JP2006234207A - Refrigerating cycle pressure reducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle pressure reducing device operated with suitable cycle efficiency even in the case that pressure at a high-pressure side reaches critical pressure or lower as well as the case that the pressure at the high-pressure side reaches the critical pressure or higher. <P>SOLUTION: The refrigerating cycle pressure reducing device with an accumulator 150 is applicable to a refrigerating cycle where the pressure of a refrigerant in a radiator 120 is the critical pressure or higher. It reduces the pressure of the refrigerant flowing out of the radiator 120 and delivers the pressure-reduced refrigerant to an evaporator 140. It comprises a valve element 134 opened in response to a refrigerant pressure difference ΔP between the side of the radiator 120 and the side of the evaporator 140 and a fixed restriction part 136 whose flow path resistance is set to be a predetermined value for making the side of the radiator 120 consistently communicate with the side of the evaporator 140. When the pressure of the refrigerant in the radiator 120 is at least the critical pressure or lower, the valve element 134 is kept in a closed state and the pressure is reduced by the fixed restriction part 136. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a decompression device that controls a radiator outlet side pressure of a vapor compression refrigeration cycle in which a high-pressure side pressure of a refrigerant can be equal to or higher than a critical pressure, and is used for a carbon dioxide (CO ₂ ) as a refrigerant. Is preferred.

  Conventionally, as a decompression device for a refrigeration cycle in which the refrigerant is carbon dioxide and the pressure in the radiator for cooling the refrigerant exceeds the critical pressure, for example, one disclosed in Patent Document 1 is known. That is, this decompression device decompresses the refrigerant flowing out of the radiator and also flows out the decompressed refrigerant toward the evaporator, and the valve body formed in the housing is connected to the pressure in the radiator. The refrigeration cycle according to the heat load by varying the opening according to the pressure in the evaporator so that the pressure difference with the pressure in the evaporator becomes a predetermined pressure difference ΔP (for example, 5.5 to 7 MPa). It is possible to drive.

Here, the predetermined pressure difference ΔP is the pressure in the radiator where the coefficient of performance COP (ratio of the refrigerating capacity in the evaporator to the work in the compressor) corresponding to the pressure in the radiator is near the maximum value. (9 to 12.5 MPa) and a pressure (3.5 to 5.5 MPa) at which frost due to condensed water is not generated in the evaporator, the difference between the two (5.5 to 7 MPa) is determined.
Japanese Patent Laid-Open No. 10-9719

  However, when the refrigeration cycle is operated including a region where the pressure in the radiator is equal to or lower than the critical pressure, the cycle efficiency is controlled by controlling the radiator and the evaporator so as to always have a predetermined pressure difference ΔP. (The above-mentioned coefficient of performance) gets worse.

  For example, when the outside air temperature is low (for example, 10 ° C.), when the pressure in the evaporator is 3.8 MPa (the pressure at which the carbon dioxide refrigerant is 3 ° C., it is possible to prevent the generation of frost due to condensed water). Although the pressure in the radiator is able to operate the refrigeration cycle at a pressure not exceeding the critical pressure (7.4 MPa) (for example, 7 MPa), the pressure in the radiator is intentionally maintained high ( 3.8 + 5.5 = 9.3 MPa), the work in the compressor increases unnecessarily, and the cycle efficiency deteriorates.

  In view of the above problems, an object of the present invention is to provide a decompression device for a refrigeration cycle that enables operation at a suitable cycle efficiency even when the high-pressure side pressure is equal to or higher than the critical pressure, even when the pressure is equal to or lower than the critical pressure. There is to do.

  In order to achieve the above object, the present invention uses the following technical means.

