Patent Application
20240175586
The present disclosure relates to an air-conditioning apparatus including a heat exchanger capable of serving both as a condenser and as an evaporator.
For air-conditioning apparatuses, it is known to use a heat exchanger including heat transfer tubes in the form of flat tubes with a flat cross-section to allow heat exchange between refrigerant flowing inside the flat tubes and fluid present outside the flat tubes. For example, Patent Literature 1 discloses a heat exchanger that serves as a condenser for an air-conditioning apparatus. In the heat exchanger, opposite ends of a plurality of flat tubes are connected to a pair of headers extending in the horizontal direction. The interior of each header is divided by a partition plate into parts such that refrigerant flows through the flat tubes in a meandering manner.
Patent Literature 1 proposes sequentially reducing the number of flat tubes from the inlet to the outlet so that the heat exchanger has a smaller channel cross-sectional area in a downstream portion of the heat exchanger with respect to the refrigerant flow than in an upstream portion with respect to the refrigerant flow. This helps to enhance the flow velocity of refrigerant in the downstream portion to mitigate a decrease in heat transfer coefficient, and consequently maintain high heat exchange performance.
When an air-conditioning apparatus capable of switching between cooling and heating operations switches from one operation to another, a heat exchanger serving as a condenser switches to serving also as an evaporator. A heat exchanger employing flat tubes as disclosed in Patent Literature 1 is suited for reducing the amount of refrigerant, that is, suited for so-called refrigerant saving. When the heat exchanger disclosed in Patent Literature 1 serves as an evaporator, however, the channel cross-sectional area is smaller in a portion of the heat exchanger where refrigerant enters than in a portion of the heat exchanger where refrigerant exits. This may result in increased refrigerant pressure loss across the entire channel length. Increased refrigerant pressure loss leads to decreased saturation temperature of refrigerant, and consequently decreased air-conditioning performance.
It is accordingly an object of the present disclosure to provide an air-conditioning apparatus including a heat exchanger capable of achieving both refrigerant saving and improved performance.
An air-conditioning apparatus according to an embodiment of the present disclosure is an air-conditioning apparatus in which a compressor, a condenser, a pressure reducing device, and an evaporator are connected by a pipe and in which refrigerant circulates.
The air-conditioning apparatus includes a heat exchanger, and a fan. The heat exchanger is configured to, in response to switching of directions of refrigerant flow, switch between serving as the evaporator and serving as the condenser. The fan is configured to generate an air flow to send air to the heat exchanger.
The heat exchanger includes a first heat exchanger, a second heat exchanger, and a connection pipe.
The first heat exchanger includes a plurality of first heat transfer tubes, a first header, and a second header. The first header extends in a horizontal direction, and has an internal space divided into a plurality of chambers including a first chamber and a second chamber. The first header is connected with one end of each of the plurality of first heat transfer tubes. The second header extends in the horizontal direction, and is connected with an other end of each of the plurality of first heat transfer tubes.
The second heat exchanger includes a plurality of second heat transfer tubes, a third header, and a fourth header. The third header extends in the horizontal direction, and is connected with one end of each of the plurality of second heat transfer tubes. The fourth header extends in the horizontal direction, and is connected with an other end of each of the plurality of second heat transfer tubes.
The connection pipe connects one of the first header and the second header of the first heat exchanger, and the third header of the second heat exchanger.
For an operation in which the heat exchanger is made to serve as the evaporator:
For an operation in which the heat exchanger is made to serve as the condenser, the pipe is connected such that, after refrigerant to be condensed passes through the second heat exchanger from the pipe, the refrigerant flows via the connection pipe into one of the plurality of chambers of the first header of the first heat exchanger, or into the second header, and after passing through the first heat exchanger, the refrigerant exits from the first chamber of the first header.
The plurality of first heat transfer tubes each have a length greater than a length of each of the plurality of second heat transfer tubes.
The air-conditioning apparatus according to an embodiment of the present disclosure makes it possible to achieve both enhanced performance and refrigerant saving, by enabling reduction of pressure loss during an operation in which the first heat exchanger and the second heat exchanger are each made to serve as an evaporator, and enabling reduction of refrigerant density during an operation in which the first heat exchanger and the second heat exchanger are each made to serve as a condenser.
Embodiments of an air-conditioning apparatus according to the present disclosure are described below. The particular details illustrated in the drawings are intended to be illustrative only, and not to limit the present disclosure. Elements designated by the same reference signs in the drawings represent the same or corresponding Elements throughout the specification. Further, in the drawings below, the relative sizes of various components are not necessarily drawn to scale.
The outdoor unit 201 is provided with the following components: an outdoor fan 13a, a compressor 14, a four-way valve 15, an outdoor heat exchanger 16, and an expansion device 17. The indoor unit 202 is provided with an indoor heat exchanger 10, and an indoor fan 13b. The indoor heat exchanger 10 includes a first heat exchanger 21, and a second heat exchanger 22. The indoor heat exchanger 10 is a heat exchanger that allows heat exchange between the temperature of indoor air and the temperature of refrigerant. The indoor fan 13b is a fan that generates an air flow such that indoor air is sent to the indoor heat exchanger 10. The outdoor unit 201 is an example of a heat-source-side heat exchanger. The indoor unit 202 is an example of a use-side heat exchanger.
The four-way valve 15 and the outdoor heat exchanger 16 are connected by a pipe 11a. The outdoor heat exchanger 16 and the expansion device 17 are connected by a pipe 11b. The expansion device 17, and the first heat exchanger 21 of the indoor heat exchanger 10 are connected by a pipe 11c. The expansion device 17 is a pressure reducing device that, by reducing the cross-sectional area through which refrigerant passes, causes the pressure of refrigerant to decrease after passage through the cross-sectional area relative to the pressure of refrigerant before passage through the cross-sectional area. The second heat exchanger 22 of the indoor heat exchanger 10, and the four-way valve 15 are connected by a pipe 11d.
