Loop type heat pipe and waste heat recovery device

Abstract

A loop type heat pipe includes an evaporator located to evaporate a refrigerant by heat-exchanging with a first fluid as a heat source, and a condenser located to liquefy and condense the evaporated vapor refrigerant by heat-exchanging with a second fluid to be heated. The condenser has a refrigerant condensation side on which the condensed liquid refrigerant flows, and a refrigerant un-condensation side on which the vapor refrigerant before being condensed flows. In addition, the loop type heat pipe is provided with a flow limitation portion for flowing the second fluid from the refrigerant condensation side toward the refrigerant un-condensation side. For example, the loop type heat pipe is suitably used for a waste heat recovery device.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-165177 filed on Jun. 14, 2006, the contents of which are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a loop type heat pipe, in which a refrigerant is evaporated by heat from a first fluid as a heat source, and the evaporated vapor refrigerant is cooled by a second fluid to be heated so as to heat the second fluid by condensation latent heat of the vapor refrigerant. For example, the loop type heat pipe can be suitably used for a waste heat recovery device.

2. Description of the Related Art

Conventionally, a loop type heat pipe is described in JP-A-4-45393, for example. This loop type heat pipe is provided with an evaporator for heating and evaporating refrigerant, and a condenser for cooling and condensing the evaporated vapor refrigerant. Furthermore, operation of the loop type heat pipe is controlled by a switching valve (opening and closing valve). The switching valve is located to open and close a passage through which the liquid refrigerant condensed in the condenser returns to the evaporator. Furthermore, the loop type heat pipe is provided with a liquid refrigerant storage portion for storing the liquid refrigerant therein at an upstream side (i.e., condenser side) of the switching valve. In addition, the liquid refrigerant storage portion and the switching valve are located outside of the condenser.

The condenser is located in a tank in which the second fluid to be heated flows, such that the vapor refrigerant introduced to the condenser is heat-exchanged with the second fluid flowing in the tank so as to heat the second fluid. However, in this loop type heat pipe, it is difficult to always improve heating performance of the second fluid to be heated, by a simple structure.

SUMMARY OF THE INVENTION

In view of the foregoing problems, it is an object of the present invention to provide a loop type heat pipe, which can effectively improve heat pump efficiency.

It is another object of the present invention to provide a waste heat recovery device which can effectively improve heat recovery efficiency.

According to an example of the present invention, a loop type heat pipe in which a refrigerant circulates, includes an evaporator located to evaporate the refrigerant by heat-exchanging with a first fluid as a heat source, and a condenser located to liquefy and condense the evaporated vapor refrigerant by heat-exchanging with a second fluid to be heated. The condenser has a refrigerant condensation side on which the condensed liquid refrigerant flows, and a refrigerant un-condensation side on which the vapor refrigerant before being condensed flows. Furthermore, the loop type heat pipe is provided with a flow limitation means for flowing the second fluid from the refrigerant condensation side toward the refrigerant un-condensation side. Therefore, the condensed liquid refrigerant can be effectively cooled to a low temperature because a temperature difference between the refrigerant and the second fluid can be made larger on both the refrigerant condensation side and the refrigerant un-condensation side. Accordingly, the temperature of the liquid refrigerant to be supplied to the evaporator can be lowered, and heat absorbing amount of the refrigerant in the evaporator can be increased. As a result, heat pump efficiency of the loop type heat pipe can be effectively increased and thereby improving heating performance of the second fluid to be heated.

For example, a liquid refrigerant storage portion may be provided to store the condensed liquid refrigerant. In this case, the flow limitation means is provided for flowing the second fluid from a side of the liquid refrigerant storage portion toward the refrigerant un-condensation side. Furthermore, the liquid refrigerant storage portion may be a part of the condenser.

Alternatively, an operation stop means for stopping the evaporation of the refrigerant in the evaporator may be provided. For example, the operation stop means may be a switching valve located to open and close a passage through which the liquid refrigerant condensed in the condenser flows to the evaporator, or may be a flow control means for controlling a flow amount of the first fluid flowing to the evaporator. Furthermore, the loop type heat pipe may be suitably used for recovering waste heat of exhaust gas from an engine. In this case, the first fluid is an exhaust gas of the engine, the second fluid is a coolant used for a coolant circuit of the engine, and the evaporator and the condenser are located to recovery waste heat from the exhaust gas.

