Patent Application
20200271357
The present invention relates to a refrigeration cycle apparatus including a gas-liquid separator that reduces the quality of two-phase gas-liquid refrigerant flowing thereinto and then supplies the refrigerant to an evaporator.
In a hitherto known air-conditioning apparatus, liquid refrigerant condensed by an indoor heat exchanger provided to an indoor unit and serving as a condenser is decompressed by an expansion device provided at the outlet of the condenser and thus falls into a two-phase gas-liquid state in which gas refrigerant and liquid refrigerant both exist. The refrigerant in the two-phase gas-liquid state flows into an outdoor heat exchanger included in an outdoor unit and serving as an evaporator. If the quality of the two-phase gas-liquid refrigerant flowing into the outdoor heat exchanger serving as an evaporator is high, the amount of gas refrigerant that does not contribute to evaporation increases, worsening the heat-exchanging performance of the evaporator.
To reduce the quality of the refrigerant flowing into the evaporator in a heating operation, there is a technique in which a gas-liquid separator that separates refrigerant flowing thereinto in a two-phase gas-liquid state into gas refrigerant and liquid refrigerant is provided in the upstream of the evaporator so that the liquid refrigerant obtained through the separation is made to flow into the evaporator (see Patent Literature 1, for example). According to Patent Literature 1, the gas-liquid separator includes a container, an inflow pipe extending through a side wall of the container, a gas outflow pipe extending vertically through a central part of an upper wall of the container, and a gas outflow pipe extending through a bottom wall of the container. The two-phase gas-liquid refrigerant having flowed into the container swirls in the container. The swirling flow generates a centrifugal force acting on the refrigerant, whereby the refrigerant is separated into gas refrigerant and liquid refrigerant. The liquid refrigerant obtained through the separation accumulates at the bottom of the container and is discharged to the outside of the container through the liquid outflow pipe. The gas refrigerant is discharged to the outside of the container through the gas outflow pipe.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2014-211265
If major part of the refrigerant flowing into the container is liquid refrigerant, that is, if incoming refrigerant has a quality of 0.50 or lower, the following problem arises in the gas-liquid separator according to Patent Literature 1. Since the amount of liquid refrigerant included in the incoming refrigerant is large, the amount of liquid refrigerant that accumulates at the bottom of the container becomes large. Correspondingly, the gas-liquid interface is raised. Eventually, the gas-liquid interface comes close to a gas outlet positioned in the container, and the amount of liquid accidentally flowing into the gas outflow pipe from the gas outlet increases. Such a situation reduces the efficiency of gas-liquid separation. As a solution to such a problem, the distance between the gas-liquid interface and the gas outlet may be increased. In that case, however, another problem of increase in the size of the container arises.
The present invention is to overcome the above problems and provides a refrigeration cycle apparatus that realizes both improvement in the efficiency of gas-liquid separation and size reduction.
A refrigeration cycle apparatus according to an embodiment of the present invention includes a main circuit through which refrigerant circulates and in which a compressor, a condenser, a first expansion device, a centrifugal gas-liquid separator that separates refrigerant into gas refrigerant and liquid refrigerant by using centrifugal force, and an evaporator are connected by refrigerant pipes; and a bypass through which the gas refrigerant obtained through the separation by the gas-liquid separator is returned to a suction side of the compressor, wherein the gas-liquid separator includes a cylindrical container, an inflow pipe, a gas outflow pipe, and a liquid outflow pipe, wherein the main circuit includes a second expansion device provided between the liquid outflow pipe of the gas-liquid separator and the evaporator, and wherein the gas refrigerant discharged from the gas outflow pipe of the gas-liquid separator flows into the bypass, and the bypass is provided with a third expansion device.
In the refrigeration cycle apparatus according to the embodiment of the present invention, the first expansion device, the second expansion device, and the third expansion device are provided on a refrigerant inlet side and a refrigerant outlet side relative to the gas-liquid separator. Therefore; not only the refrigerant pressure in the gas-liquid separator but also the shape of a gas-liquid interface formed in the gas-liquid separator can be controlled. Hence, if the expansion devices are controlled such that the liquid refrigerant accumulated in the gas-liquid separator is not discharged from the gas outlet of the gas-liquid separator, the performance of gas-liquid separation can be improved without changing the size of the container. That is, the performance improvement of the gas-liquid separator and the size reduction of the container are both realized.
Embodiments of the refrigeration cycle apparatus including the same according to the present invention will now be described. Embodiments illustrated in the drawings are only exemplary and do not limit the present invention. Furthermore, like reference numerals used in the drawings denote like or corresponding elements, which applies throughout this specification. Furthermore, the elements illustrated in the drawings to be referred to below are not necessarily to scale. Furthermore, the levels of pressure and other factors are not defined by particular absolute values thereof but are each defined on the relative basis by the state, operation, or any other factors of a system, an apparatus, or any other devices relevant thereto.
The refrigeration cycle apparatus 200 according to Embodiment 1 forms a main circuit of a refrigerant circuit through which refrigerant circulates and in which a compressor 13, a four-way valve 14, an indoor heat exchanger 11, a second expansion device 22, a gas-liquid separator 10, and an outdoor heat exchanger 12 are connected by refrigerant pipes.
The gas-liquid separator 10 includes a cylindrical container 1. The container 1 is provided with an inflow pipe 2, a liquid outflow pipe 3, and a gas outflow pipe 4. The gas-liquid separator 10 separates two-phase gas-liquid refrigerant flowing thereinto from a first expansion device 21 into liquid refrigerant and gas refrigerant. Details of the gas-liquid separator 10 will be described separately below.
