U.S. patent application number 12/667280 was filed with the patent office on 2010-08-12 for refrigerant system with bypass line and dedicated economized flow compression chamber.
Invention is credited to Alexander Lifson, Michael F. Taras.
Application Number | 20100199715 12/667280 |
Document ID | / |
Family ID | 40511723 |
Filed Date | 2010-08-12 |
United States Patent
Application |
20100199715 |
Kind Code |
A1 |
Lifson; Alexander ; et
al. |
August 12, 2010 |
REFRIGERANT SYSTEM WITH BYPASS LINE AND DEDICATED ECONOMIZED FLOW
COMPRESSION CHAMBER
Abstract
A refrigerant system has an economizer cycle. A vapor
refrigerant from the economizer loop is returned to a dedicated
economizer compression chamber. A main refrigerant is returned to a
dedicated main compressor chamber. A bypass line communicates the
two refrigerant flows.
Inventors: |
Lifson; Alexander; (Manlius,
NY) ; Taras; Michael F.; (Fayetteville, NY) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD, SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
40511723 |
Appl. No.: |
12/667280 |
Filed: |
September 24, 2007 |
PCT Filed: |
September 24, 2007 |
PCT NO: |
PCT/US2007/079260 |
371 Date: |
December 30, 2009 |
Current U.S.
Class: |
62/510 ; 62/512;
62/513 |
Current CPC
Class: |
F25B 2309/061 20130101;
F25B 2400/075 20130101; F25B 2600/2501 20130101; F25B 2600/2509
20130101; F25B 41/20 20210101; F25B 2400/13 20130101; F25B 40/00
20130101 |
Class at
Publication: |
62/510 ; 62/513;
62/512 |
International
Class: |
F25B 1/10 20060101
F25B001/10; F25B 41/00 20060101 F25B041/00; F25B 43/00 20060101
F25B043/00 |
Claims
1. A refrigerant system comprising: at least two compression
chambers, said at least two compression chambers for compressing a
refrigerant, a downstream heat rejection heat exchanger, a
refrigerant line passing from the heat rejection heat exchanger
into an economizer cycle, and a main refrigerant line passing from
the economizer cycle through a main expansion device and to a heat
accepting heat exchanger, a suction line downstream of said heat
accepting heat exchanger and extending to at least one of the at
least two compression chambers; a return line being returned from
the economizer cycle to at least one other of the at least two
compression chambers; and a bypass line communicating the return
line and the suction line.
2. The refrigerant system as set forth in claim 1, wherein said
bypass line includes a restriction to allow continuous
communication between the return line and the suction line.
3. The refrigerant system as set forth in claim 2, wherein said
bypass line includes an electrically controlled valve to provide
selective communication.
4. The refrigerant system as set forth in claim 3, wherein said
electrically controlled valve is a solenoid on/off valve.
5. The refrigerant system as set forth in claim 3, wherein said
electrically controlled valve is controlled by a pulse width
modulation technique.
6. The refrigerant system as set forth in claim 3, wherein said
electrically controlled valve is a modulating valve.
7. The refrigerant system as set forth in claim 3, wherein said
electrically controlled valve is opened to equalize pressure upon
refrigerant system shutdown or before startup.
8. The refrigerant system as set forth in claim 2, wherein said
restriction is an orifice.
9. The refrigerant system as set forth in claim 2, wherein said
restriction has a cross-section area between 0.1 square millimeter
and 3 square millimeters.
10. The refrigerant system as set forth in claim 2, wherein said
restriction is a capillary tube.
11. The refrigerant system as set forth in claim 1, further
comprising an electrically controlled valve installed in parallel
with said bypass line.
12. The refrigerant system as set forth in claim 1, wherein said
economizer cycle includes a flash tank to separate liquid and vapor
refrigerant phases.
13. The refrigerant system as set forth in claim 1, wherein said
compression chambers are independent compressors.
14. The refrigerant system as set forth in claim 1, wherein said
compression chambers are positioned within a single compressor.
15. The refrigerant system as set forth in claim 14, wherein said
bypass line is located externally in relation to the
compressor.
16. The refrigerant system as set forth in claim 14, wherein said
bypass line is located internally in relation to the
compressor.
17. The refrigerant system as set forth in claim 14, wherein said
compressor is reciprocating compressor and said compression
chambers are reciprocating compressor cylinders.
