Dual-pressure organic Rankine-two-stage steam compression heat pump system and power control method

Abstract

The present invention discloses a dual-pressure organic Rankine-two-stage steam compression heat pump system and a power control method, which belongs to the technical field of high-temperature heat pumps, and includes a dual-pressure series organic Rankine cycle subsystem, the dual-pressure series organic Rankine cycle subsystem is connected to a hybrid gearbox subsystem, the hybrid gearbox subsystem is connected to a two-stage steam compression heat pump subsystem, and the dual-pressure series organic Rankine cycle subsystem includes a high-pressure generator and a low-pressure generator, and the high-pressure generator and the low-pressure generator are respectively connected to a high-pressure expander and a low-pressure expander. The present invention adopts the above-mentioned dual-pressure organic Rankine-two-stage steam compression heat pump system and power control method, adopts a hybrid gearbox as a transmission and power coupling device, introduces solar cells as an auxiliary energy source, achieves optimal efficiency and power performance, adopts a dual-pressure organic Rankine cycle plus a preheater, realizes the cascade utilization of heat from a low-temperature heat source, improves the thermal efficiency of the system, and reduces heat transfer losses, and adopts a two-stage steam compression heat pump system plus an intercooler, so that the system operates efficiently and stably.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature heat pumps, and in particular to a dual-pressure organic Rankine-two-stage steam compression heat pump system and a power control method. Background Art

[0002] Organic Rankine cycle (ORC) is a power technology that uses low-boiling-point organic fluid as working fluid to achieve efficient thermoelectric or heat-to-work conversion of medium- and low-temperature thermal energy. The dual-pressure series organic Rankine cycle is an emerging cycle type in the field of organic Rankine cycle, including two series-connected processes at different pressures and two expansion work processes at different pressures. The dual-pressure evaporation cycle can greatly reduce the irreversible loss in the endothermic process and has better applicability to heat sources with complex exothermic characteristics and large fluctuations.

[0003] Two-stage steam compression heat pump is a heat pump technology that uses two steam compression cycles at different pressures to improve the efficiency and performance of the heat pump. The so-called incomplete intermediate cooling refers to the cooling process in which the superheated steam discharged from the low-pressure compressor is cooled by an intercooler to reduce the temperature by a certain amount without reaching the saturation state.

[0004] In the prior art, a geothermal driven organic Rankine-single-stage compression refrigeration system is proposed. The system mainly includes an organic Rankine cycle (ORC) part that provides power and a vapor compression refrigeration (VCR) part. During the operation of the system, there are large The loss of heat exchanger The loss is mainly caused by the large heat transfer temperature difference, especially in the low temperature heat exchanger. The loss is greater. When the evaporation temperature is greatly different from the condensation temperature, the compression ratio of the compressor will be too large, resulting in a decrease in the compressor gas transmission coefficient, and the actual compression process deviates from the isentropic process to a greater extent, thus causing the system to experience performance degradation, increased power consumption, decreased efficiency, and reduced performance coefficient. In addition, in this system, the expander and the compressor are directly coaxially connected, and the output work of the expander cannot fully match the work required by the compressor. Under different operating conditions, the output work of the expander may be greater than the compression work of the compressor, and the output work of the expander may be redundant and wasted; it may also be that when the heat source temperature is low, the output work of the expander is insufficient to support the compression work of the compressor. Therefore, the direct connection between the expander and the compressor may cause the operating range of the expander and the compressor to be smaller, the output work of the expander cannot fully match the work required by the compressor, and under variable operating conditions, the stable and efficient operation of the compressor cannot be guaranteed, so the stability and efficiency of the system cannot be guaranteed. Summary of the invention

[0005] The purpose of the present invention is to provide a dual-pressure organic Rankine-two-stage steam compression heat pump system and a power control method, using a hybrid gearbox as a transmission and power coupling device between the two, and introducing solar cells as an auxiliary energy source to achieve optimal system efficiency and power performance, using a dual-pressure series organic Rankine cycle and adding a preheater, realizing the cascade utilization of low-temperature heat source heat, improving system thermal efficiency, and reducing heat transfer In order to reduce losses, a two-stage steam compression heat pump system is adopted and an intercooler is installed to achieve efficient and stable operation of the system.

