JP7534124B2 - Refrigeration Cycle Equipment - Google Patents

Description

This disclosure relates to a refrigeration cycle device.

Figure 8 is a configuration diagram of the refrigeration cycle device of Patent Document 1. The refrigeration cycle device 100 shown in Figure 8 includes an evaporator 101, a multi-stage compressor 102, a condenser 103, a first expansion valve 104a, a second expansion valve 104b, and an economizer heat exchanger 105. The multi-stage compressor 102 has a first compression stage 102a and a second compression stage 102b. Specifically, the multi-stage compressor 102 is a turbo compressor, and the compression stages 102a and 102b are impellers.

The refrigerant is vaporized in the evaporator 101, pumped by the multi-stage compressor 102, and then condensed in the condenser 103. The refrigerant condensed in the condenser 103 flows through either the first flow path 106a or the second flow path 106b.

The refrigerant flowing through the first flow path 106a flows through the economizer heat exchanger 105, expands in the second expansion valve 104b, and is then guided to the evaporator 101. The refrigerant flowing through the second flow path 106b expands in the first expansion valve 104a, flows through the economizer heat exchanger 105, and is then guided to the multi-stage compressor 102.

Specifically, the refrigerant flowing through the second flow path 106b is vaporized by heat exchange with the liquid-phase refrigerant flowing through the first flow path 106a in the economizer heat exchanger 105. The gas-phase refrigerant generated by the vaporization is sucked into the compression process of the multi-stage compressor 102 together with fine droplets. Specifically, this gas-phase refrigerant is sucked into the second compression stage 102b together with the droplets.

JP 2020-003124 A

This disclosure provides technology suitable for suppressing the inhalation of liquid droplets during the compression process of a multi-stage compressor.

The present disclosure relates to
A refrigeration cycle device that uses a refrigerant containing, as a main component, a component having a saturated vapor pressure equal to or lower than atmospheric pressure at room temperature,
An evaporator;
A multi-stage compressor;
A condenser;
Tanks and
In this order,
The multi-stage compressor has a first compression stage and a second compression stage,
the tank has a partition, an upper space located above the partition, a lower space located below the partition, a communication port that communicates the upper space with the lower space, an inlet that opens into the upper space, a liquid phase outlet that opens into the lower space, and a gas phase outlet that opens into the lower space and is located at a higher position than the liquid phase outlet,
the refrigerant circulates through the evaporator, the first compression stage, the second compression stage, the condenser, the inlet, the upper space, the communication port, the lower space, and the liquid phase outlet in this order;
The refrigerant in a gas phase flows from the gas phase outlet to the second compression stage.
A refrigeration cycle device is provided.

The technology disclosed herein is suitable for preventing droplets from being sucked into the compressor during the compression process of a multi-stage compressor.

FIG. 1 is a configuration diagram of a refrigeration cycle device according to an embodiment of the present invention. FIG. 1 is an enlarged side view of a first tank according to an embodiment of the present invention; FIG. 1 is an enlarged view of a first tank according to an embodiment of the present invention; FIG. 1 is an enlarged view of an intermediate flow path according to an embodiment of the present invention; Enlarged view of the intermediate flow passage of the modified example FIG. 1 is an enlarged side view of a second tank according to an embodiment of the present invention; FIG. 1 is an enlarged view of a second tank according to an embodiment of the present invention, viewed from above. Diagram of a conventional refrigeration cycle device

(Findings that form the basis of this disclosure)
Suppose water is used as the refrigerant in the refrigeration cycle device 100 shown in FIG. 8. In this case, the refrigeration cycle device 100 can operate under the condition that the condensation pressure at 38° C. is 6.63 kPa and the saturated vapor pressure at 6.2° C. is 0.95 kPa. In other words, the refrigeration cycle device 100 can operate under the condition that the condensation pressure and the saturated vapor pressure are negative pressures and the differential pressure between them is a minute value of 5.68 kPa. Under such conditions, when liquid water boils near the saturated liquid line, water vapor having a volume about 14,500 times that of water can be generated (Yoshiaki Katto, "Heat Transfer", Vol. 44, No. 187, Japan Society of Heat Transfer, pp. 15-20, see (2) Low Pressure Boiling in "The Science of Boiling (2)").

After passing through the first expansion valve 104a, the water flows into the economizer heat exchanger 105 in a two-phase gas-liquid state. The two-phase water receives heat in the economizer heat exchanger 105. As a result, the liquid water contained in the two-phase water boils and evaporates.

As described above, macroscopically, it can be explained that in the economizer heat exchanger 105, the liquid water contained in the two-phase water evaporates. Microscopically, this liquid water evaporates while generating a huge volume of steam at the boundary surface where it comes into contact with the steam. During this process, the water forms a film that envelops the steam, forming bubbles. When these bubbles receive heat, the volume of the steam in the bubbles increases. As the volume increases, the bubbles eventually burst. When the bubbles burst, a large amount of tiny water droplets are generated.

In this way, a large amount of tiny water droplets are generated in the economizer heat exchanger 105. Meanwhile, during the evaporation process, the volume of the water increases rapidly. Due to the combination of these phenomena, the water droplets are sucked from the economizer heat exchanger 105 into the compression stage 102b of the multi-stage compressor 102 without all of them changing phase to steam. The sucking of the water droplets into the compression stage 102b can cause erosion in the compression stage 102b. The erosion can degrade the performance of the multi-stage compressor 102.

Therefore, the inventors investigated a technology suitable for preventing droplets from being sucked into the compression process of a multi-stage compressor.

(Summary of one aspect of the present disclosure)
A refrigeration cycle device according to a first aspect of the present disclosure includes:
A refrigeration cycle device that uses a refrigerant containing, as a main component, a component having a saturated vapor pressure equal to or lower than atmospheric pressure at room temperature,
An evaporator;
A multi-stage compressor;
A condenser;
Tanks and
In this order,
The multi-stage compressor has a first compression stage and a second compression stage,
the tank has a partition, an upper space located above the partition, a lower space located below the partition, a communication port that communicates the upper space with the lower space, an inlet that opens into the upper space, a liquid phase outlet that opens into the lower space, and a gas phase outlet that opens into the lower space and is located at a higher position than the liquid phase outlet,
the refrigerant circulates through the evaporator, the first compression stage, the second compression stage, the condenser, the inlet, the upper space, the communication port, the lower space, and the liquid phase outlet in this order;
The refrigerant in a vapor phase flows from the vapor phase outlet to the second compression stage.

The technology according to the first aspect is suitable for preventing droplets from being sucked into the compression process of a multi-stage compressor. Specifically, the technology according to the first aspect is suitable for preventing droplets from being sucked into the second compression stage.

In a second aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to the first aspect,
The refrigerant in a gas-liquid two-phase state may flow into the upper space from the inlet,
In the upper space, the refrigerant in a gas-liquid two-phase state may be decompressed to generate liquid droplets, and the liquid droplets may be received by an upper surface of the partition, thereby separating the refrigerant in the gas-liquid two-phase state into gas and liquid.
The refrigerant in a liquid phase may flow along the upper surface of the partition, drip from the communication port, and be stored in the lower space, and then flow out from the liquid phase outlet,
The refrigerant in a gas phase may move from the upper space through the communication port and the lower space in this order to the gas phase outlet.

The behavior of the refrigerant in the second aspect is a specific example of the behavior of the refrigerant in a tank.

