KR101345106B1 - Heat engine based on transcritical rankine cycle with improved exergy efficiency and method thereof - Google Patents

Abstract

A Rankine cycle is disclosed that condenses and cools the working fluid flowing out of the turbine, compresses the condensed and cooled working fluid, and heat exchanges the compressed working fluid with a lower heat source. As a result, exergy efficiency is improved.

Description

HEAT ENGINE BASED ON TRANSCRITICAL RANKINE CYCLE WITH IMPROVED EXERGY EFFICIENCY AND METHOD THEREOF}

The present invention relates to a transcritical Rankine cycle heat engine having improved exergy efficiency and a method thereof.

Recently, there has been a growing interest in cycles of heat engines utilizing all possible heat sources, including next-generation reactors, solar, fossil, or biofuels. Supercritical CO ₂ cycles, for example, have high efficiency and compact advantages over conventional steam-based Rankine cycles or helium-based Brayton cycles.

1, 2, and 5 are views for explaining a Rankine cycle heat engine using a conventional CO ₂ .

Referring to these drawings, when describing a Rankine cycle heat engine using conventional CO ₂ (hereinafter referred to as 'carbon dioxide'), a Rankine cycle heat engine using conventional carbon dioxide works while adiabaticly expanding carbon dioxide, which is a working fluid, and a recuperator. A condenser for condensing and cooling the working fluid, a pump for compressing the working fluid, and a heater.

The recuperator heat-exchanges the working fluid discharged from the turbine and the working fluid compressed and discharged by the pump, and the heater exchanges the working fluid and the high heat source which have exchanged heat by the recuperator, and then flows out to the turbine. do.

The working fluid circulating in the Rankine cycle in FIG. 1 is subjected to temperature and pressure changes as indicated in FIGS. 2 and 5. On the other hand, for convenience of understanding the temperatures on each of the conduits (0, 1, 2, 3, 4, 5) shown in Figure 1 are shown in Figures 2 and 5.

That is, the working fluid flowing out of the turbine has a temperature of T ₄ , and the heat quantity of Q _R (449.0 kJ / kg) of the working fluid is transmitted to the working fluid flowing out by the pump while passing through the recuperator. Thereafter, the working fluid discharged from the recuperator is condensed and cooled by the condenser to become a working fluid having a temperature of T ₀ (20 ° C.). This process wastes as much as Q _L + Q _C (70.7 + 152.0 kJ / kg).

A working fluid with a temperature of T _O (20 ° C) is compressed by a pump to have a temperature of T ₁ (39 ° C), which is then supplied with a calorific value of Q _R (449.0 kJ / kg) in the recuperator, It goes up to T2 (298 ° C). The working fluid whose temperature has risen to T2 (298 ° C.) again receives heat from an external heat source in the heater and rises to T3 (600 ° C.).

As described above, the conventional Rankine cycle heat engine using CO ₂ has a temperature T3 in which the working fluid in the compressed state T1 can work (eg, Q _H = 373.1). kJ / kg) should be supplied relatively more than the Brayton cycle heat engine described later.

3, 4, and 6 are views for explaining a heat engine operating in a conventional Brayton cycle mode.

Referring to these drawings, a conventional Brayton cycle heat engine using carbon dioxide will be described. A conventional Brayton cycle heat engine using carbon dioxide cools a turbine, a recuperator, and a working fluid while adiabaticly expanding working fluid carbon dioxide. , A compressor for compressing the working fluid, and a heater.

The recuperator heat exchanges the working fluid discharged from the turbine and the working fluid compressed and discharged by the compressor, and the heater exchanges heat between the working fluid and the high heat source, which are exchanged by the recuperator, and then flows out to the turbine. do.

The working fluid circulating in the Rankine cycle in FIG. 3 is subjected to temperature and pressure changes as indicated in FIGS. 4 and 6. On the other hand, for convenience of understanding the temperatures on each of the conduits (0, 1, 2, 3, 4, 5) shown in Figure 3 are shown in Figures 4 and 6.

That is, the working fluid flowing out of the turbine has a temperature of T ₄ (449 ° C.), and the heat quantity of Q _R (355.5 kJ / kg) of the working fluid flowing through the recuperator is transferred to the working fluid flowing out of the pump. Delivered. Thereafter, the working fluid flowing out of the recuperator is cooled by a cooler to become a working fluid having a temperature of T ₀ (20 ° C.). In the process, Q _L of heat (164.2 kJ / kg) is discarded.