The refrigeration cycle apparatus 200 further includes a bypass 7 through which the gas refrigerant obtained through the separation by the gas-liquid separator 10 is returned to a suction side of the compressor 13. The bypass 7 is provided with the second expansion device 22. An end of the bypass 7 that is on the compressor suction side may be connected either to the pipe provided on the in downstream relative to an outlet header 6, to be described below, of the outdoor heat exchanger 12 as illustrated in
The refrigeration cycle apparatus 200 further includes a third expansion device 23 provided between the gas-liquid separator 10 and the outdoor heat exchanger 12 in the main circuit.
The first expansion device 21, the second expansion device 22, and the third expansion device 23 are each an expansion valve whose opening degree is adjustable. The expansion valve may be an electronic expansion valve in which the opening degree of a restrictor is variably adjustable by using a stepping motor (not illustrated). Hereinafter, the first expansion device 21, the second expansion device 22, and the third expansion device 23 are collectively denoted as the expansion devices 21 to 23 when all of them are mentioned.
The outdoor heat exchanger 12 includes an inlet header 5 and the outlet header 6 arranged at an interval therebetween. The outdoor heat exchanger 12 is a fin-tube heat exchanger including many heat exchanger tubes and fins provided between the headers. Distributors provided at the inlet and the outlet, respectively, of the outdoor heat exchanger 12 are not limited to such headers and may each be a distributor-type impact distributor.
The compressor 13, the second expansion device 22, the gas-liquid separator 10, the third expansion device 23, and the outdoor heat exchanger 12 are included in an outdoor unit 201. The indoor heat exchanger 11 and the first expansion device 21 are included in an indoor unit 202.
The refrigeration cycle apparatus 200 further includes a controller 203 that controls the entirety of the refrigeration cycle apparatus 200. The controller 203 may be configured either as a piece of hardware such as a circuit device that realizes relevant functions, or as a combination of an arithmetic device, such as a microcomputer or a CPU, and software to be executed thereon.
In the refrigeration cycle apparatus 200 configured as above, the outdoor heat exchanger 12 serves as a condenser, and the indoor heat exchanger 11 serves as an evaporator. The refrigeration cycle apparatus 200 is intended for, for example, an air-conditioning apparatus, a water heating apparatus, or any other like device. Embodiment 1 relates to a case where the refrigeration cycle apparatus 200 is used for an air-conditioning apparatus,
The number of outdoor units 201 is not limited to one, either. A plurality of outdoor units 201 may be provided. Furthermore, a plurality of indoor heat exchangers 11 may be provided, as long as the first expansion device 21 is provided to the refrigerant pipe provided between the gas-liquid separator 10 and the plurality of indoor heat exchangers 11. A multi-air-conditioning apparatus including a plurality of indoor units 202 is also applicable. Furthermore, the refrigerant pipe connecting the first expansion device 21 and the gas-liquid separator 10 to each other may be provided with a distribution controller that controls the distribution of refrigerant among the plurality of indoor units 202.
The refrigerant circulating through the refrigerant circuit is not particularly limited. However, any of refrigerants having a high gas density, such as R32, R410A, and CO2, is preferable because a great effect of improving the performance of the gas-liquid separator 10 can be obtained.
If olefin-based refrigerant such as R1234yf or R1234ze(E), HFC refrigerant such as R32, or hydrocarbon refrigerant such as propane or isobutane is used, the size of the container is reduced. Correspondingly, the amount of refrigerant to be contained therein is reduced. Olefin-based refrigerant such as R1234yf or R1234ze(E), HFC refrigerant such as R32, and hydrocarbon refrigerant such as propane or isobutane are flammable refrigerant. Therefore, the reduction in the amount of refrigerant to be contained leads to increased safety.
Now, an operation of the refrigeration cycle apparatus 200 according to Embodiment 1 will be described with reference to
High-temperature high-pressure refrigerant discharged from the compressor 13 flows through the four-way valve 14 and then flows into the indoor heat exchanger 11, where the refrigerant exchanges heat with air passing through the indoor heat exchanger 11, whereby the refrigerant turns into high-pressure liquid refrigerant and is discharged. The high-pressure liquid refrigerant discharged from the indoor heat exchanger 11 is decompressed by the first expansion device 21, thereby turning into two-phase gas-liquid refrigerant. The two-phase gas-liquid refrigerant flows through the inflow pipe 2 into the gas-liquid separator 10.
The two-phase gas-liquid refrigerant having flowed into the gas-liquid separator 10 is separated into liquid refrigerant and gas refrigerant. The liquid refrigerant is discharged from the liquid outflow pipe 3, is decompressed by the third expansion device 23, and flows through the inlet header 5 into the outdoor heat exchanger 12. The refrigerant having flowed into the outdoor heat exchanger 12 evaporates by exchanging heat with air, is merged with refrigerant flowing from the gas outflow pipe 4 in the outlet header 6 or at a position on the downstream side of the outlet header 6, and flows into the compressor 13 again. The gas refrigerant obtained through the separation by the gas-liquid separator 10 is discharged from the gas outflow pipe 4 into the bypass 7, flows through the second expansion device 22, and returns to the suction side of the compressor 13.
The gas-liquid separator 10 is a centrifugal gas-liquid separator and separates liquid and gas contained in gas-liquid mixed refrigerant from each other by generating a swirling flow of the gas-liquid mixed refrigerant in the container 1 and thus causing the liquid contained in the swirling flow to adhere to the inner peripheral surface of the container 1 with a centrifugal force. In the gas-liquid separator 10, the inflow pipe 2 is inserted through an upper part of the side wall of the container 1, with one end thereof being positioned inside the container 1 and the other end thereof being connected to the first expansion device 21. The inflow pipe 2 is shifted from a center line O of the container 1 so that the center line O does not meet the extension of part of the inflow pipe 2 that is positioned inside the container 1, The liquid outflow pipe 3 is connected to the bottom of the container 1, with a liquid outlet 3a at one end thereof being positioned in a central part of the bottom wall of the container 1. The gas outflow pipe 4 vertically is inserted through a central part of the upper wall of the container 1, with a gas outlet 4a at one end thereof being positioned inside the container 1 and the other end thereof being connected to the bypass 7.