In a third aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to the first or second aspect,
When the tank is observed from above, the gas phase outlet and the communication port may be located on opposite sides of a second line that is perpendicular to a first line connecting the gas phase outlet and the inlet and passes through the inlet.

The third aspect is suitable for suppressing the intake of liquid droplets into the compression process of a multi-stage compressor. Specifically, the technology related to the third aspect is suitable for suppressing the intake of liquid droplets into the second compression stage.

In a fourth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to any one of the first to third aspects,
The partition may include, at a position adjacent to the communication port, a sloping portion whose height decreases toward the communication port.

According to the fourth aspect, the liquid phase refrigerant can easily flow smoothly along the top surface of the partition to the communication port.

In a fifth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to any one of the first to fourth aspects,
When the tank is referred to as a first tank, the partition is referred to as a first partition, the upper space is referred to as a first upper space, the lower space is referred to as a first lower space, the communication port is referred to as a first communication port, the inlet is referred to as a first inlet, the liquid phase outlet is referred to as a first liquid phase outlet, and the gas phase outlet is referred to as a first gas phase outlet,
The refrigeration cycle apparatus may further include a second tank,
The multi-stage compressor may further include a third compression stage,
The second tank may have a second partition, a second upper space located above the second partition, a second lower space located below the second partition, a second communication port that communicates the second upper space with the second lower space, a second inlet that opens into the second upper space, a second liquid phase outlet that opens into the second lower space, and a second gas phase outlet that opens into the second lower space and is located at a higher position than the second liquid phase outlet,
the refrigerant may be circulated through the evaporator, the third compression stage, the first compression stage, the second compression stage, the condenser, the first inlet, the first upper space, the first communication port, the first lower space, the first liquid phase outlet, the second inlet, the second upper space, the second communication port, the second lower space, and the second liquid phase outlet in this order,
The refrigerant may flow in a vapor phase from the second vapor phase outlet to the first compression stage.

The fifth aspect is suitable for suppressing the intake of liquid droplets during the compression process of a multi-stage compressor. Specifically, the technology related to the fifth aspect is suitable for suppressing the intake of liquid droplets into the first compression stage.

In a sixth aspect of the present disclosure, for example, the refrigeration cycle apparatus according to any one of the first to fifth aspects may further include an intermediate flow path connecting the first liquid phase outlet and the second inlet,
The intermediate flow path may have a low portion and a high portion located higher than the low portion,
The refrigerant may flow through the first liquid phase outlet, the lower portion, the higher portion, and the second inlet in this order.

According to the sixth aspect, it is difficult to form a loop in which the gas phase refrigerant discharged from the first compression stage passes through the first gas phase outlet of the first tank, the first lower space, the first liquid phase outlet, the intermediate flow path, the second inlet of the second tank, the second upper space, the second communication port, the second lower space, and the second gas phase outlet in this order, and then returns to the first compression stage. This makes it easier to ensure the performance of the multi-stage compressor.

In a seventh aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to any one of the first to sixth aspects,
The refrigeration cycle apparatus may further include a bypass flow path extending at a position lower than the high-level portion, and a bypass valve provided in the bypass flow path,
When the opening degree of the bypass valve is greater than zero, the refrigerant may bypass the high-level portion and flow through the first liquid phase outlet, the bypass flow path, and the second inlet in this order.

According to the seventh aspect, the refrigeration cycle device can be operated appropriately by adjusting the opening of the bypass valve, both under low load conditions where the pressure difference between the compression stages of the multi-stage compressor is small, and under high load conditions where the pressure difference is large.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these embodiments.

In the following embodiments, the term "multi-stage compressor" may be used. In the following embodiments, "multi-stage" in "multi-stage compressor" means two or more stages.

In the following embodiments, the term "room temperature" may be used. In the following embodiments, "room temperature" refers to 20°C ± 15°C, as specified in Japanese Industrial Standard JIS Z8703.

In the following embodiments, the term "main component" may be used. In the following embodiments, "main component" refers to the component that is contained in the largest amount by mass.

In the following embodiments, "above" and "below" respectively mean above and below in the vertical direction. "High position" and "low position" mean high and low positions in the vertical direction.

In the following embodiments, ordinal numbers such as first, second, third, etc. may be used. When an element is assigned an ordinal number, it is not necessary that there is an element of the same type with a lower number. The number of the ordinal number can be changed as necessary.

(Embodiment 1)
Hereinafter, the first embodiment will be described with reference to FIG.

[1-1. Configuration]
1 is a configuration diagram of a refrigeration cycle apparatus 200 according to the present embodiment. In the refrigeration cycle apparatus 200, a refrigerant containing, as a main component, a component having a saturated vapor pressure equal to or lower than atmospheric pressure at room temperature flows. Examples of such refrigerant include a refrigerant containing water as a main component, a refrigerant containing R1233zd as a main component, and the like. When the refrigeration cycle apparatus 200 is in operation, the pressure inside the refrigeration cycle apparatus 200 is, for example, lower than atmospheric pressure.

The refrigeration cycle device 200 includes an evaporator 201, a multi-stage compressor 202, a condenser 204, a first valve 205, a first tank 207, a second tank 210, and a second valve 213. The evaporator 201, the multi-stage compressor 202, the condenser 204, the first valve 205, the first tank 207, the second tank 210, and the second valve 213 are connected in this order. The refrigerant flows through the evaporator 201, the multi-stage compressor 202, the condenser 204, the first valve 205, the first tank 207, the second tank 210, and the second valve 213 in this order.

The refrigeration cycle device 200 includes a first flow path 221, a second flow path 222, a third flow path 223, a fourth flow path 224, an intermediate flow path 209, a bypass flow path 214, a fifth flow path 225, a first gas phase flow path 208, and a second gas phase flow path 211. The first flow path 221 connects the evaporator 201 and the multi-stage compressor 202. The second flow path 222 connects the multi-stage compressor 202 and the condenser 204. The third flow path 223 connects the condenser 204 and the first valve 205. The fourth flow path 224 connects the first valve 205 and the first tank 207. The intermediate flow path 209 connects the first tank 207 and the second tank 210. The bypass flow path 214 connects two points of the intermediate flow path 209 so as to bypass a part of the intermediate flow path 209. The fifth flow path 225 connects the second tank 210 and the second valve 213. The first gas phase flow path 208 connects the first tank 207 and the multi-stage compressor 202 so as to bypass the second tank 210 and the evaporator 201. The second gas phase flow path 211 connects the second tank 210 and the multi-stage compressor 202 so as to bypass the evaporator 201.

The refrigeration cycle device 200 is equipped with a bypass valve 217. The bypass valve 217 is provided in the bypass flow path 214.

The components of the refrigeration cycle device 200 are further described below.

In the evaporator 201, heat exchange occurs between an external heating medium and a liquid-phase refrigerant. This heat exchange causes the liquid-phase refrigerant to evaporate and generate a gas-phase refrigerant. The evaporator 201 may be a plate-type heat exchanger, a shell-and-tube-type heat exchanger, a spray-type heat exchanger, or a direct-contact-type heat exchanger.

The first flow path 221 guides the gas phase refrigerant from the evaporator 201 to the multi-stage compressor 202. Specifically, the first flow path 221 guides the gas phase refrigerant from the evaporator 201 to the third compression stage 202c of the multi-stage compressor 202.

The multi-stage compressor 202 pumps gas-phase refrigerant. The multi-stage compressor 202 has multiple compression stages. These compression stages are connected to each other.

In this embodiment, the multi-stage compressor 202 is a turbo compressor. The compression stages are impellers.