A working fluid with a temperature of T _O (20 ° C.) is compressed by a compressor to have a temperature of T ₁ (115 ° C.), which is then supplied with a calorific value of Q _R (355 kJ / kg) in the recuperator, so that the temperature is T 2. It goes up to (370 ° C). The working fluid whose temperature has risen to T2 (370 ° C.) is again heated up to T3 (600 ° C.) by receiving heat (283.6 kJ / kg) from an external heat source in the heater.

As described above, since the Brayton cycle heat engine using CO ₂ has a process of compressing directly in a gas state, energy efficiency is better than that of the Rankine cycle heat engine described above, but the compression power is higher than that of the Rankine cycle heat engine. There are disadvantages.

According to one embodiment of the inventive concept, a transcritical Rankine cycle with improved exergy efficiency is provided.

According to another embodiment of the inventive concept, a transcritical Rankine cycle based heat engine with improved exergy efficiency is provided.

According to another embodiment of the inventive concept, a method of increasing the exergy efficiency of a heat engine is provided.

According to another embodiment of the inventive concept, a method of operating a heat engine with improved exergy efficiency is provided.

According to an exemplary embodiment of the inventive concept, a Rankine cycle for a heat engine, comprising: condensing and cooling a working fluid exiting a turbine; Compressing the condensed and cooled working fluid; A first heat exchange step of exchanging the compressed working fluid with a lower heat source; And a second heat exchange step of exchanging heat with the working fluid that has passed through the first heat exchange step before condensing and cooling the working fluid that flows out of the turbine. It includes, and the Rankine cycle is improved exergy efficiency, characterized in that the working fluid passed through the first heat exchange step and the second heat exchange step is introduced into the turbine.

The working fluid may be carbon dioxide.

The Rankine cycle according to an exemplary embodiment of the present inventive concept may include: a third heat exchange step of exchanging heat with the working fluid compressed by the compressing step before condensing and cooling the working fluid passed through the second heat exchange step; Further comprising, the working fluid that has passed through the first heat exchange step, the second heat exchange step, and the third heat exchange step may be introduced into the turbine.

According to an exemplary embodiment of the inventive concept, a steam cycle based heat engine, comprising: a turbine for outflow of a working fluid; A condenser for condensing and cooling the working fluid discharged from the turbine; A pump for compressing the condensed and cooled working fluid; A first recuperator for exchanging the compressed working fluid with a lower heat source; And a second recuperator for exchanging the working fluid from the turbine and before flowing into the condenser with the working fluid heat exchanged by the first recuperator. It includes, and is provided with a steam cycle-based heat engine, characterized in that the working fluid which has undergone heat exchange by the first and second recuperator flows into the turbine.

The first accumulator may also be configured to heat exchange the working fluid before the heat exchange by the second recuperator and flowing into the capacitor, with the working fluid compressed by the pump.

According to an exemplary embodiment of the inventive concept, a turbine is operated by a working fluid; A condenser for condensing and cooling the working fluid flowing out of the turbine; A pump for compressing the working fluid condensed and cooled by the condenser; A first conduit providing a path through which the working fluid flowing out of the turbine can move to the capacitor; A second conduit providing a path through which the working fluid flowing out of the pump can move to the turbine; A first recuperator heat-exchanging a working fluid and a low heat source moving through the second pipe; And a second recuperator disposed between the first recuperator and the turbine and exchanging a working fluid flowing through the first pipe line and a working fluid flowing through the second pipe line. .

According to an exemplary embodiment of the inventive concept, a heat engine operating in Brayton cycle mode and Rankine cycle mode, comprising: a turbine working by a working fluid; A direction changer for flowing the working fluid flowing out of the turbine to either the capacitor or the compressor; And a first recuperator for exchanging heat between the working fluid and the heat storage fluid before flowing to the condenser or the compressor. The working fluid flowing out of the condenser or the compressor may be introduced into the turbine.

The heat engine according to an exemplary embodiment of the inventive concept may further include a heat storage unit for storing the heat storage fluid.

In the Brayton cycle mode, the direction switching unit may be to convert the working fluid flowing out of the turbine to flow to the compressor.

A heat engine according to an exemplary embodiment of the present invention concept further includes a cooler disposed between the turning part and the compressor, wherein the cooler cools the working fluid by receiving the working fluid from the turning part. It may be leaking.

In the Rankine cycle mode, the diverter may convert the working fluid flowing out of the turbine to flow to the capacitor.

The heat engine according to an exemplary embodiment of the present invention concept may further include a pump for compressing the working fluid flowing out of the condenser.

In the Rankine cycle mode, the first recuperator may exchange heat between the working fluid before flowing to the condenser or the compressor, the heat storage fluid stored in the heat storage unit, and the working fluid flowing out of the pump.

