JP7123238B2 - refrigeration cycle equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a refrigeration cycle device, and more particularly to connection between a heat exchanger functioning as an evaporator and an expansion device.

An air conditioner, which is a type of refrigeration cycle system, is a type of refrigeration cycle system that, in heating operation, heats and cools high-temperature, high-pressure gas refrigerant discharged from a compressor with indoor air through an indoor heat exchanger that functions as a condenser. Phase change to high pressure liquid refrigerant. Thereafter, the low-temperature and high-pressure liquid refrigerant is phase-changed into a low-temperature and low-pressure two-phase refrigerant in the expansion device. The two-phase refrigerant is heated by exchanging heat with air in an outdoor heat exchanger that functions as an evaporator, changes phase to a low-temperature, low-pressure gas refrigerant, and is sucked into the compressor. Then, the low-temperature, low-pressure gas refrigerant is compressed by a compressor and discharged again as a high-temperature, high-pressure gas refrigerant.

Here, when the air conditioner is operated for heating, if the temperature of the outside air where the outdoor heat exchanger is installed approaches below the freezing point, the surface temperature of the outdoor heat exchanger is lowered below the freezing point in order to maintain the heat exchange performance. also goes down. At this time, frost may adhere to the outdoor heat exchanger. Defrosting becomes necessary when the amount of frost adhering to the outdoor heat exchanger increases. For example, the defrosting operation of the outdoor heat exchanger is performed by a method such as allowing hot gas to flow into the outdoor heat exchanger. Generally, the drain water generated by defrosting drips onto the drain pan and is drained. However, water may accumulate at the lower end of the heat exchanger due to stagnation of drainage in the drain pan or the effect of surface tension. In a state where water remains in the heat exchanger, the accumulated drain water may freeze and damage the outdoor heat exchanger during the heating operation. Therefore, a method is known in which a heater is installed in the drain pan to prevent the outdoor heat exchanger from freezing.

For example, in the air conditioner disclosed in Patent Document 1, the refrigerant having a higher pressure (temperature) than the upper portion of the heat exchanger flows through the lower portion of the heat exchanger, thereby causing the drain pan and the lower portion of the heat exchanger to flow. It suppresses frost formation and freezing.

Japanese Utility Model Publication No. 5-44653

However, in the air conditioner disclosed in Patent Document 1, for example, in order to further improve the heat transfer performance of the heat exchanger, or to reduce the amount of refrigerant flowing through the heat transfer tube constituting the heat exchanger, the heat transfer tube may reduce the cross-sectional area of For example, it is possible to reduce the outer diameter of a heat transfer tube formed of a circular tube, or to make the cross section of the tube flat and to make the flow path in the tube narrow and multi-hole. In the air conditioner according to the patent document, when the cross-sectional area of the flow path of the heat transfer tube constituting the heat exchanger is reduced, the flow path resistance is large in the lower part of the heat exchanger where the number of branches of the refrigerant flow path is small. There was a problem of becoming

An object of the present invention is to solve the above-described problems, and to provide a refrigeration cycle apparatus that can suppress freezing of the lower part of a heat exchanger where drain water tends to stay, even when the diameter of the heat transfer tube is reduced. with the aim of obtaining

A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit in which a compressor, a first expansion device, and a first heat exchanger that functions as an evaporator during heating operation are connected by refrigerant piping, and the first heat The exchanger includes a first heat exchange section, a second heat exchange section connected in series to the first heat exchange section in the refrigerant circuit, and between the first heat exchange section and the second heat exchange section. and a second expansion device connected to the refrigerant circuit, wherein the first expansion device is connected to the refrigerant circuit so that the refrigerant flows in from the second heat exchange portion side during heating operation, and the first expansion device is connected to the refrigerant circuit in the The second expansion device is connected in parallel with a second heat exchange section, the second heat exchange section is positioned below the first heat exchange section, and the second expansion device is arranged in parallel with the first expansion device in the refrigerant circuit. connected and connected in series with the second heat exchange section.

According to the present invention, with the above configuration, the cross-sectional area of the refrigerant flow path of the heat transfer tube of the heat exchanger is reduced, thereby reducing the amount of refrigerant flowing through the refrigerant circuit and suppressing freezing of the drain pan and the lower part of the heat exchanger. can do.

1 is a circuit diagram of a refrigerant circuit 1 of a refrigeration cycle device 100 according to Embodiment 1. FIG. 2 is a perspective view of first heat exchanger 10 of refrigeration cycle apparatus 100 according to Embodiment 1. FIG. FIG. 3 is an explanatory diagram of a cross-sectional structure of the first heat exchanger 10 of FIG. 2; FIG. 2 is an explanatory diagram of the structure of the first heat exchanger 10 according to Embodiment 1 as viewed from the front; 1 shows a cross-sectional view of a flat tube that is an example of a heat transfer tube 20 used in the first heat exchanger 10 of Embodiment 1. FIG. 2 is a circuit diagram of refrigerant circuit 101 of refrigerating cycle device 1100 that is a comparative example of refrigerating cycle device 100 of Embodiment 1. FIG. FIG. 3 is a perspective view of a first heat exchanger 110 of a refrigeration cycle device 1100 according to a comparative example; FIG. 11 is a diagram showing characteristics during heating operation of the refrigeration cycle device 1100 of the comparative example; FIG. 4 is a diagram showing characteristics during heating operation of the refrigeration cycle apparatus 100 according to Embodiment 1; 10 is an enlarged view of part A of FIG. 9. FIG. FIG. 4 is a circuit diagram of a refrigerant circuit 201 of a refrigeration cycle device 200 according to Embodiment 2; FIG. 11 is a perspective view of first heat exchanger 210 of refrigeration cycle apparatus 200 according to Embodiment 2; FIG. 10 is a diagram showing characteristics during heating operation of the refrigeration cycle device 200 according to Embodiment 2; FIG. 10 is a diagram showing characteristics during heating operation of the refrigeration cycle device 200 according to Embodiment 2; FIG. 11 is a circuit diagram of a refrigerant circuit 301 of a refrigeration cycle device 300 according to Embodiment 3; FIG. 11 is a perspective view of first heat exchanger 310 of refrigeration cycle apparatus 300 according to Embodiment 3; FIG. 12 is a diagram showing characteristics during heating operation of the refrigeration cycle device 300 according to Embodiment 3; FIG. 12 is a diagram showing characteristics during heating operation of the refrigeration cycle device 300 according to Embodiment 3; FIG. 11 is a circuit diagram of a refrigerant circuit 401 of a refrigeration cycle device 400 according to Embodiment 4; FIG. 11 is a perspective view of first heat exchanger 410 of refrigeration cycle apparatus 400 according to Embodiment 4; FIG. 11 is a diagram showing characteristics during heating operation of a refrigeration cycle device 400 according to Embodiment 4;

An embodiment of a refrigeration cycle apparatus will be described below. In addition, the form of drawing is an example and does not limit this invention. In addition, the same reference numerals in each drawing are the same or equivalent, and this is common throughout the specification. Furthermore, in the drawings below, the size relationship of each component may differ from the actual size.

Embodiment 1.
FIG. 1 is a circuit diagram of a refrigerant circuit 1 of a refrigeration cycle device 100 according to Embodiment 1. FIG. A refrigeration cycle device 100 shown in FIG. 1 is, for example, an air conditioner. As shown in FIG. 1, the refrigeration cycle device 100 connects a compressor 2, a four-way valve 7, a first heat exchanger 10, a first expansion device 5, and a second heat exchanger 3 by refrigerant pipes to The circuit 1 is constructed. For example, when the refrigerating cycle device 100 is an air conditioner, refrigerant flows in the refrigerant piping, and the four-way valve 7 switches the refrigerant flow to switch between heating operation and cooling operation or defrosting operation. can be done. In Embodiment 1, an air conditioner is exemplified as the refrigerating cycle device 100, but the refrigerating cycle device 100 is, for example, a refrigerator, a freezer, a vending machine, an air conditioner, a refrigerating device, a water heater, or the like. It is used for applications or air conditioning applications.

