JP2010032159A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain stable operation from a low temperature area to a high temperature area. <P>SOLUTION: A refrigerating cycle device 10 circulates a mixed refrigerant in which a plurality of component refrigerants are mixed. An expansion valve 40 is equipped with a power element 42. An enclosed refrigerant enclosed in the power element 42 includes one component refrigerant of the plurality of component refrigerants. Inclination of a saturated vapor pressure curve SV1 of the component refrigerant is larger than that of a saturated vapor pressure curve SV0 of the mixed refrigerant. As a result, the enclosed refrigerant also shows inclination larger than that of the mixed refrigerant. This characteristic can avoid an excessive opening of the expansion valve in the low-temperature area and can provide a suitable opening for load in the high temperature area, which can provide the stable operation from the low temperature area to the high temperature area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus.

  Conventionally, a refrigeration cycle apparatus described in Patent Document 1 is known. The refrigeration cycle apparatus includes a compressor, a condenser, an expansion valve, and an evaporator, and is configured by connecting them in a ring shape. The refrigeration cycle apparatus further includes an internal heat exchanger that exchanges heat between the high-pressure refrigerant between the condenser and the expansion valve and the low-pressure refrigerant between the evaporator and the compressor. The circulating refrigerant circulating through the refrigeration cycle apparatus is a single refrigerant or a mixed refrigerant. A temperature-sensitive expansion valve is widely used as an expansion valve.

  Patent Document 2 discloses a refrigeration cycle apparatus using a mixed refrigerant and a temperature-sensitive expansion valve. Further, Patent Document 2 also discloses that the same refrigerant as the circulating refrigerant or a refrigerant exhibiting pressure-temperature characteristics similar to the circulating refrigerant is enclosed in the temperature sensing part of the expansion valve. The refrigerant enclosed in the temperature sensing part is called an enclosed refrigerant.

On the other hand, various forms are known as a temperature-sensitive expansion valve. For example, patent document 2 is disclosing the joint type expansion valve provided with the joint part for connecting with piping which comprises a refrigeration cycle apparatus. Patent document 3 is disclosing the box-type expansion valve provided with the housing which formed the high pressure channel | path and the low pressure channel | path. Patent Document 4 discloses a cassette structure in which a temperature sensing part and a valve part are unitized. Furthermore, Patent Document 2 discloses an inner-equal expansion valve that introduces pressure between the expansion valve and the evaporator. Patent Document 4 discloses an outer-equal expansion valve that introduces pressure between the evaporator and the compressor.
JP 2007-71461 A JP-A-2-203175 Patent No. 4039069 No. 7-40139

  A conventional temperature-sensitive expansion valve controls the refrigerant state at the outlet of the evaporator. For example, the temperature-sensitive expansion valve controls the degree of superheat of the circulating refrigerant at the outlet of the evaporator to a predetermined value.

  However, when mixed refrigerant is used as the circulating refrigerant, the pressure difference between the saturated vapor pressure curve of the circulating refrigerant and the valve opening characteristic depending on the saturated vapor pressure curve of the enclosed refrigerant is undesirably reduced or increased in the low temperature region or the high temperature region. Was sometimes shown. Such behavior is prominent when the enclosed refrigerant and the circulating refrigerant are different. For this reason, there is a problem that desired control characteristics cannot be obtained in a low temperature region or a high temperature region.

  For example, when the pressure difference between the saturated vapor pressure curve of the circulating refrigerant and the valve opening characteristic becomes larger as the temperature becomes lower, an excessive pressure difference is obtained, so that the expansion valve opens more than necessary. When the expansion valve is over-opened, a liquid return phenomenon occurs. As a result, there is a problem that the superheat control is broken and the refrigerating capacity is reduced.

  On the other hand, since the thermal load is large in the high temperature region, it is desirable to increase the flow rate of the circulating refrigerant. However, when the pressure difference between the saturated vapor pressure curve of the circulating refrigerant and the valve opening characteristic decreases as the temperature increases, the pressure difference becomes excessive. As a result, there was a problem that the opening required for the expansion valve could not be obtained.

  In view of the above problems, an object of the present invention is to provide an improved refrigeration cycle apparatus.

  An object of the present invention is to provide a refrigeration cycle apparatus that uses a mixed refrigerant as a circulating refrigerant and can be stably operated even in a low temperature region or a high temperature region.

  Another object of the present invention is to provide a refrigeration cycle apparatus that can stably operate from a low temperature region to a high temperature region in a refrigeration cycle apparatus that uses a mixed refrigerant as a circulating refrigerant.

