U.S. patent application number 13/255198 was filed with the patent office on 2011-12-29 for dual duty compression machine.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Haiping Ding, Michael A. Stark.
Application Number | 20110314847 13/255198 |
Document ID | / |
Family ID | 42936831 |
Filed Date | 2011-12-29 |
United States Patent
Application |
20110314847 |
Kind Code |
A1 |
Ding; Haiping ; et
al. |
December 29, 2011 |
DUAL DUTY COMPRESSION MACHINE
Abstract
A compression machine includes a refrigerant condenser, an
expansion device, a refrigerant evaporator, a first compressor and
a second compressor. Each compressor is arranged to receive lower
pressure refrigerant vapor from the evaporator and to deliver
higher pressure vapor to the condenser independently of the other
compressor. The first compressor operates when the compression
machine is operating in a first duty mode, for example a
water-cooling mode. The second compressor operates when the
compression machine is operating in a second duty mode, for example
one of a water-heating mode or a brine cooling. The first
compressor is selected for optimal performance in the first duty
only and the second compressor is selected for optimal performance
in the second duty mode only.
Inventors: |
Ding; Haiping; (Shanghai,
CN) ; Stark; Michael A.; (Fayetteville, NY) |
Assignee: |
CARRIER CORPORATION
Farmington
CT
|
Family ID: |
42936831 |
Appl. No.: |
13/255198 |
Filed: |
April 1, 2010 |
PCT Filed: |
April 1, 2010 |
PCT NO: |
PCT/US2010/029595 |
371 Date: |
September 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61167978 |
Apr 9, 2009 |
|
|
|
Current U.S.
Class: |
62/115 ;
62/228.1; 62/510 |
Current CPC
Class: |
F04D 27/0269 20130101;
F04D 25/16 20130101 |
Class at
Publication: |
62/115 ; 62/510;
62/228.1 |
International
Class: |
F25B 1/10 20060101
F25B001/10; F25B 1/00 20060101 F25B001/00; F25B 49/02 20060101
F25B049/02 |
Claims
1. A dual duty compression machine for selective operation in one
of a first duty mode and a second duty mode comprising: a
refrigerant condenser, an expansion device, a refrigerant
evaporator, and a compression device disposed in a serial
refrigerant flow relationship, said compression device including a
first compressor and a second compressor, each of said first
compressor and said second compressor arranged to receive lower
pressure refrigerant vapor from said evaporator and to deliver
higher pressure vapor to said condenser independently of the other
of said first compressor and said second compressor, said first
compressor selected for optimal operation of said compression
machine in the first duty mode and said second compressor selected
for optimal operation of said compression machine in the second
duty mode.
2. The compression machine as recited in claim 1 further comprising
a control system operatively associated with each of said first
compressor and said second compressor for selectively operating
said first compressor when operating said compression machine in
the first duty mode and for selectively operating said second
compressor when operating said compression machine in the second
duty mode.
3. The compression machine as recited in claim 1 wherein at least
one of said first compressor and said second compressor comprises a
centrifugal compressor.
4. The compression machine as recited in claim 1 further comprising
a first drive motor operatively associated with said first
compressor only and a second drive motor operatively associated
with said second compressor only.
5. The compression machine as recited in claim 4 wherein said
control system is configured to direct electric power to said first
drive motor when operating said compression machine in the first
duty mode and direct electric power to said second drive motor when
operating said compression machine in the second duty mode.
6. The compression machine as recited in claim 1 wherein the first
duty mode has a first lift requirement and the second duty mode has
a second lift requirement, the second lift requirement being
greater than the first lift requirement.
7. The compression machine as recited in claim 1 wherein the first
duty mode is a water-cooling mode and the second duty mode is a
water-heating mode.
8. The compression machine as recited in claim 1 wherein the first
duty mode is a water-cooling mode and the second duty mode is a
brine-cooling mode.
9. The compression machine as recited in claim 1 wherein the first
duty mode is a water-cooling mode and the second duty mode is one
of a water-heating mode and an ice-making brine-cooling mode.
10. A method for designing a compression machine for selective
operation in one of a first duty mode or a second duty mode, the
compression machine having a condenser and an evaporator in
refrigerant flow communication with the condenser, a first
compressor for receiving refrigerant vapor from the evaporator and
delivering refrigerant vapor to the condenser, and a second
compressor for receiving refrigerant vapor from the evaporator and
delivering refrigerant vapor to the condenser, said method
comprising the steps of: selecting the first compressor to perform
optimally in the first duty mode; and selecting the second
compressor to perform optimally in the second duty mode.
