JP3528433B2 - Vapor compression refrigeration cycle - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to carbon dioxide (CO
₂ ) A vapor compression refrigeration system that uses a refrigerant such as
It's about Kuru .

[0002]

2. Description of the Related Art In recent years, for example, Japanese Patent Publication No.
As described in JP-A-18602, carbon dioxide (C
Vapor compression refrigeration cycle using O ₂ (hereinafter CO
Abbreviated as ₂ cycles. ) Is proposed.

The operation of this CO ₂ cycle is, in principle, the same as the operation of a conventional vapor compression refrigeration cycle using freon. That is, as shown by A-B-C-D- A in FIG. 6 (CO ₂ Mollier chart), compressing the CO ₂ in the vapor phase by a compressor (A-B), the gas of the high temperature and high pressure CO ₂ in phase is cooled by a radiator (gas cooler) (BC). Then, the pressure is reduced by a pressure reducer (C-
D), by evaporating CO ₂ in the gas-liquid two-phase state (D-
A), the latent heat of vaporization is removed from the external fluid such as air to cool the external fluid. Note that CO ₂ undergoes a phase change to a gas-liquid two-phase state from when the pressure falls below the saturated liquid pressure (the pressure at the intersection of the line segment CD and the saturated liquid line SL).

However, CO₂The critical temperature is about 31 ℃
Critical temperature of conventional CFCs (for example, 112 ° C for R12)
Since it is lower than that of CO on the radiator side in summer etc.₂temperature
Is CO₂Will be higher than the critical point temperature. That is,
CO on the radiator outlet side ₂Does not condense (line segment BC
Does not intersect the saturated liquid line). In addition, the radiator outlet side (C
The state of point) is the discharge pressure of the compressor and C at the radiator outlet side.
O₂CO at the radiator exit side, which is determined by the temperature₂
The temperature is determined by the heat dissipation capacity of the radiator and the ambient temperature.
It And since the outside air temperature cannot be controlled,
CO at the radiator outlet₂The temperature should be substantially controlled
I can't.

Therefore, the state on the radiator outlet side (point C) can be controlled by controlling the discharge pressure of the compressor (radiator outlet side pressure). That is, in order to secure a sufficient cooling capacity (enthalpy difference) when the outside air temperature is high in summer, etc., as shown by E-F-G-H-E in FIG. Need to be higher.

[0006]

By the way, in order to control the pressure on the outlet side of the radiator, the above publication describes that the opening of the pressure reducer is manually controlled according to the required refrigerating capacity. is there. However, with this means, there is no problem as long as it is a confirmation test whether it is possible to control the refrigerating capacity by controlling the pressure on the radiator outlet side,
In an actual usage situation, the required refrigerating capacity changes from time to time. Therefore, by controlling the opening of the pressure reducer by manual operation, the CO
Unable to provide ₂ cycles.

In view of the above points, the present invention is a vapor compression type in which the radiator outlet side pressure can be controlled according to the required refrigerating capacity.
It is intended to provide a refrigeration cycle .

[0008]

The present invention uses the following technical means in order to achieve the above object. Claim 1
In the invention described in 3 , the pressure inside the radiator (2) is controlled by the refrigerant.
Heat dissipation in vapor compression refrigeration cycle exceeding field pressure
Pressure reducing device (3) for reducing the pressure of the refrigerant flowing out of the vessel (2)
The inlet (32) communicating with the radiator (2), and steam
A howe formed with an outlet (33) communicating with the generator (4)
With housing (31), flow into housing (31)
The space (32a) on the mouth (32) side and the sky on the outflow port (33) side
A valve port (34) for communicating with the space (33a) is formed,
The valve body (35) for adjusting the opening of the valve opening (34) is a housing.
The valve body (35) is provided in the inlet (3).
2) side space (32a) and outlet (33) side space (3
The opening of the valve port (34) is controlled according to the pressure in the evaporator (4) so that the pressure difference with 3a) becomes a predetermined pressure difference (ΔP).

As a result, as will be described later, when the heat load on the evaporator (4) rises, the opening of the valve port (34) is reduced, while the heat load on the evaporator (4) is reduced. At this time, the opening degree of the valve opening (34) is increased.
Therefore, when the heat load of the evaporator (4) increases, the outlet side pressure of the radiator (2) increases, while the evaporator (4)
When the heat load of 1 is reduced, the outlet side pressure of the radiator (2) is reduced. Therefore, the outlet side pressure of the radiator (2) of the vapor compression refrigeration cycle in which the pressure inside the radiator (4) exceeds the critical pressure of the refrigerant can be controlled.

