U.S. patent application number 13/811359 was filed with the patent office on 2013-08-08 for rankine cycle system and method.
This patent application is currently assigned to MODINE MANUFACTURING COMPANY. The applicant listed for this patent is George A. Baker, JR., Mark R. Hoehne, Greg Mross, Mark G. Voss. Invention is credited to George A. Baker, JR., Mark R. Hoehne, Greg Mross, Mark G. Voss.
Application Number | 20130199173 13/811359 |
Document ID | / |
Family ID | 46084337 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130199173 |
Kind Code |
A1 |
Voss; Mark G. ; et
al. |
August 8, 2013 |
RANKINE CYCLE SYSTEM AND METHOD
Abstract
A Rankine cycle system and method is described and illustrated,
and in some embodiments includes an expander, a pump, a condenser,
and a receiver comprising a variable fluid volume at least
partially defined by a movable member, wherein the variable fluid
volume defines at least a portion of the working fluid flow path
between the condenser and the inlet of the pump. Also, a method of
charging a Rankine cycle system with working fluid is described and
illustrated, and can include applying a regulated pressure to a
chamber located within a receiver, introducing the working fluid to
the Rankine cycle system, the working fluid being separated from
the chamber by a movable member of the receiver, monitoring
displacement of the movable member, and stopping the introduction
of working fluid into the Rankine cycle system when the movable
member reaches a predetermined position.
Inventors: |
Voss; Mark G.; (Franksville,
WI) ; Baker, JR.; George A.; (Waterford, WI) ;
Hoehne; Mark R.; (Lake Villa, IL) ; Mross; Greg;
(Sturtevant, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Voss; Mark G.
Baker, JR.; George A.
Hoehne; Mark R.
Mross; Greg |
Franksville
Waterford
Lake Villa
Sturtevant |
WI
WI
IL
WI |
US
US
US
US |
|
|
Assignee: |
MODINE MANUFACTURING
COMPANY
Racine
WI
|
Family ID: |
46084337 |
Appl. No.: |
13/811359 |
Filed: |
August 26, 2011 |
PCT Filed: |
August 26, 2011 |
PCT NO: |
PCT/US11/49376 |
371 Date: |
January 21, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61407119 |
Oct 27, 2010 |
|
|
|
Current U.S.
Class: |
60/530 ;
60/643 |
Current CPC
Class: |
F01K 27/00 20130101;
F01K 25/10 20130101 |
Class at
Publication: |
60/530 ;
60/643 |
International
Class: |
F01K 27/00 20060101
F01K027/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] This invention was made with government support under
Contract No. W909MY-09-C-0084 awarded by the US Army, Research,
Development and Engineering Command. The government has certain
rights in the invention.
Claims
1. A Rankine cycle system comprising: an expander; a pump; a
condenser located along a working fluid flow path between an outlet
of the expander and an inlet of the pump; and a receiver comprising
a variable fluid volume at least partially defined by a movable
member, wherein the variable fluid volume defines at least a
portion of the working fluid flow path between the condenser and
the inlet of the pump.
2. The system of claim 1, further comprising a liquid sub-cooler
located along the working fluid flow path between the receiver and
the inlet of the pump.
3. The system of claim 2, wherein the condenser and the liquid
sub-cooler are parts of a single heat exchanger.
4. The system of claim 1, wherein at least a portion of the
variable fluid volume defines a cylindrical volume, the movable
member defining an end of the cylindrical volume.
5. The system of claim 4, wherein the movable member is movably
disposed within the receiver so as to vary the length of the
cylindrical volume.
6. The system of claim 1, wherein the variable fluid volume is a
first variable fluid volume, the receiver further comprising a
second variable fluid volume at least partially defined by the
movable member.
7. The system of claim 6, wherein the second variable fluid volume
is in fluid communication with the environment outside of the
receiver to maintain a substantially atmospheric pressure within
the second variable fluid volume.
8. The system of claim 6, wherein the second variable fluid volume
is in fluid communication with a regulated pressure source.
9. The system of claim 1, wherein the movable member is positioned
within the receiver, and wherein the receiver includes a position
indicator to indicate the location of the movable member within the
receiver.