In the example shown in FIG. 1, the multi-stage compressor 202 has a first compression stage 202a, a second compression stage 202b, a third compression stage 202c, a first communication passage 203a, and a second communication passage 203b. The third compression stage 202c, the second communication passage 203b, the first compression stage 202a, the first communication passage 203a, and the second compression stage 202b are connected in this order. The compression stages 202a, 202b, and 202c are impellers.

The gas phase refrigerant is compressed in the third compression stage 202c, flows through the second communication passage 203b, is compressed in the first compression stage 202a, flows through the first communication passage 203a, and is then compressed in the second compression stage 202b. The communication passages 203a and 203b can be referred to as the compression flow path.

In the example shown in FIG. 1, the multi-stage compressor 202 is a three-stage compressor. However, the number of compression stages that the multi-stage compressor 202 has is not particularly limited.

The second flow path 222 guides the gas phase refrigerant from the multi-stage compressor 202 to the condenser 204. Specifically, the second flow path 222 guides the gas phase refrigerant from the second compression stage 202b of the multi-stage compressor 202 to the condenser 204.

In the condenser 204, heat exchange occurs between the cooling medium from the outside and the gas phase refrigerant. This heat exchange causes the gas phase refrigerant to condense, generating a liquid phase refrigerant. The condenser 204 may be a plate type heat exchanger, a shell-and-tube type heat exchanger, a spray type heat exchanger, or a direct contact type heat exchanger.

The third flow path 223 guides the refrigerant from the condenser 204 to the first valve 205. In the third flow path 223, a portion of the liquid-phase refrigerant is vaporized due to reduced pressure. Therefore, the gas-liquid two-phase refrigerant is guided to the first valve 205 by the third flow path 223.

The first valve 205 adjusts the flow rate of the two-phase gas-liquid refrigerant flowing through the first valve 205. The first valve 205 can be referred to as a high-stage flow rate adjustment valve.

The fourth flow path 224 guides the gas-liquid two-phase refrigerant from the first valve 205 to the first tank 207. The fourth flow path 224 can be referred to as the high-stage side flow path.

In the first tank 207, the two-phase gas-liquid refrigerant is separated into gas and liquid while being evaporatively cooled. The first tank 207 can be referred to as a high-stage evaporative cooling tank.

Figure 2 is an enlarged side view of the first tank 207 of this embodiment. As shown in Figure 2, in this embodiment, the first tank 207 has a first partition 207a. The first partition 207a divides the first internal space 207s of the first tank 207 into a first upper space 207u and a first lower space 207d. The first partition 207a is provided with a first communication port 207c. The first upper space 207u and the first lower space 207d are in communication with each other via the first communication port 207c.

The first tank 207 is provided with a first inlet 207i, a first gas phase outlet 207og, and a first liquid phase outlet 207ol. The first inlet 207i is connected to the fourth flow path 224 and faces the first upper space 207u. The first gas phase outlet 207og faces the first lower space 207d and is connected to the first gas phase flow path 208. The first liquid phase outlet 207ol faces the first lower space 207d and is connected to the intermediate flow path 209. The first gas phase outlet 207og is provided at a higher position than the first liquid phase outlet 207ol. The first partition 207a can be referred to as a high stage side shield.

As shown in FIG. 2, in this embodiment, the first partition 207a has a first inclined portion 207ai. The first inclined portion 207ai is provided at a position adjacent to the first communication opening 207c. The height of the first inclined portion 207ai decreases as it approaches the first communication opening 207c.

As shown in FIG. 2, in this embodiment, the first tank 207 has a first bottom wall 207bw, a first ceiling wall 207cw, and a first side wall 207sw. The first side wall 207sw connects the first bottom wall 207bw and the first ceiling wall 207cw. A first inlet 207i is provided in the first ceiling wall 207cw. A first gas phase outlet 207og and a first liquid phase outlet 207ol are provided in the first side wall 207sw. In addition, the first side wall 207sw is exposed to the first communication port 207c.

Figure 3 is an enlarged view of the first tank 207 of this embodiment as viewed from above. When the first tank 207 is observed from above, a straight line connecting the first gas phase outlet 207og and the first inlet 207i is defined as a first straight line 207x, and a straight line perpendicular to the first straight line 207x and passing through the first inlet 207i is defined as a second straight line 207y. In this embodiment, when the first tank 207 is observed from above, the first gas phase outlet 207og and the first communication port 207c are on opposite sides of the second straight line 207y. Specifically, when the first tank 207 is observed from above, the first gas phase outlet 207og, the first inlet 207i, and the first communication port 207c appear in this order on the first straight line 207x. Note that the first partition 207a and the like are not shown in Figure 3.

In the first tank 207, gas-liquid two-phase refrigerant flows in from the first inlet 207i. The gas-phase refrigerant obtained by gas-liquid separation in the first tank 207 flows out from the first gas-phase outlet 207og. The liquid-phase refrigerant obtained by gas-liquid separation in the first tank 207 flows out from the first liquid-phase outlet 207ol.

The first gas phase flow path 208 bypasses the second tank 210 and the evaporator 201 and guides the gas phase refrigerant from the first tank 207 to the multi-stage compressor 202. Specifically, the first gas phase flow path 208 guides the gas phase refrigerant from the first tank 207 to the first communication passage 203a. The first gas phase flow path 208 can be referred to as a high-stage gas phase flow path. The gas phase refrigerant guided to the first communication passage 203a is sucked into the second compression stage 202b.

The intermediate flow path 209 guides the refrigerant from the first tank 207 to the second tank 210. In the intermediate flow path 209, a portion of the liquid-phase refrigerant is vaporized by reducing the pressure. Therefore, the gas-liquid two-phase refrigerant is guided to the second tank 210 by the intermediate flow path 209.

Figure 4 is an enlarged view of the intermediate flow path 209 in this embodiment. As shown in Figure 4, in this embodiment, the intermediate flow path 209 has a low-level section 209L and a high-level section 209H. The first liquid phase outlet 207ol, the low-level section 209L, the high-level section 209H, and the second inlet 210i of the second tank 210 are connected in this order. The high-level section 209H is located at a higher position than the first liquid phase outlet 207ol, the low-level section 209L, and the second inlet 210i.

As shown in FIG. 4, in this embodiment, the intermediate flow path 209 has a U-shaped portion that protrudes upward, and the high portion 209H is the apex of the U-shaped portion. However, the configuration of the intermediate flow path 209 is not limited to this. FIG. 5 is an enlarged view of the intermediate flow path 209 in a modified example. In the example of FIG. 5, the intermediate flow path 209 has a rectangular portion that protrudes upward, and the high portion 209H is the upper side of the rectangular portion.

The bypass flow path 214 connects two points of the intermediate flow path 209 so as to bypass a portion of the intermediate flow path 209. Specifically, the bypass flow path 214 connects two points of the intermediate flow path 209 so as to bypass the high-level portion 209H. The bypass flow path 214 extends at a position lower than the high-level portion 209H. As with the intermediate flow path 209, in the bypass flow path 214, a portion of the liquid-phase refrigerant can be vaporized by reducing pressure.

In the second tank 210, the two-phase gas-liquid refrigerant is separated into gas and liquid while being evaporatively cooled. The second tank 210 can be referred to as a low-stage evaporative cooling tank.