A refrigeration cycle is formed as refrigerant flows through the compressor 14, the four-way valve 15, the outdoor heat exchanger 16, the expansion device 17, and the indoor heat exchanger 10. The four-way valve 15 is a switching valve that switches the directions of refrigerant flow discharged from the compressor 14. The four-way valve 15 switches the directions of refrigerant flow, such that refrigerant is either routed through the pipe 11a toward the outdoor heat exchanger 16 or routed through the pipe 11d toward the indoor heat exchanger 10. Switching between cooling and heating operations of the air-conditioning apparatus 200 is performed by switching of the directions of refrigerant flow by the four-way valve 15. The switching valve may be implemented not by the four-way valve 15 but instead by a combination of, for example, other valves or pipes, such as a combination of a plurality of two-way valves.
During cooling operation of the air-conditioning apparatus 200, the indoor heat exchanger 10 serves as an evaporator, and the outdoor heat exchanger 16 serves as a condenser. During heating operation, the indoor heat exchanger 10 serves as a condenser, and the outdoor heat exchanger 16 serves as an evaporator. That is, the air-conditioning apparatus 200 includes heat exchangers that, in response to reversing of the direction of refrigerant flow, switch between serving as an evaporator and serving as a condenser.
The first heat exchanger 21 includes a plurality of first heat transfer tubes 212, a plurality of first fins 211, a first header 213, and a second header 214. The second heat exchanger 22 includes a plurality of second heat transfer tubes 222, a plurality of second fins 221, a third header 223, and a fourth header 224. The first heat exchanger 21 and the second heat exchanger 22 are connected by the connection pipe 12. Each of the first heat transfer tube 212 and the second heat transfer tube 222 is a heat transfer tube in which refrigerant passes for heat exchange with ambient air present outside the heat transfer tube. The first heat transfer tube 212 and the second heat transfer tube 222 are each arranged with a spacing from an adjacent heat transfer tube such that air passes through the spacing. The first header 213, the second header 214, the third header 223, and the fourth header 224 either distribute refrigerant to, or collect refrigerant from, a plurality of heat transfer tubes such as the first heat transfer tubes 212 or the second heat transfer tubes 222. One of the first header 213 and the second header 214 of the first heat exchanger 21, or one of the third header 223 and the fourth header 224 of the second heat exchanger 22 is connected with a pipe through which refrigerant enters or exits.
The connection pipe 12 connects the first heat exchanger 21 and the second heat exchanger 22 in series with each other. That is, after refrigerant passes through one of the first heat exchanger 21 and the second heat exchanger 22, the refrigerant flows into the other heat exchanger through the connection pipe 12. When the first heat exchanger 21 and the second heat exchanger 22 each serve as an evaporator, refrigerant including a liquid phase flows into the second heat exchanger 22 after passing through the first heat exchanger 21 and the connection pipe 12. When the first heat exchanger 21 and the second heat exchanger 22 each serve as a condenser, refrigerant including a gas phase flows into the first heat exchanger 21 after passing through the second heat exchanger 22 and the connection pipe 12. With the first heat exchanger 21 and the second heat exchanger 22 each serving as an evaporator, the header to which a pipe is connected to allow entry of refrigerant including a liquid phase into the first heat exchanger 21 is the first header 213, and the header to which the connection pipe 12 is connected to allow entry of refrigerant into the second heat exchanger 22 is the third header 223. At this time, refrigerant flows into the second heat exchanger 22 from the connection pipe 12 connected to the second header 214 of the first heat exchanger 21, and refrigerant exits to the outside from the fourth header 224 of the second heat exchanger 22. The configuration to be employed in this case, however, is not limited to the configuration mentioned above. In an alternative configuration, refrigerant may flow into the second heat exchanger 22 from the connection pipe 12 connected to the first header 213 of the first heat exchanger 21, or refrigerant may exit to the outside from the third header 223 of the second heat exchanger 22.
The first heat transfer tubes 212 of the first heat exchanger 21 are flat tubes, and stacked in alternation with the first fins 211. The first fins 211 are, for example, corrugated fins. Each flat tube has, when viewed in a cross-section perpendicular to a direction in which the flat tube extends, a flattened shape elongated in one direction. Air-conditioning apparatuses in which high-pressure refrigerant flows typically employ multi-hole tubes with their internal channel divided into a plurality of parts in the longitudinal direction. Corrugated fins are pieces of sheet metal with good thermal conductivity such as aluminum formed into corrugations. The first fin 211 and the second fin 221 serve to increase the heat exchange area of the first heat exchanger 21 for improved heat exchange between each heat transfer tube and air passing around each flat tube. The first heat transfer tubes 212 are arranged in parallel in the longitudinal direction with a spacing therebetween in the lateral direction. The apexes of the corrugations of the corrugated fins are joined to surfaces of the flat tubes that face each other with the spacing therebetween.
The first header 213 and the second header 214 of the first heat exchanger 21 extend in the horizontal direction. The first header 213 is connected with one end of the first heat transfer tubes 212, and the second header 214 is connected with the other end of the first heat transfer tubes 212. The first header 213 and the second header 214 each have a tubular structure with an internal channel cross-sectional area greater than the internal channel cross-sectional area of each first heat transfer tube 212. The first heat transfer tubes 212 each extend in the up-down direction, and are disposed side by side with a horizontal spacing therebetween.
The first heat exchanger 21 and the second heat exchanger 22 are positioned such that the two heat changers are not in upstream or downstream relation to each other with respect to the flow of air sent from the indoor fan 13b or other components. In other words, the first heat exchanger 21 and the second heat exchanger 22 are positioned in offset relation to each other as viewed from the fan or from an upstream location in the path of the air to be sent. Typically, one of the first header 213 and the second header 214 is positioned proximate to one of the third header 223 and the fourth header 224, and the other one of the first header 213 and the second header 214 is positioned remote from the other one of the third header 223 and the fourth header 224.
The second heat transfer tubes 222 of the second heat exchanger 22 are flat tubes, and stacked in alternation with the second fins 221. The second fins 221 are, for example, corrugated fins. As with the first fins 211, the second fins 221 serve to increase the heat exchange area of the second heat exchanger 22. One or both of the first heat exchanger 21 and the second heat exchanger 22 may employ plate fins or other fins instead of corrugated fins.
