WO2020116061A1

WO2020116061A1 - Rankine cycle device and control method therefor

Info

Publication number: WO2020116061A1
Application number: PCT/JP2019/042901
Authority: WO
Inventors: 倉本　哲英; 雅也本間
Original assignee: パナソニック株式会社
Priority date: 2018-12-07
Filing date: 2019-10-31
Publication date: 2020-06-11

Abstract

This Rankine cycle device comprises a sensor, a pump, an evaporator, an expansion machine, and a condenser, and also comprises a fluid circuit in which a working fluid flows and which includes a circulation circuit. In the circulation circuit, the pump, the evaporator, the expansion machine, and the condenser are arranged in this order. The sensor detects: (I) the pressure of the working fluid; (II) the temperature of the working fluid; or (III) the temperature of a cooling medium that is to exchange heat with the working fluid in the condenser. The sensor commences a first control if a value detected by the sensor is lower than a first threshold value. In the first control, the working fluid is circulated by the pump through the evaporator and/or a heater.

Description

Rankine cycle device and control method thereof

The present disclosure relates to a Rankine cycle device and a control method thereof.

Conventionally, various Rankine cycle devices have been studied. Patent Document 1 describes an example of a Rankine cycle device.

FIG. 8 shows a Rankine cycle device 100 according to Patent Document 1. In the Rankine cycle device 100, a pump 101, an evaporator 102, an expander 103, and a condenser 104 are connected in an annular shape. The Rankine cycle device 100 is provided with a bypass flow passage 110. The bypass passage 110 bypasses the expander 103. A valve 105 is provided in the bypass passage 110. The valve 105 regulates the flow rate of the working fluid in the bypass flow passage 110.

Patent No. 6179736

The present disclosure provides technology suitable for ensuring the reliability of Rankine cycle equipment.

This disclosure is
A sensor, a pump, an evaporator, an expander, and a condenser,
A fluid circuit in which a working fluid flows, the fluid circuit including a circulation circuit is provided,
In the circulation circuit, the pump, the evaporator, the expander, and the condenser are arranged in this order,
The sensor detects (I) the pressure of the working fluid, (II) the temperature of the working fluid, or (III) the temperature of a cooling medium to be heat exchanged with the working fluid in the condenser,
When the detection value of the sensor is lower than the first threshold value, the first control is started,
The first control provides a Rankine cycle device, which is a control in which the working fluid is circulated by the pump through the evaporator and/or the heater.

The technology according to the present disclosure is suitable for ensuring the reliability of Rankine cycle equipment.

FIG. 1 is a configuration diagram of the Rankine cycle device according to the first embodiment. FIG. 2 is a state diagram of a working fluid according to an example. FIG. 3 shows a flowchart showing the control in the first embodiment. FIG. 4 is a configuration diagram of the Rankine cycle device according to the second embodiment. FIG. 5 shows a flowchart showing the control in the second embodiment. FIG. 6 is a configuration diagram of the Rankine cycle device according to the third embodiment. FIG. 7 shows a flowchart showing the control in the fourth embodiment. FIG. 8: is a block diagram of the Rankine cycle apparatus which concerns on a prior art.

(Findings that form the basis of this disclosure)
When the pressure of the working fluid is a negative pressure, air, moisture, etc. in the atmosphere may be mixed in the flow path through which the working fluid flows. Suppressing such mixture contributes to ensuring the reliability of the Rankine cycle device.

(Outline of One Aspect According to the Present Disclosure)
A Rankine cycle device according to a first aspect of the present disclosure,
A sensor, a pump, an evaporator, an expander, and a condenser,
A fluid circuit in which a working fluid flows, the fluid circuit including a circulation circuit is provided,
In the circulation circuit, the pump, the evaporator, the expander, and the condenser are arranged in this order,
The sensor detects (I) the pressure of the working fluid, (II) the temperature of the working fluid, or (III) the temperature of a cooling medium to be heat exchanged with the working fluid in the condenser,
When the detection value of the sensor is lower than the first threshold value, the first control is started,
The first control is control in which the working fluid is circulated by the pump via the evaporator and/or heater.

The technology according to the first aspect is suitable for preventing the pressure of the working fluid from becoming a negative pressure. This contributes to ensuring the reliability of the Rankine cycle device.

In the second aspect of the present disclosure, for example, in the Rankine cycle device according to the first aspect,
(I) The sensor may detect the pressure of the working fluid, and the first threshold may be a pressure equal to or higher than atmospheric pressure,
(Ii) the sensor may detect the temperature of the working fluid, and the first threshold may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, or
(Iii) The sensor may detect a temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser, and the first threshold may be a temperature equal to or higher than a boiling point of the working fluid at atmospheric pressure. Good.

The second modes (i), (ii) and (iii) are suitable for preventing the pressure of the working fluid from becoming negative.

In the third aspect of the present disclosure, for example, in the Rankine cycle device according to the first aspect or the second aspect,
The sensor may detect the pressure of the working fluid in a portion of the circulation circuit downstream of the expander and upstream of the pump.

The third mode is suitable for preventing the pressure of the working fluid from becoming a negative pressure.

In the fourth aspect of the present disclosure, for example, in the Rankine cycle device according to any one of the first to third aspects,
The fluid circuit includes a portion downstream of the evaporator and upstream of the expander in the circulation circuit, and a portion downstream of the expander and upstream of the condenser in the circulation circuit. , May include a bypass circuit to connect,
In the first control, the working fluid may be circulated via the bypass circuit.

In the first control of the fourth aspect, the working fluid can circulate by bypassing the expander by the bypass circuit. With this configuration, the working fluid can smoothly circulate in the first control.

In the fifth aspect of the present disclosure, for example, in the Rankine cycle device according to the fourth aspect,
A valve may be provided in the bypass circuit,
In the first control, the opening degree of the valve of the bypass circuit may be set to 50% or more and 100% or less.

In the fifth mode, in the first control, the opening degree of the valve of the bypass circuit is set to 50% or more and 100% or less. When the opening is set in this way, the working fluid can be easily circulated smoothly in the first control.

In the sixth aspect of the present disclosure, for example, in the Rankine cycle device according to any one of the first to fifth aspects,
In the fluid circuit, the heater may be provided,
In the first control, the working fluid may be circulated through the evaporator by the pump,
When the detected value is less than a second threshold value and the elapsed time from the start of the first control is a threshold time or more, heat generation of the heater may be started.

According to the sixth aspect, even when the risk of the pressure of the working fluid becoming a negative pressure cannot be sufficiently suppressed by the first control, the risk can be suppressed by using the heater.

In the seventh aspect of the present disclosure, for example, the Rankine cycle device according to any one of the first to sixth aspects,
The drive of the pump may be stopped when the detected value is equal to or greater than the second threshold value.

According to the seventh aspect, unnecessary power consumption of the pump can be avoided.

In the eighth aspect of the present disclosure, for example, in the Rankine cycle device according to any one of the first to seventh aspects,
The boiling point of the working fluid at atmospheric pressure may be 0° C. or higher and 50° C. or lower.

When the boiling point of the working fluid is high as specified in the eighth mode, the pressure of the working fluid tends to be a negative pressure. Therefore, in this case, the technique of preventing the pressure of the working fluid from becoming a negative pressure is likely to exert its effect.

In the ninth aspect of the present disclosure, for example, the Rankine cycle device according to any one of the first to eighth aspects,
It may be provided with a generator that generates electric power by the rotation torque of the expander.

According to the ninth aspect, power can be generated by the expander and the generator.

A control method according to a tenth aspect of the present disclosure is
A method for controlling a Rankine cycle device in which a working fluid circulates through a pump, an evaporator, an expander, and a condenser in this order,
A sensor for detecting (I) the pressure of the working fluid, (II) the temperature of the working fluid, or (III) the temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser,
Starting a first circulation in which the working fluid in a heated state is circulated by the pump when the detection value of the sensor is lower than a first threshold value.

The technology according to the tenth aspect is suitable for preventing the pressure of the working fluid from becoming a negative pressure. This contributes to ensuring the reliability of the Rankine cycle device.

In the eleventh aspect of the present disclosure, for example, in the control method according to the tenth aspect,
(I) The sensor may detect the pressure of the working fluid, and the first threshold may be a pressure equal to or higher than atmospheric pressure,
(Ii) the sensor may detect the temperature of the working fluid, and the first threshold may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, or
(Iii) The sensor may detect a temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser, and the first threshold may be a temperature equal to or higher than a boiling point of the working fluid at atmospheric pressure. Good.

The eleventh modes (i), (ii) and (iii) are suitable for preventing the pressure of the working fluid from becoming negative.

In the twelfth aspect of the present disclosure, for example, in the control method according to the tenth aspect or the eleventh aspect,
In the Rankine cycle apparatus, a circulation circuit may be provided in which the pump, the evaporator, the expander, and the condenser are arranged in this order,
The sensor may detect the pressure of the working fluid in a portion of the circulation circuit downstream of the expander and upstream of the pump.

The twelfth aspect is suitable for preventing the pressure of the working fluid from becoming a negative pressure.

In the thirteenth aspect of the present disclosure, for example, in the control method according to any one of the tenth to twelfth aspects,
In the Rankine cycle device,
A circulation circuit in which the pump, the evaporator, the expander, and the condenser are arranged in this order,
A bypass connecting a portion of the circulation circuit downstream of the evaporator and upstream of the expander, and a portion of the circulation circuit downstream of the expander and upstream of the condenser. And a circuit may be provided,
In the first circulation, the working fluid may pass through the bypass circuit.

