JP6526537B2 - Waste heat recovery system - Google Patents

Description

  The present invention relates to a waste heat recovery apparatus, and more particularly to a waste heat recovery apparatus including a Rankine cycle device.

  As a waste heat recovery apparatus provided with a Rankine cycle apparatus, for example, a waste heat recovery apparatus described in Patent Document 1 is known. In the waste heat recovery device described in Patent Document 1, the Rankine cycle device uses an engine coolant as a heat source for heating (high temperature side heat source), an evaporator that evaporates a working medium, and an operation that has flowed out of the evaporator The expander includes an expander that recovers power by expanding a medium, and a condenser that uses outside air as a heat source for cooling (low temperature side heat source) and condenses a working medium that has flowed out of the expander.

JP, 2014-238007, A

  In the waste heat recovery apparatus as described above, the higher the temperature of the working medium in the evaporator, the higher the pressure (inlet pressure) of the working medium at the inlet of the expander. Also, the lower the temperature of the working medium in the condenser, the lower the pressure (outlet pressure) of the working medium at the outlet of the expander. Therefore, the larger the temperature difference between the high temperature side heat source and the low temperature side heat source, the larger the ratio of the inlet pressure to the outlet pressure of the expander (expansion ratio) can be made, the cycle efficiency improves, and the output (recovered) It is also considered possible to increase the power). However, when the waste heat recovery apparatus is used in an extremely cold environment, for example, the outside air temperature extremely decreases, the expansion ratio becomes too large, and the heat insulation efficiency of the expander may be reduced. In this case, the influence of the decrease in the adiabatic efficiency is larger than the influence of the improvement of the cycle efficiency due to the increase of the expansion ratio, and as a result, the output may be reduced.

  An object of the present invention is to provide a waste heat recovery apparatus capable of suppressing a decrease in output even when the outside air temperature decreases.

  The waste heat recovery apparatus according to the present invention includes an evaporator that evaporates a working medium using engine cooling water as a heat source, an expander that recovers power by expanding the working medium that has flowed out of the evaporator, and outside air. A Rankine cycle device having a condenser that condenses a working medium that has flowed out of an expander, which is used as a heat source, an outside air temperature detection unit that detects an outside air temperature, and a water temperature that lowers the water temperature of cooling water supplied to the evaporator And a controller for controlling the operation of the water temperature reducing means, wherein the controller is configured to cool the evaporator when the outside air temperature detected by the outside air temperature detector is lower than a predetermined judgment temperature. The water temperature lowering means is controlled so that the water temperature of the water decreases.

  In this waste heat recovery apparatus, when the outside air temperature is lower than the determination temperature, the water temperature of the cooling water supplied to the evaporator is reduced. Thereby, the inlet pressure of the expander can be reduced, and as a result, the expansion ratio of the expander can be reduced to an appropriate range in which the influence of the reduction in adiabatic efficiency does not increase. Therefore, according to this waste heat recovery apparatus, it is possible to suppress the decrease in the output even when the outside air temperature decreases.

  Further, the waste heat recovery apparatus according to the present invention further includes an inlet pressure detection unit that detects an inlet pressure of the expander, and an outlet pressure detection unit that detects an outlet pressure of the expander. If the outside air temperature detected by the detection unit is lower than the judgment temperature, the ratio of the inlet pressure detected by the inlet pressure detection unit to the outlet pressure detected by the outlet pressure detection unit becomes smaller than a predetermined set value The water temperature lowering means may be controlled so that the temperature of the cooling water supplied to the evaporator is lowered. In this waste heat recovery apparatus, when the outside air temperature is lower than the determination temperature, the water temperature of the cooling water supplied to the evaporator is reduced until the expansion ratio of the expander becomes smaller than the set value, and the adiabatic efficiency decreases. The expansion ratio of the expander can be reliably reduced to an appropriate range where the influence does not increase. Therefore, even when the outside air temperature decreases, it is possible to reliably suppress the decrease in the output.