11. The method for designing a compression machine as recited in
claim 10 wherein: the step of selecting the first compressor
comprises selecting a first centrifugal compressor to perform
optimally in the first duty mode only; and the step of selecting
the second compressor comprises selecting a second compressor to
perform optimally in the second duty mode only.
12. The method as recited in claim 11 wherein the first duty mode
has a first lift requirement and the second duty mode has a second
lift requirement, the second lift requirement being greater than
the first lift requirement.
13. The method as recited in claim 10 wherein the step of selecting
the first compressor to perform optimally in the first duty mode
comprises selecting the first compressor to perform optimally in a
water-cooling mode; and the step of selecting the second compressor
to perform optimally in the second duty mode comprises selecting
the second compressor to perform optimally in one of a
water-heating mode or a brine-cooling mode.
14. A method for operating a compression machine for selectively
cooling water or heating water, the compression machine having a
condenser and an evaporator in refrigerant flow communication with
the condenser, a first compressor for receiving refrigerant vapor
from the evaporator and delivering refrigerant vapor to the
condenser, and a second compressor for receiving refrigerant vapor
from the evaporator and delivering refrigerant vapor to the
condenser, said method comprising the steps of: selectively
operating the compression machine in one of a water cooling mode or
a water heating mode; operating the first compressor only when
operating the compression machine in a water cooling mode; and
operating the second compressor only when operating the compression
machine in a water heating mode.
15. The method for operating a compression machine as recited in
claim 14 wherein the first compressor is selected to perform
optimally in a water chilling mode and the second compressor is
selected to perform optimally in a water heating mode.
16. The method for operating a compression machine as recited in
claim 15 wherein at least one of the first compressor and the
second compressor comprises a centrifugal compressor.
17. The compression machine as recited in claim 1 wherein said
first compressor is selected for operation of the compression
machine for providing chilled water passing from the refrigerant
evaporator at a temperature in the range of from about 2.degree. C.
to about 12.degree. C. (about 35.degree. F. to about 54.degree.
F.).
18. The compression machine as recited in claim 1 wherein said
second compressor is selected for operation of the compression
machine for providing heated water passing from the refrigerant
condenser at a temperature in the range of from about 40.degree. C.
to about 60.degree. C. (about 104.degree. F. to about 140.degree.
F.).
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] Reference is made to and this application claims priority
from and the benefit of U.S. Provisional Application Ser. No.
61/167,978, filed Apr. 9, 2009, entitled "DUAL DUTY COMPRESSION
MACHINE", which application is incorporated herein in its entirety
by reference.
FIELD OF THE INVENTION
[0002] This invention relates generally to compression machines for
building cooling and heating application or ice thermal storage
application and, more particularly, to a compression machine having
dual compressors, one compressor dedicated for water chilling and
the other compressor dedicated for water heating or ice thermal
storage.
BACKGROUND OF THE INVENTION
[0003] Compression machines are well known for use in providing
chilled water for use in air conditioning systems for buildings,
especially large commercial buildings. A common type of compression
chiller includes a tube-in-shell heat exchanger that functions as a
refrigerant vapor condenser, a tube-in-shell heat exchanger that
functions as a refrigerant liquid evaporator, and a centrifugal
compressor that has an inlet in refrigerant flow communication with
the evaporator and an outlet in refrigerant flow communication with
the condenser. In the condenser, water is passed through the heat
exchange tubes in heat exchange relationship with hot refrigerant
vapor discharged from the compressor into the shell of the
condenser and flowing over the heat exchange tubes. In doing so,
the refrigerant vapor is condensed and the water flowing through
the heat exchange tubes is heated. The condensed liquid refrigerant
is passed through an expansion device and thereby expanded to form
a lower pressure, lower temperature refrigerant liquid/vapor
mixture. The refrigerant liquid/vapor mixture is delivered into the
shell of the evaporator and dispersed to flow over the heat
exchange tubes therein. In the evaporator, water passing through
the heat exchange tubes is cooled and the refrigerant liquid/vapor
mixture is heated and the liquid refrigerant evaporated. The
refrigerant vapor exits the shell of the evaporator and passes back
the inlet of the compressor, thereby completing the refrigerant
flow circuit.
