JP2008032295A - Refrigeration apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent oil choke in an expansion valve. <P>SOLUTION: In this refrigeration apparatus provided with a refrigerant circulating route constituted by connecting a compressor 1, a condenser 2, the expansion valve 4 and an evaporator 5 by a closed loop, a pressure reducing means 3a for reducing a pressure of the refrigerant radiating heat at the condenser 2, to a two-phase region G of a gas-liquid mixing state, is disposed between the condenser 2 and the expansion valve 4, and the refrigerant is kept in the gas-liquid mixing state at an input portion of the expansion valve 4, thus a gas component is included, a density is reduced, and a flow velocity is increased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigerating apparatus in which refrigerating machine oil (oil) circulates with a refrigerant in a refrigerant circulation path formed by coupling a compressor, a condenser, an expansion valve, and an evaporator in a closed loop. The present invention relates to a refrigeration apparatus that can prevent oil choke (clogging of refrigerator oil).

  A refrigerating apparatus in which a refrigerant circulation path is configured by connecting a compressor, a condenser, an expansion valve whose opening is adjustable, and an evaporator in a closed loop is generally known.

  As the refrigerant, HFC refrigerant (hydrofluorocarbon) is generally used. However, from the viewpoint of protecting the global environment, the development of a refrigerant that has less influence on the global environment is required. Therefore, recently, development of a refrigeration apparatus using carbon dioxide as a refrigerant, which is nonflammable, safe, non-corrosive, has little influence on the ozone layer, and does not adversely affect the human body, has been promoted.

  By the way, in the refrigeration apparatus using Freon, the high temperature side pressure is operated at about 1 to 2 MPa, whereas in the case of a refrigeration apparatus using carbon dioxide as a refrigerant, the high temperature side pressure is about even during stable operation. 10 MPa or more. For this reason, a special expansion valve with a high-pressure specification is required. Therefore, a pressure reducing means consisting of a capillary tube is interposed between the condenser in the refrigerant circulation path and the expansion valve, and the pressure of the refrigerant is reduced in two stages, thereby reducing the pressure resistance required for the expansion valve itself. In order to make it possible to use a general-purpose expansion valve, it has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-14024 (FIG. 1)

  By the way, the compressor used for the refrigerating apparatus compresses the refrigerant by using a refrigerating machine oil having a predetermined viscosity. This refrigerating machine oil plays a role in preventing wear inside the compressor, leakage of refrigerant, and the like. For example, the refrigerating machine oil used in the reciprocating compressor prevents the cylinder from being worn, and prevents the refrigerant from leaking by closing the gap between the cylinder and the piston. However, refrigeration oil is difficult to completely seal inside the compressor due to the structure of the compressor, and slightly flows out from the compressor into the refrigerant circulation path and circulates in the refrigerant circulation path. . That is, in the refrigerant circulation path, the refrigerant and the refrigeration oil are circulated in a mixed state. Moreover, the following is understood about the relationship between a refrigerant | coolant (for example, carbon dioxide) and refrigeration oil.

  That is, under the condition where the temperature is constant, the carbon dioxide mixing ratio indicating the ratio of the weight of carbon dioxide dissolved in the refrigerating machine oil (unit volume) increases as the pressure increases. Furthermore, under the condition where the pressure is constant, the carbon dioxide mixing ratio increases as the temperature decreases. That is, as the pressure increases and the temperature decreases, carbon dioxide has a characteristic of becoming more easily dissolved in the refrigerating machine oil.

  On the other hand, when the temperature is constant, the viscosity of the refrigerating machine oil increases as the carbon dioxide mixing rate decreases. Furthermore, under the condition where the carbon dioxide mixing ratio is constant, the viscosity of the refrigerating machine oil increases as the temperature decreases. That is, as the carbon dioxide mixing ratio decreases and the temperature decreases, the refrigeration oil has a characteristic that it becomes sticky.