According to another example of the present invention, a waste heat recovery device includes: a loop-type heat pipe including an evaporator located to evaporate a refrigerant by performing a heat exchange with a first fluid, and a condenser located to cool and condense the evaporated vapor refrigerant from the evaporator; a first fluid flowing portion in which the first fluid flows to perform heat exchange with the refrigerant flowing in the evaporator; a second fluid flowing portion in which the second fluid flows to perform heat exchange with the refrigerant flowing in the condenser; an introducing pipe for introducing the second fluid to the second fluid flowing portion; and a discharging pipe for discharging the second fluid from the second fluid flowing portion after passing through the second fluid flowing portion. Furthermore, the condenser has a refrigerant condensation side on which the condensed liquid refrigerant flows, and a refrigerant un-condensation side on which the vapor refrigerant before being condensed flows. In addition, the introducing pipe is connected to the second fluid flowing portion at the refrigerant condensation side of the condenser, and the discharging pipe is connected to the second fluid flowing portion at the refrigerant un-condensation side of the condenser. Therefore, the condensed liquid refrigerant can be effectively cooled to a low temperature because a temperature difference between the refrigerant and the second fluid can be made larger on both the refrigerant condensation side and the refrigerant un-condensation side. Accordingly, the temperature of the liquid refrigerant to be supplied to the evaporator can be lowered, and heat absorbing amount of the refrigerant in the evaporator can be increased. As a result, heat recovery efficiency (heat pump efficiency) of the waste heat recovery device can be effectively increased.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings. In which:

FIG. 1 is a schematic diagram showing a loop type heat pipe used for a waste heat recovery device, according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram showing the waste heat recovery device for a vehicle engine, according to the first embodiment;

FIG. 3 is a schematic diagram showing a loop type heat pipe used for a waste heat recovery device, according to a second embodiment of the present invention; and

FIG. 4 is a schematic diagram showing a loop type heat pipe used for a waste heat recovery device, according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A first embodiment will be now described with reference to FIGS. 1 and 2. In this embodiment, a loop type heat pipe is typically used for a waste heat recovery device.

First, a basic structure of the waste heat recovery device will be now described. An engine (internal combustion engine) 1 is located for generating a rotation output for a vehicle running by fuel combustion. The engine 1 is generally provided with a coolant circuit for controlling heat generated in the engine 1, and an exhaust pipe 2 for discharging exhaust gas to atmosphere.

The coolant circuit includes a radiator circuit 3, a heater circuit 4 and a waste heat recovery circuit 5. Furthermore, a catalytic converter 6 for purifying the exhaust gas and the waste heat recovery device 7 are located in the exhaust pipe 2.

Next, the coolant circuit including the radiator circuit 3, the heater circuit 4 and the waste heat recovery circuit 5 will be described.

A radiator 9 is located to perform heat exchange between the coolant circulated by a water pump 8 and outside air so as to cool the coolant. A bypass passage 10, through which the coolant flows while bypassing the radiator 9, is provided in the radiator circuit 3. A thermostat 11 is located in the radiator circuit 3.

The thermostat 11 adjusts a ratio between a coolant amount passing through the radiator 9 and a coolant amount passing through the radiator bypass passage 10 such that the temperature of the coolant is controlled in a temperature range (e.g., 80° C. to 100° C.). For example, when the temperature of the coolant is low in an engine heating time, the coolant amount supplying to the radiator bypass passage 10 is increased so as to facilitate the engine heating operation at the engine heating time.

The heater circuit 4 is connected to the engine 1, such that the coolant flows out of the engine 1 from a position different from an engine outlet for the radiator circuit 3, and is joined to the waste heat recovery circuit 5 on a downstream side of the waste heat recovery device 7. A heater core 12 is located in the heater circuit 4 to heat a fluid by using heat from the coolant. For example, the heater core 12 is located in an air duct for a vehicle air conditioner such that air flowing in the air duct is heat exchanged with the coolant. Therefore, air to be blown into a vehicle compartment is heated by the heater core 12.

The waste heat recovery circuit 5 is branched from the radiator circuit 3 in a passage from the engine 1 to the radiator 9, and is joined to the water pump 8. Therefore, the coolant is circulated in the waste heat recovery circuit 5 by operation of the water pump 8. A water tank 13 (fluid tank) provided in the waste heat recovery device 7 is connected to a passage of the waste heat recovery circuit 5.

Next, the waste heat recovery device 7 will be described. The waste heat recovery device 7 is located to recover heat generated from the exhaust gas (first fluid as a heat source) and to heat the coolant (second fluid to be heated) flowing in the waste heat recovery circuit 5 by using the loop type heat pipe that performs heat transport (heat pump) due to refrigerant evaporation and refrigerant condensation. In this embodiment, the waste heat recovery device 7 heats the coolant by using heat of the exhaust gas after passing through the catalytic converter 6.

In this embodiment, an evaporator 14 and a condenser 15 contained in a tank 13 (e.g., coolant tank) are integrally formed to construct the loop type heat pipe. Furthermore, a switching valve such as a differential pressure regulating valve 16 is located to control the operation of the loop type heat pipe in accordance with an interior pressure of the loop type heat pipe.

For example, the evaporator 14 and the condenser 15 accommodated in the tank 13 are made of an anti-corrosion material (e.g., stainless steel), and are integrally bonded using a bonding technique such as brazing. After the bonding, the differential pressure regulating valve 16 is assembled to the integrated member of the evaporator 14 and the condenser 15, so as to form the loop type heat pipe used for the waste heat recovery device 7.

The waste heat recovery device 7 has a sealing portion (not shown). After the interior of the waste heat recovery device 7 is vacuated and a refrigerant (operation fluid) is filled therein, the sealing portion is sealed.

