Note: Descriptions are shown in the official language in which they were submitted.
~C~78~
Thls invention relates to a heat and moisture
transferring system for effecting exchange of heat and
moisture between two streams of air.
There have hitherto been known in the art two
types of heat and moisture transferring devices, or
devices of the rotary type and the static type, operat~ve
to simultaneously effect heat exchange with respect to
latent heat and sensible heat, thereby enabling heat to
be recovered with a high degree of efficiency.
In one aspect of the present invention there is :~
provided a system for transferring heat and moisture
between first and second air streams comprising, in
combination: a first conduit means for said first air
stream; a second conduit means for said second air
stream; heat and moisture transferring means comprlsing
a multitude of open-ended air passages defined by moisture
absorptive and heat conductive material, a first set of :
said air passages being disposed in said first conduit -
means for permitting said first air stream to pass .
thèrethrough and a second set of said air passages ;
being disposed in said second conduit means for permitting
said second air stream to pass therethrough; means . :
- disposing the first and second set o air passages
alternatively so that heat and moisture are transferred ..
between the first and second air streams passing through .
2S said passages through the moisture absorptive and heat
conductive material; and a heat transmitting system
including a first heat exchanging means disposed in said .~.
first condui.t means upstream of said heat and moisture
transferring means for exchanging heat between said first
air stream and a heat transmitting medium, a second heat
exchanging means disposed in said second conduit means
upstream of saia heat and molsture transferring means for
exchanging heat ~etween sa;d second air stream and said
heat transmltting medïum, and thîrd conduit means
connecting said first and second heat exchanging means
together for forming a closed circuit for said heat
transmitting medium.
In the drawings illustrating the invention:
Fig. 1 is a perspective view, with certain
parts being broken away, of a rotary type heat and mois-
ture transferring device used in the heat and moisture
transferri~g system according to the present invention;
Fig. 2 is a perspective view schematically
showing essential portions of a static type heat and
moisture transferring device used in the heat and
moisture transferring system according to the invention;
Fig. 3 is a schematic view of a heat and
moisture transferring system of the prior art;
Figs. 4 and 5 are psychrometric charts showing
the relation between the temperature and the humidity of
the air passing through the system shown in Fig. 3;
Fig. 6 is a schematic view of the heat and
moisture transferring system comprising one embodiment
of the invention;
Fig. 7 is a schematic view of another embodi-
ment of the invention;
Fig. 8 is a psychrometric chart showing the
I temperature-humidity characteristics of the embodiment
shown in Fig. 6;
Fig. 9 is a graph showing the relation between
the preheating ratio and the total heat recovery
efficiency;
l 1
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~ig. 10 ls a schematic view of still another
embodiment of the invention;
Fig. 11 is a schematic view of a further
embodiment of the invention; and
Fig. 12 is a perspective view, with certain
parts being broken away, of the embodiment shown in
Fig. 6.
Fig. 1 shows a commonly used device of the rotary type. As
shown, the heat and moisture transferring device 3
comprises a heat and moisture transferrer matrix 4 formed
by winding, in roll rorm, a sheet of asbestos paper
consisting of plane member and a corrugated member both
impregnated with a moisture absorbing agent. As shown in :.
Fig. 3, the device 3 is mounted for rotation of the heat
and moisture transferrer matrix 4 across an air supply pas- ~
sage 1 and an air exhaust passage 2 divided by a partition `.
wall 11 lnto upper and lower passages or left and right
passages. One example of the rotary type heat and
moisture transferring device is disclosed in US Patent `
No. 3,587,723. ~leanwhile Fig. 2 shows a commonly used
heat and moisture transferring device of the static type
comprising a plurality of corrugated members 4a of ~: ~
asbestos paper impregnated with a moisture absorbing ~ .
agent and a plurality of plane members 4b of the same
material as the corrugated members 4a impregnated with :~
the same moisture absorbing agent, such corrugated
members 4a and plane members 4b being mounted across
the two air passages ln such a manner that they are
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l alternately piled in vertically stacked relationshlp
so that the layers of the corrugated members 4a will
intersect one another perpendicularly and the layers of
the corrugated members 4a of odd numbers communicate
with the air supply passage l while the layers of the
corrugated members 4a of even numbers communicate with
the air exhaust passage, for example. This type of
device ~s disclosed in US Patent No. 3,666,oo7.
Assume that, when heating of a space is effected
10 in wintertime, such heat and moisture transferring device ~.
3 is used for recovering heat from return air RA from
the heated space and exhausting the return air RA as
exhaust air EA to the atmosphere, while the recovered
heat is given to outdoor air OA which is introduced
into the space as supply air SA. If the return air RA
has an inordinately high moisture content, or if, as
shown in a psychrometric chart i.n Fig. 4, the outdoor
air OA has a temperature 0C and a humidity 75% and the
return air RA from the heated space has a temperature ~ :
20C and a humidity 95%, for example, the.straight
line connecting the two points representing the outdoor
air and return air in the chart will intersect the
saturation line of relative humidity 100% at a point A
(17C) and a point B (5C). When this is the case,
the return air RA will move downwardly along the broken
line as it is being cooled by the heat and moisture
transferring device 3 until its humidity becomes lQ0%
at the polnt A where it moves outwardly of the saturation
line. The broken line will intersect the saturation line
again at the point B. The return air is exhausted to
~.~q~38~
1 the atmosphere as exhaust air EA. When this phenomenon
occurs, dew wlll be formed on the surfaces of the heat
and moisture transferrer matrix 4 between the points A
and B, because the humidity o~ the return air RA is
over 100% in this section of the broken line and the
moisture in the return air RA condenses. The formation
of dew on the sur~aces of the heat and moisture trans- ;:
.ferrer matrix 4 will cause effluence of the moisture
absorbing agent, thereby causing a reduction in the ~ :
10 moisture absorbing erriciency of the heat and moisture ~ -
transferrer matrix 4.
