阅读说明：本技术 替代混合工质的叠合有机朗肯循环及其调节方法 (Superimposed organic Rankine cycle for replacing mixed working medium and adjusting method thereof ) 是由 李新国 高冠怡 于 2020-04-16 设计创作，主要内容包括：本发明公开一种替代混合工质的叠合有机朗肯循环及其调节方法,以提高循环对外界热源与冷源的调节性、适应性和提高系统的发电能力。如双工质的叠合有机朗肯循环,系统具体连接与工作流程为：蒸发器、膨胀机A、冷凝器、工质泵A串接构成有机朗肯循环--循环1。蒸发器、膨胀机B、冷凝器、工质泵B构成另一有机朗肯循环--循环2。循环1与循环2采用临界温度不同的工质。不同于混合工质有机朗肯循环,叠合循环中各循环及工质彼此独立,其运行工况(蒸发器温度、冷凝温度与循环流量)可以独立调节,以提高循环的调节性和对外界热源/冷源的传热匹配性及适应性,和提高循环的性能(加热量和热效率)。(The invention discloses an overlapped organic Rankine cycle for replacing a mixed working medium and an adjusting method thereof, which are used for improving the adjustability and the adaptability of the cycle to an external heat source and a cold source and improving the power generation capacity of a system. If the dual-working-medium overlapped organic Rankine cycle is adopted, the specific connection and working process of the system is as follows: the evaporator, the expander A, the condenser and the working medium pump A are connected in series to form an organic Rankine cycle-cycle 1. The evaporator, the expander B, the condenser and the working medium pump B form another organic Rankine cycle, namely a cycle 2. The cycle 1 and the cycle 2 adopt working media with different critical temperatures. Different from mixed working medium organic Rankine cycle, each cycle and working medium in the superposition cycle are independent, and the operation working conditions (the temperature of an evaporator, the condensation temperature and the circulation flow) can be independently adjusted, so that the adjustability of the cycle, the heat transfer matching and adaptability to an external heat source/cold source and the performance (heating amount and heat efficiency) of the cycle are improved.)

1. The superimposed organic Rankine cycle for replacing mixed working media is characterized in that: overlapping working medium organic Rankine cycles with different critical temperatures to form an overlapped cycle:

a circulation loop 1, namely a circulation 1, is formed by an evaporator, an expander A, a condenser and a working medium pump A;

the evaporator, the expander B, the condenser and the working medium pump B form a circulation loop 2, namely a circulation loop 2.

2. The stacked organic rankine cycle of alternative mixed refrigerant according to claim 1, characterized in that: the method comprises an overlapped organic Rankine cycle of double working media, wherein each working medium in the overlapped cycle adopts working media with different critical temperatures.

3. The stacked organic rankine cycle of alternative mixed refrigerant according to claim 1, characterized in that: the laminating cycle employs an evaporator and a condenser. Simultaneously heating, superposing and circulating working media in parallel in the evaporator; all the working mediums which are circulated in the condenser are simultaneously cooled in parallel.

4. The stacked organic Rankine cycle of alternative mixed refrigerant according to any one of claims 1 to 3, characterized in that: the specific process steps are as follows:

1) and (3) circulation 1: the saturated liquid working medium at the outlet of the condenser is pressurized to evaporation pressure by a working medium pump A, then enters the evaporator and is heated to a saturated gas state, the working medium enters an expander A to do work to drive a generator to generate electricity, and exhaust steam at the outlet of the expander A enters the condenser and is condensed and then enters the working medium pump A to form a circulation loop 1;

2) and (3) circulation 2: the saturated liquid working medium at the outlet of the condenser is pressurized to evaporation pressure by the working medium pump B, then enters the evaporator to be heated to a saturated gas state, enters the expander B to do work to drive the generator to generate power, and the exhaust steam at the outlet of the expander B enters the condenser to be condensed and then enters the working medium pump B to form a circulation loop 2.

5. The stacked organic Rankine cycle of alternative mixed refrigerant according to claim 4, characterized in that: the circulation and working medium of the superposition circulation are independent, and the temperature of the evaporator, the condensation temperature and the circulation flow under the operation condition can be independently adjusted.

Technical Field

The invention belongs to the technical field of medium-low temperature heat source power generation, and particularly relates to an overlapped organic Rankine cycle for replacing a mixed working medium and an adjusting method thereof.

