U.S. patent application number 12/884491 was filed with the patent office on 2012-03-22 for systems and methods for power generation from multiple heat sources using customized working fluids.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to Sean P. Breen, Ahmad M. Mahmoud, Lance D. Woolley.
Application Number | 20120067049 12/884491 |
Document ID | / |
Family ID | 44905740 |
Filed Date | 2012-03-22 |
United States Patent
Application |
20120067049 |
Kind Code |
A1 |
Woolley; Lance D. ; et
al. |
March 22, 2012 |
SYSTEMS AND METHODS FOR POWER GENERATION FROM MULTIPLE HEAT SOURCES
USING CUSTOMIZED WORKING FLUIDS
Abstract
A power generating system in one embodiment employs a Rankine
Cycle system that is coupled to multiple heat sources. The Rankine
cycle system includes a customized working fluid that comprises a
mixture of a plurality of constituent fluids, the selection of
which causes the mixture to exhibit a working fluid profile. In one
embodiment, the working fluid profile includes a temperature glide
portion selected and optimized based on operating conditions of the
heat sources, wherein the temperature glide portion includes a
constituent phase point at which one of the constituent fluids
undergoes a phase change before the other constituent fluids of the
mixture.
Inventors: |
Woolley; Lance D.;
(Glastonbury, CT) ; Breen; Sean P.; (Holyoke,
MA) ; Mahmoud; Ahmad M.; (Bolton, CT) |
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
44905740 |
Appl. No.: |
12/884491 |
Filed: |
September 17, 2010 |
Current U.S.
Class: |
60/671 ;
60/676 |
Current CPC
Class: |
F01K 25/06 20130101;
F01K 25/10 20130101 |
Class at
Publication: |
60/671 ;
60/676 |
International
Class: |
F01K 25/08 20060101
F01K025/08; F01K 27/00 20060101 F01K027/00 |
Claims
1. A power generating system comprising: a heat source; and a
customized working fluid in heat exchange relation to the heat
source, the customized working fluid comprising a mixture of
constituent fluids, the mixture exhibiting a working fluid profile
comprising at least one constituent phase point at which at least
one of the constituent fluids undergoes a phase change before the
other constituent fluids of the mixture.
2. A power generating system according to claim 1, wherein the
constituent fluids comprise at least one organic fluid.
3. A power generating system according to claim 1, wherein the heat
source comprises a first heat source and a second heat source, and
wherein the customized working fluid exchanges heat with each of
the first heat source and the second heat source.
4. A power generating system according to claim 1, wherein the
working fluid profile includes a constituent phase point for each
of the constituent fluids of the mixture, and wherein the
constituent phase points define different temperatures at which
occur the phase change.
5. A power generating system according to claim 1, further
comprising a heat exchange system coupled to the heat source and in
which flows the customized working fluid, the heat exchange system
comprising at least one of a pump, an evaporator, a condenser, and
a turbine generator.
6. A power generating system according to claim 1, wherein the
mixture comprises a first constituent fluid and a second
constituent fluid, and wherein the constituent phase point
identifies a portion of the working fluid profile at which the
phase change of first constituent fluid is completed before the
phase change of the second constituent fluid.
7. A power generating system according to claim 1, wherein at least
one of the constituent fluids is compatible with operation in a
Rankine cycle system.
8. A power generating system according to claim 1, wherein at least
one of the first constituent fluid and the second constituent fluid
comprises one or more of a hydrofluorocarbon, a hydrocarbon, a
fluorinated ketone, a fluorinated ether, a chloro- and bromo-fluoro
olefin, a hydrofluoroolefins, a hydrofluoroolefin ether, a
hydrochlorofluoroolefin ether, a linear siloxane, a cyclic
siloxane, and combinations and derivations thereof.
9. In a power generating system comprising a first heat source
having a first temperature and a second heat source having a second
temperature that is greater than the first temperature, the power
generating system employing a Rankine cycle system comprising: a
heat exchange system coupled to each of the first heat source and
the second heat source; and a customized working fluid flowing in
the heat exchange system, the customized working fluid comprising a
first constituent fluid and a second constituent fluid, wherein the
first constituent fluid undergoes a phase change before the second
constituent fluid.
