KR20190032841A - Rankine cycle-based heat engine using ejector for waste heat recovery and method for operating the same heat engine - Google Patents

Abstract

According to an embodiment of the present invention, a heat engine based on a steam cycle comprises: a step of circulating a working fluid through a steam cycle comprising an evaporator, a turbine, a condenser, and a pressurizing pump; a step of re-supplying a part of the working fluid discharged from the condenser to the condenser along a feedback route connecting an output end and an input end of the condenser; and a step of allowing exhaust gas discharged from a combustion apparatus and the working fluid on the feedback route to exchange heat. Here, the pressure of the working fluid of the feedback route is set to be lower than the pressure of the working fluid passing through the condenser, thereby maintaining the evaporating temperature of the working fluid of the feedback route lower than the evaporating temperature of the working fluid passing through the condenser.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a waste heat recovery apparatus and a method of operating the same,

The present invention relates to a steam cycle-based cogeneration heat pump, and more particularly, to a steam cycle-based heat pump with a feedback path connecting an output stage and an input stage of a condenser, thereby maximizing the waste heat recovery and water recovery of the exhaust gas, And a method for operating the same.

BACKGROUND ART [0002] Generally, a power generation system using a steam cycle-based heat pipe is used in a power plant or the like. Recently, such a steam cycle-based heat engine is also used as a power generation system using various waste heat (exhaust gas).

Figure 1 shows a conventional conventional steam cycle-based heat engine. A typical steam cycle heat engine converts the thermal energy into mechanical work by means of a working fluid circulating between the evaporator 10, the turbine 20, the condenser 30 and the pump 40 as shown to obtain power. The exhaust gas discharged from the combustion apparatus is supplied to the evaporator 10, for example, to transmit thermal energy to the working fluid, and the working fluid can receive the thermal energy to vaporize and then drive the turbine.

The waste heat of the exhaust gas can not be efficiently recovered in the conventional waste heat steam cycle, and in recent years, water (H2O) in the exhaust gas has been often discharged without being sufficiently recovered. In the case of power plants, especially water consumption is high and the exhaust gas temperature of the power plant is 100 ° C or more, and a large amount of water is discharged in the state of steam, so that the water recovery is required to be maximized. Conventionally, absorbent materials or cooling water are used for water recovery. The dehumidifying devices using the absorbing material have a drawback in that a large amount of cooling water is circulated due to a small temperature difference when the exhaust gas is cooled by using cooling water.

In addition, it is important to increase the waste heat generation efficiency (power generation / waste heat capacity) in the waste heat power generation heat pipe system. However, in the case of a steam cycle-based heat pipe, the efficiency of the waste heat generation varies depending on the temperature of the exhaust gas and the kind of the working fluid. Therefore, it is required to find the optimal waste heat generation efficiency for a given heat pipe system.

Patent Document 1: Korean Patent Publication No. 2010-0044738 (published on Apr. 30, 2010) Patent Document 2: Korean Patent No. 10-1450660 (published on October 15, 2014)

SUMMARY OF THE INVENTION The present invention is conceived to solve the above problems and provides a heat engine system capable of maximizing waste heat recovery and water recovery of exhaust gas.

Also, in one embodiment of the present invention, there is provided a heat engine system having an optimal waste heat generation efficiency while maximizing waste heat recovery and water recovery.

According to an embodiment of the present invention, there is provided a method of operating a steam cycle-based cogeneration heat engine, comprising: circulating a working fluid along a steam cycle including an evaporator, a turbine, a condenser, and a pressure pump; Supplying a part of the working fluid discharged from the condenser to the condenser along a feedback path connecting the output end and the input end of the condenser; And a step of heat-exchanging the exhaust gas discharged from the combustion apparatus with the working fluid of the feedback path, wherein the pressure of the working fluid in the feedback path is set to be smaller than the pressure of the working fluid passing through the condenser, Wherein the evaporation temperature of the working fluid in the path is kept lower than the evaporation temperature of the working fluid passing through the condenser.

In one embodiment, the evaporator includes a heat exchanger for exchanging heat between the working fluid and the exhaust gas, wherein the exhaust gas discharged from the combustion apparatus is heat-exchanged with the working fluid in the evaporator to supply thermal energy to the working fluid, And then exchange heat with the working fluid of the feedback path.