In this embodiment, as one example of the refrigerant, water is used. The water has a boiling point of 100° C. at 1 atm. Because the interior of the waste heat recovery device 7 is decompressed and vacuated to, for example, 0.01 atm, water in the waste heat recovery device 7 has a boiling point in a range of 5° C.-10° C. As the refrigerant, an operation fluid other than water, such as alcohol, fluorocarbon, Freon, etc. may be used.

The evaporator 14 is a heat exchanger in which the exhaust gas passing through the exhaust pipe 2 is heat exchanged with water flowing in the evaporator 14. Any type heat exchanger, for example, a laminated-type heat exchanger, a header type heat exchanger, a drawn-cup type heat exchanger may be used as the evaporator 14. The evaporator 14 includes a heat exchanging portion 17, a lower tank 18 and an upper tank 19.

For example, the heat exchanging portion 17 is a laminated type in which tubes 17a and fins 17b are alternately laminated in a lamination direction. The heat exchanging portion 17 is mounted on a vehicle such that the longitudinal direction of the tubes 17a are directed in the up-down direction of the vehicle. The fins 17b may be omitted in the heat exchanging portion 17. In this case, the exhaust efficiency and durability can be improved in the heat exchanging portion 17, although the refrigerant evaporation capacity is decreased.

The lower tank 18 is positioned at a lower side of the heat exchanging portion 17 when the waste heat recovery device 7 is mounted on the vehicle. The differential pressure regulating valve 16 is located in the lower tank 18, such that condensed water supplied from the differential pressure regulating valve 16 is distributed into the tubes 17 through the lower tank 18. The upper tank 19 is positioned at an upper side of the heat exchanging portion 17 when the waste heat recovery device 7 is mounted on the vehicle, such that the evaporated vapor refrigerant rising in the tubes 17a is collected in the upper tank 19. The evaporated vapor refrigerant collected in the upper tank 19 is introduced to the condenser 15.

The condenser 15 is located in the tank 13 in which the coolant flows. The tank 13 is a container, and is located such that the coolant flows between the tank 13 and the evaporator 14. For example, the tank 13 is constructed with a tank plate connected to a side surface of the evaporator 14, and a tank cup connected to the tank plate to receive the condenser 15. A coolant introducing pipe 21 for introducing the coolant into the tank 13, and a coolant discharging pipe 22 for discharging the coolant after passing through the tank 13 are connected to the tank 13.

The condenser 15 is a heat exchanger in which the vapor refrigerant supplied from the evaporator 14 is heat exchanged with the coolant flowing in the tank 13. Any type heat exchanger, for example, a laminated-type heat exchanger, a header type heat exchanger, a drawn-cup type heat exchanger may be used as the condenser 15. In this embodiment, the condenser 15 is located on the side surface of the evaporator 14, adjacent to the evaporator 14, as shown in FIG. 1.

The condenser 15 includes a heat exchanging portion 23, a refrigerant upstream tank 24 and a refrigerant downstream tank 25. The heat exchanging portion 23 includes a plurality of tubes 23a that are laminated at intervals. The coolant passes through the clearances between the tubes 23a in the tank 13 to be heat exchanged with the refrigerant flowing in the tubes 23a. Each of the tubes 23a extends between the refrigerant upstream tank 24 and the refrigerant downstream tank 25 in parallel with the tubes 17a of the evaporator 14. The waste heat recovery device 7 is mounted on the vehicle such that the longitudinal direction of the tubes 23a of the heat exchanging portion 23 is directed in the vertical direction. Fins may be located on the tubes 23a of the heat exchanging portion 23 in order to improve heat exchanging efficiency.

When the waste heat recovery device 7 is mounted on the vehicle, the refrigerant upstream tank 24 is positioned on the upper side of the heat exchanging portion 23, and the refrigerant downstream tank 25 is positioned on the lower side of the heat exchanging portion 23, in this embodiment. Therefore, vapor refrigerant supplied from the upper tank 19 of the evaporator 14 to the refrigerant upstream tank 24 is distributed into the tubes 23a to be cooled and condensed by the coolant flowing in the tank 13. Then, the condensed liquid refrigerant from the tubes 23a is collected to the refrigerant downstream tank 25 and is introduced to the differential pressure regulating valve 16.

Next, the differential pressure regulating valve 16 used as an operation stop means for stopping the evaporation of refrigerant in the evaporator 14 will be described. The differential pressure regulating valve 16 is one example of an opening and closing valve type, and is located in a communication passage through which the liquid refrigerant condensed in the condenser 15 is introduced to the evaporator 14.

When the interior pressure of the waste heat recovery device 7 is increased to be larger than a first value, the differential pressure regulating valve 16 is closed to shut the communication between the lower tank 18 of the evaporator 14 and the refrigerant downstream tank 25 of the condenser 15 so as to prevent an exceed pressure increase in the waste heat recovery device 7. In contrast, when the interior pressure of the waste heat recovery device 7 is decreased to be lower than a second value lower than the first value, the differential pressure regulating valve 16 opens the communication passage between the lower tank 18 of the evaporator 14 and the refrigerant downstream tank 25 of the condenser 15 so as to restart the waste heat recovery operation of the waste heat recovery device 7.