The compressor 2, the second heat exchanger 3, the first expansion device 5, the first heat exchanger 10, and the four-way valve 7 constitute a refrigerant circuit 1 through which refrigerant can circulate. In the refrigeration cycle device 100, a refrigeration cycle is performed in which the refrigerant circulates in the refrigerant circuit 1 while undergoing phase changes. The compressor 2 compresses the refrigerant. The compressor 2 is, for example, a rotary compressor, a scroll compressor, a screw compressor, a reciprocating compressor, or the like.

The first heat exchanger 10 functions as an evaporator when the refrigerating cycle device 100 performs a heating operation, and functions as a condenser when the refrigerating cycle device 100 performs a cooling operation. The first heat exchanger 10 is composed of a first heat exchange section 11 and a second heat exchange section 12 . The second heat exchange section 12 is positioned below the first heat exchange section 11 .

The second heat exchanger 3 functions as a condenser when the refrigeration cycle device 100 performs heating operation, and functions as an evaporator when the refrigeration cycle device 100 performs cooling operation. However, the second heat exchanger 3 may partially act as an evaporator when the refrigerant temperature drops due to pressure loss in the pipe during heating operation. The first heat exchanger 10 and the second heat exchanger 3 are, for example, fin-and-tube heat exchangers, microchannel heat exchangers, finless heat exchangers, shell-and-tube heat exchangers, and heat pipe heat exchangers. , a double tube heat exchanger, or a plate heat exchanger.

The first expansion device 5 expands and decompresses the refrigerant. The first expansion device 5 is, for example, an electric expansion valve capable of adjusting the flow rate of refrigerant. The first expansion device 5 may be not only an electric expansion valve but also a mechanical expansion valve employing a diaphragm as a pressure receiving portion, a capillary tube, or the like.

The four-way valve 7 switches the flow path of the refrigerant in the refrigeration cycle device 100 and changes the circulation direction of the refrigerant in the refrigerant circuit 1 . The four-way valve 7 is switched to connect the discharge port of the compressor 2 and the second heat exchanger 3 and to connect the suction port of the compressor 2 and the first heat exchanger 10 during the heating operation. Further, the four-way valve 7 connects the discharge port of the compressor 2 and the first heat exchanger 10 and connects the suction port of the compressor 2 and the second heat exchanger 3 during the cooling operation and the dehumidifying operation. can be switched to

A blower 6 is arranged near the first heat exchanger 10 . Further, the second heat exchanger 3 has an air blower 4 arranged in the vicinity thereof. Here, the first heat exchanger 10 is an outdoor heat exchanger mounted on the outdoor unit, and the blower 6 sends outside air to the first heat exchanger 10 to exchange heat between the outside air and the refrigerant. . In addition, the second heat exchanger 3 is an indoor heat exchanger mounted on the indoor unit, and the blower 4 introduces indoor air into the housing of the indoor unit and sends the indoor air to the indoor heat exchanger. , heat exchange between the indoor air and the refrigerant to balance the temperature of the indoor air.

The configuration of the refrigerant circuit 1 of the refrigeration cycle apparatus 100 according to Embodiment 1 will be described based on the refrigerant flow in the cooling and heating operation states. In cooling operation, refrigerant discharged from the compressor 2 flows through the four-way valve 7 into the first heat exchange section 11 of the first heat exchanger 10 . The refrigerant flowing out of the first heat exchange section 11 branches into two refrigerant flow paths, one of which passes through the first expansion device 5 and the other of which passes through the second heat exchange section 12 . After that, the refrigerant that has passed through the first expansion device 5 and the refrigerant that has passed through the second heat exchange section 12 join, pass through the second heat exchanger 3 and the four-way valve 7 in that order, and are sucked into the compressor 2 .

On the other hand, in heating operation, the refrigerant discharged from the compressor 2 flows through the four-way valve 7 into the second heat exchanger 3 . The refrigerant flowing out of the second heat exchanger 3 branches into two refrigerant flow paths, one of which passes through the first expansion device 5 and the other of which passes through the second heat exchange section 12 of the first heat exchanger 10. . After that, the refrigerant that has passed through the first expansion device 5 and the refrigerant that has passed through the second heat exchange section 12 merge, pass through the first heat exchange section 11 and the four-way valve 7 in that order, and are sucked into the compressor 2 .

The refrigerant circuit 1 of the refrigeration cycle device 100 includes a branching portion 90 where the refrigerant pipe branches between the second heat exchanger 3 and the first heat exchanger 10 and the first expansion device 5 . That is, no other expansion device is provided between the second heat exchanger 3 and the branch portion 90 .

(Structure of first heat exchanger 10)
FIG. 2 is a perspective view of the first heat exchanger 10 of the refrigeration cycle apparatus 100 according to Embodiment 1. FIG. FIG. 2 schematically shows a part of refrigerant pipes connected to the first heat exchanger 10 . As shown in FIG. 2 , the first heat exchanger 10 includes a first heat exchange section 11 and a second heat exchange section 12 . The second heat exchange section 12 is positioned below the first heat exchange section 11 .

The first heat exchange section 11 and the second heat exchange section 12 are each provided with two heat exchange sections arranged in series in the flow direction of the air flowing into the first heat exchanger 10 . The first heat exchange section 11 includes a first windward heat exchange section 11a as a heat exchange section located on the windward side, and a first leeward heat exchange section 11b as a heat exchange section located on the leeward side. The first windward heat exchange section 11a and the first leeward heat exchange section 11b are connected by a header 14 at their ends. When the first heat exchanger 10 functions as an evaporator, the refrigerant that has flowed out of the first leeward heat exchange section 11b is configured to flow into the first windward heat exchange section 11a.

The second heat exchange section 12 includes a second windward heat exchange section 12a as a heat exchange section located on the windward side, and a second leeward heat exchange section 12b as a heat exchange section located on the leeward side. The second windward heat exchange section 12a and the second leeward heat exchange section 12b are connected by a header 14 at their ends. When the first heat exchanger 10 functions as an evaporator, the refrigerant that has flowed out of the second windward heat exchange section 12a is configured to flow into the second leeward heat exchange section 12b.

The first heat exchange section 11 and the second heat exchange section 12 that constitute the first heat exchanger 10 each include a heat transfer tube 20 . The heat transfer tubes 20 are arranged in parallel in the z-direction shown in FIG. In Embodiment 1, the z-axis is along the direction of gravity. However, the first heat exchanger 10 is not limited to being installed with the z direction aligned with the direction of gravity, and may be installed with the z direction inclined, for example. In other words, it is sufficient that the plurality of heat transfer tubes 20 are arranged in parallel in the vertical direction.

The header 14 connects the upper header 14a that connects the first windward heat exchange section 11a and the first leeward heat exchange section 11b, and the second windward heat exchange section 12a and the second leeward heat exchange section 12b. and a lower header 14b. The header 14 is integrally formed with an upper header 14a and a lower header 14b. are formed so that they do not mix.

Note that the first windward heat exchange section 11 a and the first leeward heat exchange section 11 b may not be connected by the header 14 . For example, the heat transfer tubes 20 of the first windward heat exchange section 11a and the heat transfer tubes 20 of the first leeward heat exchange section 11b may be connected to each other by a U-shaped tube. Similarly, the second windward heat exchange section 12a and the second leeward heat exchange section 12b may not be connected by the header 14, and the ends of the heat transfer tubes 20 are connected by U-shaped tubes. can be

In FIG. 2 , the first heat exchange section 11 has a plurality of heat transfer tubes 20 . The first windward heat exchange section 11 a and the first leeward heat exchange section 11 b each include the same number of heat transfer tubes 20 and are connected by a header 14 . A plurality of heat transfer tubes 20 are arranged in parallel in the z direction. Further, the plurality of heat transfer tubes 20 of the first windward heat exchange section 11a are connected to the windward collecting pipe 13a at the ends in the y direction. The plurality of heat transfer tubes 20 of the first leeward heat exchange section 11b are also connected to the leeward collecting pipe 13b at their ends in the y direction. The collecting pipes 13 a and 13 b are connected to refrigerant pipes forming the refrigerant circuit 1 and serve as an inflow portion or an outflow portion of the refrigerant to the first heat exchange section 11 . Incidentally, the collection pipes 13a and 13b may be divided into a plurality of pieces. For example, among the plurality of heat transfer tubes 20 of the first leeward heat exchange section 11b, the upper three heat transfer tubes 20, the middle three heat transfer tubes 20, and the lower three heat transfer tubes 20 are separated from each other. It may be connected to a collecting pipe.