Figure 6 is an enlarged side view of the second tank 210 of this embodiment. As shown in Figure 6, in this embodiment, the second tank 210 has a second partition 210a. The second partition 210a divides the second internal space 210s of the second tank 210 into a second upper space 210u and a second lower space 210d. The second partition 210a is provided with a second communication port 210c. The second upper space 210u and the second lower space 210d are in communication with each other via the second communication port 210c.

The second tank 210 is provided with a second inlet 210i, a second gas phase outlet 210og, and a second liquid phase outlet 210ol. The second inlet 210i is connected to the intermediate flow path 209 and faces the second upper space 210u. The second gas phase outlet 210og faces the second lower space 210d and is connected to the second gas phase flow path 211. The second liquid phase outlet 210ol faces the second lower space 210d and is connected to the fifth flow path 225. The second gas phase outlet 210og is provided at a higher position than the second liquid phase outlet 210ol. The second partition 210a can be referred to as a low stage side shield.

As shown in FIG. 6, in this embodiment, the second partition 210a has a second inclined portion 210ai. The second inclined portion 210ai is provided at a position adjacent to the second communication port 210c. The height of the second inclined portion 210ai decreases as it approaches the second communication port 210c.

As shown in FIG. 6, in this embodiment, the second tank 210 has a second bottom wall 210bw, a second ceiling wall 210cw, and a second side wall 210sw. The second side wall 210sw connects the second bottom wall 210bw and the second ceiling wall 210cw. A second inlet 210i is provided in the second ceiling wall 210cw. A second gas phase outlet 210og is provided in the second side wall 210sw. A second liquid phase outlet 210ol is provided in the second bottom wall 210bw. In addition, the second side wall 210sw is exposed to the second communication port 210c.

If the second liquid phase outlet 210ol is provided on the second bottom wall 210bw instead of the second side wall 210sw, it is easier to supply liquid phase refrigerant to the fifth flow path 225 even when the amount of liquid phase refrigerant stored in the second tank 210 is small. However, the second liquid phase outlet 210ol may be provided on the second side wall 210sw.

2 and 6, the first distance, which is the distance between the first bottom wall 207bw and the first gas phase outlet 207og, is greater than the second distance, which is the distance between the second bottom wall 210bw and the second gas phase outlet 210og.

The advantages of the first distance > the second distance are explained below. From the viewpoint of reducing the pressure loss in the first gas phase flow path 208, it is better for the first gas phase flow path 208 to be short. However, if this is done, the vapor pressure in the first tank 207 is likely to be low. If the vapor pressure in the first tank 207 is low, the pressure difference between the first tank 207 and the second tank 210 is likely to be small. When such a configuration is adopted, if the pressure difference between the suction port and the discharge port of the first compression stage 202a becomes transiently small, the pressure difference between the tanks 207 and 210, which is already likely to be small, may be further reduced. This may cause a backflow of the liquid phase refrigerant from the intermediate flow path 209 to the first tank 207. However, if the first distance > the second distance, it is easy to ensure the first distance. Therefore, even if the liquid level in the first tank 207 rises due to the backflow, it is easy to ensure a sufficient distance between the liquid level and the first gas phase outlet 207og.

However, the first distance and the second distance may be the same. Also, the first distance may be smaller than the second distance.

Figure 7 is an enlarged view of the second tank 210 of this embodiment as viewed from above. When the second tank 210 is observed from above, the straight line connecting the second gas phase outlet 210og and the second inlet 210i is defined as the third straight line 210x, and the straight line perpendicular to the third straight line 210x and passing through the second inlet 210i is defined as the fourth straight line 210y. In this embodiment, when the second tank 210 is observed from above, the second gas phase outlet 210og and the second communication port 210c are on opposite sides of the fourth straight line 210y. Specifically, when the second tank 210 is observed from above, the second gas phase outlet 210og, the second inlet 210i, and the second communication port 210c appear in this order on the third straight line 210x. Note that the second partition 210a and the like are not shown in Figure 7.

In the second tank 210, gas-liquid two-phase refrigerant flows in from the second inlet 210i. The gas-phase refrigerant obtained by gas-liquid separation in the second tank 210 flows out from the second gas-phase outlet 210og. The liquid-phase refrigerant obtained by gas-liquid separation in the second tank 210 flows out from the second liquid-phase outlet 210ol.

The second gas phase flow path 211 bypasses the evaporator 201 and guides the gas phase refrigerant from the second tank 210 to the multi-stage compressor 202. Specifically, the second gas phase flow path 211 guides the gas phase refrigerant from the second tank 210 to the second communication passage 203b. The second gas phase flow path 211 can be referred to as a low-stage gas phase flow path. The gas phase refrigerant guided to the second communication passage 203b is sucked into the first compression stage 202a.

The fifth flow path 225 guides liquid phase refrigerant from the second tank 210 to the second valve 213. The fifth flow path 225 can be referred to as a low-stage liquid phase flow path.

The second valve 213 adjusts the flow rate of the liquid phase refrigerant flowing through the first valve 205. The second valve 213 can be referred to as a low-stage flow rate adjustment valve.

The first valve 205 is, for example, a single-hole or multi-hole variable orifice valve. The same applies to the second valve 213 and the bypass valve 217.

[1-2. Operation]
The operation and function of the refrigeration cycle apparatus 200 configured as above will be described below with reference to the drawings.

[1-2-1. Operation in the first state]
The refrigeration cycle apparatus 200 can be in a first state. In the first state, the opening degree of the bypass valve 217 is relatively small. Here, the concept of the opening degree being relatively small includes the opening degree being zero. In the first state of the present embodiment, the opening degree of the bypass valve 217 is zero. In the present embodiment, the refrigeration cycle apparatus 200 can be in the first state at a high load. Specifically, the refrigeration cycle apparatus 200 can be in the first state at a rated load. In the present embodiment, at a high load, the temperature difference between the refrigerant after evaporation in the evaporator 201 and the refrigerant after condensation in the condenser 204 is large, the rotation speed of the multi-stage compressor 202 is high, and the pressure difference between the compression stages in the multi-stage compressor 202 is large. Typically, at a rated load, the above temperature difference, rotation speed, and pressure difference are in the rated range.

The operation of the refrigeration cycle device 200 in the first state is described below.

In the evaporator 201, heat is exchanged between the stored liquid-phase refrigerant and the heating medium from the outside. This heat exchange causes the liquid-phase refrigerant to evaporate, generating gas-phase refrigerant.

Next, the gas phase refrigerant is compressed sequentially by each compression stage in the multi-stage compressor 202. Specifically, the gas phase refrigerant is compressed in the third compression stage 202c, flows through the second communication passage 203b, is compressed in the first compression stage 202a, flows through the first communication passage 203a, and is then compressed in the second compression stage 202b.

Next, in the condenser 204, heat exchange occurs between the gas phase refrigerant and the cooling medium from the outside. This heat exchange causes the gas phase refrigerant to condense, and the resulting liquid phase refrigerant is stored in the condenser 204.

Next, in the third flow path 223, a portion of the liquid-phase refrigerant is vaporized by reducing pressure. In this way, a two-phase gas-liquid refrigerant is generated in the third flow path 223. Next, the flow rate of the two-phase gas-liquid refrigerant is adjusted in the first valve 205. Next, the two-phase gas-liquid refrigerant flows through the fourth flow path 224.

