JP2008133967A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To combine the sufficient supply of lubricating oil to an expander and the improvement of heating efficiency of the whole cycle in a refrigerating cycle device equipped with a compressor and the expander. <P>SOLUTION: The refrigerating cycle device 10 comprises a refrigerant circuit 11 where the compressor 1, an oil separator 9, a radiator 2, the expander 3 and an evaporator 5 are connected in this order, and an oil supply pipe 7 connecting the oil separator 9 to inlet side piping 13 of the expander 3. The oil supply pipe 7 is provided with an opening adjustable valve 8 and a cooler 6 cooling the lubricating oil by exchanging heat between a low pressure refrigerant and the lubricating oil. The inlet side piping 13 is provided with a temperature sensor 12. A controller 15 controls the opening of the valve 8 based on the inlet refrigerant temperature of the expander 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus including a compressor and an expander.

  In a so-called vapor compression refrigeration cycle apparatus, an apparatus having an expander instead of an expansion valve is known. In this type of refrigeration cycle apparatus, by using an expander, the expansion energy in the process of expansion of the refrigerant can be recovered in the form of electric power or power, and the efficiency of the cycle can be improved by the amount of the recovered energy. it can.

  In a refrigeration cycle apparatus equipped with an expander, lubricating oil is required not only for the compressor but also for the expander. In view of this, a refrigeration cycle apparatus has been proposed in which an oil separator is provided in the refrigerant circuit and the lubricating oil separated by the oil separator is supplied to the expander. For example, the following Patent Document 1 discloses a refrigeration air conditioner provided with an oil separator provided between a compressor and a radiator, and an oil feed pipe connecting the oil separator and an inlet side pipe of an expander. Is disclosed.

Since the refrigerant discharged from the compressor and the lubricating oil contained therein are hot, the lubricating oil flowing from the oil separator to the oil feed pipe also becomes hot. On the other hand, since the refrigerant that has passed through the oil separator is cooled in the radiator, the temperature is low immediately before the expander. Therefore, when the lubricating oil in the oil feed pipe merges with the refrigerant on the inlet side of the expander, the refrigerant temperature at the expander inlet rises, which leads to a decrease in the refrigerating capacity. Therefore, Patent Document 1 proposes providing a cooler in the oil feed pipe in order to lower the temperature of the lubricating oil supplied to the expander.
JP 2001-141315 A

  However, since the refrigeration air conditioner disclosed in Patent Document 1 is intended to prevent a decrease in refrigeration capacity, a separate cooling source (for example, cooling water) is indispensable in the cooler of the oil feed pipe. Met.

  In addition, heat dissipation from the lubricating oil results in energy loss, leading to a decrease in heating efficiency or heating efficiency (hereinafter simply referred to as heating efficiency) as a whole cycle.

  This invention is made | formed in view of this point, The place made into the objective is to make compatible the sufficient supply of the lubricating oil with respect to an expander, and the improvement of the heating efficiency as the whole cycle.

  The refrigeration cycle apparatus according to the present invention includes a refrigerant circuit in which a compressor, an oil separator, a radiator, an expander, and an evaporator are connected in order, and lubricating oil separated by the oil separator in the expander. Or an oil supply passage to be supplied between the radiator and the expander in the refrigerant circuit, a part of a refrigerant in a low pressure part from the expander to the compressor through the evaporator in the refrigerant circuit, and And a cooling device that cools the lubricating oil by directly or indirectly exchanging heat with the lubricating oil in the oil supply passage.

  According to the refrigeration cycle apparatus, since the lubricating oil is supplied from the oil separator to the expander through the oil supply passage, a sufficient amount of lubricating oil can be supplied to the expander. Further, since the lubricating oil in the oil supply passage is cooled by the refrigerant in the low pressure portion of the refrigerant circuit (hereinafter referred to as low pressure refrigerant), a separate cooling source is not necessary. Furthermore, since the heat radiation from the lubricating oil can be recovered, the heating efficiency of the entire cycle can be improved. Therefore, it is possible to achieve both a sufficient supply of lubricating oil to the expander and an improvement in the heating efficiency of the entire cycle.

  The cooling device may include a heat exchanger that exchanges heat between the refrigerant in the low-pressure portion of the refrigerant circuit and the lubricating oil in the oil supply passage.

  The cooling device may include a heat exchanger that exchanges heat between the air before being cooled by the evaporator or the air after being cooled by the evaporator and the lubricating oil in the oil supply passage.