In this embodiment, the differential pressure regulating valve 16 is an opening and closing valve (switching valve) which performs the communication or the shutting between the refrigerant downstream tank 25 of the condenser 15 and the lower tank 18 of the evaporator 14, based on a differential pressure between the interior pressure of the waste heat recovery device 7 and the atmosphere. If the atmosphere is constant, when the interior pressure of the waste heat recovery device 7 is increased to a valve closing pressure Pc, the communication between the lower tank 18 of the evaporator 14 and the refrigerant downstream tank 25 of the condenser 15 is shut. In contrast, when the interior pressure of the waste heat recovery device 7 is decreased to a valve opening pressure Po that is lower than the valve opening pressure Pc, the lower tank 18 of the evaporator 14 and the refrigerant downstream tank 25 of the condenser 15 are made to be communicated with each other by the differential pressure regulating valve 16.

FIG. 1 shows an example structure of the differential pressure regulating valve 16. As shown in FIG. 1, the differential pressure regulating valve 16 includes a housing 26, a valve body 27, a diaphragm 28 and a return spring (not shown).

The housing 26 is an approximately cylindrical member located in the refrigerant downstream tank 25, and the valve body 27 is held in the housing 26 to be movable in an axial direction. The housing 26 has an inner space 26a, and the inner space 26a communicates with the refrigerant downstream tank 25 through a side port 26b so that the liquid refrigerant in the refrigerant downstream tank 25 flows into the inner space 26a of the housing 26 of the differential pressure regulating valve 16.

The inner space 26a of the housing 26 communicates with the lower tank 18 of the evaporator 14 through a valve open port 26c that is opened and closed by a valve body 27. Therefore, when the valve open port 26c is opened by the valve body 27, the liquid refrigerant in the inner space 26a flows into the lower tank 18 through the valve open port 26c.

The valve body 27 is held in the housing 26 to be displaceable in its axial direction. The valve body 27 is provided with a valve bell 27a which opens and closes the valve open port 26c in accordance with a displacement of the valve body 27 in the axial direction. The diaphragm 28 is located to displace the valve body 27 in the axial direction based on the differential pressure between the interior pressure of the waste heat recovery device 7 and the atmosphere, and to prevent panting of the differential pressure regulating valve 16 by reflection operation of the diaphragm 28.

The return spring (not shown) is a spring member that biases the valve body 27 from the atmosphere side to the valve opening direction. By adjusting the biasing force of the return spring, the valve open pressure Po for displacing the diaphragm 28 to the valve opening direction and the valve close pressure Pc for displacing the diaphragm 28 to the valve closing direction can be adjusted.

As an example, the valve open pressure Pc is set at an interior pressure of the waste heat recovery device 7 when the operation load of the engine 1 is a half throttle load at a temperature (e.g., 70° C.) of the coolant immediately after finishing the engine heating. Furthermore, the valve open pressure Po is set at an interior pressure of the waste heat recovery device 7 in an engine idling (zero load operation) at a temperature (e.g., 70° C.) of the coolant immediately after finishing the engine heating.

Next, operation of the waste heat recovery device 7 will be described. When the engine 1 starts its operation, the water pump 8 is operated such that the coolant is circulated in the radiator circuit 3, the heater circuit 4 and the waste heat recovery circuit 5. At the same time, exhaust gas generated with the fuel combustion of the engine 1 flows into the exhaust pipe 2, the catalytic converter 6 and the evaporator 14 of the waste heat recovery device 7, and then is discharged to the atmosphere.

In this example, as the refrigerant circulating in the loop type heat pipe between the evaporator 14 and the condenser 15, water is used. Therefore, the exhaust gas from the engine 1 through the exhaust pipe 2 heats water as the refrigerant within the evaporator 14 while passing through the evaporator 14. The water in the evaporator 14 is boiled and evaporated by absorbing heat from the exhaust gas, and the evaporated water vapor flows in the tubes 17a upwardly to be collected into the upper tank 19. Then, the water vapor flows from the upper tank 19 of the evaporator 14 into the refrigerant upstream tank 24 of the condenser 15. The water vapor (refrigerant vapor) introduced into the condenser 15 is cooled and condensed by the coolant flowing in the tank 13.

Immediately after the engine 1 starts its operation, the interior pressure of the waste heat recovery device 7 is not increased to the valve close pressure Pc. In this case, the differential pressure regulating valve 16 is opened, thereby the condensed water cooled and condensed in the condenser 15 returns to the lower tank 18 of the evaporator 14 through the differential pressure regulating valve 16. With this, the waste heat recovery cycle can be repeated in the waste heat recovery device 7.