18. The refrigerant system as set forth in claim 1, wherein at
least one of said at least two compression chambers is represented
by sequential compression stages.
19. The refrigerant system as set forth in claim 1, wherein said
economizer cycle includes an economizer heat exchanger having an
economizer expansion device expanding a tapped portion of
refrigerant and passing it through the economizer heat exchanger to
exchange heat with the main refrigerant, with said tapped
refrigerant being returned through the return line.
20. The refrigerant system as set forth in claim 1, wherein at
least one said compression chamber is a part of at least one
reciprocating compressor cylinder.
21. The refrigerant system as set forth in claim 1, wherein the
refrigerant streams in said return line and suction line are
partially combined together at subcritical pressure.
22. The refrigerant system as set forth in claim 1, wherein said
refrigerant is selected from a group consisting of R744, R22,
R410A, R134a, R407C, R290, R600a refrigerants or their
combinations.
23. A method of operating a refrigerant system comprising:
providing at least two compression chambers, said at least two
compression chambers compressing refrigerant and delivering the
refrigerant to a downstream heat rejection heat exchanger,
refrigerant passing from the heat rejection heat exchanger into an
economizer cycle, and a main flow of refrigerant passing from the
economizer cycle through a main expansion device and to a heat
accepting heat exchanger, refrigerant from the heat accepting heat
exchanger passing through a suction line to at least one of the at
least two compression chambers; an economized flow of refrigerant,
that is at least largely vapor, being returned from the economizer
cycle to at least one other of the at least two compression
chambers through a return line; and communicating the return line
and the suction line through a bypass line.
24. The method as set forth in claim 23, wherein an electrically
controlled valve on said bypass line is opened to unload the
refrigerant system.
25. The method as set forth in claim 23, wherein an electrically
controlled valve on said bypass line is opened to return oil.
Description
BACKGROUND OF THE INVENTION
[0001] This application relates to a refrigerant system having an
economizer cycle, and wherein an economized refrigerant flow is
returned to an economizer compression chamber of a compression
unit, and a main refrigerant flow is returned to a main compression
chamber of a compression unit, wherein a bypass refrigerant line
communicates the two refrigerant flows upstream of their
corresponding compression chambers.
[0002] Refrigerant compressors compress and circulate a refrigerant
throughout a refrigerant system to condition a secondary fluid,
typically delivered to a climate-controlled space. In a basic
refrigerant system, a compressor compresses a refrigerant and
delivers it to a heat rejection heat exchanger. Refrigerant from
the heat rejection heat exchanger passes through an expansion
device, in which its pressure and temperature are reduced.
Downstream of the expansion device, the refrigerant passes through
a heat accepting heat exchanger, and then back to the compressor.
As known, the heat accepting heat exchanger is typically an
evaporator, and the heat rejecting heat exchanger is a condenser
for subcritical applications and a gas cooler for transcritical
applications.
[0003] One option in a refrigerant system design to enhance
performance is the use of an economizer, or vapor injection
function. When an economizer function is activated, a portion of
refrigerant is tapped from a main refrigerant stream downstream of
the heat rejection heat exchanger. In one configuration, this
tapped refrigerant is passed through an auxiliary expansion device,
to be expanded to an intermediate pressure and temperature, and
then this partially expanded tapped refrigerant passes in heat
exchange relationship with a main refrigerant flow in an economizer
heat exchanger. In this manner, the main refrigerant flow is cooled
such that it will have a greater thermodynamic potential when it
reaches the heat accepting heat exchanger. The tapped refrigerant,
typically in a superheated thermodynamic state, is returned to the
compressor.
[0004] As known, an economizer function can be performed in either
a flash tank or in an economizer heat exchanger. For purposes of
this application, the two devices will be both known as an
"economizer heat exchanger."
[0005] As described in European Patent Application EP1498667, the
vapor refrigerant is returned to a dedicated economizer compression
chamber or a compressor. The main refrigerant flow is returned from
the heat accepting heat exchanger back to its own dedicated
compression chamber or compressor. This known system maintains the
economizer and suction refrigerant flows completely isolated from
each other. A purpose of the dedicated compression chambers is to
have two separate non-mixing inlet refrigerant streams, each
compressing refrigerant from a particular thermodynamic state to a
common discharge thermodynamic state.