[0004] Compression machines of this type may also be used for
heating water in the winter for building space heating purposes, in
addition to cooling water in the summer for building air
conditioning purposes. However, designing the compression machine
for dual purposes, i.e. both water-cooling in the summer and water
heating in winter is complicated due to the quite different
temperatures of the water supplied to the compression machine and
differing temperature required to be supplied to the building for
cooling/heating. The lift required for water heating in the winter
may be nearly twice the lift required for water-cooling in the
summer. Consequently, in compression machines designed with a
single compressor, the compressor must be selected to provide
sufficient capacity to meet the winter heating lift requirement,
and then be operated at a substantially reduced capacity during the
summer cooling season to match the reduced summer cooling lift
requirement. Unfortunately, compressors operating at a
substantially reduced capacity, in particular centrifugal
compressors operating at a substantially reduced capacity, suffer a
significant reduction in energy efficiency, leading to a waste of
energy and increased power consumption costs.
[0005] Although compression machines of this type typically employ
a single compressor, compression machines employing two compressors
are also known. For example, a compression chiller using two
individual centrifugal compressors arranged in series is disclosed
in U.S. Pat. No. 5,875,637. As disclosed therein, the first
compressor receives through its inlet low pressure refrigerant
vapor from the evaporator and discharges refrigerant vapor at an
intermediate pressure to the inlet of the second compressor. The
refrigerant vapor is further compressed in the second compressor
and discharged to the condenser at a relatively higher discharge
pressure.
[0006] Another example of a compression machine having two
centrifugal compressors is disclosed in U.S. Pat. No. 3,859,820. As
disclosed therein, the compression machine includes an evaporator,
a condenser divided into two separate chambers, and two separate
centrifugal compressors are in parallel. Each compressor receives
as its input refrigerant vapor from the evaporator. However, each
compressor discharges compressed refrigerant vapor into a
respective separate one of the chambers of the condenser.
[0007] In such two-compressor compression machines, increased
capacity may be achieved relative to single compressor compression
machines as both compressors, whether disposed in a series
arrangement or a parallel arrangement, are operated simultaneously.
In the series arrangement of the two centrifugal compressors, the
increased capacity is attainable because the individual rises in
refrigerant pressure developed in the separate compressors is
additive. In the parallel arrangement of the two centrifugal
compressors, the increased capacity is attainable because the
overall refrigerant throughput is the sum of the refrigerant flows
through the two centrifugal compressors. However, the increased
capacity comes at a price, as each compressor must have its own
drive motor, starter and controls. Additionally, the overall system
controls are necessarily more complicated.
SUMMARY OF THE INVENTION
[0008] In an aspect of the invention, a compression machine
provided for selective operation in one of a first duty mode and a
second duty mode. The compression machine includes: a refrigerant
condenser, an expansion device, a refrigerant evaporator, and a
compression device disposed in a serial refrigerant flow
relationship. The compression device includes a first compressor
and a second compressor, each of which is arranged to receive lower
pressure refrigerant vapor from the evaporator and to deliver
higher pressure vapor to the condenser independently of the other.
The first compressor is selected for optimum operation of the
compression machine in the first duty mode and the second
compressor is selected for optimum operation of the compression
machine in the second duty mode. In an embodiment, the first duty
mode has a first lift requirement and the second duty mode has a
second lift requirement that is greater than the first lift
requirement. In an embodiment, the first duty mode may be a
water-cooling mode and the second duty mode may be one of a
water-heating mode or a brine cooling mode.
[0009] A controller may be provided in operative association with
each of the first compressor and the second compressor, selectively
operates the first compressor when operating the compression
machine in a water-cooling mode and selectively operates the second
compressor when operating the compression machine in a
water-heating mode. The controller directs electric power to a
first drive motor for driving the first compressor when operating
the compression machine in a water-cooling mode and directs
electric power to a second drive motor for driving the second
compressor when operating the compression machine in a
water-heating mode. In an embodiment, each of the first compressor
and the second compressor comprises a centrifugal compressor.
[0010] In an aspect of the invention, a method is provided for
operating a compression machine for selectively cooling water or
heating water, the compression machine having a condenser and an
evaporator in refrigerant flow communication with the condenser, a
first compressor for receiving refrigerant vapor from the
evaporator and delivering refrigerant vapor to the condenser, and a
second compressor for receiving refrigerant vapor from the
evaporator and delivering refrigerant vapor to the condenser. The
method includes the steps of: selectively operating the compression
machine in one of a water cooling mode or a water heating mode;
operating the first compressor when operating the compression
machine in a water cooling mode; and operating the second
compressor when operating the compression machine in a water
heating mode.