  For this reason, when the flow rate at the input part of the expansion valve becomes low or the temperature becomes low at low flow rates by reducing the opening of the expansion valve, the viscosity of the oil increases and an oil choke (of the refrigerating machine oil) Clogging) occurs. When the oil choke is generated, the circulation amount of the refrigerant composed of carbon dioxide becomes extremely small, the pressure on the high pressure side of the expansion valve is increased, and the protection circuit of the compressor is activated.

  Also, in a refrigeration system that uses carbon dioxide as a refrigerant, the pressure in the refrigerant circulation path increases both on the high-pressure side and the low-pressure side compared to the case where HFC refrigerant is used, and the internal load (friction, etc.) of the compressor increases. This increases the possibility of damaging the compressor itself. Moreover, in the process of transition from high pressure to low pressure, the refrigerant undergoes a phase change to a supercritical, liquid, gas-liquid two-phase state. For this reason, as the refrigerating machine oil of this compressor, one having a higher viscosity than the refrigerating machine oil in the case of the HFC refrigerant is used. That is, the refrigerating machine oil circulating in the refrigerant circulation path of the refrigeration apparatus using carbon dioxide as a refrigerant is very likely to be clogged with the expansion valve at a low temperature.

  The problem of the oil choke in such an expansion valve is that the pressure of the refrigerant is simply set by interposing a pressure reducing means comprising a capillary tube between the condenser and the expansion valve in the refrigerant circulation path as in the above-described conventional example. It cannot be solved simply by reducing the pressure in two stages. According to the experiments by the present inventors, when the pressure reducing means (capillary tube) is arranged upstream of the expansion valve as in the above-described conventional example, the refrigerant after pressure reduction by the first stage pressure reducing means (capillary tube). It has been found that the properties and temperature of the oil have important implications for oil chokes. In other words, even when a pressure reducing means (capillary tube) is arranged upstream of the expansion valve and the two-stage pressure reduction is performed, if the property of the refrigerant after the first pressure reduction is only in the liquid phase, the expansion valve It has been found that oil choke is generated when the flow velocity at the input section decreases or when the temperature becomes low. In order to solve this problem, the pressure of the refrigerant is reduced to a region of two phases (gas-liquid mixing) with a capillary tube as a first-stage pressure reducing means, the gas component is included, the density is reduced, If the pressure reducing means (capillary tube) is placed downstream of the expansion valve and the pressure is reduced in two stages, the temperature immediately after the expansion valve can be raised and the viscosity of the refrigerating machine oil can be kept low. Therefore, an undiscovered physical phenomenon has been discovered that oil choke does not occur even if the first stage expansion valve does not necessarily reduce the pressure of the refrigerant to a region that is in two phases (gas-liquid mixing).

  An object of the present invention is to obtain a refrigeration apparatus capable of preventing oil choke in an expansion valve in view of the above points and the above knowledge.

  (1) The refrigeration apparatus according to the present invention has the following configuration. That is, in a refrigeration apparatus in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a closed loop to form a refrigerant circulation path, the refrigerant radiated by the condenser between the condenser and the expansion valve Is provided with a pressure reducing means for reducing the pressure to a two-phase region where a gas-liquid mixed state is achieved.

  (2) The refrigeration apparatus according to the present invention has the following configuration. That is, in a refrigeration system in which a refrigerant circulation path is configured by connecting a compressor, a condenser, an expansion valve, and an evaporator in a closed loop, the pressure is reduced by adiabatic expansion at the expansion valve between the expansion valve and the evaporator. A pressure reducing means for reducing the pressure of the refrigerant further by adiabatic expansion to the evaporation temperature of the evaporator is provided.

  (3) The refrigeration apparatus according to the present invention has the following configuration. That is, in a refrigeration apparatus in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a closed loop to form a refrigerant circulation path, the refrigerant radiated by the condenser between the condenser and the expansion valve The first pressure reducing means for reducing the pressure of the gas to the two-phase region where the gas-liquid mixture is brought about is provided, and the first pressure reducing means and the expansion valve are adiabatically expanded in two stages between the expansion valve and the evaporator. A second depressurizing means for depressurizing the pressure of the depressurized refrigerant to the evaporation temperature of the evaporator by adiabatic expansion is provided.

