A heat driven rankine cycle system

Abstract

The application discloses a heat-driven Rankine cycle system, which comprises a booster assembly and a vortex tube, and can realize the increase of fluid pressure and temperature by using low-grade heat energy without inputting external energy, so as to obtain high-temperature and high-pressure fluid, drive the expander to do work, realize the effective utilization of low-grade heat energy below 100 DEG C, and control the flow between the generator and the high-pressure gas source inlet by a valve, so as to match the heat required by the heat exchanger.

Description

Technical Field

[0001] The present invention relates to the technical field of low-grade energy utilization, and in particular to a heat-driven Rankine cycle system. Background Art

[0002] According to the basic principles of waste heat classification and its cascade comprehensive utilization, the recycling and utilization technology of high-temperature waste heat (above 500℃) and medium-temperature waste heat (200℃~500℃) has become relatively mature, while the recycling and utilization technology of low-temperature thermal energy, that is, relatively low-grade thermal energy (generally below 200℃) is more difficult, and there are still some problems in terms of stability, economy and recovery efficiency.

[0003] Organic Rankine cycle (ORC) power generation can realize the conversion of thermal energy into kinetic energy and then to electrical energy. This system is suitable for power generation from heat sources below 350°C and is one of the important technical approaches to convert low-temperature heat sources into high-quality electricity. Figure 1 This is a schematic diagram of a common organic Rankine cycle. A general organic Rankine cycle includes a heat source 1, a steam turbine 2, a condenser 3, a pump 4, etc.

[0004] The organic Rankine cycle (ORC) uses organic matter with a relatively low boiling point as the medium, producing high-pressure steam at relatively low temperatures. In existing industrial applications, MTI in the United States has developed an ORC waste heat power generation system, which is used to recycle 115°C waste heat from factories. ORMAT has also applied low-temperature ORC power generation technology to recycle low-grade heat sources between 100°C and 250°C.

[0005] However, the efficiency of existing organic Rankine cycles is significantly limited by the heat source temperature. When the heat source temperature is below 100°C, the organic working fluid vapor pressure is low, the system's operating efficiency is poor, and the goal of converting low-grade thermal energy into high-grade electricity is almost impossible. Low-grade thermal energy with a heat source temperature below 100°C is very common. In addition to industrial waste heat, low-grade thermal energy also includes renewable energy sources such as biomass, solar energy, geothermal energy, and even lower-temperature ocean thermal energy. These sources all have relatively low heat source temperatures and relatively low energy density. To effectively utilize this low-temperature, low-grade thermal energy and drive the organic Rankine cycle expander to generate electricity, further system design and optimization are required. Summary of the Invention

[0006] The object of the present invention is to provide a heat-driven Rankine cycle system that can effectively utilize low-grade thermal energy below 100°C.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions.

[0008] A heat-driven Rankine cycle system includes a generator, a booster assembly, a vortex tube, a heat exchanger, an expander, and a valve. The generator has a two-phase saturated working medium. The generator uses low-grade energy to heat the liquid working medium to generate saturated steam. The booster assembly includes a booster and a valve control system. The booster includes a body, a piston, and a spring. The body is provided with a low-pressure chamber and a high-pressure chamber. The piston isolates the low-pressure chamber and the high-pressure chamber. The piston includes a low-pressure end and a high-pressure end. The cross-sectional area of ​​the low-pressure end is adapted to the cross-sectional area of ​​the low-pressure chamber, and the cross-sectional area of ​​the high-pressure end is adapted to the cross-sectional area of ​​the high-pressure chamber. The cross-sectional area of ​​the low-pressure end is larger than the cross-sectional area of ​​the high-pressure end. Therefore, when the pressures of the low-pressure chamber and the high-pressure chamber are equal, the piston compresses the fluid in the high-pressure chamber. One end of the spring abuts against the piston, and the other end abuts against the body. Abutment, the spring can drive the piston movement under certain conditions to increase the volume of the high-pressure chamber, the valve control system can control the saturated steam generated by the generator to enter the low-pressure chamber or the high-pressure chamber, and can also control the outflow of fluid in the low-pressure chamber or the high-pressure chamber. The vortex tube includes a high-pressure gas source inlet, a cold end outlet, and a hot end outlet. The fluid flowing out of the low-pressure chamber enters the high-pressure gas source inlet. The fluid flowing out of the high-pressure chamber is defined as the working fluid. The fluid flowing out of the hot end outlet enters the heat exchanger to heat the working fluid, so that the working fluid is in a high-temperature and high-pressure state. The working fluid flowing out of the heat exchanger then enters the expander to perform external work. The fluid flowing out of the cold end outlet and the fluid flowing out of the expander flow back to the generator after treatment. The valve component controls the flow of high-temperature, high-pressure steam generated by the generator into the high-pressure gas source inlet. In this way, by setting up a booster component, the fluid pressure can be increased without inputting external energy. At the same time, by setting up a vortex tube, the fluid can be heated without inputting external energy, thereby obtaining a high-temperature and high-pressure fluid, which can drive the expander to perform external work and realize the effective utilization of low-grade thermal energy below 100°C. At the same time, the valve controls the flow between the generator and the high-pressure gas source inlet, which can match the heat required by the heat exchanger.