In the first circulation of the thirteenth aspect, the working fluid can circulate by bypassing the expander by the bypass circuit. With this configuration, the working fluid can smoothly circulate in the first circulation.

In the fourteenth aspect of the present disclosure, for example, in the control method according to the thirteenth aspect,
A valve may be provided in the bypass circuit,
In the first circulation, the opening degree of the valve of the bypass circuit may be set to 50% or more and 100% or less.

In the fourteenth aspect, in the first circulation, the valve opening degree of the bypass circuit is set to 50% or more and 100% or less. When the opening is set in this way, the working fluid can be easily circulated in the first circulation.

In the fifteenth aspect of the present disclosure, for example, in the control method according to any one of the tenth to fourteenth aspects,
In the first circulation, the working fluid may be heated by the evaporator and/or heater.

An evaporator and a heater are specific examples of devices that heat a working fluid.

In the sixteenth aspect of the present disclosure, for example, in the control method according to any one of the tenth to fifteenth aspects,
In the first circulation, the working fluid may be heated by the evaporator,
The control method may further include starting heating of the working fluid by a heater when the detected value is less than a second threshold value and an elapsed time after starting the first circulation is a threshold time or more. You may have it.

According to the sixteenth aspect, even if the risk that the pressure of the working fluid becomes a negative pressure cannot be sufficiently suppressed in the first circulation, the risk can be suppressed by using the heater.

In the seventeenth aspect of the present disclosure, for example, the control method according to any one of the tenth to sixteenth aspects,
The method may further include stopping driving of the pump when the detected value is equal to or greater than a second threshold value.

According to the seventeenth aspect, it is possible to avoid unnecessary power consumption of the pump.

In the eighteenth aspect of the present disclosure, for example, in the control method according to any one of the tenth to seventeenth aspects,
The boiling point of the working fluid at atmospheric pressure may be 0° C. or higher and 50° C. or lower.

If the boiling point of the working fluid is high as specified in the eighteenth aspect, the pressure of the working fluid tends to be a negative pressure. Therefore, in this case, the technique of preventing the pressure of the working fluid from becoming a negative pressure is likely to exert its effect.

A Rankine cycle device according to a nineteenth aspect of the present disclosure,
A sensor, a pump, an evaporator, an expander, and a condenser,
A fluid circuit in which a working fluid flows, the fluid circuit including a circulation circuit is provided,
In the circulation circuit, the pump, the evaporator, the expander, and the condenser are arranged in this order,
The sensor detects (I) the pressure of the working fluid, (II) the temperature of the working fluid, or (III) the temperature of a cooling medium to be heat exchanged with the working fluid in the condenser,
When the detection value of the sensor is lower than the first threshold value, the first control of circulating the heated working fluid by the pump is started.

A control method according to a twentieth aspect of the present disclosure is
A method for controlling a Rankine cycle device in which a working fluid circulates through a pump, an evaporator, an expander, and a condenser in this order,
A sensor for detecting (I) the pressure of the working fluid, (II) the temperature of the working fluid, or (III) the temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser,
Starting a first circulation when the detection value of the sensor is lower than a first threshold value;
The first circulation is a circulation of the working fluid by the pump through the evaporator and/or heater.

In the following embodiments, the term "circuit" may be used. As understood from the drawings and the like, the term “circuit” does not necessarily mean a closed path, but can be rephrased as “flow path” as appropriate.

Hereinafter, embodiments will be described with reference to the drawings. The present disclosure is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a configuration diagram of the Rankine cycle device 21 in the first embodiment.

The Rankine cycle device 21 is provided with a fluid circuit 14. In the fluid circuit 14, the working fluid flows. The fluid circuit 14 includes a circulation circuit 15 and a bypass circuit 16.

The type of working fluid is not particularly limited. The boiling point of the working fluid at atmospheric pressure is, for example, 0° C. or higher and 50° C. or lower. Here, the atmospheric pressure refers to one atmosphere. A specific example of the working fluid is a hydrofluoroolefin (HFO)-based working fluid. Here, the HFO-based working fluid refers to a working fluid containing HFO. The content of HFO in the working fluid is, for example, 50% by mass or more, and may be 80% by mass or more. More specifically, as the working fluid, a mixed fluid of HFO1336mzz(Z), HFO1336mzz(E), HFO1336mzz(Z), and HFO1336mzz(E) can be adopted. The working fluid containing HFO may be a mixed fluid or a single type of working fluid. A known fluid that does not contain HFO can be used as the working fluid.

The fluid circuit 14 is composed of a plurality of pipes. Hereinafter, the plurality of pipes may be collectively referred to as a pipe portion.

A Rankine cycle is configured in the Rankine cycle device 21. Specifically, the Rankine cycle device 21 constitutes an organic Rankine cycle (ORC).

The Rankine cycle device 21 includes a pump 1, an evaporator 2, an expander 3, and a condenser 4. In the circulation circuit 15, the pump 1, the evaporator 2, the expander 3, and the condenser 4 are arranged in this order. The pump 1, the evaporator 2, the expander 3, and the condenser 4 are connected using a plurality of pipes.

Rankine cycle device 21 includes reheater 6. In the reheater 6, heat is exchanged between the working fluids flowing in different parts of the circulation circuit 15.

The bypass circuit 16 includes a portion of the circulation circuit 15 downstream of the evaporator 2 and upstream of the expander 3, and a portion of the circulation circuit 15 downstream of the expander 3 and upstream of the condenser 4. , Are connected.

Rankine cycle device 21 includes valve 5. The valve 5 is provided in the bypass circuit 16. Hereinafter, the valve 5 may be referred to as the bypass valve 5. In the present embodiment, the bypass valve 5 is a flow rate adjusting valve. Here, the flow rate adjusting valve is a valve that can take not only 0% and 100% but also an opening degree larger than 0% and smaller than 100%.

The Rankine cycle device 21 includes a generator 18. The generator 18 is connected to the expander 3.

Hereinafter, operations of the pump 1, the evaporator 2, the expander 3, the condenser 4, the bypass valve 5, the reheater 6 and the generator 18 when the Rankine cycle device 21 is in the power generation operation will be described. Here, the power generation operation of the Rankine cycle device 21 refers to an operation in which the generator 18 generates power.

Pump 1 conveys a working fluid.

The evaporator 2 evaporates the working fluid. Specifically, the evaporator 2 recovers the heat of the heating medium and evaporates the working fluid. In the present embodiment, the heating medium is a heat source gas. Specifically, in the present embodiment, the heating medium is exhaust gas from a heat source such as factory equipment. The evaporator 2 is composed of, for example, a fin-and-tube heat exchanger.

The expander 3 expands the working fluid. Specifically, the expander 3 expands the working fluid that has become high temperature steam in the evaporator 2.

The condenser 4 condenses the working fluid expanded by the expander 3. Specifically, the condenser 4 condenses the working fluid by removing the heat of the working fluid by the cooling medium. In the present embodiment, the cooling medium is gas, specifically air in the atmosphere. However, the cooling medium may be a liquid such as water. In the present embodiment, the condenser 4 includes a fan 7. The condenser 4 uses the fan 7 to condense the working fluid. However, the fan 7 is not essential. The condenser 4 is composed of, for example, a fin-and-tube heat exchanger, a plate heat exchanger, or a double-tube heat exchanger. In one embodiment, the cooling medium is air, the condenser 4 is a fin and tube heat exchanger, and the condenser 4 comprises a fan 7. In another embodiment, the cooling medium is water, the condenser 4 is a plate heat exchanger or a double tube heat exchanger, and the condenser 4 is not equipped with a fan 7.

The bypass valve 5 adjusts the flow rate of the working fluid flowing through the expander 3 and the flow rate of the working fluid flowing through the bypass circuit 16. Specifically, these flow rates are adjusted by adjusting the opening degree of the bypass valve 5.

The reheater 6 includes a first portion 6a downstream of the pump 1 in the circulation circuit 15 and upstream of the evaporator 2, and downstream of the expander 3 in the circulation circuit 15 and upstream of the condenser 4. Second portion 6b of In the reheater 6, heat is exchanged between the working fluids flowing through these two parts. Due to this heat exchange, the temperature of the working fluid flowing through the first portion 6a rises and the temperature of the working fluid flowing through the second portion 6b falls.

The generator 18 generates power by the rotating torque of the expander 3.

Further, the Rankine cycle device 21 includes a first pressure sensor 8a, a second pressure sensor 8b, a first temperature sensor 9a, a second temperature sensor 9b, a third temperature sensor 9c, and a fourth temperature sensor 9d. including.

The first pressure sensor 8a detects the pressure of the working fluid in the first circuit 15a. The second pressure sensor 8b detects the pressure of the working fluid in the second circuit 15b. Here, the first circuit 15 a is a part of the circulation circuit 15 that is downstream of the pump 1 and upstream of the expander 3. The second circuit 15b is a part of the circulation circuit 15 downstream of the expander 3 and upstream of the pump 1.

In the present embodiment, the first pressure sensor 8a is provided in the first circuit 15a. Specifically, in the present embodiment, the first pressure sensor 8a is provided in a portion of the circulation circuit 15 downstream of the evaporator 2 and upstream of the expander 3. However, the first pressure sensor 8a may be provided in a portion of the circulation circuit 15 downstream of the pump 1 and upstream of the evaporator 2. The first pressure sensor 8a detects the pressure on the high pressure side of the Rankine cycle in the Rankine cycle device 21. The first pressure sensor 8a can be referred to as a high pressure sensor 8a.