On the other hand, ir the return air RA has an
inordinately high humidity and the.outdoor air OA has an ;
extremely low temperature, or if the return air has a .. .
15 temperature 20C and a humidlty 75% and the outdoor :~ :
air has a temperature -20C and a humidity 100%, ~or
example, the strai~ht line connecting the~~two points
representing the return air and the outdoor alr in a ..
psychrometric chart in ~ig. 5 will intersect the ~ .
saturation line of relative humidity 100% at a point C ~
(13C) and a point D (-20C). Thus, when the return air .
RA and outdoor air OA are introduced into the heat and moisture
transferring device 3, some portions of the air becomes
higher than lOOg in humidity and below 0C in temperature~
so that the formation of frost occurs on the surfaces of the
heat and moisture transferrer matrix 4. Combined with an
increase in the resistance offered by the air passages to the
streams of air, this causes a reduction in the performance of
the heat and moisture transferring device 3.
3 As described hereinabove, the heat and moisture
. '
3 ~
- .-~' ....
. .
1 transferring device 3 has the disadvantage of being
unable to recover heat, without causing any trouble,
when the return air RA from the heated space and the
outdoor air OA from the atmosphere have temperatures and
humidities such that the straight line connecting the
two points representing the two streams of air on a
psychrometric shart intersects the saturation line,
.because the formation of dew and frost occurs between
these two points. In order to prevent the formation
of dew and frost, proposals have hitherto been made to
mount a preheater H, as shown in Fig. 3, in the air
supply passage to be located in a position upstream of
the heat and moisture transferring device 3, so as to
preheat the outdoor air OA as shown in a solid line
in Figs. 4 and 5 and convert the same into preheated
outdoor air OA' which is caused to pass through the
transferring device 3, in which the preheated outdoor
air OA' is further heated by the heat recovered ~rom
the return air RA from the heated space, so that the
air will be introduced into the space as supply air SA.
However, the use of the preheater H has disadvantages in
that, since it consumes eleçtricity, gas or other heating
energy, the running cost is increased and control of .
operation becomes troublesome. An added disadvantage
is that overall cost of production of the system is
increased.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention
is to provide a heat and moisture trans~erring system
, ,
8~
1 capable of preventing the formation of dew and frost on
the surfaces of the heat and moisture transferring
device, without requiring to use additional heating
energy.
Another obJect of the present invention is
to provide a heat and moisture transferring system
adapted to effect transfer of heat and moisture between
a stream of air supplied to an air-conditioned space and
a stream of air returned from the air-conditioned space,
wherein the outdoor air and the return air are preheated
and precooled respectively by effecting heat exhcange
therebetween through the agency of a heat transmitting
medium before being passed through the heat and moisture
transferring device, thereby preventing the formation .
15 of dew and frost on the surfaces of the heat and :~
moisture transferring device.
Another object of the invention is to provide
a heat and moisture transferring system comprising a
heat transmitting system inGluding a heat exchanger
located in the air supply passage, a heat exchanger
located in the air exhaust passage, and a conduit for
interconnecting the two heat exchangers to form a
closed circuit, so that the heat transmitting system
can effect preheating and precooling of the outdoor air
25 and the return air respectively. ~:
Another ob~ect of the invention is to provide .
a heat and moisture transferring system which is pro- :.
vided with a double heat transmitting system so as to
increase the heat recovery efficiency as compared with
the heat and moisture transferring system using a
.
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~IL078~3Z0
- l single heat transmitting system.
A still another ob;ect of the invention is to
provide a heat and moisture transferring system wherein
a non-evaporative liquid is used as a heat transmitting
medium circulated through the heat transmitting system
whereby the heat transmitting system need not have a
structure which can withstand high pressure and the
construction of the system can be simplified.
A still another object of the invention is to
provide a heat and moisture transferring system wherein
a condensable gas which undergoes a change in phase when
it effects exchange of heat is used as a heat transmitting
medium circulated through the heat transmitting system,
whereby latent heat of the heat transmitting medium can
be utilized to increase the heat recovery efficiency.
Still another object of the invention is to
provide a heat and moisture transferring system wherein
the closed clrcuit of the heat transmitting system is
formed as a gravity circulation circuit whereby the
heat transmitting medium circulated through the closed
circuit can be made to flow by gravity without requiring
the use of power.
A further ob;ect of the invention is to provide
a heat and moisture transferring system wherein the
closed circuit is provided with means for forcedly
circulating the heat transmitting medium therethrough
whereby the heat exchangers can be arranged in any
positions as desired without being subJected to any
limitation as to their vertical relative positions.
A still further ob~ect of the invention is to
~. .
