Abstrict A process and apparatus for open cycle desiccant cooling wherein
the process stream and regeneration stream are divided into a plurality
of radial stream segments by non-parallel partitions forming unequal
face segments in the desiccant wheel and the heat wheel for the
same stream segment. The unequal face segments in the desiccant
wheel and the heat wheel provide differing temperature profiles
at the face of each wheel and allow obtaining desired temperature
profiles for heat exchange and moisture adsorption. The process
of this invention results in reduction of the radial speed of the
heat wheel to less than 4 providing high effectiveness of the heat
wheel increasing the capacity and the COP of the system.
Claims We claim:
1. In a process for open cycle desiccant cooling of the type wherein
a process stream passes sequentially through a process stream arcuate
segment of a rotating desiccant wheel, a process stream arcuate
segment of an oppositely rotating heat wheel and an evaporative
cooler to the cooled space and a countercurrent regeneration stream
passes sequentially through an evaporative cooler, a regeneration
stream arcuate segment of said heat wheel and a regeneration stream
arcuate segment of said desiccant wheel, the improvement comprising;
dividing said process stream after passing through said desiccant
wheel into a plurality of different temperature arcuate process
stream segments, corresponding said arcuate process stream segments
having a different arcuate area at the outlet face of said desiccant
wheel and the inlet face of said heat wheel to provide a temperature
profile for improved effectiveness of said heat wheel.
2. In a process according to claim 1 wherein the arcuate area of
said process stream at said inlet face of said heat wheel is larger
than the arcuate area of said process stream at said outlet face
of said desiccant wheel.
3. In a process according to claim 1 wherein said heat wheel is
rotated at a nondimensional rotational speed of less than 4.
4. In a process according to claim 1 wherein high temperature process
stream segment(s) comprise arcuate angle fractions of said desiccant
wheel of about 0.1 to about 0.4 of the total arcuate angle of said
process stream passing through said desiccant wheel.
5. In a process according to claim 1 wherein said process stream
has a converging ratio of just over 1.0 to about 1.67 passing from
said outlet face of said desiccant wheel to said inlet face of said
heat wheel.
6. In a process according to claim 1 further comprising dividing
said regeneration stream after passing through said heat wheel into
a plurality of different temperature arcuate regeneration stream
segments, said arcuate regeneration stream segment having different
arcuate area at the outlet face of said heat wheel and the inlet
face of said desiccant wheel to provide utilization of a greater
amount of heat from said heat wheel in staged temperature profile
for said desiccant wheel.
7. In a process according to claim 6 wherein the highest temperature
said arcuate regeneration stream segment(s) is(are) further heated
by heat from a source exterior to said process.
8. In a process according to claim 7 wherein said arcuate regeneration
stream segment(s) further heated comprise arcuate angle fraction(s)
of said desiccant wheel of about 0.5 to about 0.67 of the total
arcuate angle of said regeneration stream passing through said desiccant
wheel.
9. In a process according to claim 6 wherein said regeneration
stream arcuate area at said inlet face of said desiccant wheel is
larger than said regeneration stream arcuate area at said outlet
face of said heat wheel.
10. In a process according to claim 9 wherein the lowest temperature
said arcuate regeneration stream segment(s) is(are) discharged from
said process.
11. In a process according to claim 6 wherein said regeneration
stream has a diverging ratio of just over 1 to about 2.5 passing
from said outlet face of said heat wheel to said inlet face of said
desiccant wheel.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus and process for improved
efficiency of a sensible heat exchanger wheel in an open cycle desiccant
cooling system. Diverging and converging partitions between the
desiccant wheel and heat wheel in an open cycle desiccant cooling
system provide unequal sized segments of the desiccant wheel and
heat wheel exposed to process and regeneration gas streams in a
manner which improves the efficiency of the heat wheel and allows
reduction in rotational speed of the heat wheel to obtain high cooling
efficiencies.
2. Description of Related Art
Rotary gas treating apparatus of a wide variety are known. U.S.
Pat. Nos. 4895580 and 5167679 teach gas adsorption and desorption
on regenerative rotary devices. Rotary dehumidifiers which are thermally
regenerable are taught by U.S. Pat. Nos. 4134743 and 4926618.
Rotary heat exchangers are taught by U.S. Pat. Nos. 4497361 and
5183098.