In the gas-liquid separator 10 configured as above, the two-phase gas-liquid refrigerant having flowed into the container 1 swirls in the container 1. The swirling flow generates a centrifugal force acting on the refrigerant, whereby the refrigerant is separated into liquid refrigerant and gas refrigerant. That is, the difference between the centrifugal force acting on liquid refrigerant, which is relatively heavy, and the centrifugal force acting on gas refrigerant, which is relatively light, causes the two-phase gas-liquid refrigerant to be separated into the liquid refrigerant and the gas refrigerant. The liquid refrigerant flows from the liquid outlet 3a into the liquid outflow pipe 3 and is discharged to the outside of the container 1. The gas refrigerant flows from the gas outlet 4a into the gas outflow pipe 4 and is discharged to the outside of the container 1.
In the container 1, as illustrated in
In the container 1 of the gas-liquid separator 10, as illustrated in
If the distance between the gas-liquid interface 102 and the gas outlet 4a of the gas outflow pipe 4 is short, the liquid refrigerant flows into the gas outlet 4a from the liquid-main region 101. Consequently, the performance of gas-liquid separation is reduced. Therefore, the gas outlet 4a of the gas outflow pipe 4 and the gas-liquid interface 102 need to be at a satisfactory distance from each other so that accidental flowing of the liquid from the liquid-main region 101 into the gas outflow pipe 4 can be prevented.
In
As described above, the shape of the gas-liquid interface 102 depends on the inflow velocity, the quality, and the gas-liquid density ratio of the refrigerant. The inflow velocity and the quality are determined by the operating capacity of the air-conditioning apparatus and indoor-air conditions. In general, as illustrated in
Embodiment 1 is characterized in that the expansion devices 21 to 23 are provided on the refrigerant inlet side and the refrigerant outlet side relative to the gas-liquid separator 10. Since the opening degrees of the expansion devices 21 to 23 are individually controllable, the refrigerant pressure inside the container 1 is changeable arbitrarily, regardless of the difference between the high pressure and the low pressure in the refrigeration cycle, that is, regardless of the capacities of the condenser and the evaporator. Therefore, the shape of the gas-liquid interface 102 can be adjusted. If the refrigerant employed is, for example, R410A, the gas-liquid density ratio is adjustable in a range between twelvefold and sixtyfold. A specific method of controlling the opening degrees of the expansion devices 21 to 23 will be described separately in Embodiment 8.
As described above, the shape of the gas-liquid interface 102 is adjustable by controlling the opening degrees of the expansion devices 21 to 23 individually. Therefore, the opening degrees of the expansion devices 21 to 23 are adjusted such that a satisfactory distance is provided between the gas-liquid interface 102 and the gas outlet 4a of the gas outflow pipe 4. Thus, accidental flowing of the liquid from the liquid-main region 101 into the gas outflow pipe 4 is suppressed. Hence, the performance of gas-liquid separation can be improved.
To summarize, in the refrigeration cycle apparatus 200 according to Embodiment 1, since the expansion devices 21 to 23 are provided on the refrigerant inlet side and the refrigerant outlet side of the gas-liquid separator 10, not only the refrigerant pressure but also the gas-liquid density ratio in the gas-liquid separator 10 is adjustable. Therefore, the shape of the gas-liquid interface 102 in the gas-liquid separator 10 can be controlled. Hence, the performance of gas-liquid separation can be improved by controlling the expansion devices 21 to 23 such that the gas-liquid interface 102 has such a shape as to be at a satisfactory distance from the gas outlet 4a of the gas outflow pipe 4.
Furthermore, according to Embodiment 1, since the performance of gas-liquid separation can be improved without changing the size of the container 1, the performance improvement of the gas-liquid separator 10 and the size reduction of the container 1 are both realized. This contributes to cost reduction and prevents the occurrence of a problem that the gas-liquid separator 10 of a large size cannot be installed in a housing of a relevant product.
The refrigeration cycle apparatus 200 configured as illustrated in
In the modification of the refrigeration cycle apparatus 200 illustrated in
Embodiment 2 relates to the height-direction position of insertion of the inflow pipe 2 and the length of insertion of the gas outflow pipe 4 in the gas-liquid separator 10. The gas-liquid separator 10 and the refrigeration cycle apparatus 200 are configured as in Embodiment 1. Now, Embodiment 2 will be described, focusing on differences from Embodiment 1.
The gas-liquid separator 10 according to Embodiment 2 is designed such that the inflow pipe 2 and the gas outflow pipe 4 are positioned relative to the container 1 in the following dimensional relationships:
0.26H1≤L1≤0.65H1 (1), and
0.25H1≤L1−H2 (2)
where
L1: length of insertion of gas outflow pipe 4 from upper end of container 1 (hereinafter referred to as gas-outflow-pipe insertion length)
H1: container height
H2: vertical distance from upper end of container 1 to height-direction position of insertion of inflow pipe 2 (hereinafter referred to as inflow-pipe insertion height position)
That is, the gas-outflow-pipe insertion length L1 relative to the container height H1 is set to 0.26H1 or greater and 0.65 or smaller, and “L1−H2” expressing the height-direction distance from the height-direction position of insertion of the inflow pipe 2 to the gas outlet 4a of the gas outflow pipe 4 is set to greater than 0.25H1. Thus, high efficiency of gas-liquid separation can be obtained. The reasons for such a design will now be described.