10. The system of claim 9, wherein the position indicator is
magnetically coupled to the movable member.
11. The system of claim 1, wherein the variable fluid volume is
further defined by an end face of the receiver, the end face
including first and second ports in fluid communication with the
variable fluid volume and defining portions of the working fluid
flow path immediately upstream and downstream of the variable fluid
volume.
12. The system of claim 11, wherein at least one of the end face
and the movable member includes an offset surface so that a fluid
flowpath is maintained between the first and second ports when the
offset surface is in contact with the other of the end face and the
movable member.
13. A method of charging a Rankine cycle system with working fluid,
comprising: applying a regulated pressure to a chamber located
within a receiver in the Rankine cycle system; introducing the
working fluid to the Rankine cycle system, the working fluid being
separated from the chamber by a movable member of the receiver;
monitoring displacement of the movable member; and stopping the
introduction of working fluid into the Rankine cycle system when
the movable member reaches a predetermined position.
14. The method of claim 13, wherein the regulated pressure is
greater than a saturation pressure corresponding to a temperature
of the working fluid.
15. The method of claim 13, wherein monitoring the displacement of
the movable member includes at least one of visual observation of
the movable member and electronic measurement of the movable
member.
16. The method of claim 13, wherein monitoring the displacement of
the movable member includes monitoring the displacement of a
position indicator magnetically coupled to the movable member.
17. A method of pressure adjustment within a Rankine cycle system
having an expander and a pump, the method comprising: changing a
pressure of working fluid within the system between the expander
and the pump; changing a volume of an internal chamber of a
receiver in fluid communication between the expander and the pump
responsive to changing the pressure of the working fluid within the
system.
18. The method of claim 17, wherein changing the volume of the
internal chamber comprises moving a portion of the receiver.
19. The method of claim 17, further comprising receiving the
working fluid into the receiver from a first heat exchanger
portion, and discharging the working fluid from the receiver to a
second heat exchanger portion.
20. The method of claim 17, further comprising changing a volume of
a second internal chamber in the receiver responsive to changing
the pressure of the working fluid within the system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/407,119, filed Oct. 27, 2010, the entire
contents of which are hereby incorporated by reference herein.
BACKGROUND
[0003] Vapor power cycles are known in the art as a means whereby
heat energy can be converted to useful mechanical work. One such
cycle, commonly known as the Rankine cycle, utilizes a working
fluid that is cyclically pressurized from a low-pressure liquid
state, vaporized using a heat source, non-adiabatically expanded to
a low-pressure vapor, and cooled and condensed back to the
low-pressure liquid state. In cycles of this kind, mechanical
energy is produced during the non-adiabatic expansion of the
vapor.
[0004] Rankine cycle systems may be especially beneficial in
recovering energy from waste heat streams. Such waste heat stream
may, for example, be found in the exhaust of a combustion process
such as a burner or a combustion engine. In some applications, a
Rankine cycle waste heat recovery system can be advantageously
employed on a vehicle to recover waste heat from the exhaust of the
internal combustion engine powering the vehicle. As vehicle
efficiency standards are pushed progressively higher, such waste
heat recovery systems become a means by which the required
efficiency targets can be achieved.
[0005] A variety of working fluids may be suitable for use with
Rankine cycle systems. As one example, water is commonly used as a
working fluid in steam turbines operating on a Rankine cycle. For
certain applications, however, other fluids may be preferable.
[0006] An undesirable condition can sometimes occur in Rankine
cycle systems when the working fluid is cooled to a temperature
that corresponds to a saturation pressure that is lower than the
atmospheric pressure. Preventing the infiltration of ambient air
into the system can be exceedingly difficult with the resulting
pressure gradient, and the presence of such non-condensable gases
into the working fluid volume can cause the Rankine cycle system to
operate in a sub-optimal fashion, or even to not operate at
all.
