JP6163145B2 - Thermal energy recovery device - Google Patents

Description

  The present invention relates to a thermal energy recovery device.

  2. Description of the Related Art Conventionally, a thermal energy recovery device that recovers power from exhaust heat of various facilities such as factories is known. For example, Patent Document 1 discloses an evaporator that evaporates a working medium, an oil separation tank that collects oil that flows out of the evaporator together with the working medium, a screw expander that expands the working medium that flows out of the oil separation tank, Disclosed is a power generator including a generator connected to a screw expander, a condenser for condensing a working medium flowing out from the expander, and a pump for sending the working medium flowing out from the condenser to an evaporator. Yes. A heating medium for heating the working medium from an external heat source is supplied to the evaporator. Patent Document 2 also discloses a similar power generator.

JP 2011-122568 A JP 2006-283675 A

  In the power generator as described in Patent Document 1 or 2, the upstream side of the pump at the start-up time (warm-up operation) or when the flow rate or temperature of the heating medium supplied to the evaporator decreases. There is a concern that the amount of the liquid working medium in the pump is reduced, the pump operation becomes unstable, and cavitation occurs in the pump. Specifically, when the apparatus is activated, the temperature of the flow path on the downstream side of the evaporator and the temperature of the oil recovery device is lower than that during steady operation of the apparatus. And condensed in the oil recovery unit and collected in the oil recovery unit as a liquid working medium. Therefore, the amount of the liquid working medium on the upstream side of the pump is reduced. In addition, when the flow rate or temperature of the heating medium supplied from the heat source to the evaporator decreases, the liquid working medium does not fully evaporate in the evaporator and flows out of the evaporator in a gas-liquid two-phase state. Since the liquid of the working medium is accumulated in the oil recovery unit, the amount of the liquid working medium on the upstream side of the pump is reduced. For this reason, at the time of start-up (during warm-up operation) or when the flow rate or temperature of the heating medium supplied to the evaporator is reduced, the operation of the pump may become unstable due to the gaseous working medium flowing into the pump. Cavitation occurs in the pump, which can damage the pump.

  An object of the present invention is to provide a thermal energy recovery device capable of suppressing the unstable operation of a pump and the occurrence of cavitation in the pump at the time of startup or when the flow rate or temperature of a heating medium supplied to an evaporator is lowered. It is.

  As means for solving the above-mentioned problems, the present invention collects an evaporator that evaporates the working medium by heating the working medium with an externally supplied heating medium, and oil that flows out of the evaporator together with the working medium. An oil recovering device, an expander that expands the working medium flowing out from the oil recovering device, a power recovery device connected to the expander, a condenser that condenses the working medium flowing out from the expander, and A pump for sending the working medium condensed in the condenser to the evaporator; a circulation path for connecting the evaporator, the oil recovery unit, the expander, the condenser and the pump in this order; and the oil recovery unit A return flow path for returning the liquid in the circulation flow path to the downstream side of the condenser and the upstream side of the pump, and the amount of the working medium in the condenser or the circulation flow path The condenser Control for performing a return operation to return the liquid in the oil recovery unit through the return flow path when a liquid volume reduction condition indicating that the volume of the working medium between the pump and the pump has decreased below a reference amount is established And a thermal energy recovery device comprising the unit.

  In the present invention, when the amount of the working medium on the upstream side of the pump (in the condenser or the portion between the condenser and the pump in the circulation flow path) decreases below the reference amount, in other words, the oil Since the return operation is performed when the liquid working medium is accumulated in the collector, that is, the liquid (oil and working medium) in the oil collector passes through the return flow path and is downstream of the condenser in the circulation flow path. And since it returns to the site | part upstream of a pump, the liquid quantity in the upstream of a pump increases early. Therefore, the unstable operation of the pump and the occurrence of cavitation in the pump at the time of start-up (during warm-up operation) or when the flow rate or temperature of the heating medium supplied to the evaporator is reduced are suppressed. Moreover, since the liquid in the oil recovery unit is returned not to the upstream side of the condenser but to the downstream side of the condenser, cooling of the liquid in the condenser is avoided, so that the liquid is returned to the upstream side of the condenser. Compared to the case where the working medium contained in the liquid is condensed after flowing out of the evaporator, or the working medium contained in the liquid is prevented from flowing out from the evaporator in a gas-liquid two-phase state. .