  In the first aspect of the invention, the compressor (110), the radiator (120), the evaporator (140), and the accumulator (150) are sequentially connected in an annular shape as main components, and the refrigerant circulates. (120) is applied to the refrigeration cycle (100) in which the refrigerant pressure can be equal to or higher than the critical pressure, and is disposed between the radiator (120) and the evaporator (140). 120) In the decompression device for the refrigeration cycle that decompresses the refrigerant that has flowed out from 120) and flows the decompressed refrigerant toward the evaporator (140), between the radiator (120) side and the evaporator (140) side. The valve body (134) that opens according to the pressure difference (ΔP) of the refrigerant is always in communication between the radiator (120) side and the evaporator (140) side, and the flow resistance becomes a predetermined value. With a fixed aperture (136) When the refrigerant pressure in the radiator (120) is at least below the critical pressure and the refrigeration cycle (100) is operated, the valve body (134) is maintained in the closed state, and the fixed throttle (136) The feature is that the pressure is reduced.

  Thereby, when the pressure of the refrigerant in the radiator (120) is lower than the critical pressure, the decompression device (130) functions only by the fixed throttle (136), so that the fixed throttle (136) and the accumulator (150) are used. The refrigeration cycle (100) can be efficiently operated by the self-control action (details are described in “Best Mode for Carrying Out the Invention” below).

  Further, when the refrigerant pressure in the radiator (120) is equal to or higher than the critical pressure, the valve body (134) is opened, and the fluctuation of the heat load (refrigeration capacity) in the evaporator (140) is expressed by the pressure difference (ΔP). Instead, the valve opening in the valve body part (134) is adjusted, and the required refrigerant flow rate is secured while suppressing an excessive pressure rise in the radiator (120). Refrigeration cycle (100) can be operated.

  In the invention according to claim 2, the flow resistance of the fixed throttle portion (136) is such that the dryness of the refrigerant on the outlet side of the radiator (120) during the refrigeration cycle (100) operation is 0.25 or less. It is characterized by being set.

  Thereby, since it can be set as the area | region where the fluctuation | variation amount of the refrigerant | coolant flow volume which distribute | circulates a fixed throttle part (136) changes largely, it becomes easy to exhibit the self-control effect | action of the circulating refrigerant | coolant flow volume in an accumulator cycle.

  In the invention according to claim 3, the refrigeration cycle (100) includes an internal heat exchanger (160) for exchanging heat between the refrigerant on the outlet side of the radiator (120) and the refrigerant on the outlet side of the evaporator (140). It is characterized by having.

  As a result, the refrigerant flowing out of the radiator (120) can be cooled by the refrigerant from the evaporator (140), so that the enthalpy difference that can be taken by the evaporator (140) can be increased, and the evaporation The refrigerating capacity in the vessel (140) can be improved.

  The invention according to claim 4 is characterized in that the refrigerant is carbon dioxide, and the valve body (134) is opened at a pressure difference (ΔP) of at least 3.6 MPa.

  In carbon dioxide, the pressure at which the temperature becomes 3 ° C. is 3.8 MPa, and the critical pressure is uniquely determined as 7.4 MPa. Therefore, when the minimum pressure at which frost is not generated from the condensed water generated on the surface of the evaporator (140) is set to 3.8 MPa, the pressure difference (ΔP) is set to 3.6 MPa or more, so that the inside of the radiator (120) The pressure reducing device (130) in which the valve body part (134) opens and operates when the pressure is equal to or higher than the critical pressure (3.8 + 3.6 = 7.4 MPa).

  As in the fifth aspect of the invention, it is preferable that the flow path resistance of the fixed throttle portion (136) is set to be equivalent to an orifice of φ0.3 mm to φ0.7 mm.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows a corresponding relationship with the specific means of embodiment description mentioned later.

(First embodiment)
A first embodiment according to the present invention will be described below with reference to FIGS. 1 is a schematic diagram showing the entire configuration of the refrigeration cycle 100, FIG. 2 is a cross-sectional view showing a refrigeration cycle decompression device 130, FIG. 3 is a graph showing a coefficient of performance COP of the cycle with respect to the orifice inner diameter, and FIG. 5 is a graph showing the amount of displacement of the valve body part 134 with respect to the pressure difference of the decompression device 130, FIG. 5 is a graph showing the refrigerant flow rate with respect to the pressure difference of the refrigeration cycle decompression device 130, and FIG. FIG. 7 is a graph showing the operating state of the refrigeration cycle 100 on the Mollier diagram. FIG. 7 is a graph showing the refrigerant flow rate when the valve is closed (when functioning as a fixed throttle) with respect to the dryness of the refrigerant.