  Further, the waste heat recovery apparatus according to the present invention further includes a cooling water flow path for circulating the cooling water so as to be circulated between the engine and the evaporator, and the water temperature lowering means is that the water temperature of the cooling water is higher than the valve opening temperature. The thermostat includes a thermostat that allows the coolant to flow out from the engine to the coolant flow channel when the temperature rises, and the control unit sets the valve opening temperature of the thermostat when the outside temperature detected by the outside air temperature detection unit is lower than the determination temperature. May be lowered. According to this waste heat recovery apparatus, when the outside air temperature is lower than the judgment temperature, the valve opening temperature of the thermostat is lowered, and the cooling water having a lower water temperature is made to flow through the cooling water flow path. The water temperature of the cooling water supplied to the

  In the waste heat recovery apparatus according to the present invention, the cooling water flow path is provided with a radiator for cooling the cooling water, the cooling water flow path has a bypass flow path for bypassing the radiator, and the water temperature reduction means is bypassed The control unit includes a bypass valve that adjusts the flow rate of the cooling water flowing through the flow passage, and the control unit reduces the flow rate of the cooling water flowing through the bypass flow passage when the outside air temperature detected by the outside air temperature detection unit is lower than the determination temperature. As such, the bypass valve may be controlled. According to this waste heat recovery apparatus, when the outside air temperature is lower than the determination temperature, the flow rate of the cooling water flowing through the bypass flow path is decreased, and the flow rate of the cooling water supplied to the radiator is increased. The water temperature of the cooling water supplied to the

  The waste heat recovery apparatus according to the present invention further includes a cooling water flow path for circulating the cooling water so as to circulate between the engine and the evaporator, and the cooling water flow path is provided with a radiator for cooling the cooling water. The cooling water flow path has a bypass flow path for bypassing the radiator, the water temperature reduction means includes a bypass valve for adjusting the flow rate of the cooling water flowing in the bypass flow path, and the control unit is detected by the outside air temperature detection unit If the outside air temperature is lower than the determination temperature, the bypass valve may be controlled to reduce the flow rate of the cooling water flowing through the bypass flow passage. According to this waste heat recovery apparatus, when the outside air temperature is lower than the determination temperature, the flow rate of the cooling water flowing through the bypass flow path is decreased, and the flow rate of the cooling water supplied to the radiator is increased. The water temperature of the cooling water supplied to the

  According to the present invention, it is possible to provide a Rankine cycle device capable of suppressing a decrease in output even when the outside air temperature decreases.

It is a schematic block diagram of the waste heat recovery equipment concerning an embodiment. It is a typical graph showing the relation between the expansion ratio and the adiabatic efficiency in the expander. It is a flowchart which shows the process of the normal mode in the waste-heat collection | recovery apparatus of FIG. It is a flowchart which shows the process of the suppression control mode in the waste-heat collection | recovery apparatus of FIG. It is a flowchart which shows the process of the bypass control mode in the waste-heat collection | recovery apparatus of FIG. It is a schematic block diagram of the waste heat recovery equipment concerning a modification.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements will be denoted by the same reference symbols, without redundant description.

  FIG. 1 is a schematic configuration view of a waste heat recovery apparatus 1 according to the embodiment. As shown in FIG. 1, the waste heat recovery system 1 is mounted on a vehicle equipped with an engine 10. The vehicle to be applied is, for example, a commercial vehicle such as a truck and a bus, and may be a large vehicle, a medium vehicle, a general passenger car, a small vehicle, a light vehicle or the like. The engine 10 is an engine for driving a vehicle, and is, for example, a diesel engine or a gasoline engine.

  The waste heat recovery system 1 includes a Rankine cycle system 20. The Rankine cycle device 20 includes a working medium pump 22, an evaporator 24, an expander 26, and a condenser 28 on the working medium flow path 30. The working medium channel 30 circulates the working medium M to circulate between the working medium pump 22, the evaporator 24, the expander 26, and the condenser 28. As the working medium M, various ones may be used, and in this example, an alternative fluorocarbon which is a low boiling point medium is used.

