JP2006250392A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently supply lubricant to an expander and to perform a defrosting operation capable of promoting energy saving in a refrigerating cycle device comprising a compressor and the expander. <P>SOLUTION: This refrigerating cycle device 10 comprises a refrigerant circuit 11 formed by successively connecting the compressor 1, an oil separator 9, a heat radiator 2, the expander 3 and an evaporator 5, an oil supply pipe 7 connecting the oil separator 9 and an inlet-side pipe 13 of the expander 3, and a temperature sensor 12 for detecting a refrigerant temperature of the evaporator 5. The oil supply pipe 7 passes through the evaporator 5. A controller 15 switches the operation from a normal operation to the defrosting operation when the refrigerant temperature of the evaporator 5 becomes lower than a prescribed temperature. In the defrosting operation, frost of the evaporator 5 is melted by the lubricant flowing in the evaporator 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 (see, for example, Patent Document 1). 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.
JP 2000-329416 A

  However, the conventional refrigeration cycle apparatus disclosed in Patent Document 1 does not include an evaporator defrosting unit. For this reason, there has been a problem that the performance deteriorates when frosting occurs in the evaporator.

  In general, it is conceivable to use an external heat source such as an electric heater as the defrosting means. However, when an electric heater or the like is used, the overall efficiency of the refrigeration cycle apparatus is reduced by the amount of energy input to the electric heater or the like. Therefore, it becomes difficult to promote energy saving of the apparatus.

  On the other hand, in a refrigeration cycle apparatus equipped with an expander, lubricating oil is required not only for the compressor but also for the expander. Therefore, it is necessary to always supply sufficient lubricating oil to the expander, and it is not preferable to apply the conventional so-called hot gas defrost method as it is.

  The present invention has been made in view of the above points, and an object of the present invention is to sufficiently supply lubricating oil to the expander and promote energy saving in the refrigeration cycle apparatus including the expander. It is to enable a defrosting operation that can be performed.

  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 the refrigerant circuit. A flow path opening / closing mechanism for blocking the flow of the refrigerant, an oil supply passage for supplying the lubricating oil separated by the oil separator to the expander or between the radiator and the expander in the refrigerant circuit; The oil supply passage passes through the evaporator.

  According to the refrigeration cycle apparatus, during the defrosting operation, the circulation of the refrigerant in the radiator is prevented, while the high-temperature lubricating oil stored in the oil separator flows through the oil supply passage and passes through the evaporator. As a result, the evaporator frost is melted by the heat of the lubricating oil. Therefore, the heat in the refrigerant circuit can be effectively used, and energy can be saved in the refrigeration cycle apparatus as compared with the case where defrosting is performed using an external heat source. In addition, since a sufficient amount of lubricating oil is supplied to the expander during the defrosting operation, a shortage of lubricating oil in the expander can be prevented. Furthermore, since the defrosting operation can be performed while the expander is stably operated, the high / low pressure of the refrigeration cycle does not change greatly from the normal operation, and the energy when returning from the defrosting operation to the normal operation is reduced. Can be reduced.

  The refrigeration cycle apparatus includes a temperature sensor that detects a temperature of the evaporator or a refrigerant temperature of the evaporator, and a controller that starts a defrosting operation when a detected temperature of the temperature sensor becomes a predetermined value or less. It is preferable.

  As a result, the defrosting operation can be started at an appropriate time.

  The refrigeration cycle apparatus may include a pressure sensor that detects a refrigerant pressure of the evaporator, and a controller that starts a defrosting operation when a detected pressure of the pressure sensor becomes a predetermined value or less.

  As a result, the defrosting operation can be started at an appropriate time.

  The refrigeration cycle device includes an oil amount detector that detects whether or not the amount of lubricating oil in the oil separator is equal to or less than a predetermined amount, and defrosting when the amount of lubricating oil in the oil separator becomes equal to or less than a predetermined amount during defrosting operation. And a controller for terminating the operation.

  Thus, when the lubricating oil in the oil separator is reduced during the defrosting operation, the defrosting operation is terminated. Therefore, when returning from the defrosting operation to the normal operation, insufficient supply of lubricating oil to the expander can be prevented.

  The flow path opening / closing mechanism is configured such that the opening degree can be adjusted, and the refrigeration cycle apparatus is configured so that the flow path opening / closing mechanism is not fully opened until lubricating oil is stored in the oil separator after the defrosting operation is completed. A controller for gradually increasing the opening degree of the flow path opening / closing mechanism may be provided.

  As a result, even if the lubricating oil in the oil separator is insufficient due to the defrosting operation, the return from the defrosting operation to the normal operation is performed gently, so that the lubricating oil is gradually added to the oil separator. It will be accumulated in. Therefore, when the flow path opening / closing mechanism is fully opened, a sufficient amount of lubricating oil is stored in the oil separator, and a shortage of lubricating oil in the expander can be prevented.