  In this case, the control unit determines the height of the liquid level of the working medium in the condenser or the height of the liquid level of the working medium between the condenser and the pump in the circulation channel. A liquid level sensor that can be detected, and a return control unit that performs the return operation by determining that the liquid amount reduction condition is satisfied when a detection value of the liquid level sensor is equal to or lower than a reference height. May be.

  In this way, it is possible to determine whether or not the liquid amount reduction condition is satisfied with a simple configuration in which a liquid level sensor is provided between the condenser and the pump in the condenser or in the circulation flow path. It becomes.

  Alternatively, the control unit includes a liquid level sensor capable of detecting the height of the liquid level in the oil recovery unit, and the liquid amount reduction condition when the detected value of the liquid level sensor exceeds an upper limit height. And a return control unit that performs the return operation by determining that it has been established.

  Even in this case, the unstable operation of the pump and the occurrence of cavitation in the pump at the time of start-up or when the flow rate or temperature of the heating medium supplied to the evaporator is reduced are suppressed. Specifically, at the time of start-up or when the flow rate or temperature of the heating medium is lowered, at least a part of the working medium that has flowed out of the evaporator accumulates in the oil recovery unit in a liquid state. Then, while the liquid level in the oil recovery unit becomes higher, the amount of liquid on the upstream side of the pump decreases, so it is determined whether or not the liquid amount reduction condition is satisfied based on the height of the liquid level of the oil recovery unit can do. Therefore, by performing the return operation when the liquid level of the oil recovery device reaches or exceeds the upper limit height, it is possible to suppress the unstable operation of the pump and the occurrence of cavitation in the pump.

  Alternatively, the control unit includes a temperature sensor capable of detecting the temperature of the liquid in the oil recovery unit or the temperature of the oil recovery unit, and the liquid amount decrease when a detection value of the temperature sensor becomes a lower limit temperature or less. A return control unit that determines that the condition is satisfied and performs the return operation.

  Even in this case, unstable operation of the pump and occurrence of cavitation in the pump are suppressed. Specifically, when the temperature of the liquid in the oil recovery unit or the temperature of the oil recovery unit is lower than the vaporization temperature of the working medium, for example, at least a part of the working medium flowing out of the evaporator is condensed in the oil collecting unit. In the oil collector. As a result, the liquid level in the oil recovery unit increases while the liquid amount on the upstream side of the pump decreases, so that the liquid amount reduction condition is established based on the temperature of the liquid in the oil recovery unit or the temperature of the oil recovery unit. It can be determined whether or not. Therefore, by performing a return operation when the temperature of the liquid in the oil recovery device or the temperature of the oil recovery device is lower than the lower limit temperature, the unstable operation of the pump and the occurrence of cavitation in the pump are suppressed. Can do.

  Alternatively, the control unit performs the return operation until the temperature of the part of the circulation channel between the oil recovery unit and the expander or the temperature of the working medium flowing through the part becomes a set temperature or higher. Also good.

  In this way, during the warm-up operation in which the liquid working medium tends to accumulate in the oil recovery unit (the portion between the evaporator and the oil recovery unit in the circulation channel, the oil in the oil recovery unit and the circulation channel) The operation is continued until the temperature of the part between the collector and the expander reaches the normal operation temperature), so that the unstable operation of the pump during start-up and cavitation in the pump Generation can be effectively suppressed.

  Further, in the present invention, an oil supply passage for supplying the oil in the oil recovery unit to the expander is further provided, and the specific gravity of the oil is smaller than the specific gravity of the liquid working medium, and the upstream of the oil supply passage. The side end is preferably connected to the oil collector at a position above the upstream end of the return flow path.

  In this way, since a liquid containing a large amount of oil having a relatively small specific gravity is supplied from the oil collector to the expander, the occurrence of oil film breakage in the expander is suppressed. Specifically, since the specific gravity of oil is smaller than that of the liquid working medium, the upstream end of the oil supply passage is at the same height as or lower than the upstream end of the return passage. The ratio of oil to the liquid supplied to the expander through the oil supply passage is more connected to the oil recovery device at a position higher than the upstream end of the return passage compared to the case where it is connected to the recovery device. Increases, thereby increasing the viscosity of the liquid. Therefore, the occurrence of oil film breakage in the expander is suppressed.

  In this case, an auxiliary oil supply passage for supplying the oil in the oil recovery unit to the expander is further provided, and an upstream end of the auxiliary oil supply passage is an upstream end of the oil supply passage. It is preferable that it is connected to the oil recovery unit at a position below the part.