SUMMARY OF THE INVENTION
[0006] In a disclosed embodiment of this invention, a refrigerant
system is provided with an economizer cycle, where an economized
refrigerant stream is returned from the economizer circuit back to
a dedicated economizer compression chamber (or a separate
compressor) through an economizer circuit return line. A main
refrigerant stream is returned to its own dedicated main
compression chamber (or a compressor) through a suction line. A
bypass line communicates the two refrigerant flow lines upstream of
their corresponding inlets to the dedicated compression chambers
(or compressors). In this arrangement, the two inlet refrigerant
streams are allowed to selectively communicate and mix with each
other via the bypass line. In one embodiment, the bypass line may
have a small orifice which always communicates the two refrigerant
streams. In a second embodiment, the bypass line may include a
controlled valve. In a third embodiment, the bypass line may
include a combination of these two options.
[0007] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 shows a prior art system.
[0009] FIG. 2 shows a schematic of a first embodiment.
[0010] FIG. 3 shows a schematic of a second embodiment.
[0011] FIG. 4 shows a schematic of a third embodiment.
[0012] FIG. 5 shows a schematic of a fourth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] FIG. 1 shows a prior art refrigerant system 20. As known a
compression unit 22 includes at least two chambers, cylinders, or
compressors 24 and 26. The two compression chambers compress
refrigerant and deliver it downstream to a heat rejection exchanger
28. The heat rejection exchanger 28 can be a condenser (if the
refrigerant discharge thermodynamic state is below the critical
point) or a gas cooler (if the refrigerant discharge thermodynamic
state is above the critical point). An expansion device 29 is
positioned downstream of the heat rejection heat exchanger, and
partially expands refrigerant passing into a flash tank 30 to an
intermediate pressure. An expansion device 34 is positioned
downstream of the flash tank 30, to control the amount of
refrigerant reaching an evaporator 36, and expands this refrigerant
to a pressure approximating the suction pressure. In the flash tank
30, a liquid refrigerant is separated from a vapor refrigerant. The
liquid refrigerant from the flash tank 30 is expanded to a
two-phase thermodynamic state in the expansion device 34, flows
through the evaporator 36, where it evaporates and is typically
superheated, passes through a suction line 38 and is returned to
the dedicated main compression chamber 26. The separated vapor
refrigerant passes through a return line 32 of the economizer
circuit to its dedicated compression chamber 24. In the known prior
art system, the lines 32 and 38 are maintained strictly separate. A
purpose of the two separate lines delivering refrigerant to two
dedicated compression chambers 24 and 26 is to have refrigerant in
each of the compression chambers be closer to homogeneous
conditions than if the two refrigerant flows were allowed to
mix.
[0014] FIG. 2 shows an embodiment 40 wherein the compression unit
42 has a dedicated economizer compression chamber 44 and a
dedicated main compression chamber 46. However, a bypass line 48
including a restriction 49 is provided to communicate an economizer
refrigerant flow and a main refrigerant flow. This restriction can
be in a form of an orifice; however it can also be a capillary tube
or any other type of a restriction that throttles the refrigerant
flow. Typically the size of the orifice is selected to have a
cross-sectional area between 0.1 to 3 square millimeters. Other
restriction types may have a different cross-sectional area;
however their effective cross-sectional area is sized to correspond
to an equivalent orifice area in the range mentioned above.
[0015] A purpose of this bypass line 48 is to allow pressure
equalization on startup. This will allow reduce motor starting
torque, resulting in a more efficient operation, and allow the use
of smaller and less expensive motors. Also, the orifice allows
drainage of lubricating oil from the economizer line 32 to the
suction line 38 after shutdown. A shutoff valve 33 may be included
on the economizer circuit return line 32.
[0016] FIG. 3 shows an embodiment 50 having a compression unit 52
having dedicated compression chambers 54 and 56. The bypass line 58
includes an electrically controlled valve, which in this embodiment
is disclosed as a controlled solenoid valve 59, which may be opened
or closed. The solenoid valve may be opened to allow mixing of main
and economized refrigerant streams during continuous operation, or
can be opened prior to startup for pressure equalization, or can be
opened at or after shutdown for oil return. Also, in some
circumstances, the valve 59 may be operated in a pulse mode such
as, for instance, to facilitate oil return or unload the
compression unit 50. Further, the valve 59 may be of a modulating
type to tailor valve opening to specific operating conditions
(operating pressures, in particular) and precisely match thermal
load demands in the conditioned space.