The third header 223 and the fourth header 224 of the second heat exchanger 22 extend in the horizontal direction. The third header 223 is connected with one end of the second heat transfer tubes 222, and the fourth header 224 is connected with the other end of the second heat transfer tubes 222. The third header 223 and the fourth header 224 each have a tubular structure with an internal channel cross-sectional area greater than the internal channel cross-sectional area of each second heat transfer tube 222. The second heat exchanger 22 and the first heat exchanger 21 are substantially similar in structure, but differ in Elements such as the length of their heat transfer tubes and the internal structure of their headers. The second heat transfer tubes 222 each extend in the up-down direction, and are disposed side by side with a horizontal spacing therebetween. In
The internal space of the first header 213 is divided by partition parts 4 into a plurality of chambers including a first chamber 213a and a second chamber 213b. In the following description, each space divided off by the partition part 4 is referred to as chamber, and when reference is made individually to chambers into which each header is divided, such chambers are referred to as first chamber, second chamber, and so on. In the example illustrated in
The internal space of the third header 223 is divided by the partition part 4 into a first chamber 223a and a second chamber 223b. The fourth header 224 is divided by the partition part 4 into a first chamber 224a and a second chamber 224b. In the example mentioned above, all of the headers have an internal space divided into a plurality of chambers by the partition part 4. Alternatively, some of the headers may have an internal space defined as a single chamber without being divided. The number of chambers into which the first header 213 is divided, and the number of chambers into which the second header 214 is divided may be different. The number of chambers into which the third header 223 is divided, and the number of chambers into which the fourth header 224 is divided may be different.
The connection pipe 12 connects one of the first header 213 and the second header 214 of the first heat exchanger 21, and the third header 223 of the second heat exchanger 22. In the example illustrated in
During an operation in which the indoor heat exchanger 10 is made to serve as an evaporator (hereinafter, also “evaporator mode operation”), refrigerant to be evaporated flows from the pipe 11c into the first chamber 213a of the first header 213 of the first heat exchanger 21. The refrigerant then flows into the first chamber 214a of the second header 214 from the first heat transfer tubes 212 connected to the first chamber 213a. In the first chamber 214a, the refrigerant turns its direction of flow before leaving the second header 214. Further, the refrigerant flows into the second chamber 213b of the first header 213 from the second header 214 through the first heat transfer tubes 212 connected to the second chamber 213b of the first header 213. Of the first heat transfer tubes 212 connected to the first chamber 214a of the second header 214, those connected to the first chamber 213a of the first header 213, and those connected to the second chamber 213b of the first header 213 allow refrigerant to flow therethrough in vertically opposite directions.
The refrigerant turns its direction of flow in the second chamber 213b of the first header 213. The refrigerant then flows out of the second chamber 213b into the second chamber 214b of the second header 214. The refrigerant then turns its direction of flow in the second chamber 214b, and flows out of the second chamber 214b of the second header 214 into the third chamber 213c of the first header 213. The refrigerant then turns its direction of flow in the third chamber 213c, and flows out of the third chamber 213c of the first header 213 into the third chamber 214c of the second header 214. Subsequently, the refrigerant flows into the first chamber 223a of the third header 223 of the second heat exchanger 22 from the third chamber 213c of the first header 213 through the connection pipe 12. The refrigerant then flows into the first chamber 224a of the fourth header 224 from the second heat transfer tubes 222 connected to the first chamber 223a of the third header 223. In the first chamber 224a of the fourth header 224, the refrigerant has its direction of flow turned. The refrigerant then flows into the second chamber 223b of the third header 223. The refrigerant turns its direction of flow in the second chamber 223b, and then flows into the second chamber 224b of the fourth header 224. Subsequently, the refrigerant exits from the pipe 11d connected to the second chamber 224b of the fourth header 224. The pipe 11d is connected such that the refrigerant is sucked into the compressor 14 after passing through the second heat exchanger 22.
During an operation in which the indoor heat exchanger 10 is made to serve as a condenser (hereinafter, also “condenser mode operation”), the direction of refrigerant flow is reverse to the direction of refrigerant flow when the indoor heat exchanger 10 is made to serve as an evaporator. That is, refrigerant enters the second chamber 224b of the fourth header 224 of the second heat exchanger 22 from the pipe 11d, and exits from the first chamber 213a of the first header 213 of the first heat exchanger 21. Refrigerant to be condensed is discharged from the compressor 14, and passes through the second heat exchanger 22 from the pipe 11d. The refrigerant is then routed through the connection pipe 12 into one of the chambers of the first header 213 of the first heat exchanger 21 or into the second header 214. Although the connection pipe 12 is depicted in
As described above, refrigerant entering one heat exchanger from a chamber at one end of a header in the horizontal method is made to turn its direction of flow between a pair of headers connected by the first heat transfer tubes 212. The refrigerant thus travels in a meandering manner toward a side of the heat exchanger opposite from the inlet side in the horizontal direction. Then, after reaching the chamber at the opposite farthest end, the refrigerant flows out to the other heat exchanger through the connection pipe 12 or to the outside through the pipe 11c or 11d.
The sum of the number of chambers in the third header 223 of the second heat exchanger 22 and the number of chambers in the fourth header 224 of the second heat exchanger 22 is less than the sum of the number of chambers in the first header 213 of the first heat exchanger 21 and the number of chambers in the second header 214 of the first heat exchanger 21. Accordingly, the number of turns of the direction of refrigerant flow in the second heat exchanger 22 is less than the number of turns of the direction of refrigerant flow in the first heat exchanger 21.
