JP2001235239A - Supercritical vapor compressing cycle system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a cooling efficiency by suitably heat exchanging a supercritical high pressure vapor phase refrigerant passed through a radiator with a low pressure vapor phase refrigerant separated by an accumulator by an inner heat exchanger 3 and to prevent a rise of a compressor discharge temperature and a rise of a radiator outlet pressure due to excess heat exchanging. SOLUTION: A bypass passage 7 is provided in parallel with a heat exchanger 3b of a low pressure of the inner heat exchanger 3. A vapor phase refrigerant flow rate of the passage 3b of the low pressure side and a vapor phase refrigerant flow rate of the passage 7 are respectively controlled by flow rate control valves 9, 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention provides a car air conditioner that uses refrigerant of CO ₂ or the like, not condense on the high pressure side, the air-conditioning apparatus, a supercritical vapor compression cycle device of the heat pump or the like.

[0002]

2. Description of the Related Art In recent years, in order to prevent pollution of the global environment, in particular, destruction of the ozone layer and global warming, carbon dioxide (CO ₂ ), which has much less influence than fluorocarbon, has been used as a refrigerant for car air conditioners and the like. Research and development of a supercritical vapor compression cycle device that uses methane is underway.

[0003] Japanese Patent Publication No. 7-18602 discloses a supercritical vapor compression cycle device capable of adjusting and controlling the capacity. An outline of this supercritical vapor compression cycle device will be described with reference to FIG. 10. A compressor 1 compresses a refrigerant to a supercritical state, radiates and cools the compressed refrigerant by a radiator 2, and cools the internal heat exchanger. (Counter-flow type heat exchanger) After passing through the heat exchange passage 3a on the high pressure side of 3 to further reduce the temperature, it is expanded by the expansion valve 4 to reduce the pressure, and the evaporator 5 evaporates by heat absorption from the outside. (Liquid Separator) The liquid refrigerant is stored in a liquid separator 6 and separated into a gas-liquid two-phase.
And returns to the compressor 1 through the heat exchange passage 3b on the low pressure side. By the heat exchange of the internal heat exchanger 3, the refrigerant temperature on the high pressure side is further lowered, and the cooling capacity is improved. And the above-mentioned Tokuhei 7
In Japanese Patent No. -18602, the capacity of the system is further adjusted and controlled by adjusting the flow rate of the refrigerant in the system with the expansion valve 4 or a separately provided throttle valve.

Referring to the Mollier diagram of FIG. 12, FIG.
Explaining the relationship between the temperature and the pressure of the supercritical vapor compression cycle device described above, the compressor 1 increases the pressure from point A to point B, and at that time, the temperature also increases. The radiator 2 lowers the temperature from point B to point C while maintaining the pressure of the refrigerant.

[0005] Here, if the refrigerant is expanded by sending the refrigerant directly from the point C to the expansion valve 4, the pressure decreases and the pressure decreases as shown in FIG.
To move to point E 'just below point C. In the next evaporator 5, E '
Heat absorption from the point to the intersection F with the saturated vapor pressure line S is performed. The internal heat exchanger 3 lowers the temperature of the refrigerant passing through the high-pressure side heat exchange passage 3a from point C to point D,
By moving the point E 'to the point E, the amount of heat absorbed in the evaporator 5 is increased, the refrigeration effect is increased, and the efficiency is improved.

[0006] After passing through the evaporator 5 and the accumulator 6, F
The refrigerant at the point is the low pressure side heat exchange passage 3 of the internal heat exchanger 3.
Through b, it is heated by the heat radiation on the high-pressure side heat exchange passage 3a side, the temperature rises, and reaches the point A.

The temperature increase FA in the low-pressure side heat exchange passage 3b is not always preferable for the compressor 1. The refrigerant discharge temperature of the compressor 1 rises substantially in proportion to FA. In particular, when the heat load is large, the discharge temperature rises with an increase in pressure, and in addition, when the heat exchange amount of the internal heat exchanger 3 increases (CD, FA), the discharge temperature further increases. turn into.

An excessive rise in the temperature of the refrigerant at the outlet of the compressor 1 due to these causes the compressor 1 to be damaged, such as poor lubrication and poor sealing of the compressor 1.