According to another embodiment of the present invention, there is provided a method of operating a steam cycle-based cogeneration heat engine, comprising: circulating a steam cycle including a first heat exchanger, a turbine, a condenser, and a pressurized pump along a working fluid; Supplying a part of the working fluid discharged from the condenser to the condenser along a feedback path connecting the output end and the input end of the condenser and provided with the second heat exchanger; And a step in which exhaust gas discharged from a combustion device exchanges heat with a working fluid in the first heat exchanger and then exchanges heat with a working fluid in the second heat exchanger, Wherein the evaporating temperature of the working fluid in the feedback path is maintained to be lower than the evaporating temperature of the working fluid passing through the condenser, do.

According to another embodiment of the present invention, there is provided a steam cycle-based waste heat generating heat pipe comprising: an evaporator which evaporates heat by applying thermal energy to a working fluid; A turbine that mechanically works by a working fluid supplied from the evaporator; A condenser for condensing the working fluid discharged from the turbine; A pressurizing pump for pressurizing the working fluid discharged from the condenser and supplying the working fluid to the evaporator; A feedback path connecting an output end and an input end of the condenser; And a heat exchanger (50) disposed on the feedback path for exchanging heat between the exhaust gas discharged from the combustion apparatus and the working fluid of the feedback path, the pressure of the working fluid in the feedback path passing through the condenser And the evaporation temperature of the working fluid in the feedback path is kept lower than the evaporation temperature of the working fluid passing through the condenser.

In one embodiment, the evaporator includes a heat exchanger for exchanging heat between the working fluid and the exhaust gas, wherein the exhaust gas discharged from the combustion device sequentially passes through a heat exchanger of the evaporator and a heat exchanger of the feedback path, Heat exchange with the fluid is possible.

In one embodiment, the apparatus further comprises an ejector connecting the feedback path and the input of the condenser, wherein a driving nozzle of the ejector is connected to an output end of the turbine, an injection nozzle of the ejector is connected to an input of the condenser, The inlet of the ejector may be connected to the feedback path.

In one embodiment, the apparatus further comprises an ejector for connecting the feedback path and the input of the condenser, wherein the driving nozzle of the ejector is connected to a conduit for a working fluid connecting the evaporator and the turbine, And a conduit of a working fluid connecting the turbine and the condenser, and an inlet of the ejector may be connected to the feedback path.

According to an embodiment of the present invention, a feedback path is provided for connecting an output end and an input end of a condenser of a steam cycle, and a heat exchanger is provided on the feedback path. Heat exchange between the exhaust gas and the working fluid is performed in the heat exchanger, Thereby achieving the effect of maximizing recovery and water recovery.

In this case, by using the ejector to connect the feedback path and the steam cycle path, it is possible to lower the working fluid pressure on the feedback path, thereby lowering the evaporation temperature of the working fluid in the heat exchanger of the feedback path, Thereby achieving the effect of further increasing the heat exchange between the heat exchanger and the heat exchanger.

Also, according to an embodiment of the present invention, the exhaust gas temperature can be lowered simultaneously with the production of power through the exhaust gas cogeneration system and the water in the exhaust gas can be condensed to recover the water and utilize it as the water. If the exhaust gas temperature is cooled to room temperature, the condensable fine dust which occupies 80% or more of the exhaust gas can be simultaneously recovered and removed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a conventional steam cycle-based heat engine,
2 is a view for explaining a steam cycle-based heat engine according to the first embodiment of the present invention,
3 is a view for explaining a steam cycle-based heat engine according to the second embodiment,
4 is a view for explaining a TS diagram of a steam cycle-based heat engine according to an embodiment,
5 is a view for explaining the TS diagram when the evaporation temperature of the working fluid is lowered,
6 is a view for explaining the efficiency of the heat engine according to the evaporation temperature of the working fluid,
7 is a view for explaining a steam cycle-based heat engine according to the third embodiment.

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.

In the present specification, the singular form includes plural forms unless otherwise specified in the specification. The terms "comprise" 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 contents have been set forth in order to explain the invention in more detail and to aid understanding. 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 should be mentioned in advance that it is common knowledge in describing an invention, and that parts not significantly related to the invention are not described in order to avoid confusion in describing the invention.

2 shows a steam cycle-based heat engine according to a first embodiment of the present invention. In the present specification, the term "heat pipe" is a system for converting thermal energy into mechanical energy through circulation between a high-temperature and low-temperature heat source. The heat engine can be used as a power source of a vehicle such as an automobile or a ship, a steam turbine of a power plant, etc. However, the use of the heat engine is not particularly limited in the present invention.

Referring to FIG. 2, a steam cycle-based heat engine according to an embodiment may include an evaporator 10, a turbine 20, a condenser 30, and a pressurization pump 40. The evaporator 10, the turbine 20, the condenser 30, and the pressurizing pump 40 constitute a steam cycle and are connected by the first to fourth pipes L1 to L4. The first to fourth conduits L1 to L4 constitute a closed loop, and the working fluid flows in the conduit. In one embodiment the working fluid may be a water (H ₂ O), it may be other working fluid known to be used in alternative embodiments.