  In this way, even when a liquid working medium is accumulated in the oil recovery unit, the liquid level in the oil recovery unit is refueled while supplying a liquid containing a large amount of oil to the expander through the oil supply passage. Even when lower than the upstream end of the flow path, the oil can be reliably supplied to the expander through the auxiliary oil supply flow path.

  Furthermore, in this case, the upstream end of the auxiliary oil supply channel is connected to the oil recovery device at the same height as or lower than the upstream end of the return channel. It is preferable.

  In this way, the oil is always supplied to the expander while the liquid in the oil recovery unit is returned through the return channel.

  Further, in the present invention, switching between a first mode in which the oil supply channel is opened and the auxiliary oil supply channel is blocked and a second mode in which the oil supply channel is blocked and the auxiliary oil channel is opened. The control unit further includes a possible switching valve, and the control unit sets the switching valve as the first mode when the liquid level in the oil recovery unit is located above the upstream end of the oil supply passage. On the other hand, when the liquid level in the oil recovery unit is located below the upstream end of the oil supply passage, it is preferable to further include a switching valve control unit that uses the switching valve as the second mode.

  In this way, when the liquid level in the oil recovery device is higher than the end on the upstream side of the oil supply passage, only the liquid containing a relatively large amount of oil can be supplied to the expander through the oil supply passage. In addition, when the liquid level in the oil recovery unit is lower than the upstream end of the oil supply passage, the oil supply passage is blocked, so that, for example, a gaseous working medium flows into the expander through the oil supply passage. It is suppressed.

  As described above, according to the present invention, thermal energy recovery that can suppress unstable operation of the pump and occurrence of cavitation in the pump at the time of start-up or when the flow rate or temperature of the heating medium supplied to the evaporator is reduced. An apparatus can be provided.

It is a figure which shows the outline of a structure of the thermal energy recovery apparatus of 1st Embodiment of this invention. It is a flowchart which shows the control content of the return control part of the thermal energy recovery apparatus of FIG. It is a figure which shows the modification of the thermal energy recovery apparatus of FIG. It is a figure which shows the modification of the thermal energy recovery apparatus of FIG. It is a figure which shows the modification of the thermal energy recovery apparatus of FIG. It is a figure which shows the modification of the thermal energy recovery apparatus of FIG. It is a figure which shows the modification of the thermal energy recovery apparatus of FIG. It is a figure which shows the outline of a structure of the thermal energy recovery apparatus of 2nd Embodiment of this invention. It is a figure which shows the outline of a structure of the thermal energy recovery apparatus of 3rd Embodiment of this invention.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
A thermal energy recovery device according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the thermal energy recovery apparatus includes an evaporator 10, an oil recovery unit 12, an expander 14, a power recovery unit 16, a condenser 18, a receiver 20, a pump 22, and a circulation. A flow path 30, a return flow path 32, and a control unit 40 are provided.

  The circulation flow path 30 connects the evaporator 10, the oil recovery device 12, the expander 14, the condenser 18, the receiver 20, and the pump 22 in this order in series.

  The evaporator 10 evaporates the working medium by exchanging heat between the heating medium supplied from the outside and the liquid working medium. Examples of the heating medium supplied to the evaporator 10 include hot water and high-temperature gas discharged from a factory or the like. Further, R245fa is used as the working medium.

  The oil recovery unit 12 is provided at a downstream side of the evaporator 10 in the circulation flow path 30. The oil recovery unit 12 recovers oil that has flowed out of the evaporator 10 together with the working medium. The oil recovered by the oil recovery unit 12 is supplied to the expander 14 through an oil supply passage 13 that connects the oil recovery unit 12 and the expander 14. In the present embodiment, the upstream end of the oil supply passage 13 is connected to the side of the oil collector 12. The specific gravity of this oil is smaller than the specific gravity of the liquid working medium.

  The expander 14 is provided in the downstream portion of the oil collector 12 in the circulation flow path 30. In the present embodiment, a positive displacement screw expander having a rotor that is rotationally driven by the expansion energy of the gaseous working medium flowing out from the oil recovery unit 12 is used as the expander 14. Specifically, the expander 14 has a pair of male and female screw rotors.