SUMMARY
[0007] According to some embodiments of the invention, a Rankine
cycle system includes a pump, an expander, and a condenser located
along a working fluid flow path between an outlet of the expander
and an inlet of the pump. The system also includes a receiver
comprising a variable fluid volume at least partially defined by a
movable member, wherein the variable fluid volume defines at least
a portion of the working fluid flow path between the condenser and
the inlet of the pump.
[0008] In some embodiments, the system includes a liquid sub-cooler
located along the working fluid flow path between the receiver and
the inlet of the pump. The condenser and the liquid sub-cooler may
be parts of a single heat exchanger in certain embodiments.
[0009] In some embodiments, at least a portion of the variable
fluid volume defines a cylindrical volume, with the movable member
defining an end of the cylindrical volume. The movable member may
be movably disposed within the receiver so as to vary the length of
the cylindrical volume.
[0010] According to some embodiments, the receiver further
comprises a second variable fluid volume at least partially defined
by the movable member. In some such embodiments the second variable
fluid volume is in fluid communication with the environment to
maintain a substantially atmospheric pressure within the second
variable fluid volume, while in other such embodiments the second
variable fluid volume is in fluid communication with a regulated
pressure source.
[0011] In some embodiments, the receiver includes a position
indicator to indicate the location of the movable member within the
receiver. The position indicator may, in some embodiments of the
invention, be magnetically coupled to the movable member.
[0012] According to some embodiments, the variable fluid volume is
further defined by an end face of the receiver. The end face can
include first and second ports in fluid communication with the
variable fluid volume, the ports defining portions of the working
fluid flow path immediately upstream and downstream of the variable
fluid volume. In some embodiments, at least one of the end face and
the movable member includes an offset surface so that a fluid
flowpath is maintained between the first and second ports when the
offset surface is in contact with the other of the end face and the
movable member.
[0013] Some embodiments of the invention provide a method of
charging a Rankine cycle system with working fluid, including the
steps of: applying a regulated pressure to a chamber located within
a receiver in the Rankine cycle system; introducing the working
fluid to the Rankine cycle system, the working fluid being
separated from the chamber by a movable member in the receiver;
monitoring the displacement of the movable member; and stopping the
introduction of working fluid into the Rankine cycle system when
the movable member reaches a predetermined position. In some
embodiments, the regulated pressure is greater than the saturation
pressure corresponding to the temperature of the working fluid.
[0014] These and other aspects of the invention will become
apparent to one of ordinary skill in the art upon inspection of the
following detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic diagram of a Rankine cycle system
according to an embodiment of the present invention.
[0016] FIG. 2 is a perspective view of a receiver according to an
embodiment of the present invention.
[0017] FIG. 3 is a sectional perspective view of the receiver of
FIG. 2, taken along lines 3-3 of FIG. 2.
[0018] FIG. 4 is a perspective view of a receiver according to
another embodiment of the present invention.
[0019] FIG. 5 is a perspective view showing the interrelation of
certain components of the system of FIG. 1 according to an
embodiment of the invention.
[0020] FIG. 6 is a graph of saturation pressure vs. temperature for
two different fluids.
DETAILED DESCRIPTION
[0021] Before any embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangement
of components set forth in the following description or illustrated
in the accompanying drawings. The invention is capable of other
embodiments and of being practiced or of being carried out in
various ways. Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," or "having" and variations thereof herein is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. Unless specified or limited otherwise,
the terms "mounted," "connected," "supported," and "coupled" and
variations thereof are used broadly and encompass both direct and
indirect mountings, connections, supports, and couplings. Further,
"connected" and "coupled" are not restricted to physical or
mechanical connections or couplings.
[0022] A Rankine cycle system 1 according to an embodiment of the
present invention is depicted in schematic fashion in FIG. 1. The
movement of a working fluid through the system 1 is illustrated by
the solid black arrows. As shown, a pump 2 directs the working
fluid through the system 1 in a closed loop. Energy in the form of
heat is received by pressurized liquid working fluid in a heating
section 4, and a portion of that energy is removed from the working
fluid and converted to useful work in an expander 3. The heating
section 4 may include one or more heat exchangers through which the
working fluid can be directed in order to vaporize the pressurized
liquid working fluid, thereby converting it to a pressurized vapor
state. The heat so transferred in the heating section 4 may in some
cases be waste heat contained in an exhaust stream of a process
such as, for example, a combustion process. In other cases, the
heat may be derived from other sources.