Accordingly, heat of the exhaust gas is transmitted to the refrigerant (e.g., water) in the evaporator 14. Therefore, the water as the refrigerant is evaporated in the evaporator 14 by absorbing heat from the exhaust gas, and heat contained in the water as the refrigerant is exhausted as condensation latent heat while being condensed so as to heat the coolant circulating in the waste heat recovery circuit 5. Here, a part of heat of the exhaust gas is transmitted to members constructing the evaporator 14 and the condenser 15, and heats the coolant flowing in the waste heat recovery circuit 5 via those members.

As a result, the heating of the engine 1 can be facilitated at an engine start time, and a fuel increasing time (auto choke operation ratio) for facilitating the engine heating can be shortened, thereby improving fuel consumption efficiency.

When the temperature of the exhaust gas is increased in accordance with increase of the engine load after operation of the engine 1 starts, the heat quantity of the exhaust gas for heating the water as the refrigerant in the evaporator 14 is increased, and the vapor amount generated in the evaporator 14 is increased thereby increasing the interior pressure of the loop type heat pipe in the waste heat recovery device 7. When the interior pressure of the loop type heat pipe in the waste heat recovery device 7 is increased to the valve close pressure Pc, the differential pressure regulating valve 16 is closed, so that condensed water in the condenser 15 does not return to the evaporator 14. Therefore, water is not supplied to the evaporator 14 from the condenser 15, and evaporation in the evaporator 14 is reduced thereby the waste heat recovery cycle is stopped. In contrast, because the condensation of water vapor in the condenser 15 is performed, the interior pressure of the loop type heat pipe in the waste heat recovery device 7 is decreased.

When the interior pressure of the loop type heat pipe in the waste heat recovery device 7 is reduced to the valve open pressure Po, the differential pressure regulating valve 16 is opened, and the condensed water in the condenser 15 flows into the lower tank 18 of the evaporator 14 through the differential pressure regulating valve 16. Therefore, water as the refrigerant is evaporated again in the evaporator 14, and the waste heat recovery cycle is restarted.

According to the first embodiment of the present invention, the waste heat recovery device 7 is provided with a flow limitation means for performing a flow of the coolant from a refrigerant condensation side (i.e., a side of the refrigerant downstream tank 25) to a refrigerant un-condensation side (i.e., a side of the refrigerant upstream tank 24). Here, the refrigerant condensation side is a side on which the condensed liquid refrigerant stays or flows, and the refrigerant un-condensation side is a side on which the vapor refrigerant before being condensed stays or flows. That is, as the flow limitation means, the coolant introducing pipe 21 for introducing the coolant into the tank 13 is located at a most downstream side (refrigerant condensation side) of the condenser 15 in a refrigerant flow direction, and the coolant discharging pipe 22 for discharging the coolant after passing through the tank 13 is located at a most upstream side (refrigerant un-condensation side) of the condenser 15 in the refrigerant flow direction. In this arrangement of FIG. 1, the coolant introducing pipe 21 is located at a bottom portion of the tank 13, and the coolant discharging pipe 22 is located at a top portion of the tank 13, so as to form the flow limitation means.

In the first embodiment, because the coolant introducing pipe 21 is located at the bottom portion of the tank 13 and the coolant discharging pipe 22 is located at the top portion of the tank 13, the coolant flows in a direction from the refrigerant condensation side (i.e., the side of the refrigerant downstream tank 25) toward the refrigerant un-condensation side (i.e., the side of the refrigerant upstream tank 24). Therefore, liquid refrigerant condensed in the condenser 15 can be cooled by the coolant before being heated or slightly heated to have a relatively low temperature. Accordingly, the liquid refrigerant to be supplied to the evaporator 14 can be cooled to a relatively low temperature so as to be super-cooled.

With this, the temperature of liquid refrigerant returned to the evaporator 14 is decreased, thereby increasing a temperature difference between the liquid refrigerant returned to the evaporator 14 and the vapor refrigerant evaporated in the evaporator 14. Thus, it is possible to increase the heat quantity obtained from the exhaust gas in the evaporator 14, thereby increasing heat recovery efficiency (heat pump efficiency) in the waste heat recovery device 7.

Furthermore, in the first embodiment, the vapor refrigerant immediately after being introduced to the condenser 15 has a high temperature, and its temperature is lowered as the condensation is more performed. That is, the refrigerant has a high temperature at the refrigerant un-condensation side (i.e., the side of the refrigerant upstream tank 24), and the temperature of the refrigerant is lowered as the refrigerant moves toward the refrigerant condensation side (i.e., the side of the refrigerant downstream tank 25). In contrast, the coolant introducing pipe 21 is located at the bottom portion of the tank 13 and the coolant discharging pipe 22 is located at the top portion of the tank 13, so that the coolant flows in the direction from the refrigerant condensation side (i.e., the side of the refrigerant downstream tank 25) toward the refrigerant un-condensation side (i.e., the side of the refrigerant upstream tank 24), as described above. Therefore, the coolant having been heated by the condensed liquid refrigerant having a relative low temperature, can be further heated by the un-condensation vapor refrigerant having a relative high temperature. Accordingly, the temperature of the coolant heated by the condenser 15 while passing through the tank 13 can be effectively increased.