  The power recovery machine 16 is connected to the expander 14. In the present embodiment, a power generator is used as the power recovery machine 16. The power recovery machine 16 has a rotating shaft connected to one of a pair of screw rotors of the expander 14. The power recovery machine 16 generates electric power when the rotating shaft rotates with the rotation of the screw rotor. In addition to the generator, a compressor or the like may be used as the power recovery machine 16.

  The condenser 18 is provided in a portion of the circulation channel 30 on the downstream side of the expander 14. The condenser 18 condenses (liquefies) the working medium flowing out from the expander 14 by cooling with a cooling medium (cooling water or the like) supplied from the outside.

  The receiver 20 is provided at a site on the downstream side of the condenser 18 in the circulation flow path 30. The receiver 20 stores the liquid working medium that has flowed out of the condenser 18.

  The pump 22 is provided at a site downstream of the receiver 20 in the circulation channel 30 (a site between the receiver 20 and the evaporator 10). The pump 22 pressurizes the liquid working medium to a predetermined pressure and sends it to the evaporator 10. As the pump 22, a centrifugal pump having an impeller as a rotor, a gear pump having a rotor composed of a pair of gears, or the like is used.

  The return flow path 32 is a flow path for returning the liquid in the oil recovery unit 12 to a site downstream of the condenser 18 and upstream of the pump 22 in the circulation flow path 30. In the present embodiment, the upstream end of the return channel 32 is connected to the bottom of the oil recovery device 12, and the downstream end of the return channel 32 is connected to the receiver 20. The upstream end of the return channel 32 may be connected to the oil supply channel 13. Further, the downstream end of the return channel 32 may be connected to a portion of the circulation channel 30 between the condenser 18 and the receiver 20.

  A return valve V <b> 1 is provided in the return channel 32. By opening the return valve V1, the liquid in the oil collector 12 flows into the receiver 20.

  The control unit 40 passes through the return flow path 32 when a liquid volume reduction condition is established that indicates that the liquid volume of the working medium between the condenser 18 and the pump 22 in the circulation flow path 30 has decreased below the reference volume. A return operation for returning the liquid in the oil collector 12 is performed. Specifically, the control unit 40 performs control to open the return valve V1 when the liquid amount reduction condition is satisfied. In the present embodiment, the control unit 40 includes a liquid level sensor 41 and a return control unit 42.

  The liquid level sensor 41 is provided in the receiver 20 located between the condenser 18 and the pump 22 in the circulation flow path 30.

  The return control unit 42 determines that the liquid amount reduction condition is satisfied when the detection value L1 of the liquid level sensor 41 is equal to or less than the reference height L0, and performs the return operation (operation to open the return valve V1). . Further, the return control unit 42 closes the return valve V1 when the detected value L1 becomes larger than the reference height L0.

  In the present embodiment, the control unit 40 further includes a liquid level sensor 43 that can detect the height of the liquid level of the oil recovery unit 12. The return control unit 42 closes the return valve V1 when the detection value L2 of the liquid level sensor 43 becomes equal to or lower than the lower limit height Lα. The lower limit height Lα is set at the position of the upstream end of the oil supply passage 13.

  Next, specific control contents of the return control unit 42 will be described with reference to FIG.

  First, the return control unit 42 determines whether or not the detection value L1 of the liquid level sensor 41 is equal to or lower than the reference height L0 during the activation of the pump 22 (step S12).

  As a result, when the detected value L1 is equal to or less than the reference height L0 (YES in step S12), the return control unit 42 opens the return valve V1 to return the liquid in the oil recovery unit 12 to the receiver 20 (return). Operation) is performed (step S13). On the other hand, when the detected value L1 is larger than the reference height L0 (NO in step S12), the return control unit 42 returns to step S12 and determines again whether or not the detected value L1 is equal to or lower than the reference height L0.

  After performing the operation of opening the return valve V1 (after step S13), the return control unit 42 determines whether or not the detection value L2 of the liquid level sensor 43 is equal to or lower than the lower limit height Lα (step S14).

  As a result, if the detected value L2 is equal to or lower than the lower limit height Lα (YES in step S14), that is, the level of the liquid level in the oil recovery unit 12 is the same height as the upstream end of the oil supply passage 13 or higher. The return control unit 42 closes the return valve V1 in order to avoid insufficient supply of the oil in the oil collector 12 through the oil supply passage 13 to the expander 14 (step S16). Return to step S12. On the other hand, when the detected value L2 is larger than the lower limit height Lα (NO in step S14), the return control unit 42 determines whether or not the detected value L1 of the liquid level sensor 41 is larger than the reference height L0 ( Step S15).