The first pressure sensor 8a may be provided in a part of the bypass circuit 16 upstream of the bypass valve 5. The first pressure sensor 8a provided on the upstream side of the bypass valve 5 in the bypass circuit 16 can also detect the pressure of the working fluid in the first circuit 15a.

In the present embodiment, the second pressure sensor 8b is provided in the second circuit 15b. Specifically, in the present embodiment, the second pressure sensor 8b is provided in a portion of the circulation circuit 15 downstream of the condenser 4 and upstream of the pump 1. As described later, this portion corresponds to the third circuit 15c. However, the second pressure sensor 8b may be provided in a portion of the circulation circuit 15 downstream of the expander 3 and upstream of the condenser 4. The second pressure sensor 8b detects the pressure on the low pressure side of the Rankine cycle in the Rankine cycle device 21. The second pressure sensor 8b can be referred to as a low pressure sensor 8b.

The second pressure sensor 8b may be provided in a portion of the bypass circuit 16 downstream of the bypass valve 5. The second pressure sensor 8b provided on the downstream side of the bypass valve 5 in the bypass circuit 16 can also detect the pressure of the working fluid in the second circuit 15b.

The first temperature sensor 9a is provided in a portion of the circulation circuit 15 downstream of the evaporator 2 and upstream of the expander 3. The first temperature sensor 9a detects the temperature of the working fluid in this portion. The temperature of the working fluid at the inlet of the expander 3 can be grasped by the first temperature sensor 9a. The first temperature sensor 9a can be referred to as an expander inlet temperature sensor 9a.

The second temperature sensor 9b is provided in the third circuit 15c. Here, the third circuit 15c is a part of the circulation circuit 15 that is downstream of the condenser 4 and upstream of the pump 1. The second temperature sensor 9b detects the temperature of the working fluid in the third circuit 15c. The temperature of the working fluid at the outlet of the condenser 4 can be grasped by the second temperature sensor 9b. The second temperature sensor 9b can be referred to as a condenser outlet temperature sensor 9b.

The third temperature sensor 9c is installed in the cooling medium suction portion of the condenser 4. The third temperature sensor 9c detects the temperature of the cooling medium. In the present embodiment, the cooling medium is air in the atmosphere, and the third temperature sensor 9c detects the outside air temperature. In the present embodiment, the third temperature sensor 9c can be referred to as an outside air temperature sensor 9c.

The fourth temperature sensor 9d detects the temperature of the heating medium sucked into the evaporator 2. As described above, in the present embodiment, the heating medium is the heat source gas. In the present embodiment, the fourth temperature sensor 9d can be referred to as the heat source gas temperature sensor 9d.

Further, the Rankine cycle device 21 includes a control device 19. The control device 19 controls the components of the Rankine cycle device 21.

The pressure of the working fluid in the fluid circuit 14 will be described below.

When the Rankine cycle device 21 is in the power generation operation, the evaporator 2 recovers the heat of the heating medium, and the heat heats the working fluid. Then, the working fluid heated by the pump 1 flows through the fluid circuit 14. Therefore, the pressure of the working fluid in the fluid circuit 14 is maintained at a positive pressure. Here, the positive pressure is a pressure higher than the atmospheric pressure.

On the other hand, when the Rankine cycle device 21 is stopped and the pump 1 is stopped, the working fluid does not flow in the fluid circuit 14. In this case, even if the temperature of the heating medium supplied to the evaporator 2 is high, the pressure of the working fluid in the fluid circuit 14 is affected by the outside air temperature and becomes a pressure close to the saturation pressure of the working fluid at the outside air temperature. Sometimes.

In one specific example, the pump 1, the expander 3, and the condenser 4 are housed in one housing, and the housing and the evaporator 2 are separated by 5 m or more. When the separation distance is as large as that, the pressure of the working fluid in the fluid circuit 14 existing in the housing is more easily affected by the outside air temperature than the temperature of the heating medium, and is saturated with the outside air temperature of the working fluid. It tends to be close to pressure.

Consider using a working fluid with a high saturation temperature at atmospheric pressure. In this case, when the outside air temperature is lower than the boiling point of the working fluid, the working fluid may have a negative pressure. Here, the saturation temperature refers to a boiling point. Negative pressure refers to pressure below atmospheric pressure.

When the temperature of the working fluid is in a substantially equilibrium state in each part of the fluid circuit 14 and the outside air temperature is lower than the boiling point of the working fluid, a state in which the pressure of the working fluid becomes a negative pressure under the influence of the outside air temperature is shown in FIG. This will be described with reference to 2. Note that, typically, immediately after the pump 1 is stopped, there is a temperature difference in the working fluid in each part of the fluid circuit 14. After a lapse of a sufficient time from the stop of the pump 1, the temperature of the working fluid can reach a substantially equilibrium state in each part of the fluid circuit 14. FIG. 2 is a state diagram of the working fluid. In addition, in FIG. 2, the melting curve and the sublimation curve are omitted.

In state A, the working fluid is in a gas-liquid two-phase state. The pressure of the working fluid is positive pressure. The temperature of the working fluid is above its boiling point at atmospheric pressure.

When the outside air temperature changes, the temperature of the working fluid also changes under the influence of the outside air temperature. In particular, the temperature of the working fluid inside the condenser 4 becomes substantially the same as the outside air temperature when in a thermal equilibrium state. For example, if the outside air temperature decreases, the temperature of the working fluid also decreases. As the temperature of the working fluid decreases, the pressure of the working fluid decreases along the vapor pressure curve. Specifically, in this example, the state of the working fluid changes from state A to state C via state B.

In state B, the working fluid is in a gas-liquid two-phase state. The pressure of the working fluid is atmospheric pressure. The temperature of the working fluid is the boiling point at atmospheric pressure.

In state C, the working fluid is in a gas-liquid two-phase state. The temperature of the working fluid is the outside air temperature. The pressure of the working fluid is a negative pressure.

In FIG. 2, the pressure of the working fluid is negative even in the state between the state B and the state C in the vapor pressure curve. As understood from this, even if the temperature of the working fluid does not fall to the outside air temperature, the pressure of the working fluid can be a negative pressure.

Note that FIG. 2 is a diagram for explanation and should not be used for limiting interpretation of the embodiment. For example, the curves of the working fluid phase diagram are not limited to the shape of FIG. In addition, the pressure of the working fluid that is not in the gas-liquid two-phase state may become negative.

Specifically, consider the case where HFO1336mzz(Z) is used as the working fluid. The boiling point of HFO1336mzz(Z) is 33°C. Therefore, in this case, if the pump 1 is stopped when the outside air temperature is less than 33° C., the pressure of the working fluid may become a negative pressure.

Also, consider the case where HFO1336mzz(E) is used as the working fluid. The boiling point of HFO1336mzz(E) is 8°C. Therefore, in this case, if the pump 1 is stopped when the outside air temperature is lower than 8° C., the pressure of the working fluid may become a negative pressure.

In the piping section, there may be gaps at the welding point, screw connection section, etc. This gap may be caused by poor welding, poor construction such as insufficient tightening torque during screw connection, or loosening of the screw connection portion due to vibration during operation, deterioration over time, and the like. If the pressure of the working fluid is positive, and if a gap occurs in the piping, the working fluid leaks from the inside of the piping to the outside. In this case, the Rankine cycle device 21 can be returned to the state before the leakage of the working fluid by repairing the piping so as to eliminate the gap and refilling the working fluid. Further, if the working fluid leaks from the piping portion, specific symptoms that indicate a malfunction of the Rankine cycle device appear, such as the working fluid cannot be circulated by the pump 1 due to lack of working fluid. Therefore, the leakage of the working fluid from the piping portion is easily recognized. Therefore, the repair of the piping portion and the refilling of the working fluid can be performed relatively early from the occurrence of the leakage of the working fluid.

On the other hand, if the pressure of the working fluid is negative, and if a gap is created in the piping, air, moisture, etc. in the atmosphere may enter the piping. When such mixing occurs, the working fluid or the lubricating oil may be hydrolyzed. If the lubricating oil is hydrolyzed, the lubricity of the sliding parts of the components such as the pump 1 and the expander 3 may be deteriorated, which may cause the device failure. It is not always easy to immediately recognize the entry of air, moisture, etc. into the piping section. For this reason, when it is noticed that a defect has occurred, the degree of the defect may be large. Therefore, at the time when the trouble is discovered, the equipment failure has progressed to a serious state, and it is difficult to return to the original state even if the gap is repaired and the working fluid is refilled.

In order to avoid the above-mentioned inconvenience caused by the pressure of the working fluid becoming a negative pressure when a gap is created in the piping part, it is conceivable to eliminate the occurrence of the gap itself in the piping part. However, it is not always easy to completely eliminate the generation of gaps.

Specifically, as described above, the fluid circuit 14 may include a welding part, a screw connection part, and the like. It is not easy to completely eliminate the generation of gaps at welded parts, screw connection parts and the like.

By adopting an installation method in which the Rankine cycle device 21 is completed in a factory equipped with manufacturing devices and the finished product is moved to the installation place, that is, by eliminating the welding work at the installation site of the Rankine cycle device 21, It is possible to reduce the probability of forming a gap at the welded portion. However, such an installation method is not always adopted. When the heat source that supplies the heat source gas to the evaporator 2 is equipment fixed to the land, the Rankine cycle device 21 may be installed at the site where the equipment is located. When welding is performed on site, it is not always easy to completely prevent the formation of a gap at the welding point.