10. A system according to claim 9, wherein at least one of the
first constituent fluid and the second constituent fluid is an
organic fluid compatible with the Rankine cycle system.
11. A system according to claim 9, wherein the first constituent
fluid completely vaporizes before the second constituent fluid.
12. A system according to claim 9, wherein the first constituent
fluid completely condenses before the second constituent fluid.
13. A system according to claim 9, wherein the heat exchange system
comprises at least one of a pump, an evaporator, a condenser, and a
turbine generator.
14. A system according to claim 9, wherein the first constituent
fluid and the second constituent fluid comprise a compound that is
selected from the group consisting of propane, cyclopropane,
isobutene, isobutane, n-butane, propylene, n-pentane, isopentane,
cyclopentane, R-134a, R-30, R-32, R-123, R-125, R-143a, R-134,
R-152a, R-161, R-1216, R-227ea, R-245fa, R-245cb, R-236ea, R-236fa,
R-365mfc, HT-55, R-43-10mee, HFE-7000, Novec-649, CF.sub.3I, R-1234
(ye and yf), R-1234ze, R-1233 (zd(E) and zd(Z)), R-1225 (ye(Z) and
ye(E)), C.sub.5F.sub.9Cl, C.sub.5H.sub.2F.sub.10, R-1243zf, E-134a,
E134, E125, E143a, siloxane MM, dimethylether, and CO.sub.2, and
combinations and derivations thereof.
15. A system comprising: a plurality of heat sources; a power
generator coupled to each of the plurality of heat sources; and a
plurality of customized working fluids flowing in the power
generator, wherein each of the customized working fluids comprises
a mixture of a plurality of constituent fluids, and wherein the
mixture exhibits a working fluid profile with at least one
constituent phase point at which one of the plurality of
constituent fluids undergoes a phase change before any of the other
of the plurality of constituent fluids.
16. A system according to claim 15, wherein the power generator
comprises a plurality of heat exchange systems that flow the
customized working fluid in heat transfer relation to the heat
sources.
17. A system according to claim 15, wherein the constituent fluids
comprise one or more of a hydrofluorocarbon, a hydrocarbon, a
fluorinated ketone, a fluorinated ether, a chloro-fluoro olefin, a
bromo-fluoro olefin, a hydrofluoroolefin, a hydrofluoroolefin
ether, a hydrochlorofluoroolefin ether, a linear siloxane, a cyclic
siloxane, and combinations and derivations thereof.
18. A system according to claim 15, wherein the first constituent
fluid and the second constituent fluid comprise compounds selected
from the group consisting of propane, cyclopropane, isobutene,
isobutane, n-butane, propylene, n-pentane, isopentane,
cyclopentane, R-134a, R-30, R-32, R-123, R-125, R-143a, R-134,
R-152a, R-161, R-1216, R-227ea, R-245fa, R-245cb, R-236ea, R-236fa,
R-365mfc, HT-55, R-43-10mee, HFE-7000, Novec-649, CF.sub.3I, R-1234
(ye and yf), R-1234ze, R-1233 (zd(E) and zd(Z)), R-1225 (ye(Z) and
ye(E)), C.sub.5F.sub.9Cl, C.sub.5H.sub.2F.sub.10, R-1243zf, E-134a,
E134, E125, E143a, siloxane MM, dimethylether, and CO.sub.2, and
combinations and derivations thereof.
Description
TECHNICAL FIELD
[0001] The subject matter of the present disclosure relates
generally to closed loop Rankine cycle power systems, and in one
embodiment to a power system that comprises a customized working
fluid configured as a mixture of constituent fluids, wherein the
mixture is customized to the heat streams of the system.
BACKGROUND
[0002] Rankine cycle power systems and in particular organic
Rankine cycle ("ORC") systems are used for the purpose of
generating electrical power. These systems implement a vapor power
cycle that utilizes an organic fluid as the working fluid instead
of water/steam. Functionally these ORC systems resemble the steam
cycle power plant, in which a pump increases the pressure of the
condensed working fluid, the condensed working fluid is vaporized,
and the vaporized working fluid interacts with a turbine to
generate power.