[0011] In an aspect of the invention, a method is provided for
designing a compression machine for selective operation in one of a
first duty mode or a second duty mode, the compression machine
having a condenser and an evaporator in refrigerant flow
communication with the condenser, a first compressor for receiving
refrigerant vapor from the evaporator and delivering refrigerant
vapor to the condenser, and a second compressor for receiving
refrigerant vapor from the evaporator and delivering refrigerant
vapor to the condenser. The method includes the steps of: selecting
the first compressor to perform optimally in the first duty mode,
and selecting the second compressor to perform optimally in the
second duty mode. In an embodiment, the first duty mode has a first
lift requirement and the second duty mode has a second lift
requirement that is greater than the first lift requirement. In an
embodiment of the method, the step of selecting the first
compressor to perform optimally in the first duty mode comprises
selecting the first compressor to perform optimally in a
water-cooling mode; and the step of selecting the second compressor
to perform optimally in the second duty mode comprises selecting
the second compressor to perform optimally in one of a
water-heating mode or a brine-cooling mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a further understanding of the disclosure, reference
will be made to the following detailed description which is to be
read in connection with the accompanying drawings, where:
[0013] FIG. 1 is perspective view of an exemplary embodiment of a
compression machine in accordance with the invention;
[0014] FIG. 2 is a schematic diagram depicting the compression
machine of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Referring now to the drawing, there is depicted therein an
exemplary embodiment of a compression machine, designated generally
by the reference numeral 10. The compression machine 10 includes a
refrigerant condenser 20, an expansion device 25, a refrigerant
evaporator 30, and a compression device disposed in a serial
refrigerant flow relationship. The compression device includes a
first compressor 40 and a second compressor 50, each of which is
arranged to receive lower pressure refrigerant vapor from the
evaporator 30 and to deliver higher pressure refrigerant vapor to
the condenser 20 independently of the other. Separate drive motors
42, 52 are provided in operative association with the first
compressor 40 and the second compressor 50, respectively. The first
drive motor 42 drives only the first compressor 40. The second
drive motor 52 drives only the second compressor 50. In the
depicted exemplary embodiment, each of the first compressor 40 and
the second compressor 50 comprises a centrifugal compressor.
[0016] The condenser 20 is a liquid-cooled condenser and may any
one of various conventional designs. For example, for purposes of
illustration, but not limitation, the condenser 20 may be a
tube-in-shell condenser, wherein a heat transfer fluid, most
commonly, and in the application described herein, water, is passed
through a multiple-tube heat exchanger (not shown) housed in a
closed shell into which is introduced high pressure, high
temperature refrigerant vapor discharged from the compression
device. The high temperature refrigerant passes over the exterior
of the tubes of the heat exchanger in heat exchange relationship
with the water passing through the tubes of the heat exchanger,
whereby the refrigerant vapor is cooled and condensed to a
refrigerant liquid and the water is heated.
[0017] The high pressure, condensed refrigerant liquid passes from
the condenser 20 to the evaporator 30 through a refrigerant passage
11 in which is disposed an expansion device 25. As the high
pressure refrigerant liquid traverses the expansion device 25, the
refrigerant liquid expands to a lower pressure and a lower
temperature to form a refrigerant vapor or a saturated mixture of
refrigerant liquid and refrigerant vapor at the lower pressure and
the lower temperature. The lower pressure, lower temperature vapor
or liquid/vapor mixture is delivered via the passage 11 to and
introduced into the shell of the evaporator 30.
[0018] The evaporator 30 also may any one of various conventional
designs. For example, for purposes of illustration, but not
limitation, the evaporator 30 may be a tube-in-shell evaporator,
wherein a heat transfer fluid, most commonly, and in the
application described herein, water or a chemical salt solution
(brine), is passed through a multiple-tube heat exchanger (not
shown) housed in a closed shell into which is introduced the lower
pressure, lower temperature refrigerant liquid in traversing the
expansion device 25. The lower temperature refrigerant liquid
collects in the shell immersing the tubes of the heat exchanger.
Thus, the water or brine passing through the tubes passes in heat
exchange relationship with the liquid refrigerant in which the
tubes are immersed, whereby the refrigerant liquid is heated and
evaporated to a refrigerant vapor and the water or brine is
cooled.