Also, even if there is no problem when the Rankine cycle device 21 is installed, a gap may occur in the piping portion due to vibration during operation of the Rankine cycle device 21. It is not always easy to completely avoid the generation of gaps during operation.

Therefore, in order to suppress the occurrence of the above-mentioned inconvenience caused by the pressure of the working fluid becoming a negative pressure when a gap occurs in the pipe portion, the present inventors have It was examined to suppress the generation of negative pressure.

According to the study by the present inventors, when the pressure of the working fluid is low, the negative pressure can be suppressed by driving the pump 1 in the stopped state. Specifically, by driving the pump 1, the working fluid can be heated in the evaporator 2 while flowing the working fluid in the fluid circuit 14, and the pressure of the working fluid can be maintained at a positive pressure. The present inventors have made further studies and arrived at the control described below.

Hereinafter, the control of the Rankine cycle device 21 will be described with reference to the flowchart of FIG. In the following description, the bypass valve 5 is assumed to be closed before starting the flowchart.

In step S1, the control device 19 determines whether the pump 1 is stopped and the pressure detected by the second pressure sensor 8b is less than the first threshold pressure Pth1. When the pump 1 is stopped and the pressure detected by the second pressure sensor 8b is less than the first threshold pressure Pth1, the process proceeds to step S2. When the pump 1 is driven and/or when the pressure detected by the second pressure sensor 8b is equal to or higher than the first threshold pressure Pth1, step S1 is executed again. “When the pump 1 is driven and/or when the pressure detected by the second pressure sensor 8b is equal to or higher than the first threshold pressure Pth1”, the condition that the pump 1 is driven and the detection by the second pressure sensor 8b are performed. This means that at least one of the conditions that the pressure is equal to or higher than the first threshold pressure Pth1 is satisfied.

The first threshold pressure Pth1 may be a pressure equal to or higher than atmospheric pressure. The first threshold pressure Pth1 may be a pressure equal to or lower than the detection pressure of the second pressure sensor 8b during the power generation operation, specifically, a pressure lower than the detection pressure. In this context, the "detection pressure of the second pressure sensor 8b during the power generation operation" refers to the detection value of the pressure in the steady state rather than the transient state. The first threshold pressure Pth1 is, for example, 0.01 MPa or more and 0.2 MPa or less. In one specific example, the first threshold pressure Pth1 is 0.05 MPa.

In this example, the elapsed time that satisfies the condition of step S1 is counted starting from the timing when the process first proceeds from step S1 to S2. Hereinafter, this elapsed time may be referred to as a standby time.

In step S2, the control device 19 determines whether the waiting time is equal to or longer than the threshold waiting time Twth. When the waiting time is equal to or longer than the threshold waiting time Twth, the process proceeds to step S3. If the waiting time is less than the threshold waiting time Twth, the process proceeds to step S1.

The threshold wait time Twth is, for example, 0.1 minute or more and 5 minutes or less. A specific example of the threshold waiting time Twth is 1 minute.

In step S3, the control device 19 increases the opening degree of the bypass valve 5. Further, in step S3, the control device 19 starts driving the pump 1. It progresses to step S4 after step S3.

After execution of step S3, the working fluid circulates through the pump 1, the evaporator 2, the bypass valve 5 and the condenser 4 in this order. In the evaporator 2, the heat of the heating medium supplied to the evaporator 2 is recovered, and the heat heats the working fluid. This heating increases the pressure of the working fluid.

As mentioned above, the heating medium supplied to the evaporator 2 may be a heat source gas. In one specific example, the heat source gas is exhaust gas from a facility having a large heat capacity, such as a drying furnace or a blast furnace. In this case, even if the operation of the equipment is stopped, the temperature of the exhaust gas does not immediately drop to near the outside air temperature. For this reason, the evaporator 2 and its ambient temperature are kept higher than the outside air temperature for a while after the operation is stopped. Therefore, by driving the pump 1, the evaporator 2 heats the working fluid. Then, the pressure can be increased.

In step S3, the bypass valve 5 may be fully opened. If the opening degree of the bypass valve 5 is not zero before execution of step S3, for example, if the opening degree is 50% or more, the opening degree of the bypass valve 5 does not necessarily have to be increased in step S3. .. In some cases, the opening degree of the bypass valve 5 may be maintained at zero before and after step S3.

In step S3, the rotation speed of the pump 1 is set to, for example, 100 rpm or more and 5000 rpm or less. In one specific example, in step S3, the rotation speed of the pump 1 is set to 1000 rpm. However, since the operating rotational speed range varies depending on the pump specifications, the rotational speed to be set is not limited to the above example.

The operation in step S3 can be considered as control for preventing negative pressure. The control of step S3 can be referred to as first negative pressure prevention control.

The second pressure sensor 8b is provided in the second circuit 15b. The pressure of the working fluid in the second circuit 15b tends to be a negative pressure. Therefore, if the negative pressure prevention control is performed based on the detection value of the second pressure sensor 8b, it is easy to obtain the effect of suppressing the negative pressure of the working fluid. Specifically, the second pressure sensor 8b is provided in the third circuit 15c.

In step S4, the control device 19 determines whether the pressure detected by the second pressure sensor 8b is equal to or higher than the second threshold pressure Pth2. When the pressure detected by the second pressure sensor 8b is equal to or higher than the second threshold pressure Pth2, the process proceeds to step S5. When the pressure detected by the second pressure sensor 8b is less than the second threshold pressure Pth2, step S4 is executed again.

The second threshold pressure Pth2 may be a pressure equal to or higher than the atmospheric pressure, specifically, a pressure higher than the atmospheric pressure. The second threshold pressure Pth2 may be a pressure equal to or lower than the detection pressure of the second pressure sensor 8b during the power generation operation, specifically, a pressure lower than the detection pressure. In the present embodiment, the second threshold pressure Pth2 is higher than the first threshold pressure Pth1. The second threshold pressure Pth2 is, for example, 0.01 MPa or more and 0.2 MPa or less. In one specific example, the second threshold pressure Pth2 is 0.15 MPa.

In step S5, the control device 19 stops the pump 1. As a result, the negative pressure prevention control in step S3 ends.

The control may be restarted after the control based on the flowchart of FIG. 3 is completed. For example, the control may be restarted after a predetermined period has elapsed since the control based on the flowchart of FIG. 3 was completed. This also applies to the control of the embodiment described later.

The following describes some other embodiments. In the following, elements common to the embodiments already described and the embodiments to be described later are designated by the same reference numerals, and the description thereof may be omitted. The same applies to the flowchart. The description of each embodiment can be applied to each other as long as there is no technical contradiction. The respective embodiments may be combined with each other as long as there is no technical conflict.

(Embodiment 2)
FIG. 4 shows a configuration diagram of the Rankine cycle device 22 in the second embodiment.

Rankine cycle device 22 includes heater 10. The heater 10 is, for example, a resistance heater.

The heater 10 is provided in the fluid circuit 14. The heater 10 heats the working fluid flowing through the fluid circuit 14. In the example of FIG. 4, the heater 10 is provided in the circulation circuit 15.

Specifically, the heater 10 is provided in a portion of the circulation circuit 15 downstream of the pump 1 and upstream of the condenser 4. In other words, the heater 10 is provided in the circulation circuit 15 at a portion other than the portion downstream of the condenser 4 and upstream of the pump 1. With this configuration, the working fluid flowing into the pump 1 due to the heating by the heater 10 is unlikely to be in a gas-liquid two-phase state, and a problem in the transfer of the working fluid by the pump 1 is less likely to occur.

More specifically, the heater 10 is provided in a portion of the circulation circuit 15 downstream of the pump 1 and upstream of the evaporator 2. More specifically, the heater 10 is provided in a portion of the circulation circuit 15 downstream of the pump 1 and upstream of the reheater 6.

In one example, the heater 10 has a linear shape. The heater 10 is in close contact with the pipe in the circulation circuit 15. The length direction of the pipe and the length direction of the heater 10 match.

In another example, the heater 10 has a strip shape. The heater 10 is wound around the outer wall of the pipe in the circulation circuit 15.

The control device 19 controls the heater 10. In the present embodiment, the control device 19 controls energization of the heater 10. When electricity is supplied to the heater 10, the heater 10 generates heat. When the heater 10 is not energized, the heater 10 does not generate heat.

The control of the Rankine cycle device 22 will be described below with reference to the flowchart of FIG.

In the second embodiment, the elapsed time from the start of driving the pump 1 in step S3 is counted. Hereinafter, this elapsed time is referred to as a pump operating time.

In the second embodiment, when the pressure detected by the second pressure sensor 8b is less than the second threshold pressure Pth2 in step S4, the process proceeds to step S6.

In step S6, the control device 19 determines whether or not the pump operation time is equal to or longer than the threshold time Tth. If the pump operating time is equal to or longer than the threshold time Tth, the process proceeds to step S7. If the pump operating time is less than the threshold time Tth, the process proceeds to step S4.

The threshold time Tth is, for example, 1 minute or more and 10 minutes or less. A specific example of the threshold time Tth is 5 minutes.

In step S7, the controller 19 starts energizing the heater 10. When the energization of the heater 10 is started in step S7, the heating of the working fluid by the heater 10 is started. It progresses to step S8 after step S7.