  The working fluid pump 22 compresses and delivers (pumps) the working fluid M and circulates it within the working fluid channel 30. The evaporator 24 is provided downstream of the working fluid pump 22 in the working fluid passage 30. The evaporator 24 is a heat exchanger using the cooling water C of the engine 10 as a heat source for heating, and heats and evaporates the working medium M by heat exchange with the cooling water C. The cooling water C is supplied to the evaporator 24 via a cooling water flow path 40 described later.

  The expander 26 is provided downstream of the evaporator 24 in the working medium channel 30. The expander 26 recovers power by expanding the working medium M that has flowed out of the evaporator 24. The expander 26 here is a turbine and rotates while expanding the working medium M evaporated in the evaporator 24 to recover kinetic energy as power. The recovered kinetic energy may be output as a mechanical output or may be converted by a generator and output as an electrical output.

  An inlet pressure detection unit 32 for detecting the pressure (inlet pressure) of the working medium M at the inlet of the expander 26 is provided upstream of the expander 26 and downstream of the evaporator 24 in the working medium channel 30. There is. Further, an outlet pressure detection unit 34 for detecting the pressure (outlet pressure) of the working medium M at the outlet of the expander 26 is provided downstream of the expander 26 and upstream of the condenser 28 in the working medium channel 30. It is done. The inlet pressure detection unit 32 and the outlet pressure detection unit 34 are configured by, for example, pressure sensors that can measure the pressures of liquid and gas.

  The condenser 28 is provided downstream of the expander 26 in the working medium channel 30. The condenser 28 uses the outside air A as a heat source for cooling, and cools and condenses the working medium M in the gas phase flowing out of the expander 26. In this example, the condenser 28 cools the working medium M by heat exchange with the refrigerant R. The refrigerant R is cooled using the outside air A, and is supplied to the condenser 28 via a refrigerant flow path 50 described later. As the outside air A, for example, a traveling wind when the vehicle travels is used.

  The waste heat recovery apparatus 1 further includes a cooling water flow passage 40 for circulating the cooling water C so as to circulate between the engine 10 and the evaporator 24. A thermostat 42 is provided on the downstream side (outlet) of the engine 10 in the cooling water flow path 40. The thermostat 42 is, for example, an electronically controlled thermostat. The thermostat 42 detects the water temperature of the cooling water C at the outlet of the engine 10, and opens when the detected water temperature of the cooling water C becomes higher than the valve opening temperature, and the engine 10 to the cooling water passage 40 Allow the cooling water C to flow out. On the other hand, the thermostat 42 closes the valve when the detected water temperature of the cooling water C is equal to or lower than the valve opening temperature, and blocks (blocks) the outflow of the cooling water C from the engine 10 to the cooling water passage 40.

  The valve opening temperature of the thermostat 42 is set by the control unit 70 described later. The valve opening temperature is the temperature of the cooling water C within a range where the reliability of the engine 10 is secured in order to keep the cycle efficiency of the Rankine cycle device 20 as high as possible in the normal time (normal mode described later). Set to keep as high as possible. The normal valve opening temperature is set to, for example, 80.degree.

  In the waste heat recovery apparatus 1 of the present embodiment, as described later, in the suppression control mode, the valve opening temperature of the thermostat 42 is changed to a value lower than the valve opening temperature at the normal time. When the valve opening temperature decreases, cooling water C having a lower water temperature flows through the cooling water flow passage 40. As a result, the water temperature of the cooling water C flowing through the cooling water flow passage 40 is lowered, and the water temperature of the cooling water C supplied to the evaporator 24 is thereby lowered. That is, the thermostat 42 constitutes a water temperature reducing means for reducing the water temperature of the cooling water C supplied to the evaporator 24.