Next, the gas-liquid two-phase refrigerant flows into the first tank 207. The gas-liquid two-phase refrigerant that flows into the first upper space 207u from the first inlet 207i expands. This expansion produces droplets. Specifically, as soon as this expansion occurs, a large volume of gas-phase refrigerant is generated. At this time, the liquid forms a film that envelops the gas-phase refrigerant, thereby forming bubbles. As the volume of the gas-phase refrigerant in the bubbles increases, the bubbles eventually burst. When the bubbles burst, droplets are produced. The resulting droplets are received by the upper surface of the first partition 207a. In this way, gas-liquid separation of the refrigerant is performed in the first tank 207.

In this embodiment, no compressor is provided in the flow path through which the refrigerant flows from when it is discharged from the condenser 204 until it flows into the first tank 207. This is suitable for supplying a two-phase gas-liquid refrigerant to the first tank 207.

The gas-phase refrigerant obtained by gas-liquid separation moves from the first upper space 207u through the first communication port 207c to the first lower space 207d and flows out from the first gas-phase outlet 207og. On the other hand, the liquid-phase refrigerant obtained by gas-liquid separation flows along the first inclined portion 207ai of the first partition 207a, drips from the first communication port 207c into the first lower space 207d, and is stored at the bottom of the first lower space 207d. The stored liquid-phase refrigerant flows out from the first liquid-phase outlet 207ol.

The gas phase refrigerant flowing out of the first gas phase outlet 207og flows into the first gas phase flow path 208. The gas phase refrigerant is then sucked into the suction port of the second compression stage 202b via the first communication passage 203a.

In this embodiment, in the first tank 207, the liquid phase refrigerant flows along the upper surface of the first partition 207a. In this way, the liquid phase refrigerant can be moved while maintaining a large surface area of the liquid phase refrigerant. Therefore, according to this embodiment, it is easy to suppress the boiling phenomenon. This prevents liquid droplets from being mixed into the gas phase refrigerant to be sucked into the second compression stage 202b via the first communication passage 203a, and is therefore suitable for maintaining the performance of the multi-stage compressor 202.

The liquid phase refrigerant flowing out of the first liquid phase outlet 207ol flows into the intermediate flow path 209. In the intermediate flow path 209, a portion of the liquid phase refrigerant is vaporized due to reduced pressure.

Now, suppose that the liquid-phase refrigerant generated by gas-liquid separation in the first tank 207 immediately flows into the second tank 210 through the intermediate flow path 209. In that case, in the first tank 207, the liquid-phase refrigerant is not substantially stored at the bottom of the first lower space 207d. When the first tank 207 is in a state where the liquid-phase refrigerant is not substantially stored, a loop may be formed in which the gas-phase refrigerant flows in the order of the discharge port of the first compression stage 202a, the first communication passage 203a, the first gas-phase flow path 208, the first tank 207, the intermediate flow path 209, the second tank 210, the second gas-phase flow path 211, the second communication passage 203b, and the suction port of the first compression stage 202a. In a state where the gas-phase refrigerant discharged from the first compression stage 202a flows through such a loop instead of being sucked into the second compression stage 202b, the first compression stage 202a is unlikely to contribute to the compression performance of the multi-stage compressor 202. In other words, from the perspective of compression performance, the first compression stage 202a becomes essentially "invisible." For example, if the multi-stage compressor 202 is a three-stage compressor, it may result in a situation where it only exhibits compression performance equivalent to that of a two-stage compressor.

In this respect, in this embodiment, the above-mentioned loop is unlikely to form. Specifically, in the intermediate flow path 209, a low-level portion 209L and a high-level portion 209H appear in order from the first liquid-phase outlet 207ol toward the second inlet 210i. Therefore, when a refrigerant containing a liquid phase component flows from the first liquid-phase outlet 207ol to the second inlet 210i via the intermediate flow path 209, the flow of the refrigerant can be restricted by the water level head difference between the low-level portion 209L and the high-level portion 209H. Therefore, the first tank 207 is unlikely to be in a state where it does not substantially store refrigerant. This can contribute to preventing the above-mentioned loop from being formed and preventing a decrease in the compression performance of the multi-stage compressor 202.

The gas-liquid two-phase refrigerant generated by partial evaporation in the intermediate flow path 209 flows into the second tank 210. The gas-liquid two-phase refrigerant that flows into the second upper space 210u from the second inlet 210i expands. This expansion generates droplets. Specifically, as soon as this expansion occurs, a large volume of gas-phase refrigerant is generated. At this time, the liquid forms a film that envelops the gas-phase refrigerant, thereby forming bubbles. As the volume of the gas-phase refrigerant in the bubbles increases, the bubbles eventually burst. When the bubbles burst, droplets are generated. The resulting droplets are received by the upper surface of the second partition 210a. In this way, gas-liquid separation of the refrigerant is performed in the second tank 210.

The gas-phase refrigerant obtained by gas-liquid separation moves from the second upper space 210u through the second communication port 210c to the second lower space 210d and flows out from the second gas-phase outlet 210og. Meanwhile, the liquid-phase refrigerant obtained by gas-liquid separation flows along the second inclined portion 210ai of the second partition 210a, drips from the second communication port 210c into the second lower space 210d, and is stored at the bottom of the second lower space 210d. The stored liquid-phase refrigerant flows out from the second liquid-phase outlet 210ol.

The gas phase refrigerant flowing out from the second gas phase outlet 210og flows into the second gas phase flow path 211. The gas phase refrigerant is then sucked into the suction port of the first compression stage 202a via the second communication passage 203b.

In this embodiment, in the second tank 210, the liquid phase refrigerant flows along the upper surface of the second partition 210a. In this way, the liquid phase refrigerant can be moved while maintaining a large surface area of the liquid phase refrigerant. Therefore, according to this embodiment, it is easy to suppress the boiling phenomenon. This prevents liquid droplets from being mixed into the gas phase refrigerant to be sucked into the first compression stage 202a via the second communication passage 203b, and is therefore suitable for maintaining the performance of the multi-stage compressor 202.

The liquid phase refrigerant flowing out of the second liquid phase outlet 210ol flows through the fifth flow path 225. Next, the flow rate of the liquid phase refrigerant is adjusted in the second valve 213. Next, the liquid phase refrigerant flows into the evaporator 201.

[1-2-2. Operation in the second state]
The refrigeration cycle apparatus 200 can be in a second state. In the second state, the opening degree of the bypass valve 217 is relatively large. In the present embodiment, the second state is a state in which the opening degree of the bypass valve 217 is fully open. In the present embodiment, the refrigeration cycle apparatus 200 can be in the second state at a small load. Specifically, the refrigeration cycle apparatus 200 can be in the second state at a partial load. In the present embodiment, at a small load, the temperature difference between the refrigerant after evaporation in the evaporator 201 and the refrigerant after condensation in the condenser 204 is small, the rotation speed of the multi-stage compressor 202 is low, and the pressure difference between the compression stages in the multi-stage compressor 202 is small. The partial load state is, for example, when the refrigeration cycle apparatus 200 is started or stopped.

The operation of the refrigeration cycle device 200 in the second state will be described below. Note that the description of the same contents as in the first state will be omitted below.

In the second state, as in the first state, the liquid-phase refrigerant flowing out from the first liquid-phase outlet 207ol flows into the intermediate flow path 209. However, in the second state, the refrigerant that flows into the intermediate flow path 209 flows into the bypass flow path 214 midway through the intermediate flow path 209. The refrigerant flows through the bypass flow path 214 to bypass the high-level portion 209H, and returns to the intermediate flow path 209. In the intermediate flow path 209 and/or the bypass flow path 214, a portion of the liquid-phase refrigerant is vaporized by reduced pressure. The refrigerant that flows through the intermediate flow path 209 and/or the bypass flow path 214 flows into the second tank 210.