[0003] Implementation of these systems is useful to harness waste
energy in many forms including geothermal wells and waste heat
generated by industrial and commercial processes and operations.
Other sources of waste heat include biomass boilers, engine cooling
systems, and industrial cooling processes. However, because such
configurations of ORC systems generally use single constituent
working fluids with particularly well defined "pinch points," or
point in the temperature profile where the difference between the
temperature of the working fluid and the heat source is smallest,
the range of temperatures with which these conventional ORC systems
exchange heat is limited. The limiting effect of the pinch point is
particularly important in implementations wherein the ORC system is
used to generate power with heat from multiple sources, and more
particularly from multiple sources at disparate operating
temperatures.
[0004] To address the issues with the pinch point, and thus improve
efficiency, conventional solutions may utilize heat transfer
systems for each of the heat sources. While effective in that the
individual heat transfer systems can be customized to the specific
heat source, such solutions are limited to transfer heat at the
temperature prescribed by the properties of the working fluid.
These properties include the pinch point at which temperature of
the working fluid rises quickly to the vaporization point and then
the remaining heat is transferred in the working fluid at one
temperature.
[0005] Other solutions are also available in which the working
fluid is manipulated to control the thermal characteristics of the
working fluid. These characteristics can influence the ratio of the
heat transferred at a variety of temperatures, which permits better
temperature driven heat transfer and simplifies the heat transfer
system. Such solutions require manipulation of the chemical
compounds and composition of the working fluid. But in addition to
requiring extensive research to understand and manufacture the
resulting working fluid, the manipulation of chemical compounds to
formulate new and exotic working fluids does not address the
fundamental problem. That is, although the working fluid is
appropriate for the specific heat sources for which it was
designed, the resulting working fluid still has a tight single
instance pinch point, which will limit its further application in
connection with other heat sources or combination of heat sources
and flexibility during off design operation of the equipment.
[0006] There is a need for systems to generate power from multiple
heat sources, but that utilize the advantages of a single circuit
ORC system despite the disparate temperature between the multiple
heat streams. There is likewise a need for a working fluid and/or a
system employing such working fluid that address the problems and
limitations associated with the fluid pinch point, the effect the
thermodynamic limitations of the pinch point has on determining the
specific ratio of energy that is transferable from each of the
various heat sources, and the impact of this ratio has on
efficiency, optimization, and utilization of resources to generate
power from multiple heat sources.
SUMMARY
[0007] There is described below in accordance with the present
disclosure embodiments of systems and power generating systems that
utilize a customized working fluid that comprises a mixture of
working fluids including, but not limited to, organic fluids used
in ORC systems. The content of the mixture, e.g., the selection of
the working fluids, is configured so as to provide the customized
working fluid with thermodynamic properties conducive to heat
transfer from the multiple sources, and in one example each of the
multiple sources is at their existing nominal operation points.
Each of the working fluids, however, retain their initial chemical
properties, thereby simplifying the implementation of the resultant
customized working fluid and the control of the specific
mixture.
[0008] Further discussion of these and other features is provided
below in connection with one or more embodiments, examples of which
appear immediately below:
[0009] In one embodiment, a power generating system comprises a
heat source and a customized working fluid in heat exchange
relation to the heat source. The customized working fluid comprises
a mixture of a plurality of constituent fluids. In one example the
mixture exhibits a working fluid profile comprising at least one
constituent phase point at which at least one of the constituent
fluids undergoes a phase change before the other constituent fluids
of the mixture.
[0010] In another embodiment, in a power generating system that
comprises a first heat source having a first temperature and a
second heat source having a second temperature that is greater than
the first temperature, the power generating system employs a
Rankine cycle system. The Rankine cycle system comprises a heat
exchange system coupled to each of the first heat source and the
second heat source and a customized working fluid flowing in the
heat exchange system. The customized working fluid comprises a
first constituent fluid and a second constituent fluid. In one
example, the first constituent fluid undergoes a phase change
before the second constituent fluid.