The heat engine according to an exemplary embodiment of the inventive concept may further include a second recuperator configured to exchange heat between the working fluid before flowing into the first recuperator and the working fluid flowing out of the condenser or the compressor. It may be.

According to an exemplary embodiment of the present inventive concept, a method of increasing the exergy efficiency of a heat engine including a turbine, a compressor, and a condenser, wherein a working fluid flowing out of the turbine flows to the compressor in a Brayton cycle mode. Direction switching to flow to the capacitor in a Rankine cycle mode; In the Brayton cycle mode, heat exchanging the working fluid and the heat storage fluid before flowing to the compressor; And introducing a working fluid flowing out of the condenser or the compressor into the turbine.

The method of increasing the exergy efficiency of a heat engine according to an exemplary embodiment of the present inventive concept may further include storing the heat storage fluid in the Brayton cycle mode.

A method of increasing the exergy efficiency of a heat engine according to an exemplary embodiment of the present inventive concept may include cooling the working fluid before entering the compressor in a Brayton cycle mode.

The method of increasing the exergy efficiency of a heat engine according to an exemplary embodiment of the inventive concept may further include compressing the working fluid flowing out of the condenser into a pump in a Rankine cycle mode.

A method of increasing the exergy efficiency of a heat engine according to an exemplary embodiment of the present invention includes a heat storage fluid stored in the Brayton cycle mode and a working fluid compressed and discharged by the pump in a Rankine cycle mode. Heat exchange step; may be to include more.

A method for increasing the exergy efficiency of a heat engine according to an exemplary embodiment of the present inventive concept, in a Rankine cycle mode, includes mutually heat-exchanging a working fluid before flowing to the condenser and a working fluid compressed and discharged by the pump. It may be to include a; more.

According to an exemplary embodiment of the present inventive concept, a heat engine operating by circulating a working fluid is operated in Brayton cycle mode or Rankine cycle mode; In a Brayton cycle mode of cooling and then compressing the working fluid flowing out of the turbine, storing the heat-exchanging fluid by heat exchange with the working fluid before cooling; And heat exchange with the working fluid compressed in the Rankine cycle mode and the heat storage fluid stored in the Brayton cycle mode in a Rankine cycle mode in which the working fluid discharged from the turbine is condensed and cooled and then compressed. A method of operating a heat engine may be provided.

Heat engines according to one or more embodiments of the present inventive concept have improved exergy efficiency.

1 is a view for explaining a heat engine operating in a conventional Rankine cycle mode,
2 and 5 are views for explaining the heat engine of FIG.
3 is a view for explaining a heat engine operating in a conventional Brayton cycle mode,
4 and 6 are views for explaining the heat engine of FIG.
7 is a view for explaining a heat engine according to an exemplary embodiment of the inventive concept,
8 is a view for explaining the heat engine of FIG.
9 and 10 are views for explaining a heat engine according to another exemplary embodiment of the inventive concept,
11 and 12 are views for explaining the effect according to the inventive concept,
13 is a view showing a modification of the embodiment of FIG. 7, and
14, 15, and 16 exemplarily illustrate steam cycles that can be implemented in a heat engine according to the inventive concept.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features, and advantages of the present invention will become more readily apparent from the following description of preferred embodiments with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. The terms "comprises" and / or "comprising" used in the specification do not exclude the presence or addition of one or more other elements.

Hereinafter, the present invention will be described in detail with reference to the drawings. In describing the specific embodiments below, various specific details have been set forth in order to explain the invention in greater detail and to assist in understanding it. However, it will be appreciated by those skilled in the art that the present invention may be understood by those skilled in the art without departing from such specific details. In some cases, it is mentioned in advance that parts of the invention which are commonly known in the description of the invention and which are not highly related to the invention are not described in order to prevent confusion in explaining the invention without cause.

Definition of Terms

As used herein, the term "vapor cycle" includes the transcritical Rankine cycle and the supercritical Brayton cycle.

7 is a view for explaining a heat engine according to an exemplary embodiment of the present invention concept, Figure 8 is a view for explaining the heat engine of FIG.

Referring to these figures, a heat engine according to an exemplary embodiment of the inventive concept may include a turbine 10, a first recuperator 30, a second recuperator 20, a capacitor 40, and a pump 50. ), The high temperature heater 60 may be included. Meanwhile, for the purpose of illustrating the inventive concept, the LT Heat Source and the conduits are additionally shown.

The heat engine according to the exemplary embodiment of the present inventive concept operates in the Rankine cycle mode, and the exergy efficiency may be improved by appropriately utilizing a lower heat source.