Here, the "pressure in the evaporator (4)"
Does not mean the pressure in the evaporator (4) in a strict sense, but is a portion showing the pressure in the evaporator (4) in the vapor compression refrigeration cycle diagram shown on the Mollier diagram. Show the whole. That is, the "pressure in the evaporator (4)" refers to the pressure between the outlet side of the pressure reducing device (3) for the refrigeration cycle and the suction side of the compressor.

In the invention described in claim 2, the valve body (35)
Is disposed in the space on the side of the outflow port (33) and is provided by an elastic member (36) that generates an elastic force.
It is characterized in that it is pressed toward the space on the side 2). Thereby, as will be described later, the pressure reduced by the pressure reducing device (3) for the refrigeration cycle, that is, the pressure difference (Δ
P) can be adjusted by adjusting the elastic force of the elastic member (36). Therefore, as compared with an electric control unit that adjusts the opening degree of the valve port (34) using a pressure sensor, a proportional control solenoid valve, or the like, the refrigeration cycle decompression device 3
The structure can be simplified, and an increase in the manufacturing cost of the decompression device 3 can be prevented.

In the invention described in claim 3, carbon dioxide is used as the refrigerant, and the predetermined pressure difference (ΔP) is
It is characterized in that it is 5.5 to 7 MPa . The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the specific means described in the embodiments to be described later.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention shown in the drawings will be described. (First Embodiment) FIG. 1 is a CO using a decompression device for a refrigeration cycle (hereinafter referred to as a decompression device) 3 according to the present embodiment.
_Two cycles are applied to a vehicle air conditioner.
Is a compressor that compresses CO ₂ in a gas phase by obtaining driving force from an engine (not shown). Reference numeral 2 is a radiator (gas cooler) that cools CO ₂ compressed by the compressor 1 by exchanging heat with the outside air, and 3 is decompressed high-pressure (about 12 MPa) CO ₂ flowing out from the radiator 2. It is a pressure reducing device.

The decompression device 3 serves as a decompression device and also has a function of controlling the outlet side pressure of the radiator 2 as described later, and the CO decompressed by the decompression device 3 is also provided.
₂ enters a vaporizer 4 described later in a gas-liquid two-phase state. Reference numeral 4 denotes an evaporator (heat absorber) that serves as a cooling means for the air blown into the vehicle interior. When CO ₂ in a gas-liquid two-phase state is vaporized (evaporated) in the evaporator 4, latent heat of vaporization from the vehicle interior air is removed. Take it away and cool the cabin air. 5 separates CO ₂ in the vapor phase from CO ₂ in the liquid phase, and
It is an accumulator that temporarily stores ₂ . In addition,
Cooling fans 6 and 7 promote heat exchange between the radiator 2 and the evaporator 4.

The compressor 1, the radiator 2, the decompression device 3, the evaporator 4 and the accumulator 5 are connected by pipes to form a closed circuit. The radiator 2 is arranged in front of the vehicle in order to maximize the temperature difference between the CO 2 inside the radiator ₂ and the outside air. Next, the decompression device 3 will be described in detail (see FIG. 2).

Reference numeral 31 denotes an inlet 32 communicating with the radiator 2.
And a housing made of metal such as stainless steel or brass in which an outlet 33 communicating with the evaporator 4 is formed. In the housing 31, a space 32a on the inlet 32 side and a space 33a on the outlet 33 side are formed. A valve port 34 for communication is formed. Further, a valve body 35 for adjusting the opening degree of the valve opening 34 is arranged in the space 33a, and the valve body 35 is provided with a coil spring (elastic member) 36 made of a metal.
It is pressed toward the side space 32a.

The housing 31 is the housing 31.
Part (lid part) 31a in which the outlet 33 is formed
And a portion (bottom) 31b where the inlet 32 is formed
And a cylindrical main body portion 31c, the bottom portion 31b and the main body portion 31c are integrally formed, and the lid portion 31a stores the valve body 35 and the coil spring 36 in the housing 31. It is connected to the housing 31 by a connecting means such as welding or screw connection.