[0011] In yet another embodiment, a system comprises a plurality of
heat sources, a power generator coupled to each of the plurality of
heat sources, and a plurality of customized working fluids flowing
in the power generator. In one example, each of the customized
working fluid comprises a mixture of a plurality of constituent
fluids. In another example, the mixture exhibits a working fluid
profile with at least one constituent phase point at which one of
the plurality of constituent fluids undergoes a phase change before
any of the other of the plurality of constituent fluids.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above recited concepts of
the present disclosure may be understood in detail, a more
particular description is provided by reference to the embodiments,
which are illustrated in the accompanying drawings. It is to be
noted, however, that the appended drawings illustrate only typical
embodiments and are therefore not to be considered limiting of its
scope, for the concepts of the present disclosure may admit to
other equally effective embodiments. Moreover, the drawings are not
necessarily to scale, emphasis generally being placed upon
illustrating the principles of certain embodiments.
[0013] Thus, for further understanding of these concepts and
embodiments, reference may be made to the following detailed
description, read in connection with the drawings in which:
[0014] FIG. 1 is a schematic diagram of an example of an ORC system
that is made in accordance with concepts of the present disclosure;
and
[0015] FIG. 2 is a temperature-enthalpy phase diagram that
illustrates a working fluid profile for another example of an ORC
system of the present disclosure.
DETAILED DESCRIPTION
[0016] Broadly stated, embodiments of the present disclosure are
useful to convert thermal energy to mechanical energy and further
to electrical energy by way of closed loop Rankine cycle systems,
e.g., Organic Rankine Cycle ("ORC") systems and related technology.
These heat transfer systems employ working fluids that allow their
use in heat to mechanical conversions. Such working fluids in the
embodiments discussed below are particularly customized to the heat
sources and related processes to which is coupled the heat transfer
system. This custimization can occur in the form of formulated
mixtures of constituent fluids, which comprise organic and
inorganic compounds such as refrigerants for use in ORC systems.
The constituent fluids are mixed such as at relative percentages
and weights, wherein the resulting mixture has thermodynamic
properties that optimize the efficiency of heat transfer between
the working fluid and the heat sources, and ultimately the amount
of power generated.
[0017] However, the mixture of constituent fluids is provided so
that each of the constituent fluids substantially retains its
physical and chemical properties in the mixed fluids. That is the
mixture of organic fluids is a product of mechanical blending,
without chemical bonding or other chemical changes as among and
between the organic fluids in the mixture. Each ingredient
substance thus retains its own chemical properties and makeup.
[0018] In one embodiment, the inventors propose customized working
fluids in which the selection and mixture of a plurality of
constituent fluids result in a working fluid profile (e.g., as
defined by a temperature-enthalpy diagram (T-H diagram)) without
the characteristic pinch point(s) of conventional
single-constituent working fluids. The mixture is formulated so
that, in place of the pinch point, there is found a temperature
glide portion in which changes in the temperature of the working
fluid occur gradually during the thermodynamic cycle. More
particular to one example, the temperature glide portion comprises
at least one operating temperature wherein one of the constituent
fluids undergoes a phase change (e.g., from a liquid phase to a
vapor phase) before the other constituent fluids of the mixture.
Details of this and other concepts are provided in the discussion
that follows below.
[0019] Referring now to FIG. 1, there is shown a schematic
illustration of a system 100 that is made in accordance with
concepts of the present disclosure. The system 100 includes a heat
exchange system 102 and a heat source 104 coupled in thermal
relation to the heat exchange system 102. This coupling permits the
heat exchange system 102 to capture heat from the heat source 104,
and in one construction the captured heat is transformed into power
such as by way of a mechanical expander (e.g., a turbine). The heat
source 104 comprises a low temperature or first source 106 and a
high temperature or second source 108. Each of the first source 106
and the second source 108 exhibit an operating temperature,
generally identified in the present example as T.sub.1 and T.sub.2.
While two heat sources are schematically illustrated in the
disclosed non-limiting embodiment, it should be understood that the
disclosure is applicable to multiple sources (more than two (2)
sources) systems.