[0017] As shown in FIG. 4, a refrigerant system 60 has a
compression unit 62 with dedicated compression chambers 64 and 66,
as in the prior embodiments. However, the bypass function now has
both the solenoid valve 59 on the bypass line 58 and an orifice 68
on a branch bypass line 66. The embodiment 60 would achieve the
benefits of each of the embodiments of FIGS. 2 and 3, and allow the
control at shutdown or startup without the need to open the valve
59. The bypass lines 58 and 66 may be arranged in a parallel
configuration, between the economizer circuit return line 32 and
the main circuit suction line 38, as well.
[0018] FIG. 5 shows yet another embodiment 80 having a compression
unit 82 with separate compression chambers 84 and 86. In the
embodiment 80, the economizer function is provided by an economizer
heat exchanger 94, rather than the flash tank 30 of previous
embodiments. As known, a tap line 90 taps a portion of refrigerant
from a main refrigerant flowing through a liquid line 88 and passes
this refrigerant through an economizer expansion device 92, where
it is expanded to a lower intermediate pressure and temperature.
This would allow the refrigerant in the tap line 90 to further cool
the main refrigerant in the liquid line 88, while passing through
the economizer heat exchanger 94. The economized refrigerant,
typically in the vapor thermodynamic state, flows into the return
line 96 of the economizer circuit. A main circuit expansion device
34 is positioned downstream of the economizer heat exchanger 94 to
control the amount of liquid refrigerant reaching the evaporator
36. While the economized refrigerant flow in the tap line 90 and
the main refrigerant flow in the liquid line 88 are shown passing
through the economizer heat exchanger 94 in the same direction, in
practice, they are preferably flown in counterflow relationship.
The two refrigerant streams are shown flowing in the same direction
for illustration simplicity only. Furthermore, the tap line 90 may
be positioned downstream of the economizer heat exchanger 94.
[0019] Similar to previous embodiments, the bypass line 58 is shown
with the solenoid valve 59. Further, the economizer heat exchanger
94 may be utilized in the embodiments of FIG. 2 or 4 as well,
instead of the flash tank 30.
[0020] As stated above, the flow control device 59 may have an
adjustable orifice to control the amount of communicated
refrigerant between the dedicated economizer and main compression
chambers, based, for instance, on operating conditions and thermal
load demand in the conditioned space. On the other hand, the
solenoid valve 59 may be controlled by a pulse width modulation
technique to achieve similar results for compressor unit unloading
or to facilitate oil return and assure reliable compressor
operation.
[0021] It should be pointed out that many different compressor
types could be used in this invention. For example, scroll, screw,
rotary, or reciprocating compressors can be employed. The
economized flow and main flow chambers can be separate compressors,
or these compression chambers can be positioned within a single
compressor. In the context of this invention, each compression
chamber can be represented by a single cylinder or multiple
cylinders, as for example, may be the case for a reciprocating
compressor. If the compression chambers are located within a single
compressor, then the bypass line can be located internally or
externally, in relation to the compressor shell. If the compression
chambers are independent compressors then the preferable location
for the bypass line would be external to these compressors.
Further, each of the dedicated compression chambers may have a
number of sequential compression stages, with the dedicated main
compression chambers having a higher number of sequential
compression stages then the dedicated economizer compression
chambers, since they operate between higher pressure
differentials.
[0022] This invention would apply to a broad range of refrigerants
including, but not limited to, R744, R22, R134a, R410A, R407C,
R290, R600a and their combinations.
[0023] The refrigerant systems that utilize this invention can be
used in many different applications, including, but not limited to,
air conditioning systems, heat pump systems, marine container
units, refrigeration truck-trailer units, and supermarket
refrigeration systems. The refrigerant system of this invention can
be a subcritical of transcritical system.
[0024] Although an embodiment of this invention has been disclosed,
a worker of ordinary skill in this art would recognize that certain
modifications would come within the scope of this invention. For
that reason, the following claims should be studied to determine
the true scope and content of this invention.
* * * * *