Open cycle desiccant cooling systems using rotary sensible heat
exchanger wheels and regenerable desiccant wheels are well known,
as exemplified by U.S. Pat. Nos. 3889742; 3774374; 4729774;
4887438; 4948392; 4594860; and 5170633. Staged heating of
only the regeneration stream using parallel partitions between the
heat wheel and the desiccant wheel forming equal sized segments
of the heat wheel and desiccant wheel is taught by U.S. Pat. Nos.
3889742 and 4948392. Parallel partitions in the regeneration
stream between the heat wheel and the desiccant wheel forming equal
size segments in these wheels and parallel partitions in the process
stream between the desiccant wheel and the heat wheel forming equal
size segments in these wheels to obtain stratified inlet temperature
to the heat wheel is taught by U.S. Pat. No. 4594860. Stratified
heat recovery in the process steam to effect profiling of temperatures
in the regeneration stream to obtain higher temperatures toward
the hotter zone of a desiccant bed is taught be U.S. Pat. No. 4729774.
The emphasis for increased performance of open cycle desiccant
cooling systems has focused on increasing the effectiveness of the
desiccant wheel, as exemplified by R. K. Collier, Jr., D. Novosel
and W. M. Worek, "Performance Analysis of Open-Cycle Desiccant
Cooling Systems", ASHRAE Transactions 1990 V. 96 Pt. 1 AT
90-19-2 (1990) and W. M. Worek, W. Zheng, W. A. Belding, D. Novosel
and W. D. Holeman, "Simulation of Advanced Gas-Fired Desiccant
Cooling Systems", ASHRAE In-91-4-2 pg. 609-614 (1991).
SUMMARY OF THE INVENTION
Conventional open cycle cooling systems comprise a desiccant wheel
and a heat wheel, which rotate in opposite directions, and an evaporative
cooler with a process stream passing sequentially through a portion
of the desiccant wheel, a portion of the heat wheel and an evaporative
cooler and a counter flowing regenerative stream passing sequentially
through an evaporative cooler, a portion of the heat wheel, and
a portion of the desiccant wheel. The process stream after being
dehumidified by the desiccant wheel, becomes warm and dry and is
cooled by passing through the heat wheel which concurrently heats
the regeneration stream for reactivation of the desiccant wheel.
At least a portion of the regeneration stream may be further heated
by an external source for passage through the desiccant wheel. The
open cycle solid desiccant cooling system may be operated in a ventilation
mode with at least a portion of the regeneration stream being outside
air or in the recirculation mode with the regeneration stream being
exclusively air from the cooled space.
The heat wheel is a critical element of the open cycle solid desiccant
cooling system since if the heat wheel has low effectiveness, the
system cooling capacity will be commensurately low, regardless of
how dry the process air is dried by the desiccant wheel. The cooling
capacity of a desiccant cooling system is basically controlled by
the effectiveness of the heat wheel. Further, the more effective
the heat wheel, a greater amount of heat will be recovered to heat
the regeneration stream. Thus, both the cooling capacity and the
coefficient of performance (COP) of the system are increased by
more effective operation of the heat wheel.
It is an object of this invention to provide an apparatus and process
for increasing the COP in an open cycle desiccant cooling system.
Another object of this invention is to provide an apparatus and
process for increasing the system capacity in an open cycle desiccant
cooling system.
Yet another object of this invention is to increase the effectiveness
of the heat wheel in an open cycle desiccant cooling system.
These and other objects and advantages of this invention are achieved
by non-parallel radial partitions in both the regeneration stream
and the process stream creating unequal arcuate segments in the
desiccant wheel and the heat wheel for each segment of the streams
formed by such non-parallel partitions. By the terminology "non-parallel"
as used in herein, it is meant that line segments parallel to the
axis of the wheels in adjacent partitions are non-parallel with
the adjacent partitions forming unequal cross sectional areas of
the space between them at opposite ends. Improvement in the effectiveness
of the heat wheel is further achieved by reducing the rotational
speed of the heat wheel to a value significantly less than presently
considered to be optimal.
Prior efforts to increase the efficiency of open cycle desiccant
cooling systems have focused upon improvement in the effectiveness
of the desiccant wheel. The present invention focuses on improvement
in the effectiveness of the heat wheel to obtain both increased
system capacity on increased COP.