[0023] The working fluid can be any type of fluid that may be
advantageously used in such cycles. By way of example only, the
working fluid may include: water; ammonia; alcohols, including but
not limited to ethanol and methanol; refrigerants, including but
not limited to R134a, R152a, and R22; hydrocarbons, including but
not limited to propane and butane; organic working fluids,
including but not limited to R245fa; and combinations thereof.
[0024] It should be understood that the pump 2 can be any type of
machinery used to pressurize and provide motive flow to a liquid,
including but not limited to positive displacement pumps,
reciprocating action pumps, rotary action pumps, kinetic pumps and
centrifugal pumps, among others. Similarly, the expander 3 can be
any type of machinery capable of converting pressure energy into
mechanical work, including but not limited to piston expanders,
impulse turbines and reaction turbines, among others.
[0025] Continuing with the description of the system of FIG. 1, the
working fluid exits the expander 3 as a low-pressure (relative to
the pressure at which it enters the expander 3) vapor, and is
returned to the pump 2 inlet by way of a flowpath 9. Along the
flowpath 9, residual heat is rejected from the working fluid in a
condenser 5, thereby converting the low-pressure vapor to a
low-pressure liquid. Additionally, a receiver 6 is located along
the flowpath 9 between the condenser 5 and the inlet of the pump 2.
A sub-cooler 7 may optionally be included between the receiver 6
and the pump inlet in order to reject additional heat from the
working fluid. In some embodiments, however, the sub-cooler 7 may
not be included, or it may be incorporated into the condenser
5.
[0026] The illustrated receiver 6 contains a movable member 8 that
at least partially defines a chamber 10 within the receiver 6. The
chamber 10 comprises a portion of the flow path 9 between the exit
of the condenser and the inlet of the pump 2, so that the working
fluid traveling along the flowpath 9 passes through the chamber 10
between the condenser 5 and the pump inlet.
[0027] One embodiment of a receiver 6 is shown in greater detail in
FIGS. 2 and 3. The receiver 6 as shown therein includes a port 20
whereby working fluid can enter into the chamber 10, and a port 21
whereby working fluid can exit the chamber 10. An additional
optional port 22 is also shown. This additional port 22 may be
adapted to a number of uses, including connection of a pressure or
temperature sensor, venting non-condensable gases from the receiver
6, providing a pressure relief vent, and providing a convenient
working fluid charging port for the waste heat recovery system
1.
[0028] The illustrated receiver 6 as shown in FIGS. 2 and 3
additionally includes a cylindrical shell 12 extending between
first and second end caps 13, 14. The first and second end caps 13,
14 are in turn connected to first and second end plates 15, 16
respectively. These connections may be accomplished by way of
mechanical fasteners (e.g. screws or the like), or by welding,
soldering, brazing, or other known processes. In some cases, the
first end plate 15 may be integral to the first end cap 13, and
similarly the second end plate 16 may be integral to the second end
cap 14. The shell 12 is sealingly attached to the end caps 13, 14
by way of o-rings 19. Tie rods 17 extend between the end plates 15,
16 in order to maintain assembly between the shell 12 and the end
caps 13, 14, and to resist the pressure that may be exerted by the
working fluid during operation.
[0029] As best seen in the sectional view of FIG. 3, the movable
member 8 may be embodied as a free piston. The chamber 10 is
located between the movable member 8 and the first end cap 13,
whereas the chamber 11 is located between the movable member 8 and
the second end cap 14. The movable member 8 is disposed within the
shell 12 so as to be movable in sliding fashion between the end
plates 13, 14. O-rings 18 are positioned within grooves in the free
piston comprising the movable member 8 in order to provide
leak-free separation between the chambers 10, 11.