The turbine 10 flows into the second recuperator 20 after working while adiabaticly expanding the working fluid.

The second recuperator 20 exchanges heat between the working fluid flowing out of the first recuperator 30 and the working fluid flowing out of the turbine 10. That is, the working fluid flowing through the fifth conduit 5 and the working fluid flowing through the second conduit 2 are exchanged with each other.

The first recuperator 30 exchanges heat between the working fluid flowing out of the second recuperator 20 and the working fluid compressed and discharged by the pump 50. That is, the working fluid flowing through the sixth conduit 6 and the working fluid flowing through the first conduit 1 are exchanged with each other.

In addition, the first recuperator 30 may exchange heat with the working fluid compressed and discharged by the pump 50 and the low heat source (LT Heat Source). That is, the working fluid flowing through the first pipe line 1 is exchanged with the lower heat source.

In FIG. 7, the first recuperator 30 exchanges the working fluid flowing through the first conduit 1 with the working fluid flowing through the sixth conduit 6 while heat-exchanging the lower heat source. However, the configuration using one recuperator as described above may be configured differently as an exemplary configuration.

For example, it is also possible to comprise a recuperator with one recuperator and a separate low temperature heater. Referring to FIG. 13, the working fluid flowing through the first pipe line 1 includes a low temperature heater 34 for heat-exchanging a lower heat source, and a working fluid flowing through the first pipe line 1, and the sixth pipe line 6. Each of the recuperators 32 for exchanging heat with the working fluid flowing therethrough may be configured separately.

The capacitor 40 receives the working fluid flowing out of the first recuperator 30, condenses and cools it, and then flows out to the pump 50.

The pump 50 compresses the working fluid condensed and cooled by the condenser 40 and flows out toward the first recuperator 30.

As described above, the working fluid compressed and discharged by the pump 50 passes through the first and second recuperators 30 and 20, and then is heated by the high temperature heater 60. Heat exchanged with (HT Heat Source) and then flows back into the turbine (10).

According to an exemplary embodiment of the inventive concept, the working fluid described above may be carbon dioxide, but this is illustrative, and the inventive concept is not limited to carbon dioxide only. Known as "the party".

According to an exemplary embodiment of the inventive concept shown in FIG. 7, the working fluid may go through the same steps as in FIG. 8.

Referring to FIG. 8, the working fluid introduced into the turbine 10 is discharged into the fifth conduit 5 with the heat T ₅ after the work 169.9 kJ / kg. The working fluid leaked into the fifth conduit 5 is discharged into the sixth conduit 6 after passing through the second recuperator 30.

The temperature of the working fluid in the fifth pipe line 5 is T5 (449 ° C), and the temperature after heat exchange by the second recuperator 30 is 112 ° C. Referring to FIG. 8, it can be seen that heat Q _R2 (358.1 kJ / kg) was transferred to the working fluid flowing through the second conduit 2 in this process.

The working fluid discharged into the sixth conduit 6 flows back to the capacitor 40 after heat exchange is performed by the second recuperator 20 again. Referring to FIG. 8, it can be seen that heat Q _R1 (91.0 kJ / kg) is transferred to the working fluid flowing through the first conduit 1 in this process.

The capacitor 40 receives the working fluid flowing out of the second recuperator 20 to perform a condensation and cooling process. Referring to FIG. 8, a section in which the condensation and cooling processes in the capacitor 40 are performed is indicated as reference numeral 8. In this interval, the column Q _L may be discarded.

Pump 50 after the work (W _P) which compresses against the working fluid received through the inlet pipe (0), to emit a first rail Coober concentrator 30. The That is, the working fluid compressed by the pump 50 flows into the first recuperator 30 through the first pipe line 1.

The working fluid introduced into the first recuperator 30 undergoes heat exchange with the working fluid flowing through the lower heat source and the sixth conduit 6. That is, the working fluid introduced into the first recuperator 30 receives heat Q _H1 from the lower grade heat source, and receives heat Q _R1 from the working fluid flowing through the sixth conduit 6.

The working fluid flowing out of the first recuperator 30 flows back into the second recuperator 10 through the second conduit 2 to perform a heat exchange operation. That is, the working fluid introduced into the second recuperator 10 exchanges heat with the working fluid flowing through the fifth conduit 5. Referring to FIG. 8, the working fluid introduced into the second recuperator 10 receives heat Q _R2 .

The working fluid flowing out of the second recuperator 10 is supplied to the turbine 10 again after heat exchange with the high heat source Q _H in the high temperature heater 60. Referring to FIG. 8, the working fluid receives heat Q _H2 from a high heat source.