In addition, in the waste heat recovery device 7 of the first embodiment, the differential pressure regulating valve 16 is closed when the interior pressure of the loop type heat pipe in the waste heat recovery device 7 is increased. Therefore, it can prevent the waste heat recovery device 7 from being overheated during a high engine load in the summer, thereby preventing the waste heat recovery device 7 from being damaged. Furthermore, the liquid refrigerant storage portion 29 for storing the condensed liquid refrigerant is located in the condenser 15 at a refrigerant upstream side of the valve open port 26c of the differential pressure regulating valve 16. Therefore, when the differential pressure regulating valve 16 is closed, the amount of the liquid refrigerant stored in the liquid refrigerant storage portion 29 is increased.

On the other hand, when the differential pressure regulating valve 16 is opened, the liquid refrigerant of the condenser 15 flows into the evaporator 14 by using the difference between the liquid height (liquid surface position of the refrigerant in the condenser 15) in the liquid refrigerant storage portion 29 and the liquid height (liquid surface position of the refrigerant in the evaporator 14) of the evaporator 14. Therefore, even when the differential pressure regulating valve 16 is opened, the liquid refrigerant storage portion 29, in which condensed liquid refrigerant is stored, can be formed at a refrigerant downstream side position of the condenser 15 and at a refrigerant upstream side position of the valve open port 26c of the differential pressure regulating valve 16.

The waste heat recovery device 7 of this embodiment is provided with the liquid refrigerant storage portion 29 for storing the liquid refrigerant to the lower portion in the condenser 15, and the flow limitation means for flowing the coolant from the side of the liquid refrigerant storage portion 29 to the refrigerant un-condensation portion of the condenser 15. Accordingly, the liquid refrigerant condensed in the condenser 15 can be super-cooled by the unheated coolant or the coolant having a relative low temperature, thereby the liquid refrigerant returned to the evaporator 14 can be accurately cooled to a low temperature.

Second Embodiment

The second embodiment will be described with reference to FIG. 3. In the second embodiment, members having the same functions as those of the above-described first embodiment are indicated by the same reference numbers.

In the waste heat recovery device 7 of the above-described first embodiment, the tubes 23a of the condenser 15 are elongated in the vertical direction so that liquid refrigerant moves downwardly by its weight when the waste heat recovery device 7 is mounted on a vehicle. That is, in the above-described first embodiment, the condenser 15 is located on the side surface of the evaporator 14 such that the tubes 17a of the evaporator 14 and the tubes 23a of the condenser 15 are arranged in parallel with each other to be elongated in the vertical direction when the waste heat recovery device 7 is mounted on a vehicle. However, in the second embodiment, the condenser 15 is located such that the longitudinal direction of the tubes 23a of the condenser 15 is approximately perpendicular to the longitudinal direction of the tubes 17a of the evaporator 14.

As shown in FIG. 3, in a waste heat recovery device 7 of the second embodiment, the condenser 15 is located at a top portion of the evaporator 14, such that the tubes 23a of the condenser 15 are elongated in the vehicle horizontal direction and the tubes 17a of the evaporator 14 are elongated in the vehicle vertical direction when the waste heat recovery device 7 is mounted on the vehicle.

The refrigerant upstream tank 24 of the condenser 15 is connected to the upper tank 19 of the evaporator 14 to directly communicate with the upper tank 19 of the evaporator 14. The differential pressure regulating valve 16 is located in the refrigerant downstream tank 25 of the condenser 15 to adjust the flow of refrigerant from the refrigerant downstream tank 25 to the evaporator 14, similarly to the above-described first embodiment.

An open outlet of the differential pressure regulating valve 16 is connected to the lower tank 18 of the evaporator 14 through a liquid refrigerant passage 31. The liquid refrigerant passage 31 may be constructed outside of the evaporator 14 or may be constructed inside of the evaporator 14. When the liquid refrigerant passage 31 is constructed inside of the evaporator 14 by using a part of the tubes 17a, a heat insulation material is used for the tube 17a used as the liquid refrigerant passage 31 so that the liquid refrigerant is not evaporated while passing through the liquid refrigerant passage 31.

The tubes 23a of the condenser 15 are elongated approximately horizontally when being mounted on the vehicle. Even in this case, the refrigerant inside the tubes 23a of the condenser 15 flows to the refrigerant downstream tank 25 by the pressure of the evaporated vapor refrigerant supplied from the refrigerant upstream tank 24, so that condensed liquid refrigerant is collected to the refrigerant downstream tank 25.

Accordingly, even when the tubes 23a of the condenser 15 are arranged to be elongated in the horizontal direction, the liquid refrigerant to be supplied to the evaporator 14 can be collected to a side of the refrigerant downstream tank 25 of the condenser 15. In the second embodiment, the waste heat recovery device 7 is provided with a flow limitation means such that coolant flows in a direction from the refrigerant condensation side (i.e., the side of the refrigerant downstream tank 25) toward the refrigerant un-condensation side (i.e., the side of the refrigerant upstream tank 24), similarly to the above-described first embodiment. Specifically, the coolant introducing pipe 21 is connected to the tank 13 at the side of the refrigerant downstream tank 25, and the coolant discharge pipe 22 is connected to the tank 13 at the side of the refrigerant upstream tank 24 so as to form the flow limitation means.