  In order to achieve the above object, the present invention employs the following technical means. In the invention described in claim 1, the refrigeration includes a compressor (20), a condenser (30), an expansion valve (40), and an evaporator (50), and circulates a mixed refrigerant in which a plurality of component refrigerants are mixed. In the cycle device, the expansion valve (40) has a valve part (41) that adjusts the amount of refrigerant supplied to the evaporator (50) by changing the opening degree, and the pressure of the enclosed refrigerant enclosed therein. A power element (42) for adjusting the opening of the valve portion (41), and the slope of the saturated vapor pressure curve (SV1) indicated by the enclosed refrigerant is larger than the slope of the saturated vapor pressure curve (SV0) indicated by the mixed refrigerant. Adopt technical means. According to this invention, the opening degree of the expansion valve can be set to an opening degree corresponding to the load. In the low temperature region, when the slope of the saturated vapor pressure curve (SV1) indicated by the filled refrigerant is larger than the slope of the saturated vapor pressure curve (SV0) indicated by the mixed refrigerant, it is avoided that the valve opening is excessive. In the high temperature region, when the slope of the saturated vapor pressure curve (SV1) indicated by the enclosed refrigerant is larger than the slope of the saturated vapor pressure curve (SV0) indicated by the mixed refrigerant, it is avoided that the valve opening becomes too small.

  In the second aspect of the invention, the enclosed refrigerant includes one component refrigerant among the plurality of component refrigerants, wherein the gradient of the saturated vapor pressure curve is larger than the gradient of the saturated vapor pressure curve (SV0) of the mixed refrigerant. Adopt means. According to this invention, the control characteristic of the expansion valve can be defined using the component refrigerant contained in the mixed refrigerant.

  The invention according to claim 3 employs a technical means in which the encapsulated refrigerant includes one component refrigerant having the largest slope of the saturated vapor pressure curve among the plurality of component refrigerants.

  The invention according to claim 4 employs a technical means in which the enclosed refrigerant includes one or a plurality of component refrigerants excluding the component refrigerant having the smallest slope of the saturated vapor pressure curve among the plurality of component refrigerants.

  In the invention according to claim 5, the technical means that the enclosed refrigerant contains only one component refrigerant is adopted. According to the present invention, there is an advantage that the refrigerant can be sealed in the expansion valve by a simple process.

  According to the invention of claim 6, the slope of the saturated vapor pressure curve (SV1) indicated by the enclosed refrigerant is larger than the slope of the saturated vapor pressure curve (SV0) indicated by the mixed refrigerant from the low temperature region to the high temperature region. Adopt means. According to the present invention, the opening degree of the expansion valve is prevented from becoming excessive in the low temperature region, and the opening degree suitable for the load is provided in the high temperature region. As a result, stable operation is possible from the low temperature region to the high temperature region.

  According to the seventh aspect of the present invention, the difference in the saturated vapor pressure (SD) between the saturated vapor pressure curve (SV1) indicated by the enclosed refrigerant and the saturated vapor pressure curve (SV0) indicated by the mixed refrigerant increases the evaporation temperature. Adopt technical means of gradually increasing according to

  In addition, the code | symbol in the parenthesis as described in a claim and said each means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is applied to a refrigeration cycle apparatus 10 for a refrigerator will be described. In FIG. 1, the refrigeration cycle apparatus 10 includes a compressor 20, a condenser 30, an expansion valve 40, and an evaporator 50. These parts are sequentially connected by a plurality of pipes to form a closed circuit. An internal heat exchanger 60 that exchanges heat between the high-pressure refrigerant between the condenser 30 and the expansion valve 40 and the low-pressure refrigerant between the evaporator 50 and the compressor 20 is provided.

  The refrigeration cycle apparatus 10 is used as a refrigerator. The compressor 20 compresses the circulating refrigerant to a high temperature and a high pressure. The compressor 20 is driven by an internal combustion engine or is driven by an electric motor. The compressor 20 can be a fixed capacity type or a variable capacity type. The condenser 30 is a high-pressure side heat exchanger. The condenser 30 is connected to the discharge side of the compressor 110 and condenses and liquefies the refrigerant by exchanging heat with the outside air. The expansion valve 40 is a pressure reducer. The expansion valve 40 decompresses and expands the liquid-phase refrigerant that has flowed out of the condenser 30 in an enthalpy manner. The expansion valve 40 controls the throttle opening so that the refrigerant state at the outlet of the evaporator 50 becomes a predetermined state. The expansion valve 40 is a temperature-sensitive expansion valve that senses the refrigerant state based on temperature. The evaporator 50 is a low-pressure side heat exchanger and is also called a cooler or a heat absorber. The evaporator 50 cools the air in the freezer to be cooled as the refrigerant evaporates inside.