  (4) In the refrigeration apparatus according to the present invention, the decompression means is constituted by a capillary tube or an orifice.

  (5) The refrigeration apparatus according to the present invention uses carbon dioxide as a refrigerant.

  In the cooling device of the present invention, the decompression means for lowering the viscosity of the refrigerating machine oil is arranged before, after, or before and after the expansion valve, so that the viscosity of the refrigerating machine oil does not increase and the flow rate of the refrigerant And the oil choke at the expansion valve can be prevented.

  Further, by using a capillary tube or an orifice as the decompression means, the structure can be simplified and the cost can be reduced.

  Further, by using carbon dioxide as a refrigerant, it is easy to ensure safety without adversely affecting the global environment and the human body.

Embodiment 1 FIG.
FIG. 1 is a Mollier diagram (PH diagram) showing the operation of the refrigeration apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a configuration diagram of the refrigeration circuit (refrigerant circulation path).

  As shown in FIG. 2, the refrigeration apparatus of the present embodiment is a refrigeration circuit in which a compressor 1, a condenser 2, an expansion valve 4 with adjustable opening, and an evaporator 5 are coupled in a closed loop and carbon dioxide is used as a refrigerant. In the (refrigerant circulation path), between the condenser 2 and the expansion valve 4 (upstream of the expansion valve 4), the two-phase region where the pressure of the refrigerant radiated by the condenser 2 is changed from a liquid to a gas-liquid mixed state. A pressure reducing means, that is, a capillary tube 3a for reducing the pressure to (the filled G region in FIG. 1) is provided.

  In the refrigeration apparatus of the present embodiment, the refrigerant discharged from the compressor 1 is circulated sequentially to the condenser 2, the capillary tube 3a, the expansion valve 4 and the evaporator 5 as indicated by arrows in FIG. Is configured.

  The lines indicated by A, B, C, D, and E in FIG. 1 indicate the paths that the refrigerant follows. A to B are strokes in which the compressor 1 compresses the refrigerant, and B to C are the refrigerant by the condenser 2. , C to D to E are steps in which pressure is reduced in two stages by adiabatic expansion, and E to A are steps in which the refrigerant absorbs heat energy by the evaporator 5. D in the middle of C to E is the pressure in the two-phase region G where the refrigerant is in a gas-liquid mixed state, and E is the evaporation temperature of the evaporator 5 (hereinafter referred to as “evaporation temperature”). Up to ~ D, the pressure is reduced by the capillary tube 3a, and up to D ~ E is reduced by the expansion valve 4.

  As described above, the refrigeration apparatus of the present embodiment is provided with the capillary tube 3a on the upstream side of the expansion valve 4 for reducing the pressure of the refrigerant radiated by the condenser 2 to the two-phase region G where the gas-liquid mixed state is established. Therefore, the refrigerant is in a gas-liquid mixed state at the input portion of the expansion valve 4. And in this gas-liquid mixed state, since there is a quality (dryness) of the refrigerant, a gas component is contained, the density is reduced, and the flow rate is increased. For this reason, even if refrigeration oil having a high viscosity is mixed, it can be pushed out and allowed to flow without clogging, and oil choking at the expansion valve 4 can be prevented.

Embodiment 2. FIG.
FIG. 3 is a Mollier diagram (PH diagram) illustrating the operation of the refrigeration apparatus according to Embodiment 2 of the present invention, and FIG. 4 is a configuration diagram of the refrigeration circuit (refrigerant circulation path). The same parts as those in the first embodiment are denoted by the same reference numerals.