[0020] In one embodiment, the heat exchange system 102 comprises a
fluid circuit 110 through which flows a customized working fluid
112. Examples and construction of the fluid circuit 110 can vary,
however those familiar with Rankine cycle systems will generally
recognize that the customized working fluid 112 flows amongst
various components of the fluid circuit 110, some of which are
discussed in more detail below. Here the fluid circuit 110
comprises a turbine generator 114, a pump 116, and a condenser 118.
These components are typically coupled together as closed-loop
systems, which are substantially hermetically sealed from the
environment.
[0021] Related to the operation of systems such as the system 100,
the fluid circuit 110 is configured to flow the customized working
fluid 112 among the first source 106 and the second source 108.
This flow facilitates heat transfer to and from the customized
working fluid 112 and one or more of the first source 106 and the
second source 108. The transfer of heat effectuates changes in the
temperature of the customized working fluid 112. These changes are
influenced by the configuration of the system 100, and in the
present example heat transfer is influenced by the operating
temperatures of the first source 106 and the second source 108
(e.g., operating temperatures T1 and T2). In one example, the
system 100 is configured for pre-heating of the customized working
fluid 112 at the first source 106 and vaporizing of the customized
working fluid 112 at the second source 108. In another example, the
system 100 is configured for pre-heating of the customized working
fluid 112 at the first source 106, partial vaporizing of the
customized working fluid 112 at the first source 106, and complete
vaporizing of the customized working fluid 112 at the second source
108. In yet another example, the system 100 is configured for
partial pre-heating of the customized working fluid 112 at the
first source 106 and partial pre-heating and complete vaporizing of
the customized working fluid 112 at the second source 108.
Super-heating of the customized working fluid 112 is likewise
possible such as in one or more of the examples above where the
customized working fluid 112 is superheated in the second source
108. Other configurations of the system 100 are also contemplated
in which occurs super-critical heating of the customized working
fluid 112.
[0022] The customized working fluid 112 passes to the turbine
generator 114, thereby providing mechanical power to generate,
e.g., electricity. Upon leaving the turbine generator 114, the
vapor passes next to the condenser 118 wherein the vapor is
condensed by way of heat exchange relationship with a cooling
medium (not shown). The resulting working fluid, now substantially
condensed as liquid, is then circulated by the pump 116 to the
first source 106, which is at an operating temperature T.sub.1.
This essentially completes the cycle of the system 100.
[0023] The heat source 104, including each of the first source 106
and the second source 108, is generally instantiated by heat
rejection devices that exhibit heat streams of varying
temperatures. Suitable heat streams are found, for example, in
internal combustion engines (ICE) by way of, but not limited to,
the exhaust gas, charge air cooler, and the jacket water. Other
heat streams can be found in renewable power sources such as fuel
cells, solar, and geothermal applications. Combinations (e.g.,
solar applications in combination with geothermal applications) and
derivations of these and other devices, systems, and the like are
also contemplated within the scope and spirit of the present
disclosure.
[0024] Flowing the customized working fluid 112 in heat transfer
relation to these devices facilitates the exchange of heat. This
exchange, as discussed above, can optimize the heat recovery of the
system 100 and boost power generation of, e.g., the Rankine cycle
system. To optimize the system 100, for example, the inventors have
discovered that the customized working fluid 112 can be configured
to match the operating conditions of the heat source 104, e.g., the
operating temperature T.sub.1 of the first source 106 and the
operating temperature T.sub.2 of the second source 108.
[0025] Such configuration can be in the form of a mixture of
constituent fluids such as, but not limited to, organic fluids used
as the working fluid in ORC systems. In one embodiment, the
constituent fluids of the mixture are selected based on parameters
of the system 100. These parameters include the operating
temperatures T.sub.1 and T.sub.2, desired heat recovery rates as
between the resulting customized working fluid 112 and the heat
source 104, desired power generation for the system 100, and other
functional parameters, which will be recognized by those artisans
with skill in the field of this disclosure.