  It is preferable that the refrigeration cycle apparatus includes a flow rate adjusting device that adjusts the flow rate of the lubricating oil in the oil supply passage.

  As a result, an appropriate amount of lubricating oil can always be supplied to the expander.

  The refrigeration cycle apparatus preferably includes a temperature sensor that detects a refrigerant temperature on the inlet side of the expander, and a controller that controls the flow rate adjusting device based on a temperature detected by the temperature sensor.

  Accordingly, the supply amount of the lubricating oil can be adjusted based on the refrigerant temperature on the inlet side of the expander, and sufficient supply of the lubricant oil to the expander and improvement in heating efficiency can be achieved at a high level. .

  The expander includes an expander whose operation capacity can be freely adjusted, and the refrigeration cycle apparatus includes an operation capacity detection device that detects an operation capacity of the expander, and the flow rate adjustment device based on the operation capacity of the expander. And a controller for controlling.

  Thereby, the supply amount of the lubricating oil can be adjusted based on the operating capacity of the expander, and sufficient supply of the lubricating oil to the expander and improvement in heating efficiency can be achieved at a high level.

  In the refrigeration cycle apparatus, a refrigerant in a high pressure portion from the compressor in the refrigerant circuit to the expander through the radiator may be in a supercritical state.

  As described above, according to the present invention, in a refrigeration cycle apparatus including a compressor and an expander, sufficient supply of lubricating oil to the expander and improvement in heating efficiency as a whole cycle can be achieved. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
As shown in FIG. 1, the refrigeration cycle apparatus 10 according to the first embodiment includes a refrigerant circuit 11 in which a compressor 1, an oil separator 9, a radiator 2, an expander 3, and an evaporator 5 are connected in order. I have. The refrigeration cycle apparatus 10 also includes an oil supply pipe 7 that supplies lubricating oil from the oil separator 9 to the expander 3. One end of the oil supply pipe 7 is connected to the oil separator 9, and the other end is connected to an inlet side pipe (that is, a refrigerant pipe between the radiator 2 and the expander 3) 13 of the expander 3. The oil supply pipe 7 is provided with a cooler 6 and a valve 8. The valve 8 is a valve whose opening degree can be freely adjusted.

The refrigerant charged in the refrigerant circuit 11 is a refrigerant that becomes a supercritical state in a high-pressure portion (portion from the compressor 1 through the radiator 2 to the expander 3) during operation. The refrigerant circuit 11 of the present embodiment is filled with carbon dioxide (CO ₂ ) as such a refrigerant. However, the type of refrigerant is not particularly limited.

  For the compressor 1, for example, a rotary compressor, a scroll compressor, or the like can be suitably used. However, the format of the compressor 1 is not limited at all.

  The type of the expander 3 is not limited at all. As the expander 3, for example, an expander equipped with an expansion mechanism such as a rotary type or a scroll type can be suitably used.

  A power generator 4 is connected to the expander 3. The generator 4 converts the expansion energy of the refrigerant recovered by the expander 3 into electric energy. In FIG. 1, the generator 4 and the expander 3 are illustrated separately, but the generator 4 may be built in the expander 3. Of course, the generator 4 and the expander 3 may be formed separately.

  The configurations of the radiator 2 and the evaporator 5 are not limited at all. For example, an air-cooled or water-cooled heat exchanger may be used as the radiator 2 or the evaporator 5. The configuration of the oil separator 9 is not particularly limited.

  The cooler 6 is a so-called liquid-liquid heat exchanger, and directly exchanges heat between the lubricating oil in the oil supply pipe 7 and the low-pressure refrigerant between the expander 3 and the evaporator 5. For the cooler 6, for example, a double tube heat exchanger, a plate heat exchanger, a shell and tube heat exchanger, or the like can be suitably used. Further, the cooler 6 can also be configured by joining the oil supply pipe 7 and the refrigerant pipe without using a dedicated heat exchanger.

  When a double tube heat exchanger having an inner flow path and an outer flow path is used as the cooler 6, a coolant may flow through the inner flow path and lubricating oil may flow through the outer flow path. This can suppress an increase in the pressure loss of the low-pressure refrigerant. Conversely, it is possible to flow lubricating oil in the inner flow path and flow refrigerant in the outer flow path. In this case, the pressure loss of the lubricating oil is reduced, and a sufficient flow rate of the lubricating oil can be ensured. In addition, it is preferable that the cooler 6 is a so-called counter flow type heat exchanger that allows the refrigerant and the lubricating oil to flow in a facing state.