The process of this invention for open cycle desiccant cooling
is of the type wherein a process stream passes sequentially through
a process stream arcuate segment of a rotating desiccant wheel,
a process stream arcuate segment of an oppositely rotating heat
wheel and an evaporative cooler to the cooled space and a countercurrent
regeneration stream passes sequentially through an evaporative cooler,
a regeneration stream arcuate segment of the heat wheel and a regeneration
stream arcuate segment of the desiccant wheel. The improvement of
this invention comprises dividing the process stream after passing
through the desiccant wheel into a plurality of different temperature
arcuate process stream segments, the total arcuate angle of the
process stream outlet face segments in the desiccant wheel being
greater than the total arcuate angle of the process stream inlet
face segments in the heat wheel. The ducting forming the process
stream is converging from the desiccant wheel to the heat wheel.
Corresponding arcuate process stream segments have a different arcuate
area at the outlet face of the desiccant wheel and the inlet face
of the heat wheel to provide a temperature profile for improved
effectiveness of the heat wheel. The process stream is divided into
a gradation of high to low temperature process streams, the high
temperature process stream(s) having a smaller face area than the
low temperature process stream(s) due to the non-linear temperature
change in the process stream at the outlet face of the desiccant
wheel. Likewise, the medium and high temperature portions of the
regeneration stream, after passing through the heat wheel, may be
divided into a plurality of different temperature arcuate regeneration
stream segments, the total arcuate angle of the medium and high
temperature outlet face segments in the heat wheel being less than
the total arcuate angle of the regeneration stream inlet face segments
in the desiccant wheel. The ducting forming the medium and high
temperature regeneration streams is diverging from the heat wheel
to the desiccant wheel.
The apparatus of this invention for open cycle desiccant cooling
is of the type having a rotating desiccant wheel, an oppositely
rotating heat wheel and ducting means capable of passing a process
stream sequentially through a process stream arcuate segment of
the desiccant wheel, a process stream arcuate segment of the heat
wheel and an evaporative cooler to a cooled space and capable of
passing a regeneration stream countercurrent to the process stream
sequentially through an evaporative cooler, a regeneration stream
arcuate segment of the heat wheel and a regeneration stream arcuate
segment of the desiccant wheel. The improvement of this invention
comprises the ducting means forming the process stream being converging
from the desiccant wheel to the heat wheel forming a plurality of
arcuate process stream outlet face segments at the outlet face of
the desiccant wheel and forming a plurality of arcuate process stream
inlet face segments at the inlet face of the heat wheel. Likewise,
the ducting means forming the medium and high temperature regeneration
stream may be diverging from the heat wheel to the desiccant wheel
forming a plurality of arcuate regeneration stream outlet face segments
at the outlet face of the heat wheel and forming a plurality of
arcuate regeneration stream inlet face segments at the inlet face
of the desiccant wheel.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other advantages of this invention will become evident
upon descriptions of specific preferred embodiments and reference
to the drawings, wherein:
FIG. 1 is a schematic top view of a portion of an open cycle desiccant
cooling system according to one embodiment of this invention;
FIG. 2 is a schematic showing of one face of the desiccant wheel
as shown in FIG. 1 by Section 2--2;
FIG. 3 is a schematic showing of one face of the heat wheel as
shown in FIG. 1 by Section 3--3; and
FIG. 4 is a perspective view of non-parallel radial partitions
which extend between the desiccant wheel and the heat wheel, according
to one preferred embodiment of this invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIG. 1 an open cycle desiccant cooling system according
to one embodiment of this invention is shown in a simplified schematic
form. Process stream input 37 passes to the process stream input
face of desiccant wheel 20 through desiccant wheel 20 drying the
process stream, and exits desiccant wheel 20 through the opposite
process stream output face of desiccant wheel 20. At the process
stream output face of desiccant wheel 20 low temperature process
stream face segment 21 and high temperature process stream face
segment 22 as best seen in FIG. 2 form low temperature process
stream segment 31 and high temperature process stream segment 32
respectively, defined by non-parallel radial partitions which extend
between desiccant wheel 20 and heat wheel 10 as shown in FIG. 4.
These process stream segments pass to the process stream input face
of heat wheel 10 with low temperature process stream segment 31
passing through low temperature process stream face segment 11 of
the process stream input face of heat wheel 10 and high temperature
process stream segment 32 passing through high temperature process
stream face segment 12 of the input face of heat wheel 10 as best
seen in FIG. 3. The total arcuate angle of low temperature process
stream face segment 21 and high temperature process stream face
segment 22 of the output face of desiccant wheel 20 is greater than
that of low temperature process stream face segment 11 and high
temperature process stream face segment 12 of the input face of
heat wheel 10 forming a converging process stream from desiccant
wheel 20 to heat wheel 10. The converging ratio is the ratio of
the total angle of the process stream outlet face segments 21 and
22 of the desiccant wheel to that of the process stream inlet face
segments 11 and 12 of the heat wheel. In system design, the converging
ratio between the face segment 22 and the face segment 12 and the
converging ratio between the face segment 21 and the face segment
11 are about equal. The converging ratio is suitable just over 1.0
to about 1.67 preferably about 1.15 to about 1.3. The entire process
stream is cooled passing through heat wheel 10 and humidified by
passing through process stream evaporative cooler 18 to form process
stream cool output 38. Heat wheel 10 and desiccant wheel 20 rotate
in opposite directions as shown by the arrows.