As illustrated in
As the gas-outflow-pipe insertion length L1 is increased further, the gas-liquid-separation efficiency becomes lowest near a point of L1=H2. As the gas-outflow-pipe insertion length L1 is increased much further, the gas-liquid-separation efficiency sharply increases. The increasing gas-liquid-separation efficiency is substantially saturated at a point of L1>H2+0.25H1, and then sharply drops when L1 exceeds 0.65H1. This reduction in the gas-liquid-separation efficiency occurs because the gas outlet 4a of the gas outflow pipe 4 comes close to the gas-liquid interface 102 of the liquid-main region 101 at the bottom of the container 1, allowing the liquid to accidentally flow into the gas outflow pipe 4.
Considering the above changes in the gas-liquid-separation efficiency η that depend on the gas-outflow-pipe insertion length L1, it is understood that high gas-liquid-separation efficiency can be obtained if “L1−H2” expressing the height-direction distance from the height-direction position of insertion of the inflow pipe 2 to the gas outlet 4a of the gas outflow pipe 4 is set to greater than 0.25H1. Furthermore, if the gas-outflow-pipe insertion length L1 is set to L1≤0.65H1, high gas-liquid-separation efficiency η can be obtained.
As described above, if the positions of the inflow pipe 2 and the gas outflow pipe 4 relative to the container 1 are designed such that Expressions (1) and (2) above are satisfied, high gas-liquid-separation efficiency can be obtained.
To summarize, according to Embodiment 2, the advantageous effects obtained in Embodiment 1 can also be obtained. Furthermore, with a design satisfying “0.25H1<L1−H2”, that is, if “L1−H2” expressing the height-direction distance from the height-direction position H2 of insertion of the inflow pipe 2 to the gas outlet 4a of the gas outflow pipe 4 is set to greater than 0.25H1, the following advantageous effects are obtained. The liquid refrigerant flowing from the inflow pipe 2 into the container 1 does not directly flow into the gas outflow pipe 4 and can travel a required vertical entrance distance before reaching the liquid-main region 101 near the wall surface under the centrifugal force. Consequently, as illustrated in
Furthermore, if the gas-outflow-pipe insertion length L1 is set to 0.26H1 or greater, the swirling flow generated in the container 1 is prevented from striking upon the upper end of the container 1 and further bouncing therefrom to flow into the gas outflow pipe 4. Therefore, the amount of liquid refrigerant accidentally flowing into the gas outlet 4a of the gas outflow pipe 4 is reduced. Consequently, the performance of gas-liquid separation is improved.
Furthermore, if the insertion length L1 of the gas outflow pipe 4 is set to 0.65H or smaller, a distance of 0.35H or greater is provided between the gas outlet 4a of the gas outflow pipe 4 and the bottom surface of the container. That is, a satisfactory distance is provided between the gas outlet 4a of the gas outflow pipe 4 and the gas-liquid interface 102. Hence, suction of refrigerant from the liquid-main region 101 into the gas outflow pipe 4 can be prevented. Consequently, the performance of gas-liquid separation is improved.
Embodiment 3 relates to the dimensions of the inflow pipe 2 of the gas-liquid separator 10. The gas-liquid separator 10 and the refrigeration cycle apparatus 200 are configured as in Embodiment 1. Now, Embodiment 3 will be described, focusing on differences from Embodiment 1.
The gas-liquid separator 10 according to Embodiment 3 is designed with the following dimensional relationships:
0<Dinlet<0.71Gr0.5 (3), and
D
inlet
<D
bottle/2 (4)
where
Dbottle: inside diameter [mm] of container 1
Dinlet: in-pipe equivalent diameter [mm] of inflow pipe 2
Gr: refrigerant mass flow rate [kg/h] in rated heating operation
The in-pipe equivalent diameter is expressed as follows, using flow-path cross-sectional area Af and cross-sectional length L:
=4Af/L
As illustrated in
As Dinlet is made smaller, the effect of improving the performance of gas-liquid separation with the centrifugal force acting on the refrigerant flowing from the inflow pipe 2 into the container 1 becomes greater than the reduction in the performance of gas-liquid separation under the gravitational force acting on the refrigerant that has struck upon the wall surface of the container. Hence, the performance of gas-liquid separation is improved. Note that the lower limit of Dinlet needs to be greater than 0, because the inflow pipe 2 forms a flow path of the refrigeration cycle.
To summarize, according to Embodiment 3, the advantageous effects obtained in Embodiment 1 can also be obtained. Furthermore, since Dinlet is set such that Expressions (3) and (4) are satisfied, the performance of gas-liquid separation is further improved.
An experiment conducted by the inventors has demonstrated that an effect of improving the pressure capacity of the gas-liquid separator 10 can be obtained without increasing the size of the container but by reducing the in-pipe equivalent diameter Dinlet of the inflow pipe 2. In Embodiment 3, the in-pipe equivalent diameter Dinlet of the inflow pipe 2 designed to satisfy Expression (3) produces an effect of improving the pressure capacity of the gas-liquid separator 10. Therefore, the gas-liquid separator 10 can be provided on the high-pressure side of the refrigeration cycle. Accordingly, a refrigerant circuit illustrated in
The refrigeration cycle apparatus 200 illustrated in
In the heating operation, the first switching valve 31 and the second switching valve 32 are open, whereas the third switching valve 33 and the fourth switching valve 34 are closed. Thus, a flow of the refrigerant in the heating operation that is the same as in Embodiment 1 is formed. In the cooling operation, the first switching valve 31 and the second switching valve 32 are closed, whereas the third switching valve 33 and the fourth switching valve 34 are open.