The second windward heat exchange section 12 a and the second leeward heat exchange section 12 b that constitute the second heat exchange section 12 in FIG. 2 each have one heat transfer tube 20 . However, the second windward heat exchange section 12 a and the second leeward heat exchange section 12 b may have a plurality of heat transfer tubes 20 .

In Embodiment 1, the first heat exchange section 11 has nine heat transfer tubes 20 arranged in the z direction, and the second heat exchange section 12 has one heat transfer tube 20 in the z direction. That is, the number of heat transfer tubes 20 arranged in parallel in the first heat exchange section 11 is greater than the number of heat transfer tubes 20 arranged in parallel in the second heat exchange section 12 . Note that the number of heat transfer tubes 20 is not limited to this. The number of refrigerant passages in each of the first heat exchange section 11 and the second heat exchange section 12 can be set as appropriate. However, the number of refrigerant passages in the first heat exchanging portion 11 positioned at the top is greater than the number of refrigerant passages in the second heat exchanging portion 12 .

Here, the operation of the first heat exchanger 10 when the refrigeration cycle device 100 is in heating operation will be described. In the refrigeration cycle device 100, the high-pressure liquid refrigerant condensed in the second heat exchanger 3, at least part of which functions as a condenser, is branched into two at the branching portion 90 of the refrigerant pipe, and is supplied to the first expansion device 5. The air is branched in parallel to the connected circuit and the bypass circuit 95 connected to the second windward heat exchange section 12a. The refrigerant that has flowed into the first expansion device 5 is expanded, that is, depressurized, and becomes a low-temperature gas-liquid two-phase refrigerant. The refrigerant that has flowed out of the first expansion device 5 joins with the refrigerant that has passed through the second leeward heat exchange section 12b. In general, when the refrigerant passes through a device such as the first expansion device 5, depending on the flow path shape of the first expansion device 5, the amount of refrigerant circulating in the refrigerant circuit 1, and the flow mode of the refrigerant, A certain flow resistance occurs. The flow mode of a refrigerant is a physical property of the refrigerant, and changes depending on the state of the refrigerant, such as gas phase, liquid phase, or gas-liquid two-phase. Also, the flow resistance of the first expansion device 5 causes pressure loss in the flow of refrigerant passing through the first expansion device 5 . That is, the pressure of the refrigerant that has passed through the first expansion device 5 is lowered.

On the other hand, the refrigerant that has flowed into the second windward heat exchange section 12a flows through the heat transfer tubes 20 and flows into the header 14 for moving from the second windward heat exchange section 12a to the second leeward heat exchange section 12b. do. The header 14 has an internal space divided corresponding to the positions of the plurality of heat transfer tubes 20 arranged in parallel in the z-direction. The internal space of the header 14 is divided, and a lower header 14b is formed below the header 14. As shown in FIG. The lower header 14b connects the heat transfer tubes 20 of the second windward heat exchange section 12a and the heat transfer tubes 20 of the second leeward heat exchange section 12b. The refrigerant that has passed through the lower header 14 b flows into the second leeward heat exchange portion 12 b , flows through the heat transfer tubes 20 , and then joins with the refrigerant that has passed through the first expansion device 5 .

Here, as in the first expansion device 5 described above, the heat transfer tubes 20 also have a predetermined flow resistance when the refrigerant flows through the heat transfer tubes 20 . The flow resistance is generated according to the flow path shape in the heat transfer tubes 20, the circulation amount of the refrigerant in the refrigerant circuit 1, and the flow mode of the refrigerant, and causes pressure loss in the flow of the refrigerant. The refrigerant that has passed through the second heat exchange section 12 and the refrigerant that has passed through the first expansion device 5 join and flow into the first heat exchange section 11 . The first heat exchange section 11 has a plurality of heat transfer tubes 20 . For example, the refrigerant is distributed to the plurality of heat transfer tubes 20 by the leeward collecting pipe 13b, and the refrigerant flows into the respective heat transfer tubes 20 in parallel. The refrigerant flowing into the heat transfer tubes 20 in parallel passes through the first leeward heat exchange section 11b, passes through the upper header 14a, and flows into the first windward heat exchange section 11a. The refrigerant that has passed through the plurality of heat transfer tubes 20 of the first windward heat exchange section 11a joins at the windward collecting pipe 13a. That is, the refrigerant that has branched into a plurality of refrigerant flow paths in the first heat exchange section 11 merges in the windward collecting pipe 13 a and flows out of the first heat exchanger 10 . The refrigerant that has flowed out of the first heat exchanger 10 is sucked into the compressor 2 through the four-way valve 7 .

Here, the circulation amount ratio of the refrigerant branched to each of the first expansion device 5 and the second heat exchange section 12 is determined by the pressure loss generated in the first expansion device 5 and the pressure loss generated in the second heat exchange section 12. The ratio will be equal. That is, the circulation rate ratio of the refrigerant fluctuates depending on the flow path shape of each of the first expansion device 5 and the second heat exchange section 12, the pressure reduction of the refrigerant, and the change in the flow mode due to the heat balance. As an example, when the refrigerant flow mode is a single-phase state of liquid or gas, the pressure loss ΔP is expressed by the following equation.

Here, ΔP: pressure loss [Pa], λ: friction loss coefficient, L: channel length [m], d: equivalent diameter of channel [m], G: mass velocity [kg / (m ² s )], ρ: working fluid density [kg/m ³ ], Re: Reynolds number [-]. In addition, the friction loss coefficient λ is determined according to the range of values that the Reynolds number Re takes.
λ=64/Re (Re<2300)
or
λ = ^0.3164 Re-0.25 (2300 < Re)
is represented by

Note that the equivalent diameter d of the flow path is the diameter of the coolant flow path when the cross-sectional shape of the coolant flow path is circular. If the coolant channel is not circular, the equivalent diameter d is expressed as d=4 A/l based on the cross-sectional area of the coolant channel and the length of the edge of the cross-sectional shape of the coolant channel. At this time, A: channel cross-sectional area [Pa], l: channel edge length [m]. The equivalent diameter d is the diameter of a coolant channel with a circular cross-sectional shape equivalent to a coolant channel with a non-circular cross-sectional shape.

As can be seen from the above formula representing the pressure loss ΔP, the pressure loss increases in a narrow coolant channel or a long coolant channel.

In addition, when the refrigerant flows in a gas-liquid two-phase state, the liquid and the gas are mixed to create a complicated state, resulting in an increase in pressure loss. On the other hand, in the case of a form such as the first expansion device 5, in which the pressure is reduced at once by passing through a locally narrow flow section, basically the capacity coefficient Cv value unique to the shape of the first expansion device 5 is In the given form, the pressure loss ΔP is expressed. For example, when the inlet of the first expansion device 5 is in a gas-liquid two-phase state, the following is shown.

Here, ΔP: pressure loss [Pa], ρ: working fluid density [kg/m ³ ], ρ _water : density of water [kg/m ³ ] (fixed value), Q: volumetric flow rate [m ³ /min] , Cv: capacitance coefficient [-]. Strictly speaking, the pressure loss ΔP also takes other influences into account, but generally according to the above formula, the refrigerant flow path in which the first expansion device 5 is installed and the bypass circuit 95 in which the second heat exchange section 12 is installed is determined.