[0030] In other embodiments, the illustrated movable member 8 may
be replaced with another structure or device suitable for adjusting
the volume of the chamber 10. For example, in some embodiments, the
movable member may include a diaphragm that deflects to adjust the
volume of the chamber 10. In further embodiments, the shell 12 may
include one or more elastomeric or movable walls that function as
the movable member to adjust the volume of the chamber 10. In still
further embodiments, the receiver 6 may include a combination of
pistons, diaphragms, and/or movable walls that function as the
movable member.
[0031] The illustrated movable member 8 of the illustrated
embodiment is able to translate along the direction of the shared
axis of the movable member 8 and the shell 12. This movement may be
resisted by the friction forces resulting from the sliding of the
o-rings 18 along the inner wall of the shell 12. This resistive
force can be adjusted to the desired level by proper sizing of the
o-rings 18 and the clearance gap between the shell 12 and the
movable member 8.
[0032] With continued reference to the illustrated embodiment of
FIGS. 2 and 3, the movable member 8 includes an offset surface 33
arranged to function as a stop for the movable member 8 against the
first end cap 13. This ensures that the fluid flow path 9 is
maintained between the ports 20, 21 even when the movable member 8
is at its limit of travel. Although the offset surface 33 is on the
movable member 8 in the exemplary embodiment, it could additionally
or alternatively be on the first end cap 13 and accomplish the same
function.
[0033] The second end cap 14 includes one or more ports 23 (two are
shown in FIG. 3) whereby fluid can be added to or removed from the
chamber 11. In doing so, the fluid pressure within the chamber 11
may be regulated and, by extension, the fluid pressure within the
chamber 10 may be also regulated. As one example, the port(s) 23
may be exposed to ambient pressure so that the pressure of air
within the chamber 11 is approximately equal to the ambient
pressure. As another example, one or more of the ports 23 may be
fluidly connected to a regulated pressure source so that fluid
pressure within the chamber 11 can be maintained at a relatively
constant, elevated pressure.
[0034] When the pressure imbalance between the chambers 10, 11
results in a net force on the movable member 8 that exceeds the
frictional resistive force of the o-rings 18 on the wall of the
shell 12, then the movable member 8 will displace in the direction
of the chamber 10, 11 having the lower pressure, unless and until
the movable member 8 contacts one of the end caps 13, 14. Since the
fluid chamber 10 is a portion of the total working fluid volume of
the Rankine cycle system 1, changing the volume of the chamber 10
can result in a change in the working fluid pressure at the suction
side of the pump 2.
[0035] When the system 1 is in a non-operating state, the
temperature and pressure of the working fluid will be relatively
constant throughout the entire working fluid volume of the system
1, and the charge of working fluid contained within that volume can
exist as either a liquid, a vapor, or a two-phase liquid/vapor
mixture, depending on the temperature and pressure. As the system 1
begins to operate, the addition of heat to the working fluid
results in an increase of the system pressure at both the high
pressure side (between the pump outlet and the expander inlet) and
the low pressure side (between the expander outlet and the pump
inlet).
[0036] The increase in pressure of the working fluid in the chamber
10 acting on the face of the movable member 8 causes the movable
member 8 to move away from the first end cap 13 and towards the
second end cap 14. This movement of the movable member 8 results in
a volumetric increase of the chamber 10, and a corresponding
volumetric decrease of the chamber 11. The increase in volume of
the chamber 10 counteracts the increase in working fluid pressure,
and the movable member 8 can be positioned at a new location within
the receiver 6 such that the condensing pressure is again
approximately equal to the reference pressure within the chamber
11. This may advantageously be used to operate the system 1 with a
low condensing pressure in order to maximize the efficiency of the
system 1 in converting heat energy to useful work.
[0037] When operation of the Rankine cycle system 1 is suspended,
the working fluid cools down and, eventually, reaches the ambient
temperature. In comparison to when the system is in operation, the
working fluid will have a considerably greater liquid mass fraction
during the non-operative condition. This shift from relatively
low-density vapor to relatively high-density liquid causes a
reduction in the pressure of the working fluid, which is
compensated for by the movable member 8 repositioning itself to be
nearer to the first end cap 13 in response.