[0009] Furthermore, the valve control system includes a first control valve, a second control valve, a third control valve, and a fourth control valve. The first control valve is arranged on the pipeline between the generator and the low-pressure chamber to control the flow of fluid from the generator into the low-pressure chamber. The second control valve is arranged on the pipeline between the generator and the high-pressure chamber to control the flow of fluid from the generator into the high-pressure chamber. The third control valve is arranged on the pipeline between the vortex tube and the low-pressure chamber to control the flow of fluid from the low-pressure chamber into the vortex tube. The fourth control valve is arranged on the pipeline between the heat exchanger and the high-pressure chamber to control the flow from the high-pressure chamber into the heat exchanger. The valve member is arranged on the pipeline between the generator and the high-pressure gas source inlet. Through the arrangement of the valve control system, the regulation of the system is achieved.

[0010] Furthermore, the heat-driven Rankine cycle system includes a first condenser, a second condenser, a liquid storage tank, and a pump. The fluid at the cold end outlet enters the second condenser for condensation, the fluid at the hot end outlet enters the second condenser after flowing through the heat exchanger and condenses, the fluid after condensing through the second condenser enters the liquid storage tank, the fluid flowing out of the expander enters the first condenser for condensation, the fluid after condensing through the first condenser enters the liquid storage tank, and the liquid in the liquid storage tank is pressurized by the pump and enters the generator.

[0011] Furthermore, the system uses dry working fluid. Using dry working fluid can avoid gas-liquid phase transition caused by working condition changes in some equipment, such as avoiding pressure reduction and liquefaction of working fluid in the nozzle of vortex tube 13 and expander 16, thereby avoiding liquid hammer problem of equipment.

[0012] Furthermore, the dry working fluid is R245fa or R365mfc.

[0013] Furthermore, temperature and pressure monitoring elements are provided at the inlet and outlet of the expander, and the relative opening of the valve is controlled based on the superheat of the working fluid at the inlet and outlet of the expander. Temperature monitoring elements, such as temperature and pressure elements, are provided at the inlet and outlet of the expander to ensure the working fluid is in a superheated state, so that the working fluid at the inlet and outlet of the expander 16 is kept in a superheated state.

[0014] Furthermore, the cold flow ratio of the vortex tube is selected to be 0.7 to 0.8.

[0015] Furthermore, the ratio of the cross-sectional area of ​​the high-pressure end to the cross-sectional area of ​​the low-pressure end is 1:2 to 1:3.

[0016] Furthermore, a plurality of supercharger assemblies are arranged in parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a diagram of a common Rankine cycle system.

[0018] Figure 2 This is a schematic diagram of a heat-driven Rankine cycle system of the present invention.

[0019] Figure 3 This is a schematic diagram of another heat-driven Rankine cycle system of the present invention.

[0020] Figure 4 It is a schematic diagram of the TS diagram of the dry working fluid described in this article. DETAILED DESCRIPTION

[0021] Figure 2 The figure shows a heat-driven Rankine cycle system, which includes a generator 11, a booster assembly 12, a vortex tube 13, a heat exchanger 14, a first condenser 15, an expander 16, a second condenser 17, a liquid storage tank 18, a pump 19, a valve 10, and pipes connecting the various components.

[0022] There is a two-phase saturated working medium in the generator 11. The generator 11 uses low-grade energy as a heat source to heat the two-phase saturated working medium to generate saturated steam.

[0023] The supercharger assembly 12 includes a supercharger 121 and a valve control system 120 . The valve control system 120 includes a first control valve 122 , a second control valve 123 , a third control valve 124 , and a fourth control valve 125 .