~ 6 --
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~0~8Z~
provide a heat and molsture transferrlng system ~hereln
the heat transmitting system is composed of heat pipes
wereby the construction of the system can be simplified
and the heat transmitting medium can be made to flow ~ .
through the heat transmitting system without requiring ~
the use of power. :
A still further ob~ect of the invention is to . ~ .
provide a heat and moisture transferring system wherein
an on-off valve is mounted in the closed circuit so that `
. . .
a condensable gas can be circulated through the closed :
clrcuit only when it is necessary to do so, particularly
when the system is used in a heating mode.
A still further ob;ect of the invention is to .
provide a heat and moisture transferring system wherein
means is provided to return, for recirculation, a ~ .
portion of the return air to the space to be heated,
without being exhausted to the atmosphere as exhaust
air in initial stage of starting of operation of the ' :
system in a heating mode in which the temperature of the :. :
return air is not very high.
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Fig. 6 and Flg. 7 ea~h show an embodiment of
the present invention. Referring to Fig. 6, there is
shown a heat and moisture transferring system provided
with a rotary type heat and moisture transferring
. device 3 and comprising an air supply passage 1, and an
air exhaust passage 2 disposed below the air supply
passage 1, the two air passages 1 and 2 being partitioned
by a partition wall 11 as shown in Fig. 12. The rotary
type heat and moisture transferring device 3 is mounted ~-
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,
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~78~2~ ~
1 in airtight fashion and located across the two air
passages 1 and 2. The heat and moisture transferring
system further comprises a heat transmitting system 5
including air heat exchangers 18 and 19 interconnected
to form a closed circuit for a heat transmitting medium
to be circulated therethrough between the two heat
exchangers 18 and 19.
The construction of the heat and moisture
transferring device 3 will be described in detail. As
shown in Fig. 1, the device 3 comprises a rotary type
heat and moisture transferrer matrix 4 rotatably mounted
across the two air passages 1 and 2, a motor 7 for
rotating the transferrer matrix ~ at a low rotational
speed, e.g. 10 r.p.m., and a controller 8 for controlling
the rotation of the motor 7. The heat and moisture
transferrer matrix 4 comprises a disk-shaped air
permeable body 6 rotatably supported by a shaft, not
shown, and mounted within a panel casing 4c in such a
manner that the opposite ends thereof face the respec-
tive openings formed in the panel casing 4c. A parti-
tion packing 10 transversely extending along the central
portion o~ the air permeable body 6 supports the device
3 such that the lower portion of the air permeable body
6 is located in the air exhaust passage 2 and the upper
portion thereof is located in the air supply passage 1
as shown in Fig. 6.
Referring to Fig. 1 again, the air permeable
body 6 is connected to the motor through a belt 9
trained over the outer periphery of the body 6. Thus,
any arbitrarily selected portion of the disk-shaped air
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~t7~8~0
1 permeable body 6 is disposed in the air supply passage 1
during one half rotation of the body 6 and ln the air
exhaust passage 2 during the other half rotation thereof.
The air permeable body 6 is formed of a sheet
material having heat conductivity and moisture absorpti-
vity, e.g. asbestos paper, and constructed in a manner
to have a honeycomb structure comprising a multitude of
air flow passages oriented axially of the air permeable
body 6. The air permeable body 6 may, for exampleg be
readily formed by winding, in roll form, a sheet of
asbestos paper consisting of a plane member and a
corrugated member both impregnated with a moisture
absorbing agent, e.g. lithium chloride. -
The rotary type heat and moisture transferring
device 3 constructed as aforementioned is mounted in
airtight fashion and located across the two air passages
1 and 2, as shown in Fig. 6. The downstream end of the
air supply passage 1 opens in a room 14 through a heat
exchanger 12 Or an air conditloner of the heat pump type
and a supply fan 13, and the upstream end of the exhaust
air passage 2 opens in the room 14 through a filter 15.
The upstream end of the air supply passage 1 opens in
the atmosphere through a filter 16 and the downstr-eam
end of the air exhaust passage 2 opens in the atmosphere
through an exhaust fan 17.
The motor 7 is controlled by the operation
controller 8 which comprises a relay circuit in which a
timer, a relay and other control equipment are mounted.
Thus the controller 8 may have its operation ad~usted
manually so that the motor 7 can be switched readily
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1 from continuous rotation to a full stop or intermittent
rotation as desired.
The construction of the heat transmitting
system 5 will now be described. As aforesaid, the air
heat exchangers 18 and 19 are mounted in the air supply
passage 1 and the air exhaust passage 2 respectively
in a manner to be located on the upstream side of the
heat and moisture transferring device 3, so that heat
exchange can be effected between the heat transmitting
medium in the heat exchanger and the outdoor air OA
introduced into the system from the atmosphere and -
between the heat transmitting medium and the return air
RA from the heated room. More specifically, the heat
exchanger 18 is disposed in a position higher than that
of the other exchanger 19. The two heat exchangers 18
and 19 are interconnected at upper ends thereof by a
piping 20 and at lower ends thereof by a piping 21 to
form a closed circuit in which a suitable quantity of
the heat transmitting medium is charged. The numeral
22 designates a drain pan located below the heat
exchanger 19.
The heat transmitting system 5 is rendered
operative only when the room 14 is to be heated. In
this case, the heat exchanger 1~ located in the air
supply passage 1 can be made to function as a radiator
for warming the outdoor air OA introduced into the
system, while the heat exchanger 19 located in the air
exhaust passage 2 can be made to function as a heat
receiver for absorbing heat from the return air RA
from the heated room 14.