  The inlet side pipe 13 of the expander 3 is provided with a temperature sensor 12 that detects the refrigerant temperature. The temperature sensor 12 may be any sensor that substantially detects the refrigerant temperature. Therefore, the temperature sensor 12 may directly detect the refrigerant temperature in the inlet side pipe 13 or indirectly detect the refrigerant temperature by detecting the wall surface temperature of the inlet side pipe 13 or the like. May be. Moreover, the temperature sensor 12 should just detect the inlet refrigerant temperature of the expander 3, and may be provided in the expander 3 itself.

  The refrigeration cycle apparatus 10 is provided with a controller 15. The controller 15 receives the detection signal of the temperature sensor 12 and controls the opening degree of the valve 8. Of course, the controller 15 does not have to be a dedicated controller provided for controlling the valve 8 and may control the compressor 1 and the like.

  Next, the operation of the refrigeration cycle apparatus 10 will be described. In the refrigerant circuit 11, the refrigerant discharged from the compressor 1 is separated from the lubricating oil in the oil separator 9, and then radiates heat in the radiator 2, expands in the expander 3, and becomes a low-temperature and low-pressure refrigerant. The low-temperature and low-pressure refrigerant is heated by the cooler 6 at the same time as the lubricating oil is cooled. At this time, part of the refrigerant may or may not evaporate. The refrigerant heated by the cooler 6 evaporates by the evaporator 5 and is then sucked into the compressor 1.

  On the other hand, the lubricating oil separated by the oil separator 9 flows through the oil supply pipe 7 and is cooled by exchanging heat with the refrigerant in the cooler 6. Then, the cooled lubricating oil flows into the inlet side pipe 13 of the expander 3, merges with the refrigerant from the radiator 2, and flows into the expander 3. Thereby, lubricating oil is supplied to the expander 3. The flow rate of the lubricating oil is adjusted by the valve 8.

  The controller 15 controls the opening degree of the valve 8 based on the inlet refrigerant temperature of the expander 3. For example, the controller 15 may adjust the inflow amount of the lubricating oil so that the internal temperature of the expander 3 does not increase or decrease too much. In this embodiment, the controller 15 controls the opening degree of the valve 8 so that the inlet refrigerant temperature becomes a predetermined value. For example, the controller 15 decreases the opening degree of the valve 8 when the inlet refrigerant temperature of the expander 3 is equal to or higher than a predetermined value, and increases the opening degree of the valve 8 when the inlet refrigerant temperature is lower than the predetermined value.

  As described above, according to the present embodiment, the refrigerant and the lubricating oil are separated by the oil separator 9 and the lubricating oil is supplied to the expander 3 through the oil supply pipe 7. And a sufficient amount of lubricating oil can be supplied. In addition, since the lubricating oil in the oil supply pipe 7 is cooled by the low-pressure refrigerant in the refrigerant circuit 11, it is not necessary to separately provide a cooling source. Moreover, the heat radiation from the lubricating oil can be recovered in the refrigerant circuit 11, and the heating efficiency of the entire cycle can be improved. Therefore, it is possible to achieve both the sufficient supply of the lubricating oil to the expander 3 and the improvement of the heating efficiency of the entire cycle.

  That is, in the present refrigeration cycle apparatus 10, by heating the low-pressure refrigerant with lubricating oil, the pressure in the low-pressure part of the refrigerant circuit 11 (hereinafter referred to as the low-pressure side pressure) can be increased, and the load on the compressor 1 is reduced. can do. Therefore, the heating COP of the refrigeration cycle can be improved. Moreover, since a refrigerant | coolant is heated in the cooler 6, the required amount of heating in the evaporator 5 can be reduced. Therefore, the evaporator 5 can be downsized.

  Further, according to the present embodiment, since the oil supply pipe 7 is provided with the valve 8 whose opening degree can be adjusted, the supply amount of the lubricating oil to the expander 3 can be freely adjusted. Moreover, the refrigerant temperature before expansion can be controlled by adjusting the opening degree of the valve 8 based on the inlet refrigerant temperature of the expander 3. Therefore, it is possible to suppress a decrease in lubricating oil viscosity due to a decrease in refrigerant temperature before expansion and a decrease in evaporator capacity due to an increase in refrigerant temperature before expansion. If the lubricating oil viscosity decreases, the sliding loss in the expander 3 increases, and the reliability and performance of the expander 3 decrease. Moreover, if evaporator capacity falls, evaporator pressure will fall and the load of the compressor 1 will increase. Therefore, the heating efficiency of the refrigeration cycle apparatus 10 can be improved while ensuring the reliability of the expander 3 regardless of fluctuations in the operating state.