  As shown in FIG. 4, the refrigeration apparatus of the present embodiment is a refrigeration circuit in which a compressor 1, a condenser 2, an expansion valve 4 with adjustable opening, and an evaporator 5 are coupled in a closed loop and carbon dioxide is used as a refrigerant. In the (refrigerant circulation path), between the expansion valve 4 and the evaporator 5 (on the downstream side of the expansion valve 4), the pressure of the refrigerant depressurized by the adiabatic expansion by the expansion valve 4 is further increased. This is different from that of the first embodiment described above in that a pressure reducing means for reducing pressure by adiabatic expansion, that is, a capillary tube 3b is provided. Other configurations are the same as those of the first embodiment.

  In the refrigeration apparatus of the present embodiment, the lines indicated by A, B, C, D, and E in FIG. 3 indicate the paths that the refrigerant follows, and A to B are steps in which the compressor 1 compresses the refrigerant, B C is a process in which the refrigerant releases thermal energy by the condenser 2, C C to D are processes in which the pressure is reduced in two stages by adiabatic expansion, and E to A are processes in which the refrigerant absorbs the heat energy by the evaporator 5. . D in the middle between C and E is the pressure in the two-phase region G where the refrigerant is in a gas-liquid mixed state, E is the evaporator temperature of the evaporator 5, and here, the pressure is reduced by the expansion valve 4 until C to D, From D to E, the pressure is reduced by the capillary tube 3a.

  As described above, in the refrigeration apparatus of the present embodiment, the capillary tube 3b that lowers the refrigerant expanded by the expansion valve 4 to the required evaporation temperature is provided on the downstream side of the expansion valve 4. The state can be raised to point D. For this reason, the temperature immediately after the expansion valve 4 can be raised, the viscosity of the refrigerating machine oil can be kept low, and oil choke at the expansion valve 4 can be prevented.

  In this example, the expansion valve 4 is used to reduce the pressure of the refrigerant to the region G that is in two phases (gas-liquid mixture). However, as described above, the refrigerant after the expansion valve 4 is used. Since the temperature immediately after the expansion valve 4 is raised by the capillary tube 3b so as to increase the temperature immediately after the expansion valve 4, the viscosity of the refrigerating machine oil can be kept low. The refrigerant does not have to be depressurized to the two-phase region G, and can be set higher than that.

Embodiment 3 FIG.
FIG. 5 is a Mollier diagram (PH diagram) illustrating the operation of the refrigeration apparatus according to Embodiment 3 of the present invention, and FIG. 6 is a configuration diagram of the refrigeration circuit (refrigerant circulation path). The same parts as those in the first and second embodiments are denoted by the same reference numerals.

  As shown in FIG. 6, the refrigeration apparatus of the present embodiment is a refrigeration circuit in which a compressor 1, a condenser 2, an expansion valve 4 with adjustable opening, and an evaporator 5 are coupled in a closed loop and carbon dioxide is used as a refrigerant. In the (refrigerant circulation path), between the condenser 2 and the expansion valve 4 (upstream side of the expansion valve 4), the pressure of the refrigerant radiated by the condenser 2 reaches the two-phase region G where the gas-liquid mixed state is achieved. A first pressure reducing means for reducing the pressure, that is, the capillary tube 3a is provided, and between the expansion valve 4 and the evaporator 5 (on the downstream side of the expansion valve 4), the capillary tube 3a and the expansion valve 4 are adiabatically expanded in two stages. The second pressure reducing means, that is, the capillary tube 3b for reducing the pressure of the decompressed refrigerant further by adiabatic expansion to the evaporation temperature of the evaporator 5, is provided. The function of the first embodiment and the above-described implementation are provided. Point that has the function of Form 2 It has a feature.

  In the refrigeration apparatus of the present embodiment, the lines indicated by A, B, C, D, F, and E in FIG. 5 indicate the paths that the refrigerant follows, and A to B are steps in which the compressor 1 compresses the refrigerant. B to C are processes in which the refrigerant releases heat energy by the condenser 2, C to D to F to E are processes in which the pressure is reduced in three stages by adiabatic expansion, and E to A are the processes in which the refrigerant absorbs the heat energy by the evaporator 5. It is the process to do. D in the middle between C and E is the pressure in the two-phase region G where the refrigerant is in a gas-liquid mixed state, F is the pressure lower than D in the two-phase region G, E is the evaporator temperature of the evaporator 5, Here, the pressure from C to D is reduced by the capillary tube 3a, the pressure from D to F is reduced by the expansion valve 4, and the pressure from F to E is reduced by the capillary tube 3b.