Consider a case where the heat source is factory equipment and the factory equipment has been down for a long time. In that case, since the factory equipment is cooled by the ambient air, the difference between the temperature of the heat source gas and the outside air temperature may be small. If this difference is small, even if the pump 1 is driven in step 3, the working fluid cannot be sufficiently heated in the evaporator 2, and the pressure of the working fluid may not rise sufficiently. In this respect, in the present embodiment, the working fluid is heated by the heater 10 in step S7. Thereby, the pressure of the working fluid can be sufficiently increased.

The operation in step S7 can be considered as control for preventing negative pressure. The control of step S7 can be referred to as second negative pressure prevention control.

In step S8, the control device 19 determines whether the pressure detected by the second pressure sensor 8b is equal to or higher than the second threshold pressure Pth2. When the pressure detected by the second pressure sensor 8b is equal to or higher than the second threshold pressure Pth2, the process proceeds to step S9. When the pressure detected by the second pressure sensor 8b is less than the second threshold pressure Pth2, step S8 is executed again.

In step S9, the controller 19 terminates energization of the heater 10. The heating of the working fluid by the heater 10 is ended by the end of the energization of the heater 10 in step S9. As a result, the second negative pressure prevention control of step S7 ends.

In step S9, the control device 19 may stop energizing the heater 10 and stop the pump 1.

(Embodiment 3)
FIG. 6 shows a configuration diagram of the Rankine cycle device 23 in the third embodiment.

In the Rankine cycle device 23, the fluid circuit 14 includes a shortcut circuit 17.

Rankine cycle device 23 includes valve 11. The valve 11 is provided in the shortcut circuit 17. Hereinafter, the valve 11 will be referred to as a shortcut valve 11. In the present embodiment, the shortcut valve 11 is a flow rate adjusting valve.

The control based on the flowchart of FIG. 5 can be applied to the third embodiment. In the third embodiment, the control device 19 increases the opening degree of the shortcut valve 11 when step S7 of FIG. 5 is executed. As a result, the working fluid circulates through the pump 1, the shortcut valve 11 and the condenser 4 in this order. During this circulation, the working fluid also passes through the heater 10. The working fluid is heated by the heater 10. As a result, the pressure of the working fluid can be increased.

Since the circulation path of the working fluid passing through the pump 1, the shortcut valve 11 and the condenser 4 in this order is shorter than the circulation path of the working fluid passing through the pump 1, the evaporator 2, the bypass valve 5 and the condenser 4 in this order, The working fluid can be circulated quickly by the pump 1. Such a short circulation path may make it easier for the heater 10 to raise the pressure of the working fluid.

The shortcut valve 11 may be fully opened when step S7 of FIG. 5 is executed. When the opening degree of the shortcut valve 11 is not zero before the execution of step S7, for example, when the opening degree is 50% or more, the opening degree of the shortcut valve 11 is not necessarily increased when step S7 is executed. You don't have to. In some cases, the opening degree of the shortcut valve 11 may be maintained at zero before and after step S7.

(Embodiment 4)
Hereinafter, the control of the fourth embodiment will be described with reference to FIG. 7. The control of the fourth embodiment can be executed using the Rankine cycle device 22 of the second embodiment, for example.

As shown in FIG. 7, in the fourth embodiment, if the waiting time is equal to or longer than the threshold waiting time Twth in step S2, the process proceeds to step S10.

In step S10, the control device 19 increases the opening degree of the bypass valve 5. In step S10, the controller 19 starts energizing the heater 10. When the heater 10 is energized in step S10, heating of the working fluid by the heater 10 is started. Further, in step S10, the control device 19 starts driving the pump 1. It progresses to step S4 after step S10.

After execution of step S10, the working fluid circulates through the pump 1, the heater 10, the evaporator 2, the bypass valve 5 and the condenser 4 in this order. The working fluid is heated in the heater 10. The working fluid can also be heated in the evaporator 2.

In step S10, the bypass valve 5 may be fully opened. If the opening degree of the bypass valve 5 is not zero before execution of step S10, for example, if the opening degree is 50% or more, it is not necessary to increase the opening degree of the bypass valve 5 in step S10. In some cases, the opening degree of the bypass valve 5 may be maintained at zero before and after step S10.

In some cases, the control device 19 may energize the heater 10 before step S10. For example, when the standby time reaches the first threshold time, the controller 19 starts energizing the heater 10, and when the standby time reaches the threshold standby time Twt, the controller 19 starts driving the pump 1. May be. Here, the first threshold time is shorter than the threshold waiting time Twth.

Alternatively, the pump 1 may be driven by the control device 19 before step S10. For example, when the standby time reaches the second threshold time, the controller 19 starts driving the pump 1, and when the standby time reaches the threshold standby time Twt, the controller 19 starts energizing the heater 10. May be. Here, the second threshold time is shorter than the threshold waiting time Twth.

In step S10, the rotation speed of the pump 1 is set to, for example, 100 rpm or more and 5000 rpm or less. In one specific example, in step S10, the rotation speed of the pump 1 is set to 1000 rpm. However, since the operating rotational speed range varies depending on the pump specifications, the rotational speed to be set is not limited to the above example.

The operation in step S10 can be considered as control for preventing negative pressure. The control in step S10 can be referred to as third negative pressure prevention control.

In the fourth embodiment, if the pressure detected by the second pressure sensor 8b is equal to or higher than the second threshold pressure Pth2 in step S4, the process proceeds to step S11.

In step S11, the controller 19 terminates energization of the heater 10. In step S11, the control device 19 stops the pump 1. With step S11, the negative pressure prevention control of step S10 ends.

If the heat source is factory equipment and the factory equipment has been stopped for a long time, there may be substantially no difference between the temperature of the heat source gas and the outside air temperature. In this case, even if the pump 1 is driven, the working fluid is not substantially heated in the evaporator 2. Therefore, the evaporator 2 does not substantially contribute to the pressure increase of the working fluid.

In this respect, according to the fourth embodiment, even if the evaporator 2 does not contribute to the temperature rise and the pressure rise of the working fluid, the heater 10 can raise the temperature and the pressure of the working fluid.

(Embodiment 5)
It is also possible to perform the control of the fourth embodiment by using the Rankine cycle 23 of the third embodiment. A mode of performing the control of the fourth embodiment by using the Rankine cycle 23 of the third embodiment is referred to as a fifth embodiment.

In the fifth embodiment, when step S10 of FIG. 7 is executed, the opening degree of the shortcut valve 11 may be increased or may be fully opened. If the opening degree of the shortcut valve 11 is not zero before execution of step S10, for example, if the opening degree is 50% or more, the opening degree of the shortcut valve 11 should not be increased when step S10 is executed. You can In some cases, the opening degree of the shortcut valve 11 may be maintained at zero before and after step S10.

In the fifth embodiment, after step S10 of FIG. 7, a mode in which the opening degree of the shortcut valve 11 is non-zero and the opening degree of the bypass valve 5 is zero can also be adopted. In this way, after the execution of step S10, the working fluid circulates through the pump 1, the heater 10, the shortcut valve 11 and the condenser 4 in this order. The working fluid is heated in the heater 10. This heating increases the pressure of the working fluid.

(Technology applicable to Embodiments 1 to 5)
In the above example, in step S1 of the first to fifth embodiments, it is determined whether the pressure detected by the second pressure sensor 8b is less than the first threshold pressure Pth1. However, instead of making this determination, it may be determined whether the temperature detected by the second temperature sensor 9b is lower than the first threshold temperature. Instead of making this determination, it may be determined whether the temperature detected by the third temperature sensor 9c is lower than the second threshold temperature. This is because the temperature detected by the second temperature sensor 9b and the temperature detected by the third temperature sensor 9c can be effective indices for preventing the pressure of the working fluid from becoming negative.

The pressure detected by the second pressure sensor 8b used in step S1 of the first to fifth embodiments is the pressure detected on the low pressure side of the Rankine cycle. In step S1, the detected pressure on the high pressure side of the Rankine cycle may be used. Specifically, in step S1, it may be determined whether the pressure detected by the first pressure sensor 8a is less than the third threshold pressure. This is because the detected pressure on the high pressure side can also be an effective index for preventing the pressure of the working fluid from becoming negative. When the pump 1 is stopped, the low-pressure side pressure and the high-pressure side pressure may be close to each other.

Also, the detected temperature on the high pressure side of the Rankine cycle may be used in step S1. Specifically, in step S1, it may be determined whether or not the temperature detected by the first temperature sensor 9a is lower than the third threshold temperature. This is because the detected temperature on the high pressure side can also be an effective index for preventing the pressure of the working fluid from becoming a negative pressure. When the pump 1 is stopped, the low-pressure side temperature and the high-pressure side temperature may be close to each other.

Specifically, in step S1 according to a modification, the control device 19 determines whether the pump 1 is stopped and the temperature detected by the second temperature sensor 9b is lower than the first threshold temperature. When the pump 1 is stopped and the temperature detected by the second temperature sensor 9b is lower than the first threshold temperature, the process proceeds to step S2. When the pump 1 is driven and/or when the temperature detected by the second temperature sensor 9b is equal to or higher than the first threshold temperature, step S1 is executed again. The first threshold temperature may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, specifically, a temperature higher than the boiling point. The first threshold temperature may be a temperature equal to or lower than the detection temperature of the second temperature sensor 9b during the power generation operation, specifically, a temperature lower than the detection temperature. The first threshold temperature is, for example, a value obtained by adding a margin to the boiling point of the working fluid at atmospheric pressure. The margin is, for example, 0° C. or more and 5° C. or less.