 As described above, the numerical values described with reference to FIG. 8 are merely exemplary, and those skilled in the art should understand that the inventive concept is not limited to such numerical values.

9 is a view for explaining the operation in the blaton cycle mode of the heat engine according to another exemplary embodiment of the invention concept, Figure 10 is a view for explaining the operation in the Rankine cycle mode.

The heat engine according to the inventive concept illustrated in FIGS. 9 and 10 may operate symmetrically in Brayton cycle mode or Rankine cycle mode.

The heat engine illustrated in FIGS. 9 and 10 includes a turbine 110, a first recuperator 130, a second recuperator 120, a compressor 125, a heat storage unit 135, and a capacitor 140. , The cooler 145, the pump 150, the diverters 155 and 165, and the third recuperator 160.

The heat engine illustrated in FIGS. 9 and 10 operates in the Brayton cycle mode or the Rankine cycle mode, and when operating in the Brayton cycle mode, the working fluid discharged from the turbine 110 before cooling with the cooler and Store by heat exchange. In addition, when the heat engine operates in the Rankine cycle mode, the working fluid flowing out of the turbine 110 is condensed and cooled, and then compressed, and the heat engine is exchanged with the compressed working fluid and the working fluid stored in the Brayton cycle mode.

Hereinafter, the Brayton cycle mode will be described with reference to FIG. 9.

In the Brayton cycle mode, the working fluid moves through the cooler 145 and the compressor 125. That is, the direction change unit 155 performs a switching operation so that the working fluid flowing out of the first recuperator 130 and flowing through the seventh conduit 7 flows toward the cooler 145 instead of the condenser 140. . In addition, the direction switching unit 165 performs a switching operation so that the working fluid flowing out from the compressor 125 flows toward the second recuperator 120.

In the Brayton cycle mode, the first recuperator 130 also flows into the sixth conduit 6 through the heat storage fluid and the second recuperator 120 stored in the heat storage unit 135. Heat exchange with each other.

For example, the heat storage unit 135 includes a cool tank and a hot tank, and may be a heat storage fluid (eg, water) stored in the cool tank, but only But not limited to, is pumped by the pump 175 and passed through the first recuperator 130 and then stored in the hot tank. Here, the pump 175 may be a bidirectional pump, but this is exemplary and a person skilled in the art may configure the pump 175 as a one-way pump.

The controller (not shown) may control the pumping direction of the pump 175, and control the heat storage fluid to move from the cool tank to the hot tank in the Brayton cycle mode and to move in the opposite direction in the Rankine cycle mode. have. In addition, as described above, the controller (not shown) may control the turning unit 155 to move the working fluid through the compressor 125 in the Brayton cycle mode.

The second recuperator 120 heats the working fluid flowing out through the compressor 125 and the working fluid flowing through the fourth conduit 4 flowing out of the turbine. Thereafter, the high temperature heater 160 flows out through the second recuperator 120 and receives the working fluid flowing through the third conduit 3, heat exchanges with the high pressure heat source, and then flows out to the turbine 110.

In the Brayton cycle mode, the heat storage fluid stored in the storage unit 135 may store heat corresponding to Q _L in FIG. 4. The heat stored in the heat storage fluid is used in the Rankine cycle mode described later.

The Rankine cycle mode will now be described with reference to FIG. 10.

In Rankine cycle mode, the working fluid moves through the condenser 140 and the pump 150. That is, the direction switching unit 155 performs a switching operation so that the working fluid flowing out of the first recuperator 130 flows toward the condenser 140 instead of the cooler 145. In addition, the direction change unit 165 performs a switching operation so that the working fluid flowing out of the first recuperator 130 flows to the second recuperator 120.

In the Rankine cycle mode, the first recuperator 130 exchanges heat between the heat storage fluid stored in the hot tank of the heat storage unit 135 and the working fluid pumped through the pump 175.

In the Rankine cycle mode, the pump 175 performs a pumping operation to move the heat storage fluid stored in the hot tank toward the cool tank under the control of a controller (not shown).

In the Rankine cycle mode, the first recuperator 130 also includes a working fluid flowing through the second recuperator 120 in the sixth conduit 6, and a working fluid pumped through the pump 150. Heat exchange with each other. Thereafter, the high temperature heater 160 flows out through the second recuperator 120 and receives the working fluid flowing through the third conduit 3, heat exchanges with the high pressure heat source, and then flows out to the turbine 110.

As such, in the Rankine cycle mode, the heat storage fluid stored in the storage unit 135 may function as a low temperature heat source.

FIG. 11 is for explaining the effect of a heat engine, which is an exemplary embodiment of the inventive concept shown in FIGS. 9 and 10.