78~
1 More specifically, if the heat transmitt~ng
medium in the closed circuit is circulated in the
direction of solid line arrows as shown in ~ig. 6, then
the heat transmitting medium has its temperature raised
by effecting heat exchange with the return air R~
immediately before the latter flows into the heat and
moisture transferring device 3, and flows through the
piping 20 into the heat exchaner 18 where the warmed
heat transmitting medium effects heat exchange with the
outdoor air OA immediately before the latter is intro~
duced into the heat and moisture transferring device 3,
so that the outdoor air OA is warmed while the heat
transmitting medium is cooled. By effecting the afore-
mentioned heat exchanging operation cyclically, the
outdoor air OA is preheated and becomes preheated
outdoor air 0~' immediately before being introduced
into the heat and moisture transferring device 3.
A condensable gas, e.g. chlorodifluoromethane
(R-22), or non-evaporative, non-freezing liquid, e.g.
a solution of calcium chloride, may be used as the heat
transmitting medium circulated through the heat trans-
mitting system 5 However, when a non-freezing liquid
is used, it is impossible to cause the liquid to flow
in gravity circulation through the closed circuit, so
that it becomes necessary to use a pump 23 for ~orcedly
circulating the medium. On the other hand, when a
condensable gas, e.g. dichlorodifluoromethane (R-12) or
chlorodifluoromethane (R-22), is used, it will be
evident that the heat exchanger 19 can be made to function
as an evaporator and the heat exchanger 18 can be made
.
- 12 -
~ ~t7~
1 to functlon as a condenser by arranging the air passage
of lower air temperature or the air supply passage 1
at a higher level than the air passage of a higher air
temperature or the exhaust alr passage 2 to enable
the heat exchanger 18 to be located at a higher level
than the heat exchanger 19. By this arrangement, it is
possible to provide a circulation circuit suitable ~or
a condensable gas which circulates in gravity circulation
by changing its phase during circulation. It will be
appreciated that the heat transmitting system 5 Or this
form does not need any power for circulating the heat
transmitting medium therethrough.
Additionally, if a non-evaporative liquid is used
as the heat transmitting medium, the heat t~ansmitting
system 5 need not have a structure which can withstand
high pressure. This enables the construction of the
system to be simplified. The use Or a condensable gas
as the heat transmitting medium offers the advantage
Or requiring the use of no power for circulating the
medium as aforesaid. Moreover, since the use of a
condensable gas makes it possible to utilize latent heat,
the dif~erence between the temperature at which the
medium condenses and the temperature at which the mediumm
evaporates is small. This ofrers an advantage in that
the heat recovery efriciency can be increased by increas-
ing the difference between the temperature o~ return
air RA and the evaporating temperature of the medium -,
and the dirference between the temperature Or outdoor
alr OA and the condensing temperature of the medium.
- 30 It ls to be understood that when a condensable gas is
~ - 13 -
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l used as the heat transmitting medium circulated through
the heat transmitting system 5, the circulation of the
gas can be effected not only in gravity circulation as
illustrated in Fig. 6 but also in forced circulation -
wherein a pump or compressor is used. If the circulation
of the condensable medium is effected by khe latter
system, no limits are set on the relative positions of
the two heat exchangers 18 and 19, so that this offers
the advantage of being able to design the arrangement
of the air supply passage l and the air exhaust passage
2 as desired.
The operation of the heat and moisture trans-
ferring system shown in Flg. 6 will be described with
reference to the case in which R-22 is charged in the
heat transmitting system 5 and circulated in gravity
circulation therethrough. When the room 14 is to be
heated in the wintertime, the air conditioner is operated
in a heating mode so that the supply air SA is heated
by the heat exchanger 12 which functions as a condenser.
The heat and moisture transferrer matrix 4 of the heat
and moisture transferring device 3 is rotated at a
predetermined number of revolutions. The return air RA
of high temperature and high moisture content from the
heated room 14 is filtered by the filter 15 and brought
i.nto contact with the heat exchanger l9. The return
air RA effects heat exchange ~ith the refrigerant R-22
in the heat exchanger l9, with the result that the
former is cooled and has its moisture content reduced,
becoming precooled return air RA~. Since the temperature
of the refrigerant is lower than the dew point of the
- 14 -
1~7~ 0
1 return air RA, the moisture content of the return air RA
is reduced. The precooled return air RA' flows into the
half portion of the heat and moisture transferrer matrix
4 disposed in the air exhaust passage 2, where the
moisture and heat in the precooled return air RA' are
absorbed by the air permeable body 6. Thereafter the
air is exhausted as exhaust air EA to the atmosphere.
Meanwhile the refrigerant R-22 in the heat exchanger 19
is evaporated by the heat of the return air RA and flows
in a gaseous state into the heat exchanger 18. The
portion of the air permeable body 6 of the heat and . .
moisture transferrer matrix 4, which has absorbed heat
and moisture from the return air, rotates and moves ~.-.
into the air supply passage 1.