  The expansion valve 40 will be described with reference to FIG. The expansion valve 40 has a structure called an outer equation. The expansion valve 40 includes a valve portion 41 that adjusts the amount of refrigerant supplied to the evaporator 50, and a power element 42 that adjusts the opening degree of the valve portion 41. The valve unit 41 can be configured by a valve seat, a valve body, and a valve closing spring. The power element 42 as the temperature sensing unit includes a means for sensing the refrigerant state at the outlet of the evaporator 50, a control unit for generating an operation amount of the valve unit 41 so that the refrigerant state matches the target state, and an operation amount. Accordingly, it is a fluid pressure type device that realizes a driving means for adjusting the opening degree of the valve portion 41 accordingly.

  The power element 42 includes a diaphragm 43 as a pressure sensitive member. The diaphragm 43 partitions the first chamber 44 and the second chamber 45. A valve rod 46 that drives the valve body is connected to the diaphragm 43. The diaphragm 43 is displaced by the differential pressure between the first chamber 44 and the second chamber 45 and adjusts the opening of the valve portion 41. The first chamber 44 communicates with the temperature sensing cylinder 48 through the pipe 47 to form a sealed space. A medium is sealed in the first chamber 44. The medium includes a two-phase sealed refrigerant and an adjustment auxiliary gas. The temperature sensing cylinder 48 is provided in contact with a pipe near the outlet of the evaporator 50. As a result, the temperature of the refrigerant at the outlet of the evaporator 50 is transmitted to the medium in the first chamber 44. The enclosed refrigerant senses the refrigerant temperature at the outlet of the evaporator 50. The enclosed refrigerant changes the pressure in the first chamber 44 depending on the refrigerant temperature at the outlet of the evaporator 50. The second chamber 45 is communicated with a passage near the outlet of the evaporator 50 by a pipe 49. As a result, the evaporation pressure of the circulating refrigerant in the evaporator 50 is introduced into the second chamber 45. According to the expansion valve 40, the diaphragm 43 is displaced according to a differential pressure between the evaporation pressure of the evaporator 50 and the pressure corresponding to the temperature of the circulating refrigerant at the outlet of the evaporator 50.

  The circulating refrigerant is a mixed refrigerant in which a plurality of component refrigerants having different saturation vapor pressure curves are mixed. The circulating refrigerant can include three or more component refrigerants. The mixed refrigerant includes a first component refrigerant, a second component refrigerant, and a third component refrigerant. The boiling points of these component refrigerants are: first component refrigerant> second component refrigerant> third component refrigerant. The sealed refrigerant contains only one component refrigerant. The configuration in which only one component refrigerant is used as the encapsulated refrigerant makes it possible to simplify the encapsulating process in the power element 42.

  2 to 4 are temperature-pressure graphs in which the horizontal axis indicates the temperature T and the vertical axis indicates the pressure P. FIG. FIG. 2 shows a saturated vapor pressure curve SV0 of the mixed refrigerant and saturated vapor pressure curves SV1, SV2, and SV3 of the component refrigerants. As shown in the figure, the saturated vapor pressure of the first component refrigerant is the highest. The saturation vapor pressure of the third component refrigerant is the lowest. The saturated vapor pressure curve SV0 of the mixed refrigerant passes between the saturated vapor pressure curves of the two component refrigerants having a relatively low saturated vapor pressure. Specifically, it passes between the saturated vapor pressure curve SV2 of the second component refrigerant and the saturated vapor pressure curve SV3 of the third component refrigerant.

  The saturated vapor pressure curve SV1 of the first component refrigerant shows the largest slope. The saturation vapor pressure curve SV3 of the third component refrigerant shows the smallest slope. The slope of the saturated vapor pressure curve SV1 indicated by the first component refrigerant as the enclosed refrigerant is larger than the slope of the saturated vapor pressure curve SV0 indicated by the mixed refrigerant from the low temperature region to the high temperature region. Further, the slope of the saturated vapor pressure curve SV2 indicated by the second component refrigerant is larger than the slope of the saturated vapor pressure curve SV0 indicated by the mixed refrigerant from the low temperature region to the high temperature region. The saturated vapor pressure curve SV3 of the third component refrigerant has a slope smaller than the saturated vapor pressure curve SV0 of the mixed refrigerant from the low temperature region to the high temperature region.

  The difference SD of the saturated vapor pressure between the saturated vapor pressure curve SV1 indicated by the first component refrigerant and the saturated vapor pressure curve SV0 indicated by the mixed refrigerant gradually increases as the evaporation temperature increases. As a result, the pressure difference SD2 at the high load temperature is larger than the pressure difference SD1 at the low load temperature. In this embodiment, −10 ° C. is a high load temperature, and −40 ° C. is a low load temperature.