In the cooling operation, the four-way valve 14 is switched to form paths illustrated by dotted lines in
As described above, the gas-liquid separator 10 is highly resistant to pressure. Therefore, the gas-liquid separator 10 can be provided in downstream of the refrigerant path in the cooling operation relative to an outdoor heat exchanger 12 that generates an in-pipe pressure of, for example, about 3 MPa or higher at maximum in the cooling operation. Hence, for example, a circuit for bypassing the outdoor heat exchanger and a receiver tank for storing liquid refrigerant that are required to perform a cooling-heating mixed operation by using a plurality of indoor units 202 can be provided with no additional pipes.
If the gas-liquid separator 10 is not highly resistant to pressure but includes a circuit for the cooling-heating mixed operation, the circuit needs to be configured as follows. A circuit for bypassing the outdoor heat exchanger that connects “a circuit between the four-way valve 14 and the outlet header 6” and “a circuit between the inlet header 5 and the third expansion device 23” to each other needs to be added. With such additional pipes, the allowance for space is reduced. Moreover, in terms of control operation, it is necessary to control the pressure inside the gas-liquid separator 10 to be reduced by controlling the third expansion device 23, with the second expansion device 22 being fully closed. Actually, since the gas-liquid separator 10 is highly resistant to pressure, the above consideration is not necessary.
Embodiment 4 relates to the shape of the container 1 of the gas-liquid separator 10. The refrigeration cycle apparatus 200 is configured as in Embodiment 1. Now, Embodiment 4 will be described, focusing on differences from Embodiment 1.
The container 1 of the gas-liquid separator 10 according to Embodiment 1 has a circular cylindrical shape. The gas-liquid separator 10 according to Embodiment 4 is characterized in that the container 1 has a conical cylindrical shape projecting toward the lower side in the direction of gravitational force.
To summarize, according to Embodiment 4, the advantageous effects obtained in Embodiment 1 can also be obtained. Furthermore, since the container 1 of the gas-liquid separator 10 has a conical shape projecting toward the lower side in the direction of gravitational force, the following advantageous effect is obtained. The container 1 has a shape conforming to the gas-liquid interface 102 to be formed inside the container 1. Therefore, while the effect of gas-liquid separation with the swirling flow that is obtained in Embodiment 1 employing the cylindrical container 1 is maintained, the volume of the container 1 can be reduced. Hence, the performance improvement and the size reduction of the gas-liquid separator 10 are both realized.
Embodiment 5 relates to the shape of the inflow pipe 2 of the gas-liquid separator 10. The refrigeration cycle apparatus 200 is configured as in Embodiment 1. Now, Embodiment 5 will be described, focusing on differences from Embodiment 1.
In the gas-liquid separator 10 according to Embodiment 5, as illustrated in
The insertion portion 2A is inserted through an upper part of the side wall of the container 1, with one end thereof being positioned inside the container 1 and the other end thereof being positioned outside the container 1. The insertion portion 2A is shifted from the center line O of the container 1 so that the center line O does not meet the extension of the insertion portion 2A.
A length L2 of the insertion portion 2A, in other words, a bent position L2 relative to the inlet 2a, is designed as follows:
0<L2<15Dinlet (5)
If L2≥15Dinlet, the entrance area provided for the liquid-phase part gathered on the outer peripheral side in the bent portion 2B before flowing into the container 1 becomes long. In such a case, the flow in the insertion portion 2A develops into a less-gathered flow. Consequently, the advantageous effect is reduced. Hence, L2 is set to smaller than 15Dinlet. Furthermore, to generate a gathered flow of liquid by using a bend, L2 is set to greater than 0.
The inflow portion 2C is provided as follows. In an installed state in which the container 1 of the gas-liquid separator 10 is vertically oriented, an orthogonal coordinate system is defined in a plane that is vertical to a center axis O1 of the insertion portion 2A, with the origin being the point of intersection of the plane and the center axis O1. In the coordinate system in which the x axis and they axis are defined as described below, the inflow portion 2C is positioned in a first quadrant that is defined on the positive side of the x axis and on the positive side of the y axis, or in which x>0 and y>0. The x axis is a vertical line extending downward in the direction of gravitational force from the origin 0 defined on the center axis O1 of the insertion portion 2A. The x axis is positive toward the lower side in the direction of gravitational force. The y axis extends on the left and right sides relative to a plane containing the center axis O1 and the x axis. The y axis is positive toward the side of the origin 0 on which the center line O of the container 1 is positioned.
Embodiment 5 is characterized in the inflow pipe 2 designed and positioned as above.
To summarize, according to Embodiment 5, the advantageous effects obtained in Embodiment 1 can also be obtained. Furthermore, since the inflow pipe 2 of the gas-liquid separator 10 includes the bent portion 2B in a middle part thereof, centrifugal force acts on the two-phase gas-liquid refrigerant flowing in the inflow pipe 2, Specifically, different centrifugal forces act on the gas-phase part and the liquid-phase part having different densities. The difference causes the liquid refrigerant to flow on the outer peripheral side in the bent portion 2B and the gas refrigerant to flow on the inner peripheral side in the bent portion 2B. That is, in the bent portion 2B, the liquid refrigerant gathers on the outer peripheral side of the bent portion 2B, and the gas refrigerant gathers on the inner peripheral side of the bent portion 2B. Furthermore, the liquid refrigerant flows into the container 1 while being kept gathered as in the bent portion 2B. Thus, before the refrigerant flows into the container 1, the refrigerant is separated in the inflow pipe 2 into liquid refrigerant and gas refrigerant. Therefore, the performance of gas-liquid separation is improved without changing the size of the container 1. Hence, the performance improvement and the size reduction of the gas-liquid separator 10 are both realized.