[0038] If the charge of working fluid in the system 1 is sufficient
to enable a working fluid pressure in the chamber 10 that is in
equilibrium with the pressure in the chamber 11 without the movable
member 8 reaching the limits of its travel (i.e. by contacting the
first end cap 13 during a non-operative state, or by contacting the
second end cap 14 during an operative state), then the receiver 6
will enable the Rankine cycle system 1 to maintain a desired
working fluid pressure. In an especially preferable embodiment, the
receiver 6 will be able to achieve the foregoing over the full
range of ambient conditions and operating conditions.
[0039] Use of the receiver 6 may especially provide benefit when
the working fluid used in the Rankine cycle system 1 is of a fluid
type that has a sub-atmospheric saturation pressure at expected
ambient temperatures. In a non-operating steady-state condition, a
fraction of the working fluid charge will exist in a vapor state
such that the system pressure is equal to the fluid saturation
pressure corresponding to the fluid temperature. When the fluid
drops to a low temperature, as may be experienced if the system is
outdoors in cold weather, a greater portion of the working fluid
will condense to liquid. If the total volume of working fluid is
fixed, as would be the case in a system 1 lacking the variable
volume receiver 6, this would leave only a small volume of vapor
and, correspondingly, a low system pressure.
[0040] Working fluid pressures that are lower than the surrounding
ambient pressure can be detrimental to the performance of the
system. With positive pressure external to the system, infiltration
of air or other non-condensable gases can occur at the piping
joints along the system. The presence of these non-condensable
gases will degrade the efficiency of the system during operation,
as the working fluid partial pressure will be less than the full
condensing pressure. This will result in a higher condensing
pressure being required to achieve the same condensing temperature,
thus reducing the pressure drop across the expander 3 and,
consequently, reducing the system efficiency.
[0041] Incorporating the variable volume receiver 6 into the system
1 can help to alleviate this problem. The movable member 8 allows
for the volume of the chamber 10 (and, consequently, the total
working fluid volume) to vary. If the system 1 according to the
invention were to be in a non-operating state in a low ambient
temperature environment, the movable member 8 would displace to
reduce the volume of the chamber 10 in response to the reduction in
working fluid pressure. If the pressure in the chamber 11 were to
be maintained at atmospheric pressure (such as by opening the
port(s) 23 to ambient) then the working fluid pressure could be
regulated to atmospheric pressure as well, thereby avoiding a
pressure gradient that would drive non-condensable gases into the
working fluid.
[0042] The desirability of such a Rankine cycle system 1 with
regard to this aspect of the invention can be explained with
reference to FIG. 6, which compares and contrasts the saturation
pressure vs. temperature relationship of R245fa, a typical working
fluid for organic Rankine cycles, to that of R134a, a typical
refrigerant for vapor-compression air conditioning cycles. Whereas
R134a does not reach a saturation temperature that is lower than
the typical atmospheric pressure of 100 kPa until a temperature of
-25.degree. C. (an ambient temperature that is rarely if ever
encountered in most habitable areas of the world), R245fa achieves
the same at a much more moderate temperature of 16.degree. C. When
the variable volume receiver 6 is included in the system 1, the
working fluid can be converted to be entirely liquid at a pressure
equal to that of chamber 11 when the temperature is less than the
saturation temperature at that pressure.
[0043] In order for the foregoing to be readily achievable, it is
highly desirable that the system 1 has a proper charge of working
fluid. In some embodiments, such a proper charge is an amount of
working fluid that, when it is entirely in a liquid state, has a
volume in excess of that which the system 1 would be capable of
accommodating without the receiver 6. In this manner, the working
fluid can be fully condensed to a liquid state while still having
working fluid in the chamber 10. Since liquid fluids are
essentially incompressible, the working fluid in such cases can be
fully condensed (given a sufficiently low temperature) and can be
able to maintain a pressure roughly equivalent to the pressure
within the chamber 11.