  If the detected value L1 is less than or equal to the reference height L0 (NO in step S15), the process returns to step S14. On the other hand, if the detected value L1 is greater than the reference height L0 (YES in step S15), the oil collector 12 In order to stop the flow of liquid into the receiver 20, the return valve V1 is closed (step S16), and the process returns to step S12.

  Next, operation | movement of this thermal energy recovery apparatus is demonstrated. Here, the start-up time (during warm-up operation) of the device will be described. When the device is activated, the return valve V1 is closed.

  First, a heating medium is supplied to the evaporator 10 and a cooling medium is supplied to the condenser 18. Then, the pump 22 is driven. Then, the liquid working medium upstream of the pump 22 is sent to the evaporator 10 where it is evaporated.

  Here, at the time of activation of the present apparatus, the temperature of the liquid in the circulation path 30 between the evaporator 10 and the oil recovery unit 12, the oil recovery unit 12 and the oil recovery unit 12 is a steady operation of the apparatus. Since it is lower than that at the time, the working medium that has flowed out of the evaporator 10 is condensed in the part and the oil recovery unit 12 and collected in the oil recovery unit 12 as a liquid working medium. If it does so, while the liquid level in the oil recovery device 12 will become high, the liquid level in the receiver 20 located in the upstream of the pump 22 will become low.

  As a result, when the detection value L1 of the liquid level sensor 41 provided in the receiver 20 becomes equal to or less than the reference height L0 (when the liquid amount reduction condition is satisfied), the return control unit 42 opens the return valve V1. . As a result, the liquid (oil and liquid working medium) in the oil recovery device 12 flows into the receiver 20 through the return channel 32. Thereafter, when the detected value L2 becomes equal to or lower than the lower limit height Lα, or the detected value L1 becomes larger than the reference height L0, the return control unit 42 closes the return valve V1.

  As described above, the warm-up operation shifts to the steady operation.

  As described above, in the thermal energy recovery device of the present embodiment, when the liquid level in the receiver 20 located on the upstream side of the pump 22 has dropped below the reference height L0, in other words, in the oil recovery unit 12 Since the return operation (operation to open the return valve V1) is performed when the liquid working medium is accumulated, the liquid (oil and working medium) in the oil recovery unit 12 is returned to the receiver 20, so that the pump The amount of liquid on the upstream side of 22 increases early. Accordingly, the 22 unstable operation of the pump and the occurrence of cavitation in the pump 22 at the start (during warm-up operation) are suppressed. For this reason, it is possible to avoid the operation of reducing the rotational speed of the pump 22 during the warm-up operation to be smaller than that during the steady operation, and thus the power recovery machine 16 can effectively recover the power even during the warm-up operation. Is possible.

  Further, since the liquid in the oil recovery unit 12 is returned not to the upstream side of the condenser 18 but to the downstream side of the condenser 18, cooling of the liquid in the condenser 18 is avoided, so that the liquid is condensed into the condenser 18. The working medium contained in the liquid is condensed after flowing out of the evaporator 10 or the working medium contained in the liquid is in a gas-liquid two-phase state compared with the case where the working medium is contained in the liquid. Outflow is suppressed.

  In addition, the liquid level in the receiver 20 is not limited to when the apparatus is activated, but may also occur when the flow rate or temperature of the heating medium supplied to the evaporator 10 is reduced during steady operation. Specifically, when the flow rate or temperature of the heating medium decreases, the liquid working medium does not fully evaporate in the evaporator 10 and flows out of the evaporator 10 in a gas-liquid two-phase state, Since a liquid thing accumulates in the oil recovery device 12, the liquid level of the receiver 20 falls. At this time, since the return control unit 42 performs the same control as described above, not only when the apparatus is started up (during warm-up operation) but also when the flow rate or temperature of the heating medium supplied to the evaporator 10 is decreased. The unstable operation of the pump 22 and the occurrence of cavitation in the pump 22 are effectively suppressed.