If the length of the insertion portion 2A satisfies Expression (5), the entrance distance for the refrigerant flowing from the downstream end of the bent portion 2B to the inlet 2a becomes short. Therefore, the effect of keeping the liquid refrigerant gathered as in the bent portion 2B when flowing into the container 1 can be produced more assuredly.
If the inflow portion 2C is on the positive side of the x axis or in the first quadrant, an upward flow of refrigerant is generated in the inflow portion 2C. With the inertia of that flow, the refrigerant discharged from the inflow portion 2C flows upward in the container 1. Therefore, compared with a case where the inflow portion 2C is on the positive side of the y axis, the time over which the centrifugal force acts can be made longer, and the performance of gas-liquid separation can be improved further. If the inflow portion 2C is provided at a position where x>0 and y<0, the liquid-phase part gathered on the outer peripheral side at the bend of the bent portion 2B adheres to the outer wall of the gas outflow pipe 4 in the container 1, Then, the liquid-phase part runs down the outer wall of the gas outflow pipe 4 and flows into the gas outlet 4a. Such a situation cannot satisfactorily produce the above effect.
In Embodiment 5, the bent portion 2B of the inflow pipe 2 has an L shape that is bent by 90 degrees. The angle of bend is not limited to the angle and may be changed arbitrarily.
Embodiment 6 relates to the liquid outflow pipe 3 of the gas-liquid separator 10. The refrigeration cycle apparatus 200 is configured as in Embodiment 1. Now, Embodiment 6 will be described, focusing on differences from Embodiment 1.
In the gas-liquid separator 10 according to Embodiment 6, as illustrated in
To summarize, according to Embodiment 6, the advantageous effects obtained in Embodiment 1 can also be obtained. Furthermore, since the liquid outlet 3a of the liquid outflow pipe 3 is at a position not overlapping the gas outlet 4a of the gas outflow pipe 4 in plan view, the following advantageous effect is obtained. Even if any gas refrigerant that has accidentally flowed into the liquid outflow pipe 3 but has come out of the liquid outflow pipe 3 with its buoyancy flows upward in the container 1 and pushes the liquid refrigerant that is in the upward path, the liquid refrigerant pushed by the gas refrigerant going upward can be prevented from flowing into the gas outlet 4a of the gas outflow pipe 4. Hence, the performance of gas-liquid separation is improved.
In Embodiment 6, the container 1 is provided with a single liquid outflow pipe 3. Alternatively, the container 1 may be provided with two or more liquid outflow pipes 3, That is, two or more liquid outlets 3a may be provided. The second and subsequent ones of the liquid outflow pipes 3 may be connected to the inlet header 5 at the lower ends thereof. Such a configuration also produces the above advantageous effects if the liquid outlets 3a are provided at positions not overlapping the gas outlet 4a of the gas outflow pipe 4 in plan view.
The gas-liquid separator 10 according to Embodiment 6 illustrated in
In this modification, the liquid outflow pipe 3 is inserted into the container 1 from the side wall of the container 1. In this configuration, the liquid outlet 3a is also at a position not overlapping the gas outlet 4a of the gas outflow pipe 4 in plan view. In
Embodiment 7 relates to the gas outflow pipe 4 of the gas-liquid separator 10. The refrigeration cycle apparatus 200 is configured as in Embodiment 1. Now, Embodiment 7 will be described, focusing on differences from Embodiment 1.
The gas-liquid separator 10 according to Embodiment 7 is characterized in additionally including an outer pipe 40 fitted over the gas outflow pipe 4. The outer pipe 40 is flared at a position lower than the inlet 2a of the inflow pipe 2. In other words, a flared surface 40a spreading outward toward the lower side is provided on the outer periphery of the gas outflow pipe 4 and at a position lower than the inlet 2a of the inflow pipe 2.
In such a configuration, liquid refrigerant that has flowed into the container 1 from the inlet 2a and liquid refrigerant that has struck upon the upper end of the container 1 run down the outer surface of the outer pipe 40 under the gravitational force and flows along the surface 4b. Since the surface 4b spreads outward toward the lower side, the liquid refrigerant flows in a direction toward the outer side from the center line O, that is, toward the wall surface in the container 1.
The effect of centrifugal force is greater on the side of the container 1 that is nearer to the wall than on the side nearer to the center line O. Therefore, the liquid refrigerant redirected along the surface 4b toward the wall of the container 1 receives a greater centrifugal force than in a configuration with no surface 4b. Hence, the centrifugal force applied to the liquid refrigerant on the surface 4b becomes greater than the surface tension of the liquid refrigerant on the surface 4b. Consequently, the liquid refrigerant is released from the surface 4b and flows toward the wall of the container 1, where a great centrifugal force acts on the liquid refrigerant flowing toward the wall of the container 1. Thus, the gas-liquid-separation efficiency is improved.
To summarize, according to Embodiment 7, the advantageous effects obtained in Embodiment 1 can also be obtained. Furthermore, since the gas outflow pipe 4 of the gas-liquid separator 10 has the flared surface 4b at a position lower than the inlet 2a, the following advantageous effect is obtained. The liquid refrigerant flowing downward along the outer surface of the outer pipe 40 under the gravitational force is redirected along the surface 4b toward the wall of the container 1, whereby a great centrifugal force can be applied to the liquid refrigerant. Consequently, the gas-liquid-separation efficiency can be improved.