[0024] Supercharger 121 includes a body 1210, a piston 1213, and a spring 1216. Body 1210 defines a low-pressure chamber 1211 and a high-pressure chamber 1212. Piston 1213 divides low-pressure chamber 1211 and high-pressure chamber 1212. Piston 1213 includes a low-pressure end 1214 and a high-pressure end 1215. The cross-sectional area of ​​low-pressure end 1214 corresponds to the cross-sectional area of ​​low-pressure chamber 1211, while the cross-sectional area of ​​high-pressure end 1215 corresponds to the cross-sectional area of ​​high-pressure chamber 1212. The cross-sectional area of ​​low-pressure end 1214 is greater than that of high-pressure end 1215. The ratio of the cross-sectional area of ​​low-pressure end 1214 to that of high-pressure end 1215 can be determined during design based on the design operating conditions. During equipment production, the ratio is generally designed to be between 2:1 and 3.1. One end of the spring 1216 abuts against the piston, and the other end abuts against the body 1210. Therefore, as the piston moves, the spring 1216 changes state from compressed to stretched. The spring 1216 can increase the volume of the high-pressure chamber 1212 under certain conditions.

[0025] The vortex tube 13 includes a high-pressure gas source inlet 131 , a cold end outlet 132 , and a hot end outlet 133 .

[0026] Part of the high-temperature, high-pressure steam generated by the generator 11 flows into the high-pressure gas source inlet 131 of the vortex tube 13 through a pipeline connection, part of it flows into the low-pressure chamber 1211 of the supercharger 121 through a pipeline connection, and part of it flows into the high-pressure chamber 1212 of the supercharger 121 through a pipeline connection.

[0027] The valve element 10 is disposed in the pipeline between the generator 11 and the high-pressure gas source inlet 131 of the vortex tube 13, controlling the flow rate of fluid flowing from the generator 11 into the high-pressure gas source inlet 131. By controlling the opening of the valve element 10, the working fluid pressure in the pipeline after the third control valve 124 is greater than the working fluid pressure after the valve element 10, ensuring that the working fluid flowing out of the low-pressure chamber 1211 of the supercharger can flow smoothly into the high-pressure gas source inlet 131 of the vortex tube 13. The pipeline between the generator 11 and the high-pressure gas source inlet 131 of the vortex tube 13 is provided to regulate and control the operating flow rate of the vortex tube 13, so that the flow rate at the hot end outlet 133 can match the heat demand of the heat exchanger 14.

[0028] The first control valve 122 is provided on the pipeline between the generator 11 and the low-pressure chamber 1211 to control the flow of fluid from the generator 11 into the low-pressure chamber 1211. The second control valve 123 is provided on the pipeline between the generator 11 and the high-pressure chamber 1212 to control the flow of fluid from the generator 11 into the high-pressure chamber 1212.

[0029] The third control valve 124 is provided on the pipeline between the vortex tube 13 and the low-pressure chamber 1211 to control the flow of fluid from the low-pressure chamber 1211 into the vortex tube 13. The fourth control valve 125 is provided on the pipeline between the heat exchanger 14 and the high-pressure chamber 1212 to control the flow of fluid from the high-pressure chamber 1212 into the heat exchanger 14.

[0030] The fluid flowing out of the high pressure chamber 1212 is defined as the working fluid.

[0031] The fluid flowing out of the cold end outlet 132 of the vortex tube 13 is called cold fluid, and the cold fluid enters the second condenser 17 for condensation. The fluid flowing out of the hot end outlet 133 of the vortex tube 13 is called high-temperature fluid. The high-temperature fluid enters the heat exchanger 14 to heat the working fluid in the heat exchanger 14, then flows out of the heat exchanger 14 and enters the second condenser 17 for condensation. The fluid condensed by the second condenser 17 enters the liquid storage tank 18. The cold fluid and the high-temperature fluid passing through the heat exchanger 14 can be mixed before entering the second condenser 17, or they can enter the second condenser 17 separately. The hot end outlet 133 can be provided with a hot end regulating valve 1331 to control the fluid state of the fluids at the cold end outlet 132 and the hot end outlet 133.

[0032] The vortex tube cold flow ratio is selected to be 0.7 to 0.8, which has a better effect and can achieve a temperature separation of hot and cold working media greater than 100°C under certain working conditions.

[0033] The working fluid exiting heat exchanger 14 is at high temperature and pressure and enters expander 16 to perform external work. Temperature monitoring elements, such as temperature and pressure sensors, are installed at the inlet and outlet of expander 16 to ensure the working fluid is in a superheated state. The superheat level is set based on the specific properties of the working fluid. For example, for R245fa, the superheat level is set to no less than 5°C. Furthermore, the relative opening of valve element 10 is controlled based on the superheat level of the working fluid at the inlet and outlet of expander 16.