  Moreover, in this embodiment, since the liquid which contains much oil with relatively small specific gravity is supplied to the expander 14 from the oil collection | recovery device 12, generation | occurrence | production of the oil film breakage | shortage in the expander 14 is suppressed. Specifically, the specific gravity of the oil is smaller than that of the working medium, and the upstream end of the oil supply passage 13 is located above the upstream end of the return passage 32 to the oil recovery device 12. Since it is connected, the upstream end of the oil supply passage 13 is connected to the oil collector 12 at the same height as the upstream end of the return passage 32 or at a position below it. The ratio of oil to the liquid supplied to the expander 14 through the oil supply passage 13 is increased, thereby increasing the viscosity of the liquid. Therefore, the occurrence of oil film breakage in the expander 14 is suppressed.

  In the present embodiment, an example is shown in which the return control unit 42 closes the return valve V1 when the detected value L1 becomes larger than the reference height L0. Among them, the return valve V1 is turned on until the detected value of the temperature sensor 49 (see FIG. 3) provided in the region between the oil recovery device 12 and the expander 14 becomes equal to or higher than the set temperature (until the warm-up operation is finished). You may open it.

  In this way, during the warm-up operation in which the liquid working medium tends to accumulate in the oil recovery unit 12 (the portion of the circulation channel 30 between the evaporator 10 and the oil recovery unit 12, the oil recovery unit 12 and the circulation Since the return valve V1 continues to open during the operation until the temperature of the portion of the flow path 30 between the oil recovery unit 12 and the expander 14 reaches the set temperature, which is the temperature during normal operation), particularly during startup The unstable operation of the pump 22 and the occurrence of cavitation in the pump 22 can be effectively suppressed.

  Further, as shown in FIG. 4, the receiver 20 may be omitted. In this case, the liquid level sensor 41 is provided in a portion where the liquid level between the condenser 18 and the pump 22 can be detected in the circulation flow path 30, and the downstream end of the return flow path 32 has a circulation flow rate. It connects with the site | part upstream from the position in which the liquid level sensor 41 is provided among the paths 30. Alternatively, in particular, when the heat exchanger has a function of storing a liquid working medium, such as a so-called shell-and-tube heat exchanger as the condenser 18, as shown in FIG. It may be connected to the device 18.

  Moreover, as FIG. 6 shows, you may further have the auxiliary oil supply flow path 13a for supplying the oil in the oil recovery device 12 to the expander 14. FIG. The upstream end of the auxiliary oil supply passage 13a is located below the upstream end of the oil supply passage 13 and at the same height as or lower than the upstream end of the return passage 32. It is connected to the oil collector 12 at the position. The downstream end of the auxiliary oil supply channel 13 a is connected to, for example, an intermediate portion of the oil supply channel 13.

  In this way, even when a liquid working medium accumulates in the oil recovery unit 12, the liquid containing a large amount of oil having a relatively small specific gravity is supplied to the expander 14 through the oil supply passage 13, Even when the liquid level in the recovery device 12 becomes lower than the upstream end of the oil supply passage 13, oil can always be supplied to the expander 14 through the auxiliary oil supply passage 13a. In this case, step S14 in the control flow of the return control unit 42 is omitted. Alternatively, as shown in FIG. 7, the upstream end of the oil supply passage 13 is connected to the bottom of the oil collector 12, and the upstream end of the return passage 32 is connected to the oil supply passage 13. May be. Also in this case, the step S14 is omitted.

(Second Embodiment)
A thermal energy recovery apparatus according to a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, only parts different from the first embodiment will be described, and the description of the same structure, operation, and effect as in the first embodiment will be omitted.

  In the present embodiment, the determination mode for determining whether or not the liquid amount reduction condition is satisfied is different from that in the first embodiment. Specifically, in the present embodiment, the return control unit 42 determines that the liquid amount reduction condition is satisfied when the detection value of the liquid level sensor 45 provided in the oil recovery device 12 is equal to or higher than the upper limit height. Then, the return operation (operation to open the return valve V1) is performed. Further, the return control unit 42 closes the return valve V1 when the detection value of the liquid level sensor 45 becomes less than the upper limit height.

  Even in this case, similarly to the first embodiment, the unstable operation of the pump 22 and the occurrence of cavitation in the pump 22 at the time of startup or when the flow rate or temperature of the heating medium supplied to the evaporator 10 is lowered. It is suppressed. Specifically, at the time of start-up or when the flow rate or temperature of the heating medium decreases, at least a part of the working medium flowing out of the evaporator 10 is stored in the oil recovery unit 12 in a liquid state. Then, while the liquid level in the oil recovery unit 12 is increased, the amount of liquid on the upstream side of the pump 22 (for example, the amount of liquid in the receiver 20) is decreased. It can be determined whether or not the liquid amount reduction condition is satisfied. Therefore, the unstable operation of the pump 22 and the occurrence of cavitation in the pump 22 can be suppressed by opening the return valve V1 when the liquid level of the oil recovery device 12 becomes equal to or higher than the upper limit height.