The number of first heat transfer tubes 212 and the number of second heat transfer tubes 222 are the same. Each of the first heat transfer tubes 212 and each of the second heat transfer tubes 222 have the same channel cross-sectional area. The first header 213, the second header 214, the third header 223, and the fourth header 224 each have the same length. The first header 213 and the second header 214 are each made of a tube with the same thickness. Accordingly, the first header 213 and the second header 214 are basically the same in terms of the volume of their internal space, except for, for example, slight differences in Elements such as the partition part 4 and the connecting portion of each header with the corresponding pipe. Likewise, the third header 223 and the fourth header 224 are basically the same in terms of the volume of their internal space. Making the first header 213, the second header 214, the third header 223, and the fourth header 224 have basically the same volume of internal space allows for a relatively simple configuration. In an alternative arrangement, the third header 223 and the fourth header 224 of the second heat exchanger may each have an internal space greater than the internal space of each of the first header 213 and the second header 214, and to that end, the third header 223 and the fourth header 224 may each have a tube diameter greater than the tube diameter of each of the first header 213 and the second header 214.
The first heat transfer tubes 212 each have a length L1 greater than a length L2 of each of the second heat transfer tubes 222. The length L1 of the first heat transfer tube 212 refers to a length from one end of the first heat transfer tube 212 connected to the first header 213, to the other end of the first heat transfer tube 212 connected to the second header 214. The length L2 of the second heat transfer tube 222 refers to a length from one end of the second heat transfer tube 222 connected to the third header 223, to the other end of the second heat transfer tube 222 connected to the fourth header 224.
As for the number of first heat transfer tubes 212 connected to each of the first to third chambers 213a to 213c of the first header 213, the number of first heat transfer tubes 212 is not the same but different for each of the chambers (the first to third chambers 213a to 213c) of the first header 213. As for the number of first heat transfer tubes 212 connected to each of the first to third chambers 214a to 214c of the second header 214, the number of first heat transfer tubes 212 is not the same but different for each of the chambers (the first to third chambers 214a to 214c) of the second header 214. That is, the respective numbers of first heat transfer tubes 212 connected to the first to third chambers 213a to 213c of the first header 213 and to the first to third chambers 214a to 214c of the second header 214 are adjusted. This ensures that during condenser mode operation, after turning of the direction of refrigerant flow, the channel cross-sectional area for refrigerant does not decrease but remains the same or increases relative to the channel cross-sectional area before turning of the direction of refrigerant flow.
The mean number of second heat transfer tubes 222 connected to each of the chambers (the first chamber 223a and the chamber 223b) of the third header 223 is greater than the mean number of first heat transfer tubes 212 connected to each of the chambers (the first to third chambers 213a to 213c) of the first header 213.
In the present case, the first chamber 213a of the first header 213 is a chamber connected with the pipe 11c, the second chamber 224b of the fourth header 224 is a chamber connected with the pipe 11d, and the third chamber 214c of the second header 214, and the first chamber 223a of the third header 223 are chambers connected with the connection pipe 12. In each of the above-mentioned chambers, refrigerant does not turn back its direction of flow between the heat transfer tubes connected with the chamber. Accordingly, each of these chambers has a length shorter than the length of a chamber located adjacent to the chamber and where refrigerant turns back its direction of flow.
Reference is now made to how the indoor heat exchanger 10 operates.
Refrigerant changes to a high-temperature, high-pressure gaseous state in the compressor 14, and flows via the four-way valve 15 into the outdoor heat exchanger 16 mounted in the outdoor unit 201. In the outdoor heat exchanger 16, the refrigerant rejects heat to the outdoor air being sent by the outdoor fan 13a, and thus changes to liquid-phase refrigerant or mainly-liquid refrigerant. The refrigerant then undergoes pressure reduction in the expansion device 17, and flows into the first heat exchanger 21 of the indoor heat exchanger 10 of the indoor unit 202. In the first heat exchanger 21, the refrigerant removes heat from the indoor air being sent by the indoor fan 13b. As the refrigerant travels from the first heat exchanger 21 of the indoor heat exchanger 10 to the second heat exchanger 22 of the indoor heat exchanger 10, the refrigerant turns from low-temperature, low-pressure two-phase refrigerant into low-pressure gas refrigerant, which then leaves the indoor heat exchanger 10, and returns to the compressor 14 again via the four-way valve 15.
The heat-transfer-tube length ratio refers to the ratio of L1, which is the length of the first heat transfer tube 212, to L1+L2, which is the sum of the length of the first heat transfer tube 212 and the length of the second heat transfer tube 222.
As illustrated in
When the indoor heat exchanger 10 serves as an evaporator, the refrigerant that has undergone pressure reduction in the expansion device 17 removes heat from indoor air in the first heat transfer tubes 212 of the first heat exchanger 21, and increases in quality. The refrigerant with higher quality then flows through the second heat transfer tubes 222 of the second heat exchanger 22.
At this time, the volume flow rate of refrigerant through the second heat exchanger 22 is greater than the volume flow rate of refrigerant through the first heat exchanger 21. Therefore, increasing the length L2 of the second heat transfer tube 222 relative to the length L1 of the first heat transfer tube 212, that is, decreasing the heat-transfer-tube length ratio causes pressure loss in the second heat transfer tube 222 to increase. This results in decreased saturation temperature in the indoor heat exchanger 10, and consequently degradation of evaporator performance.
Decreasing the length L2 of the second heat transfer tube 222 relative to the length L1 of the first heat transfer tube 212, that is, increasing the heat-transfer-tube length ratio results in reduced length of the path through which refrigerant with higher quality passes. This leads to reduced pressure loss in the second heat transfer tube 222, increased saturation temperature in the indoor heat exchanger 10, and consequently enhanced evaporator performance.
During heating operation of the air-conditioning apparatus 200, the indoor heat exchanger 10 serves as a condenser, and the outdoor heat exchanger 16 serves as an evaporator.
Refrigerant changes to a high-temperature, high-pressure gaseous state in the compressor 14, and flows via the four-way valve 15 into the indoor heat exchanger 10 mounted in the indoor unit 202. In the first heat exchanger 21 and the second heat exchanger 22 of the indoor heat exchanger 10, the refrigerant rejects heat to the indoor air being sent by the indoor fan 13b, and thus changes to liquid-phase refrigerant or mainly-liquid refrigerant, which then leaves the indoor heat exchanger 10. Subsequently, the refrigerant undergoes pressure reduction in the expansion device 17, and in the outdoor heat exchanger 16 of the outdoor unit 201, the refrigerant removes heat from the outside air being sent by the outdoor fan 13a. The refrigerant thus changes from a low-temperature, low-pressure two-phase state to a low-pressure gaseous state. The resulting refrigerant then leaves the outdoor heat exchanger 16, and returns to the compressor 14 again via the four-way valve 15.