In general, when the pressure on the high pressure side is increased, the cooling capacity is improved. However, increasing the pressure on the high pressure side requires more power for the compressor. The relationship between the cooling capacity / power ratio, the so-called coefficient of performance COP, and the radiator outlet pressure is shown in a diagram as shown in FIG. 11, in which the COP increases as the radiator outlet pressure on the high pressure side increases. As the vessel outlet pressure exceeds the limit, the COP gradually begins to decrease. That is, the COP has a peak value. As shown in the figure, the peak value of the COP changes depending on the radiator outlet temperature. As the radiator outlet temperature increases, the peak value of the COP decreases, and at the same time, the radiator outlet pressure at the peak value increases. I do.

Therefore, it is required to change the radiator outlet pressure in accordance with the radiator outlet temperature and to operate the supercritical vapor compression cycle device so that the COP has a peak value. The same can be said for the case where an internal heat exchanger is used. When such a cycle operation is performed, an excessive rise in the discharge temperature causes the outlet temperature of the radiator 2 to rise,
The point of intersection C with the isotherm I is shifted to the right (the point of intersection with the isotherm (not shown) that is higher than the isotherm I shown in the figure), and accordingly, the outlet temperatures on the high pressure side and the low pressure side of the internal heat exchanger 3 accordingly. As a result, the effect of improving the cooling efficiency of the internal heat exchanger 3 is hindered, and a vicious cycle of further increasing the high-pressure side pressure at the radiator outlet or the like also occurs.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and appropriately exchanges heat between a supercritical high-pressure refrigerant discharged from a compressor and a low-pressure refrigerant vaporized in an evaporator in an internal heat exchanger. The present invention provides a supercritical vapor compression cycle device that improves cooling efficiency and prevents a rise in compressor discharge temperature and a rise in radiator outlet pressure due to excessive heat exchange.

[0012]

In order to solve the above-mentioned problems, the present invention provides a compressor for compressing a refrigerant heated to a predetermined degree of superheat to a supercritical state, and a refrigerant compressed by the compressor. A radiator for radiating heat and cooling, and an internal heat exchanger for introducing the supercritical high-pressure refrigerant radiated by the radiator into the high-pressure side heat exchange passage and exchanging heat with the low-pressure refrigerant in the low-pressure side heat exchange passage. An expansion valve that reduces the pressure of the supercritical high-pressure refrigerant that has passed through the heat exchange passage on the high-pressure side, and a low-pressure refrigerant that is expanded and decompressed by the expansion valve and gas-liquid two-phase is introduced to evaporate by heat absorption from the outside. A supercritical vapor compression cycle device, wherein the low-pressure refrigerant that has passed through the evaporator is introduced into the heat exchange passage on the low-pressure side to exchange heat, and then sent to the compressor. Parallel to the heat exchange passage on one side of the heat exchanger A bypass passage is provided, it is to control the refrigerant flow rate of the coolant flow and the bypass passage of the heat exchange passages on one side by the flow rate control valve.

The flow control valve may be provided in both the flow path on the one-side heat exchange passage and the bypass passage, or may be further provided between the middle of the one-side heat exchange passage and the bypass passage. By providing the bypass passage of (1) and providing the third flow control valve in the second bypass passage, it is easy to control the flow rate of the refrigerant in the heat exchange passage and the flow rate of the refrigerant in the bypass passage.

If a heat exchange passage on the low pressure side is used as the heat exchange passage on the one side, the thermal and pressure loads applied to the flow control valve, the pipe joint and the like are small, so that the reliability is further improved.

The opening and closing of the flow control valve is adjusted based on the outlet temperature of the compressor corresponding to the source flow of the radiator, that is, the temperature of the refrigerant discharged from the compressor, rather than the adjustment based on the radiator outlet temperature. This is preferable because a change in the outlet temperature can be detected in advance and a response delay hardly occurs.

The temperature and pressure of the refrigerant at the outlet and the inlet of the internal heat exchanger, or the temperature and load information of the evaporator are added to the outlet temperature of the compressor, and based on these, the flow control valve is controlled. Opening and closing can be adjusted, and in this case, a supercritical vapor compression cycle device with more excellent adaptability can be obtained.

In the present invention, the amount of heat exchange in the internal heat exchanger is appropriately controlled to prevent excessive heat exchange, and the heat exchange in the internal heat exchanger is performed so that the outlet pressure of the radiator becomes the peak value of COP. To improve the cooling efficiency and prevent the compressor discharge temperature from rising due to excessive heat exchange.