[0044] As another aspect of the invention, the variable volume
receiver 6 may provide advantages in charging the Rankine cycle
system 1 with working fluid. In order to ensure a properly charged
system, a regulated pressure can be applied to the chamber 11 as
working fluid is introduced into the system 1. The regulated
pressure applied to the chamber 11 may, for example, be a pressure
greater than the saturation pressure corresponding to the
temperature of the working fluid. Once the space available to the
working fluid outside of the receiver 6 becomes filled, the working
fluid begins to fill the chamber 10 and displaces the movable
member 8. When the movable member 8 reaches a predetermined target
position, the system 1 is properly charged. In some embodiments,
the predetermined target position is a position that provides a
suitable volume in the chamber 10 at a fully condensed liquid
state.
[0045] The shell 12 may advantageously be constructed of a material
that is at least partially transparent, so that the displacement of
the movable member 8 can be directly observed. In this manner, a
direct indication of the working fluid charge level and/or void
fraction can be made available. As an example, the shell 12 can be
constructed of a borosilicate glass. However, in other embodiments
of the invention, displacement of the moveable member 8 can be
indicated in other manners. For example, the position of the
movable member 8 can be indicated using electronic sensors.
[0046] Turning to FIG. 4, an alternate embodiment of the receiver
6' is shown. The shell 12 of the illustrated receiver 6' is a metal
cylinder that is directly and metallurgically attached to the end
caps 13, 14 by welding, brazing, soldering, or the like. The tie
rods 17 and o-rings 19 are not necessary in such a construction,
and have been removed. An indicator ring 24 is provided to allow
for an indication of the position of the movable member 8. The
indicator ring 24 includes magnets 25 arranged along the
circumference, with matching magnets arranged along the
circumference of the movable member 8. The indicator ring 24 and
the shell 12 may be constructed of non-ferrous metals so that the
indicator ring 24 will travel along the receiver 6' in response to
the movement of the movable member 8, thereby indicating the
position of the movable member 8 along the axis of the receiver 6'.
In some embodiments, the indicator ring is constructed of an
aluminum alloy, and the shell 12 is constructed of non-ferrous
stainless steel, but other material combinations may be equally
desirable.
[0047] In some embodiments of the Rankine cycle system 1, the
receiver 6 is connected to a parallel-flow heat exchanger 24
including an integrated air-cooled condenser 5 and sub-cooler 7, as
shown in FIG. 5. The illustrated heat exchanger 24 comprises a
plurality of parallel arranged tubes 31 extending between first and
second headers 29, 30. Corrugated fins 32 are arranged between
adjacent ones of the tubes 31 in order to maintain proper tube to
tube spacing and to provide enhanced heat transfer between the
tubes 31 and air passing over the external surfaces of the tubes
31. Baffles (not shown) within the headers 29, 30 serve to separate
the header internal volume into four separate manifolds, each of
the headers 29, 30 having a first and a second manifold so that the
condenser 5 includes those tubes 31 connecting the first manifold
of the header 29 to the first manifold of the header 30, and the
sub-cooler 7 includes those tubes 31 connecting the second manifold
of the header 29 to the second manifold of the header 30.
[0048] A flow of working fluid enters the first manifold of the
header 29 through fitting 25 as a superheated vapor, and passes
through the condenser 5 to the first manifold of the header 30. The
now liquid working fluid exits the header 30 through fitting 26,
and is routed to port 20 of the receiver 6. Liquid working fluid is
extracted from the receiver 6 through port 21, and is routed to
fitting 27 connected to the second manifold of the header 30. The
working fluid passes through the sub-cooler 7 to the second
manifold of header 29, and is removed from the heat exchanger 24
through a fitting 28 connected to the second manifold of the header
29.
[0049] Various alternatives to certain features and elements of the
present invention are described herein with reference to specific
embodiments of the present invention. With the exception of
features, elements, and manners of operation that are mutually
exclusive of or are inconsistent with each embodiment described
above, it should be noted that the alternative features, elements,
and manners of operation described with reference to one particular
embodiment are applicable to the other embodiments.
[0050] The embodiments described above and illustrated in the
figures are presented by way of example only and are not intended
as a limitation upon the concepts and principles of the present
invention. As such, it will be appreciated by one having ordinary
skill in the art that various changes in the elements and their
configuration and arrangement are possible without departing from
the spirit and scope of the present invention.
* * * * *