Regeneration stream input 39 passes through regeneration stream
evaporative cooler 19 to the regeneration stream input face of heat
wheel 10 through heat wheel 10 heating the regeneration stream,
and exits heat wheel 10 through the opposite regeneration stream
output face of heat wheel 10. At the regeneration stream output
face of heat wheel 10 high temperature regeneration face segment
13 medium temperature regeneration face segment 14 and low temperature
regeneration face segment 15 as best seen in FIG. 3 form high
temperature regeneration stream segment 33U, medium temperature
regeneration stream segment 34 and low temperature regeneration
stream scavenger segment 35 respectively, defined by non-parallel
partitions. Regeneration stream scavenger segment 35 may be discharged
from the system. Medium temperature regeneration stream segment
34 passes directly to regeneration stream input face of desiccant
wheel 20 and passes through medium temperature regeneration stream
face segment 24. High temperature regeneration stream segment 33U
passes through heating means 9 further heating this stream segment
to form heated high temperature regeneration stream segment 33H
which passes through heated high temperature regeneration stream
face segment 23 of the regeneration stream input face of desiccant
wheel 20. The total arcuate angle of high temperature regeneration
stream face segment 13 and medium temperature regeneration stream
face segment 14 of the output face of heat wheel 10 is less than
that of high temperature regeneration stream face segment 23 and
medium temperature face segment 24 of the input face of desiccant
wheel 20 forming a divergent regeneration stream from heat wheel
10 to desiccant wheel 20. The diverging ratio is the ratio of the
total angle of the high and medium temperature regeneration stream
outlet face segments 13 and 14 of the heat wheel 10 to that of regeneration
stream inlet face segments 23 and 24 of desiccant wheel 20. In system
design, the diverging ratio between face segment 13 and face segment
23 and the diverging ratio between face segment 14 and face segment
24 are about equal. The diverging ratio is suitably just over 1.0
to about 2.5 preferably about 1.5 to about 2.0. Passing through
desiccant wheel 20 the regeneration stream heats the regeneration
segments to regenerate the desiccant within that portion of desiccant
wheel 20 and pass from regeneration stream exhaust face of the wheel
as regeneration stream exhaust 40.
A purge stream may be passed through desiccant wheel 20 by passing
through purge stream inlet face segment 27 forming purge stream
36 which is passed back through desiccant wheel 20 through purge
stream outlet face segment 26 to cool these segments of desiccant
wheel 20 prior to entry of process stream 37.
Process stream input 37 may be from outside the cooled space to
operate the system in the ventilation mode or may be from inside
the cooled space to operate the system in the recirculation mode,
or may be any combination of these sources. The process stream is
dehumidified by passing through desiccant wheel 20 and the process
stream temperature upon passing from the outlet face of the desiccant
wheel has a profile which is a function of the arc segment of the
wheel through which it passed, with the highest temperature being
adjacent to the purging stream. The temperature profile is maintained
by partitions in the process stream between the desiccant wheel
and the heat wheel. In this invention, the arcuate temperature profile
of the process stream may be modified between the process stream
outlet face of the desiccant wheel and the process stream inlet
face of the heat wheel to obtain high effectiveness of the heat
wheel. As shown in FIG. 2 the process stream outlet face of desiccant
wheel 20 is divided into high temperature process stream face segment
22 and low temperature process stream face segment 21 while, as
shown in FIG. 3 the process stream inlet face of heat wheel 10
is divided into high temperature process stream face segment 12
and low temperature process stream face segment 11. The process
stream arcuate segments at the outlet face of the desiccant wheel
and the inlet face of the heat wheel are of unequal sizes which
may be adjusted to obtain high effectiveness of the heat wheel.