The flow control valve in the present invention is
An N / OFF control type, a stepless opening / closing degree control type, or a combination thereof can be appropriately selected. Also,
A valve combining a plurality of valves such as a three-way valve can also be used.

The load information according to the present invention is defined as the thermal load applied to the supercritical vapor compression cycle device, such as the outside air temperature, the indoor temperature, the set indoor temperature, the amount of solar radiation, or the case where the engine is used as the rotational power of the compressor. Means information on the engine speed, accelerator opening, and the like.

[0020]

Embodiments of the present invention will be described below.
This will be described with reference to the drawings.

[First Embodiment] FIG. 1 is an explanatory diagram showing one embodiment of the present invention. The supercritical vapor compression cycle device of FIG. 1 is a device in which a bypass is formed in the internal heat exchanger of the supercritical vapor compression cycle device shown in FIG. 10, and the other components are the same. And description thereof is omitted.

In FIG. 1, a bypass 7 is provided in parallel with the heat exchange passage 3b on the low pressure side of the internal heat exchanger 3, and a flow path between one of the heat exchange passages 3b on the low pressure side and the outlet of the accumulator 6 is provided. A first flow control valve 9 is provided at 8, and a second flow control valve 10 is provided at the bypass 7.

A temperature sensor 11 is provided at a discharge port of the compressor 1 from which the refrigerant compressed to the supercritical state is discharged, and the temperature sensor 11 detects a temperature of the refrigerant discharged from the compressor 1. Reference numeral 12 denotes a control unit (control unit) that sends a control signal to the flow control valves 9 and 10 based on the temperature detected by the temperature sensor 11.

The first and second flow control valves 9, 10
As the method, a flow control valve of a stepless opening / closing control type capable of continuously adjusting the opening from full open to fully closed is used. In addition,
It is also possible to use an ON / OFF control type flow control valve having only an opening and closing without an intermediate opening.

As the heat exchange passages 3a and 3b, use is made of a double tube in which the heat exchange passage 3a on the high pressure side is covered by the heat exchange passage 3b on the low pressure side.

The control operation of the supercritical vapor compression cycle device shown in FIG. 1 will be described below.

[Explanation of Supercritical Vapor Compression Cycle] The supercritical state (state of FIG. 12B) where the compressor 1 exceeds the critical pressure of the refrigerant heated to a predetermined degree of superheat (state of FIG. 12A). ), And the supercritical high-pressure refrigerant discharged from the compressor 1 is introduced into the radiator 2 to radiate heat (state C in FIG. 12). The supercritical high-pressure refrigerant that has passed through the radiator 2 is introduced into the high-pressure side heat exchange passage 3a of the internal heat exchanger 3, and heat-exchanges with a low-pressure refrigerant in a low-pressure side heat exchange passage 3b, which will be described later. Lower (state D in FIG. 12). Due to this temperature decrease, the cooling efficiency is improved.

Heat exchange passage 3a on the high pressure side of internal heat exchanger 3
Is introduced into the expansion valve 4 to expand and reduce the pressure. In this process, cross the saturated vapor pressure line S,
The refrigerant becomes a gas-liquid two-phase (state of E in FIG. 12). The low-pressure refrigerant that has been expanded and decompressed and converted into a gas-liquid two-phase is introduced into the evaporator 5 and evaporated by absorbing heat from the outside, thereby cooling the outside (the state of F in FIG. 12).

The low-pressure refrigerant that has passed through the evaporator 5 is collected in the accumulator 6 and separated into a gas phase and a liquid phase. The gas-phase refrigerant is further transferred to the heat exchange passage 3 b on the low pressure side of the internal heat exchanger 3. The heat is introduced and heat exchanged, and used for cooling the refrigerant on the high pressure side. In this process, the refrigerant exceeds the saturated vapor pressure line S, and the refrigerant is heated to a predetermined degree of superheat (state A in FIG. 12).

Thereafter, this cycle is repeated.

[Explanation of heat exchange control in internal heat exchanger]
The temperature of the refrigerant discharged from the compressor 1 detected by the temperature sensor 11 is sent to the control unit 12, and the control unit 12 controls the flow control valve based on the detected temperature (the temperature of the refrigerant discharged from the compressor). A control signal is sent to 9 and 10. The openings of the flow control valves 9 and 10 are respectively adjusted in accordance with the control signals, and heat exchange is performed so as to lower the temperature on the high pressure side as much as possible without increasing the temperature on the low pressure side excessively.