15Outdoor air OA of low temperature and low
moisture content is filtered by the filter 16 and
effects heat exchange with the refrigerant ~-22 in the
gaseous state in the heat exchanger 18, with the result
that the outdoor air OA is heated and becomes preheated
outdoor air OA'. The preheated outdoor air OA' ~lows
through the half portion of the heat and moisture trans-
ferrer matrix 4 which is disposed in the air supply
passage 1, so that it is heated and has its moisture ~.
content increased by the air permeable body 6. There-
after the outdoor air OA is heated to a predetermined
temperature in the heat exchanger 12 before being deli~-
ered to the room 14. Meanwhile the refrigerant in the
gaseous state in the heat exchanger 18 is condensed and : -
and changes to a liquid state, and the refrigerant in
the liquid state flow downwardly by its own weight into
- 15 - ~ ~
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978~ Q
1 the heat exchanger 19 which is disposed at a lower level
than the heat exchanger 18. The portion of the air
permeable body 6 from which heat and moisture have been
absorbed by the outdoor air OA rotates into the exhaust
air passage 2. The aforesaid cycle of operation is
repeated so that the heat and moisture in the return
air are continuously transferred to the outdoor alr. The
amount of precooling and preheating the return air and
the outdoor air respectively ~ill be described later.
When a cooling operation is performed in the
summertime, the air conditioner is operated in a cooling
mode so that the heat exchanger 12 functions as an
evaporator and cools the supply air SA. The heat and
moisture transferrer matrix 4 of the heat and moisture
transferring device 3 is rotated at a predetermined
number of revolutions. In this case, the outdoor air
is higher in temperature than the return air, so that
no gravity circulation of the refrigerant takes place
in the heat transmitting system 5. Thus the heat trans-
mitting system 5 is rendered inoperative and the transferof heat between the return air and the outdoor air
through the agency of the refrigerant does not take place.
However, since the heat and moisture transferrer matrix
4 of the heat and moisture transferring device 3 rotates,
the heat and moisture in the outdoor air of high
temperature and high moisture content are transferred
to the return air through the heat and moisture trans-
ferring device 3. That is, the outdoor air of high
temperature and high moisture content is cooled and
has its moisture content reduced by the return air of
- 16 -
~07~ Z~I
1 relatively low temperature and low moisture content,
and then cooled to a predetermined temperature by the -
~eat exchanger 12 before being delivered to the room 14.
In this case, under general temperature and humidity
conditions of sapce cooling, the straight line connecting
the points representing the temperatures and humidities -
of the outdoor air OA and the return air RA in a psychro-
metric chart does not intersect the saturation line of
relative humidity 100%, so that no dew formation occurs
in the heat and moisture transferring device 3. Thus no
trouble occurs even if the heat transmitting sys~em 5 is
rendered inoperative as aforesaid.
There is no need to heat or cool outdoor air
in the seasons between summer and winter, so that the
air conditioner has only to perform a ventilating
operation. ~herefore, it is not necessary to rotate
the heat and moisture transferrer matrix 4 of the heat
and moisture transferring device 3. However, in case
the heat and moisture transferring device 3 is shut -
down, dew formation on the surfaces of the air permeable
body 6 or other trouble may occur. Therefore, it is
desirable that the motor operation controller 8 be
actuated, so that the heat and moisture transferrer
matrix 4 will be rotated intermittently for several
minutes at intervals of 30 to 60 minutes, at a rota-
tional speed of 10 r.p.m. or less, for example. This
eliminates the trouble of effluence of the moisture
absorbing agent due to the formation of dew therein
and obturation of the air flow passages with dust in the
heat and moisture transferrer matrix 4.
.
- 17 -
1~715 13ZO
1 The recovery of` heat that is effected when a
heat and moisture transferring operation is per~ormed in
the wintertime as aforesaid will be further discussed.
For example, when the heat and moisture transferring
device 3 alone is used in places of lntense cold, the
moisture in the return air RA from which heat is
recovered will cause the formation of dew or frost in
the heat and moisture transferring device 3 and troubIe
will result, if the return air RA has an abnormally
0 high moisture content and the outdoor air OA has an
extremely low temperature.
In the present invention, the heat transmit
ting system 5 including the heat exchangers 18 and 19
are used in combination with the heat and moisture
transferring device 3 as aforesaid. Thus, by designing
the heat and moisture transferring device 3 and the
heat exchangers 18 and 19 in a manner to have suitable
heat exchanging capacities, the formation of dew and
frost can be prevented.
~ore specifically, the heat and moisture
transferring device 3 and the heat exchangers 18 and
19 should be designed in such a manner that the straight
line connecting the points representing the temperatures
and humidities of precooled return air RA' obtained by
precooling return air RA from the room 14 by the heat
exchanger 19 and of preheated outdoor air OA' obtained
by preheating outdoor air OA by the heat exchanger 18
lies inwardly of the saturation line as shown in Fig. 8.
This enables dew and frost formation to be prevented.
This ls one of the important features of the invention.