  A radiator 44 is provided downstream of the evaporator 24 in the cooling water passage 40. The radiator 44 cools the cooling water C by, for example, traveling wind (open air) when the vehicle travels. The coolant passage 40 has a bypass passage 46 that bypasses the radiator 44. The bypass flow path 46 is provided with a bypass valve 48 that adjusts the flow rate of the cooling water C flowing through the bypass flow path 46. The bypass valve 48 is, for example, a solenoid valve or a motor-operated valve, and adjusts the flow rate of the cooling water C flowing through the bypass flow path 46 by changing the opening degree in accordance with a control signal input from the control unit 70 described later. In the present specification, the "flow rate" may be a volumetric flow rate or a mass flow rate.

  As the opening degree of the bypass valve 48 decreases, the flow rate of the cooling water C flowing through the bypass flow passage 46 decreases, and the flow rate of the cooling water C flowing into the radiator 44 increases. Therefore, when the opening degree of the bypass valve 48 decreases, the water temperature of the cooling water C flowing through the cooling water flow passage 40 decreases, and the water temperature of the cooling water C supplied to the evaporator 24 decreases. That is, the bypass valve 48 constitutes a water temperature reducing means for reducing the temperature of the cooling water C supplied to the evaporator 24. In addition, in order to keep the cycle efficiency of the Rankine cycle device 20 as high as possible at the normal time, the opening degree of the bypass valve 48 maximizes the water temperature of the cooling water C within the range where the reliability of the engine 10 is ensured. It is controlled to be kept high.

  In the present embodiment, the waste heat recovery apparatus 1 further includes a sub radiator (heat exchanger) 52 and a refrigerant pump 54 on the refrigerant flow path 50. The refrigerant flow path 50 circulates the refrigerant R so as to circulate between the condenser 28, the sub radiator 52, and the refrigerant pump 54. The sub radiator 52 cools the refrigerant R by heat exchange with the outside air A. The refrigerant pump 54 pumps the refrigerant R and circulates it in the refrigerant flow path 50.

  The waste heat recovery apparatus 1 further includes an outside air temperature detection unit 60 that detects the temperature of the outside air A (outside air temperature). The outside air temperature detection unit 60 is configured by, for example, a temperature sensor capable of measuring the outside air temperature. The outside air temperature detection unit 60 may be provided at a position at which the outside air temperature can be detected. For example, the outside air temperature detection unit 60 is provided in the vicinity of the intake port of the sub radiator 52 or the like.

  The waste heat recovery apparatus 1 further includes a control unit 70 electrically connected to at least the inlet pressure detection unit 32, the outlet pressure detection unit 34, the thermostat 42, the bypass valve 48, and the outside air temperature detection unit 60. . The control unit 70 executes the process shown in the flowcharts of FIGS. 3 to 5 described later. The control unit 70 is configured by, for example, a computer including a central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM). Control unit 70 may be further electrically connected to elements other than the above.

  Next, the influence which the fall of external temperature may have on the waste heat recovery apparatus 1 will be described. FIG. 2 is a schematic graph showing the relationship between the ratio of the inlet pressure to the outlet pressure (expansion ratio) in the expander 26 and the adiabatic efficiency. In the waste heat recovery system 1, as the temperature of the working medium M in the evaporator 24 increases, the inlet pressure of the expander 26 increases. In addition, as the temperature of the working medium M in the condenser 28 decreases, the outlet pressure of the expander 26 decreases. Therefore, the expansion ratio of the expander 26 can be increased as the outside air temperature decreases and the temperature difference between the cooling water C (high temperature side heat source) and the outside air A (low temperature side heat source) increases, and the cycle efficiency is improved. It is also conceivable that the output (power to be recovered) can be increased.