The flow control valve 9 in the flow path 8 connected to the low pressure side heat exchange passage 3b is fully opened, and the opening degree of the flow control valve 10 in the bypass path 7 is adjusted so that the low pressure side heat exchange passage 3
b and the flow rate of the refrigerant in the bypass 7.
Alternatively, on the contrary, the flow rate control valve 10 of the bypass path 7 is fully opened, and the flow rate is controlled by adjusting the opening degree of the flow rate control valve 9 of the flow path 8. In the former state, when the flow control valve 10 of the bypass 7 is fully closed, the refrigerant flow rate in the heat exchange path 3b becomes 1
When the flow control valve 10 is opened, the refrigerant diverges according to the ratio of the fluid resistance between the heat exchange passage 3b side and the bypass passage 7 side. In the latter state, when the flow control valve 9 of the flow path 8 is fully closed, the refrigerant flow rate in the heat exchange passage 3b becomes 0% (no internal heat exchange), and when the flow control valve 9 is opened, the refrigerant flows into the heat exchange passage 3b and bypasses. The refrigerant diverges according to the ratio of the fluid resistance to the passage 7 side. For example, when the temperature of the refrigerant discharged from the compressor 1 rises significantly from the target value, the internal heat exchange is stopped by setting the refrigerant flow rate of the heat exchange passage 3b to 0%, and the refrigerant is entirely bypassed to the bypass passage 7. Thus, the compressor discharge temperature can be rapidly reduced.

As the flow control valves 9 and 10, ON / O
FIG. 2 shows a control flow when the FF control type flow control valve is used. The ON / OFF control type flow control valve is somewhat unsuitable for fine control, but the valve is inexpensive, the control system is simple, and can be used sufficiently for actual control.

The discharge temperature of the compressor 1 detected by the temperature sensor 11 is input to the control unit 12 at regular time intervals in step 201 of FIG. The control unit 12 compares the preset allowable discharge temperature with the input current discharge temperature (step 202), and if the current discharge temperature is equal to or higher than the allowable temperature,
Since the current discharge temperature is too high, which is undesirable for the compressor 1, the internal heat exchange is stopped by closing the flow control valve 9 on the internal heat exchanger 3 side and opening the flow control valve 10 on the bypass passage 7 (step). 203). In step 202, if the current discharge temperature is lower than the permissible temperature, the discharge temperature can be raised more than this, so that the flow control valve 9 on the internal heat exchanger 3 side is opened and the flow control valve on the bypass passage 7 is opened. 10 is closed and internal heat exchange is performed (step 204), and the temperature of the refrigerant at the high pressure side outlet of the internal heat exchanger 3 is reduced, and the cooling efficiency is increased. After the processing in step 203 or 204, the process returns to step 201 again.

As described above, in the supercritical vapor compression cycle device shown in FIG. 1, the amount of heat exchange in the internal heat exchanger 3 is controlled, and the low-pressure side refrigerant (FIG.
2) A) moderately superheat degree, prevent compressor damage,
In addition, the temperature of the refrigerant sent to the evaporator 5 is further reduced by the internal heat exchanger 3, so that the amount of heat absorbed by the evaporator 5 can be increased efficiently. The allowable value of the outlet temperature of the compressor is:
It is determined in advance by experiments or the like.

In FIG. 1, the first flow control valve 9
May be provided not on the upstream side of the heat exchange passage 3b on the low pressure side of the internal heat exchanger 3 but on the downstream side. Further, although the control range of the heat exchange amount is narrowed, only one of the first flow control valve 9 and the second flow control valve 10 is used, and the heat exchange passage 3b or the bypass passage 7 has a flow control valve. Even without the control valve, the heat exchange passage 3 is controlled by the control of the one flow control valve.
The flow rate of b can be adjusted.

[Embodiment 2] FIG. 3 shows an example in which one three-way solenoid valve 13 is used as two flow control valves. The same parts as those in the first embodiment of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Three-way solenoid valve 1
3 is provided at a branch point between the heat exchange passage 3b on the low pressure side from the accumulator 6 and the bypass passage 7, as shown in the figure. Alternatively, it may be provided at the junction of the low-pressure side heat exchange passage 3 b and the bypass passage 7. The three-way solenoid valve 13 is connected to the electromagnet O
By N / OFF, the heat exchange passage 3b or the bypass passage 7 on the low pressure side is opened, and the other is closed, and control is performed according to the flow according to FIG.