As illustrated in
When the indoor heat exchanger 10 serves as a condenser, refrigerant with high quality enters the indoor heat exchanger 10 from the second heat exchanger 22, and travels through the second heat exchanger 22 and the first heat exchanger 21 while rejecting heat to indoor air. This causes the refrigerant to decrease in quality, and the refrigerant with lower quality exits from the first heat exchanger 21.
At this time, low refrigerant quality in the third header 223 and the fourth header 224 of the second heat exchanger 22 results in increased mean refrigerant density in the third header 223 and the fourth header 224. This leads to an increase in the amount of refrigerant in the third header 223 and the fourth header 224, and consequently an increase in the amount of refrigerant within the indoor heat exchanger 10.
Increasing the length L1 of the first heat transfer tube 212 relative to the length L2 of the second heat transfer tube 222 helps to facilitate heat transfer in the first heat exchanger 21, which results in increased quality in the third header 223 and the fourth header 224 of the second heat exchanger 22. This leads to decreased mean refrigerant density and consequently reduced amount of refrigerant in the indoor heat exchanger 10.
In this way, the configuration described above leads to an increase in the saturation temperature in the indoor heat exchanger 10 for an operation in which the indoor heat exchanger 10 serves as an evaporator, and to a decrease in the mean refrigerant density in the indoor heat exchanger 10 for an operation in which the indoor heat exchanger 10 serves as a condenser.
This makes it possible to achieve both enhanced performance and energy saving of the air-conditioning apparatus 200.
The number of partition parts 4 that divide the internal space of each of the first header 213, the second header 214, the third header 223, and the fourth header 224, and the number of chambers into which the internal space is to be divided may be changed as appropriate. In an alternative configuration, each of the third header 223 and the fourth header 224 may include no partition part 4, and may thus include only a single chamber.
It is to be noted, however, that the sum of the number of chambers in the third header 223 of the second heat exchanger 22, and the number of chambers in the fourth header 224 of the second heat exchanger 22 is less than the sum of the number of chambers in the first header 213 of the first heat exchanger 21, and the number of chambers in the second header 214 of the first heat exchanger 21. Alternatively, the number of chambers in the first header 213 or the second header 214 of the first heat exchanger 21, which is a header connected with the connection pipe 12, is greater than the number of chambers in the third header 223 of the second heat exchanger 22, which is a header connected with the connection pipe 12. As a result, the number of turns of the direction of refrigerant flow in the second heat exchanger 22 is less than the number of turns of the direction of refrigerant flow in the first heat exchanger 21. This reduces pressure loss caused by collision or friction between refrigerant and the interior wall surface of each of the third header 223 and the fourth header 224.
During evaporator mode operation, the following relationship holds: the number of first heat transfer tubes 212 connected to a chamber of the first heat exchanger 21 that is connected to the pipe 11c and into which liquid-containing refrigerant enters<the number of first heat transfer tubes 212 connected to a chamber of the first heat exchanger 21 from which refrigerant flows out into the connection pipe 12≤the number of second heat transfer tubes 222 connected to a chamber of the second heat exchanger 22 into which refrigerant enters from the connection pipe 12≤the number of second heat transfer tubes 222 connected to a chamber of the second heat exchanger 22 that is connected to the pipe 11d and from which gasified refrigerant exits.
The protrusion of the second heat transfer tube 222 into the third header 223 and the fourth header 224 helps to ensure that even if there is an expansion or contraction of flow, pressure loss caused by the resistance to refrigerant flow can be reduced.
Unlike the first heat exchanger 21, the second heat exchanger 22 may be designed such that the channel cross-sectional area does not vary across the entire refrigerant path. The first chamber 223a of the third header 223 and the second chamber 224b of the fourth header 224, which are chambers from or into which refrigerant exits to or enters from the outside and where refrigerant does not turn back its direction of flow, may be made to have the same size. The second chamber 223b of the third header 223 and the first chamber 224a of the fourth header 224, which are chambers where refrigerant turns back its direction of flow, may be made to have the same size. Desirably, the number of second heat transfer tubes 222 connected to the first chamber 223a of the third header 223 and the number of second heat transfer tubes 222 connected to the second chamber 224b of the fourth header 224 are the same, and the number of second heat transfer tubes 222 connected to the second chamber 223b of the third header 223 and the number of second heat transfer tubes 222 connected to the first chamber 224a of the fourth header 224 are the same. That is, the number of second heat transfer tubes 222 through which refrigerant flows from one of the chambers in the third header 223 and the fourth header 224, toward a chamber in the fourth header 224 and the third header 223 opposite from the one chamber is the same between the third and the fourth headers 223 and 224. This helps to ensure that for the second heat exchanger 22 with a relatively small length of its heat transfer tubes, a large channel cross-sectional area can be maintained across the entire length of the heat transfer tubes. In some cases, dividing the number of second heat transfer tubes 222 connected to the third header 223 by the number of chambers in the third header 223 may result in a non-integer quotient. In such a case, it may be desirable to adjust the respective numbers of second heat transfer tubes 222 connected to individual chambers in the third header 223 to integers by adding or subtracting a number less than 1 to or from the quotient, and to make the difference between the numbers of second heat transfer tubes 222 less than or equal to 1. This results in roughly the same, although not exactly the same, number of second heat transfer tubes 222 in each chamber. As a result, the effect mentioned above can be obtained. For example, if the number of second heat transfer tubes 222 connected to the third header 223 is 21, and the number of chambers in the third header 223 is 2, then the respective numbers of second heat transfer tubes 222 connected to the two chambers are 10 and 11. Although the above-mentioned adjustment may in some cases result in an about 10% change in the size of each chamber in the third header 223, even in such cases, it is regarded according to the present disclosure that such a plurality of chambers are equal in size, and these chambers are connected with the same number of second heat transfer tubes 222.