  As described above, in the refrigeration apparatus of the present embodiment, the capillary tube 3a for reducing the pressure of the refrigerant radiated by the condenser 2 to the two-phase region G in a gas-liquid mixed state is provided upstream of the expansion valve 4. The capillary tube 3b is provided downstream of the expansion valve 4 and the pressure of the refrigerant depressurized in two stages by the adiabatic expansion by the capillary tube 3a and the expansion valve 4 is further reduced by the adiabatic expansion to the evaporation temperature of the evaporator 5. Thus, the same effects as those of the first and second embodiments are obtained, and the oil choke in the expansion valve 4 can be reliably prevented by the synergistic effect thereof. That is, gas components are always included in the input portion of the expansion valve 4, the density is reduced, the flow rate is increased, and even if refrigeration oil with increased viscosity is mixed, it is pushed out and flows so as not to be clogged. I can do it. Further, the state immediately after the expansion valve 4 can be raised to the point F, the temperature immediately after the expansion valve 4 can be raised, the viscosity of the refrigerating machine oil can be kept low, and the oil choke in the expansion valve 4 Can be prevented.

  In each of the above-described embodiments, the example using the capillary tube as the pressure reducing means has been described as an example, but an orifice can be used instead. In either case, the structure can be simplified and the cost can be reduced.

It is a Mollier diagram which shows operation | movement of the freezing apparatus which concerns on Embodiment 1 of this invention. It is a block diagram of the freezing circuit of the freezing apparatus which concerns on Embodiment 1 of this invention. It is a Mollier diagram which shows operation | movement of the freezing apparatus which concerns on Embodiment 2 of this invention. It is a block diagram of the freezing circuit of the freezing apparatus which concerns on Embodiment 2 of this invention. It is a Mollier diagram which shows operation | movement of the freezing apparatus which concerns on Embodiment 3 of this invention. It is a block diagram of the freezing circuit of the freezing apparatus which concerns on Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3a, 3b Capillary tube (pressure reduction means)
4 Expansion valve 5 Evaporator

Claims (5)

In a refrigeration apparatus in which a compressor, a condenser, an expansion valve, and an evaporator are coupled in a closed loop to form a refrigerant circulation path.
A refrigeration apparatus comprising a decompression means for reducing the pressure of the refrigerant radiated by the condenser to a two-phase region in a gas-liquid mixed state between the condenser and the expansion valve. In a refrigeration apparatus in which a compressor, a condenser, an expansion valve, and an evaporator are coupled in a closed loop to form a refrigerant circulation path.
A pressure reducing means is provided between the expansion valve and the evaporator to further reduce the pressure of the refrigerant depressurized by adiabatic expansion by the expansion valve to the evaporation temperature of the evaporator by adiabatic expansion. Refrigeration equipment. In a refrigeration apparatus in which a compressor, a condenser, an expansion valve, and an evaporator are coupled in a closed loop to form a refrigerant circulation path.
Between the condenser and the expansion valve, there is provided a first decompression means for decompressing the pressure of the refrigerant radiated by the condenser to a two-phase region that is in a gas-liquid mixed state,
Between the expansion valve and the evaporator, the pressure of the refrigerant depressurized in two stages by adiabatic expansion by the first depressurization means and the expansion valve is further reduced by adiabatic expansion to the evaporation temperature of the evaporator. A refrigeration apparatus provided with a second decompression means.   The refrigeration apparatus according to any one of claims 1 to 3, wherein the decompression means is constituted by a capillary tube or an orifice. The refrigeration apparatus according to any one of claims 1 to 4, wherein the refrigerant is carbon dioxide.

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