Third Embodiment FIG. 4 is an explanatory diagram showing another embodiment of the present invention. The supercritical vapor compression cycle device of FIG. 4 is different from the supercritical vapor compression cycle device of FIG. 1 in that a second bypass passage 14 is provided between the middle 3c of the low-pressure side heat exchange passage 3b and the bypass passage 7. A third flow control valve 15 is provided in the second bypass passage 14. The same parts as those in the first embodiment of FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 4, the first to third flow control valves 9, 10, and 15 are ON only for opening and closing without an intermediate opening.
A / OFF control type flow control valve is used. It should be noted that a flow rate control valve of a stepless opening / closing control type that can adjust the opening in a stepless manner from fully open to fully closed may be used.

The first to third flow control valves 9, 1
0 and 15 are controlled based on the temperature signal of the refrigerant discharged from the compressor 1 detected by the temperature sensor 11 similarly to the supercritical vapor compression cycle device of FIG.

A second bypass path 14 is provided, and the first to third
(A) The first flow control valve 9 is opened, the second flow control valve 10 and the third flow control valve 15 are used. Is closed, the entire amount of the refrigerant undergoes heat exchange in the total heat exchange passage of the internal heat exchanger 3, and the most heat exchange occurs. (B) The first flow control valve 9 and the second flow control valve If the 10 is closed and the third flow control valve 15 is opened, the whole amount of the refrigerant is the downstream half of the heat exchange passage half the distance of the internal heat exchanger 3 (the right half of FIG. 3c).
Heat exchange is performed, and the amount of heat exchange becomes about half of (a).
(C) If the first flow control valve 9 and the third flow control valve 15 are closed and the second flow control valve 10 is opened, the entire amount of the refrigerant passes through the bypass 7 and no internal heat exchange is performed. .

When a flow control valve that is only open / closed is used as the first to third flow control valves 9, 10, and 15, a step-like control is performed. However, similar to the supercritical vapor compression cycle device of FIG. The amount of heat exchange of the exchanger 3 is controlled, the degree of superheating of the low-pressure side refrigerant (A in FIG. 12) sent to the compressor 1 is appropriately suppressed to prevent damage to the compressor, and the amount of the refrigerant sent to the evaporator 5 is reduced. The temperature can be lowered by the internal heat exchanger 3 and the amount of heat absorbed by the evaporator 5 can be increased efficiently.

In FIG. 4, the same control can be performed even if the installation positions of the first to third flow control valves 9, 10, 15 are changed, for example, as follows.

The first flow control valve 9 is moved to the downstream side of the heat exchange passage 3b on the low pressure side, and the second flow control valve 10 is moved to the accumulator 6 in the bypass passage 7 upstream of the heat exchange passage 3b. The connection point of the flow control valve 15 with the bypass 7 is located downstream of the second flow control valve 10. In this case, if the flow control valve is only open / closed, heat is exchanged in the upstream half of the heat exchange passage 3b on the low pressure side, or heat is exchanged in the total heat exchange passage.

If a flow control valve capable of adjusting the opening degree is used, the amount of heat exchange can be controlled while finely adjusting the flow rate of the refrigerant upstream or downstream of the heat exchange passage 3b in a stepless manner.

In the above-described embodiment, the case where the internal heat exchange amount is controlled only by the information on the compressor discharge temperature has been described.

Next, a description will be given of an embodiment in which integrated control is performed in which control of the expansion valve and control of the amount of internal heat exchange are simultaneously controlled in accordance with the external heat load condition.

In each of the following embodiments in which the integrated control is performed, the inlet temperature, inlet pressure or outlet temperature, and outlet pressure of the internal heat exchanger are detected, and the pressure is controlled by the expansion valve. (Refer to FIG. 11) It is intended to realize a highly adaptive supercritical vapor compression cycle device capable of maintaining high efficiency in accordance with an operating environment such as an outside air temperature and a compressor rotation speed. In the following embodiments, the allowable value of the outlet temperature of the compressor is determined in advance by experiments or the like.