In step S1 according to the modified example, the control device 19 determines whether the pump 1 is stopped and the temperature detected by the third temperature sensor 9c is lower than the second threshold temperature. When the pump 1 is stopped and the temperature detected by the third temperature sensor 9c is lower than the second threshold temperature, the process proceeds to step S2. When the pump 1 is driven and/or when the temperature detected by the third temperature sensor 9c is equal to or higher than the second threshold temperature, step S1 is executed again. The second threshold temperature may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, specifically, a temperature higher than the boiling point. The second threshold temperature is, for example, a value obtained by adding a margin to the boiling point of the working fluid at atmospheric pressure. The margin is, for example, 0° C. or more and 5° C. or less.

In step S1 according to the modification, the control device 19 determines whether the pump 1 is stopped and the pressure detected by the first pressure sensor 8a is less than the third threshold pressure. When the pump 1 is stopped and the pressure detected by the first pressure sensor 8a is less than the third threshold pressure, the process proceeds to step S2. When the pump 1 is driven and/or when the pressure detected by the first pressure sensor 8a is equal to or higher than the third threshold pressure, step S1 is executed again. The third threshold pressure may be a pressure equal to or higher than atmospheric pressure, specifically a pressure higher than atmospheric pressure. The third threshold pressure may be a pressure equal to or lower than the detection pressure of the first pressure sensor 8a during the power generation operation, specifically, a pressure lower than the detection pressure. The same value as the first threshold pressure can be adopted as the third threshold pressure.

In step S1 according to a modification, the control device 19 determines whether the pump 1 is stopped and the temperature detected by the first temperature sensor 9a is lower than the third threshold temperature. When the pump 1 is stopped and the temperature detected by the first temperature sensor 9a is lower than the third threshold temperature, the process proceeds to step S2. When the pump 1 is driven and/or when the temperature detected by the first temperature sensor 9a is equal to or higher than the third threshold temperature, step S1 is executed again. The third threshold temperature may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, specifically, a temperature higher than the boiling point. The third threshold temperature may be a temperature equal to or lower than the detection temperature of the first temperature sensor 9a during the power generation operation, specifically, a temperature lower than the detection temperature. The third threshold temperature is, for example, a value obtained by adding a margin to the boiling point of the working fluid at atmospheric pressure. The margin is, for example, a value in the range of 0° C. or higher and 5° C. or lower.

In the above example, in step S4 of the first to fifth embodiments, it is determined whether the pressure detected by the second pressure sensor 8b is equal to or higher than the second threshold pressure Pth2. However, instead of making this determination, it may be determined whether the temperature detected by the second temperature sensor 9b is equal to or higher than the fourth threshold temperature. Instead of making this determination, it may be determined whether the temperature detected by the first temperature sensor 9a is equal to or higher than the fifth threshold temperature.

Specifically, in step S4 according to the modified example, the control device 19 determines whether the temperature detected by the second temperature sensor 9b is equal to or higher than the fourth threshold temperature. When the temperature detected by the second temperature sensor 9b is equal to or higher than the fourth threshold temperature, the process proceeds to step S5 or step S11. When the temperature detected by the second temperature sensor 9b is lower than the fourth threshold temperature, step S4 is executed again or the process proceeds to step S6. The fourth threshold temperature may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, specifically, a temperature higher than the boiling point. The fourth threshold temperature may be a temperature equal to or lower than the detection temperature of the second temperature sensor 9b during the power generation operation, specifically, a temperature lower than the detection temperature. The fourth threshold temperature may be higher than the first threshold temperature. The fourth threshold temperature is, for example, a value obtained by adding a margin to the boiling point of the working fluid at atmospheric pressure. The margin is, for example, a value in the range of 0° C. or higher and 5° C. or lower.

In step S4 according to the modification, the control device 19 determines whether the temperature detected by the first temperature sensor 9a is equal to or higher than the fifth threshold temperature. When the temperature detected by the first temperature sensor 9a is equal to or higher than the fifth threshold temperature, the process proceeds to step S5 or step S11. When the temperature detected by the first temperature sensor 9a is lower than the fifth threshold temperature, step S4 is executed again or the process proceeds to step S6. The fifth threshold temperature may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, specifically, a temperature higher than the boiling point. The fifth threshold temperature may be a temperature equal to or lower than the detection temperature of the first temperature sensor 9a during the power generation operation, specifically, a temperature lower than the detection temperature. The fifth threshold temperature may be higher than the second threshold temperature. The fifth threshold temperature is, for example, a value obtained by adding a margin to the boiling point of the working fluid at atmospheric pressure. The margin is, for example, a value in the range of 0° C. or higher and 5° C. or lower.

In the example described above, in step S6, the control device 19 determines whether the pump operation time is equal to or longer than the threshold time Tth. It is also possible to apply the judgment based on the pump operating time to step S4 of the first, fourth and fifth embodiments.

Specifically, in step S4 according to the modified example of the first embodiment, the control device 19 determines whether or not the pump operation time is equal to or longer than the threshold time Tth. If the pump operating time is equal to or longer than the threshold time Tth, the process proceeds to step S5. When the pump operating time is less than the threshold time Tth, step S4 is executed again.

In step S4 according to the modification of the fourth and fifth embodiments, the control device 19 determines whether or not the pump operation time is equal to or longer than the threshold time Tth. If the pump operating time is equal to or longer than the threshold time Tth, the process proceeds to step S11. When the pump operating time is less than the threshold time Tth, step S4 is executed again.

In the above example, in step S8 of the second and third embodiments, it is determined whether the pressure detected by the second pressure sensor 8b is equal to or higher than the second threshold pressure Pth2. However, instead of making this determination, it may be determined whether the temperature detected by the second temperature sensor 9b is equal to or higher than the fourth threshold temperature. Instead of making this determination, it may be determined whether the temperature detected by the first temperature sensor 9a is equal to or higher than the fifth threshold temperature.

Specifically, in step S8 according to the modified example, the control device 19 determines whether the temperature detected by the second temperature sensor 9b is equal to or higher than the fourth threshold temperature. When the temperature detected by the second temperature sensor 9b is equal to or higher than the fourth threshold temperature, the process proceeds to step S9. When the temperature detected by the second temperature sensor 9b is lower than the fourth threshold temperature, step S8 is executed again.

In step S8 according to the modification, the control device 19 determines whether the temperature detected by the first temperature sensor 9a is equal to or higher than the fifth threshold temperature. When the temperature detected by the first temperature sensor 9a is equal to or higher than the fifth threshold temperature, the process proceeds to step S9. When the temperature detected by the first temperature sensor 9a is lower than the fifth threshold temperature, step S8 is executed again.

In the above-described example, in step S1 of Embodiments 1 to 3, the control device 19 determines whether the pump 1 is stopped and the pressure detected by the second pressure sensor 8b is less than the first threshold pressure Pth1. to decide. However, in step S1, the control device 19 determines that the pump 1 is stopped, the pressure detected by the second pressure sensor 8b is less than the first threshold pressure Pth1, and the temperature detected by the fourth temperature sensor 9d is the third. You may judge whether it is higher than the detection temperature of the temperature sensor 9c. By determining whether or not the temperature detected by the fourth temperature sensor 9d is higher than the temperature detected by the third temperature sensor 9c, it is possible to confirm whether or not the working fluid can be heated by the evaporator 2 when step S3 is executed. it can. A temperature sensor for detecting the temperature of the evaporator 2 (specifically, the temperature of the structural portion forming the evaporator 2) is provided, and the temperature detected by the temperature sensor is used instead of the temperature detected by the fourth temperature sensor 9d. Good. The same modification can be applied to the fourth and fifth embodiments.

Specifically, in step S1 according to the modified example, in addition to the conditions of step S1 of the first to third embodiments, the control device 19 determines that the temperature detected by the fourth temperature sensor 9d is the temperature detected by the third temperature sensor 9c. Is higher than. When the conditions of step S1 of Embodiments 1 to 3 are satisfied and the temperature detected by the fourth temperature sensor 9d is higher than the temperature detected by the third temperature sensor 9c, the process proceeds to step S2. When the condition of step S1 of the first to third embodiments is not satisfied and/or the temperature detected by the fourth temperature sensor 9d is equal to or lower than the temperature detected by the third temperature sensor 9c, step S1 is executed again. To be done. The same modification can be applied to the fourth and fifth embodiments. Furthermore, the same modification can be applied to the above-described modified example.

In the above example, the bypass valve 5 and the shortcut valve 11 are variable flow rate type valves. However, the bypass valve 5 and the shortcut valve 11 may be opening/closing valves such as solenoid valves. The on-off valve refers to a valve whose opening degree is set to either of 0% and 100%.

An electric ball valve can be adopted as the bypass valve 5 and/or the shortcut valve 11. The electric ball valve has a small change in the flow passage cross-sectional area between the valve portion and the piping before and after the valve. Therefore, according to the electric ball valve, the flow path resistance when circulating the working fluid can be reduced.

During the power generation operation of the Rankine cycle device, the working fluid circulates through the expander 3. This enables power generation by the expander 3 and the generator 18.

On the other hand, it is not essential for the working fluid to circulate through the expander 3 when the Rankine cycle device is not generating power. In one embodiment, after step S3 of FIGS. 3 and 5 and step S10 of FIG. 7, the working fluid circulates through bypass circuit 16 in addition to pump 1 and evaporator 2. This allows the working flow to flow smoothly. After steps S3 and S10, the opening degree of the bypass valve 5 may be 100% or less than 100%.

The opening degree of the bypass valve 5 after step S3 and step S10 being 100% is advantageous from the viewpoint of smoothing the flow of the working fluid through the pump 1, the evaporator 2 and the bypass circuit 16. In this case, the working fluid is easily heated by the evaporator 2.