[0019] As noted previously, the first compressor 40 and the second
compressor 50 are each arranged in the refrigerant flow circuit
between the evaporator 30 and the condenser 20. A refrigerant line
47 has an outlet opening into the shell of the condenser 20 and an
inlet in communication with the discharge outlet of the first
compressor 40 whereby the first compressor 40 discharges higher
pressure, hot refrigerant vapor into the condenser 20. Similarly, a
refrigerant line 57 has an outlet opening into the shell of the
condenser 20 and an inlet in communication with the discharge
outlet of the second compressor 50 whereby the second compressor 50
discharges higher pressure, hot refrigerant vapor into the
condenser 30.
[0020] A refrigerant line 43 has an inlet opening into the shell of
the evaporator 30 and an outlet in communication with the suction
inlet of the first compressor 40 whereby the first compressor 40
receives lower pressure refrigerant vapor from the evaporator 30.
Similarly, a refrigerant line 53 has an inlet opening into the
shell of the evaporator 30 and an outlet in communication with the
suction inlet of the second compressor 50 whereby the first
compressor 50 receives lower pressure refrigerant vapor from the
evaporator 30. A first flow shut-off valve 45 is interdisposed in
refrigerant line 43 upstream with respect to refrigerant flow of
the suction inlet to the first compressor 40. A second flow
shut-off valve 55 is interdisposed in refrigerant line 53 upstream
with respect to refrigerant flow of the suction inlet to the second
compressor 50.
[0021] The compression machine 10 may also include a control system
80 for selectively operating the first compressor 40 and the second
compressor 50. The control system may include a first controller
80-1 that is operatively associated with the first compressor 40
and its drive motor 42 and a second controller 80-2 that is
operatively associated with the second compressor 50 and its drive
motor 52, and a motor starter 82 that is capable of selectively
starting either the first compressor 40 or the second compressor 50
as directed. The control system may also include a master
controller (not shown) that selectively independently commands the
first and second controllers 80-1, 80-2. In other embodiments, the
control system 80 associated with the compression machine 10 may
include a single controller for controlling the first and second
compressors 40, 50 respectively. In the illustrated embodiment, the
control system 80 may be configured to operate the compression
machine 10 in a water-cooling mode during the summer cooling season
to supply chilled water to an air conditioning system (not shown)
of a building associated with the compression machine 10. The
control system 80 operates the compression machine 10 in a
water-heating mode during the winter heating season to provide hot
water to the air conditioning system of a building associated with
the compression machine 10. For example, for purposes of
illustration, but not limitation, the compression machine 10 may
need to supply chilled water at a temperature in the vicinity of
about 7.degree. C. (about 45.degree. F.) during the summer cooling
system, and need to supply hot water at a temperature in the
vicinity of about 50.degree. C. (about 122.degree. F.) during the
winter heating season. Thus, the lift requirement associated with
water-cooling duty would be less than the lift requirement
associated with water-heating duty.
[0022] In another application, the control system 80 may be
configured during the summer to operate the compression machine 10
in a brine-cooling mode to supply chilled brine to an air
conditioning system (not shown) of a building associated with the
compression machine 10 during the hours of the day when the
building is occupied and to supply chilled brine to an ice-storage
system (not shown) to make ice during the hours of the night when
the building occupancy is lower, such as typically at night.
Chilling brine for the air-conditioning duty would have a lower
lift requirement than chilling brine for ice-making duty.
[0023] The compression machine 10 is designed for selective
operation in one of a first duty mode and a second duty mode. The
first compressor 40 is selected for optimal operation of the
compression machine 10 in the first duty mode, for example a
water-cooling mode, and the second compressor 50 is selected for
optimal operation of the compression machine 10 in the second duty
mode, for example a water-heating mode or a brine cooling mode. In
an embodiment, first compressor 40 is selected for optimal
operation of the compression machine for providing chilled water
passing from the refrigerant evaporator at a temperature in the
range of from about 2.degree. C. to about 12.degree. C. (about
35.degree. F. to about 54.degree. F.). In an embodiment, second
compressor 50 is selected for optimal operation of the compression
machine for providing heated water passing from the refrigerant
condenser at a temperature in the range of from about 40.degree. C.
to about 60.degree. C. (about 104.degree. F. to about 140.degree.