The evaporator 10 applies heat energy to the working fluid to evaporate (vaporize) the working fluid. In one embodiment, a boiler or a combustion device may be used as the evaporator 10, and the working fluid may be directly or indirectly heated and evaporated in such a boiler or combustion device. The working fluid supplied to the evaporator 10 through the fourth conduit L4 is discharged from the evaporator 10 through the first conduit L1. The discharged high temperature working fluid is supplied to the turbine 20, and the turbine 20 mechanically works by the working fluid and discharges the working fluid through the second conduit L2.

The condenser 30 receives the working fluid discharged from the turbine 20 to condense and cool it. That is, in one embodiment, the condenser 30 may be implemented with any heat exchanger. At this time, a refrigerant (water-cooled or air-cooled) flows into the condenser 30 from the seventh conduit L7, receives heat energy from the working fluid, and is heated and discharged to the eighth conduit L8. The pressurizing pump 40 compresses the condensed and cooled working fluid in the condenser 30 and discharges it to the evaporator 10 through the fourth conduit L4.

In one embodiment, the heat engine further comprises a feedback path L10, L11, L12 connecting the output and input of the condenser 30. The feedback path L10 is branched from the third conduit L3 connected to the output end of the condenser 30 and the feedback path L12 is joined to the second conduit L2 connected to the input end of the condenser 30 . Accordingly, a part of the working fluid discharged from the condenser 30 is circulated along the feedback path of the tenth to twelfth pipelines L10 to L12 and supplied to the condenser 30 again.

In one embodiment, the heat engine can include a heat exchanger 50 and a circulation pump 60 installed on the feedback path. The heat exchanger 50 exchanges heat between the exhaust gas discharged from the combustion apparatus and the working fluid on the feedback path. In one embodiment, the combustion device may be one of any combustion device, such as, for example, a gas turbine, a gas engine, a diesel engine, a combustor, an incinerator, and the exhaust gas may be a hot waste gas exhausted from any such combustion device .

The steam in the exhaust gas is condensed by the heat exchange between the exhaust gas and the working fluid in the heat exchanger 50. The working fluid is vaporized by receiving the heat energy and then discharged through the twelfth pipe line L12, L2) and is re-supplied to the condenser (30). The water vapor condensed in the heat exchanger 50 is discharged as water and the remaining components of the exhaust gas can be discharged in a separate path.

The circulation pump 60 operates so that the working fluid circulates along the feedback path. Unlike the pressurizing pump 40, the circulating pump 60 does not apply any additional pressure to the working fluid and serves to pump the working fluid to circulate.

How much of the working fluid discharged from the condenser 30 is circulated through the feedback path may vary depending on the specific embodiment. In one embodiment, for example, 1:10 may be cycled to the feedback path, but this ratio may vary depending on the embodiment.

The number of revolutions of the circulation pump 60 may be adjusted to control the flow rate of the working fluid to be circulated to the feedback path, or a flow control valve (not shown) may be provided on the feedback path, for example. In one embodiment, the flow control valve may increase or decrease the flow rate of the working fluid to be circulated to the feedback path depending on the temperature of the exhaust gas supplied to the heat exchanger 50. For example, a higher temperature of the exhaust gas may require more working fluid to condense steam, thereby increasing the flow rate of the circulating working fluid to the feedback path and vice versa. Although not shown in the drawing, the flow rate control includes, for example, a temperature sensor for measuring the temperature of the exhaust gas supplied to the heat exchanger 50 and a flow rate control signal based on the sensed value of the temperature sensor, And a control unit for delivering it to the valve.

Meanwhile, in a preferred embodiment, the heat engine may further include an ejector 70 that connects the feedback path and the input of the condenser 30. In one embodiment, the ejector 70 connects the feedback path L12 with the second conduit L2 connecting the turbine 20 and the condenser 30. [ The ejector 70 is a device for mixing a fluid using a venturi effect. The ejector 70 gradually reduces the diameter of the pipe and injects the fluid to be mixed into the enlarged venturi pipe. Hereinafter, an input end of the ejector 70 will be referred to as a motive nozzle, an output end will be referred to as a diffuser nozzle, and an injection port for inputting a fluid to be mixed will be referred to as a suction port. In the illustrated embodiment, the driving nozzle of the ejector 70 is connected to the output end of the turbine 20, the injection nozzle of the ejector 70 is connected to the input of the condenser 30, And is connected to the path L12.