  FIG. 2 shows a saturated vapor pressure curve SVC of a comparative refrigerant as a comparative example. The comparative refrigerant is not a component of the mixed refrigerant. When the comparative refrigerant is an enclosed refrigerant, the slope of the saturated vapor pressure curve SVC is smaller than the saturated vapor pressure curve SV0 of the mixed refrigerant.

  FIG. 3 shows a characteristic curve indicating the vapor pressure of the medium after adding an auxiliary gas such as helium to each component refrigerant. The characteristic curve in FIG. 3 is adjusted by auxiliary gas or the like so that the circulating refrigerant is controlled to a predetermined state at −30 ° C. which is a reference temperature as a refrigerator. The characteristic curve SV1 + shows the characteristic after adjustment of the first component refrigerant. A characteristic curve SV2 + indicates the characteristic after adjustment of the second component refrigerant. A characteristic curve SV3 + indicates the characteristic after adjustment of the third component refrigerant. A characteristic curve SVC + indicates the characteristic after adjustment of the comparative refrigerant. Even after the adjustment with the auxiliary gas, the slope of the saturated vapor pressure curve of the component refrigerant is maintained.

  FIG. 4 shows a characteristic curve indicating a valve opening pressure in consideration of a bias force such as a valve closing spring of the expansion valve 40. The characteristic curve SV1D shows the valve opening characteristic of the medium containing the first component refrigerant. The characteristic curve SVCD shows the valve opening characteristic of the medium containing the comparative refrigerant.

  The characteristic curve SVCD has a smaller slope than the characteristic curve SV1D. For this reason, the characteristic curve SVCD passes on the higher pressure side than the characteristic curve SV1D in a low temperature region lower than the reference temperature. In addition, in this low temperature region, the characteristic curve SVCD moves away from the saturated vapor pressure curve SV0 of the mixed refrigerant in the pressure axis direction. The characteristic curve SVCD generates a pressure difference PD1 larger than the pressure difference PD0 at the reference temperature in the low temperature region. As a result, an excessive pressure difference occurs in the low temperature region, and the opening degree becomes excessive. Characteristic curve SVCD passes on the lower pressure side than characteristic curve SV1D in a high temperature region higher than the reference temperature. The characteristic curve SVCD generates a pressure difference PD2 smaller than the pressure difference PD0 at the reference temperature in the high temperature region. As a result, when the characteristic curve SVCD is employed, the opening degree is insufficient in the high temperature region.

  On the other hand, according to the characteristic curve SV1D, the pressure difference gradually increases from the low temperature region to the high temperature region. The characteristic curve SV1D generates a pressure difference PD3 smaller than the pressure difference PD0 at the reference temperature in the low temperature region. The characteristic curve SV1D generates a pressure difference PD4 larger than the pressure difference PD0 at the reference temperature in the high temperature region. For this reason, the opening degree of the expansion valve 40 gradually increases from the low temperature region toward the high temperature region.

  In this embodiment, R404A is used as the mixed refrigerant. In the mixed refrigerant R404A, R125 is used as the first component refrigerant, R143a is used as the second component refrigerant, and R134a is used as the third component refrigerant. The enclosed refrigerant is R125 which is the first component refrigerant. R22 is used as a comparative refrigerant.

  When the refrigeration cycle apparatus 10 is operated, the expansion valve 40 adjusts the opening degree of the valve unit 41 so that the refrigerant state at the outlet of the evaporator 50 matches the target state. The operation range of the refrigeration cycle apparatus 10 as a refrigerator extends from a low temperature region to a high temperature region. The vicinity of −40 ° C., which is a low load temperature corresponding to a low load state as a refrigerator, is a temperature that can be called an extremely low temperature among the evaporation temperatures as a refrigerator. In the vicinity of the low load temperature, the refrigerant flow rate decreases and the opening degree of the expansion valve 40 also decreases. On the other hand, in the vicinity of −10 ° C., which is a high load temperature corresponding to a high load state as a refrigerator, a large amount of refrigerant corresponding to a high load is allowed to flow.

  The component refrigerant selected as the encapsulated refrigerant has a slope of the saturated vapor pressure curve that is higher than the slope of the saturated vapor pressure curve of the mixed refrigerant that is the circulating refrigerant when the evaporation temperature is in the low temperature region, particularly in the very low temperature region. large. This feature avoids that the opening degree of the expansion valve 40 becomes an excessive opening degree exceeding the opening degree corresponding to the load in a low temperature region, particularly in a very low temperature region. Further, a large slope in the low temperature region gives sufficient pressure change and opening degree change with respect to temperature change. For this reason, in the vicinity of the low load temperature, stable control can be maintained even within a small opening range. As a result, stable superheat control is possible even in a low temperature region, particularly in a very low temperature region.