FIG. 3 is an explanatory diagram showing a cross-sectional structure of the first heat exchange section 11 and the second heat exchange section 12 of the first heat exchanger 10 according to the first embodiment. A part of the cross-sectional structure of the first heat exchanger 10 in a cross section passing through points A1, A2, A3, and A4 shown in FIG. 2 is shown. A cross section passing through points A1, A2, A3, and A4 is a cross section parallel to the xz plane. 3 shows a state viewed from the direction of arrow Y1 shown in FIG. That is, FIG. 3 shows a cross section perpendicular to the tube axis of the heat transfer tube 20 . As shown in FIG. 3, the first heat exchanger 10 is formed by inserting heat transfer tubes 20 into each of a plurality of cutouts 31 of fins 30 extending longitudinally in the z-direction. . The heat transfer tube 20 has a flat cross-sectional shape, and the long axis of the cross-sectional shape is directed in the x direction and the short axis is directed in the z direction. Air flows into the first heat exchanger 10 in the x direction, passes between the fins 30 and the heat transfer tubes 20 , and heat exchange is performed between the air and the refrigerant flowing through the heat transfer tubes 20 .

FIG. 4 is an explanatory diagram of the structure of the first heat exchanger 10 according to Embodiment 1 as viewed from the front. As shown in FIG. 4, the airflow flowing into the first heat exchanger 10 during the heating operation flows from the front to the back of the drawing. The first heat exchanger 10 is configured by arranging a plurality of heat transfer tubes 20 in parallel in the z direction with the tube axis directed in the y direction. The plurality of heat transfer tubes 20 are composed of flat tubes, for example. The plurality of flat tubes are configured in a flat shape having a major axis and a minor axis in a cross section perpendicular to the tube axis. The plurality of flattened tubes have their long axes oriented in the x-direction.

FIG. 5 shows a cross-sectional view of a flat tube that is an example of the heat transfer tube 20 used in the first heat exchanger 10 of the first embodiment. The flattened tube is made of a metallic material with thermal conductivity. For example, aluminum, an aluminum alloy, copper, or a copper alloy is used as a material for forming the flat tube. A flattened tube is manufactured by an extrusion process in which heated material is extruded through a die hole to form the internal channel 21 shown in FIG. It should be noted that the flattened tube may be manufactured by a drawing process in which material is drawn out of a die hole to form the cross section shown in FIG. A method for manufacturing the heat transfer tube 20 can be appropriately selected according to the cross-sectional shape of the heat transfer tube 20 . Note that the heat transfer tube 20 is not limited to a flat tube, and may be a heat transfer tube having a circular or elliptical cross-sectional shape, for example.

(Refrigeration cycle device 1100 of comparative example)
FIG. 6 is a circuit diagram of refrigerant circuit 101 of refrigeration cycle device 1100 that is a comparative example of refrigeration cycle device 100 of Embodiment 1. As shown in FIG. FIG. 7 is a perspective view of first heat exchanger 110 of refrigeration cycle apparatus 1100 according to a comparative example. FIG. 7 schematically shows part of the refrigerant pipes connected to the first heat exchanger 110 . The refrigerating cycle device 100 according to Embodiment 1 and the refrigerating cycle device 1100 of the comparative example differ in the refrigerant circuit configuration on the downstream side of the second heat exchanger 3 in the refrigerant flow direction during heating operation.

As shown in FIG. 1, in the refrigeration cycle apparatus 100 according to Embodiment 1, the refrigerant pipe branches downstream of the second heat exchanger 3, and the first expansion device 5 and the second heat exchange section 12 are connected in parallel. , and flows into the first heat exchange section 11 after the refrigerant passes through them and merges.

On the other hand, as shown in FIG. 6, in a refrigeration cycle device 1100 according to the comparative example, the first expansion device 5 and the second heat exchange section 112 are connected in series downstream of the second heat exchanger 3, and the refrigerant flows into the first heat exchange section 111 after passing through the first expansion device 5 and the second heat exchange section 112 in order. Note that, as shown in FIG. 7, the number of refrigerant flow paths in the first heat exchange section 111 and the number of refrigerant flow paths in the second heat exchange section 112 of the comparative example are the same as those of the first heat exchanger according to the first embodiment. 10 is set in the same way.

FIG. 8 is a diagram showing characteristics during heating operation of the refrigeration cycle device 1100 of the comparative example. FIG. 8 is a Ph diagram showing changes in the refrigerant pressure and enthalpy when the refrigeration cycle device 1100 is in heating operation. In the refrigeration cycle apparatus 1100 of the comparative example, the high-pressure gas refrigerant (P ₀₁ ) discharged from the compressor 2 passes through the four-way valve 7 and then flows into the second heat exchanger 3, which is an indoor heat exchanger. Note that the symbol represented by adding a suffix to “P” shown in parentheses is the symbol shown on the Ph diagram of FIG. The refrigerant is at the point enthalpy and pressure indicated by the symbols shown in parentheses.

The refrigerant that has flowed into the second heat exchanger 3 exchanges heat with room air in the second heat exchanger 3 and is cooled (condensed). At this time, the temperature of the refrigerant is higher than the temperature of the indoor air. The refrigerant is cooled by room air in the second heat exchanger 3 and becomes a high pressure liquid phase refrigerant at the outlet of the second heat exchanger 3 .

The high-pressure liquid refrigerant (P ₁₁ ) that has passed through the second heat exchanger 3 is decompressed by the first expansion device 5 . The gas-liquid two-phase refrigerant (P ₂₁ ) that has passed through the first expansion device 5 flows into the second heat exchange section 112 and is depressurized by the flow path in the heat transfer tube 20 . In the diagram shown in FIG. 8, the refrigerant (P ₂₁ ) that has passed through the first expansion device 5 is in a gas-liquid two-phase state. In some cases, it becomes a liquid single-phase refrigerant.

The gas-liquid two-phase refrigerant (P ₂₁ ) that has passed through the first expansion device 5 flows into the heat transfer tubes 20 of the second heat exchange section 112 . As shown in FIG. 7 , the second heat exchange section 112 has a refrigerant channel formed by one heat transfer tube 20 . Therefore, the gas-liquid two-phase refrigerant passing through the second heat exchange section 112 has a pressure loss ΔP according to the above formula (1). That is, the gas-liquid two-phase refrigerant passing through the second heat exchange section 112 is decompressed.

When the refrigerant is depressurized and undergoes a phase change from a liquid single-phase state to a gas-liquid two-phase state, the temperature of the refrigerant is determined according to the pressure. The temperature of the refrigerant becomes the saturation temperature at the predetermined pressure. That is, the temperature of the gas-liquid two-phase refrigerant is similarly lowered by the pressure reduction. At this time, heat exchange is performed according to the temperature of the working fluid outside the heat transfer tubes 20 . When the refrigerant temperature is higher than the extra-pipe working fluid temperature, the refrigerant is cooled (condensed) and the extra-pipe working fluid is heated. On the other hand, when the refrigerant temperature is lower than the extra-pipe working fluid temperature, the refrigerant is heated (evaporated) and the extra-pipe working fluid is cooled. In addition, in Embodiment 1, the external working fluid is outside air.

The low-pressure two-phase refrigerant (P ₃₁ ) that has passed through the first expansion device 5 and the second heat exchange section 112 flows into the first heat exchange section 111 and Heat (evaporate). The refrigerant that has flowed into the first heat exchange section 111 evaporates in the first heat exchange section 111 , and the low-pressure gas refrigerant (P ₄₁ ) passes through the four-way valve 7 and is sucked into the compressor 2 .