- 18 -
- ~ILC;788~(J
1 This feature will be described in detail with
reference to Figs. 6, 8 and 9. Assume that the outdoor
air OA has a temperature -20C and a humi.dity 100% and
the return air RA has a temperature 20C and a humidity
75%. Then it will be seen that the straight line
connecting the points representing the temperatures and
humidities of the preheated outdoor air OA' (passed
through the heat exchanger 18) having a temperature -6C
and a humidity 35% and of the precooled return air RA'
(passed through the heat exchanger 19) having a tempera-
ture 13C and a humidity 90% on the psychrometric chart
in Fig. 8 does not intersect the saturation line of
relative humidity 100%n That is, by designing the heat . .
exchanger 19 functioning as an evaporator in such a
15 manner that its evaporating temperature (Tc) becomes .
higher than 0C, the return air RA of 20C beco~es
precooled return air RA' of 13C which is cooled to a
temperature range higher than the evaporating tempera- .
ture (Tc), and the outdoor air OA of -20C is heated
and changed into the preheated outdoor air OA' of -6C
by the heat exchanger 18 which functions as a condenser
of a condensing temperature which is substantially
equal to the evaporating temperature (Tc). Meanwhile the
precooled return air RA' of 13C is further cooled at
the heat and moisture transferring device 3 and changed
into exhaust air EA of -1C which is exhausted to the
atmosphere, and the preheated outdoor air OA' of -6C is :
further heated at the heat and moisture transferring
device 3 and changed back into supply air SA of 8C which
is introduced into the room 1
- 19 -
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3L0~8~3Z(~
1 Thus the return air RA of 20C is changed into
the exhaust air EA of -1C, and the heat difference
between the return air RA and the exhaust air EA is
recovered by the system according to the invention.
The recovered heat is used for heating the outdoor air
of -20C and changing the same into the supply air SA of
8C for introduction into the room 14 to be heated.
It will be apparent that the system according to the
invention has a very high efficiency in recovering and
transferring heat from one air stream to the other air
stream.
The state of air passing through the heat and
moisture transferring device 3 at this time will be
further discussed. It will be seen that the straight
line connecting the points representing the precooled
return air RA', supply air SA, exhaust air EA and;pre-
heated outdoor air OA t in a psychrometric chart does not
intersect the saturation line as shown in Fig. 8.
Accordingly, it will be apparent that, if the
2~ heat and moisture transferring device 3 is used in
combination wlth the heat transmitting system 5 includ-
ing the heat exchangers 18 and 19 and if the heat exchan-
gers 18 and 19 are each designed in a manner to have a
suitable heat exchanging capacity, then it is possible to
enable the heat and ~oisture transferring device 3 to
function normally without dew and frost being formed on
the surfaces of the heat and moisture transferrer matrix
4, even if the system according to the invention operates
under conditions such that the return air RA has an
- 20 -
71!382~
inordinately high humidity while the outdoor air OA has an
extremely low temperature-conditions under which the formation
of dew and frost tends to occur.
A comparison of the heat and moisture transferring
system according to the invention wherein the heat transmit-
ting system 5 is combined with the heat and moisture trans-
ferring device 3 with a conventional system wherein the out-
door air entering the heat and moisture transferring device 3
is heated by an electric heater, gas burner or other separate
heating source shows that the use of the heat transmitting
system S enables to achieve a higher heat recovery efficiency.
More specifically, the total heat recovery effi-
ciency n of the heat and moisture transferring devicë 3 and
the heat transmitting system 5 can be expressed by the ollow-
ing formula:
il +Q i2
~ i4where ~ il: Heat gain through heat transmi~ing system 5.
~ i2: Heat gain through heat and moisture trans-
ferring device 3.
i4: The difference in enthalpy between return
air RA and outdoor air OA. - .
If the values of~ il and~ i4 are calculated in the
psychrometric chart shown in Fig. 8,h il/~ i4 = 0~2.
Suppose that the heat and moisture transferring
device 3 is designed to operate at 70~ of heat recovery effi-
ciency. The heat recovery efficiency of the heat and moisture
transferring device 3 can be expressed as follows:
The difference in enthalPY between OA' and SA
The difference in enthalpy between OA' and RA'
The difference in enthalpy between EA and RA'
The difference in enthalpy between OAI and RA~
- 21 -
. , ' .' ' ~ ,
~i2
~i4 - 2 ~il 0'7
Thus~ Qi2 = 0 7 ( Qi4 2 ~
The total heat recovery efficiency can be calculated
as follows;
~i 1 + Qi2
n= ~i4
~ 0.7 ( ~ 2 Ail)
= ~i4
= 0.2 + 0.7 (1 - 2 x 0.2)
= 0.62
On the other hand, in a conventional system of the
external heating type r~herein the heat gain ~ih is obtained by
means of a separate heat source, such as an electric heater or
gas burner, the total heat recovery efficiency n ~ can be cal-
culated as follows as shown in the psychrometric chart of
~ig. 5:
~i 0 7 ( bi - ai )
i4 - = 0.7 x (1- 0.2) = 0.56
Also, if ~il/ ai4 = ~ = 0.3 un~er conditions
of different temperature and humidity other than those shown
in Fig. 8 and Fig. 5, n = 0~58 and n ' = 0.49 are ca~culated.
The total heat recovery efficiency is plotted in
Fig. 9 against the preheating ratio ~il/ ai4 or ~ which
is varied by changing the conditions of temperatures and
humidity with respect to the system according to the invention ,
wherein preheating of outdoor air is effected by means of the
heat transmitting system and a system of the prior art using
an external heat source for preheating outdoor air. In Fig. 9,
it will be clearly seen that n > ~ ~ . This shows that the
system according to the invention is higher in total
heat recovery efficiency than the system of the prior art
~ .
- 22 - -
~, . .