  However, generally, the adiabatic efficiency is high in the range of the expansion ratio corresponding to all the outside air temperature range (for example, -20 ° C to 30 ° C) from the midsummer to the extremely cold environment such as the cold winter. As such, it is difficult to design the expander 26. For this reason, as shown in FIG. 2, the expander 26 has an expansion ratio range (appropriate range) P capable of keeping the adiabatic efficiency relatively high. That is, when the temperature difference between the high temperature side heat source and the low temperature side heat source is small and the expansion ratio becomes smaller than the appropriate range P, the adiabatic efficiency decreases due to the underexpansion. On the other hand, when the temperature difference between the high temperature side heat source and the low temperature side heat source is large and the expansion ratio becomes larger than the appropriate range P, the adiabatic efficiency decreases due to overexpansion.

  Therefore, when a general waste heat recovery apparatus is used in an extremely cold environment, the outside temperature drops extremely, and the expansion ratio of the expander 26 becomes larger than the appropriate range P, so that the heat insulation efficiency of the expander 26 is increased. May decrease. In this case, the influence of the decrease in the adiabatic efficiency is larger than the influence of the improvement of the cycle efficiency due to the increase of the expansion ratio, and as a result, the output may be reduced.

  On the other hand, the waste heat recovery apparatus 1 of the present embodiment performs the processing described below to expand the expansion ratio of the expander 26 to the appropriate range P where the high thermal insulation efficiency can be maintained even when the outside air temperature decreases. It is configured to be able to lower the Below, the process by the waste heat recovery apparatus 1 is demonstrated. 3 to 5 are flowcharts showing each process by the waste heat recovery system 1. These processes are performed by the control unit 70. In the initial state, the control mode is the normal mode.

  As shown in FIG. 3, first, it is determined whether the number of revolutions of the engine 10 is larger than a predetermined threshold (S11). This threshold is set, for example, to 500 min-1. If the number of revolutions of the engine 10 is larger than the threshold (YES in S11), the process proceeds to step S12. If the number of revolutions of the engine 10 is equal to or less than the threshold (NO in S11), the process proceeds to step S14.

  In step S12, it is determined whether the outside air temperature detected by the outside air temperature detection unit 60 is lower than a predetermined determination temperature. If the outside air temperature is lower than the determination temperature (YES in S12), the process proceeds to step S13. If the outside air temperature is higher than the determination temperature (NO in S11), the process proceeds to step S14. In step S13, the control mode is switched to the suppression control mode, and the normal mode is ended. In the suppression control mode, as described later, a process for reducing the temperature of the cooling water C is performed.

  The determination temperature in step S12 is a value set in advance in order to appropriately determine whether to start the process for reducing the temperature of the cooling water C. The determination temperature may be set based on experiments, past results and experiences, and simulations, and is set to, for example, -5 ° C. The determination temperature may be a fixed value or a variable value.

  In step S14, the valve opening temperature of the thermostat 42 is set to the normal value, and the opening degree of the bypass valve 48 is set to the normal opening degree. Thereafter, the process returns to step S11, and each process in the normal mode is executed again.

  As shown in FIG. 4, in the suppression control mode, first, the expansion ratio of the expander 26 is calculated from the inlet pressure detected by the inlet pressure detection unit 32 and the outlet pressure detected by the outlet pressure detection unit 34 ( S21). Next, it is determined whether the calculated expansion ratio is larger than a predetermined set value (S22). If the expansion ratio is equal to or less than the set value (NO in S22), the control mode is switched to the normal mode (S23), and the suppression control mode is ended. On the other hand, if the expansion ratio is larger than the set value (YES in S22), the process proceeds to step S24.

  The set value in step S22 is a value set in advance in order to appropriately determine whether the expansion ratio has decreased to the appropriate range P. The set value may be set based on, for example, experiments, past results and experiences, and simulations, and is set to 10, for example. The setting value may be a fixed value or a variable value.