In this configuration, when the pressure Pout of the working fluid output from the turbine 20 is set to be larger than the pressure Pc of the working fluid flowing into the condenser 30, the working fluid flows toward the driving nozzle of the ejector 70 Pressurized and supplied. The working fluid in the feedback path can be injected into the ejector 70 through the intake port of the ejector 70 when the working fluid passes through the venturi pipe in the ejector 70. [ When the pressure of the working fluid flowing through the feedback paths L10 to L12 at this time is represented as "Pe ", the relationship of [Pout> Pc> Pe] is established. Therefore, since the pressure Pe of the working fluid in the feedback path is lower than the pressure Pc of the working fluid passing through the condenser 30, the evaporation temperature of the working fluid passing through the heat exchanger 50 in the feedback path is set to the condenser 30 ) And may cause more heat exchange between the exhaust gas and the working fluid in the heat exchanger 50. The heat exchanger 50 may also be operated at a higher temperature than the working fluid.

According to the first embodiment of the present invention as described above, the feedback paths L10 to L12 are formed, and heat exchange between the exhaust gas and the working fluid is performed in the heat exchanger 50 of the feedback path. Water can be maximized. In general, the exhaust gas discharged from the combustion apparatus may have a temperature of about 100 to 200 degrees centigrade, and even when waste heat of the exhaust gas is recovered through any conventional heat exchanging means or the like, (Chimney) at the temperature of the road. However, the discharged exhaust gas still contains a large amount of water, and in order to maximize the water recovery, it may be desirable to lower the outlet temperature of the exhaust gas to 50 ° C or less.

According to the first embodiment, the feedback paths L10 to L12 circulating through the condenser 30 are formed, and the heat exchanger 50 is installed in the feedback path to heat exchange the exhaust gas and the working fluid. At this time, the exhaust gas to be inputted into the heat exchanger 50 may be, for example, exhaust gas having primarily a waste heat recovered and having a temperature of 70 to 80 degrees Celsius, and heat exchange with the working fluid in the heat exchanger 50, The water temperature can be lowered to 50 degrees or less and the water content in the exhaust gas can be condensed to achieve water recovery. Also, in this process, only the working fluid of the original steam cycle is used and no additional refrigerant or working fluid is used, and a part of the working fluid circulating the existing steam cycle is branched and recirculated, and through the phase change of the recirculated working fluid Since the exhaust gas can be cooled, the recovery of waste heat and the recovery of water can be enhanced with a relatively simple system configuration.

In this case, the feedback path and the conduit L2 flowing into the condenser 30 may be connected by the ejector 70, so that the heat exchange energy in the heat exchanger 50 can be further increased. Since the pressure Pe of the working fluid in the feedback path is lower than the pressure Pc of the working fluid passing through the condenser 30 as described above, the evaporation temperature of the working fluid passing through the heat exchanger 50 in the feedback path is set to the condenser (Condensation) temperature of the working fluid passing through the first and second heat exchangers 30 and 30. Therefore, more heat exchange can be achieved between the exhaust gas and the working fluid in the heat exchanger 50, so that the waste heat of the exhaust gas and the water recovery from the exhaust gas can be maximized.

Fig. 3 shows a steam cycle-based heat engine according to the second embodiment.

Referring to the drawings, the steam cycle-based heat engine according to the second embodiment includes a first heat exchanger 80, a turbine 20, a condenser 30, a pressurizing pump 40, a second heat exchanger 50, A pump 60, and an ejector 70. The steam cycle configuration and the pipelines constituted by the first heat exchanger 80, the turbine 20, the condenser 30 and the pressurizing pump 40 and the ducts L10 to L12, the second heat exchanger 50, and the ejector 70, Is the same as or similar to that of the first embodiment shown in Fig. 2, and thus the description thereof will be omitted.

Compared with the first embodiment of FIG. 2, the second embodiment of FIG. 3 differs from the first embodiment of FIG. 3 in that the exhaust gas discharged from the combustion apparatus is heat-exchanged in the first heat exchanger 80 and then supplied to the second heat exchanger 50 There is a difference. That is, the exhaust gas discharged from the combustion apparatus sequentially passes through the first heat exchanger 80 and the second heat exchanger 50, and is configured to exchange heat with the working fluid.