  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.

  Thus, the flow rate of the lubricating oil in the oil supply passage can be adjusted, and an appropriate amount of lubricating oil can always be supplied.

  In the refrigeration cycle apparatus, the refrigerant compressed by the compressor is radiated by the radiator, expanded by the expander, evaporated by the evaporator, and then sucked into the compressor during normal operation. The refrigerant in the high-pressure part from the compressor in the circuit to the expander through the radiator may be in a supercritical state.

  As described above, according to the present invention, in the refrigeration cycle apparatus including the compressor and the expander, the lubricating oil can be sufficiently supplied to the expander, and energy saving can be achieved in the defrosting operation. be able to.

  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. Between the oil separator 9 and the radiator 2, an on-off valve 18 made of an electromagnetic valve is provided. However, the on-off valve 18 may be provided between the radiator 2 and the expander 3. The position of the on-off valve 18 is not limited as long as the refrigerant flow in the radiator 2 can be prevented during the defrosting operation described later. The evaporator 5 is composed of a heat exchanger that exchanges heat between the refrigerant and the air. In the present embodiment, the evaporator 5 is configured by a plate fin tube heat exchanger. The refrigeration cycle apparatus 10 is further provided with a blower 17 that supplies air to the evaporator 5.

  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 passes through the evaporator 5. That is, the oil supply pipe 7 forms part of the path of the evaporator 5. The oil supply pipe 7 is provided with a valve 8 whose opening degree can be 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 configuration of the radiator 2 is not limited at all. For example, an air-cooled or water-cooled heat exchanger may be used as the radiator 2. The configuration of the oil separator 9 is not particularly limited.

  The evaporator 5 is provided with a temperature sensor 12. In the present embodiment, the temperature sensor 12 is arranged so as to detect the refrigerant temperature of the evaporator 5, but is arranged so as to detect the temperature of the evaporator 5 itself (for example, the surface temperature of the evaporator 5). Also good.

  The refrigeration cycle apparatus 10 is provided with a controller 15. The controller 15 is connected to the temperature sensor 12 and the on-off valve 18. The controller 15 opens and closes the on-off valve 18, but the controller 15 may be connected to the compressor 1, the valve 8, and the like to control them.

  Next, the operation of the refrigeration cycle apparatus 10 will be described. The refrigeration cycle apparatus 10 can selectively execute a normal operation in which the refrigerant is evaporated by the evaporator 5 and a defrosting operation in which the frost in the evaporator 5 is melted.

  First, normal operation will be described. During normal operation, the controller 15 opens the on-off valve 18. The refrigerant discharged from the compressor 1 is separated from the lubricating oil in the oil separator 9, then radiates heat in the radiator 2, expands in the expander 3, evaporates in the evaporator 5, and is sucked into the compressor 1. The

  On the other hand, the lubricating oil separated by the oil separator 9 flows through the oil supply pipe 7 and is cooled by the refrigerant or air in the evaporator 5, and then flows into the inlet side pipe 13 of the expander 3. The refrigerant merges with the refrigerant 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.

  When frost formation occurs in the evaporator 5 by the above-described normal operation, the refrigerant temperature of the evaporator 5 decreases. When the refrigerant temperature of the evaporator 5 becomes equal to or lower than the predetermined temperature, the controller 15 closes the on-off valve 18 and stops the operation of the blower 17 and switches the operation of the refrigeration cycle apparatus 10 from the normal operation to the defrosting operation.

  In the defrosting operation, high-temperature lubricating oil in the oil separator 9 passes through the evaporator 5, and the frost in the evaporator 5 is melted by being heated by the lubricating oil. In this defrosting operation, the flow rate of the lubricating oil can be adjusted by the valve 8.

  As described above, according to the present embodiment, since the lubricating oil in the refrigerant circuit 11 is used as a heat source for defrosting, energy saving of the refrigeration cycle apparatus 10 can be achieved. Further, since the lubricating oil is supplied to the expander 3 through the oil supply pipe 7 even during the defrosting operation, it is possible to prevent a shortage of the lubricating oil in the expander 3 during or after the defrosting operation.

  Further, since the operation is switched from the normal operation to the defrosting operation when the refrigerant temperature of the evaporator 5 becomes a predetermined temperature or less, the defrosting operation can be started at an appropriate time. Therefore, efficient defrosting is possible.

  Moreover, since the valve 8 whose opening degree can be adjusted is provided in the oil supply pipe 7, the flow rate of the lubricating oil in the oil supply pipe 7 can be controlled, and an appropriate amount of lubricating oil can always be supplied. .

(Modification)
In the above embodiment, the controller 15 starts the defrosting operation based on the refrigerant temperature of the evaporator 5. However, the controller 15 may start the defrosting operation based on the refrigerant pressure of the evaporator 5.