These unequal arcuate segments are formed by non-parallel radial
partitions between desiccant wheel 20 and heat wheel 10 resulting
in different process stream arcuate temperature profiles adjacent
each wheel. In this manner, the desired temperature profile for
high effectiveness of the heat wheel may be obtained. The ducting
for process stream input 37 is matched to the total arcuate segment
of the process stream through desiccant wheel 20 and for process
stream treated output 38 is matched to the total arcuate segment
of the process stream through heat wheel 10. While the figures show
two segments 31 and 32 of the process stream and corresponding two
segments in desiccant wheel 20 and heat wheel 10 it should be recognized
that any desired number of segments may be formed in a similar manner
to obtain the desired temperature profile, generally two to about
four segments being suitable. It is generally desired that the arcuate
segments of high temperature process stream 32 and low temperature
process stream 31 be reduced between the process stream outlet face
of desiccant wheel 20 and the process stream inlet face of heat
wheel 10. Since the total arcuate angle on the process side of the
desiccant wheel may be varied in different designs, the arcuate
segments of the process stream will be defined as arcuate angle
fractions of the total process stream input 37. The arcuate angle
fraction of high temperature process stream face segment 22 to the
total arcuate angle of process stream input 37 is suitably about
0.1 to about 0.4 preferably about 0.15 to about 0.25.
Regeneration stream input 39 is ambient air directed, countercurrent
to the process stream, through regeneration stream evaporative cooler
19 and through heat wheel 10 to exit through regeneration stream
arcuate outlet face segments of heat wheel 10 shown as 12 13 and
14 in FIG. 3. The regeneration stream is warmed by passing through
heat wheel 10 and the regeneration stream temperature upon passing
from the outlet face of the heat wheel has a profile which is a
function of the arc segment of the wheel through which it is passed,
with the highest temperature being adjacent the high temperature
process stream segment, as seen in FIG. 3. The temperature profile
in the regeneration stream is maintained by partitions in the regeneration
stream between the heat wheel and the desiccant wheel. In this invention,
the arcuate temperature profile of the regeneration stream may be
modified between the outlet face of the heat wheel and the inlet
face of the desiccant wheel. As shown in FIG. 3 the regeneration
stream outlet face of heat wheel 10 is divided into high temperature
regeneration stream outlet face segment 13 medium temperature regeneration
stream outlet face segment 14 and low temperature regeneration stream
outlet face segment 15 while, as shown in FIG. 2 the regeneration
stream inlet face of desiccant wheel 20 is divided into medium temperature
regeneration stream inlet face segment 24 and high temperature regeneration
stream inlet face segment 23. The regeneration stream arcuate segments
at the outlet face of the heat wheel and the inlet face of the regeneration
wheel are of unequal sizes which may be adjusted to obtain high
effectiveness of regeneration of the desiccant wheel. The portion
of the regeneration stream formed by low temperature regeneration
face segment 15 is regeneration stream scavenger segment 35 which
is discarded from the system, as shown in FIG. 1 thereby reducing
the heat input necessary to obtain the same regeneration temperature.
Medium temperature regeneration stream 34 formed by medium temperature
regeneration stream outlet face segment 24 is passed directly to
medium temperature regeneration stream inlet face segment of regeneration
wheel 20 as shown in the figures. High temperature regeneration
stream 33U, unheated by an external source, is passed through heating
means 9 providing heat from an external source, further heating
the stream segment to the desired temperature for heated high temperature
regeneration stream 33H which is passed through high temperature
regeneration stream inlet face segment 13 of desiccant wheel 20.
Thus, it is seen that the regeneration stream arcuate segments of
the outlet face of the heat wheel and the inlet face of the regeneration
wheel are of unequal sizes which may be adjusted to obtain desired
temperature profiles for high effectiveness of both the heat wheel
and regeneration of the desiccant wheel. These unequal arcuate segments
are formed by non-parallel partitions in the regeneration stream
between the outlet of heat wheel 10 and the inlet of desiccant wheel
20 resulting in different regeneration stream arcuate temperature
profiles adjacent each wheel. Suitable ducting is provided for discharging
regeneration scavenger stream 35 and ducting for exhaust stream
40 may be matched to the total arcuate segment of the regeneration
stream passing through desiccant wheel 20. Heating means 9 may be
any suitable heating means known to the art, such as a gas burner.