According to the configuration of the second embodiment, the waste heat utilization and the water recovery of the exhaust gas discharged from the combustion apparatus are achieved in the steam cycle engine of the present invention. For example, when the exhaust gas at a high temperature (for example, between 100 and 200 degrees centigrade) is heat-exchanged with the working fluid in the first heat exchanger 80 and then becomes a low temperature of 70 to 80 degrees Celsius, Is supplied to the second heat exchanger (50) without being discharged, and can be exchanged again with the working fluid of the feedback path in the second heat exchanger (50) to be reduced to 50 degrees or less (for example, 30 to 40 degrees). Therefore, it is possible to maximize the utilization of the waste heat of the exhaust gas in the steam cycle engine of the present invention and also to increase the recovery rate of water in the exhaust gas.

On the other hand, in the steam cycle-based heat engine according to this embodiment, the working fluid circulates through the first heat exchanger 80, the turbine 20, the condenser 30, and the pressurizing pump 40, In the example, the working fluid is set to have an evaporation temperature within a predetermined temperature range. In one preferred embodiment, the evaporation temperature of the working fluid can be set such that the waste heat generation efficiency of the heat engine shown has a maximum value. In another preferred embodiment, the evaporation temperature of the working fluid can be set so that the waste heat generation efficiency of the heat engine shown has a certain range of system efficiency values including the maximum value. The evaporation temperature range of the working fluid is described below with reference to FIGS. 4 to 6. FIG.

Figure 4 shows a T-S (temperature-entropy) diagram of the steam cycle-based heat engine of Figure 3; In the figure, the X-axis is the entropy and the Y-axis is the temperature, and the graph shows the temperature-entropy change of the working fluid with the steam cycle.

4 are the same as the numbers of the first to eighth ducts L1 to L8 in Fig. 3, respectively. 3, when the working fluid supplied to the first heat exchanger 80 through the fourth conduit L4 is heated and vaporized and then discharged to the first conduit L1, Move along the line from point to point 1. That is, the temperature and entropy increase at point 4, and the evaporation starts at point 9, the temperature is kept constant and the entropy continues to increase.

Then, while the working fluid passes through the turbine 20, the working fluid moves from point 1 to point 2 in FIG. Moving from point 2 to point 3 in FIG. 4 corresponds to cooling and condensation of the working fluid through the condenser 30 and moving from point 3 to point 4 in FIG. 40, respectively.

The exhaust gas passing through the first heat exchanger 80 of FIG. 3 moves along the line from point 5 to point 6 in FIG. That is, when the exhaust gas passes through the first heat exchanger 80, it is cooled while transferring the heat energy to the working fluid, and the entropy also becomes small. The refrigerant (water-cooled or air-cooled) passing through the condenser 30 of FIG. 3 moves along the line from point 7 to point 8 in FIG.

The heat energy transferred from the exhaust gas to the working fluid in the first heat exchanger 80 is the heat amount Q _EG corresponding to the temperature difference in the temperature-entropy graph of the exhaust gas of FIG. 4 (that is, the graph from points 5 to 6) _in an exhaust gas in order to transfer thermal energy to the working fluid temperature of the exhaust gas in the first heat exchanger 80 is passed by the 4-entropy graph, the temperature of the operating fluid, and more entropy graph always be above, at this time, The minimum temperature difference for heat transfer is called the pinch temperature (ΔT1).

On the other hand, the efficiency of a steam cycle-based cogeneration system can be explained by waste heat recovery efficiency, cycle efficiency, and waste heat efficiency. The waste heat recovery efficiency (η _HR ) can be defined as the heat quantity (Q _{EG, in} ) utilized in the steam cycle for the maximum heat quantity (Q _{EG, max} ) available when cooling the exhaust gas to room temperature have.

η _HR = Q _{EG, in} / Q _{EG, max} --- Equation 1

The cycle efficiency (eta _cyc ) can be defined as the net output date (W _net ) of the steam cycle with respect to the heat quantity (Q _{EG, in} ) utilized in the steam cycle and expressed as Equation 2 below.

侶_cyc = W _net / Q _{EG, in} --- Equation 2

The system efficiency (η _sys ) of the waste heat generation system (η _sys ) can be defined as the _net output day (W _net ) of the steam cycle with respect to the maximum amount of heat that can be utilized when the waste heat is cooled down to room temperature, and is proportional to the product of the waste heat recovery efficiency and the cycle efficiency As shown in FIG. For example, the waste heat (system) efficiency can be expressed by Equation 3 below.

侶_sys = W _net / Q _{EG, max} --- Equation 3

Since it is important to maximize the output of the waste heat steam cycle from a given waste heat source in a steam cycle-based heat pump, it is important to improve the efficiency of the waste heat generation among the above three efficiencies. According to an embodiment of the present invention, the evaporation temperature of the working fluid can be adjusted in order to increase the efficiency of waste heat generation of the heat engine. For example, by optimizing the waste heat recovery efficiency and cycle efficiency by raising or lowering the evaporation temperature of the working fluid, optimum waste heat generation efficiency can be achieved.