The quality of refrigerant flowing through the third header 223 and the fourth header 224 is higher than the quality of refrigerant flowing through the first header 213. Accordingly, maintaining a large channel cross-sectional area across the entire path of refrigerant flow through the second heat exchanger 22 makes it possible to reduce pressure loss in the second heat exchanger 22 when the indoor heat exchanger 10 is operating as an evaporator.
The first header 213 is divided into individual chambers (the first to third chambers 213a to 213c) such that these chambers have a mean size smaller than the mean size of the chambers (the first and second chambers 223a and 223b) in the third header 223. That is, during condenser mode operation of the indoor heat exchanger 10, the individual divided chambers (the first to third chambers 213a to 213c) in the first heat exchanger 21 located downstream in the flow of refrigerant have a mean size smaller than the mean size of the individual divided chambers (the first and second chambers 223a and 223b) in the second heat exchanger 22. As a result, in the indoor heat exchanger 10, formation of regions where refrigerant exists in a subcooled state with high refrigerant density can be reduced, and consequently, the amount of refrigerant can be reduced.
The foregoing description is directed to an example in which the indoor heat exchanger 10 includes the first heat exchanger 21 and the second heat exchanger 22. In an alternative configuration, instead of the indoor heat exchanger 10, the outdoor heat exchanger 16 may include the first heat exchanger 21 and the second heat exchanger 22.
In another alternative configuration, the indoor heat exchanger 10 may include the first heat exchanger 21 and the second heat exchanger 22, and the outdoor heat exchanger 16 may likewise include the first heat exchanger 21 and the second heat exchanger 22.
The pipe 11c, which is a pipe through which two-phase refrigerant flows when the indoor heat exchanger 10 operates as a condenser, is longer than the pipe 11b, which is a pipe through which two-phase refrigerant flows when the outdoor heat exchanger 16 operates as a condenser. Accordingly, from the viewpoint of reducing the amount of refrigerant during condenser mode operation, employing a configuration in which the indoor heat exchanger 10 is made up of the first heat exchanger 21 and the second heat exchanger 22 allows for greater reduction in the amount of refrigerant.
In the air-conditioning apparatus 200 according to Embodiment 1, the length L1 of the first heat transfer tube 212 of the first heat exchanger 21 constituting the indoor heat exchanger 10 is greater than the length L2 of the second heat transfer tube 222 of the second heat exchanger 22. Accordingly, when the indoor heat exchanger 10 is made to serve as an evaporator, refrigerant with high quality flows through the second heat transfer tube 222 of the second heat exchanger 22, which has a length less than the length L1 of the first heat transfer tube 212 of the first heat exchanger 21. This results in reduced pressure loss, and enhanced performance of the indoor heat exchanger 10. When the indoor heat exchanger 10 is made to serve as a condenser, heat exchange in the first heat exchanger 21 is facilitated, which in turn facilitates passage of refrigerant with high quality. This makes it possible to reduce mean refrigerant density in the first header 213, the second header 214, the third header 223, and the fourth header 224, and consequently achieve refrigerant saving.
The refrigerant pipe through which refrigerant with high quality flows when the indoor heat exchanger 10 serves as a condenser is longer than the refrigerant pipe through which refrigerant with high quality flows when the outdoor heat exchanger 16 serves as a condenser. Accordingly, employing a configuration in which the indoor heat exchanger 10 includes the first heat exchanger 21 and the second heat exchanger 22 allows for increased energy saving.
As described above, the number of chambers (the first to third chambers 213a to 213c) in the first header 213 is greater than the number of chambers (the first chamber 223a and the second chamber 223b) in the third header 223. This leads to reduced pressure loss within the third header 223 when the indoor heat exchanger 10 serves as an evaporator. This makes it possible to enhance the performance of the indoor heat exchanger 10.
Of the chambers 213a to 213c in the first header 213, the first chamber 213a, which is located downstream in the direction of refrigerant flow when the indoor heat exchanger 10 is serving as a condenser, is smaller than the second chamber 213b and the third chamber 213c, which are located upstream in the direction of refrigerant flow. This reduces the risk of refrigerant in a low-quality, subcooled state accumulating in the first header 213.
The third header 223 is divided into the first chamber 223a and the second chamber 223b that are of the same size. The division into equal-sized chambers helps to ensure that when the indoor heat exchanger 10 serves as an evaporator, a channel in which refrigerant with high quality flows can be increased in cross-sectional area, which allows for reduced pressure loss and enhanced performance.
If a refrigerant with a low gas density relative to an R32 refrigerant or an R410A refrigerant is used as the refrigerant, the refrigerant flow velocity per unit capacity increases. Accordingly, the performance improvement due to reduced pressure loss becomes more pronounced. Examples of such a refrigerant include an olefin-based refrigerant, propane, and dimethyl ether (DME) that contain double-bonds in their molecules, such as HFO1234yf and HFP1234ze(E).
The first heat exchanger 21 and the second heat exchanger 22 may be integral with each other as long as such an integral construction allows the constraints on the respective lengths of the first and second heat transfer tubes 212 and 222 to be met.
As illustrated in
In the indoor heat exchanger 10, the second header 214 and the fourth header 224 are the two headers that are located farthest from each other, and the first header 213 and the third header 223 are the two headers that are located closest to each other. As with the configuration in
Since the configuration in
As with the configuration in
The first header 213 of the first heat exchanger 21 is divided by a plurality of partition parts 4 into a plurality of chambers 213a to 213c. The second header 214 is divided by a plurality of partition parts 4 into a plurality of chambers 214a to 214c.
The third header 223 of the second heat exchanger 22 is divided into a first chamber 223a and a second chamber 223b.
The third heat exchanger 23 is a serpentine heat exchanger in which a single third heat transfer tube 6 makes a turn a plurality of times.
The third heat transfer tube 6 of the third heat exchanger 23 is connected at one end 8 to the pipe 11c, and connected at the other end 7 to the first chamber 213a of the first header 213.