  In the present embodiment, the upstream end of the oil supply passage 13 is connected to the bottom of the oil collector 12.

  Here, in the present embodiment, a temperature sensor is provided in the oil recovery device 12 instead of the liquid level sensor 45, and the return control unit 42 controls the opening / closing of the return valve V1 based on the detection value of the temperature sensor. Good. Specifically, the return control unit 42 determines that the liquid amount reduction condition is satisfied when the detection value of the temperature sensor becomes lower than the lower limit temperature (for example, the vaporization temperature of the working medium), and performs the return operation (return valve). (Operation for opening V1) may be performed.

  Even in this case, the unstable operation of the pump 22 and the occurrence of cavitation in the pump 22 are suppressed. Specifically, when the temperature of the liquid in the oil collector 12 or the temperature of the oil collector 12 is lower than the vaporization temperature of the working medium, at least a part of the working medium flowing out of the evaporator 10 is contained in the oil collector 12. It condenses and accumulates in the oil collector 12. As a result, the liquid level in the oil recovery unit 12 is increased while the liquid level on the upstream side of the pump 22 is decreased. Therefore, the liquid level is determined based on the temperature of the liquid in the oil recovery unit 12 or the temperature of the oil recovery unit 12. It can be determined whether or not the decrease condition is satisfied. Therefore, by opening the return valve V1 when the temperature of the liquid in the oil recovery unit 12 or the temperature of the oil recovery unit 12 is equal to or lower than the lower limit temperature, unstable operation of the pump 22 or cavitation in the pump 22 is caused. Occurrence can be suppressed. In this case, the return control unit 42 closes the return valve V1 when the detected value of the temperature sensor becomes higher than the lower limit temperature.

(Third embodiment)
Next, a thermal energy recovery device according to a third embodiment of the present invention will be described with reference to FIG. In addition, also about 3rd Embodiment, only a different part from 1st Embodiment is demonstrated, and description of the same structure, an effect | action, and an effect as 1st Embodiment is abbreviate | omitted.

  The thermal energy recovery device of this embodiment includes the auxiliary oil supply passage 13a and a switching valve. The switching valve has a first switching valve V2 provided in the oil supply passage 13 and a second switching valve V3 provided in the auxiliary oil supply passage 13a. The first switching valve V2 is provided in a portion of the oil supply passage 13 that is upstream of the connection portion between the oil supply passage 13 and the auxiliary oil supply passage 13a. Each switching valve V2, V3 is an on-off valve whose opening degree can be adjusted.

  The control unit 40 further includes a switching valve control unit 46 that controls opening and closing of the switching valves V2 and V3. The switching valve control unit 46 opens the first switching valve V2 and closes the second switching valve V3 (opens the oil supply passage 13 and shuts off the auxiliary oil supply passage 13a), and the first switch valve V2. Is closed and the second switching valve V3 is opened (the oil supply passage 13 is shut off and the auxiliary oil supply passage 13a is opened). Specifically, when the liquid level in the oil recovery unit 12 is higher than the upstream end of the oil supply passage 13 (the detected value of the liquid level sensor 43 is upstream of the oil supply passage 13). The first switching valve V2 is opened and the second switching valve V3 is closed (referred to as the first mode), while the liquid level in the oil recovery unit 12 is the oil supply passage. When it is lower than the upstream end of 13, the first switching valve V2 is closed and the second switching valve V3 is opened (referred to as the second mode).

  In this way, when the liquid level in the oil recovery unit 12 is higher than the upstream end of the oil supply passage 13, only the liquid containing a relatively large amount of oil is supplied to the expander 14 through the oil supply passage 13. When the liquid level in the oil recovery unit 12 is lower than the upstream end of the oil supply passage 13, for example, a gaseous working medium flows into the expander 14 through the oil supply passage 13. While suppressing this, oil can be reliably supplied to the expander 14 through the auxiliary oil supply passage 13a.

  In this embodiment, the example in which the first switching valve V2 is provided in the oil supply passage 13 and the second switching valve V3 is provided in the auxiliary oil supply passage 13a is shown. However, the oil supply passage 13 and the auxiliary oil supply are shown. A three-way valve may be provided as the switching valve at the connection with the flow path 13a.