[Fourth Embodiment] FIG. 5 shows, in addition to the discharge temperature of the compressor in the first embodiment of FIG. 1, the high-pressure side of the internal heat exchanger 3 as information used for controlling the internal heat exchange amount. In the heat exchange passage 3a inlet, that is, in this embodiment,
The temperature and pressure of the refrigerant at the outlet of the radiator 2, the temperature of the evaporator 5 (near), the outside air temperature, the indoor temperature of the air conditioner,
The load information such as the set indoor temperature and the amount of solar radiation is detected, and the amount of internal heat exchange and the amount of throttle of the expansion valve are controlled based on the information. The same parts as those in the first embodiment of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. As the first and second flow control valves 9 and 10, stepless open / closed degree control type solenoid valves whose opening degrees can be freely adjusted,
Similarly, an electromagnetic valve whose opening can be freely adjusted is used for the expansion valve 4.

Reference numerals 16 and 17 denote a high-pressure inlet temperature sensor for detecting the temperature of the refrigerant at the inlet of the high-pressure heat exchange passage 3a of the internal heat exchanger 3, and a high-pressure inlet pressure sensor for detecting the pressure of the refrigerant. The evaporator temperature sensor detects the temperature of the vessel 5. These high-pressure inlet temperature sensors 16,
High pressure side inlet pressure sensor 17 and evaporator temperature sensor 1
The outputs of 8 are input to the control unit 12, respectively. Also,
Load information 19 such as the outside air temperature, the indoor temperature of the air-conditioning target, the set indoor temperature, and the amount of solar radiation is detected by a temperature sensor (not shown) or the like, and these are also input to the control unit 12.

In this embodiment, the optimal internal heat exchange amount according to the degree of the radiator 2 outlet temperature and outlet pressure, allowable discharge temperature, allowable high pressure side pressure, evaporator temperature, load information, etc. is experimentally determined. In addition, the control unit 12 controls the high-pressure side pressure by adjusting the opening of the expansion valve 4 so that an optimum COP is obtained with respect to the radiator outlet temperature in accordance with various data input. The opening degree of the first flow control valve 9 and the second flow control valve 10 is adjusted so that the internal heat exchange amount according to the degree of heat load such as information is obtained.

When the discharge temperature of the compressor 1 rises excessively and exceeds the allowable value, the control unit operates the first flow control valve 9.
Is closed, the second flow control valve 10 is fully opened, and the internal heat exchange is temporarily stopped.

[Fifth Embodiment] FIG. 6 shows an embodiment in which the temperature and pressure of the refrigerant at the inlet of the high-pressure side heat exchange passage 3a of the internal heat exchanger 3 in the embodiment of FIG. The detection of the temperature and the pressure of the refrigerant at the outlet of the high-pressure side heat exchange passage 3a is performed by the high-pressure outlet temperature sensor 20 and the high-pressure outlet pressure sensor 21. The same parts as those in the embodiment of FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. As the first and second flow control valves 9 and 10, stepless opening / closing control type solenoid valves whose opening degrees can be freely adjusted, and electromagnetic valves whose opening degrees can be freely adjusted similarly for the expansion valve 4. Use a valve.

Instead of detecting the temperature and pressure of the refrigerant at the inlet (exit of the radiator 2) of the high-pressure heat exchange passage 3a of the internal heat exchanger 3, the refrigerant at the outlet of the high-pressure heat exchange passage 3a of the internal heat exchanger 3 is used. If the temperature and pressure of the COP are detected, a graph according to FIG. 11 of the relationship between the outlet temperature of the high-pressure side heat exchange passage 3, the outlet pressure, and the COP is obtained. From this diagram, it is possible to control the pressure so that the COP becomes maximum according to the temperature at the outlet of the high-pressure side heat exchange passage 3a of the internal heat exchanger 3.

In this embodiment, the COP can be controlled to be high, but if the COP is optimized, the cooling power may be slightly insufficient. Therefore, for example, when the outside air temperature rises or the amount of solar radiation increases, a strong cooling power is required.
Temporarily deviate from the pressure control that results in OP and increase the pressure to a higher pressure to perform rapid cooling.

FIG. 7 is a flowchart showing the control flow of FIG. 5 or FIG.

In FIG. 7, at step 701, the discharge temperature of the compressor 1, the temperature and pressure of the inlet (outlet of the radiator 2) of the internal heat exchanger 3, and the evaporator 5
And load information such as the outside air temperature, the indoor temperature, the set indoor temperature, and the amount of solar radiation are input to the control unit 12 at regular time intervals. In step 702, the control unit 12 compares the preset allowable discharge temperature with the input current discharge temperature, and if the current compressor discharge temperature is equal to or lower than the allowable temperature, in step 703, Information from internal heat exchanger 3
Optimum values of the high pressure side pressure and the heat exchange amount at the inlet or outlet of the valve are calculated, and in step 704, the opening degrees of the expansion valve 4, the first and second flow control valves 9, 10 are determined based on the calculation results. Control.