[0006] To achieve the above-mentioned objectives, the present invention provides a dual-pressure organic Rankine-two-stage steam compression heat pump system, comprising a dual-pressure series organic Rankine cycle subsystem, the dual-pressure series organic Rankine cycle subsystem is connected to a hybrid transmission subsystem, the hybrid transmission subsystem is connected to a two-stage steam compression heat pump subsystem, the dual-pressure series organic Rankine cycle subsystem comprises a high-pressure generator and a low-pressure generator, the high-pressure generator and the low-pressure generator are respectively connected to a high-pressure expander and a low-pressure expander.

[0007] Preferably, the high-pressure generator is connected to the high-pressure working fluid pump, the high-pressure working fluid pump and the low-pressure generator are both connected to the preheater, the preheater is connected to the low-pressure working fluid pump, the low-pressure working fluid pump is connected to the condenser, the condenser is connected to the low-pressure expander, and the low-pressure expander is connected to the high-pressure expander.

[0008] Preferably, the two-stage steam compression heat pump circulation subsystem includes a high-pressure compressor, which is respectively connected to a condenser, an intercooler and a low-pressure compressor, the condenser is respectively connected to the intercooler and a second throttle valve, the second throttle valve is connected to the intercooler, the intercooler is connected to the first throttle valve, the first throttle valve is connected to the evaporator, and the evaporator is connected to the low-pressure compressor.

[0009] Preferably, the hybrid transmission subsystem includes a battery, which is a solar cell, and the battery is connected to a generator and a motor respectively. The generator is connected to a high-pressure expander and a low-pressure expander respectively through a first transmission gear and a second transmission gear, and the high-pressure expander and the low-pressure expander are connected to a first clutch and a second clutch respectively, and the motor is connected to the drive shafts of the high-pressure compressor and the low-pressure compressor respectively through a third clutch, a third transmission gear and a fourth transmission gear.

[0010] Preferably, the first clutch is connected to the high-pressure expander and the first transmission respectively, the first transmission is connected to the high-pressure compressor, the second clutch is connected to the low-pressure expander and the second transmission respectively, and the second transmission is connected to the low-pressure compressor.

[0011] A power control method for a dual-pressure organic Rankine-two-stage steam compression heat pump system comprises the following steps:

[0012] The temperature information of the heat source is obtained by temperature measurement, and the first judgment is made to determine whether the temperature of the heat source is greater than 60°C;

[0013] When the first judgment result is no, the first clutch and the second clutch are disconnected, the third clutch is closed, and the hybrid transmission operates in series mode;

[0014] When the first judgment result is yes, the first clutch and the second clutch are closed, and a second judgment is performed based on the heat source temperature to determine whether the heat source temperature is greater than 70°C;

[0015] When the second judgment result is negative, the third clutch is closed and the hybrid transmission operates in parallel mode;

[0016] When the second judgment result is yes, the third clutch is disconnected, and the high-pressure compressor and the low-pressure compressor are completely driven by the high-pressure expander and the low-pressure expander respectively.

[0017] Therefore, the present invention adopts the above-mentioned dual-pressure organic Rankine-two-stage steam compression heat pump system and power control method, which has the following beneficial effects:

[0018] (1) The present invention adopts a hybrid transmission as a transmission and power coupling device between the two, and introduces solar cells as auxiliary energy sources; the expander is used to provide power, and the electric motor is used to provide auxiliary power. The two can work simultaneously or separately to achieve optimal system efficiency and power performance. The present invention also proposes a power control strategy based on the hybrid transmission to ensure stable and efficient operation of the system.

[0019] (2) The present invention adopts a dual-pressure series organic Rankine cycle and adds a preheater to achieve the cascade utilization of the heat of the low-temperature heat source, improve the thermal efficiency of the system, and reduce the heat transfer loss.

[0020] (3) The steam compression cycle side of the present invention is used to produce high-temperature steam above 100°C; and the present invention adopts a two-stage steam compression heat pump system and adds an intermediate cooler, which not only realizes efficient and stable operation of the system, but also can be coupled with a dual-pressure organic Rankine cycle to realize that the high-pressure expander drives the high-pressure compressor and the low-pressure expander drives the low-pressure compressor.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a dual-pressure organic Rankine-two-stage steam compression heat pump system of an embodiment of a dual-pressure organic Rankine-two-stage steam compression heat pump system and a power control method of the present invention;

[0023] Figure 2 It is a flow chart of a control method of a dual-pressure organic Rankine-two-stage steam compression heat pump system and a power control method embodiment of the present invention.