  In step S24, it is determined whether the valve opening temperature of the thermostat 42 is higher than a predetermined lower limit temperature. If the valve opening temperature of the thermostat 42 is higher than the lower limit temperature (YES in S24), the process proceeds to step S25. On the other hand, when the valve opening temperature is equal to or lower than the lower limit temperature (NO in S24), it is determined that the valve opening temperature can not be further reduced, and the process proceeds to step S26. The lower limit temperature in step S24 is a value for appropriately determining whether to end the suppression control mode and start the bypass control mode, and is set to 70 ° C., for example.

  In step S25, the valve opening temperature of the thermostat 42 is decreased. For example, the valve opening temperature of the thermostat 42 is decreased by a predetermined value (for example, 5 ° C.). As a result, the water temperature of the cooling water C flowing through the cooling water flow passage 40 is lowered, and the water temperature of the cooling water C supplied to the evaporator 24 is thereby lowered. Then, it returns to step S21 and performs each processing of suppression control mode again. In step S26, the control mode is switched to the bypass control mode, and the suppression control mode is ended.

  As shown in FIG. 5, in the bypass control mode, first, as in steps S21 and S22, the expansion ratio is calculated (S31), and it is determined whether the calculated expansion ratio is larger than a predetermined set value. (S32). If the expansion ratio is equal to or less than the set value (NO in S32), the control mode is switched to the normal mode (S36), and the bypass control mode is ended. On the other hand, if the expansion ratio is larger than the set value (YES in S32), the process proceeds to step S33. As the set value in step S32, for example, the same value as the set value in step S22 is used.

  In step S33, it is determined whether the opening degree of the bypass valve 48 is larger than a predetermined minimum opening degree. If the opening degree is larger than the minimum opening degree (YES in S33), the process proceeds to step S34. On the other hand, when the opening degree is equal to or less than the minimum opening degree (NO in S33), it is determined that the opening degree of the bypass valve 48 can not be further reduced, and the process proceeds to step S35. The minimum opening degree is a value for appropriately determining whether or not to execute the waste heat recovery suppressing process described later to end the bypass control mode, and is set to, for example, 50%.

  In step S34, by changing the opening degree of the bypass valve 48, the bypass valve 48 is controlled so that the flow rate of the cooling water C flowing through the bypass flow passage 46 is reduced. For example, the opening degree of the bypass valve 48 is decreased by a predetermined value (for example, 5%). As a result, the water temperature of the cooling water C flowing through the cooling water flow passage 40 is lowered, and the water temperature of the cooling water C supplied to the evaporator 24 is thereby lowered. Thereafter, the process returns to step S31, and each process of the bypass control mode is performed again.

  In step S35, a waste heat recovery suppression process is performed. For example, the operation of the working fluid pump 22 is stopped or the discharge amount of the working fluid pump 22 is reduced. Thereby, the waste heat recovery by the waste heat recovery apparatus 1 is suppressed. After execution of the waste heat recovery suppressing process, the control mode is switched to the normal mode (S36), and the bypass control mode is ended.

  As described above, in the waste heat recovery apparatus 1, when the outside air temperature is lower than the determination temperature, the water temperature of the cooling water C supplied to the evaporator 24 is reduced. Thereby, the inlet pressure of the expander 26 can be reduced, and as a result, the expansion ratio of the expander 26 can be reduced to the appropriate range P in which the influence of the reduction in the adiabatic efficiency does not increase. Therefore, according to the waste heat recovery apparatus 1, it is possible to suppress the decrease in output even when the outside air temperature decreases.

  Further, in the waste heat recovery apparatus 1, when the outside air temperature is lower than the determination temperature, the water temperature of the cooling water C supplied to the evaporator 24 is decreased until the expansion ratio of the expander 26 becomes smaller than the set value. The expansion ratio of the expander 26 can be reliably reduced to the appropriate range P where the influence of the decrease in the heat insulation efficiency does not increase. Therefore, according to the waste heat recovery apparatus 1, even when the outside air temperature decreases, it is possible to reliably suppress the decrease in the output.