On the other hand, the fact that the opening degree of the bypass valve 5 after step S3 and step S10 is less than 100% means that the temperature of the working fluid flowing into the condenser 4 is lowered as compared with the case where the opening degree is 100%. Is advantageous. In this case, the working fluid is likely to be condensed in the condenser 4, the gas-liquid two-phase working fluid is unlikely to flow into the pump 1, and the pump 1 is unlikely to cause a problem.

After step S3 and step S10, it is possible to suppress the inflow of the working fluid into the expander 3 by controlling the rotation speed of the expander 3. In the above example, the rotary shaft of the expander 3 and the rotary shaft of the generator 18 are connected. Therefore, control of the rotation speed of the expander 3 can be realized by controlling the rotation speed of the generator 18. The control of the rotation speed of the generator 18 can be realized by the control device 19, for example. In one specific example, a PWM (Pulse Width Modulation) inverter (not shown) is connected to the generator 18. Then, the control device 19 PWM-controls the rotation speed of the generator 18 using the PWM inverter. During the power generation operation, it is also possible to control the amount of power generation by rotating the generator 18 by PWM control.

As described above, the bypass circuit 16 is connected to the portion of the circulation circuit 15 downstream of the evaporator 2 and upstream of the expander 3. A valve may be provided in a portion of the circulation circuit 15 that is downstream of the connection and upstream of the expander 3. By doing so, the flow of the working fluid into the expander 3 can be prevented by closing the valve. For example, in steps S3 and S10, the valve can be closed.

The fan 7 of the condenser 4 may be stopped while the first negative pressure prevention control, the second negative pressure prevention control, and the third negative pressure prevention control are being performed. As a result, the working fluid is less likely to be affected by the outside air temperature, and the pressure of the working fluid is more likely to increase or less likely to decrease.

The fan 7 may be operated while performing the first negative pressure prevention control, the second negative pressure prevention control, and the third negative pressure prevention control. This makes it difficult for the gas-liquid two-phase working fluid to flow into the pump 1. For example, the fan 7 can be operated when the temperature of the working fluid flowing into the condenser 4 is high and the ability to condense the working fluid should be improved.

It is also possible to control the fan 7 using a sensor. In one example, the fan 7 is controlled based on the detection value of the second pressure sensor 8b and the detection value of the second temperature sensor 9b. In one specific example, the degree of supercooling of the working fluid is calculated based on the detection value of the second pressure sensor 8b and the detection value of the second temperature sensor 9b, and the fan 7 is controlled based on the degree of supercooling. Controlling the fan 7 is an expression that includes both a form in which the rotation speed of the fan 7 is controlled and a form in which whether the fan 7 is driven or stopped is controlled.

(Technology related to the above description)
As can be understood from the above description, the Rankine cycle devices 21 to 23 according to the above description start the first control when the detection value of the sensor is lower than the first threshold value. The first control is control in which the working fluid is circulated by the pump 1 via the evaporator 2 and/or the heater 10. Such a Rankine cycle device is suitable for preventing the pressure of the working fluid from becoming a negative pressure. This contributes to ensuring the reliability of the Rankine cycle device. Specifically, the first control is control in which the working fluid is circulated by the pump 1 via the evaporator 2 and/or the heater 10 in a heat generation state. In one specific example, the first control is control in which the working fluid is circulated by the pump 1 via the evaporator 2 in a state in which the working fluid can be heated and/or the heater 10 in a heating state.

Here, starting the first control means that the driving of the pump 1 is started before the heat generation of the heater 10 is started, the driving of the pump 1 is started simultaneously with the heat generation of the heater 10, and the first control is started. It is a concept including a form in which the driving is started after the heat generation of the heater 10 is started. In a typical example, the start of the first control and the start of driving the pump 1 are simultaneous.

Also, the expression “circulating the working fluid by the pump 1 through the evaporator 2 and/or the heater 10” does not mean that the presence of the heater 10 is essential. As can be understood from the first embodiment, the first control can be executed without the heater 10.

In one specific example, the Rankine cycle devices 21 to 23 according to the above description start the driving of the pump 1 when the pump 1 is stopped and the first condition is satisfied, so that the

Rankine cycle devices

21 and 23 evaporate. The first control of circulating the working fluid via the device 2 is started. Here, the first condition is a condition that the detection value of the sensor is lower than the first threshold value.

The control method according to the above description includes a step of detecting with a sensor. Further, the control method includes a step of starting a first circulation in which the working fluid in a heated state is circulated by the pump 1 when the detection value of the sensor is lower than the first threshold value.

Here, the expression "starting the first circulation in which the working fluid in a heated state is circulated by the pump 1 is started" will be explained. In this expression, the driving start of the pump 1 is before the heating of the working fluid, the driving start of the pump 1 is the same as the heating of the working fluid, and the driving start of the pump 1 is the heating of the working fluid. It is a concept that includes a form after the start. In a typical example, the start of the first circulation and the start of driving the pump 1 are simultaneous.

Specifically, it can be said that the control method includes a step of heating the working fluid.

In the first circulation, the working fluid may be heated by, for example, the evaporator 2 and/or the heater 10. The step of heating the working fluid may be performed by the evaporator 2 and/or the heater 10, for example.

The above sensor may be a sensor that detects the pressure of the working fluid. In this case, the first condition is a condition that the pressure of the working fluid is lower than the first threshold value. In this case, the first threshold may be a pressure equal to or higher than atmospheric pressure, specifically a pressure higher than atmospheric pressure. Specifically, in this case, the second pressure sensor 8b can be used as the sensor, and the above-described first threshold pressure Pth1 can be used as the first threshold. In this case, the first pressure sensor 8a can be used as the sensor and the third threshold pressure can be used as the first threshold.

The above sensor may be a sensor that detects the temperature of the working fluid. In this case, the first condition is a condition that the temperature of the working fluid is lower than the first threshold value. In this case, the first threshold may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, specifically, a temperature higher than the boiling point. Specifically, in this case, the second temperature sensor 9b can be used as the sensor, and the above-mentioned first threshold temperature can be used as the first threshold. Further, in this case, the first temperature sensor 9a can be used as the sensor and the above-mentioned third threshold temperature can be used as the first threshold.

The above sensor may be a sensor that detects the temperature of the cooling medium that is to be heat-exchanged with the working fluid in the condenser 4. In this case, the first condition is a condition that the temperature of the cooling medium is lower than the first threshold value. In this case, the first threshold may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, specifically, a temperature higher than the boiling point. Specifically, in this case, the third temperature sensor 9c can be used as the sensor, and the above-mentioned second threshold temperature can be used as the first threshold. The “temperature of the cooling medium to be heat-exchanged with the working fluid in the condenser 4” refers to the temperature of the cooling medium before being heat-exchanged with the working fluid in the condenser 4.

In one specific example, the sensor detects the pressure of the working fluid in the portion of the circulation circuit 15 downstream of the expander 3 and upstream of the pump 1 (that is, the second circuit 15b). The pressure of the working fluid in this portion tends to be a negative pressure. Therefore, the detection of the pressure of the working fluid in this portion by the sensor is suitable for preventing the pressure of the working fluid from becoming a negative pressure.

In a more specific example, the sensor detects the pressure of the working fluid in the portion of the circulation circuit 15 downstream of the condenser 4 and upstream of the pump 1 (that is, the third circuit 15c).

In the first control, the working fluid may be circulated via the bypass circuit 16. In this way, the working fluid can be circulated by bypassing the expander 3 by the bypass circuit 16. In this way, the working fluid can circulate smoothly.

In one specific example, in the first control, the working fluid is circulated via the pump 1, the evaporator 2, and the bypass circuit 16. With this configuration, in the first control, the working fluid can smoothly circulate via the pump 1 and the evaporator 2.

Similarly, in the first circulation, the working fluid may pass through the bypass circuit 16. Specifically, in the first circulation, the working fluid may pass through the pump 1, the evaporator 2, and the bypass circuit 16.

Although not particularly limited, the opening degree of the valve 5 of the bypass circuit 16 can be set to 50% or more and 100% or less in the first control. When the opening is set in this manner, the working fluid can be easily circulated through the pump 1 and the evaporator 2 smoothly in the first control. In the first control, the opening degree of the valve 5 of the bypass circuit 16 may be set to 75% or more and 100% or less.

Similarly, the first circulation may be performed with the opening degree of the valve 5 of the bypass circuit 16 set to 50% or more and 100% or less. The first circulation may be performed with the opening degree of the valve 5 of the bypass circuit 16 set to 75% or more and 100% or less.

In one example, in the first control, the working fluid is circulated through the evaporator 2 by the pump 1. When the detected value of the sensor is less than the second threshold value and the elapsed time from the start of the first control is the threshold time or more, the heater 10 starts to generate heat. With this configuration, even if the first control cannot sufficiently suppress the risk that the pressure of the working fluid becomes negative, the heater 10 can be used to suppress the risk. In the typical example, the second threshold is higher than the first threshold.

In one specific example, when the second condition is not satisfied and the pump operation time is equal to or longer than the threshold time, the second control in which the working fluid is circulated through the pump 1 and the heater 10 while causing the heater 10 to generate heat. To start. Here, the second condition is a condition that the detected value is equal to or more than the second threshold value. The second threshold is a higher threshold than the first threshold. The pump operation time is an elapsed time after the driving of the pump is started by the first control. With this configuration, even when the risk of the working fluid pressure becoming a negative pressure cannot be sufficiently suppressed by the first control, the risk can be suppressed by the second control using the heater 10.