In the second embodiment, the other parts may be made similar to those of the above-described first embodiment.

Third Embodiment

A third embodiment will be now described with reference to FIG. 4. In the above-described first and second embodiments, the differential pressure regulating valve 16 is used as one example of the operation stop means of the waste heat recovery device 7, to open and close the communication passage through which the liquid refrigerant condensed in the condenser 15 flows to the evaporator 14. However, in a waste heat recovery device 7 of the third embodiment, as shown in FIG. 4, the differential pressure regulating valve 16 is not provided. In the third embodiment, an operation stop means for stopping evaporation of the refrigerant in the evaporator 14 is constructed without using the differential pressure regulating means 16. For example, a fluid control means for controlling a supply amount of exhaust gas (first fluid for heating) introduced to the evaporator 14 through the exhaust gas pipe 2 is provided so as to stop the evaporation of refrigerant in the evaporator 14.

For example, the fluid control means is a switching means for switching an exhaust passage through which the exhaust gas passes through the evaporator 14. By controlling the amount of the exhaust gas passing through the evaporator 14 to be heat exchanged with the refrigerant by using the fluid control means, the evaporation amount of the refrigerant in the evaporator 14 can be controlled.

Furthermore, even when the differential pressure regulating means 16 described in the first and second embodiments is not provided, the liquid refrigerant to be returned to the evaporator 14 is collected to a refrigerant downstream portion of the condenser 15. Accordingly, in the third embodiment, the waste heat recovery device 7 is provided with a flow limitation means such that the coolant (second fluid to be heated) flows in a direction from the refrigerant condensation side (i.e., the side of the refrigerant downstream tank 25) toward the refrigerant un-condensation side (i.e., the side of the refrigerant upstream tank 24), similarly to the above-described first embodiment. Specifically, the coolant introducing pipe 21 is connected to the tank 13 at the side of the refrigerant downstream tank 25, and the coolant discharge pipe 22 is connected to the tank 13 at the side of the refrigerant upstream tank 24 so as to form the flow limitation means.

In the example of FIG. 4, the evaporator 14 and the condenser 15 are constructed of a drawn-cup heat exchanger. However, the evaporator 14 and the condenser 15 may be constructed of the other type heat exchanger, for example, a laminated type heat exchanger and a header type heat exchanger.

In the example of FIG. 4, the upper tank 19 of the evaporator 14 and the refrigerant upstream tank 24 of the condenser 15 are connected by a vapor refrigerant passage 32, and the lower tank 18 of the evaporator 14 and the refrigerant downstream tank 25 of the condenser 15 are connected by a liquid refrigerant passage 31. However, the upper tank 19 of the evaporator 14 and the refrigerant upstream tank 24 of the condenser 15 may be directly connected, and the lower tank 18 of the evaporator 14 and the refrigerant downstream tank 25 of the condenser 15 may be directly connected. Furthermore, a throttle may be provided in a passage between the lower tank 18 of the evaporator 14 and the refrigerant downstream tank 25 of the condenser 15.

In the third embodiment, the other parts may be made similar to those of the above-described first embodiment.

Other Embodiments

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

For example, in the above-described first and second embodiments, the differential pressure regulating valve 16 is used as an example of a switching valve (opening and closing valve). However, as the switching valve, a thermo valve for opening and closing its valve in accordance with a temperature of the coolant, an electrical valve (e.g., electromagnetic valve) opened and closed by a control unit (ECU) based on an operation state (e.g., a detection value, a predetermined value).

In the above-described first and second embodiments, the switching valve (e.g., the differential pressure regulating valve 16) is disposed inside the refrigerant downstream tank 25 of the condenser 15 outside of the condenser 15. However, the switching valve may be located under the condenser 15. Even in this case, the switching valve is located to construct a part of the liquid refrigerant storage portion 29, and the flow limitation means is constructed such that the coolant flows from a side of the switching valve to a side of the refrigerant downstream tank 25 of the condenser 15.

In the above-described embodiments, the exhaust gas is used as an example of a heat source first fluid. However, the other waste heat such as a battery waste heat, an inverter waste heat, and an intercooler waste heat may be used as the heat source first fluid.

In the above-described embodiments, the loop type heat pipe constructed with the evaporator 14 and the condenser 15 is typically used for a waste heat recovery device for a vehicle. However, the loop type heat pipe of the present invention can be used for the other use for a fixed equipment, for example.

In the above-described embodiments, the exhaust gas of the engine is used as an example of a heat source fluid (first fluid), and the coolant is used as an example of a fluid to be heated (second fluid). However, any other heat source fluid may be used instead of the exhaust gas, and any other fluid used for a thermal medium for a heater may be used as the fluid to be heated. Furthermore, as the refrigerant circulating between the evaporator 14 and the condenser 15 in the loop type heat pipe, the other operation fluid may be suitably used.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.