Background

In the utilization and conversion of medium-low temperature heat energy, the organic Rankine cycle is an effective technical measure. The existing medium-low temperature heat energy resources are mainly limited heat sources, namely, the temperature of the heat energy resources is gradually reduced along with the utilization of the heat energy; the heat absorption process of the circulating working medium has the change from single phase (liquid phase) to two phases (gas-liquid), and the heat transfer mismatch with the single phase change of a heat source exists greatly, so that the low thermal efficiency and the high efficiency loss of the circulation are caused. At present, a double-stage circulation mode is adopted, but the circulation configuration mostly adopts a step heating mode of a heat source to heat a high-temperature circulation and a low-temperature circulation in sequence, and although the mode improves the heating amount of the circulation and improves the working capacity, the heat efficiency of the circulation is reduced. Therefore, the heat efficiency of the circulation is not reduced and even the heat efficiency is improved while the circulation heating amount is improved, so that the heat efficiency has high significance and application value. The two-phase region of the non-azeotropic mixed working medium has the temperature slippage characteristic, can improve and increase the heat transfer matching property in the heat transfer process, but has the related problems of low heat transfer coefficient, working medium leakage and the like.

Disclosure of Invention

The invention aims to overcome the defects of conventional organic Rankine cycle and mixed working medium organic Rankine cycle in the prior art, provides an overlapped organic Rankine cycle for replacing mixed working medium and an adjusting method thereof, and the overlapped cycle is formed by overlapping the working medium organic Rankine cycles with different critical temperatures. Different from mixed working medium organic Rankine cycle, each cycle and working medium in the superposition cycle are independent, and the operation working conditions (the temperature of an evaporator, the condensation temperature and the circulation flow) of the superposition cycle can be independently adjusted, so that the heat transfer matching performance of the cycle and a heat source/cold source is improved, the cycle performance (heating quantity and heat efficiency) is improved, and the adaptability of the cycle to an external heat source and a cold source is improved.

In order to achieve the purpose, the invention specifically provides a technical scheme of replacing a superposition organic Rankine cycle of a mixed working medium, and a system specifically comprises the following connection methods:

a circulation loop 1 (circulation 1) is formed by an evaporator, an expander A, a condenser and a working medium pump A;

the evaporator, the expander B, the condenser and the working medium pump B form a circulation loop 2 (circulation 2).

The second technical scheme of the invention is a method for adjusting the superimposed organic Rankine cycle for replacing mixed working media, which comprises the following steps:

1) and (3) circulation 1: the saturated liquid working medium at the outlet of the condenser is pressurized to evaporation pressure by the working medium pump A, then enters the evaporator and is heated to a saturated gas state, the working medium enters the expander A to do work to drive the generator to generate electricity, and the exhaust steam at the outlet of the expander A enters the condenser and is condensed and then enters the working medium pump A to form a circulation loop 1.

2) And (3) circulation 2: the saturated liquid working medium at the outlet of the condenser is pressurized to evaporation pressure by the working medium pump B, then enters the evaporator to be heated to a saturated gas state, enters the expander B to do work to drive the generator to generate power, and the exhaust steam at the outlet of the expander B enters the condenser to be condensed and then enters the working medium pump B to form a circulation loop 2.

3) The circulation and working medium of the superposed circulation are independent, and the operation conditions (evaporator temperature, condensation temperature and circulation flow) can be independently adjusted, so that the heat transfer matching performance of the circulation and a heat source/cold source is improved, the circulation performance (heating quantity and heat efficiency) is improved, and the adaptability of the circulation to an external heat source and a cold source is improved.

The invention has the beneficial effects that: the invention provides a method for improving the heat transfer matching of a cycle and a heat source/cold source, improving the cycle performance (heating quantity and heat efficiency) and improving the adaptability of the cycle to an external heat source and a cold source by adopting an overlapped organic Rankine cycle instead of a non-azeotropic mixed working medium organic Rankine cycle.

The heat source heats two cycles simultaneously, so that the heat efficiency of the cycle is not reduced while the heating capacity of the cycle is improved, even the heat efficiency can be improved, the cycle performance is improved, and the utilization rate and the conversion rate of medium-low temperature heat energy are improved. Because the two cycles of the superposed cycle are independent and adjustable, the operation conditions (evaporation/condensation temperature and circulation flow) are independent and adjustable, the superposed cycle has strong adjustability and adaptability, not only can improve the heat transfer matching of the cycle and a heat source/cold source and improve the cycle performance (heating quantity and heat efficiency), but also can improve the adaptability of the cycle to an external heat source, a cold source and load. This is not available with mixed working fluid cycles.

Drawings

FIG. 1 is a schematic diagram of the system of the present invention.

FIG. 2 is a temperature entropy diagram of the working fluid of the system of the present invention.