[0034] The working fluid flowing out of the expander 16 enters the first condenser 15 to be condensed, and the condensed working fluid enters the liquid storage tank 18 .

[0035] The liquid in the liquid storage tank 18 is pressurized by the pump 19 and enters the generator 11.

[0036] The system uses dry working fluids, such as R245fa, R365mfc, etc., to avoid gas-liquid phase transition caused by working fluid condition changes in some equipment, such as avoiding pressure reduction and liquefaction of working fluid in the nozzle of vortex tube 13 and expander 16, thereby avoiding liquid hammer problems in the equipment. In this article, dry working fluid refers to the reciprocal of the slope of the saturated steam line on the temperature-entropy diagram is positive (ζ=dS / dT>0), and its TS diagram is as follows Figure 4 shown.

[0037] Figure 1 The specific principles of the illustrated embodiment are as follows:

[0038] During the high-pressure exhaust stroke of the supercharger, the first control valve 122 and the fourth control valve 125 are opened, the second control valve 123 and the third control valve 124 are closed, the low-pressure working fluid flows from the generator into the low-pressure chamber 1211 of the supercharger body, and the high-pressure working fluid flows out from the high-pressure chamber 1212 of the supercharger body.

[0039] When the pressure of the working fluid in the high-pressure chamber 1212 of the supercharger body is equal to that in the low-pressure chamber 1211 of the supercharger body, the flow of the working fluid flowing from the generator 11 into the low-pressure chamber 1211 of the supercharger body is continued to be controlled by controlling the opening of the first control valve 122, and the second control valve 123 is closed. Since the cross-sectional area of ​​the low-pressure end piston 1214 is larger than the cross-sectional area of ​​the high-pressure end piston 1215, the supercharger piston assembly moves under the driving force of the difference in the working fluid acting on the piston in the high-pressure chamber 1212 of the supercharger body and the low-pressure chamber 1211 of the supercharger body, thereby achieving the pressure-boosting treatment of the working fluid in the high-pressure chamber 1212 of the supercharger body. At this time, the movement of the supercharger piston assembly causes the spring 1216 to respond to the change in tension or compression state ( Figure 1 The spring is in a stretched state in the embodiment shown, but may be in a compressed state in other embodiments).

[0040] During the supercharger's high-pressure intake stroke, the first and fourth control valves 122 and 125 are closed, while the second and third control valves 123 and 124 are open. The working fluid in the supercharger's low-pressure chamber 1211 flows toward the vortex tube's high-pressure air source inlet 131, reducing the working fluid pressure within the supercharger's low-pressure chamber 1211. Saturated working fluid from the generator 11 flows into the supercharger's high-pressure chamber 1212, replenishing the working fluid within. Furthermore, spring 1216 partially powers the supercharger's piston assembly.

[0041] During system operation, the control strategies of the first control valve 122 , the second control valve 123 , the third control valve 124 , the fourth control valve 125 and the valve element 10 need to be determined according to actual operating conditions.

[0042] It should be noted that in this article, the valve component 10, the first control valve 122, the second control valve 123, the third control valve 124, and the fourth control valve 125 can be selected according to actual needs, and mainly valves with adjustable opening and controllable opening and closing states are selected to meet the working condition adjustment requirements such as working fluid flow and pressure.

[0043] Figure 1 In the embodiment shown, when the working fluid R245fa is selected, the heat source temperature is 70 degrees Celsius, the generator generates a pressure of 609.33 kPa, and the pressure after passing through the booster (the boost ratio is designed to be 1:3) is 1,827.99 kPa. The hot fluid is heated to 125 degrees Celsius after eddy temperature separation, expanded to 178 kPa by the expander and drives the expander to do work (generate electricity).

[0044] exist Figure 1 In the embodiment shown, the number of the supercharger assembly 12 is 1, and the operation is intermittent. In order to compensate for the intermittent operation of the supercharger and ensure the continuity of the generator set operation, in another embodiment, multiple supercharger assemblies 12 can be set in parallel, such as Figure 3 That is, this is an embodiment in which the number of supercharger assemblies 12 is two (the parallel branches are provided with control valves 21 and 22). Figure 3 In the embodiment shown, when the working fluid is R365mfc, the heat source temperature is 80°C, the generator generates a pressure of 351.81 kPa, and the pressure after passing through the booster (the boost ratio is designed to be 1:3) is 1055.43 kPa, which expands to 70 kPa and drives the expander to do work (generate electricity).

[0045] It should be noted that the "high temperature", "high pressure", "low temperature" and "low pressure" in this article are determined according to their relative sizes in the system and do not represent a specific temperature range or pressure range. For example, if the gas is heated, it is low temperature before heating and high temperature after heating.