5 shows a T-S diagram when the evaporating temperature of the working fluid is lowered. Compared with FIG. 4, it can be seen that the temperature at point 9 and point 1 in FIG. 5 is lowered. Therefore, in this case, the working fluid in the first heat exchanger 80 receives heat energy from the exhaust gas, and the temperature and entropy increase at the fourth point. Then, the evaporation starts at the point 9, and while the working fluid evaporates, And the entropy increases.

At this time, the temperature-entropy graph of the exhaust gas (i.e., the graph from points 5 to 6) and the temperature-entropy graph of the working fluid passing through the first heat exchanger 80 (i.e., 1), the temperature difference between the exhaust gas and the exhaust gas may be larger than that shown in FIG. That is, the slope of the temperature-entropy graph of the exhaust gas of FIG. 5 is more inclined than in FIG. Therefore, in this case, the waste heat recovery efficiency? _HR is increased as compared with FIG.

However, when the temperature of the exhaust gas (exhaust outlet temperature) at the time of passing through the first heat exchanger 80 is lowered, the cycle efficiency? _Cyc is reduced. Therefore, the waste heat that is proportional to the product of the waste heat recovery efficiency and the cycle efficiency The power generation efficiency may be rather reduced. On the contrary, when the evaporation temperature is increased, the cycle efficiency is increased, but the waste heat recovery efficiency is lowered because the exhaust outlet temperature is increased.

In other words, there is a trade-off relationship between waste heat recovery efficiency and cycle efficiency, and FIG. 6 schematically shows a trade-off between these two efficiencies. Referring to FIG. 6, as described above, as the evaporation temperature of the working fluid is lowered, the waste heat recovery efficiency is increased but the cycle efficiency is lowered. As the evaporation temperature of the working fluid is increased, the waste heat recovery efficiency is lowered and the cycle efficiency is increased. Thus, the efficiency of the waste heat system (proportional to the product of the two efficiencies) has a maximum value (η _MAX ) at any given evaporation temperature, as shown, but at a lower or higher evaporation temperature, the system efficiency drops. Therefore, it is desirable to maintain the evaporation temperature of the working fluid within a certain range so that the system efficiency is a maximum value (? _MAX ) or a system efficiency value within a predetermined range including this maximum value (? _MAX ).

For example, when the system efficiency is a maximum value (? _MAX ) or at least 90% of the maximum value, the evaporating temperature of the working fluid is set within a temperature range between T1 and T2 . In the illustrated embodiment, it is assumed that the optimum system efficiency is equal to or greater than 90% of the maximum value eta _MAX , and thus the evaporation temperature of the working fluid is set to T1 to T2. However, according to the specific embodiment, The evaporation temperature range of the working fluid can be varied.

In one embodiment, as a method of adjusting the evaporation temperature of the working fluid, a method of controlling the pressure applied to the working fluid (determined by the flow rate of the refrigerant and the number of revolutions of the turbine) can be used. For example, the pressure of the working fluid flowing into the first heat exchanger (80) can be adjusted by controlling the pressure applied to the working fluid by the pressurizing pump (40). For example, when the pressure of the working fluid flowing into the first heat exchanger 80 is lowered, the evaporating temperature of the working fluid is lowered and the evaporating temperature is increased by increasing the pressure of the working fluid flowing into the first heat exchanger 80.

3, the exhaust gas discharged from the combustion apparatus sequentially passes through the first heat exchanger 80 in the steam cycle and the second heat exchanger 50 in the feedback path, Heat energy recovery and water recovery can be maximized. In addition, for example, by controlling the pressure of the working fluid in the steam cycle by controlling the pressurizing pump 40, the evaporating temperature of the working fluid can be raised or lowered, thereby realizing a heat engine having optimal cogeneration efficiency.

7 shows a steam cycle-based heat engine according to the third embodiment.

The steam cycle-based heat engine according to the third embodiment includes a first heat exchanger 80, a turbine 20, a condenser 30, a pressurizing pump 40, a second heat exchanger 50, a circulation pump 60, And an ejector 70. The steam cycle configuration and the pipelines constituted by the first heat exchanger 80, the turbine 20, the condenser 30 and the pressurizing pump 40 and the ducts L10 to L12, the second heat exchanger 50, and the ejector 70, Is the same as or similar to that of the second embodiment shown in Fig. 3, and thus the description thereof will be omitted.