(Problem of the refrigeration cycle device 1100 of the comparative example)
In the first heat exchanger 110 of the refrigeration cycle apparatus 1100 of the comparative example, when the in-tube flow resistance of the heat transfer tube ₂₀ is large, the pressure loss ΔP in the second heat exchange section 112 becomes large, and the refrigerant pressure at P21 becomes low. Become. The case where the flow resistance of the heat transfer tube 20 is large means the case where the refrigerant channel formed inside the heat transfer tube 20 is thin, the refrigerant channel is long, or both. For example, if the internal flow path 21 shown in FIG. 5 is narrow, the pressure loss ΔP in the heat transfer tube 20 increases. As shown in Equation 1 above, the pressure loss ΔP increases as the equivalent diameter d of the flow path decreases and the flow path length L increases.

At this time, as shown in FIG. 8, if the opening degree of the first expansion device 5 is insufficient and the pressure loss in the second heat exchange section 112 is large, the refrigerant (P ₃₁ ) may be lower than in the ideal situation. That is, as shown in FIG. 8, the pressure of the refrigerant flowing into the first heat exchange section 111 of the first heat exchanger 110 functioning as an evaporator may become lower than the appropriate evaporator pressure P0. Such a state is likely to occur when the number of refrigerant passages in the second heat exchange portion 112 is small and the refrigerant passages inside the heat transfer tubes 20 are narrow and long.

As described above, in the case of the first heat exchanger 110 of the refrigeration cycle apparatus 1100 of the comparative example, the pressure difference between the suction portion (P ₄₁ ) and the discharge portion (P ₀₁ ) of the compressor 2 increases, However, there was a problem that the amount of work of the equipment increased and the power consumption also increased. As a result, the efficiency of the refrigeration cycle device 1100 becomes low, impairing energy saving. Alternatively, when the temperature of the refrigerant flowing in the first heat exchange section 111 decreases as the pressure decreases, and the first heat exchanger 110 used as an outdoor heat exchanger is operated at a low outdoor temperature, The amount of frost increases and the heat exchange performance may deteriorate.

On the other hand, when different heat transfer tubes 20 are used in the lower part and the upper part of the first heat exchanger 110, and the heat transfer tubes 20 having a large cross-sectional area of the flow path are used in the lower part, the first heat exchanger There was a problem that the manufacturability of 110 deteriorated.

In FIG. 8, if the pressure of the first heat exchanger 110 is to be operated at an appropriate value P0, the degree of opening of the first expansion device 5 must be further increased. Since the pressure loss ΔP in the second heat exchange section 112 depends on the shape of the heat transfer tubes 20 of the second heat exchange section 112, the pressure loss ΔP in the second heat exchange section 112 alone is between points P ₂₁ and P ₃₁ in FIG. is difficult to adjust to reduce the pressure difference between the two refrigerants. Therefore, in order to further increase the pressure of the refrigerant at point _P31 in FIG. That is, it is necessary to increase the degree of opening of the first expansion device 5 and decrease the amount of pressure reduction between points P ₁₁ and P ₂₁ in FIG. However, an electric expansion valve, a mechanical expansion valve, a capillary tube, or the like used as the first expansion device 5 has a finite adjustment range of opening, and considering the control of the refrigerating capacity of the refrigeration cycle device 1100, the first There is a problem that it is difficult to set an appropriate opening adjustment range for the expansion device 5 . In other words, when the flow resistance of the lower portion of the first heat exchanger 110 increases, the necessary refrigerant flow rate may not be adjusted even when the first expansion device 5 is at its maximum opening, and the controllability of the refrigeration cycle device 1100 deteriorates. There was a problem of

(Action of refrigeration cycle device 100 according to Embodiment 1)
FIG. 9 is a diagram showing the characteristics of the refrigeration cycle apparatus 100 according to Embodiment 1 during heating operation. 10 is an enlarged view of part A in FIG. 9. FIG. FIG. 9 is a Ph diagram showing changes in the refrigerant pressure and enthalpy when the refrigeration cycle apparatus 100 is in heating operation. In the refrigeration cycle apparatus 100, the high-pressure gas refrigerant ( _P01 ) discharged from the compressor 2 passes through the four-way valve 7 and flows into the second heat exchanger 3, which is an indoor heat exchanger. The refrigerant exchanges heat with the indoor air and cools (condenses). At this time, the temperature of the refrigerant is higher than that of the indoor air. The refrigerant is cooled by room air in the second heat exchanger 3 and becomes a high pressure liquid phase refrigerant at the outlet of the second heat exchanger 3 .

The high-pressure liquid refrigerant (P ₁₁ ) that has passed through the second heat exchanger 3 is branched into two, distributed to the second heat exchange section 12 and the first expansion device 5, and expanded, that is, decompressed. The refrigerant that has flowed into the second heat exchange section 12 is depressurized by the refrigerant flow paths in the heat transfer tubes 20, similarly to the refrigerant that has flowed into the second heat exchange section 112 in the comparative example. When the pressure of the refrigerant is reduced in the heat transfer tube 20 and the phase changes from the liquid single-phase state to the gas-liquid two-phase state, the temperature of the refrigerant is determined according to the pressure. That is, the temperature also decreases as the pressure of the refrigerant decreases. At this time, heat exchange is performed between the refrigerant flowing inside the heat transfer tubes 20 and the outside air according to the temperature of the working fluid outside the heat transfer tubes 20, that is, the temperature of the outside air. If the coolant temperature is higher than the temperature of the working fluid outside the tube, the coolant will be cooled (condensed) and the working fluid outside the tube will be heated. On the other hand, when the refrigerant temperature is lower than the temperature of the working fluid outside the tube, the refrigerant is heated (evaporated) and the working fluid outside the tube is cooled. As a result, the refrigerant flowing through the second heat exchange section 12 becomes a low-pressure gas-liquid two-phase refrigerant (P ₂₂ ).

The refrigerant that has flowed into the first expansion device 5 is expanded (depressurized) to become a low-pressure gas-liquid two-phase refrigerant (P ₂₁ ). At this time, since the first expansion device 5 performs adiabatic expansion without heat exchange of the refrigerant, the enthalpy value of the gas-liquid two-phase refrigerant (P ₂₁ ) is the same as the state before expansion (P ₁₁ ). be.

Here, the ratio of the refrigerant circulation amount distributed to the second heat exchange section 12 and the first expansion device 5 is determined by the magnitude of the flow resistance in the heat transfer tube 20 of the second heat exchange section 12 and the first expansion It is uniformly determined by the difference from the magnitude of the flow resistance due to the expansion restriction of the device 5 .

The pressure loss ΔP of the heat transfer tube 20 is obtained by the above formula (1). Of the equation (1), the friction loss coefficient λ, the channel length L, and the equivalent diameter d of the channel are determined by the shape of the heat transfer tubes 20 and the number of heat transfer tubes 20 included in the second heat exchange section 12. be. On the other hand, in formula (1), the mass velocity G is determined by the amount of refrigerant flowing into the second heat exchange section 12, and the working fluid density ρ varies depending on whether the refrigerant is single-phase or gas-liquid two-phase. It is something to do. On the other hand, the pressure loss ΔP of the first expansion device 5 is determined by Equation (2). When the opening is small (when Cv is small), the flow rate is small and the pressure loss ΔP is large. Also, when the opening is large (when Cv is large), the flow rate is large and the pressure loss ΔP is small.

Therefore, in the refrigerant circuit 1, the decompression of the refrigerant in the section where the second heat exchange section 12 and the first expansion device 5 are connected in parallel, that is, the decompression of the refrigerant in the section from _P11 to _P31 is 1 can be controlled by the opening degree of the expansion device 5 .

The low-pressure gas-liquid two-phase refrigerant (P ₂₂ ) that has passed through the second heat exchange section 12 and the low-pressure gas-liquid two-phase refrigerant (P ₂₁ ) that has passed through the first expansion device 5 join together to form a refrigerant It becomes a low-pressure two-phase refrigerant (P ₃₁ ) according to the circulating amount ratio and each enthalpy, flows into the first heat exchange section 11, and is heated (evaporated). The low-pressure gas refrigerant (P ₄₁ ) evaporated in the first heat exchange section 11 passes through the four-way valve 7 and is sucked into the compressor 2 .