Claims

1. A loop type heat pipe in which a refrigerant circulates, comprising:

an evaporator located to evaporate the refrigerant by heat-exchanging with a first fluid as a heat source;

a condenser located to liquefy and condense the evaporated vapor refrigerant by heat-exchanging with a second fluid to be heated, the condenser having a refrigerant condensation side on which the condensed liquid refrigerant flows, and a refrigerant un-condensation side on which the vapor refrigerant before being condensed flows; and

a flow limitation means for flowing the second fluid from the refrigerant condensation side toward the refrigerant un-condensation side.

2. The loop type heat pipe according to claim 1, further comprising

a liquid refrigerant storage portion provided to store the condensed liquid refrigerant,

wherein the flow limitation means is provided for flowing the second fluid from a side of the liquid refrigerant storage portion toward the refrigerant un-condensation side.

3. The loop type heat pipe according to claim 2, wherein the liquid refrigerant storage portion is a part of the condenser.

4. The loop type heat pipe according to claim 1, further comprising

an operation stop means for stopping the evaporation of the refrigerant in the evaporator.

5. The loop type heat pipe according to claim 4, wherein the operation stop means is a switching valve located to open and close a passage through which the liquid refrigerant condensed in the condenser flows to the evaporator.

6. The loop type heat pipe according to claim 4, wherein the operating stop means is a flow control means for controlling a flow amount of the first fluid flowing to the evaporator.

7. The loop type heat pipe according to claim 1, wherein:

the first fluid is an exhaust gas of an engine, generated by fuel combustion in the engine;

the second fluid is a coolant used for a coolant circuit of the engine; and

the evaporator and the condenser are located to recovery waste heat from the exhaust gas.

8. The loop type heat pipe according to claim 1, wherein:

the evaporator includes a plurality of tubes in which the refrigerant flows, the tubes being arranged in parallel with each other and elongated in a first direction; and

the condenser includes a plurality of tubes arranged in parallel with each other and elongated in a second direction that is parallel with the first direction.

9. The loop type heat pipe according to claim 8, further comprising a switching valve that is located in the condenser at a lower side of the tubes of the condenser to open and close a passage through which the liquid refrigerant flows toward the evaporator.

10. The loop type heat pipe according to claim 1, wherein:

the evaporator includes a plurality of tubes arranged in parallel with each other and elongated in a first direction;

the condenser includes a plurality of tubes in which the refrigerant flows, the tubes being arranged in parallel with each other and elongated in a second direction that is perpendicular to the first direction; and

the condenser is located at an upper side of the evaporator.

11. The loop type heat pipe according to claim 10, further comprising

a switching valve that is located in the condenser at a downstream side of the tubes of the condenser in a refrigerant flow to open and close a passage through which the liquid refrigerant flows toward the evaporator.

12. A waste heat recovery device comprising:

a loop-type heat pipe including an evaporator located to evaporate a refrigerant by performing a heat exchange with a first fluid, and a condenser located to cool and condense the evaporated vapor refrigerant from the evaporator;

a first fluid flowing portion in which the first fluid flows to perform heat exchange with the refrigerant in the evaporator;

a second fluid flowing portion in which the second fluid flows to perform heat exchange with the refrigerant in the condenser;

an introducing pipe for introducing the second fluid to the second fluid flowing portion; and

a discharging pipe for discharging the second fluid from the second fluid flowing portion after passing through the second fluid flowing portion, wherein:

the condenser has a refrigerant condensation side on which the condensed liquid refrigerant flows, and a refrigerant un-condensation side on which the vapor refrigerant before being condensed flows; and

the introducing pipe is connected to the second fluid flowing portion at the refrigerant condensation side of the condenser, and the discharging pipe is connected to the second fluid flowing portion at the refrigerant un-condensation side of the condenser.

13. The waste heat recovery device according to claim 12, wherein:

the evaporator includes a plurality of tubes in which the refrigerant flows, the tubes being arranged in parallel with each other and elongated in a first direction; and

the condenser includes a plurality of tubes in which the refrigerant flows, the tubes being arranged in parallel with each other and elongated in a second direction that is parallel with the first direction.

14. The waste heat recovery device according to claim 13, further comprising a switching valve that is located in the condenser at a lower side of the tubes of the condenser to open and close a passage through which the liquid refrigerant flows toward the evaporator.

15. The waste heat recovery device according to claim 12, further comprising

a flow control means for controlling a flow amount of the first fluid flowing to the evaporator.

16. The waste heat recovery device according to claim 12, wherein:

the evaporator includes a plurality of tubes in which the refrigerant flows, the tubes being arranged in parallel with each other and elongated in a first direction;

the condenser includes a plurality of tubes in which the refrigerant flows, the tubes being arranged in parallel with each other and elongated in a second direction that is perpendicular to the first direction; and

the condenser is located at an upper side of the evaporator.

17. The waste heat recovery device according to claim 16, further comprising a switching valve that is located in the condenser at a downstream side of the tubes of the condenser in a refrigerant flow to open and close a passage through which the liquid refrigerant flows toward the evaporator.