Claims

1. A heat-driven Rankine cycle system, characterized in that: The invention comprises a generator, a booster assembly, a vortex tube, a heat exchanger, an expander and a valve. The generator has a two-phase saturated working medium. The generator uses low-grade energy to heat the liquid working medium to generate saturated steam. The booster assembly comprises a booster and a valve control system. The booster comprises a body, a piston and a spring. The body is provided with a low-pressure chamber and a high-pressure chamber. The piston isolates the low-pressure chamber and the high-pressure chamber. The piston comprises a low-pressure end and a high-pressure end. The cross-sectional area of ​​the low-pressure end is adapted to the cross-sectional area of ​​the low-pressure chamber, and the cross-sectional area of ​​the high-pressure end is adapted to the cross-sectional area of ​​the high-pressure chamber. The cross-sectional area of ​​the low-pressure end is larger than the cross-sectional area of ​​the high-pressure end. Thus, when the pressures of the low-pressure chamber and the high-pressure chamber are equal, the piston compresses the fluid in the high-pressure chamber. One end of the spring abuts against the piston, and the other end abuts against the body. Under certain conditions, the spring can drive the piston to move and increase the volume of the high-pressure chamber. The valve control system can control the saturated steam generated by the generator to enter the low-pressure chamber or the high-pressure chamber, and can also control the outflow of fluid in the low-pressure chamber or the high-pressure chamber. The vortex tube includes a high-pressure gas source inlet, a cold end outlet, and a hot end outlet. The fluid flowing out of the low-pressure chamber enters the high-pressure gas source inlet. The fluid flowing out of the high-pressure chamber is defined as the working fluid. The fluid flowing out of the hot end outlet enters the heat exchanger to heat the working fluid, so that the working fluid is in a high-temperature and high-pressure state. The working fluid flowing out of the heat exchanger then enters the expander to perform external work. The fluid flowing out of the cold end outlet and the fluid flowing out of the expander flow back to the generator after treatment. The valve component controls the flow of high-temperature, high-pressure steam generated by the generator into the high-pressure gas source inlet.

2. The heat-driven Rankine cycle system according to claim 1, characterized in that: The valve control system includes a first control valve, a second control valve, a third control valve, and a fourth control valve. The first control valve is arranged on the pipeline between the generator and the low-pressure chamber to control the fluid flow rate of the generator flowing into the low-pressure chamber. The second control valve is arranged on the pipeline between the generator and the high-pressure chamber to control the fluid flow rate of the generator flowing into the high-pressure chamber. The third control valve is arranged on the pipeline between the vortex tube and the low-pressure chamber to control the fluid flow rate from the low-pressure chamber to the vortex tube. The fourth control valve is arranged on the pipeline between the heat exchanger and the high-pressure chamber to control the flow rate from the high-pressure chamber to the heat exchanger. The valve component is arranged on the pipeline between the generator and the high-pressure gas source inlet.

3. The heat-driven Rankine cycle system according to claim 2, characterized in that: It includes a first condenser, a second condenser, a liquid storage tank, and a pump. The fluid at the cold end outlet enters the second condenser for condensation, the fluid at the hot end outlet enters the second condenser after flowing through the heat exchanger and condenses, the fluid after condensing through the second condenser enters the liquid storage tank, the fluid flowing out of the expander enters the first condenser for condensation, the fluid after condensing through the first condenser enters the liquid storage tank, and the liquid in the liquid storage tank enters the generator after being pressurized by the pump.

4. The heat-driven Rankine cycle system according to any one of claims 1 to 3, characterized in that: The system working fluid is dry working fluid.

5. The heat-driven Rankine cycle system according to claim 4, characterized in that: The dry working fluid is R245fa or R365mfc.

6. The heat-driven Rankine cycle system according to claim 4, characterized in that: Temperature and pressure monitoring elements are provided at the inlet and outlet of the expander, and the relative opening of the valve is controlled based on the superheat of the working medium at the inlet and outlet of the expander.

7. The heat-driven Rankine cycle system according to any one of claims 1 to 3, characterized in that: The cold flow ratio of the vortex tube is selected to be 0.7 to 0.

8.

8. The heat-driven Rankine cycle system according to any one of claims 1 to 3, characterized in that: The ratio of the cross-sectional area of ​​the high-pressure end to the cross-sectional area of ​​the low-pressure end is 1:2 to 1:

3.

9. The heat-driven Rankine cycle system according to any one of claims 1 to 3, characterized in that: Multiple booster assemblies are arranged in parallel.

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