A length L3 from the location of a turn in the third heat transfer tube 6 to the location of the next turn is less than the length L1 of the first heat transfer tube 212 of the first heat exchanger 21. The total tube path length of the third heat transfer tube 6 is greater than the length L1 of the first heat transfer tube 212.
In the indoor heat exchanger 10 according to the second modification, when the indoor heat exchanger 10 operates as an evaporator, refrigerant enters the one end 8 of the third heat transfer tube 6 from the pipe 11c, and flows toward the other end 7 of the third heat transfer tube 6. The refrigerant then flows from the other end 7 into the first chamber 213a of the first header 213.
The refrigerant flows from the first chamber 213a of the first header 213 through the following chambers before entering the third chamber 213c of the first header 213: the first chamber 214a of the second header 214; the second chamber 213b of the first header 213; and then the second chamber 214b of the second header 214.
Subsequently, the refrigerant is routed through the third chamber 214c of the second header 214 from the third chamber 213c of the first header 213, and passes through the connection pipe 12 into the first chamber 223a of the third header 223. After then passing through the fourth header 224, the refrigerant reaches the second chamber 223b of the third header 223, and exits from the pipe 11d.
At this time, although the length L3 from the location of a turn in the third heat transfer tube 6 to the location of the next turn is less than the length L1 of the first heat transfer tube 212, the total tube path length of the third heat transfer tube 6 is greater than the length L1 of the first heat transfer tube 212. The second modification can be may be considered as a modification of the configurations illustrated in
As illustrated in
That is, in the indoor unit 202 according to Embodiment 2, a lowermost part 41 of the first heat exchanger 21 is positioned lower in the vertical direction 31 than a lowermost part 42 of the second heat exchanger 22.
As illustrated in
As the liquid-phase refrigerant 61 moves in the connection pipe 12, the liquid-phase refrigerant 61 experiences an inertial force 52, which acts in the direction of refrigerant flow, and a gravitational force 51. Within each header, the channel cross-sectional area is larger than the channel cross-sectional area in each heat transfer tube, and thus the velocity of refrigerant decreases. As a result, the inertial force 52 decreases, and the influence of the gravitational force 51 increases.
At higher refrigerant flow rates, the inertial force 52 acting on the liquid-phase refrigerant 61 is greater than the gravitational force 51 acting on the liquid-phase refrigerant 61. This allows the liquid-phase refrigerant 61 in the connection pipe 12 to flow from the second heat exchanger 22 toward the first heat exchanger 21, that is, in the refrigerant flow direction 30.
During low-capacity operation, the refrigerant flow rate decreases. As a result, the inertial force 52 decreases, and the influence of the gravitational force 51 increases.
At this time, if the first heat transfer tube 212 of the first heat exchanger 21 is shorter than the second heat transfer tube 222 of the second heat exchanger 22, the relative influence of the gravitational force 51 that acts in the direction of the second heat exchanger 22 increases. As a consequence, the influence of the gravitational force 51 acting in the direction of the second heat exchanger 22 increases relative to the inertial force 52 acting on the liquid-phase refrigerant 61 in the connection pipe 12. This makes it harder for the liquid-phase refrigerant 61 to flow in the refrigerant flow direction 30. As a result, the liquid-phase refrigerant 61 tends to stay particularly in the header where the inertial force 52 is relatively small, and in the connection pipe 12. This leads to increased refrigerant density in the second heat exchanger 22, and consequently increased amount of refrigerant.
According to Embodiment 2, the first heat transfer tube 212 of the first heat exchanger 21 is longer than the second heat transfer tube 222 of the second heat exchanger 22. Consequently, the influence of the gravitational force 51 acting in the direction of the first heat exchanger 21 is greater than the influence of the gravitational force 51 acting in the direction of the second heat exchanger 22. As a result, even when the inertial force 52 acting on the liquid-phase refrigerant 61 decreases during low-capacity operation, refrigerant can be moved in the refrigerant flow direction 30. This helps to mitigate an increase in refrigerant density during low-capacity operation, and consequently achieve refrigerant saving.
The air-conditioning apparatus 200 according to Embodiment 2 described above is designed such that in the indoor heat exchanger 10, the lowermost part 41 of the first heat exchanger 21 is positioned lower in the vertical direction 31 than the lowermost part 42 of the second heat exchanger 22. Such positioning helps to, during serving of the indoor heat exchanger 10 as a condenser, mitigate an increase in refrigerant density in the second heat exchanger 22, which occurs due to the increased difficulty with which the liquid-phase refrigerant 61 to be directed toward the first heat exchanger 21 flows in the refrigerant flow direction 30. As a result, refrigerant saving can be achieved.
As described above, the second heat transfer tube 222 is shorter than the first heat transfer tube 212. Consequently, the amount of heat exchange in the second heat exchanger 22 is small relative to when the second heat transfer tube 222 has the same length as the first heat transfer tube 212. This results in relatively high quality in the second heat exchanger 22. This ensures that even when the liquid-phase refrigerant 61 stays in the header and the connection pipe 12, the amount of such refrigerant is small. By contrast, the quality in the first heat exchanger 21 decreases, which causes part of the first header 213 and the second header 214 to have areas of slightly decreased quality. However, in making the indoor heat exchanger 10 serve as a condenser, it is common to bring refrigerant into a subcooled state in the first place, and thus the amount of refrigerant does not change at locations where only the liquid-phase refrigerant 61 flows. As a result, an overall decrease in the amount of the liquid-phase refrigerant 61 is achieved for the heat exchanger according to Embodiment 2.
In Embodiment 3, reference will be made to the relationship between the indoor heat exchanger 10 and the indoor fan 13b in the indoor unit 202 of the air-conditioning apparatus 200 according to Embodiment 1. In Embodiment 3, a fan with a rotation axis extending in the horizontal direction, such as a cross-flow fan, is employed as the indoor fan 13b. The air-conditioning apparatus 200 and the indoor heat exchanger 10 are similar in configuration to those in Embodiment 1, and thus will not be described in further detail. Elements in Embodiment 3 that are similar or corresponding to those in Embodiment 1 will be designated by the same reference signs.