Reference numeral 37 is a guide skirt that guides the movement of the valve body 35 in the housing 31, and the cylindrical outer surface 37a of the guide skirt 37 comes into contact with the inner wall 31d of the housing 31. Disc 3
The movement of 5 is guided. In addition, the guide skirt 3
7, a plurality of holes 37b forming a flow path for CO ₂ are formed in the vicinity of the valve element 35.

Next, the operation of the decompression device 3 will be described. As is apparent from FIG. 2, on the side of the inlet 32 of the valve element 35,
Since the acting force F ₁ due to the outlet side pressure of the radiator 2 acts, the valve element 35 is pressed toward the outflow port 33 side. On the other hand, the inlet side pressure of the evaporator 2 and the acting force F ₂ due to the elastic force of the coil spring 36 act on the outlet 33 side, so that the valve body 3
5 is pushed toward the inlet 32 side.

That is, when the acting force F ₂ is larger than the acting force F ₁ , the valve body 35 moves so that the opening of the valve opening 34 becomes smaller, and the acting force F ₁ is larger than the acting force F _2. In this case, the valve element 35 moves so that the opening degree of the valve opening 34 increases (see (b) of FIG. 2). Therefore, the valve body 35
Stops at a position where the acting force F ₁ and the acting force F ₂ are in balance (or a position where the acting force F ₂ contacts the valve opening 34), the valve opening 3
The opening degree of 4 is determined by the elastic force exerted on the valve body 35 by the coil spring 36. That is, the pressure difference ΔP between the spaces 32 a and 33 a corresponds to the elastic force exerted by the coil spring 36 on the valve body 35.

Since the movement amount (lift amount) of the valve body 35 is small, the change in the elastic force exerted on the valve body 35 by the coil spring 36 can be almost ignored.
The pressure difference ΔP between a and 33a is substantially constant. In addition,
In the present embodiment, the opening degree of the valve opening 34 indicates the distance t between the valve opening 34 and the valve body 35.

Next, the operation of the CO ₂ cycle according to this embodiment will be described. FIG. 3 is a Mollier diagram showing the operation of the CO ₂ cycle according to the present embodiment. In FIG. 3, the dashed-dotted line diagram A shows the case where the refrigerating capacity (heat load) is small,
The solid line diagram B shows the case where the heat load is large. For example, when the indoor air temperature is high, such as in the summer, the temperature of the air cooled by the evaporator 4 also rises, so the temperature inside the evaporator 4 rises and the pressure inside the evaporator 4, that is, CO ₂
Evaporating pressure increases.

As a result, the acting force F ₂ becomes large and the opening of the valve port 34 becomes small as described above.
The outlet side pressure rises (state of diagram B). Therefore, as shown in FIG. 3, the specific enthalpy difference between the outlet and the inlet of the evaporator 4 becomes large (h ₁ > h ₂ ), so that the refrigerating capacity is increased. On the other hand, on the contrary, when the room temperature is low such as in spring or autumn, the temperature of the air cooled by the evaporator 4 is also low,
As the temperature inside the evaporator 4 decreases, the pressure inside the evaporator 4, that is, the evaporation pressure of CO ₂ also decreases.

For this reason, the acting force F ₂ becomes small, and the opening of the valve port 34 becomes large as described above.
The pressure on the outlet side of is decreased (state of diagram A). Therefore, as shown in FIG. 3, the difference in specific enthalpy between the outlet and the inlet of the evaporator 4 becomes small, so that the refrigerating capacity decreases. Next, the pressure difference ΔP will be described.

When the temperature in the evaporator 4 becomes below freezing (0 ° C. or lower), frost is generated in the evaporator 4 and the refrigerating capacity of the evaporator 4 is deteriorated. Therefore, the temperature in the evaporator 4 is lower than the freezing point. It is desirable to raise it. However, if the temperature inside the evaporator 4 is unnecessarily raised, there arises a problem that the air blown into the vehicle compartment cannot be sufficiently cooled. Therefore, the inventors conducted various tests, and found that the temperature inside the evaporator 4 was about 17 ° C. at maximum and the pressure inside the evaporator 4 (CO ₂ evaporation pressure) was about 3.5 to 5. It was concluded that 5 MPa (hereinafter referred to as low pressure side pressure) is appropriate. Then, the inventors tried the following examinations in order to determine the outlet side pressure of the radiator 2 (hereinafter referred to as the high pressure side pressure) based on the low pressure side pressure.