  The refrigeration cycle decompression device (hereinafter, decompression device) 130 of the first embodiment is applied to the refrigeration cycle 100 incorporated in a vehicle air conditioner. As shown in FIG. 1, the refrigeration cycle 100 is formed by sequentially connecting a compressor 110, a radiator 120, the pressure reducing device 130, an evaporator 140, and an accumulator 150 in an annular shape. Here, carbon dioxide is used as the refrigerant, and the refrigerant pressure in the radiator 120 (hereinafter, high-pressure side pressure) can range from a region below the critical pressure to a region above the critical pressure depending on the operating conditions of the refrigeration cycle 100. It is like that.

  The compressor 110 is a fluid machine that operates by receiving a driving force from a vehicle engine (not shown) and compresses the gas-phase refrigerant from the accumulator 150 to a high temperature and a high pressure. The radiator 120 is a heat exchanger (gas cooler) that is disposed in front of the vehicle engine room and cools the refrigerant by exchanging heat between the refrigerant compressed by the compressor 110 and the outside air flowing in from the vehicle grill. . The decompression device 130 is decompression means that decompresses the high-pressure refrigerant that has flowed out of the radiator 120 and also flows out the refrigerant that has been decompressed into a gas-liquid two-phase state toward the evaporator 140. Details of the decompression device 130 will be described later.

  The evaporator 140 is a heat exchanger that evaporates the refrigerant that has flowed out of the decompression device 130 by heat exchange with the conditioned air that is blown into the passenger compartment, and the conditioned air is cooled by the latent heat of evaporation when the refrigerant evaporates. Become. Hereinafter, the refrigerant pressure in the evaporator 140 after being decompressed by the decompression device 130 will be referred to as a low pressure side pressure. The accumulator 150 is a container that separates the refrigerant flowing out of the evaporator 140 into a gas-liquid two-phase, temporarily stores the liquid-phase refrigerant, and discharges the gas-phase refrigerant to the compressor 110.

  Next, the decompression device 130 will be described in detail with reference to FIG. The decompression device 130 is formed by providing a valve body part 134, a spring 135, a fixed orifice (corresponding to the fixed throttle part in the present invention) 136 and the like in a case 131.

  The case 131 is a container body made of a metal such as stainless steel or brass and having a bottomed cylindrical shape. An inlet portion 132 communicating with the radiator 120 is formed in a circular shape on one bottom side, and the other side is formed. An outlet portion 133 communicating with the evaporator 140 is formed on the bottom side. The inner circumferential portion of the inlet portion 132 is formed as a valve seat 132a with which the valve body portion 134 abuts.

  The valve body part 134 is formed so that the center part protrudes in a conical shape toward the inlet part 132 side with a disk-shaped member as a base, and is arranged to face the valve seat 132a to increase the opening degree of the inlet part 132. It comes to adjust. In addition, a guide part 134 a extending toward the outlet part 133 is formed on the disc-shaped outer peripheral part of the valve body part 134, and this guide part 134 a comes into contact with the inner wall of the case 131, so that the valve body part 134 is formed. It is supposed to guide the movement of. A plurality of through holes 134b are formed in the circumferential direction between the valve body part 134 and the guide part 134a, and the inlet part 132 side space sandwiching the valve body part 134 in the case 131 by the through holes 134b. The outlet portion 133 side space is in communication.

  The spring 135 is a metal elastic member, and is disposed between the bottom portion where the outlet portion 133 is provided in the case 131 and the valve body portion 134, and the valve body portion 134 is moved into the inlet portion by the elastic force. Pressing to the 132 side.