In this embodiment, the suction port of the first compression stage 202a is connected to the second gas phase outlet 210og of the second tank 210 via the second communication passage 203b and the second gas phase flow path 211. On the other hand, the discharge port of the first compression stage 202a is connected to the first gas phase outlet 207og of the first tank 207 via the first communication passage 203a and the first gas phase flow path 208. Therefore, under conditions where the pressure difference between the compression stages in the multi-stage compressor 202 is small and the pressure difference between the suction port and the discharge port of the first compression stage 202a is small, the pressure difference between the first internal space 207s of the first tank 207 and the second internal space 210s of the second tank 210 is also small. In this case, it seems difficult to smoothly flow the refrigerant from the first tank 207 to the second tank 210.

However, in this embodiment, the first tank 207 is located higher than the second tank 210. Specifically, the height of the first tank 207 and the height of the second tank 210 are set so that the liquid level of the liquid phase refrigerant stored in the first tank 207 is higher than the liquid level of the liquid phase refrigerant stored in the second tank 210. The water level head difference between the first tank 207 and the second tank 210 obtained in this manner can pressurize the refrigerant flowing from the first tank 207 to the second tank 210. In this way, even if the pressure difference between the compression stages in the multi-stage compressor 202 is small, the refrigerant can flow smoothly from the first tank 207 to the second tank 210.

In the first state, the opening of the bypass valve 217 is relatively small, so that the refrigerant easily flows into the intermediate flow path 209, and the intermediate flow path 209 has a high-level portion 209H. Therefore, in the first state, even if the pressure difference between the compression stages in the multi-stage compressor 202 is large, it is possible to prevent the amount of liquid-phase refrigerant stored in the first tank 207 from becoming excessively small. On the other hand, in the second state, the opening of the bypass valve 217 is relatively large. Therefore, even if the pressure difference between the compression stages in the multi-stage compressor 202 is small, it is possible to sufficiently flow the refrigerant from the first tank 207 to the second tank 210.

In this embodiment, the opening degree of the bypass valve 217 is zero in the first state, while the opening degree of the bypass valve 217 is fully open in the second state. However, the opening degree of the bypass valve 217 may be non-zero in the first state, and non-fully open in the second state. As described above, it can generally be explained that the opening degree of the bypass valve 217 in the first state is smaller than the opening degree of the bypass valve 217 in the second state.

[1-3. Effects, etc.]
The inventors have considered compressing a gas-phase refrigerant containing, as a main component, a component having a saturated vapor pressure equal to or lower than atmospheric pressure at room temperature, by using a multi-stage compressor. In this case, it is considered that the gas-phase refrigerant generated by reducing the pressure of the liquid-phase refrigerant guided from the condenser to the evaporator is guided to a flow path between compression stages of the multi-stage compressor.

When a liquid-phase refrigerant containing as its main component a component with a saturated vapor pressure below atmospheric pressure at room temperature is decompressed, unlike refrigerants such as fluorocarbons, a small change in pressure can cause a large temperature change, and the gas-phase refrigerant can become excessive during expansion. For example, if the refrigerant is water, a pressure loss of 100 Pa can cause a temperature change of about 1°C or more. In addition, boiling can generate water vapor with a volume about 14,500 times the volume of liquid water (Yoshiaki Katto, "Heat Transfer", Vol. 44, No. 187, Japan Society of Heat Transfer, pp. 15-20, see (2) Low-pressure boiling in "The Science of Boiling (2)"). Components with a saturated vapor pressure below atmospheric pressure at room temperature have such characteristics, so as the refrigerant is decompressed, most of the volume of the refrigerant becomes occupied by the gas-phase refrigerant.

Specifically, the inventors have considered a configuration in which two tanks are provided downstream of the condenser and upstream of the evaporator, and these tanks are used to generate gas-phase refrigerant to be introduced between the compression stages of the multi-stage compressor. In this configuration, as soon as refrigerant containing liquid phase components flows into the tank and expands, a large volume of gas-phase refrigerant is generated. At this time, the liquid forms a film that envelops the gas-phase refrigerant, thereby forming bubbles. As the volume of the gas-phase refrigerant in the bubbles increases, the bubbles eventually burst. When the bubbles burst, tiny droplets are generated. A large amount of gas-phase refrigerant and liquid droplets flow into the flow passage between the compression stages of the multi-stage compressor in a state of temperature equilibrium. If the liquid droplets are sucked into the compression stages together with the gas-phase refrigerant, erosion may occur in the compression stages. Erosion may reduce the performance of the multi-stage compressor.

In light of this, the inventors have conducted extensive research into technology to prevent liquid droplets from entering the flow path between compression stages in a refrigeration cycle device in which a refrigerant containing liquid phase components is depressurized as it is guided from a condenser to an evaporator, causing liquid droplets to form as a result of this depressurization. The technology of the embodiment is based on such research.

In this embodiment, the refrigeration cycle device 200 uses a refrigerant containing, as a main component, a component having a saturated vapor pressure equal to or lower than atmospheric pressure at room temperature. The refrigeration cycle device 200 includes, in this order, an evaporator 201, a multi-stage compressor 202, a condenser 204, and a tank 207. The multi-stage compressor 202 has a first compression stage 202a and a second compression stage 202b. The tank 207 has a partition 207a, an upper space 207u, a lower space 207d, a communication port 207c, an inlet 207i, a liquid phase outlet 207ol, and a gas phase outlet 207og. The upper space 207u is located above the partition 207a. The lower space 207d is located below the partition 207a. The communication port 207c communicates the upper space 207u and the lower space 207d. The inlet 207i opens to the upper space 207u. The liquid phase outlet 207ol opens to the lower space 207d. The gas phase outlet 207og opens to the lower space 207d. The gas phase outlet 207og is located higher than the liquid phase outlet 207ol. The refrigerant circulates through the evaporator 201, the first compression stage 202a, the second compression stage 202b, the condenser 204, the inlet 207i, the upper space 207u, the communication port 207c, the lower space 207d, and the liquid phase outlet 207ol in this order. The gas phase refrigerant flows from the gas phase outlet 207og to the second compression stage 202b. According to this configuration, the partition 207a can prevent the liquid droplets from moving from the upper space 207u to the gas phase outlet 207og together with the gas phase refrigerant. Therefore, this configuration is suitable for suppressing the intake of liquid droplets during the compression process of the multi-stage compressor 202. Specifically, this configuration is suitable for suppressing the intake of liquid droplets into the second compression stage 202b. By suppressing the intake of liquid droplets, erosion of the second compression stage 202b is suppressed. This suppresses the performance degradation of the multi-stage compressor 202, and the capacity of the refrigeration cycle device 200 can be stabilized.

In this embodiment, the two-phase gas-liquid refrigerant flows into the upper space 207u from the inlet 207i. In the upper space 207u, the two-phase gas-liquid refrigerant is depressurized to generate droplets, which are received by the upper surface of the partition 207a, causing the two-phase gas-liquid refrigerant to be separated into gas and liquid. The liquid-phase refrigerant flows along the upper surface of the partition 207a and drips from the communication port 207c, where it is stored in the lower space 207d, and then flows out from the liquid-phase outlet 207ol. The gas-phase refrigerant moves from the upper space 207u to the gas-phase outlet 207og via the communication port 207c and the lower space 207d in this order.