[0026] By way of example, mixtures for use as the customized
working fluid 112 can comprise a plurality of constituent fluids
such as a first fluid and a second fluid. These constituent fluids
can be mixed together, with the amount (e.g., as a percentage
and/or fraction of the whole) of each of the first fluid and the
second fluid determined in accordance with the operating
temperatures T.sub.1 and T.sub.2. The resulting customized working
fluid 112 is compatible with operating temperatures for a low
temperature (e.g., the first source 106) and for a high temperature
(e.g., the second source 108). In one embodiment, the first fluid
undergoes a phase change (e.g., from a liquid phase to a vapor
phase) before the second fluid. While two heat sources are
schematically illustrated in the disclosed non-limiting embodiment,
it should be understood that the disclosure is applicable to
multiple sources (more than two (2) sources) systems.
[0027] With continued focus on the customized working fluid, and
with reference now to FIG. 2, there is illustrated an operating
profile 200 for an example of a customized working fluid (e.g., the
customized working fluid 112 (FIG. 1)) of the present disclosure.
The operating profile 200 is in the form of a T-H diagram (i.e., a
temperature-enthalpy diagram) on which is illustrated a
thermodynamic cycle 202. Superimposed on the thermodynamic cycle
202 is a set of temperature profiles, generally identified by 204,
and which include a cooling profile 206, a first profile 208, and a
second profile 210. The first profile 208 and the second profile
210 are indicative of the heat source with which heat is exchanged
with the customized working fluid. When considered in view of the
example of FIG. 1, the first profile 208 and the second profile 210
are consistent with, respectively, the first source 106 and the
second source 108 of the system 100. Each of the first profile 208
and the second profile 210 include a maximum temperature and a
minimum temperature, as well as a temperature difference that is
measured therebetween. In the present example, the cooling profile
206 includes a minimum temperature 212 and a maximum temperature
214. Likewise the first profile 208 (e.g., the first high
temperature profile) includes a minimum temperature 216 and a
maximum temperature 218 and the second profile 210 (e.g., the
second higher temperature profile) includes a minimum temperature
220 and a maximum temperature 222.
[0028] Also depicted in FIG. 2 is a working fluid profile 224 that
includes one or more temperature glide portions 226. In the present
example, the temperature glide portions 226 include an evaporator
glide portion 228 and a condenser glide portion 230. Each of the
temperature glide portions 226 comprises a constituent phase point
232, at which at least one of the constituent fluids of the mixture
undergoes a phase change. By way of example, but not limitation,
the evaporator glide portion 228 comprises a constituent
vaporization point 234 and the condenser glide portion 230
comprises a constituent condensation point 236. In one example, the
constituent vaporization point 234 identifies the operating
conditions in which at least one of the constituent fluids of the
mixture is completely vaporized. In another example, the
constituent condensation point 236 identifies the operating
conditions in which at least one of the constituent fluids of the
mixture is completely condensed.
[0029] The number and location of the constituent phase points 232
can vary as with, for example, the number of constituent fluids
that are mixed together to form the customized working fluids of
the present disclosure. The example that is depicted in FIG. 2 is
indicative of a mixture of two constituent fluids, wherein one of
the constituent fluids undergoes a phase change before the other.
It is contemplated that for mixtures of, e.g., three constituent
fluids, each of the temperature glide portions 226 may comprise
constituent phase points 232 that identify the operating conditions
at which each of the constituent fluids undergo the phase change.
In one embodiment, fluids such as organic fluids are selected and
mixed together in particular percentages to yield initial and final
temperatures for the temperature glide portions 226, as well as the
location of the constituent phase points 232. The combination of
constituent fluids can be used to define the slope and or profile
of the temperature glide portions 226. This combination is useful
to reduce and/or eliminate the pinch points that are typical of
conventional single constituent working fluids. These percentages
may take into consideration characteristics, e.g., the temperature,
of the cooling source 206 and the first profile 208 and the second
profile 210, thereby allowing heat recovery with a single
customized working fluid from each of the first source 106 (FIG. 1)
and the second source 108 (FIG. 1) discussed above.