(Effect of Embodiment 1)
In the refrigeration cycle apparatus 100 according to Embodiment 1, even when the in-tube flow resistance of the heat transfer tubes 20 of the second heat exchange section 12 is large, the refrigerant flow path in parallel with the refrigerant flow path in which the first expansion device 5 is installed is provided. A bypass circuit 95 is formed in the . Therefore, compared to the case where the second heat exchange section 12 or the first expansion device 5 is installed independently in series, the flow resistance of the refrigerant flow path in the portion where the refrigerant circuits 1 are arranged in parallel is reduced. Therefore, there is no need to increase the opening degree of the first expansion device 5, and the opening degree of the first expansion device 5 is not insufficient. In addition, the liquid refrigerant having a high pressure and a temperature higher than that of the room air can be caused to flow into the second heat exchange section 12 including the lowest stage of the first heat exchanger 10 . Therefore, it is possible to prevent the drain water remaining in the lower portion of the first heat exchanger 10 from freezing.

A refrigeration cycle apparatus 100 according to Embodiment 1 includes a refrigerant circuit 1 in which a compressor 2, a first heat exchanger 10, and a first expansion device 5 are connected by refrigerant piping. The first heat exchanger 10 includes a first heat exchange section 11 and a second heat exchange section 12 connected in series to the first heat exchange section 11 in the refrigerant circuit 1 . The first expansion device 5 is connected in parallel with the second heat exchange section 12 in the refrigerant circuit 1 , and the second heat exchange section 12 is positioned below the first heat exchange section 11 .
When the first heat exchanger 10 functions as an evaporator, the refrigerant flowing out of the second heat exchanger 3 is first distributed to the first expansion device 5 and the second heat exchange section 12 . Therefore, in the second heat exchange section 12 , the refrigerant flows within a saturation temperature range corresponding to the pressure difference between the upstream side and the downstream side of the first expansion device 5 in the conventional refrigerant circuit 101 . That is, the second heat exchange section 12 according to Embodiment 1 is used as an evaporator because the temperature of the refrigerant is higher than that at the inlet of the first heat exchanger 110 used as the evaporator of the refrigerant circuit 101 of the comparative example. It is possible to suppress freezing of the residual water at the bottom of the first heat exchanger 10 .

Also, the second heat exchange section 12 serves as a bypass circuit 95 with respect to the first expansion device 5 . By adding the second heat exchange section 12 in parallel with the first expansion device 5, compared to the refrigerant circuit 101 in which the first expansion device 5 and the second heat exchange section 12 are connected in series as in the comparative example, The maximum opening degree of the first expansion device 5 can be reduced. Therefore, when the pressure loss ΔP of the refrigerant passing through the second heat exchange section 12 is large, the opening of the first expansion device 5 is unlikely to be insufficient, and the range in which the pressure of the refrigerant in the evaporator can be controlled is widened.

In particular, when a flat tube is used as the heat transfer tube 20 of the first heat exchanger 10, the refrigerant flow path is narrow, and pressure loss may increase when the refrigerant is circulated. In order to reduce the amount of refrigerant in the first heat exchanger 10 and the refrigerant circuit 1, the heat transfer tube 20 is preferably formed with a thin refrigerant flow path. It is desirable to adopt a flat tube of 0.8 mm or less. At this time, when it is desired to increase the refrigerant pressure of the first heat exchanger 10 functioning as an evaporator, that is, when it is desired to operate in a state where the heat exchange capacity of the evaporator is low, in the refrigerant circuit 101 of the comparative example, the first heat The pressure loss ΔP in the second heat exchange section 112 located in the lower part of the exchanger 10 is high. Therefore, there is a problem that the pressure in the first heat exchange section 111 becomes lower than the appropriate evaporator pressure P0 unless the opening degree of the first expansion device 5 is increased. On the other hand, in the refrigerant circuit 1 of the refrigeration cycle apparatus 100 according to Embodiment 1, the second heat exchange section 12 having a large pressure loss and the first expansion device 5 are arranged in parallel. The pressure in the evaporator can be properly controlled without widening the opening range of the valve.

In addition, since the first heat exchange section 11 and the second heat exchange section 12 of the first heat exchanger 10 are configured integrally, there is an advantage that the assembling efficiency is improved when manufacturing the first heat exchanger 10. be.

In the refrigeration cycle apparatus 100 according to Embodiment 1, the number of refrigerant flow paths in the first heat exchange section 11 is greater than the number of refrigerant flow paths in the second heat exchange section 12 . Since the first heat exchanger 10 is composed of two elements, the first heat exchange section 11 and the second heat exchange section 12, and the first heat exchange section 11 and the second heat exchange section 12 are connected in series, , the pressure loss ΔP of the first heat exchanger 10 can be increased. Especially when used as an evaporator, the number of refrigerant path branches in the second heat exchange section 12 on the upstream side of the refrigerant flow with respect to the first heat exchange section 11 is made smaller than the number of refrigerant path branches in the first heat exchange section 11. Thus, the pressure loss ΔP in the second heat exchange section 12 can be increased. Therefore, while suppressing freezing of the accumulated water at the lowest part of the first heat exchanger 10, the refrigerant flowing into the first heat exchange section 11 can be Pressure can be lowered.

In the refrigeration cycle apparatus 100 according to Embodiment 1, the heat transfer tubes 20 provided in the first heat exchange section 11 are arranged in parallel with the heat transfer tubes 20 provided in the second heat exchange section 12 . As a result, in the first heat exchanger 10, high-temperature refrigerant flows to the lower heat transfer tubes 20 where water droplets flowing down from the upper heat transfer tubes 20 tend to stay. Therefore, it is possible to suppress freezing of the retained water accumulated on the upper surface of the heat transfer tube 20 .

In refrigeration cycle apparatus 100 according to Embodiment 1, heat transfer tube 20 is a flat tube. Since the heat transfer tubes 20 of the second heat exchange section 12 positioned below the first heat exchanger 10 are flat tubes, the pressure of the refrigerant passing through the second heat exchange section 12 is likely to decrease. Therefore, while the pressure of the refrigerant is reduced by the second heat exchange section 12 arranged in the bypass circuit 95 that does not pass through the first expansion device 5, the high-temperature refrigerant flows through the lower portion of the first heat exchanger 10. Freezing of the lower portion of the first heat exchanger 10 can be suppressed. Further, since the heat transfer tubes 20 are flat tubes, the refrigerant capacity of the first heat exchanger 10 can be reduced while maintaining or improving the heat exchange capacity, and the amount of refrigerant flowing through the refrigerant circuit 1 can be reduced.

Embodiment 2.
A refrigerating cycle device 100 according to the second embodiment is obtained by adding an expansion device to the refrigerant circuit 1 of the refrigerating cycle device 100 according to the first embodiment. Regarding the refrigeration cycle apparatus 200 according to the second embodiment, the description will focus on the changes from the first embodiment. Regarding each part of the refrigeration cycle apparatus 200 according to the second embodiment, those having the same function in each drawing are denoted by the same reference numerals as those used in the description of the first embodiment.

FIG. 11 is a circuit diagram of refrigerant circuit 201 of refrigeration cycle apparatus 200 according to Embodiment 2. As shown in FIG. 12 is a perspective view of first heat exchanger 210 of refrigeration cycle apparatus 200 according to Embodiment 2. FIG. The refrigerant circuit 201 of the refrigeration cycle device 200 according to Embodiment 2 is between the second heat exchange section 12 and the first heat exchange section 11 of the first heat exchanger 10 of the refrigeration cycle device 100 according to Embodiment 1. , a second expansion device 51 is added. The second expansion device 51 is arranged at the second expansion device 51 rather than the confluence portion 91 where the flow path in which the first expansion device 5 is arranged and the flow path in which the second heat exchange section 12 is arranged, which are branched at the branching portion 90 . It is arranged on the heat exchange part 12 side. In other words, the bypass circuit 295 in which the second heat exchange section 12 and the second expansion device 51 are connected in series is connected in parallel with the first expansion device 5 .

