element 5 replaceably attached to a
support 27 mounted in a casing 13.
In this case, the dimensions Ga and Gb in the direction
of height of gas flow channels 4a and 4b are appropriately
adjusted by a compression applied in Z-direction by an
appropriate device not shown. Consequently, Ga and Gb
become smaller than Lb, but such an adjustment is possible
since the first and second hollow resin spacers 2a and 2b are
elastic.
Since the flat surface-to-surface dimension Lb of the
first hollow resin spacers 2a is different from the flat
surface-to-surface dimension Lb of the second hollow resin
19
CA 02349343 2001-05-O1
spacers 2b, the dimensions Ga and Gb in the direction of
height of gas flow channels 4a and 4b do not become equal
(Ga=Gb) even when the heat exchange element 5 is com-
pressed in Z-direction. The size difference between the two
remains fixed.
The above construction has the relationship of Ga>Gb.
A relation of Ga<Gb may be adopted as necessary, that is the
flat surface-to-surface dimension Lb of the first hollow resin
spacers 2a may be made larger than the flat surface-to-
surface dimension Lb of the second hollow resin spacers 2b.
This construction also effects an excellent heat exchange
where an inflow resistance of one gas and an outflow resis-
tance of the other gas are in an unbalanced relationship.
The difference is provided in the flat surface-to-surface
dimension Lb, rather than the r surface-to-surface dimension
La between the first and second hollow resin spacers 2a and
2b. This is because a difference provided in the r surface-to-
surface dimension La would result in different widths of
adhesive application for securing the heat exchange sheets 3a
and 3b, and hence an imbalance in sheet adhesion to lower
heat transfer and moisture penetration capabilities.
It is preferable to form the embosses 25a and 25b, but
these may be omitted where they are unnecessary. The
embosses may have any shape in vertical section such as
circular or truncated cone shaped, and any shape in plan such
CA 02349343 2001-05-O1
as point-shaped, linear, dashed or cross-shaped. Their
patterns may be any patterns. The heat exchange sheets 3a,
3b and 3c may have uneven surfaces with a crepe (gathering)
in creases.
The shape of heat exchange segment l, securing of heat
exchange sheets 3a and 3b to the first hollow resin spacers 2a
and other aspects are the same as in the first and second
embodiments.
1o INDUSTRIAL UTILITY
Thus, the gas-to-gas heat exchange element according to
this invention is suitable for installation in an
air-conditioning and ventilating fan apparatus used in a
house, office or the like.
21