[0030] Manipulation of the working fluid profile 224 by way of the
mixture (e.g., the percentages of the constituent fluids) is
beneficial because it provides better matching in systems in which
the heat source is defined by one or more of the first high
temperature profile 208 and the second higher temperature profile
210. For example, the mixture of constituent fluids can be selected
so as to define the characteristics, e.g., the slope and/or arc, of
one or more of the evaporator glide portion 228 and/or the
condenser glide portion 230. Such characteristics can be used to
promote efficient heat exchange, and in one implementation the
mixture is tuned so that the evaporator glide portion 228 is in the
temperature range of at least one of the first high temperature
profile 208 and the second higher temperature profile 210.
[0031] Referring back to FIG. 2, it is seen that the working fluid
profile 224 also includes several process stages, identified
generally by the numerals 238, 240, 242, 244, 246, 248, 250, and
252 (collectively, "process stages"). These process stages describe
the various states of the customized working fluid as the
customized working fluid flows through the system, e.g., the system
100. By way of the process stages and in consideration of the
Rankine cycle system generally, an exemplary embodiment of a method
of generating power using the customized working fluid is described
below.
[0032] In one embodiment of the method, the customized working
fluid is pre-heated from stage 238 to stage 240 such as by way of
heat transfer from the low temperature or first source (e.g., the
first source 106). The customized working fluid is then evaporated,
from stage 240 to stage 242, when introduced to the high
temperature or second source (e.g., the second source 108). As
discussed above, complete vaporization of the constituent fluids
that comprise the customized working fluid can occur variously,
such as at one or more of the constituent vaporization points 234.
In one example, the mixture of the constituent components causes
vaporization of a first fluid from stage 240 to the constituent
vaporization point 234 and then vaporization of a second fluid,
such as by normal latent heating, from the constituent vaporization
point 234 to stage 242. Communication between the fluid and the
second source can likewise superheat the vaporized customized
working fluid, as illustrated in the working fluid profile 224 from
stage 242 to stage 242. The vapor is thereafter expanded between
stage 244 and stage 246, de-superheated between stage 246 and stage
248, and condensed between stage 248 and stage 250. As with the
evaporative portion of the working fluid profile 224 discussed
above, complete condensation of the constituent fluids that
comprise the customized working fluid can occur at one or more of
the constituent condensation points 236. In one example, the
mixture of the constituent components causes condensation of a
first fluid from stage 248 and constituent condensation point 236
and then condensation of a second fluid from constituent
condensation point 236 to stage 250. Sub-cooling can occur between
stage 250 and stage 252, before the customized working fluid is
reflowed in proximity to the first source.
[0033] Noted is that the composition of the customized working
fluid, e.g., the mixture of organic fluids, can be tuned to provide
appropriate and adequate initial and final temperatures for the
temperature glide portion 226 so as to facilitate one or more of
the process stages and steps discussed above. Varying the
combinations of organic fluids can change the working fluid profile
224 so that the process stages occur at different temperatures and
pressures. In one example, such variations can promote and improve
pre-heating (e.g., from stage 238 to stage 240) by matching the
customized working fluid to the temperatures of the heat
sources.
[0034] For further clarification, instruction, and description of
the concepts above, embodiments of the present disclosure are now
illustrated and discussed in connection with the following
examples:
Example I
[0035] In one example, a customized working fluid comprises
compounds such as, but not limited to, hydrofluorocarbons,
hyrocarbons, fluorinated ketones, fluorinated ethers, chloro- and
bromo-fluoro olefins, hydrofluoroolefins, hydrofluoroolefin ethers,
hydrochlorofluoroolefin ethers, and linear and/or cyclic siloxanes.