  Further, according to the waste heat recovery apparatus 1, when the outside air temperature is lower than the judgment temperature, the valve opening temperature of the thermostat 42 is lowered to allow the cooling water C having a lower water temperature to flow through the cooling water flow passage 40. Thus, the water temperature of the cooling water C supplied to the evaporator 24 can be reduced.

  Further, according to the waste heat recovery apparatus 1, when the outside air temperature is lower than the determination temperature, the flow rate of the cooling water C flowing through the bypass flow path 46 is decreased, and the flow rate of the cooling water C supplied to the radiator 44 is increased. By doing this, the water temperature of the cooling water C supplied to the evaporator 24 can be reduced.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the invention as set forth in the claims. May be

  FIG. 6 is a schematic configuration view of a waste heat recovery apparatus according to a modification. For example, as shown in FIG. 6, the present invention may be configured as a waste heat recovery apparatus 1A. The waste heat recovery apparatus 1A of the modified example is the waste heat recovery of the above embodiment in that the bypass valve 48A is provided at the flow dividing position between the flow path on the upstream side of the radiator 44 and the bypass flow path 46 in the cooling water flow path 40. It differs from the device 1. The bypass valve 48A is, for example, a three-way valve, and switches the flow path through which the cooling water C flows between the flow path on the upstream side of the radiator 44 and the bypass flow path 46. Adjust the flow rate. That is, in the waste heat recovery apparatus 1A, in the process corresponding to step S34 described above, the control unit 70 switches the flow path through which the cooling water C flows by the bypass valve 48, so that the cooling water C flowing through the bypass flow path 46 The bypass valve 48 is controlled to reduce the flow rate.

  Even with the waste heat recovery apparatus 1A, as in the above embodiment, it is possible to suppress the decrease in output even when the outside air temperature decreases. Further, the entire amount of the cooling water C flowing through the cooling water flow passage 40 is caused to flow into the bypass flow passage 46, thereby avoiding cooling of the cooling water C by the radiator 44, and the water temperature of the cooling water C flowing through the cooling water flow passage 40 Can be suppressed. As a result, the water temperature of the cooling water C, which is the high temperature side heat source, can be kept high, and the working medium M flowing into the evaporator 24 can be more suitably heated and evaporated.

  In the above embodiment, both the thermostat 42 and the bypass valve 48 are used as the water amount reduction means, but only one of them may be used. When only the thermostat 42 is used as the water amount reduction means, the radiator 44, the bypass flow passage 46 or the bypass valve 48 may be omitted.

  In the embodiment described above, bypass control is executed first in which the suppression control mode (see FIG. 4) for lowering the valve opening temperature of the thermostat 42 is executed and the opening degree of the bypass valve 48 is changed when the expansion ratio is still larger than the set value. Although the mode (see FIG. 5) is further executed, conversely, the bypass control mode may be executed first, or the suppression control mode and the bypass control mode may be simultaneously executed.

  In the above embodiment, when the outside air temperature is lower than the determination temperature, the water amount is reduced such that the water temperature of the cooling water C supplied to the evaporator 24 is decreased until the expansion ratio of the expander 26 becomes smaller than the set value. Although the means was controlled, it is not limited to this. The water amount reduction means may be controlled without determining whether the expansion ratio actually decreases to the appropriate range P. The point is that when the outside air temperature detected by the outside air temperature detection unit 60 is lower than the determination temperature, the water temperature of the cooling water C supplied to the evaporator 24 may be reduced.

  In the above embodiment, the working medium M is cooled by heat exchange between the outside air A and the refrigerant R in the condenser 28. However, as the condenser 28, any one that uses the outside air A as a heat source for cooling may be used. It may be an air-cooled type that directly cools the working medium M using A. Moreover, when the water temperature of the cooling water C does not fall to the appropriate range P even if the said suppression control mode is implemented, control which restrict | limits the output of the engine 10 may be implemented.