Referring to FIG. 11, the horizontal axis represents temperature and the vertical axis represents the specific heat of the working fluid. The curve indicated by (1) shows the specific heat in the low pressure region, and the curve indicated by (2) shows the specific heat in the high pressure region. (3) doubles the curve of (1).

The area indicated by the curve indicated by (1) in FIG. 11 may be heat stored by the heat storage fluid in the Brayton cycle mode described with reference to FIG. 9, and the area indicated by the curve indicated by (2) in FIG. It may represent the heat required to heat the working fluid in the compressed state in the Rankine cycle mode described in FIG.

As a result, when the heat is stored while operating in the Brayton cycle mode as shown in FIG. 9, and the heat stored in the Brayton cycle mode is used while operating in the Rankine cycle mode as shown in FIG. 10, the first recuperator in the Rankine cycle mode ( The heat exchange operation of 130 is such that the fluid having the non-thermal characteristics indicated by (2) in FIG. 11 and the fluid having the non-thermal characteristics indicated by (3) in FIG. 11 exert an effect such that heat exchange occurs with each other. do.

This is because, in the Rankine cycle mode of FIG. 10, the working fluid flowing out through the pump 150 exchanges heat with both the heat storage fluid stored in the hot tank and the working fluid flowing through the sixth conduit 6.

That is, the heat storage fluid (for example, may be 'water') stored in the hot tank of the heat storage unit 135 has characteristics similar to those of the non-heat characteristic indicated by (1) in FIG. The working fluid (for example, 'carbon dioxide') flowing through the second recuperator 120 and passing through the sixth conduit 6 also has a specific heat characteristic as indicated by (1) in FIG. 11, Therefore, the sum thereof has characteristics similar to those of the fluid having the specific heat of FIG.

 Therefore, the heat engine according to the inventive concept of operating alternately in the Brayton cycle mode and the Rankine cycle mode as described with reference to FIGS. 9 and 10 is characterized in that the heat required for heating the working fluid on the high pressure side (see FIG. )) From the low pressure side may be sufficient.

12 is another diagram for explaining an effect according to the inventive concept.

12, the exergy efficiency of the heat engine (R-CO2) operating in the conventional Rankine cycle mode, the exergy efficiency of the heat engine (B-CO2) operating in the conventional Brayton cycle mode, and according to the inventive concept It compares the exergy efficiency of heat engines operating in the Rankine cycle mode (LH T-CO2 LH R-CO2), which uses both low-temperature and high-temperature heat sources.

That is, the exergy efficiency of the heat engine (R-CO2) operating in the conventional Rankine cycle mode is 0.614, the exergy efficiency of the heat engine (B-CO2) operating in the conventional Brayton cycle mode is O.629, Exergy efficiency of the heat engine operating in the Rankine cycle mode (LH R-CO2) using a low temperature heat source and a high temperature heat source according to the invention concept is 0.723, it can be seen that the exergy efficiency is improved.

In the three heat engines, the existing Rankine cycle (R-CO2) and the Rankine cycle (LH R-CO2) according to the inventive concept have the same output (150.4), but it is found that the inventive concept is superior in exergy efficiency. Can be. That is, the conventional heat engines (R-CO2, B-CO2) achieved the output (150.4 and 119.4, respectively) using only 100% of the advanced heat source, the heat engine (LH R-CO2) according to the inventive concept is a low-grade heat source 25 In terms of achieving an output of 150.4 using% and a high-grade heat source 75%, it can be said to have a superior effect compared to conventional heat engines.

This generally indicates that the thermal efficiency of the lower heat source does not exceed a maximum of 10% or more. In the heat engine according to the inventive concept, the thermal efficiency of the lower heat source is improved by about 25%, which means that the lower heat source is not used at any point in time and is suitable. It is assumed that this is possible because it is used in.

FIG. 13 is a diagram illustrating a modification of the embodiment of FIG. 7.

The heat engine illustrated in FIG. 13 exemplarily includes a turbine 10, a first recuperator 32, a low temperature heater 34, a second recuperator 20, a capacitor 40, a pump 50, And a high temperature heater 60.

The other components except for the first recuperator 32 and the low temperature heater 34 perform the same or similar operations as the components of FIG. 8 having the same reference numerals.

The low temperature heater 34 exchanges heat between the working fluid compressed by the pump 50 and the lower heat source, and the first recuperator 32 flows out from the low temperature heater 34 and the high temperature heater 20. The working fluid flowing through the sixth pipe line 60 through the heat exchange.