That is, the graph of FIG. 4 shows the results of calculating the coefficient of performance (COP) of the CO ₂ cycle with respect to the high pressure side pressure, with the low pressure side pressure being constant (3.5 MPa). As is clear from this result, the COP is extremely deteriorated when the high-pressure side pressure is 9 MPa or lower and 12.5 MPa or higher, so it is desirable to keep the high-pressure side pressure at 9 to 12.5 MPa. That is, it is desirable that the pressure difference ΔP be 5.5 to 7 MPa.

The coefficient of performance (COP) is, as is well known, a value obtained by dividing the enthalpy difference (refrigerating capacity) between the outlet and the inlet of the evaporator 4 by the compression work of the compressor 1. The efficiency was 65%. Here, when the pressure difference ΔP is 6.0 MPa and the low pressure side pressure is 3.5 MPa (about 0 ° C. at the temperature inside the evaporator 4), the high pressure side pressure is 9.5 MPa. Therefore, the specific enthalpy difference between the outlet and the inlet of the evaporator 4 is about 111 kJ / kg, and the CO ₂ density at the inlet of the compressor 1 is about 96.3 kg / m ³ (see FIG. 6).

When the heat load increases and the low pressure side pressure rises to 5 MPa, the high pressure side pressure becomes 11 M
The temperature rises to Pa (about 13 ° C. at the temperature inside the evaporator 4). Therefore, the specific enthalpy difference between the outlet and the inlet of the evaporator 4 is about 121.5 kJ / kg, and the CO at the inlet of the compressor 1
_{2 The} density is about 151.5 kg / m ³ (see FIG. 6).
Therefore, the low pressure side pressure is 3.5MPa to 5MP
By increasing the temperature to a, the refrigerating capacity of the evaporator 4 becomes about 1.7 times.

As described above, according to the present embodiment, a simple means for adjusting the opening of the valve port 34 so that the pressure difference ΔP between the high pressure side pressure and the low pressure side pressure becomes a predetermined value. Thus, the CO ₂ cycle can be controlled. Further, the pressure difference ΔP is determined by the coil spring 3 in the pressure reducing device 3.
Since the setting can be controlled by the pressure reducing device 6, the structure of the pressure reducing device 3 is simpler than that of the electric control means that adjusts the opening degree of the valve opening 34 by using a pressure sensor, a proportional control solenoid valve, or the like, and the pressure reducing device is reduced. It is possible to prevent the manufacturing cost increase of item 3 above.

(Second Embodiment) In this embodiment, the valve element 35 is used.
The elastic force of the coil spring 36 acting on is adjustable. Below, it demonstrates using FIG. 40 is disposed on one end side of the coil spring 36, and the elastic force of the coil spring 36 is applied to the needle-shaped valve body 35 by pressure so as to flow out from the outlet 33.
The first pressing plate 41 acts from the side, and 41 is a second pressing plate that is arranged on the other end side of the coil spring 36 and adjusts the elastic force of the coil spring 36. This second pressing plate 41
A female screw portion 41a is formed on the male screw portion 41a, and a male screw portion 42a formed on an adjusting shaft 42 for moving the second pressing plate 41 in the axial direction of the coil spring 36 is screwed to the female screw portion 41a.

Therefore, since the second pressing plate 41 moves in the axial direction of the coil spring 36 in association with the rotation of the adjusting shaft 42, the elastic force acting on the valve body 35 can be adjusted. Reference numeral 43 is a key that prevents the second pressing plate 41 from rotating together with the adjustment shaft 42, and 44 is an O-ring made of nitrile rubber that forms a seal member that seals the gap between the adjustment shaft 42 and the housing 31. is there.

Incidentally, the CO ₂ cycle has a high pressure side pressure (about 8 times) higher than that of a normal vapor compression refrigeration cycle using CFCs. Therefore, when a seal member such as an O ring is provided in the movable part. As described above, it is desirable that the is disposed on the outlet 33 side, which is after decompression. by the way,
Although the pressure difference ΔP is mechanically controlled by using the coil spring 36 in the above-described embodiment, the evaporator 4 is controlled by the pressure sensor.
The present invention can also be implemented by using an electric actuator capable of detecting the internal pressure and adjusting the valve opening degree based on the detected value, such as a proportional control solenoid valve.