[0024] Reference numerals

[0025] 1. Condenser; 2. Low-pressure working fluid pump; 3. Preheater; 4. High-pressure working fluid pump; 5. Low-pressure generator; 6. High-pressure generator; 7. High-pressure expander; 8. Low-pressure expander; 9. First clutch; 10. Second clutch; 11. Generator; 12. Battery; 13. Motor; 14. Third clutch; 15. First transmission; 16. Second transmission; 17. First transmission gear; 18. Second transmission gear; 19. Third transmission gear; 20. Fourth transmission gear; 21. High-pressure compressor; 22. Condenser; 23. Second throttle valve; 24. Intercooler; 25. First throttle valve; 26. Evaporator; 27. Low-pressure compressor. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0027] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0028] Embodiment 1

[0029] like Figure 1 As shown, the present invention provides a dual-pressure organic Rankine-two-stage steam compression heat pump system, including a dual-pressure series organic Rankine cycle subsystem, the dual-pressure series organic Rankine cycle subsystem is connected to a hybrid transmission subsystem, and the hybrid transmission subsystem is connected to a two-stage steam compression heat pump subsystem. The dual-pressure series organic Rankine cycle subsystem realizes the cascade utilization of heat from the heat source, can better realize the recovery and utilization of low-temperature waste heat, can effectively reduce the heat transfer temperature difference in the cycle endothermic process, and reduce the heat transfer The hybrid transmission subsystem can adopt different working modes such as series connection, parallel connection or single expansion machine drive when the working conditions such as heat source temperature change, which expands the working range of the high-pressure expansion machine 7 and the low-pressure expansion machine 8 on the organic Rankine side and ensures that the output power can be effectively utilized. The two-stage steam compression heat pump subsystem can reduce throttling losses and reduce heat transfer. loss, thus improving the balance and stability of the system and improving the efficiency of the system.

[0030] The dual-pressure series organic Rankine cycle subsystem includes a condenser 1, which can condense gas into water. The condenser 1 is connected to a low-pressure working fluid pump 2, which is connected to a preheater 3, and the low-pressure working fluid pump 2 can pressurize the liquid organic working fluid. The preheater 3 is connected to a high-pressure working fluid pump 4 and a low-pressure generator 5, and the preheater 3 can preheat the liquid organic working fluid. The high-pressure working fluid pump 4 is connected to a high-pressure generator 6, and the high-pressure working fluid pump 4 can pressurize the liquid organic working fluid to make it a liquid organic working fluid with a higher pressure. The high-pressure generator 6 is connected to a high-pressure expander 7, and the high-pressure generator 6 causes the liquid organic working fluid pressurized by the high-pressure working fluid pump 4 to absorb heat and evaporate into an organic working fluid vapor with a higher temperature and pressure. The low-pressure generator 5 is connected to the low-pressure expander 8, which will make the liquid organic working medium pressurized by the low-pressure working medium pump 2 and preheated by the preheater 3 absorb heat and evaporate to become organic working medium steam, and the high-pressure expander 7 will be driven to do work by the organic working medium steam generated by the high-pressure generator 6. The low-pressure expander 8 is connected to the high-pressure expander 7 and the condenser 1, and the low-pressure expander 8 will be driven to do work by the steam exhaust gas after the high-pressure expander 7 does work and the steam generated in the low-pressure generator 5.

[0031] The two-stage steam compression heat pump circulation subsystem includes a high-pressure compressor 21, which compresses the high-temperature and high-pressure organic working fluid vapor. The high-pressure compressor 21 is connected to the condenser 22, the intercooler 24 and the low-pressure compressor 27 respectively, and the condenser 22 condenses the organic working fluid vapor compressed by the high-pressure compressor 21 into an organic working fluid liquid. The condenser 22 is connected to the intercooler 24 and the second throttle valve 23 respectively, and the second throttle valve 23 is connected to the intercooler 24. The intercooler 24 can exchange heat between the two parts of the throttled and unthrottled organic working fluids, and the second throttle valve 23 can throttle and reduce the pressure of the organic working fluid, and control the flow rate of the organic working fluid liquid to the intercooler 24. The intercooler 24 is connected to the first throttle valve 25, and the first throttle valve 25 is connected to the evaporator 26. The first throttle valve 25 can throttle and reduce the pressure of the organic working fluid, and control the flow rate of the organic working fluid liquid to the evaporator 26. The evaporator 26 is connected to the low-pressure compressor 27. The evaporator 26 can allow the organic working fluid liquid to absorb heat and evaporate, and the low-pressure compressor 27 can compress the organic working fluid vapor.