Embodiment 8 relates to a method of controlling the opening degrees of the expansion devices 21 to 23 included in the refrigeration cycle apparatus 200. The gas-liquid separator 10 and the refrigeration cycle apparatus 200 are configured as in Embodiment 1. Now, Embodiment 8 will be described, focusing on differences from Embodiment 1.
The refrigeration cycle apparatus 200 according to Embodiment 8 includes a plurality of temperature sensors 50 to 52, in addition to the elements included in the refrigeration cycle apparatus 200 according to Embodiment 1 illustrated in
The controller 203 includes the temperature sensors 50 to 52. The temperature sensor 50 acquires the result of measurement for the discharge from the liquid outlet 3a of the gas-liquid separator 10 and controls relevant elements of the refrigeration cycle apparatus 200 in accordance with the measurement results and other relevant factors.
The controller 203 includes the temperature sensors 50 to 52. The temperature sensor 50 performs the heating operation and the cooling operation based on the result of measurement for the discharge from the liquid outlet 3a of the gas-liquid separator 10. Furthermore, to allow the individual indoor units 202 to satisfactorily exert the required air-conditioning capacity, the controller 203 determines a target condensing temperature in the heating operation or a target evaporating temperature in the cooling operation. In Embodiment 8, the target condensing temperature and the target evaporating temperature are each determined in accordance with a temperature difference ΔT between a preset temperature and the indoor-air temperature detected by a temperature sensor.
Then, the controller 203 controls the frequency of the compressor 13 such that the target evaporating temperature or the target condensing temperature is reached. Furthermore, the controller 203 controls the opening degree of the first expansion device 21 of the indoor unit 202 such that the degree of subcooling at the outlet of the indoor heat exchanger 11 in the heating operation or the degree of subcooling at the outlet of the outdoor heat exchanger 12 in the cooling operation becomes the target value.
In addition to the measurement results acquired through the temperature sensors 50 to 52, the controller 203 detects the number of indoor units 202 included and the frequency of the compressor 13 and controls the opening degrees of the expansion devices 21 to 23 in accordance with those pieces of data.
Now, changes in the gas-main region 100 and the liquid-main region 101 in the container 1 that occur in accordance with the operation of controlling the opening degrees of the first expansion device 21 and the third expansion device 23 will be described.
As illustrated in
In contrast, at point (B) in
On the other hand, at point (C) in
As illustrated in
Under such conditions, the opening degrees of the first expansion device 21, the second expansion device 22, and the third expansion device 23 are all “open” and are controlled appropriately. More specifically, the third expansion device 23 is first controlled such that the liquid outlet temperature TLS measured by the temperature sensor 50 is maintained to be within a predetermined temperature range. Furthermore, the first expansion device 21 is controlled such that the degree of subcooling at the outlet of the indoor heat exchanger 11 becomes a predetermined value.
As described above, the third expansion device 23 and the first expansion device 21 are controlled individually in accordance with the liquid outlet temperature TLS and the degree of subcooling, respectively. Consequently, the third expansion device 23 and the first expansion device 21 are controlled such that when the opening degree of one of the two is raised, the opening degree of the other is lowered, as described above. Specifically, for example, when the liquid outlet temperature TLS becomes lower, the opening degree of the third expansion device 23 is lowered, whereas the opening degree of the first expansion device 21 is raised. The pressure inside the container 1 is determined by the ratio between the opening degrees of the first expansion device 21 and the third expansion device 23, and the opening degree of the second expansion device 22.
Then, the second expansion device 22 is controlled, considering the balance relative to the third expansion device 23. For example, if the opening degree of the third expansion device 23 is raised, the opening degree of the second expansion device 22 is also raised. In such a control operation, the gas-liquid interface 102 in the gas-liquid separator 10 is adjusted, whereby the effect of improving the gas-liquid-separation efficiency is obtained.
Under the intermediate conditions, the compressor 13 operates at a predetermined rotational frequency or lower, and the refrigerant circulation amount Grnow [kg/h] is within a range of 0<Grnow≤1.98(Dinlet)2. Under such “intermediate” conditions and in the cooling only operation, as summarized in
The range of Grnow for the intermediate conditions is defined as 0<Grnow≤1.98(Dinlet)2 on the basis of the following:
lower limit of Grnow: over 0 kg/h during operation
upper limit of Grnow: An experiment has shown that, to obtain the effect of centrifugation, a mass velocity of 4Gr/3600/π/(Dinlet/1000)2 needs to be over 700 [kg/m2·s]. Therefore, in the intermediate operation in which Grnow 1.98(Dinlet)2 and the mass velocity is 700 [kg/m2·s] or lower, the second expansion device 22 is fully closed, so that the gas-liquid separator 10 is not used as a gas-liquid separator.
Alternatively, the opening degree of the third expansion device 23 may be set to fully open, whereby the refrigerant may be supplied in the form of liquid refrigerant in a path from the refrigerant outlet of the outdoor unit 201 to the refrigerant inlet of the indoor unit 202. In such a control operation, if the refrigeration cycle apparatus 200 includes a plurality of indoor units 202, the refrigerant can be distributed in the form of a single liquid phase to the plurality of indoor units 202. Hence, the distribution of flow rate can be controlled easily.
In the actual control operation, tables summarizing optimum combinations of opening degrees of the first expansion device 21, the second expansion device 22, and the third expansion device 23 are prepared and stored in advance. The combinations are determined in accordance with the number of indoor units 202 included, the rotational frequency of the compressor 13, the pressure P in the gas-liquid separator 10, and the degree of subcooling of the indoor heat exchanger 11. The control operation is performed in accordance with the tables. That is, tables for the heating only operation under the rated conditions, the heating only operation under the intermediate conditions, and the cooling only operation may be stored.