In step 702, if the current compressor discharge temperature exceeds the allowable temperature, the current discharge temperature is too high,
Since it is not preferable for the compressor 1, in step 705, the amount of internal heat exchange for avoiding danger and the opening degree of the expansion valve 4 are calculated in consideration of the above various information, and in step 706, based on the calculation result, The opening of the expansion valve 4 and the first and second flow control valves 9 and 10 is controlled.

After the processing in step 704 or 706, the process returns to step 701 again.

[Sixth Embodiment] FIG. 8 shows the information used for controlling the internal heat exchange amount in addition to the discharge temperature of the compressor in the embodiment of FIG. Inlet of the high-pressure side heat exchange passage 3a of the heat exchanger 3, that is,
In this embodiment, the temperature and pressure of the refrigerant at the outlet of the radiator 2 and the temperature of (near) the evaporator 5 are detected, and the amount of internal heat exchange is controlled based on these information. 4 and FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. ON / OFF for the first, second and third flow control valves 9, 10 and 15
As the control type solenoid valve, and as the expansion valve 4, an electromagnetic valve whose opening can be freely adjusted is used.

The first, second and third flow control valves 9, 1
4, the first flow control valve 9: open, the second and third flow control valves 10, 15: closed, the second flow control valve 10: open, the first And the third flow control valves 9, 15: closed The third heat control valve 15: open, and the first and second flow control valves 9, 10: the internal heat exchange amount is controlled in three stages: closed.

It is of course possible to add the load information used in FIG. 5 or FIG. 6 to the embodiment of FIG. 8 for control.

[Seventh Embodiment] FIG. 9 shows an embodiment in which the temperature and pressure of the refrigerant at the inlet of the high-pressure side heat exchange passage 3a of the internal heat exchanger 3 in the embodiment of FIG. The detection of the temperature and pressure of the refrigerant at the outlet of the high-pressure side heat exchange passage 3a is performed by the high-pressure side outlet temperature sensor 20 and the high-pressure side inlet pressure sensor 21. The same parts as those in the embodiment of FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. First, second and third flow control valves 9, 10,
15 is an ON / OFF control type solenoid valve,
As the expansion valve 4, an electromagnetic valve whose opening can be freely adjusted is used.

Instead of detecting the temperature and pressure of the refrigerant at the inlet (exit of the radiator 2) of the high-pressure heat exchange passage 3a of the internal heat exchanger 3, the refrigerant at the exit of the high-pressure heat exchange passage 3a of the internal heat exchanger 3 is used. When the temperature and pressure of the COP are detected, the relationship between the temperature, the pressure and the COP at the outlet of the high-pressure side heat exchange passage 3 is
A diagram according to FIG. 12 is obtained. From this diagram, according to the temperature at the outlet of the high-pressure side heat exchange passage 3a of the internal heat exchanger 3,
Pressure can be controlled to maximize COP.

In this embodiment, the COP can be controlled to be high, but when the COP is optimized, the cooling power may be slightly insufficient. Therefore, for example, when the outside air temperature rises or the amount of solar radiation increases, a strong cooling power is required.
Temporarily deviate from the pressure control that becomes OP, and perform rapid cooling by increasing the pressure to a higher pressure.

The control of the amount of internal heat exchange is performed in three stages as in the embodiment of FIG.

In the embodiment shown in FIG. 9, it is also possible to control by further adding the load information used in FIG. 5 or FIG.

In the above embodiments, the bypass passage and the flow control valve are provided on the low-pressure side heat exchange passage 3b side. By doing so, the low pressure side can be reduced in pressure resistance of the pipeline, the flow control valve, and the like, which is preferable because the reliability of the apparatus is increased. However, it is preferable that the high pressure side heat exchange passage 3a has a bypass passage. Even if a flow control valve is provided, the operation and effect of the present invention can be similarly obtained.