  Further, the downstream end portion of the auxiliary oil supply channel 13 a may be connected to the expander 14.

DESCRIPTION OF SYMBOLS 10 Evaporator 12 Oil recovery machine 13 Oil supply flow path 13a Auxiliary oil supply flow path 14 Expander 16 Power recovery machine (generator)
DESCRIPTION OF SYMBOLS 18 Condenser 20 Receiver 22 Pump 30 Circulation flow path 32 Return flow path 40 Control unit 41 Liquid level sensor 42 Return control part 43 Liquid level sensor 45 Liquid level sensor 46 Switching valve control part 49 Temperature sensor V1 Return valve V2 1st switching valve V3 2nd switching valve

Claims (9)

An evaporator that evaporates the working medium by heating the working medium with a heating medium supplied from the outside;
An oil recovery unit that recovers oil that has flowed out of the evaporator together with the working medium;
An expander that expands the working medium that has flowed out of the oil collector;
A power recovery machine connected to the expander;
A condenser for condensing the working medium flowing out of the expander;
A pump for sending the working medium condensed in the condenser to the evaporator;
A circulation channel for connecting the evaporator, the oil recovery unit, the expander, the condenser and the pump in this order;
A return flow path for returning the liquid in the oil recovery unit to the downstream side of the condenser and the upstream side of the pump in the circulation flow path;
A liquid volume reduction condition is established that indicates that the liquid volume of the working medium in the condenser or the liquid volume of the working medium between the condenser and the pump in the circulation channel has decreased below a reference amount. And a control unit for performing a return operation for returning the liquid in the oil recovery unit through the return flow path. The thermal energy recovery device according to claim 1,
The control unit is configured to detect a liquid level of the working medium in the condenser or a liquid level of the working medium between the condenser and the pump in the circulation channel. A thermal energy recovery device comprising: a surface sensor; and a return control unit that determines that the liquid amount reduction condition is satisfied when a detection value of the liquid level sensor becomes a reference height or less and performs the return operation. . The thermal energy recovery device according to claim 1,
The control unit has a liquid level sensor capable of detecting the height of the liquid level in the oil recovery unit, and the liquid amount reduction condition is satisfied when a detection value of the liquid level sensor exceeds an upper limit height. And a return control unit that performs the return operation by determining that the heat energy is recovered. The thermal energy recovery device according to claim 1,
The control unit includes a temperature sensor capable of detecting the temperature of the liquid in the oil recovery unit or the temperature of the oil recovery unit, and the condition for reducing the amount of liquid when the detected value of the temperature sensor becomes a lower limit temperature or less And a return control unit that performs the return operation after determining that it has been established. The thermal energy recovery device according to claim 1,
The control unit performs the return operation until the temperature of the part of the circulation channel between the oil recovery unit and the expander or the temperature of the working medium flowing through the part reaches or exceeds a set temperature. Recovery device. In the thermal energy recovery device according to any one of claims 1 to 5,
An oil supply passage for supplying oil in the oil recovery unit to the expander;
The specific gravity of the oil is smaller than the specific gravity of the liquid working medium,
The thermal energy recovery device, wherein the upstream end of the oil supply channel is connected to the oil recovery unit at a position above the upstream end of the return channel. The thermal energy recovery device according to claim 6,
An auxiliary oil supply passage for supplying oil in the oil recovery unit to the expander;
The thermal energy recovery device, wherein the upstream end of the auxiliary oil supply channel is connected to the oil recovery unit at a position below the upstream end of the oil supply channel. The thermal energy recovery apparatus according to claim 7,
An end portion on the upstream side of the auxiliary oil supply flow path is connected to the oil recovery device at the same height as or lower than the end on the upstream side of the return flow path. . In the thermal energy recovery device according to claim 7 or 8,
A switching valve capable of switching between a first mode for opening the oil supply channel and blocking the auxiliary oil flow channel and a second mode for blocking the oil supply channel and opening the auxiliary oil flow channel; Prepared,
When the liquid level in the oil recovery unit is located above the upstream end of the oil supply passage, the control unit sets the switching valve as the first mode while the control unit has a liquid level in the oil recovery unit. The thermal energy recovery device further includes a switching valve control unit that uses the switching valve as the second mode when the liquid level is positioned below the upstream end of the oil supply passage.

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