  The fixed orifice 136 is a throttle whose flow resistance is set to a predetermined value, and is provided so as to pass through the central part of the valve body part 134, and has an inlet part 132 (radiator 120 side) and an outlet part 133 (evaporator). 140 side) is always in communication. Between the inner diameter of the fixed orifice 136 and the coefficient of performance COP of the refrigeration cycle 100, there is a relationship as shown in FIG. 3 according to the outside air temperature (the COP has a maximum value at a predetermined inner diameter). On the other hand, in order to obtain a good coefficient of performance COP, the diameter of the fixed orifice 136 is preferably set to φ0.3 to 0.7 mm.

  The case 131 has one bottom part integrally formed with the cylindrical main body part, and the other bottom part formed separately as a lid part. After the valve body part 134 and the spring 135 are accommodated in the case 131, the lid is closed. The part is joined to the main body part by joining means such as welding or screw fastening.

  Here, when the high pressure side pressure of the refrigerant applied to the inlet portion 132 is P1, the low pressure side pressure of the refrigerant applied to the outlet portion 133 is P2, and the acting force due to the elasticity of the spring 135 is F, the high pressure side pressure P1 and the low pressure side pressure P2 The pressure difference ΔP (= P1−P2) with the resistance against the acting force F of the spring 135. In the present embodiment, by setting the elastic characteristic of the spring 135, the acting force F overcomes the pressure difference ΔP until the pressure difference ΔP reaches 3.6 MPa as shown in FIG. When the pressure difference ΔP is equal to or greater than 3.6 MPa, the pressure difference ΔP overcomes the acting force F to open the valve body portion 134. Hereinafter, as the pressure difference ΔP increases, the displacement amount of the valve body portion 134 (the valve opening degree at the inlet portion 132) increases.

  Accordingly, as shown in FIG. 5, until the valve body part 134 is opened (until the pressure difference ΔP reaches 3.6 MPa), the refrigerant flows through the fixed orifice 136 and corresponds to the flow path resistance. After the refrigerant flow rate (weight flow rate) is obtained and the valve body part 134 is opened (the pressure difference ΔP is 3.6 MPa or more), the refrigerant according to the displacement amount of the valve body part 134 (the fixed orifice 136 is also a refrigerant). (Flowing) refrigerant flow rate is obtained.

  Further, by setting the flow resistance of the fixed orifice 136 (for example, the inner diameter of the orifice or the flow path length of the orifice), as shown in FIG. 6, the refrigerant flowing from the radiator 120 to the decompressor 130 (fixed orifice 136) can be obtained. The dryness is set to 0.25 or less.

  Next, the operation of the refrigeration cycle 100 and the decompression device 130 based on the above configuration will be described with reference to FIG. When the compressor 110 is operated according to the cooling request, the refrigerant circulates in the refrigeration cycle 100, and the conditioned air is cooled by the latent heat of vaporization of the refrigerant in the evaporator 140 as described above.

  Here, with the cooling of the conditioned air, moisture in the air condenses and adheres as condensed water on the surface of the evaporator 140, but frost is not generated from the condensed water by the cooling action. Therefore, while lowering the temperature of the low-pressure side refrigerant (while ensuring the refrigerating capacity), it is prevented from becoming below 0 ° C. (below the freezing temperature). For example, if the safe temperature of the refrigerant for preventing the generation of frost is set to 3 ° C., the low pressure side pressure is 3.8 MPa when the refrigerant is carbon dioxide. This low-pressure side pressure (3.8 MPa) is kept constant by, for example, grasping the downstream side air temperature of the evaporator 140 with a temperature sensor or the like and controlling the refrigerant discharge amount of the compressor 110.

  As shown in FIG. 7, in the decompression device 130 of the present embodiment, the valve body portion 134 is closed until the pressure difference ΔP reaches 3.6 MPa and the high-pressure side pressure reaches 7.4 MPa (that is, the critical pressure). Only the fixed orifice 136 functions because the valve state is maintained. Further, since the flow resistance of the fixed orifice 136 is set so that the dryness of the refrigerant at the outlet side of the radiator 120 is 0.25 or less, the self-control action by the fixed orifice 136 and the accumulator 150 works effectively. Thus, the refrigeration cycle 100 can be operated efficiently.