  In the above embodiment, when the temperature of the cooling water C becomes higher than the valve opening temperature, the opening degree of the thermostat 42 is changed from 0% (valve closing) to 100% (valve opening), and the coolant flow path from the engine 10 Although the outflow of the cooling water C to 40 was permitted, the opening degree of the thermostat 42 may be changed continuously or stepwise. For example, the opening degree of the thermostat 42 is continuously or stepwise (for example, three or more) so that the opening degree of the thermostat 42 becomes larger as the difference between the water temperature of the cooling water C and the valve opening temperature becomes larger. It may be changed (between the set values).

DESCRIPTION OF SYMBOLS 1 ... Waste heat recovery apparatus, 10 ... Engine, 20 ... Rankin cycle apparatus, 24 ... Evaporator, 26 ... Expansion machine, 28 ... Condenser, 32 ... Inlet pressure detection part, 34 ... Outlet pressure detection part, 40 ... Cooling water flow Path: 42: thermostat, 44: radiator, 46: bypass flow passage, 48: bypass valve, 60: outside air temperature detection unit, 70: control unit, A: outside air, C: cooling water, M: working medium.

Claims (5)

From the expander, an evaporator that evaporates a working medium using engine cooling water as a heat source, an expander that recovers power by expanding the working medium that has flowed out of the evaporator, and using outside air as a heat source A Rankine cycle device having a condenser for condensing the working medium that has flowed out;
An outside temperature detection unit that detects the outside temperature,
Water temperature reducing means for decreasing the temperature of the cooling water supplied to the evaporator;
A control unit that controls the operation of the water temperature reduction means;
The control unit
A waste heat recovery apparatus that controls the water temperature reduction means so that the water temperature of the cooling water supplied to the evaporator decreases when the outside air temperature detected by the outside air temperature detection unit is lower than a predetermined judgment temperature. . An inlet pressure detection unit that detects an inlet pressure of the expander;
And an outlet pressure detection unit that detects an outlet pressure of the expander.
The control unit
When the outside air temperature detected by the outside air temperature detection unit is lower than the determination temperature, a ratio of the inlet pressure detected by the inlet pressure detection unit to the outlet pressure detected by the outlet pressure detection unit is predetermined. The waste heat recovery system according to claim 1, wherein the water temperature reduction means is controlled such that the water temperature of the cooling water supplied to the evaporator decreases until it becomes smaller than a set value. And a coolant passage for circulating the coolant so as to circulate between the engine and the evaporator.
The water temperature reduction means includes a thermostat that allows the coolant to flow out of the engine to the coolant flow path when the temperature of the coolant is higher than the valve opening temperature.
The waste heat recovery system according to claim 1 or 2, wherein the control unit lowers the valve opening temperature of the thermostat when the outside air temperature detected by the outside air temperature detection unit is lower than the determination temperature. The cooling water flow path is provided with a radiator for cooling the cooling water,
The cooling water flow path has a bypass flow path that bypasses the radiator,
The water temperature reduction means includes a bypass valve that adjusts the flow rate of the cooling water flowing through the bypass flow path,
The said control part controls the said bypass valve so that the flow volume of the said cooling water which flows through the said bypass flow path may reduce, when the external temperature detected by the said external temperature detection part is lower than the said determination temperature. The waste heat recovery device according to 3. And a coolant passage for circulating the coolant so as to circulate between the engine and the evaporator.
The cooling water flow path is provided with a radiator for cooling the cooling water,
The cooling water flow path has a bypass flow path that bypasses the radiator,
The water temperature reduction means includes a bypass valve that adjusts the flow rate of the cooling water flowing through the bypass flow passage by changing the opening degree,
The said control part controls the said bypass valve so that the flow volume of the said cooling water which flows through the said bypass flow path may reduce, when the external temperature detected by the said external temperature detection part is lower than the said determination temperature. The waste heat recovery apparatus according to 1 or 2.

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