By way of illustration, these compounds can be further defined as
one or more of propane, cyclopropane, isobutene, isobutane,
n-butane, propylene, n-pentane, isopentane, cyclopentane, R-134a,
R-30, R-32, R-123, R-125, R-143a, R-134, R-152a, R-161, R-1216,
R-227ea, R-245fa, R-245cb, R-236ea, R-236fa, R-365mfc, HT-55,
R-43-10mee, HFE-7000, Novec-649, CF.sub.3I, R-1234 (ye and yf),
R-1234ze, R-1233 (zd(E) and zd(Z)), R-1225 (ye(Z) and ye(E)),
C.sub.5F.sub.9Cl, C.sub.5H.sub.2F.sub.10, R-1243zf, E-134a, E134,
E125, E143a, siloxane MM, dimethylether, and CO.sub.2. Still other
compounds, though not necessarily listed above, can be selected
that have characteristics that can enhance system performance,
enhance heat transfer characteristics, provide fire suppression,
provide flame retardation, provide lubrication, provide compound
stabilization, provide corrosion inhibition, as well as provide
solubility compatibility, tracing, prognostics or diagnostics.
Example II
[0036] In another example, a customized working fluid is configured
to utilize available energy from multiple heat sources generated by
an internal combustion engine. The temperature of first said heat
source, the higher of the two available sources, is about
90.5.degree. C. (195.degree. F.) and experiences a temperature drop
of about 25-30.degree. C. throughout the evaporator of an
embodiment of an ORC system (e.g., the system 100 (FIG. 1)). The
temperature of the second said heat source, the lower of the two
available sources, is about 71.degree. C. (160.degree. F.) and
experiences a temperature drop of about 20-25.degree. C. throughout
the pre-heater/evaporator of an embodiment of an ORC system (e.g.,
the system 100 (FIG. 1)).
[0037] As discussed above, implementation of the concepts
contemplated herein may define the amount of heat available from
the two heat sources as well to dictate whether pre-heating,
evaporation, or superheat, will occur in the ORC system design. In
one implementation, the cooling water inlet temperature and cooling
water outlet temperature to the condenser dictate the maximum
allowable temperature glide of the customized working fluid. This
characteristic will allow for matching of multiple heat
sources.
[0038] To illustrate, the customized working fluid of the present
example can comprise a binary mixture of about 40% isobutene and
about 60% isopentane (by mass fraction). This customized working
fluid is designed for an embodiment of an ORC system (e.g., system
100) in which the pinch point in the evaporator is assumed to be
about 5.6.degree. C. (10.degree. F.). This assumption defines the
bubble temperature of the mixture of the customized working fluid
at the high-side pressure be about 65-67.5.degree. C.
(150-154.degree. F.). Table 1 lists the temperature variation
throughout the ORC system using the customized working fluid of the
present example.
TABLE-US-00001 TABLE 1 Working Fluid Temperature Location .degree.
C. .degree. F. Pump Inlet 5.6 42.1 Pump Outlet 6.1 43.0 Evaporator
Inlet 6.1 43.0 Evaporator Bubble Point 66.1 151.0 Evaporator Dew
Point 76.7 170.0 Turbine Inlet 76.7 170.0 Turbine Exit 44.0 111.2
Condenser Inlet 44.0 111.2 Condenser Outlet 5.6 42.1
[0039] While an example of a customized working fluid has been
described with respect to this specific implementation, those
skilled in the art will appreciate that there are numerous
variations and permutations of the above described systems and
customized working fluids that fall within the spirit and scope of
the present disclosure.
[0040] Further, it is contemplated that numerical values, as well
as other values that are recited herein are modified by the term
"about", whether expressly stated or inherently derived by the
discussion of the present disclosure. As used herein, the term
"about" defines the numerical boundaries of the modified values so
as to include, but not be limited to, tolerances and values up to,
and including the numerical value so modified. That is, numerical
values may include the actual value that is expressly stated, as
well as other values that are, or may be, the decimal, fractional,
or other multiple of the actual value indicated, and/or described
in the disclosure.
[0041] While the present disclosure has shown and described details
of exemplary embodiments, it will be understood by one skilled in
the art that various changes in detail may be effected therein
without departing from the spirit and scope of the disclosure as
defined by claims that may be supported by the written description
and drawings. Further, where these exemplary embodiments (and other
related derivations) are described with reference to a certain
number of elements it will be understood that other exemplary
embodiments may be practiced utilizing either less than or more
than the certain number of elements.
* * * * *