F.). In an embodiment, the second compressor 50 is selected for
optimal operation of the compression machine 10 for providing
chilled brine to an ice thermal storage system (not shown) for use
in making ice.
[0024] To operate the compression machine 10 in the first duty
mode, for example the water-cooling mode, the controller 80 closes
the flow shut-off valve 55 in refrigerant line 53 thereby isolating
the second compressor 50 from the refrigerant circuit, supplies
electric power to the starter 82, and commands the starter 82 to
activate the first drive motor 42 for driving only the first
compressor 40. Alternately, to operate the compression machine 10
in the second duty mode, for example the water-heating mode or
brine cooling mode, the controller 80 closes the flow shut-off
valve 45 in refrigerant line 43 thereby isolating the first
compressor 40 from the refrigerant circuit, supplies electric power
to the starter 82, and commands the starter 82 to activate the
second drive motor 52 for driving only the second compressor 50.
Therefore, when operating the compression machine 10 in the first
duty mode, the first compressor 40 is operated and the second
compressor 50 is shutdown and isolated from the refrigerant
circuit. Conversely, when operating he compression machine 10 in
the second duty mode, the second compression 50 is operated and the
first compressor 40 is shut down and isolated from the refrigerant
circuit.
[0025] The compression machine 10 is designed for optimal energy
efficiency in both the water-cooling mode and the water-heating or
brine cooling mode by selecting as the first compressor 40 a first
compressor selected to perform optimally in a water cooling mode
only, and by selecting as the second compressor 50 a second
compressor selected to perform optimally in one of a water heating
mode or brine cooling mode. By selecting the second compressor 50
for optimal capacity and efficiency in the water heating mode or
ice storage mode, wherein the lift required could be as much as
about twice the lift required in the water cooling mode, the first
compressor 40 may be selected for optimal efficiency and
performance to meet the lower lift demands, while the second
compressor 50 may be selected for optimal efficiency and
performance to meet the higher lift demands. For example, in the
winter, water for delivery to the evaporator 30 may be drawn from a
outside water source at a temperature of about 7.degree. C. (about
45.degree. F.) and the hot water leaving the condenser 20 to meet
space heating demand may need to be at a temperature of about
50.degree. C. (about 122.degree. F.), while in the summer, water
for delivery to the condenser 20 may be from the outdoor water
source at a temperature of about 32.degree. C. (about 90.degree.
F.) and the chilled water leaving the evaporator 30 to meet air
conditioning demand may need to be at a temperature of about
7.degree. C. (about 45.degree. F.). With a typical single
compressor compression machine, the designer would necessarily need
to size the compressor to meet the maximum lift requirement and
compression capacity demand associated with the second duty mode
and simply expect lower than optimal efficiency performance during
operation in the first duty mode. However, the compression machine
10 of the invention provides for optimal performance in both the
lower lift requirement first duty mode and the higher lift
requirement second duty mode.
[0026] Additionally, in an embodiment the first compressor 40 and
the second compressor 50 are designed to not operate at the same
time. In this embodiment, the first compressor 40 is selected for
operation in, and is only operated, when the compression machine 10
operates in the water-cooling mode, and the second compressor 50 is
selected for operation in, and is only operated, when the
compression machine 10 operates in the water-heating mode. In this
embodiment, only one motor starter 82.
[0027] Referring now to FIG. 1, it should be noted that the second
compressor 50, which is the compressor selected for operation in
the second duty mode, that is the duty mode having the higher lift
requirement, is positioned opposite the end at which the water
enters the evaporator. In practice, the second compressor 50 should
be positioned as far as practical from the water inlet end to the
condenser to avoid liquid carry-over inside the evaporator, which
is driven by the pressure difference between the condenser and the
evaporator.
[0028] The terminology used herein is for the purpose of
description, not limitation. Specific structural and functional
details disclosed herein are not to be interpreted as limiting, but
merely as basis for teaching one skilled in the art to employ the
present invention. While the present invention has been
particularly shown and described with reference to the exemplary
embodiments as illustrated in the drawing, it will be recognized by
those skilled in the art that various modifications may be made
without departing from the spirit and scope of the invention. Those
skilled in the art will also recognize the equivalents that may be
substituted for elements described with reference to the exemplary
embodiments disclosed herein without departing from the scope of
the present invention.
[0029] Therefore, it is intended that the present disclosure not be
limited to the particular embodiment(s) disclosed as, but that the
disclosure will include all embodiments falling within the scope of
the appended claims.
* * * * *