When the tank 207 is observed from above, the straight line connecting the gas phase outlet 207og and the inlet 207i is defined as the first straight line 207x, and the straight line perpendicular to the first straight line 207x and passing through the inlet 207i is defined as the second straight line 207y. In this embodiment, when the tank 207 is observed from above, the gas phase outlet 207og and the communication port 207c are on opposite sides of each other with respect to the second straight line 207y. With this configuration, the communication port 207c can be provided at a position far from the gas phase outlet 207og. For this reason, it is easy to prevent liquid droplets from moving from the upper space 207u to the gas phase outlet 207og through the communication port 207c and the lower space 207d in this order together with the gas phase refrigerant. Therefore, this configuration is suitable for suppressing the inhalation of liquid droplets during the compression process of the multi-stage compressor 202. Specifically, this configuration is suitable for suppressing the intake of droplets into the second compression stage 202b.

In this embodiment, the partition 207a includes an inclined portion 207ai at a position adjacent to the communication port 207c. The height of the inclined portion 207ai decreases as it approaches the communication port 207c. With this configuration, the liquid phase refrigerant can easily flow smoothly along the upper surface of the partition 207a to the communication port 207c. In addition, with this configuration, the liquid phase refrigerant that has reached the communication port 207c along the upper surface of the partition 207a can be prevented from moving along the lower surface of the partition 207a to the gas phase outlet 207og. Therefore, this configuration is suitable for suppressing the intake of droplets during the compression process of the multi-stage compressor 202. Specifically, this configuration is suitable for suppressing the intake of droplets into the second compression stage 202b. The droplet intake suppression effect based on this configuration is particularly likely to occur when the distance between the gas phase outlet 207og and the communication port 207c is secured.

As described above, the tank 207 can be referred to as the first tank 207. The partition 207a can be referred to as the first partition 207a. The upper space 207u can be referred to as the first upper space 207u. The lower space 207d can be referred to as the first lower space 207d. The communication port 207c can be referred to as the first communication port 207c. The inlet 207i can be referred to as the first inlet 207i. The liquid phase outlet 207ol can be referred to as the first liquid phase outlet 207ol. The gas phase outlet 207og can be referred to as the first gas phase outlet 207og.

In this embodiment, the refrigeration cycle device 200 includes a second tank 210. The multi-stage compressor 202 includes a third compression stage 202c. The second tank 210 includes a second partition 210a, a second upper space 210u, a second lower space 210d, a second communication port 210c, a second inlet 210i, a second liquid phase outlet 210ol, and a second gas phase outlet 210og. The second upper space 210u is located above the second partition 210a. The second lower space 210d is located below the second partition 210a. The second communication port 210c communicates the second upper space 210u and the second lower space 210d. The second inlet 210i opens into the second upper space 210u. The second liquid phase outlet 210ol opens into the second lower space 210d. The second gas phase outlet 210og is open to the second lower space 210d. The second gas phase outlet 210og is located at a higher position than the second liquid phase outlet 210ol. The refrigerant circulates through the evaporator 201, the third compression stage 202c, the first compression stage 202a, the second compression stage 202b, the condenser 204, the first inlet 207i, the first upper space 207u, the first communication port 207c, the first lower space 207d, the first liquid phase outlet 207ol, the second inlet 207i, the second upper space 210u, the second communication port 210c, the second lower space 210d, and the second liquid phase outlet 210ol in this order. The gas phase refrigerant flows from the second gas phase outlet 210og to the first compression stage 202a. This configuration is suitable for suppressing the intake of liquid droplets during the compression process of the multi-stage compressor 202. Specifically, this configuration is suitable for suppressing the intake of droplets into the first compression stage 202a.

In this embodiment, the gas-liquid two-phase refrigerant flows into the second upper space 210u from the second inlet 210i. In the second upper space 210u, the gas-liquid two-phase refrigerant is depressurized to generate droplets, which are received by the upper surface of the second partition 210a, causing the gas-liquid two-phase refrigerant to be separated into gas and liquid. The liquid phase refrigerant flows along the upper surface of the second partition 210a and drips from the second communication port 210c, thereby being stored in the second lower space 210d, and then flows out from the second liquid phase outlet 210ol. The gas phase refrigerant moves from the second upper space 210u to the second gas phase outlet 210og via the second communication port 210c and the second lower space 210d in this order.

When the second tank 210 is observed from above, the straight line connecting the second gas phase outlet 210og and the second inlet 210i is defined as the third straight line 210x, and the straight line perpendicular to the third straight line 210x and passing through the second inlet 210i is defined as the fourth straight line 210y. In this embodiment, when the second tank 210 is observed from above, the second gas phase outlet 210og and the second communication port 210c are on opposite sides of the fourth straight line 210y. According to this configuration, the second communication port 210c can be provided at a position far from the second gas phase outlet 210og. Therefore, it is easy to prevent liquid droplets from moving from the second upper space 210u to the second gas phase outlet 210og through the second communication port 210c and the second lower space 210d in this order together with the gas phase refrigerant. Therefore, this configuration is suitable for suppressing the inhalation of liquid droplets during the compression process of the multi-stage compressor 202. Specifically, this configuration is suitable for suppressing the intake of droplets into the first compression stage 202a.

In this embodiment, the second partition 210a includes a second inclined portion 210ai at a position adjacent to the second communication port 210c. The height of the second inclined portion 210ai decreases as it approaches the second communication port 210c. With this configuration, the liquid phase refrigerant can easily flow smoothly along the upper surface of the second partition 210a to the second communication port 210c. In addition, with this configuration, the liquid phase refrigerant that has reached the second communication port 210c along the upper surface of the second partition 210a can be prevented from moving along the lower surface of the second partition 210a to the second gas phase outlet 210og. For this reason, this configuration is suitable for suppressing the intake of liquid droplets during the compression process of the multi-stage compressor 202. Specifically, this configuration is suitable for suppressing the intake of liquid droplets into the first compression stage 202a. The droplet suction suppression effect based on this configuration is particularly likely to occur when a sufficient distance is maintained between the second gas phase outlet 210og and the second communication port 210c.

In this embodiment, the refrigeration cycle device 200 is provided with an intermediate flow path 209. The intermediate flow path 209 connects the first liquid phase outlet 207ol and the second inlet 210i. The intermediate flow path 209 has a low-level portion 209L and a high-level portion 209H. The high-level portion 209H is located higher than the low-level portion 209L. The refrigerant flows through the first liquid phase outlet 207ol, the low-level portion 209L, the high-level portion 209H, and the second inlet 210i in this order. According to this configuration, when a refrigerant containing a liquid phase component flows from the first liquid phase outlet 207ol through the intermediate flow path 209 to the second inlet 210i, the flow of the refrigerant can be restricted by the water level head difference between the low-level portion 209L and the high-level portion 209H. Therefore, it is difficult for the first tank 207 to be in a state where the liquid phase refrigerant is not substantially stored. Therefore, it is difficult to form a loop in which the gas phase refrigerant discharged from the first compression stage 202a passes through the first gas phase outlet 207og of the first tank 207, the first lower space 207d, the first liquid phase outlet 207ol, the intermediate flow path 209, the second inlet 210i of the second tank 210, the second upper space 210u, the second communication port 210c, the second lower space 210d, and the second gas phase outlet 210og in this order, and returns to the first compression stage 202a. Therefore, it is easy to ensure the performance of the multi-stage compressor 202.