To detect the pressure P in the gas-liquid separator 10, the temperature of the two-phase gas-liquid refrigerant discharged from the liquid outlet 3a of the gas-liquid separator 10 is measured by the temperature sensor 50, and the pressure P is calculated from the relationship between the temperature of the two-phase gas-liquid refrigerant and the pressure. The degree of subcooling of the indoor heat exchanger 11 is detected by subtracting the condenser outlet temperature TRout, which is measured by the temperature sensor 51, from the condensation saturation temperature Tc of the refrigerant, which is measured by the temperature sensor 52.
The operations of opening and closing the expansion devices 21 to 23 summarized in
To summarize, according to Embodiment 8, the advantageous effects obtained in Embodiment 1 can also be obtained. Furthermore, controlling the expansion devices 21 to 23 produces the following advantageous effect. The refrigerant pressure in the container 1 is adjusted by controlling the expansion devices 21 to 23, whereby the shape of the gas-liquid interface 102 is controlled appropriately. Hence, accidental flow of the liquid from the liquid-main region 101 into the gas outflow pipe 4 can be prevented.
In Embodiment 9, the third expansion device 23 included in the refrigeration cycle apparatus 200 is replaced with an expansion device whose amount of expansion is fixed. The other details of the refrigeration cycle apparatus 200 are the same as in Embodiment 1. The basic concept of controlling the opening degrees of the expansion devices is the same as in Embodiment 8. Now, Embodiment 9 will be described, focusing on differences from Embodiments 1 and 8.
In Embodiment 1 illustrated in
In Embodiment 8, the third expansion device 23 provided at the liquid outlet of the gas-liquid separator 10 is controlled such that the liquid outlet temperature TLS measured by the temperature sensor 50 is maintained to be within a predetermined temperature range. In Embodiment 9, however, the third expansion device 24 provided at the liquid outlet of the gas-liquid separator 10 is a fixed expansion device, and the adjustment of the liquid outlet temperature TLS by controlling the opening degree of the third expansion device 24 is impossible. Therefore, the degree of subcooling at the outlet of the indoor heat exchanger 11 is controlled by using the first expansion device 21 and the second expansion device 22. Specifically, in accordance with the temperatures measured by the temperature sensor 51 and the temperature sensor 52, respectively, the first expansion device 21 and the second expansion device 22 are controlled such that the degree of subcooling becomes the target value. For example, a case where the quality of the refrigerant flowing into the gas-liquid separator 10 in the heating operation is 0.05 to 0.30 and the frequency of the compressor 13 is a particular value or higher or the number of indoor units 202 is over a particular value applies to an operation under the rated conditions.
Methods of controlling the first expansion device 21, the second expansion device 22, and the third expansion device 24 in the “heating only operation under intermediate conditions” and in the “cooling only operation” are the same as in Embodiment 8 summarized in
To summarize, according to Embodiment 9, the advantageous effects obtained in Embodiment 1 can also be obtained. Furthermore, since the amount of expansion by the third expansion device 24 is fixed, the third expansion device 24 does not need to be controlled. Therefore, the restriction on the configuration of the pipe provided between the liquid outlet 3a of the gas-liquid separator 10 to the inlet header 5 of the indoor heat exchanger 11 is eased. The reason for this is as follows. If the third expansion device 24 is a valve, such as an expansion valve, whose opening degree is controllable as in Embodiment 1, a restriction on the pipe configuration arises in that, for example, the direction in which the refrigerant flows into the expansion valve is limited to a vertically upward direction for assured opening-degree controllability. However, since the third expansion device 24 as a fixed expansion device is employed, such a restriction is unnecessary. That is, the restriction on the pipe configuration is eased, making it easier to install the refrigerant circuit into the housing of the outdoor unit 201.
Alternatively, the third expansion device 24 may be replaced with a capillary tube, a refrigerant pipe, or the inlet header 5 of the outdoor heat exchanger 12, and the function of the restrictor may be provided in the form of, for example, frictional pressure loss in the refrigerant pipe or impact pressure loss. With the third expansion device 24 having such a configuration, the pipe configuration between the liquid outlet 3a of the gas-liquid separator 10 and the inlet header 5 of the outdoor heat exchanger 12 can be simplified, realizing a cost reduction. Furthermore, the refrigerant pipes can be easily installed in the outdoor unit 201.
While Embodiments 1 to 9 have been described as different embodiments, the refrigeration cycle apparatus 200 may be obtained by combining individual features of Embodiments 1 to 9 in any way. Moreover, each of the modifications applied to features that are common to Embodiments 1 to 9 may also be applied to any of Embodiments 1 to 9 that is not described for that modification.
1 container 2 inflow pipe 2A insertion portion 2B bent portion 2C inflow portion 2a inlet 3 liquid outflow pipe 3a liquid outlet 4 gas outflow pipe 4a gas outlet 4b surface 5 inlet header 6 outlet header 7 bypass 10 gas-liquid separator 11 indoor heat exchanger 12 outdoor heat exchanger compressor 14 four-way valve 15 refrigerant tank 21 first expansion device 22 second expansion device 23 third expansion device 24 third expansion device 30a pipe 30b pipe 31 first switching valve 32 second switching valve 33 third switching valve 34 fourth switching valve 40 outer pipe 40a surface 50 temperature sensor 51 temperature sensor 52 temperature sensor 100 gas-main region 101 liquid-main region 102 gas-liquid interface 200 refrigeration cycle apparatus 201 outdoor unit 202 indoor unit 203 controller
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/012013 | 3/24/2017 | WO | 00 |