  The component refrigerant selected as the encapsulated refrigerant desirably has a saturated vapor pressure curve similar to the saturated vapor pressure curve SV0 of the mixed refrigerant when the evaporation temperature is in a high temperature region. This feature avoids an excessive opening exceeding the opening corresponding to the load while enabling a relatively large valve opening suitable for a high load in a high temperature region including a high load temperature. As a result, even in a high temperature region, it is possible to avoid the liquid back phenomenon and perform stable operation.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows. The present invention is not limited to a refrigeration cycle apparatus that employs R404A as a circulating refrigerant, but may be applied to a refrigeration cycle apparatus that employs various mixed refrigerants as a circulating refrigerant. The present invention may be applied to a refrigeration cycle apparatus using a plurality of refrigerants as enclosed refrigerants. One or a plurality of component refrigerants excluding the component refrigerant having the smallest slope of the saturated vapor pressure curve may be used as the enclosed refrigerant. For example, the second component refrigerant R143a in the above embodiment may be an enclosed refrigerant. The present invention can be applied to an expansion valve called a joint type or a box type. Further, the present invention can be applied to an expansion valve called an inner level expression or an outer level expression. Furthermore, the present invention can be applied to an expansion valve having a cassette structure. Furthermore, the present invention may be applied to a refrigeration cycle apparatus including an ejector.

It is a block diagram showing one embodiment of the refrigerating cycle device to which the present invention is applied. It is a temperature-pressure graph which shows the saturated vapor pressure curve of the refrigerant | coolant in one Embodiment. It is a temperature-pressure graph which shows the vapor pressure of the enclosure medium in one Embodiment. It is a temperature-pressure graph which shows the valve opening pressure characteristic in one Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Refrigeration cycle apparatus 20 ... Compressor 30 ... Condenser 40 ... Expansion valve 50 ... Evaporator 60 ... Internal heat exchanger SV0 ... Saturated vapor pressure curve of mixed refrigerant SV1 ... Saturated vapor pressure curve of first component refrigerant SV2 ... First Saturated vapor pressure curve of two-component refrigerant SV3 ... Saturated vapor pressure curve of third-component refrigerant SVC ... Saturated vapor pressure curve of comparative refrigerant

Claims (7)

In a refrigeration cycle apparatus comprising a compressor (20), a condenser (30), an expansion valve (40), and an evaporator (50), and circulating a mixed refrigerant in which a plurality of component refrigerants are mixed.
The expansion valve (40)
A valve part (41) for adjusting the amount of refrigerant supplied to the evaporator (50) by changing the opening;
A power element (42) for adjusting the opening of the valve portion (41) according to the pressure of the enclosed refrigerant sealed inside,
The refrigeration cycle apparatus characterized in that a slope of a saturated vapor pressure curve (SV1) indicated by the enclosed refrigerant is larger than a slope of a saturated vapor pressure curve (SV0) indicated by the mixed refrigerant. 2. The encapsulated refrigerant includes one of the plurality of component refrigerants, the component refrigerant having a slope of a saturated vapor pressure curve larger than a slope of a saturated vapor pressure curve (SV0) of the mixed refrigerant. The refrigeration cycle apparatus described in 1. The refrigeration cycle apparatus according to claim 2, wherein the encapsulated refrigerant includes one of the plurality of component refrigerants that has the largest slope of a saturated vapor pressure curve. The said enclosed refrigerant | coolant contains the one or some said component refrigerant | coolant except the said component refrigerant | coolant with the smallest inclination of a saturated vapor pressure curve among the said some component refrigerant | coolants. The refrigeration cycle apparatus according to crab. The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein the enclosed refrigerant includes only one component refrigerant. The slope of the saturated vapor pressure curve (SV1) indicated by the enclosed refrigerant is larger than the slope of the saturated vapor pressure curve (SV0) indicated by the mixed refrigerant from a low temperature region to a high temperature region. The refrigeration cycle apparatus according to any one of 5. The difference (SD) in saturated vapor pressure between the saturated vapor pressure curve (SV1) indicated by the enclosed refrigerant and the saturated vapor pressure curve (SV0) indicated by the mixed refrigerant gradually increases as the evaporation temperature increases. The refrigeration cycle apparatus according to any one of claims 1 to 6.

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