In this embodiment, the refrigeration cycle device 200 includes a bypass flow path 214 and a bypass valve 217. The bypass flow path 214 extends at a position lower than the high-level portion 209H. The bypass valve 217 is provided in the bypass flow path 214. When the opening degree of the bypass valve 217 is greater than zero, the refrigerant bypasses the high-level portion 209H and flows through the first liquid phase outlet 207ol, the bypass flow path 214, and the second inlet 210i in this order. With this configuration, the opening degree of the bypass valve 217 can be adjusted to operate the refrigeration cycle device 200 appropriately, both under low-load conditions where the pressure difference between the compression stages of the multi-stage compressor 202 is small, and under high-load conditions where the pressure difference is large.

As described above, the first embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can also be applied to embodiments in which changes, rewrites, additions, omissions, etc. have been made.

The technology of the refrigeration cycle device disclosed herein prevents water droplets from flowing between the compression stages of a multi-stage compressor, making it possible to maintain the performance of the multi-stage compressor. This technology can also be applied to applications such as air conditioners, chillers, and heat storage devices that use refrigeration cycle devices.

100 Refrigeration cycle device 101 Evaporator 102 Multi-stage compressor 102a First compression stage 102b Second compression stage 103 Condenser 104a First expansion valve 104b Second expansion valve 105 Economizer heat exchanger 106a First flow path 106b Second flow path 200 Refrigeration cycle device 201 Evaporator 202 Multi-stage compressor 202a First compression stage 202b Second compression stage 202c Third compression stage 203a First communication passage 203b Second communication passage 204 Condenser 205 First valve 207 First tank 207a First partition 207ai First inclined portion 207s First internal space 207u First upper space 207d First lower space 207c First communication port 207bw First bottom wall 207sw First side wall 207cw First ceiling wall 207i First inlet 207ol First liquid phase outlet 207og First gas phase outlet 207x First straight line 207y Second straight line 208 First gas phase flow path 209 Intermediate flow path 209L Low level section 209H High level section 210 Second tank 210a Second partition 210ai Second inclined section 210s Second internal space 210u Second upper space 210d Second lower space 210c Second communication port 210bw Second bottom wall 210sw Second side wall 210cw Second ceiling wall 210i Second inlet 210ol Second liquid phase outlet 210og Second gas phase outlet 210x Third straight line 210y Fourth straight line 211 Second gas phase flow path 213 Second valve 214 Bypass flow path 217 Bypass valve 221 First flow path 222 Second flow path 223 Third flow path 224 Fourth flow path 225 Fifth flow path

Claims (6)

A refrigeration cycle device that uses a refrigerant containing, as a main component, a component having a saturated vapor pressure equal to or lower than atmospheric pressure at room temperature,
An evaporator;
A multi-stage compressor;
A condenser;
The first tank,
In this order,
The multi-stage compressor has a first compression stage and a second compression stage,
the first tank has a first partition, a first upper space located above the first partition, a first lower space located below the first partition, a first communication port connecting the first upper space and the first lower space, a first inlet opening into the first upper space, a first liquid phase outlet opening into the first lower space, and a first gas phase outlet opening into the first lower space and located at a higher position than the first liquid phase outlet,
the refrigerant circulates through the evaporator, the first compression stage, the second compression stage, the condenser, the first inlet, the first upper space, the first communication port, the first lower space, and the first liquid phase outlet in this order;
the refrigerant in a gas phase flows from the first gas phase outlet to the second compression stage;
The refrigerant in a gas-liquid two-phase state flows into the first upper space from the first inlet,
In the first upper space, bubbles formed by the gas-liquid two-phase refrigerant being decompressed and expanding burst, generating liquid droplets, which are received by the upper surface of the first partition, causing the gas-liquid two-phase refrigerant to separate into gas and liquid,
the refrigerant in a liquid phase flows along the upper surface of the first partition and drips from the first communication port to be stored in the first lower space, and then flows out from the first liquid phase outlet,
The refrigerant in a gas phase moves from the first upper space through the first communication port and the first lower space in this order to the first gas phase outlet.
Refrigeration cycle equipment. A refrigeration cycle device that uses a refrigerant containing, as a main component, a component having a saturated vapor pressure equal to or lower than atmospheric pressure at room temperature,
An evaporator;
A multi-stage compressor;
A condenser;
The first tank,
In this order,
The multi-stage compressor has a first compression stage and a second compression stage,
the first tank has a first partition, a first upper space located above the first partition, a first lower space located below the first partition, a first communication port connecting the first upper space and the first lower space, a first inlet opening into the first upper space, a first liquid phase outlet opening into the first lower space, and a first gas phase outlet opening into the first lower space and located at a higher position than the first liquid phase outlet,
the refrigerant circulates through the evaporator, the first compression stage, the second compression stage, the condenser, the first inlet, the first upper space, the first communication port, the first lower space, and the first liquid phase outlet in this order;
the refrigerant in a gas phase flows from the first gas phase outlet to the second compression stage;
The refrigeration cycle apparatus further includes a second tank,
The multi-stage compressor further comprises a third compression stage,
the second tank has a second partition, a second upper space located above the second partition, a second lower space located below the second partition, a second communication port connecting the second upper space and the second lower space, a second inlet opening into the second upper space, a second liquid phase outlet opening into the second lower space, and a second gas phase outlet opening into the second lower space and located at a higher position than the second liquid phase outlet,
the refrigerant circulates through the evaporator, the third compression stage, the first compression stage, the second compression stage, the condenser, the first inlet, the first upper space, the first communication port, the first lower space, the first liquid phase outlet, the second inlet, the second upper space, the second communication port, the second lower space, and the second liquid phase outlet in this order;
the refrigerant in a gas phase flows from the second gas phase outlet to the first compression stage;
The refrigeration cycle apparatus further includes an intermediate flow path connecting the first liquid phase outlet and the second inlet,
The intermediate flow path has a low portion and a high portion located higher than the low portion,
The refrigerant flows through the first liquid phase outlet, the lower portion, the higher portion, and the second inlet in this order.
Refrigeration cycle equipment. The refrigeration cycle apparatus further includes a bypass flow path extending at a position lower than the high-level portion, and a bypass valve provided in the bypass flow path,
When the opening degree of the bypass valve is greater than zero, the refrigerant bypasses the high-level portion and flows through the first liquid phase outlet, the bypass flow path, and the second inlet in this order.
The refrigeration cycle device according to claim 2. The refrigerant in a gas-liquid two-phase state flows into the first upper space from the first inlet,
In the first upper space, the refrigerant in a gas-liquid two-phase state is decompressed to generate liquid droplets, and the liquid droplets are received by the upper surface of the first partition, whereby the refrigerant in a gas-liquid two-phase state is separated into gas and liquid,
the refrigerant in a liquid phase flows along the upper surface of the first partition and drips from the first communication port to be stored in the first lower space, and then flows out from the first liquid phase outlet,
The refrigerant in a gas phase moves from the first upper space through the first communication port and the first lower space in this order to the first gas phase outlet.
The refrigeration cycle device according to claim 2 or 3. When the first tank is observed from above, the first gas phase outlet and the first communication port are located on opposite sides to each other with respect to a second line that is perpendicular to a first line connecting the first gas phase outlet and the first inlet and passes through the first inlet.
The refrigeration cycle device according to any one of claims 1 to 4. The first partition includes an inclined portion having a height decreasing toward the first communication port at a position adjacent to the first communication port.
The refrigeration cycle device according to any one of claims 1 to 5.

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