[0032] The hybrid transmission subsystem includes a battery 12, which is a solar cell. The battery 12 is connected to the generator 11 and the motor 13 respectively. The solar energy or the generator 11 can be used to supplement the battery 12 with electricity, and the battery 12 provides electricity for the motor 13. The generator 11 is connected to the high-pressure expander 7 and the low-pressure expander 8 through the first transmission gear 17 and the second transmission gear 18 respectively. The high-pressure expander 7 and the low-pressure expander 8 are connected to the first clutch 9 and the second clutch 10 respectively. The first clutch 9 is connected to the high-pressure expander 7, and the second clutch 10 is connected to the low-pressure expander 8. The high-pressure expander 7 and the low-pressure expander 8 can drive the generator 11 to generate electricity through the first transmission gear 17 and the second transmission gear 18 when the high-pressure expander 7 and the low-pressure expander 8 do work. The motor 13 is connected to the drive shafts of the high-pressure compressor 21 and the low-pressure compressor 27 through the third clutch 14, the third transmission gear 19 and the fourth transmission gear 20 respectively. The motor can drive the high-pressure compressor 21 and the low-pressure compressor 27 to do work through the third clutch 14, the third transmission gear 19 and the fourth transmission gear 20. The third clutch 14 can interrupt the power transmission. The first clutch 9 is connected to the high-pressure expander 7 and the first transmission 15 respectively, the first transmission 15 is connected to the high-pressure compressor 21, the second clutch 10 is connected to the low-pressure expander 8 and the second transmission 16, the second transmission 16 is connected to the low-pressure compressor 27, and the first clutch 9 and the second clutch 10 can interrupt power transmission.

[0033] Working principle: After the organic working fluid comes out of the condenser 1, it is pressurized by the low-pressure working fluid pump 2 and then sent to the preheater 3 for preheating; a part of the preheated organic working fluid liquid directly enters the low-pressure generator 5 to absorb heat and evaporate to become organic working fluid steam; the other part is pressurized by the high-pressure working fluid pump 4 and enters the high-pressure generator 6 to absorb heat and evaporate to become organic working fluid steam with higher temperature and pressure. This part of the organic working fluid steam is sent to the high-pressure expander 7 to drive the high-pressure expander 7 to do work; the steam exhaust gas after doing work in the high-pressure expander 7 is mixed with the steam generated in the low-pressure generator 5 and then enters the low-pressure expander 8 to drive the low-pressure expander 8 to do work; the steam exhaust gas after doing work in the low-pressure expander 8 is sent to the condenser 1 to condense and become an organic working fluid liquid again, completing the double-pressure series organic Rankine cycle.

[0034] The high-temperature and high-pressure organic working fluid is compressed by the high-pressure compressor 21 and then sent to the condenser 22 to be condensed into an organic working fluid liquid; a part of the liquid working fluid coming out of the condenser 22 is directly sent to the intercooler 24, and the other part is throttled by the second throttle valve 23 and enters the intercooler 24, the two parts of the working fluid exchange heat in the intercooler 24, the throttled working fluid is heated by the unthrottled working fluid and becomes steam again and is sent to the high-pressure compressor 21 for compression; the unthrottled working fluid liquid releases heat in the intercooler 24 and is throttled by the first throttle valve 25 and then sent to the evaporator 26 to absorb heat and evaporate, the organic working fluid vapor coming out of the evaporator 26 is sent to the low-pressure compressor 27 for compression, the organic working fluid vapor compressed by the low-pressure compressor 27 is mixed with the organic working fluid vapor coming out of the intercooler 24 and sent to the high-pressure compressor 21 for compression, completing the intermediate incomplete cooling two-stage steam compression heat pump cycle.

[0035] The hybrid transmission includes two operating modes: series and parallel. The series mode means that the first clutch 9 is disconnected and the third clutch 14 is closed. The output work of the high-pressure expander 7 drives the generator 11 to generate electricity through the first transmission gear 17. The generated electric energy is stored in the battery 12. The battery 12 then outputs electric energy to drive the motor 13 to do work, which drives the high-pressure compressor 21 to operate after being adjusted by the third transmission gear 19 and the first transmission 15.

[0036] The parallel mode means that the first clutch 9 and the third clutch 14 are both closed, and the battery 12 outputs electrical energy to drive the work done by the motor 13 and the output work of the high-pressure expander 7, which are adjusted by the third transmission gear 19 and the first transmission 15 to drive the high-pressure compressor 21 to operate together.