Reference numerals: 1-evaporator, 2-expander A, 3-expander B, 4-condenser, 5-working medium pump A, 6-working medium pump B.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

The system shown in fig. 1 comprises an evaporator 1, an expander A2, an expander B3, a condenser 4, a working medium pump A5 and a working medium pump B6. The system comprises the following specific connection and working processes: a circulation loop 1 is formed by an evaporator 1, an expander A2, a condenser 4 and a working medium pump A5; the evaporator 1, the expander B3, the condenser 4 and the working medium pump B6 form a circulation loop 2.

The working process of the system of the invention is shown as the attached figure 2:

and (3) circulation 1: the saturated liquid working medium at the outlet of the condenser 4 is pressurized to evaporation pressure by the working medium pump A5, then enters the evaporator 1 and is heated to a saturated gas state, the working medium enters the expander A2 to do work to drive the generator to generate power, and the exhaust steam at the outlet of the expander A2 enters the condenser 4 to be condensed and then enters the working medium pump A5 to form the circulation loop 1.

And (3) circulation 2: the saturated liquid working medium at the outlet of the condenser 4 is pressurized to evaporation pressure by a working medium pump B6, then enters the evaporator 1 and is heated to a saturated gas state, enters the expander B3 to do work to drive the generator to generate power, and the exhaust steam at the outlet of the expander B3 enters the condenser 4 to be condensed and then enters the working medium pump B6 to form a circulation loop 2.

The two cycles of the superimposed cycle and the working medium are independent of each other, and the operation conditions (the temperature of the evaporator 1, the condensation temperature and the circulation flow) of each cycle are adjusted, so that the heat transfer matching performance of the cycle and a heat source/cold source is improved, the cycle performance (heating quantity and heat efficiency) is improved, and the adaptability of the cycle to an external heat source and a cold source is improved. The following is a comparison of the four power generation cycle scenarios.

The first scheme is as follows: in the system, a pure working medium R245fa (pentafluoropropane) is adopted in a cycle 1, and a pure working medium R227ea (heptafluoropropane) is adopted in a cycle 2;

scheme II: an organic Rankine cycle adopting an R245fa/227ea (pentafluoropropane/heptafluoropropane) mixed working medium;

the third scheme is as follows: a heat source is connected in series to heat a double-pressure organic Rankine cycle of pure working medium R245fa (pentafluoropropane);

and the scheme is as follows: a conventional organic Rankine cycle adopts pure working medium R245fa (pentafluoropropane);

calculating conditions: the heat source is represented by hot water at 120 ℃, and the mass flow is 1 kg/s; the inlet temperature of cooling water is 25 ℃, and the outlet temperature is 30 ℃; the isentropic efficiency of the expansion machine is 0.85, and the isentropic efficiency of the working medium pump is 0.8. The four schemes adopt the same conditions of heat source, cold source, isentropic efficiency and the like.

TABLE 1

The first scheme is as follows:

1. and (3) circulation 1: working medium R245fa is adopted, and the flow rate is m₁0.309 kg/s. The outlet of the condenser 4 is 34.73 ℃ saturated liquid, then the saturated liquid is pressurized to the evaporation pressure of 0.737MP by a working medium pump A5, the saturated liquid enters the evaporator 1 and is heated to the evaporation temperature of 77.28 ℃ (saturated gas), then the saturated liquid enters the expansion machine A2 for acting, the exhaust pressure of the expansion machine A2 is 0.21MP, the temperature is 45.43 ℃, and the exhaust gas enters the condenser 4 for condensation to complete the cycle.

2. And (3) circulation 2: working medium R227ea is adopted, and the flow rate is m₂1.911 kg/s. The outlet of the condenser 4 is 34.73 ℃ saturated liquid, then the saturated liquid is pressurized to the evaporation pressure of 2.685MP through a working medium pump B6, the saturated liquid enters the evaporator 1 and is heated to the evaporation temperature of 100.75 ℃ (saturated gas), then the saturated liquid enters the expansion machine B3 for doing work, the exhaust pressure of the expansion machine B3 is 0.606MP, the temperature is 37.3 ℃, and the exhaust gas enters the condenser 4 for condensation to complete the circulation.

As a comparison of the data in table 1, under the conditions of heat source, cold source and isentropic efficiency, the following results were obtained: compared with the conventional organic Rankine cycle (scheme four), the net output power increasing rates of the scheme I, the scheme II and the scheme III are respectively 43.24%, 30.20% and 16.03%, and in addition, the net output power of the scheme I is increased by 10.00% and 23.45% compared with the net output power of the scheme II and the scheme III.