Similarly, in one example, the working fluid is heated by the evaporator 2 in the first circulation. The control method includes the step of starting the heating of the working fluid by the heater 10 when the detected value of the sensor is less than the second threshold value and the elapsed time from the start of the first circulation is the threshold time or more. In one specific example, when the second condition is not satisfied and the pump operating time is equal to or longer than the threshold time, the control method causes the heater 10 to generate heat and circulates the working fluid through the pump 1 and the heater 10. And a step of starting the second circulation. In the typical example, the second threshold is higher than the first threshold.

The Rankine cycle device may stop the driving of the pump 1 when the detected value is equal to or higher than the second threshold value. In this way, unnecessary power consumption of the pump can be avoided.

Similarly, the control method may further include a step of stopping the driving of the pump 1 when the detection value of the sensor is equal to or higher than the second threshold value.

As described above, the sensor may be a sensor that detects the pressure of the working fluid. In this case, the second condition is a condition that the pressure of the working fluid is equal to or higher than the second threshold value. In this case, the second threshold may be a pressure equal to or higher than atmospheric pressure, specifically a pressure higher than atmospheric pressure. Specifically, the second pressure sensor 8b can be used as the sensor, and the second threshold pressure Pth2 can be used as the second threshold. When the sensor is a sensor that detects the pressure of the working fluid, the first threshold may be referred to as a first threshold pressure and the second threshold may be referred to as a second threshold pressure. In a typical example, the second threshold pressure is higher than the first threshold pressure.

As described above, the sensor may be a sensor that detects the temperature of the working fluid. In this case, the second condition is a condition that the temperature of the working fluid is equal to or higher than the second threshold value. In this case, the second threshold may be a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, specifically, a temperature higher than the boiling point. Specifically, in this case, the second temperature sensor 9b can be used as the sensor, and the above-mentioned fourth threshold temperature can be used as the second threshold. In this case, the first temperature sensor 9a can be used as the sensor and the fifth threshold temperature can be used as the second threshold.

In one specific example, in the second control, the working fluid is circulated via the pump 1, the heater 10, and the bypass circuit 16. Although not particularly limited, in the second control, the opening degree of the valve 5 of the bypass circuit 16 can be set to, for example, 50% or more and 100% or less. In the second control, the opening degree of the valve 5 of the bypass circuit 16 may be set to 75% or more and 100% or less.

Similarly, in one specific example, in the second circulation, the working fluid is circulated through the pump 1, the heater 10, and the bypass circuit 16. Although not particularly limited, the opening degree of the valve 5 of the bypass circuit 16 can be set to, for example, 50% or more and 100% or less in the second circulation. In the second circulation, the opening degree of the valve 5 of the bypass circuit 16 may be set to 75% or more and 100% or less.

The fluid circuit 14 may include the shortcut circuit 17 described above. In the second control, the working fluid may be circulated through the pump 1, the heater 10, and the shortcut circuit 17. Although not particularly limited, the opening degree of the valve 11 of the shortcut circuit 17 can be set to, for example, 50% or more and 100% or less in the second control. In the second control, the opening degree of the valve 11 of the shortcut circuit 17 may be set to 75% or more and 100% or less.

Similarly, in the second circulation, the working fluid may be circulated via the pump 1, the heater 10 and the shortcut circuit 17. Although not particularly limited, in the second circulation, the opening degree of the valve 11 of the shortcut circuit 17 can be set to, for example, 50% or more and 100% or less. In the second circulation, the opening degree of the valve 11 of the shortcut circuit 17 may be set to 75% or more and 100% or less.

In one specific example, the pump 1, the expander 3, and the condenser 4 are housed in one housing. Since the pump 1, the expander 3, and the condenser 4 are housed in the housing, it is difficult for the pump 1, the expander 3, and the condenser 4 to exchange heat with the outside air, and the temperature is less likely to drop due to the outside air. Therefore, the housing can exert an effect of suppressing the working fluid from becoming negative pressure.

The Rankine cycle apparatus according to the present disclosure can be applied to a direct contact Rankine cycle in which an evaporator is in direct contact with a heat source gas. Further, the Rankine cycle apparatus according to the present disclosure can be applied to a binary Rankine cycle having a cycle of a water refrigerant or the like between a heat source gas and an evaporator.

1 Pump 2 Evaporator 3 Expander 4 Condenser 5 Bypass valve 6 Reheater 7 Fan 8a 1st pressure sensor 8b 2nd pressure sensor 9a 1st temperature sensor 9b 2nd temperature sensor 9c 3rd temperature sensor 9d 4th temperature sensor 10 Heater 11 Shortcut valve 14 Fluid circuit 15 Circulation circuit 16 Bypass circuit 17 Shortcut circuit 18 Generator 19

Control device

21,22,23 Rankine cycle device

Claims

A sensor, a pump, an evaporator, an expander, and a condenser,
A fluid circuit in which a working fluid flows, the fluid circuit including a circulation circuit is provided,
In the circulation circuit, the pump, the evaporator, the expander, and the condenser are arranged in this order,
The sensor detects (I) the pressure of the working fluid, (II) the temperature of the working fluid, or (III) the temperature of a cooling medium to be heat exchanged with the working fluid in the condenser,
When the detection value of the sensor is lower than the first threshold value, the first control is started,
The Rankine cycle device, wherein the first control is a control in which the working fluid is circulated by the pump through the evaporator and/or the heater.
(I) The sensor detects the pressure of the working fluid, and the first threshold is a pressure equal to or higher than atmospheric pressure.
(Ii) the sensor detects the temperature of the working fluid, and the first threshold is a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, or
(Iii) the sensor detects a temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser, and the first threshold value is a temperature equal to or higher than a boiling point of the working fluid at atmospheric pressure,
The Rankine cycle apparatus according to claim 1.
The sensor detects the pressure of the working fluid in a portion of the circulation circuit downstream of the expander and upstream of the pump,
The Rankine cycle apparatus according to claim 1.
The fluid circuit includes a portion downstream of the evaporator and upstream of the expander in the circulation circuit, and a portion downstream of the expander and upstream of the condenser in the circulation circuit. Including a bypass circuit connecting
In the first control, circulating the working fluid through the bypass circuit,
The Rankine cycle apparatus according to any one of claims 1 to 3.
A valve is provided in the bypass circuit,
In the first control, the opening degree of the valve of the bypass circuit is set to 50% or more and 100% or less.
The Rankine cycle apparatus according to claim 4.
In the fluid circuit, the heater is provided,
In the first control, the working fluid is circulated through the evaporator by the pump,
When the detected value is less than a second threshold value and the elapsed time from the start of the first control is a threshold time or more, heat generation of the heater is started,
The Rankine cycle apparatus according to any one of claims 1 to 5.
Stopping the drive of the pump when the detected value is equal to or greater than a second threshold value,
The Rankine cycle device according to any one of claims 1 to 6.
The boiling point of the working fluid at atmospheric pressure is 0° C. or higher and 50° C. or lower,
The Rankine cycle apparatus according to any one of claims 1 to 7.
A generator for generating power by the rotating torque of the expander,
The Rankine cycle device according to any one of claims 1 to 8.
A method for controlling a Rankine cycle device in which a working fluid circulates through a pump, an evaporator, an expander, and a condenser in this order,
A sensor for detecting (I) the pressure of the working fluid, (II) the temperature of the working fluid, or (III) the temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser,
Starting a first circulation in which the working fluid in a heated state is circulated by the pump when the detection value of the sensor is lower than a first threshold value;
Control method.
(I) The sensor detects the pressure of the working fluid, and the first threshold is a pressure equal to or higher than atmospheric pressure.
(Ii) the sensor detects the temperature of the working fluid, and the first threshold is a temperature equal to or higher than the boiling point of the working fluid at atmospheric pressure, or
(Iii) the sensor detects a temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser, and the first threshold value is a temperature equal to or higher than a boiling point of the working fluid at atmospheric pressure,
The control method according to claim 10.
In the Rankine cycle apparatus, a circulation circuit is provided in which the pump, the evaporator, the expander, and the condenser are arranged in this order,
The sensor detects the pressure of the working fluid in a portion of the circulation circuit downstream of the expander and upstream of the pump,
The control method according to claim 10.
In the Rankine cycle device,
A circulation circuit in which the pump, the evaporator, the expander, and the condenser are arranged in this order,
A bypass connecting a portion of the circulation circuit downstream of the evaporator and upstream of the expander, and a portion of the circulation circuit downstream of the expander and upstream of the condenser. A circuit is provided,
In the first circulation, the working fluid passes through the bypass circuit,
The control method according to any one of claims 10 to 12.
A valve is provided in the bypass circuit,
In the first circulation, the opening degree of the valve of the bypass circuit is set to 50% or more and 100% or less,
The control method according to claim 13.
Heating the working fluid by the evaporator and/or heater in the first circulation;
The control method according to any one of claims 10 to 14.
Heating the working fluid by the evaporator in the first circulation;
The control method may further include starting heating of the working fluid by a heater when the detected value is less than a second threshold value and an elapsed time after starting the first circulation is a threshold time or more. Prepare,
The control method according to any one of claims 10 to 15.
The control method further includes stopping driving of the pump when the detected value is equal to or greater than a second threshold value.
The control method according to any one of claims 10 to 16.
The boiling point of the working fluid at atmospheric pressure is 0° C. or higher and 50° C. or lower,
The control method according to any one of claims 10 to 17.