[0069]

As described above in detail, according to the present invention, the bypass passage is provided in parallel with the heat exchange passage on one side of the internal heat exchanger, and the flow rate of the refrigerant in the heat exchange passage on one side is controlled by the flow control valve. Since the flow rate of the refrigerant in the bypass passage is controlled, the amount of heat exchange between the high-pressure side line through which the supercritical high-pressure refrigerant flows and the low-pressure side line through which the low-pressure refrigerant flows can be controlled in the range of 0 to 100%. As a result, efficient operation according to the heat load and the like can be performed, and an excessive rise in the discharge temperature of the compressor can be avoided, and damage to the compressor can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a control processing flow according to the embodiment of the present invention.

FIG. 3 is an explanatory view showing another embodiment of the present invention.

FIG. 4 is an explanatory view showing another embodiment of the present invention.

FIG. 5 is an explanatory view showing another embodiment of the present invention.

FIG. 6 is an explanatory view showing another embodiment of the present invention.

FIG. 7 is a flowchart showing a control processing flow in the embodiment of FIG. 5 or FIG. 6;

FIG. 8 is an explanatory view showing another embodiment of the present invention.

FIG. 9 is an explanatory view showing another embodiment of the present invention.

FIG. 10 is an explanatory view showing a conventional supercritical vapor compression cycle device.

FIG. 11 is a radiator outlet temperature / performance coefficient diagram showing the relationship between the radiator outlet temperature and the coefficient of performance in the supercritical vapor compression cycle.

FIG. 12 is a Mollier diagram showing a CO ₂ supercritical vapor compression cycle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Internal heat exchanger 3a Heat exchange passage on the high pressure side 3b Heat exchange passage on the low pressure side 4 Expansion valve 5 Evaporator 7 Bypass passage 9 First flow control valve 10 Second flow control valve 11 Temperature Sensor 12 Control unit 13 Three-way solenoid valve 14 Second bypass path 15 Third flow control valve 16 Internal heat exchanger high-side inlet temperature sensor 17 Internal heat exchanger high-side inlet pressure sensor 20 Internal heat exchanger high-side outlet temperature Sensor 21 Internal heat exchanger high pressure side outlet pressure sensor

Claims (9)

[Claims] 1. A compressor for compressing a refrigerant heated to a predetermined degree of superheat into a supercritical state, a radiator for radiating and cooling the refrigerant compressed by the compressor, and a radiator radiated by the radiator. An internal heat exchanger that introduces the supercritical high-pressure refrigerant into the heat exchange passage on the high-pressure side and exchanges heat with the low-pressure refrigerant in the heat exchange passage on the low-pressure side; and depressurizes the supercritical high-pressure refrigerant that has passed through the heat exchange passage on the high-pressure side. And an evaporator for introducing a low-pressure refrigerant that has been expanded and decompressed by the expansion valve and has been converted into a gas-liquid two-phase, and evaporates by absorbing heat from the outside. In the supercritical vapor compression cycle device, which is introduced into the heat exchange passage on the low pressure side and exchanges heat and then sent to the compressor, a bypass passage is provided in parallel with the heat exchange passage on one side of the internal heat exchanger. , Heat exchange on one side by flow control valve A supercritical vapor compression cycle device that controls a refrigerant flow rate in a passage and a refrigerant flow rate in a bypass passage. 2. The supercritical vapor compression cycle device according to claim 1, wherein a flow control valve is provided in each of the flow path on the one side heat exchange path side and the bypass path. 3. A method according to claim 1, wherein a second bypass passage is provided between an intermediate of said one side heat exchange passage and said bypass passage, and a third flow control valve is provided in said second bypass passage. 3. The supercritical vapor compression cycle device according to 2. 4. The supercritical vapor compression cycle device according to claim 1, wherein the one-side heat exchange passage is a low-pressure side heat exchange passage. 5. The supercritical vapor compression cycle device according to claim 1, wherein the opening and closing of the flow control valve is adjusted based on the temperature of the refrigerant discharged from the compressor. 6. The supercritical vapor compression cycle device according to claim 5, wherein the opening and closing of the flow control valve and the expansion valve are adjusted based on the temperature and pressure of the refrigerant at the outlet of the internal heat exchanger. 7. The supercritical vapor compression cycle device according to claim 5, wherein the opening and closing of the flow control valve and the expansion valve are adjusted based on the temperature and pressure of the refrigerant at the inlet of the internal heat exchanger. 8. The supercritical vapor compression cycle device according to claim 5, wherein the opening and closing of the flow control valve and the expansion valve are adjusted based on the temperature of the evaporator. 9. The supercritical vapor compression cycle device according to claim 5, wherein opening and closing of the flow control valve and the expansion valve are adjusted based on the load information.