Compared with the second embodiment of Fig. 3, the third embodiment of Fig. 7 differs from the second embodiment in the mounting position of the ejector 70. Fig. 7, a branch pipeline L14 branching from the first pipeline L1 connecting the first heat exchanger 80 and the turbine 20 is added, and the ejector 70 is connected to the branch pipeline L14 and feedback And is connected to the path L12. Specifically, the driving nozzle of the ejector 70 is connected to the branch conduit L14, and the inlet of the ejector 70 is connected to the upstream conduit (not shown) of the feedback path L12 of the working fluid discharged from the second heat exchanger 50 L121, and the injection nozzle of the ejector 70 is connected to the downstream side pipeline L122 of the feedback path among the feedback paths L12. At this time, the downstream side pipeline L122 of the feedback path is configured to join the second pipeline L2 connecting the turbine 20 and the condenser 30. [

In this configuration, when a part of the high-pressure working fluid discharged from the first heat exchanger 80 is inputted to the drive nozzle of the ejector 70 through the branch pipe L14 and passes through the venturi pipe in the ejector 70 The pressure can be lowered and the working fluid in the feedback path L121 can be injected into the ejector 70 through the inlet of the ejector 70. [ That is, let Pin be the pressure of the working fluid of the branch conduit L14, Pc be the pressure of the working fluid passing through the condenser 30, and Pe be the pressure of the working fluid flowing through the feedback paths L10 through L12, ≫ Pc > Pe]. Therefore, as described with reference to FIG. 2, since the pressure Pe of the working fluid in the feedback path is lower than the pressure Pc of the working fluid passing through the condenser 30, the second heat exchanger 50 of the feedback path The evaporation temperature of the passing working fluid can be kept lower than the evaporation temperature of the working fluid passing through the condenser 30 and the second heat exchanger 50 can generate more heat exchange between the exhaust gas and the working fluid .

It will be apparent to those skilled in the art that various modifications and variations may be made to the present invention without departing from the spirit or scope of the invention. Therefore, the scope of the present invention should not be limited by the described embodiments, but should be determined by the scope of the appended claims, as well as the appended claims.

10: Evaporator 20: Turbine
30: condenser 40: pressure pump
50: heat exchanger 60: circulation pump
70: Ejector 80: Heat exchanger

Claims (20)