Meanwhile, in the embodiment of FIG. 13, the working fluid compressed by the pump 50 is first heat-exchanged with the lower heat source, but it may be possible to first heat-exchange the working fluid flowing through the sixth conduit 60.

As described above, the heat engine according to the inventive concept may have a Rankine cycle mode in which exergy efficiency is improved, and as a modification, the heat engine may be used in the Rankine cycle mode by securing a lower heat source in the Brayton cycle mode.

14, 15, and 16 exemplarily illustrate steam cycles implemented in a heat engine according to the above-described embodiments.

14, 15, and 16, when the low pressure side operating conditions are higher than the supercritical pressure of the working fluid is characterized in that the working fluid does not undergo a distinct phase change process during the condensation process. In this case, the cooling fluid may not be clearly distinguished from the liquid and gas, and the distinction between the Rankine cycle (with phase change) and the Brayton cycle (gas cycle) may be blurred. However, even at this time, a completely cooled cycle as shown in FIG. 14 may be regarded as a Rankine cycle (FIG. 5) of the prior art in the present invention, and a partially cooled cycle as shown in FIG. 15 may be regarded as the Brayton cycle (FIG. 6), a cycle using both a low temperature heat source and a high temperature heat source simultaneously in a completely cooled cycle as shown in FIG. 16 to which the concept of the present invention is applied is a Rankine cycle in which a low temperature heat source and a high temperature heat source of the prior art are simultaneously used in the present invention. (Fig. 8). As such, even when the steam cycle is not clearly classified into a Rankine cycle or a Brayton cycle, the configuration according to the inventive concept described above can be applied, and the same effect can be achieved. In other words, the inventive concept can be applied to the operating region in which the low pressure side undergoes a distinct phase change, as well as in a driving region that does not experience a distinct phase change higher than the supercritical pressure of the working fluid.

According to one aspect of the inventive concept, in a Rankine cycle used in a heat engine, condensing and cooling the working fluid flowing out of the turbine, compressing the condensed and cooled working fluid, and compressing the compressed working fluid into a lower heat source. An exergy-efficient Rankine cycle method comprising a first heat exchange step of heat exchange with and a second heat exchange step of heat exchange with a working fluid that has undergone the first heat exchange step before condensing and cooling the working fluid which has flowed out of the turbine. Can be. Here, the working fluid passed through the first heat exchange step and the second heat exchange step is introduced into the turbine and circulated again.

In addition, the Rankine cycle method with improved exergy efficiency further includes a third heat exchange step of exchanging heat with the compressed working fluid by the compressing step before condensing and cooling the working fluid that has undergone the second heat exchange step. The working fluid passed through the heat exchange step, the second heat exchange step, and the third heat exchange step is introduced into the turbine.

According to another aspect of the inventive concept, a method for increasing the exergy efficiency of a heat engine including a turbine, a compressor, and a capacitor can be provided. For example, in the method, the working fluid flowing out of the turbine flows to the compressor in the Brayton cycle mode, and flows to the compressor in the Rankine cycle mode, and flows to the compressor in the Brayton cycle mode. And exchanging heat from the previous working fluid and the heat storage fluid, and may be implemented to include the working fluid flowing out of the condenser or the compressor into the turbine.

According to another aspect of the inventive concept, operating a heat engine working by circulating a working fluid in the Brayton cycle mode or the Rankine cycle mode, a Brayton cycle mode in which the working fluid flowing out of the turbine is cooled and then compressed In the heat storage fluid, the heat storage fluid is exchanged and stored with the working fluid before cooling, and in the Rankine cycle mode in which the working fluid flowing out of the turbine is condensed and cooled, and then compressed, the heat stored in the compressed working fluid and the Brayton cycle mode. Heat exchange with the storage fluid; it may be implemented to include.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Various modifications and variations are possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by equivalents to the scope of the appended claims, as well as the appended claims.

10, 110: turbine 30, 130: first recuperator
20, 120: Second recuperator 40, 140: Condenser
50, 150: pump 60: high temperature heater
125: compressor 135: heat storage unit
145: coolers 155, 165; Redirection
160: high temperature heater

Claims (24)