[0037] like Figure 2 As shown, the present invention provides a power control method for a dual-pressure organic Rankine-two-stage steam compression heat pump system, comprising the following steps:

[0038] The temperature information of the heat source is obtained by temperature measurement, and the first judgment is made to determine whether the temperature of the heat source is greater than 60°C;

[0039] When the first judgment result is negative, the first clutch 9 and the second clutch 10 are disconnected, the third clutch 14 is closed, and the hybrid transmission operates in series mode;

[0040] When the first judgment result is yes, the first clutch 9 and the second clutch 10 are closed, and a second judgment is performed based on the heat source temperature to determine whether the heat source temperature is greater than 70°C;

[0041] When the second judgment result is negative, the third clutch 14 is closed, and the hybrid transmission operates in parallel mode;

[0042] When the second judgment result is yes, the third clutch 14 is disconnected, and the high-pressure compressor 21 and the low-pressure compressor 27 are completely driven by the high-pressure expander 7 and the low-pressure expander 8 respectively.

[0043] Therefore, the present invention adopts the above-mentioned dual-pressure organic Rankine-two-stage steam compression heat pump system and power control method, adopts a hybrid gearbox as a transmission and power coupling device between the two, and introduces solar cells as an auxiliary energy source to achieve the best system efficiency and power performance. The dual-pressure series organic Rankine cycle and the addition of a preheater realize the cascade utilization of the heat of the low-temperature heat source, improve the thermal efficiency of the system, and reduce the heat transfer. In order to reduce losses, a two-stage steam compression heat pump system is adopted and an intercooler is installed to achieve efficient and stable operation of the system.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. Double-pressure organic Rankine-two-stage steam compression heat pump system, characterized in that: It includes a dual-pressure series organic Rankine cycle subsystem, which is connected to a hybrid transmission subsystem, which is connected to a two-stage steam compression heat pump subsystem, and the dual-pressure series organic Rankine cycle subsystem includes a high-pressure generator and a low-pressure generator, which are respectively connected to a high-pressure expander and a low-pressure expander; The two-stage steam compression heat pump circulation subsystem comprises a high-pressure compressor, the high-pressure compressor is respectively connected to a condenser, an intercooler and a low-pressure compressor, the condenser is respectively connected to an intercooler and a second throttle valve, the second throttle valve is connected to the intercooler, the intercooler is connected to a first throttle valve, the first throttle valve is connected to an evaporator, and the evaporator is connected to the low-pressure compressor; The hybrid transmission subsystem includes a battery, which is a solar cell, and the battery is connected to a generator and a motor respectively, and the generator is connected to a high-pressure expander and a low-pressure expander respectively through a first transmission gear and a second transmission gear, and the high-pressure expander and the low-pressure expander are connected to a first clutch and a second clutch respectively, and the motor is connected to a drive shaft of the high-pressure compressor and the low-pressure compressor respectively through a third clutch, a third transmission gear and a fourth transmission gear; The first clutch is connected to the high-pressure expander and the first transmission respectively, the first transmission is connected to the high-pressure compressor, the second clutch is connected to the low-pressure expander and the second transmission respectively, and the second transmission is connected to the low-pressure compressor.

2. The dual-pressure organic Rankine-two-stage vapor compression heat pump system according to claim 1, characterized in that: The high-pressure generator is connected to the high-pressure working fluid pump, the high-pressure working fluid pump and the low-pressure generator are both connected to the preheater, the preheater is connected to the low-pressure working fluid pump, the low-pressure working fluid pump is connected to the condenser, the condenser is connected to the low-pressure expander, and the low-pressure expander is connected to the high-pressure expander.

3. A power control method for a dual-pressure organic Rankine-two-stage steam compression heat pump system according to any one of claims 1 to 2, characterized in that: The following steps are involved: The temperature information of the heat source is obtained by temperature measurement, and the first judgment is made to determine whether the temperature of the heat source is greater than 60°C; When the first judgment result is no, the first clutch and the second clutch are disconnected, the third clutch is closed, and the hybrid transmission operates in series mode; When the first judgment result is yes, the first clutch and the second clutch are closed, and a second judgment is performed based on the heat source temperature to determine whether the heat source temperature is greater than 70°C; When the second judgment result is negative, the third clutch is closed and the hybrid transmission operates in parallel mode; When the second judgment result is yes, the third clutch is disconnected, and the high-pressure compressor and the low-pressure compressor are completely driven by the high-pressure expander and the low-pressure expander respectively.

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