  The refrigerant after being separated from the lubricating oil by the oil separator 9 flows through the radiator 2. Therefore, since lubricating oil can be prevented or suppressed from flowing into the radiator 2, the heat transfer coefficient on the refrigerant side of the radiator 2 can be increased, and the performance of the radiator 2 can be improved. Therefore, the heating efficiency can be further improved.

(Modification)
In the above embodiment, the controller 15 controls the opening degree of the valve 8 based on the inlet refrigerant temperature of the expander 3. However, the control executed by the controller 15 is not limited to the above control. For example, as shown in FIG. 2, a rotation speed detection sensor 14 that detects the rotation speed of the expander 3 may be provided, and the opening degree of the valve 8 may be controlled based on the rotation speed of the expander 3. For example, the controller 15 increases the opening degree of the valve 8 when the rotational speed of the expander 3 is greater than or equal to a predetermined value, and decreases the opening degree of the valve 8 when the rotational speed is less than the predetermined value. As a result, a sufficient amount of lubricating oil can always be supplied in accordance with the rotational speed, and the cycle efficiency can be improved.

  Note that controlling the rotational speed of the expander 3 means controlling the operating capacity of the expander 3. Here, the method of controlling the operating capacity of the expander 3 is not limited to the method of controlling the rotational speed. For example, when the expander 3 includes a plurality of expansion mechanisms that are parallel to each other, the overall operating capacity of the expander 3 can be controlled by adjusting the number of operating the plurality of expansion mechanisms. The expander 3 may be composed of a plurality of expanders connected in parallel to each other. In this case as well, the overall operating capacity of the expander 3 can be controlled by adjusting the number of expander units.

(Second Embodiment)
As shown in FIG. 3, in the second embodiment, a change is made to the cooler 6 of the oil supply pipe 7 in the refrigeration cycle apparatus 10 of the first embodiment.

  The cooler 6 according to this embodiment also cools the lubricating oil in the oil supply pipe 7 using the low-pressure refrigerant in the refrigerant circuit 11. However, this embodiment differs from the first embodiment in that the cooler 6 is configured to indirectly exchange heat between the lubricating oil and the low-pressure refrigerant. Specifically, the evaporator 5 of the present embodiment includes a so-called air heat exchanger that exchanges heat between air and a refrigerant, and the cooler 6 is air before being cooled by the evaporator 5 or after being cooled. And an air heat exchanger for exchanging heat with the lubricating oil. In the refrigeration cycle apparatus 10 of the present embodiment, a blower 17 common to the evaporator 5 and the cooler 6 is provided. However, it goes without saying that a blower may be provided for each of the evaporator 5 and the cooler 6.

  Since other configurations are the same as those of the first embodiment, description thereof will be omitted.

  Therefore, also in this embodiment, the same effect as that of the first embodiment can be obtained.

(Third embodiment)
As shown in FIG. 4, the third embodiment is also a modification of the cooler 6 of the oil supply pipe 7 in the refrigeration cycle apparatus 10 of the first embodiment. In the present embodiment, the cooler 6 is integrated with the evaporator 5. Specifically, the oil supply pipe 7 passes through the evaporator 5, and in the evaporator 5, the lubricating oil and the refrigerant (or the air before being cooled by the refrigerant or the air after being cooled) exchange heat. I do. Other configurations are the same as those of the first embodiment. In FIG. 4, the temperature sensor 12 and the controller 15 are not shown.

  Therefore, also in this embodiment, the same effect as that of the first embodiment can be obtained.

(Fourth embodiment)
In the first to third embodiments, the oil supply pipe 7 is provided with the valve 8. However, as shown in FIG. 5, the oil supply pipe 7 may be provided with an oil pump 8 a instead of the valve 8 (or together with the valve 8). The controller 15 may control the oil pump 8a based on the inlet refrigerant temperature or the operating capacity of the expander 3.