In the transcritical Rankine cycle used for heat engines,
Condensing and cooling the working fluid flowing out of the turbine;
Compressing the condensed and cooled working fluid;
A first heat exchange step of exchanging the compressed working fluid with a lower heat source;
A second heat exchange step of exchanging heat with the working fluid that has passed through the first heat exchange step before condensing and cooling the working fluid discharged from the turbine; And
And a third heat exchange step of exchanging heat with the working fluid compressed by the compressing step, before condensing and cooling the working fluid passed through the second heat exchange step.
The first heat exchange step and the third heat exchange step are performed at the same time,
A transcritical Rankine cycle with improved exergy efficiency, characterized in that the working fluid flowing through the first heat exchange step, the second heat exchange step, and the third heat exchange step flows into the turbine. The method of claim 1,
The transcritical Rankine cycle with improved exergy efficiency, characterized in that the working fluid is carbon dioxide. delete A heat engine based on a transcritical Rankine cycle,
A turbine outflow of the working fluid;
A condenser for condensing and cooling the working fluid discharged from the turbine;
A pump for compressing the condensed and cooled working fluid;
A first recuperator for exchanging the compressed working fluid with a lower heat source; And
A second recuperator for exchanging the working fluid before it flows out of the turbine and into the condenser, with the working fluid which is heat-exchanged by the first recuperator; Including;
The first accumulator heat-exchanges the working fluid compressed by the pump with a lower heat source, and at the same time, heat-exchanging with the working fluid before being heat-exchanged by the second recuperator and entering the condenser,
A trans-critical Rankine cycle-based heat engine, wherein the working fluid, which has undergone heat exchange by the first and second recuperators, is introduced into the turbine. 5. The method of claim 4,
The critical fluid Rankine cycle based heat engine, characterized in that the working fluid is carbon dioxide. delete delete delete delete A heat engine operating in Brayton cycle mode or Rankine cycle mode,
A turbine working by a working fluid;
A direction changer for flowing the working fluid flowing out of the turbine to either the capacitor or the compressor;
A first recuperator for exchanging heat between the working fluid before flowing to the capacitor or the compressor and the heat storage fluid stored in the heat storage unit; And
And, in the Rankine cycle mode, a pump that receives the working fluid from the condenser and compresses it to flow out.
The working fluid flowing out of the condenser or the pump flows into the turbine,
In the Rankine cycle mode, the first recuperator,
The exergy efficiency heat engine, characterized in that the heat exchange between the working fluid before the flow to the condenser or the compressor, the heat storage fluid stored in the heat storage unit, and the working fluid flowing out of the pump. delete The method of claim 10,
In the Brayton cycle mode, the direction switching unit,
A heat engine with improved exergy efficiency, characterized in that for converting the working fluid flowing out of the turbine to flow to the compressor. The method of claim 12,
It further comprises a cooler disposed between the turning unit and the compressor,
The cooler is a heat engine with improved exergy efficiency, characterized in that the operating fluid flows from the direction change unit to cool the flow out to the compressor. The method of claim 10,
In the Rankine cycle mode, the direction switching unit,
A heat engine with improved exergy efficiency, characterized in that for converting the working fluid flowing out of the turbine to flow to the capacitor. delete delete The method of claim 10,
And a second recuperator for heat-exchanging the working fluid before flowing into the first recuperator and the working fluid flowing out of the condenser or the compressor. In a method for increasing the exergy efficiency of a heat engine including a turbine, a compressor, a capacitor, and a first recuperator,
Redirecting the working fluid flowing out of the turbine to the compressor in Brayton cycle mode and to the condenser in Rankine cycle mode;
In the Brayton cycle mode, the first recuperator heat exchanges the working fluid before flowing to the compressor and the heat storage fluid stored in the heat storage unit;
Introducing a working fluid discharged from the condenser or the compressor into the turbine;
In the Rankine cycle mode, a pump receives and compresses a working fluid from the condenser; And
In the Rankine cycle mode, the first recuperator mutually exchanging a working fluid before flowing to the compressor, a heat storage fluid heat exchanged with the working fluid in the Brayton cycle mode, and a working fluid flowing out of the pump; Method for increasing the exergy efficiency of the heat engine comprising a. delete 19. The method of claim 18,
In the Brayton cycle mode,
Cooling the working fluid before entering the compressor; the method of increasing the exergy efficiency of a heat engine, characterized in that it comprises a. delete delete 19. The method of claim 18,
In the Rankine cycle mode, the second recuperator,
And exchanging heat between the working fluid before flowing to the condenser and the working fluid compressed and discharged by the pump. 2. Operating a heat engine circulating working fluid in Brayton cycle mode or Rankine cycle mode;
Storing the heat storage fluid heat-exchanged with the working fluid in a Brayton cycle mode in which the working fluid flowing out of the turbine is heat-exchanged with the heat storage fluid to be cooled and then compressed; And
In a Rankine cycle mode in which a pump compresses a working fluid flowing out of the turbine after the condenser condenses and cools the heat storage fluid stored in the Brayton cycle mode before the flowing out of the turbine and entering the condenser. Exchanging heat with a working fluid compressed and discharged by a pump.

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