FIG. 13 is a diagram showing the characteristics of the refrigeration cycle device 200 according to Embodiment 2 during heating operation. FIG. 13 is a Ph diagram showing changes in pressure and enthalpy around the low-temperature and low-pressure region of the refrigeration cycle apparatus 200. As shown in FIG. Depending on the specifications of the second heat exchange section 12, the refrigeration cycle apparatus 100 of Embodiment 1 has a small pressure loss ΔP in the second heat exchange section 12, and the pressure of the refrigerant immediately after leaving the second heat exchange section 12 is can be high. _In other words, as at point P23 in FIG. 13, the temperature of the refrigerant that has exited the second heat exchange section 12 may be higher than that of the outdoor air. Therefore, the refrigerant exiting the second heat exchange section 12 is further decompressed by the second expansion device 51 to lower the pressure of the refrigerant below the pressure corresponding to the outdoor air temperature. By configuring in this way, the refrigeration cycle apparatus 200 can appropriately set or control the pressure of the first heat exchanger 210 used as an evaporator. At this time, since the temperature of the refrigerant flowing out of the second heat exchange section 12 is higher than the outdoor air temperature, even in a low outdoor air temperature environment where the outdoor air temperature is near the freezing point of water, the second heat Since high-temperature refrigerant flows through the exchange portion 12, frost formation and freezing can be suppressed.

FIG. 14 is a diagram showing the characteristics of the refrigeration cycle apparatus 200 according to Embodiment 2 during heating operation. FIG. 14 is a Ph diagram showing changes in pressure and enthalpy around the low temperature and low pressure region of the refrigeration cycle apparatus 200. As shown in FIG. FIG. 14 is a diagram when the pressure loss ΔP in the second heat exchange section 12 is larger than in the case of FIG. 13 . At this time, the temperature of the refrigerant that has flowed out of the second heat exchange section 12 is lower than that of the outdoor air. Therefore, since the temperature of the portion immediately before flowing out of the second heat exchange section 12 is lower than that of the outdoor air, frost is formed around the outlet of the heat transfer tube 20 of the second heat exchange section 12, and the remaining water freezes. It is conceivable that the However, since the refrigeration _cycle apparatus 200 according to Embodiment 2 includes the second expansion device 51, the second The degree of opening of the expansion device 51 can be set or controlled. Thereby, it is possible to suppress frost formation and freezing only in a part of the periphery of the outlet of the second heat exchange section 12 .

In addition, the first expansion device 5 and the second expansion device 51 are not limited to those whose opening degrees can be changed, and may be those whose opening degrees are fixed. Further, at least one of the first expansion device 5 and the second expansion device 51 may be configured such that the degree of opening thereof can be changed.

According to refrigeration cycle apparatus 200 according to Embodiment 2, second expansion device 51 is connected in parallel with first expansion device 5 in refrigerant circuit 201 and is connected in series with second heat exchange section 12 .

Since the refrigerant that has passed through the second heat exchange section 12 is decompressed by the second expansion device 51, the refrigerant pressure and the refrigerant temperature are increased on the upstream side of the second expansion device 51, that is, on the outlet side of the second heat exchange section 12. Rise. Therefore, the refrigerant temperature can be kept high throughout the second heat exchange section 12 . Therefore, the first heat exchanger 210 is easier to suppress freezing of water remaining in the lower portion of the first heat exchanger 210 than the first heat exchanger 10 according to the first embodiment.

In addition, for example, when the refrigerating cycle device 200 operates at a low load capacity, it is necessary to operate with the opening of the first expansion device 5 closed in an operating state in which the refrigerant circulation rate needs to be reduced. However, when the flow path resistance of the second heat exchange section 12 is small, the amount of refrigerant flowing to the second heat exchange section 12 increases. Alternatively, the resolution of the opening degree setting of the first expansion device 5 is insufficient, and the pressure of the refrigerant flowing into the first heat exchange section 11 cannot be set appropriately, and the refrigeration cycle device 200 is set to the target low load capacity. Or it may become uncontrollable. The case where the flow path resistance of the second heat exchange section 12 is small is, for example, the case where the pressure loss ΔP in the heat transfer tube 20 of the second heat exchange section 12 is small.

In the refrigeration cycle apparatus 200 according to Embodiment 2, by including the bypass circuit 295 in which the second heat exchange section 12 and the second expansion device 51 are connected in series, the bypass circuit on the side of the second heat exchange section 12 295 can also be added with flow path resistance. In other words, the pressure of the refrigerant flowing into the first heat exchange section 11 can be controlled using not only the first expansion device 5 but also the second expansion device 51 installed in the bypass circuit 295 . Therefore, the refrigerating cycle device 200 improves the pressure control performance of the first heat exchanger 10 functioning as an evaporator when operating in the low load capacity state, compared to the refrigerating cycle device 100 according to Embodiment 1. can be done.

Embodiment 3.
A refrigerating cycle device 300 according to the third embodiment is obtained by adding an expansion device to the refrigerant circuit 1 of the refrigerating cycle device 100 according to the first embodiment. Regarding the refrigeration cycle apparatus 300 according to the third embodiment, the description will focus on the changes from the first embodiment. Regarding each part of the refrigeration cycle apparatus 300 according to Embodiment 3, those having the same function in each drawing are denoted by the same reference numerals as those used in the description of Embodiment 1. FIG.

FIG. 15 is a circuit diagram of refrigerant circuit 301 of refrigeration cycle apparatus 300 according to Embodiment 3. As shown in FIG. 16 is a perspective view of first heat exchanger 310 of refrigeration cycle apparatus 300 according to Embodiment 3. FIG. The refrigerant circuit 301 of the refrigeration cycle device 300 according to Embodiment 3 is between the second heat exchange section 12 and the first heat exchange section 11 of the first heat exchanger 10 of the refrigeration cycle device 100 according to Embodiment 1. , a second expansion device 52 is added. The second expansion device 52 is arranged at a branching portion 90 in the first direction rather than the confluence portion 91 where the flow path in which the first expansion device 5 is arranged and the flow path in which the second heat exchange section 12 is arranged join. It is arranged on the heat exchange part 11 side. In other words, the second expansion device 52 is connected in series with the first expansion device 5 and the second heat exchange section 12 .

FIG. 17 is a diagram showing the characteristics of the refrigeration cycle device 300 according to Embodiment 3 during heating operation. FIG. 17 is a Ph diagram showing changes in pressure and enthalpy around the low-temperature and low-pressure region of the refrigeration cycle apparatus 300. As shown in FIG. Depending on the specifications of the second heat exchange section 12, the refrigeration cycle apparatus 100 of Embodiment 1 has a small pressure loss ΔP in the second heat exchange section 12, and the pressure of the refrigerant immediately after leaving the second heat exchange section 12 is can be high. _In other words, as at point P22 in FIG. 17, the temperature of the refrigerant that has exited the second heat exchange section 12 may be higher than that of the outdoor air.

_In addition, it is conceivable that the pressure of the refrigerant flowing out of the first expansion device 5, that is, the pressure of the refrigerant at the point P21 cannot be sufficiently lowered due to the capacity or opening resolution of the first expansion device 5. . Therefore, the refrigerant that has exited the second heat exchange section 12 and the first expansion device 5 and joined is further decompressed by the second expansion device 52 to lower the pressure of the refrigerant below the pressure corresponding to the temperature of the outdoor air. With this configuration, the refrigeration cycle apparatus 300 according to Embodiment 3 can appropriately set or control the pressure of the first heat exchanger 310 used as an evaporator.

In the characteristics of the refrigeration cycle device 300 during the heating operation shown in FIG. Coolant temperature can be maintained. Therefore, there is an advantage that freezing of water remaining in the lowermost portion of the first heat exchanger 10 can be easily suppressed, as in the case of the first heat exchanger 210 according to the second embodiment.