Again, while the figures show two segments 33 and 34 of the regeneration
stream passing from the regeneration stream outlet of heat wheel
10 to the regeneration stream inlet of desiccant wheel 10 it should
be recognized that any number of segments may be formed in a similar
manner to obtain the desired temperature profile. Medium temperature
regeneration stream 34 may be divided into up to about four segments
to obtain a desired temperature profile at the regeneration stream
input face of desiccant wheel 20. High temperature regeneration
stream 33U between the regeneration stream outlet face of heat wheel
10 and heating means 9 may be divided into up to four segments to
further reduce external heat requirements, and high temperature
regeneration stream 33H between heating means 9 and regeneration
stream inlet face segment 23 of desiccant wheel 20 may be divided
into up to four segments to obtain preferred high regeneration stream
temperature profiles in desiccant wheel 20. Heating means 9 may
be used to further heat specific stream segments selectively to
provide further temperature profile control. It is generally desired
that the cross sectional area of arcuate segments of high temperature
regeneration stream 33U and 33H and of medium temperature regeneration
stream 34 be increased between the regeneration stream outlet face
of heat wheel 10 and the regeneration stream inlet face of desiccant
wheel 10. Since the total arcuate angle on the regeneration side
of the desiccant wheel may be varied in different designs, the arcuate
segments of the regeneration stream will be defined as arcuate angle
fractions of the total regeneration stream output 40. The arcuate
angle fraction of high temperature regeneration stream face segment
23 to the total arcuate angle of regeneration stream exhaust 40
is suitably about 0.4 to about 0.8 preferably about 0.50 to about
0.67.
Purge stream 36 may be provided between the regeneration stream
and the process stream segments of the regeneration wheel to cool
the wheel and to remove flue gases of an open burner to render more
effective desiccation of the process stream. As shown in FIG. 2
the purge stream passes through purge stream inlet face segment
27 and purge stream outlet face segment 26 following the path shown
in FIG. 1.
The rotational speeds of both the heat wheel and the desiccant
wheel depend upon many design and operating parameters. The rotational
speed of the desiccant wheel, for high system performance, is very
sensitive to the desiccant material used, the size of the desiccant
wheel, the heat and mass transfer in the desiccant wheel, the regeneration
temperature, the inlet process stream temperature and humidity,
as well as other variables. The heat wheel similarly depends upon
many design and operating parameters. The rotational speeds of both
the desiccant wheel and the heat wheel, and the interaction of these
two rotational speeds, are important to obtain high system performance.
For given system conditions, under-adsorption and over-adsorption
in the desiccant wheel are controlled by the rotational speed of
the wheel as well as the size of the wheel arcuate segment through
which the process stream passes. Likewise, the heat wheel can provide
greater cooling effect to the process stream at a rotational speed
and size of arcuate segments through which a process stream having
desired temperature profile passes. The greater cooling of the process
stream by the heat wheel also provides higher temperature regeneration
stream segments for regeneration of the desiccant wheel. To achieve
high system efficiency, each of the heat wheel and the desiccant
wheel must operate at a rotational speed providing high efficiency
in the respective wheel. This invention provides unequal stream
face segments for the desiccant and heat wheels for a specified
stream segment which allows greater flexibility in matching the
relative rotational speeds of the wheels. According to this invention,
desired nondimensional rotational speeds of the heat wheel are in
the order of about 1 to about 4 much less than the minimum of 5
taught by heat wheel design books and papers. The lower desired
rotational speed of the heat wheel creates a more stratified temperature
profile for the outlet of the regeneration stream from the heat
wheel to yield a higher temperature regeneration stream. For the
above reasons, it is not practical to specify absolute rotational
speeds for the heat wheel and the desiccant wheel. However, computer
modeling has shown that the ability to provide unequal stream face
segments for the desiccant and heat wheels for a specific stream
segment results in reduction in the speed of both the desiccant
and the heat wheel for high efficiency performance, as compared
to prior systems having equal stream face segments for the desiccant
and heat wheels for a specific stream segment. Generally, using
the process and apparatus of this invention, high efficiency performance
is obtained by reducing the rotational speed of the heat wheel by
a factor of about 2.5 and reducing the rotational speed of the desiccant
wheel by a factor of about 2 as compared to prior systems having
equal stream face segments for the desiccant and heat wheels for
a specific stream segment. Under such operating parameters, the
performance of the system (COP) is improved about 45 percent by
use of the apparatus and process of this invention.
While in the foregoing specification this invention has been described
in relation to certain preferred embodiments thereof, and many details
have been set forth for purpose of illustration it will be apparent
to those skilled in the art that the invention is susceptible to
additional embodiments and that certain of the details described
herein can be varied considerably without departing from the basic
principles of the invention. |