  By providing the oil pump 8 a in the oil supply pipe 7, the flow rate of the lubricating oil in the oil supply pipe 7 can be reduced even when the pressure difference between the oil separator 9 and the inlet side pipe 13 of the expander 3 is small. Can do a lot. Therefore, a sufficient amount of lubricating oil can always be supplied to the expander 3. Moreover, it becomes possible to control the flow rate of the lubricating oil widely.

(Other embodiments)
In each of the above embodiments, the downstream end of the oil supply pipe 7 is connected to the inlet side pipe 13 of the expander 3. However, the oil supply pipe 7 only needs to supply lubricating oil to the expander 3, and the downstream end of the oil supply pipe 7 may be connected to the expander 3 itself.

  If it is not necessary to control the flow rate of the lubricating oil in the oil supply pipe 7, a throttle mechanism such as a capillary tube may be provided instead of the valve 8 whose opening degree can be adjusted. If the pressure loss in the oil supply pipe 7 is in an appropriate range (a range in which an appropriate amount of lubricating oil can be supplied to the expander 3), the valve 8 can be omitted.

  The type of the oil supply pipe 7 is not limited at all. The oil supply pipe 7 may be formed of a flexible pipe so that the oil supply pipe 7 is not easily damaged by vibration of the compressor 1 or the expander 3. Further, the length and shape of the oil supply pipe 7 are not limited at all. However, from the viewpoint of reducing the pressure loss of the oil supply pipe 7, the length of the oil supply pipe 7 is preferably short, and is preferably a straight pipe.

  The refrigerant charged in the refrigerant circuit 11 is not limited to a refrigerant that is in a supercritical state in the high-pressure portion of the refrigerant circuit 11, and may be a refrigerant that does not enter a supercritical state in the high-pressure portion.

  As described above, the present invention is useful for a refrigeration cycle apparatus including a compressor and an expander.

Refrigerant circuit diagram of the refrigeration cycle apparatus according to the first embodiment Refrigerant circuit diagram according to a modification of the first embodiment Refrigerant circuit diagram of refrigeration cycle apparatus according to the second embodiment Refrigerant circuit diagram of refrigeration cycle apparatus according to the third embodiment Refrigerant circuit diagram of refrigeration cycle apparatus according to the fourth embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Expander 4 Generator 5 Evaporator 6 Cooler (cooling device, heat exchanger)
7 Oil supply pipe (oil supply passage)
8 valves (flow control device)
DESCRIPTION OF SYMBOLS 9 Oil separator 10 Refrigeration cycle apparatus 11 Refrigerant circuit 12 Temperature sensor 13 Inlet side piping 14 Rotation speed detection sensor (operation capacity detection apparatus)
15 Controller

Claims (7)

A refrigerant circuit in which a compressor, an oil separator, a radiator, an expander, and an evaporator are sequentially connected;
An oil supply passage for supplying the lubricant separated by the oil separator to the expander or between the radiator and the expander in the refrigerant circuit;
The lubricating oil is cooled by directly or indirectly heat-exchanging a part of the refrigerant in the low-pressure portion from the expander to the compressor through the evaporator in the refrigerant circuit and the lubricating oil in the oil supply passage. A cooling device to
A refrigeration cycle apparatus comprising:   The refrigeration cycle apparatus according to claim 1, wherein the cooling device includes a heat exchanger that exchanges heat between a refrigerant in a low-pressure portion of the refrigerant circuit and lubricating oil in the oil supply passage.   The cooling device includes a heat exchanger for exchanging heat between air before being cooled by the evaporator or air after being cooled by the evaporator and lubricating oil in the oil supply passage. The refrigeration cycle apparatus described in 1.   The refrigeration cycle apparatus according to any one of claims 1 to 3, further comprising a flow rate adjusting device that adjusts a flow rate of the lubricating oil in the oil supply passage. A temperature sensor for detecting a refrigerant temperature on the inlet side of the expander;
A controller for controlling the flow rate adjusting device based on a temperature detected by the temperature sensor;
The refrigeration cycle apparatus according to claim 4, comprising: The expander is an expander whose operation capacity can be freely adjusted,
An operating capacity detection device for detecting the operating capacity of the expander;
A controller for controlling the flow rate adjusting device based on the operating capacity of the expander;
The refrigeration cycle apparatus according to claim 4, comprising: The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein a refrigerant in a high-pressure portion from the compressor to the expander through the radiator in the refrigerant circuit is in a supercritical state.

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