  That is, as shown in FIG. 2, for example, the pressure sensor 14 is provided on the inlet side or outlet side pipe of the evaporator 5, and the controller 15 defrosts from the normal operation when the detected pressure of the pressure sensor 14 becomes a predetermined pressure or less. You may make it switch a driving | operation.

  Even in such a case, the defrosting operation can be started at an appropriate time, and efficient defrosting is possible.

  The operation time of the defrosting operation is not limited at all. For example, the defrosting operation may be performed for a predetermined time. However, it is preferable that the defrosting operation time is set to such a time that the lubricating oil in the oil separator 9 is not lost during the defrosting operation. In addition, the oil separator 9 is desirably set to a capacity such that the lubricating oil does not run out during the defrosting operation.

  Switching from the defrosting operation to the normal operation may be performed based on the amount of lubricating oil stored in the oil separator 9. For example, as shown in FIG. 3, a liquid level sensor 16 may be provided in the oil separator 9, and the defrosting operation may be forcibly terminated when the oil amount in the oil separator 9 becomes a predetermined amount or less.

  Thereby, when the defrosting operation is returned to the normal operation, the lack of lubricating oil in the expander 3 can be prevented.

  Further, the opening / closing valve 18 may be configured as a valve whose opening degree can be adjusted, and the opening degree of the opening / closing valve 18 may be gradually increased after the operation is switched from the defrosting operation to the normal operation. That is, when the defrosting operation is completed, the controller 15 slowly increases the opening degree of the on-off valve 18 so that the on-off valve 18 is not fully opened until a predetermined amount of lubricating oil is stored in the oil separator 9. May be.

  As a result, since the transition from the defrosting operation to the normal operation is performed gently, even if the amount of storage in the oil separator 9 immediately after returning to the normal operation is small, the oil separator 9 thereafter The lubricating oil gradually accumulates. Therefore, when the on-off valve 18 is fully opened, a sufficient amount of lubricating oil has already been stored in the oil separator 9, and a shortage of lubricating oil in the expander 3 can be prevented.

  In the embodiment, the valve 8 is provided in the oil supply pipe 7. However, the oil supply pipe 7 may be provided with a transfer device such as an oil pump (not shown) instead of (or together with) the valve 8. Even if the pressure difference between the oil separator 9 and the inlet side pipe 13 of the expander 3 is small by providing an oil pump or the like in the oil supply pipe 7, the flow rate of the lubricating oil in the oil supply pipe 7 is reduced. 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.

  However, when 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 can 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.

  In the embodiment, 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.

  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 during normal operation, 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 refrigeration cycle apparatus according to an embodiment Refrigerant circuit diagram according to modification Refrigerant circuit diagram according to another modification

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Expander 4 Generator 5 Evaporator 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 Expander inlet side piping 14 Pressure sensor 15 Controller 16 Liquid level sensor (oil quantity detector)
18 On-off valve (channel opening / closing mechanism)

Claims (7)

A refrigerant circuit in which a compressor, an oil separator, a radiator, an expander, and an evaporator are sequentially connected;
A flow path opening / closing mechanism that is provided in the refrigerant circuit and prevents the flow of the refrigerant in the radiator during the defrosting operation;
An oil supply passage for supplying lubricating oil separated by the oil separator to the expander or between the radiator and the expander in the refrigerant circuit,
The oil supply passage is a refrigeration cycle apparatus passing through the evaporator. A temperature sensor for detecting a temperature of the evaporator or a refrigerant temperature of the evaporator;
A controller that starts a defrosting operation when the temperature detected by the temperature sensor is equal to or lower than a predetermined value;
The refrigeration cycle apparatus according to claim 1, comprising: A pressure sensor for detecting the refrigerant pressure of the evaporator;
A controller that starts the defrosting operation when the detected pressure of the pressure sensor becomes a predetermined value or less;
The refrigeration cycle apparatus according to claim 1, comprising: An oil amount detector for detecting whether or not the lubricating oil in the oil separator is below a predetermined amount;
A controller that terminates the defrosting operation when the lubricating oil in the oil separator becomes a predetermined amount or less during the defrosting operation;
The refrigeration cycle apparatus according to claim 1, comprising: The flow path opening and closing mechanism is configured to freely adjust the opening degree,
A controller for gradually increasing the opening degree of the flow path opening / closing mechanism so that the flow path opening / closing mechanism is not fully opened until lubricating oil is stored in the oil separator when the defrosting operation is completed. The refrigeration cycle apparatus according to 1.   The refrigeration cycle apparatus according to any one of claims 1 to 5, further comprising a flow rate adjusting device that adjusts a flow rate of the lubricating oil in the oil supply passage. The refrigerant compressed by the compressor is radiated by the radiator, expanded by the expander, evaporated from the evaporator, and then sucked into the compressor, during the normal operation, from the compressor in the refrigerant circuit The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein a refrigerant in a high-pressure portion that reaches the expander through the radiator is in a supercritical state.

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