CLAIMS 1. A method of operating a steam cycle-
Circulating a working fluid along a vapor cycle including an evaporator, a turbine, a condenser, and a pressurizing pump;
Supplying a part of the working fluid discharged from the condenser to the condenser along a feedback path connecting the output end and the input end of the condenser; And
Exchanging the exhaust gas discharged from the combustion apparatus with the working fluid of the feedback path,
The pressure of the working fluid in the feedback path is set to be smaller than the pressure of the working fluid passing through the condenser so that the evaporation temperature of the working fluid in the feedback path is kept lower than the evaporation temperature of the working fluid passing through the condenser Wherein said steam cycle-based heat engine operating method comprises: The method according to claim 1,
Wherein the heat engine includes an ejector for connecting the feedback path and an input end of the condenser,
Wherein the drive nozzle of the ejector is connected to the output end of the turbine, the injection nozzle of the ejector is connected to the input of the condenser, and the inlet of the ejector is connected to the feedback path. The method according to claim 1,
Wherein the heat exchange step in the feedback path includes the step of the working fluid being evaporated by receiving thermal energy from the exhaust gas and the steam in the exhaust gas being condensed to produce water. The method according to claim 1,
And a heat exchanger in which the evaporator exchanges heat between the working fluid and the exhaust gas,
Wherein the exhaust gas discharged from the combustion apparatus is heat-exchanged with the working fluid in the evaporator to supply heat energy to the working fluid, and then heat-exchanges the working fluid with the working fluid in the feedback path. 5. The method of claim 4,
Setting the evaporation temperature of the working fluid so that the waste heat generation efficiency of the heat engine has a maximum value and a waste heat generation efficiency value of a predetermined range including the maximum value, wherein the waste heat generation efficiency is a product of a waste heat recovery efficiency of the heat engine and a cycle efficiency Wherein the steam cycle is defined as a proportional value. 6. The method of claim 5,
The waste heat recovery efficiency is the amount of heat utilized in the steam cycle for the maximum amount of heat available when the exhaust gas is cooled to room temperature,
Wherein the cycle efficiency is a net work of steam cycles for the heat utilized in the steam cycle. 6. The method of claim 5,
Wherein the steam pump is configured to increase or decrease the evaporation temperature of the working fluid by adjusting a pressure applied to the working fluid by the pressure pump. CLAIMS 1. A method of operating a steam cycle-
Circulating a vapor cycle comprising a first heat exchanger, a turbine, a condenser, and a pressurized pump along a working fluid;
Supplying a part of the working fluid discharged from the condenser to the condenser along a feedback path connecting the output end and the input end of the condenser and provided with the second heat exchanger; And
Exchanging the exhaust gas discharged from the combustion apparatus with the working fluid in the first heat exchanger and thereafter exchanging heat with the working fluid in the second heat exchanger,
The pressure of the working fluid in the feedback path is set to be smaller than the pressure of the working fluid passing through the condenser so that the evaporation temperature of the working fluid in the feedback path is kept lower than the evaporation temperature of the working fluid passing through the condenser Wherein said steam-cycle-based heat-pipe operation method comprises the steps of: 9. The method of claim 8,
Wherein the heat engine includes an ejector for connecting the feedback path and an input end of the condenser,
Wherein a driving nozzle of the ejector is connected to a conduit of a working fluid connecting the first heat exchanger and the turbine and the injection nozzle of the ejector is connected to a conduit of a working fluid connecting the turbine and the condenser, Is connected to the feedback path. 9. The method of claim 8,
Setting the evaporation temperature of the working fluid so that the waste heat generation efficiency of the heat engine has a maximum value and a waste heat generation efficiency value of a predetermined range including the maximum value, wherein the waste heat generation efficiency is a product of a waste heat recovery efficiency of the heat engine and a cycle efficiency Wherein the steam cycle is defined as a proportional value. 11. The method of claim 10,
The waste heat recovery efficiency is the amount of heat utilized in the steam cycle for the maximum amount of heat available when the exhaust gas is cooled to room temperature,
Wherein the cycle efficiency is a net work of steam cycles for the heat utilized in the steam cycle. 11. The method of claim 10,
Wherein the steam pump is configured to increase or decrease the evaporation temperature of the working fluid by adjusting a pressure applied to the working fluid by the pressure pump. As a steam cycle-based cogeneration heat engine,
An evaporator (10) for evaporating the working fluid by applying thermal energy thereto;
A turbine (20) mechanically operated by a working fluid supplied from the evaporator;
A condenser (30) for condensing the working fluid discharged from the turbine;
A pressure pump (40) for pressurizing the working fluid discharged from the condenser and supplying the working fluid to the evaporator;
A feedback path connecting an output end and an input end of the condenser; And
And a heat exchanger (50) disposed on the feedback path for exchanging heat between the exhaust gas discharged from the combustion apparatus and the working fluid of the feedback path,
The pressure of the working fluid in the feedback path is set to be smaller than the pressure of the working fluid passing through the condenser so that the evaporation temperature of the working fluid in the feedback path is kept lower than the evaporation temperature of the working fluid passing through the condenser A steam cycle-based heat engine. 14. The method of claim 13,
And a heat exchanger in which the evaporator exchanges heat between the working fluid and the exhaust gas,
Wherein the exhaust gas discharged from the combustion apparatus sequentially passes through a heat exchanger of the evaporator and a heat exchanger of the feedback path and performs heat exchange with the working fluid. 15. The method of claim 14,
Further comprising an ejector (70) connecting the feedback path and an input of the condenser,
Wherein a drive nozzle of the ejector is connected to an output end of the turbine, an injection nozzle of the ejector is connected to an input end of the condenser, and a suction port of the ejector is connected to the feedback path. 15. The method of claim 14,
Further comprising an ejector (70) connecting the feedback path and an input of the condenser,
Wherein the driving nozzle of the ejector is connected to a conduit of a working fluid connecting the evaporator and the turbine and the injection nozzle of the ejector is connected to a conduit of a working fluid connecting the turbine and the condenser, Wherein the steam path is connected to a feedback path. The method according to claim 15 or 16,
Setting the evaporation temperature of the working fluid so that the waste heat generation efficiency of the heat engine has a maximum value and a waste heat generation efficiency value of a predetermined range including the maximum value, wherein the waste heat generation efficiency is a product of a waste heat recovery efficiency of the heat engine and a cycle efficiency Wherein the steam-cycle-based heat exchanger is defined as a proportional value. 18. The method of claim 17,
The waste heat recovery efficiency is the amount of heat utilized in the steam cycle for the maximum amount of heat available when the exhaust gas is cooled to room temperature,
Wherein the cycle efficiency is a net work of steam cycles for the heat utilized in the steam cycle. 18. The method of claim 17,
Wherein the predetermined range of the waste heat generation efficiency is a range having a value of 90% or more of a maximum system efficiency value. 18. The method of claim 17,
Wherein the steam pump is configured to increase or decrease the evaporation temperature of the working fluid by regulating a pressure applied to the working fluid by the pressure pump.

Images