  That is, in the operation of the refrigeration cycle 100, when the refrigerant after circulation of the radiator 120 flows into the decompression device 130 in a gas-liquid two-phase state and is depressurized, for example, the refrigerant flow rate (the degree of dryness) includes Decreases and the degree of heating (superheat) in the evaporator 140 increases. As a result, the liquid refrigerant in the accumulator 150 moves to the radiator 120 side, and the liquid refrigerant ratio on the outlet side of the radiator 120 increases (shifts to a high degree of supercooling or a low degree of dryness).

  On the contrary, when the refrigerant after circulation of the radiator 120 flows into the decompression device 130 in the liquid phase state and is decompressed (supercooling region), the refrigerant flow rate increases compared to the case where the gas phase refrigerant is included, and the evaporator 140 The degree of heating at (superheat) decreases. As a result, the amount of liquid refrigerant stored in the accumulator 150 increases and the amount of liquid refrigerant in the radiator 120 decreases, so that the ratio of liquid refrigerant on the outlet side of the radiator 120 decreases (low degree of supercooling or high degree of dryness). Migration).

  By repeating this, the refrigerant after circulation of the radiator 120 is balanced and depressurized in the vicinity of the optimum degree of supercooling (subcool constant line in FIG. 7, that is, the maximum coefficient of performance line). Efficient operation will be performed.

  On the other hand, when the pressure difference ΔP in the decompression device 130 is 3.6 MPa or more and the high-pressure side pressure is 7.4 MPa (that is, the critical pressure) or more, the valve body part 134 is opened. The change in the load (refrigeration capacity) is substituted with the pressure difference ΔP, and the valve opening degree in the valve body part 134 is adjusted, and the necessary refrigerant while suppressing an excessive pressure increase in the radiator 120. An efficient operation of the refrigeration cycle 100 becomes possible by securing the flow rate.

  In general, the decompression device 130 of the present embodiment enables efficient operation of the refrigeration cycle 100 even when the high-pressure side pressure is equal to or higher than the critical pressure and even when the pressure is equal to or lower than the critical pressure.

(Second Embodiment)
A second embodiment of the present invention is shown in FIG. The second embodiment is different from the first embodiment in that the setting position of the fixed throttle portion of the decompression device 130 is changed and an internal heat exchanger 160 is provided in the refrigeration cycle 100.

  Here, the fixed throttle portion in the decompression device 130 is formed as a fixed orifice 136 a in the case 131 so as to be aligned with the inlet portion 132. The radiator 120 and the fixed orifice 136a are connected so as to communicate with each other.

  The internal heat exchanger 160 is set to have two internal flow paths so that the refrigerant flowing out of the radiator 120 flows through one internal flow path, and the accumulator 150 is connected to the other internal flow path. The refrigerant flowing out from (evaporator 140) is allowed to flow.

  According to the above configuration, when the pressure difference ΔP is 3.6 MPa or less, the refrigerant from the radiator 120 is depressurized by the fixed orifice 136a, and the depressurized refrigerant reaches the evaporator 140 through the through hole 134b and the outlet 133. The same effect as in the first embodiment can be obtained.

  In addition, since the refrigerant flowing out of the radiator 120 can be cooled by the refrigerant from the evaporator 140 side by the internal heat exchanger 160, the enthalpy difference that can be taken by the evaporator 140 can be increased, The refrigerating capacity in the evaporator 140 can be improved.

(Third embodiment)
A third embodiment of the present invention is shown in FIG. In the third embodiment, the fixed throttle portion of the decompression device 130 is changed with respect to the second embodiment.

  Here, the fixed throttle portion is provided as a fixed throttle 136b such as a capillary tube, for example, and is parallel to the flow path connecting the inlet portion 132 and the outlet portion 133 when the valve body portion 134 is opened. A fixed aperture 136b is connected.