7882(~
'
1 using a separate heat source, such as an electric,heater
or gas burner. Moreover, the present invention offers
an additional advanta~e in that the energy ~or pre-
heatlng outdoor air can be done without.
Example
Experiments were conducted on the heat and
moisture trans~erring system according to the invention
to determine whether the formation of dew and/or frost
occurs under varying cond1tions.-- The conditions under
which the experiments were conducted are as follows:
''~' ' "
Table 1
. :,
Conditions Conditions No. of Rows of No. of Rows
of Outdoor of Return Heat Exchanging Tubes of Heat Ex-
Air OA Air RA in the Heat Exchanger changer 18
, on OA Side
. .
_30C 20C 13 ~~ 6
- (1) RH: }00~ RH: 75% (286 mm)(132 mm) '~
.
- -20C 20~C 4 4
(2) RH: 100~ RH: 75~ (38 mm) (88 mm)
. .
-20C 15C 5 3
(3) RH: 100% RH: 75% tllO mm)(66 mm)
Note: In the above table, RH stands for relative
humidity and the numbers in the brackets refer to
the front-to-rear dimension Or the heàt exchangers.
Other conditions are as rOllows:
Face velocity Or Heat Exchangers: 3 m/s
Rate o~ Air Flow throu~h Heat Exchan~ers: 1200 m3/h
Face area o~ Heat Exchan~ers: 0.11 m
- 23 - ,
~,~ ... . .
~L07~3!3Z~)
1 Effective Length of Heat Exchanging Tubes: 510 mm
Diameter of Heat Exchanging Tubes: 95 mm
Pitch of Fins of Heat Exchangers: 3 mm
As the results of the experiments conducted
under the aforesaid conditions, it has been ascertained
that it is possible to prevent the formation of dew and
frost when the heat and moisture transferring system
according to the invention is permitted to operate
under the aforesaid conditions, provided that the heat
transmitting system 5 is designed such that the heat
exchangers 18 and 19 each have the rows of the numbers
set forth in the table.
Experiments were further conducted without
using the heat exchangers 18 and 19 when the return air
RA had a temperature 20C and a humidity 75%. When
the outdoor air OA has a humidity 100% and a tempera-
ture below 5C e.g. 0C for example, the straight line
connecting the point of the return air RA of a tempera-
ture 20C and a humidity 75% to the point of the outdoor
air OA of a temperature 0C and a humidity 100~ was
found to intersect the saturation line of relative
humidity 100%. Thus the elimination of the heat
exchangers 18 and 19 under the aforesaid conditions
caused the formation of dew and frost to occur in the
heat and moisture transferring device 3, thereby making
it impossible to continue the operation of the heat and
moisture transferring system.
From the foregoing description, it will be
apparent that the heat and moisture transferring system
according to the invention enables heat recovery to be
,. . . : ,. -: .
~ID7 !3~
effected with a high degree of efficiency without causing the
formation of dew and/or frost in the heat and moisture trans-
ferring device 3. Other embodiments of the invention will now
be described with reference to Figs. 7, 10 and 11.
Fig. 7 shows another embodiment wherein the heat
and moisture transferring device 3 comprises th~ known static
heat and moisture transferrer matrix 4 shown in Fig. 2, and
wherein the two heat exchangers 18 and 19 are formed as a
unitary heat exchanger of a natural circulation type. The
unitary heat exchanger comprises a plurality of heat exchanging
tubes or heat pipes, each including a hollow straight tube
having closed opposite ends and a multiplicity of fins pro-
jecting from the outer periphery thereof, and filled with a
suitable refrigerant. The heat pipes may be arranged ver-
tically or aslant and located across the air supply passage 1
and air exhaust passage 2 disposed in parallel relationship.
The heat pipes are of a known type, in which
refrigerant will be naturally circulated therein. More
specifically, in each heat pipe, the refrigerant in a liquid
state disposed in the lower portion thereof is vaporized into
a gaseous state when heated by return aix RA of high tempera-
ture and flows upwardly into the upper portion where the
gaseous-refrigerant gives off heat-into the outdoor air OA
of low temperature and changes back into a liquid state.
The liquid refrigerant flows back to the original
- 25 -
~ '
;~
:~713~
lower portion, thus completing a cycle of circulation. The
heat pipes can also be used in case where the air supply
passage 1 and air exhaust passage 2 are disposed horizontally.
In such a case, the heat pipes must be arrange~ horizontally.
In order to establish a natural circulation of the refrigerant
in the heat pipes disposed horizontally, each heat pipe should
be provided with a layer of porous material having a mul-
titude of fine passages on its inner surface, so that the
interior of each heat pipe is aivided into two regions,
one providing passages for liquid refrigerant and the other
providing passages for gas refrigerant. By this arrangement,
smooth circulation of the refrigerant can be established in
each heat pipe, even if the heat pipe is disposed horizontally.
The heat and moisture transferring device 3
is of the type which comprises the known static type
heat and moisture transferrer matrix 4 shown and
described with reference to Fig. 2. This type,of
heat and moisture transferring device 3 is advantageous
because it is simple in construction and requires no
power source to operate the same.
The heat and moistuxe transferring system
constructed as aformentioned offers the advantage of
-requiring no power at all to operate the same. In
addition, by arranging the heat transmitting system
horizontally, it is possible to render the same opera-
tive in the summertime as well as in the wintertime.