FIG. 18 is a diagram showing the characteristics of the refrigeration cycle device 300 according to Embodiment 3 during heating operation. FIG. 18 is a Ph diagram showing changes in pressure and enthalpy around the low temperature and low pressure region of the refrigeration cycle apparatus 200. As shown in FIG. FIG. 18 is a diagram when the pressure loss ΔP in the second heat exchange section 12 is larger than in the case of FIG. 17 . At this time, the temperature of the refrigerant that has flowed out of the second heat exchange section 12 is lower than that of the outdoor air. Therefore, since the temperature of the portion immediately before flowing out of the second heat exchange section 12 is lower than that of the outdoor air, frost is formed around the outlet of the heat transfer tube 20 of the second heat exchange section 12, and the remaining water freezes. It is conceivable that the However, since the refrigeration cycle apparatus 300 according to Embodiment 3 includes the second expansion device ₅₂ , the second The degree of opening of the expansion device 52 can be set or controlled. Thereby, it is possible to suppress frost formation and freezing only in a part of the periphery of the outlet of the second heat exchange section 12 .

Also in Embodiment 3, the first expansion device 5 and the second expansion device 52 are not limited to those whose opening degrees can be changed, and may be those whose opening degrees are fixed. Also, at least one of the first expansion device 5 and the second expansion device 52 may be configured such that the degree of opening thereof can be changed.

Embodiment 4.
A refrigerating cycle device 400 according to Embodiment 4 is obtained by changing the structure of the first heat exchanger 10 of the refrigerating cycle device 100 according to Embodiment 1. FIG. Regarding the refrigeration cycle apparatus 400 according to the fourth embodiment, the description will focus on the changes from the first embodiment. As for each part of the refrigeration cycle apparatus 400 according to the fourth embodiment, those having the same function in each drawing are denoted by the same reference numerals as those used in the description of the first embodiment.

FIG. 19 is a circuit diagram of refrigerant circuit 401 of refrigeration cycle device 400 according to Embodiment 4. As shown in FIG. FIG. 20 is a perspective view of first heat exchanger 410 of refrigeration cycle apparatus 400 according to Embodiment 4. FIG. A refrigerant circuit 401 of a refrigeration cycle device 400 according to Embodiment 4 is obtained by dividing the first heat exchange section 11 of the first heat exchanger 10 of the refrigeration cycle device 100 according to Embodiment 1. FIG. In the first heat exchange section 11 according to Embodiment 1, all of the plurality of heat transfer tubes 20 are arranged in parallel, and the refrigerant flows into all of the plurality of heat transfer tubes 20 at the same time. On the other hand, the first heat exchange section 11 according to Embodiment 4 includes a plurality of heat transfer tubes 20 positioned in the lower portion 16 of the first heat exchange section 11 and a plurality of heat transfer tubes positioned in the upper portion 15 of the first heat exchange section 11. 20 are connected in series.

FIG. 21 is a diagram showing the characteristics of the refrigeration cycle device 400 according to Embodiment 4 during heating operation. FIG. 21 is a Ph diagram showing changes in pressure and enthalpy around the low-temperature and low-pressure region of the refrigeration cycle apparatus 400. As shown in FIG. Depending on the specifications of the second heat exchange section 12, the refrigeration cycle apparatus 100 of Embodiment 1 has a small pressure loss ΔP in the second heat exchange section 12, and the pressure of the refrigerant immediately after leaving the second heat exchange section 12 is can be high. That is, the temperature of the refrigerant that has exited the second heat exchange section 12 may be higher than that of the outdoor air, as at point _P22 in FIG.

Further, it may be possible that the pressure of the refrigerant at the point _P21 cannot be lowered sufficiently due to the capacity of the first expansion device 5 or the resolution of the opening degree. Therefore, it is necessary to further reduce the pressure of the refrigerant that has exited the second heat exchange section 12 and the first expansion device 5 and joined together at the lower portion 16 of the first heat exchange section 11 to lower the pressure of the refrigerant below the pressure corresponding to the outdoor air temperature. By configuring in this way, the refrigeration cycle device 400 can appropriately set or control the pressure of the first heat exchanger 410 used as an evaporator.

By configuring in this way, when the outside air temperature around the first heat exchanger 410 used as an evaporator is near the freezing point of water or below the freezing point of water, not only the second heat exchange section 12 but also High-temperature refrigerant can be supplied to the lower portion 16 of the first heat exchange section 11 as well.

Although the present invention has been described above based on the embodiments, the present invention is not limited only to the configurations of the above-described embodiments. For example, the first heat exchangers 10, 210, and 310 according to Embodiments 1 to 3 have been described as being divided into two parts, the first heat exchange section 11 and the second heat exchange section 12. The heat exchange section may be divided appropriately. For example, the first heat exchange section 11 and the second heat exchange section 12 may be divided into the same number, and the divided sections may be connected in series. Furthermore, the present invention may be configured by combining each embodiment. In short, it should be noted that the gist (technical scope) of the present invention also includes various modifications, applications, and the scope of utilization made as necessary by those skilled in the art.

REFERENCE SIGNS LIST 1 refrigerant circuit 2 compressor 3 second heat exchanger 4 blower 5 first expansion device 6 blower 7 four-way valve 10 first heat exchanger 11 first heat exchange section 11a first windward side Heat exchange section 11b First leeward heat exchange section 12 Second heat exchange section 12a Second windward heat exchange section 12b Second leeward heat exchange section 13a (windward) collection pipe 13b (leeward side) ) collecting pipe, 14 header, 14a upper header, 14b lower header, 15 upper part, 16 lower part, 20 heat transfer tube, 21 internal flow path, 30 fin, 31 notch, 51 second expansion device, 52 second expansion device, 80 refrigerant pipe, 90 branching section, 91 confluence section, 95 bypass circuit, 100 refrigeration cycle device, 101 refrigerant circuit, 110 first heat exchanger, 111 first heat exchange section, 112 second heat exchange section, 200 refrigeration cycle device , 201 refrigerant circuit, 210 first heat exchanger, 295 bypass circuit, 300 refrigeration cycle device, 301 refrigerant circuit, 310 first heat exchanger, 400 refrigeration cycle device, 401 refrigerant circuit, 410 first heat exchanger, 1100 refrigeration Cycle apparatus, G mass velocity, P0 evaporator pressure, Re Reynolds number, Y1 arrow, d equivalent diameter, ΔP pressure loss, λ friction loss coefficient, ρ working fluid density.

Claims (4)

a refrigerant circuit in which a compressor, a first expansion device, and a first heat exchanger that functions as an evaporator during heating operation are connected by refrigerant piping;
The first heat exchanger is
a first heat exchange section;
a second heat exchange section connected in series to the first heat exchange section in the refrigerant circuit;
a second expansion device connected between the first heat exchange section and the second heat exchange section;
connected to the refrigerant circuit so that the refrigerant flows from the second heat exchange portion side during heating operation;
The first expansion device is
connected in parallel with the second heat exchange section in the refrigerant circuit,
The second heat exchange section is
Located below the first heat exchange section,
The second expansion device is
A refrigeration cycle device connected in parallel with the first expansion device and in series with the second heat exchange section in the refrigerant circuit. The number of refrigerant passages in the first heat exchange unit is
The refrigerating cycle device according to claim 1, wherein the number of refrigerant flow paths is greater than the number of said second heat exchanging parts. The first heat exchanger is
Equipped with multiple heat transfer tubes arranged in parallel in the vertical direction,
Each of the plurality of heat transfer tubes,
The refrigeration cycle device according to claim 1 or 2, which is a flat tube. The refrigerant circuit is
A second heat exchanger that at least partially functions as a condenser during heating operation,
4. The refrigeration cycle apparatus according to any one of claims 1 to 3, further comprising a branching portion where said refrigerant pipe branches between said second heat exchanger and said first expansion device.

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