  Thereby, the decompression device 130 can be configured using the existing fixed aperture 136b, and the same effects as those of the first and second embodiments can be obtained.

(Other embodiments)
In the first to third embodiments, the pressure difference ΔP at which the valve body part 134 opens by setting the low-pressure side pressure to 3.8 MPa (refrigerant temperature 3 ° C.) is 3.6 MPa. The pressure difference ΔP may be determined so as to be equal to or greater than the difference between the low pressure side pressure to be set and the critical pressure.

  Moreover, although carbon dioxide was used as the refrigerant, it may be, for example, ethylene, ethane, nitrogen oxide, or the like as long as it can be used in the supercritical region.

It is a schematic diagram which shows the whole structure of the refrigerating cycle in 1st Embodiment. It is a cross section which shows the decompression device for refrigeration cycles in FIG. It is a graph which shows the coefficient of performance COP of the cycle with respect to an orifice inner diameter. It is a graph which shows the displacement amount of the valve body part with respect to the pressure difference of the decompression device for refrigeration cycles. It is a graph which shows the refrigerant | coolant flow volume with respect to the pressure difference of the decompression device for refrigeration cycles. It is a graph which shows the refrigerant | coolant flow rate at the time of valve closing with respect to the dryness of the refrigerant | coolant in the inlet part of the decompression device for refrigeration cycles (when functioning as a fixed throttle). It is a graph which shows the operating state of the refrigerating cycle on a Mollier diagram. It is a schematic diagram which shows the whole structure of the refrigerating cycle in 2nd Embodiment. It is a schematic diagram which shows the whole structure of the refrigerating cycle in 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Refrigeration cycle 110 Compressor 120 Radiator 130 Refrigeration cycle decompression device 134 Valve body part 136 Fixed orifice (fixed throttle part)
140 Evaporator 150 Accumulator 160 Internal heat exchanger

Claims (5)

As main components, a compressor (110), a radiator (120), an evaporator (140), and an accumulator (150) are sequentially connected in an annular manner to circulate the refrigerant, and the pressure of the refrigerant in the radiator (120) is increased. Applied to a refrigeration cycle (100) that can be above the critical pressure,
It is arrange | positioned between the said heat radiator (120) and the said evaporator (140), and decompresses the refrigerant | coolant which flowed out from the said heat radiator (120), and directs the pressure-reduced refrigerant | coolant to the said evaporator (140). In the refrigeration cycle decompression device flowing out,
A valve body (134) that opens according to the pressure difference (ΔP) of the refrigerant between the radiator (120) side and the evaporator (140) side;
A fixed restricting portion (136) in which the radiator (120) side and the evaporator (140) side are always in communication and the flow resistance is set to a predetermined value;
When the refrigerant pressure in the radiator (120) is at least equal to or lower than the critical pressure and the refrigeration cycle (100) is operated, the valve body part (134) is maintained in a closed state, and the fixed throttle part A decompression device for a refrigeration cycle, wherein the decompression is performed at (136).   The flow path resistance of the fixed throttle portion (136) is set so that the dryness of the refrigerant on the outlet side of the radiator (120) during the refrigeration cycle (100) operation is 0.25 or less. The decompression device for a refrigeration cycle according to claim 1, characterized in that:   The refrigeration cycle (100) includes an internal heat exchanger (160) for exchanging heat between the refrigerant on the outlet side of the radiator (120) and the refrigerant on the outlet side of the evaporator (140). The decompression device for a refrigeration cycle according to claim 1 or 2. The refrigerant is carbon dioxide;
The decompression device for a refrigeration cycle according to any one of claims 1 to 3, wherein the valve body (134) opens when the pressure difference (ΔP) is at least 3.6 MPa. .   The refrigeration cycle according to any one of claims 1 to 4, wherein the flow path resistance of the fixed throttle portion (136) is set to correspond to an orifice of φ0.3 mm to φ0.7 mm. Pressure reducing device.

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