Particularly, this embodiment of the invention offers
an advantage in that the formation of dew in excessive
quantities in the heat and moisture transferrer matrix 4
- 26 -
~ ~ .
- : . , ~ - - .. ., . .. . , , :
~788~
1 by outdoor air OA Or high temperature and high humldity
can be prevented.
Fig. 10 shows still another embodiment wherein
an on-off valve 24 is mounted in the closed circuit Or
the heat transmitting system 5 in which a heat transmit-
ting medium is circulated in gravity circulation accom-
panied by a change in phase or in forced circulation.
When the system is not in use, the on-orf valve 24 is
closed so as to completely stop the circulation of the
heat-transmittlng medium. Thus the pro~ision of the
on-off valve 24 prevents unnecessary operation of the
system by stopping the circulation of the heat trans-
mitting medium, thereby offering the advantage of
increasing the heat recovery efficiency of khe heat and
moisture transferring system.
Another feature of the embodiment shown ln
~ig. 10 is that a bypass damper 25 is mounted in a
portion of the partition wall 11, separating the air
supply passage 1 from the air exhaust passage 2. The bypass
damper 25 normally forms a part of the partition wall 11,
buk, when in operation, permits a portion of the precooled
return air RA' to flow in bypass current from the air exhaust~
passage 2 to a portion of the air supply passage 1 which
is disposed aownstream of the heat and moisture transferring
device 3.
The provision of the bypass damper 25 offers the
following advantages. In initial stages of the operation
of the air conditioner in a heating mode,
. 30
~ ' ~, .
:'. , : ' , ' ' . ~ . :: .
~C~78~
1 the space is not heated satisfactorily and the tempera-
ture of return air RA is so low that the temperature of
the heat transmitting medium in the heat exchanger 18
is not sufficiently high to permit the heat and moisture
transferrer matrix 4 to function satisfactorily. When
this is the case~ the heat exchanger 18 is unable to
satisfactorily preheat outdoor air OA Or low temperature.
When the aforesaid abnormal cond~tion exists, the bypass
dampter 25, is actuated to allow a portion of the pre-
cooled return air RA' to flow in bypass current and jointhe return air RA which effects heat exchange with the
heat transmitting medium at the heat exchanger 19 can be
increased in volume without materially increasing the
volume of exhaust air EA, thereby making it possible to
sufficiently raise the temper~ture of the heat trans-
mitting medium. Thus the outdoor air OA can be suf-
ficiently preheated by the heat exchanger^lB so that the
formation of dew and frost in the heat and moisture trans-
ferring device 3 can be prevented, even when the abnormal
operating condition exists.
Fig. 11 shows still another embodiment in which
the heat exchangers 18 and 19 are each divided into two
sections or heat exchangers 18 and 19 which function as -
heat exchangers of the lower temperature sidç and heat
exchangers 18' and 19' which function as heat exchangers
of the higher temperature side when the air conditioner
operates in a heating mode. Hea~ exchanging tubes of
,~
,
- ~8 -
~ ' ' , .. .
1~7~38Z(3
1 the heat exchangers 18 and 19 are interconnected at
upper ends thereof by a piping 20, and at lower ends
thereof by a piping 21. Heat exchangin~ tubes of the
heat exchangers 18' and 19' are interconnected at upper
ends thereof by a piping 20l and at lower ends thereof
by a piping 21'. Thus the heat transmltting system of
this embodiment is formed as a double heat exchanging
systems, so that the heat recovery efficiency can be
increased as compared with the hea~ and moisture trans- -
ferring system comprising a heat transmitting system
formed as a single heat exchanging system.
The numerals 23, 23' and 24, 2l1' designate
pressure delivery devices i.g. pumps or compressors
and on-off valves mounted in the piping 21, 21'
respectively.
When the heat and moisture transferring system
according to the invention is used for effectin~ venti-
lation of a freezing chamber, the system has effects if
outdoor air OA has a relatively high temperature. In
2b this case, if the system is operated in a condition in
which the return air RA, exhaust air EA, outdoor air
OA and supply air SA of the embodiment shown in Fig. 6
are replaced by outdoor air OA, supply air SA, return
air RA and exhaust air EA respectively, then it will be
possible to cool the outdoor air of high temperature into
cooled air for effecting ventilation.
From the foregoing descriptiong it will be
appreciated that the heat and moisture transferring
system according to the invention comprises, in combina-
tion, an heat and mois~ure transferring device 3 which
29 -
.
.
~7~3Z~
1 utilizes not only sensible heat but also latent heat,
and a heat transmitting system 5 including a closed
circuit interconnecting two heat exchangers. The heat
exchangers are each designed to have a suitable heat
exchanging capacity as shown in a psychrometric chart
as aforesaid, so that the system permits heat to be
removed ~rom return air from the heated space and to be
imparted to fresh outdoor air supplied from the atmos-
phere. In this way, ventilation of the cooled or heated
space can be effected satisfactorily by utilizing the
heat removed from the return air from the cooled or
heated space. The provision of the two heat exchangers
enables the heat and moisture transferring system to
function with a high degree of efficiency without the
formation of dew and frost even in the wintertime when
cold is intense. Thus, the heat and moisture transferring
system according to the invention is characterized by
increased range of low temperatures in which it can
have application.
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