Further, since the pressure and the temperature have a relationship as shown by the isotherm of the Mollier diagram, a temperature sensor may be used instead of the pressure sensor. In this case, the pressure sensor may detect the pressure at the outlet side or the inlet side of the evaporator 4 or anywhere in the evaporator 4. However, when the pressure loss in the evaporator 4 is large and the pressure is detected at the outlet side of the evaporator 4, it is necessary to compensate for the pressure loss. Similarly, when using the temperature sensor, it is necessary to consider the temperature change from the inlet side to the outlet side of the evaporator 4.

Further, in the above-described embodiment, the valve body 35 has a C
Although the pressure of CO ₂ circulating in the O ₂ cycle was directly applied, the pressure inside the evaporator 4 or at the outlet side or the inlet side of the evaporator 4 is taken out by a thin tube or the like, and the valve body 35 is opened via a diaphragm or the like. It may be activated. Further, the decompression device 3 according to the present invention is not limited to use in a vapor compression refrigeration cycle using CO _2, and uses, for example, a refrigerant used in a supercritical region such as ethylene, ethane, and nitric oxide. It can also be applied to a conventional vapor compression refrigeration cycle.

Further, even if the accumulator 5 is eliminated, the vapor compression refrigeration cycle can be carried out.
In this case, the refrigerant remaining in the evaporator 4 is sucked, and the same operation as in the CO ₂ cycle having the accumulator 5 can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a CO ₂ cycle according to a first embodiment.

FIG. 2 is a cross-sectional view of the pressure reducing device according to the first embodiment.

FIG. 3 is a Mollier diagram for explaining the CO ₂ cycle according to the first embodiment.

FIG. 4 is a graph showing the relationship between high pressure side pressure and coefficient of performance (COP).

FIG. 5 is a cross-sectional view of a pressure reducing device according to a second embodiment.

FIG. 6 is a Mollier diagram for explaining the CO ₂ cycle.

[Explanation of symbols]

1 ... Compressor, 2 ... Radiator, 3 ... Pressure reducing device, 4 ... Evaporator,
5 ... Accumulator, 31 ... Housing, 32 ... Inflow port, 33 ... Outflow port, 34 ... Valve opening, 35 ... Valve body, 36 ... Coil spring (elastic member).

─────────────────────────────────────────────────── ───Continued from the front page (56) Bibliography Sho 59-25756 (JP, U) Shokoku 47-14305 (JP, Y1) Tokuhei 3-503206 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) F25B 41/06

Claims (3)

(57) [Claims] 1. A compressor for compressing a refrigerant (1), the heat radiation for cooling the refrigerant compressed by the compressor (1)
And a pressure reducing device for reducing the pressure of the refrigerant flowing out from the radiator (2).
(3) and an evaporator for evaporating the refrigerant decompressed by the decompression device (3)
(4) and the pressure inside the radiator (2) exceeds the critical pressure of the refrigerant.
A gas compression refrigeration cycle, comprising the pressure reducing device (3).
Is an inlet (32) communicating with the radiator (2), and
And an outlet (33) communicating with the evaporator (4) is formed.
Has a housing (31) that is located inside the housing (31) on the side of the inlet (32).
The space (32a) and the space (33) on the side of the outlet (33)
A valve opening (34) for communicating with a ) is formed, and the valve body (35) for adjusting the opening of the valve opening (34) is
The valve body (35) is provided in the housing (31), and the valve body (35) has a pressure inside the evaporator (4) so that a pressure difference between the spaces (32a, 33a) becomes a predetermined pressure difference (ΔP). A vapor compression refrigeration cycle characterized in that the opening of the valve opening (34) is controlled in accordance with the above. 2. The valve body (35) has the outlet (3).
3) side while being positioned in the space, to claim 1, characterized in that it is pressed toward the space of the inlet (32) side by the elastic member (36) for generating an elastic force serial
The vapor compression refrigeration cycle described above . 3. The vapor compression type according to claim 1, wherein the refrigerant is carbon dioxide, and the predetermined pressure difference (ΔP) is 5.5 to 7 MPa.
Refrigeration cycle .