In the indoor heat exchanger 10, the first heat transfer tube 212 and second heat transfer tube 222 are disposed in the circumferential direction of the rotation axis 18 and tangentially to a circle centered on the rotation axis 18 of the indoor fan 13b. Refrigerant flows in the circumferential direction of the rotation axis 18.
The first heat exchanger 21 is disposed such that the first header 213 and the second header 214 extend in a direction parallel to the direction of the rotation axis 18 of the indoor fan 13b. The second heat exchanger 22 is disposed such that the third header 223 and the fourth header 224 extend in a direction parallel to the direction of the rotation axis 18 of the indoor fan 13b.
Disposing the first heat exchanger 21 and the second heat exchanger 22 side-by-side with respect to the air flow as described above causes the static pressure of the air flow to decrease, which results in increased air flow rate. This improves heat transfer performance, and helps to reduce formation of subcooled refrigerant regions during condenser mode operation of the indoor heat exchanger 10. This in turn helps to reduce refrigerant density, and consequently achieve refrigerant saving.
If the first heat exchanger 21 and the second heat exchanger 22 are disposed as in the indoor unit 202 according to the comparative example, the flow of air through the indoor heat exchanger 10 tends to be obstructed. This is because the first header 213, the second header 214, the third header 223, and the fourth header 224 are located at different heights due to the difference in length between the first heat transfer tube 212 of the first heat exchanger 21 and the second heat transfer tube 222 of the second heat exchanger 22.
Disposing the first heat exchanger 21 and the second heat exchanger 22 side-by-side with respect to the air flow as in the indoor unit 202 according to Embodiment 3 results in decreased static pressure of the air flow and enhanced air flow rate, and consequently improved heat transfer performance. This helps to reduce formation of subcooled refrigerant regions during condenser mode operation of the indoor heat exchanger 10. Refrigerant density can be thus reduced for refrigerant saving.
As illustrated in
The above configuration leads to a reduced refrigerant saturation temperature required for blowing air at a temperature higher than or equal to a predetermined temperature during condenser mode operation. This results in enhanced performance per unit temperature of air provided to the user.
If a refrigerant flow is provided in a direction parallel to the rotation axis 18 of the indoor fan 13b, this results in large variability in air velocity in the circumferential direction of the rotation axis 18 of the indoor fan 13b. The resulting large variations in heat exchange capacity among heat transfer tubes leads to formation of regions with increased degree of refrigerant subcooling during condenser mode operation. This results in decreased refrigerant saving effect.
By contrast, according to Embodiment 3, the first heat transfer tubes 212 and second heat transfer tubes 222 are disposed in the circumferential direction of the rotation axis 18 of the indoor fan 13b and tangentially to a circle centered on the rotation axis 18. Consequently, refrigerant flows in the circumferential direction of the rotation axis 18 of the indoor fan 13b, which is a direction in which the variability in air velocity in the rotation axis direction 33 is relatively small. This configuration leads to reduced variations in heat exchange capacity among the first heat transfer tubes 212 and the second heat transfer tubes 222. During condenser mode operation, the above-mentioned configuration makes it possible to reduce the difference in the degree of subcooling and achieve refrigerant saving. During condenser mode operation and during evaporator mode operation, the above-mentioned configuration makes it possible to reduce non-uniformity of thermal load and enhance performance. It is therefore possible to achieve both refrigerant saving and enhanced performance.
The air-conditioning apparatus 200 according to Embodiment 3 described above employs a cross-flow fan as the indoor fan 13b, and includes the first heat exchanger 21 and the second heat exchanger 22 that are disposed side-by-side in the circumferential direction with respect to the rotation axis 18 of the indoor fan 13b. This results in decreased static pressure of the air flow and enhanced air flow rate, which leads to improved heat exchange in the first heat exchanger 21 and the second heat exchanger 22 and reduced formation of subcooled regions during condenser mode operation.
Now, the number of first heat transfer tubes 212 in each individual group is squared and summed for all groups to obtain a sum total, and the sum total is divided by the total number of first heat transfer tubes 212 in all groups to obtain a mean number of branches N1 in the first heat exchanger 21. This can be given by the following mathematical expression: N1=Σ(n1, k×n1, k)/Σn1, k. In the example illustrated in
Likewise, in the second heat exchanger 22, refrigerant from the connection pipe 12 passes through the following parts in the order stated below before exiting from the pipe 11d: the first chamber 223a of the third header 223; 10 second heat transfer tubes 222; the first chamber 224a of the fourth header 224; 11 second heat transfer tubes 222; and then the second chamber 223b of the third header 223. As with the first heat exchanger 21, the total number of second heat transfer tubes 222 connecting the first header 213 and the second header 214 is 21. The second heat transfer tube 222 connecting the respective chambers of opposite headers are divided into two groups of second heat transfer tubes 222 through which refrigerant flows while changing its direction as represented by the hollow arrows. The second heat transfer tubes 222 are divided into groups such that, of the second heat transfer tubes 222, a second heat transfer tube 222 and a second heat transfer tube 222 belong to the same group if a chamber of the third header 223 to which these second heat transfer tubes 222 are connected at one end, and a chamber of the fourth header 224 to which these second heat transfer tubes 222 are connected at the other end are the same between these second heat transfer tubes 222, and belong to different groups if these chambers are different between these second heat transfer tubes 222. In
Next, an investigation was made into what effect the length L1 of the first heat transfer tube of the first heat exchanger 21 and the length L2 of the second heat transfer tube of the second heat exchanger 22 have on the reduction of refrigerant, and how these lengths affect heat exchanger performance. ΔMg denotes the heat exchanger refrigerant-saving effect for condenser mode operation at 50% load for a case where the length L1 of the first heat transfer tube and the length L2 of the second heat transfer tube are equal. Gaε denotes the heat exchanger performance for evaporator operation mode at 50% load. The product of ΔMg and Gaε is defined as a figure of merit FM. A heat exchanger with a large figure of merit FM is superior from the viewpoints of the refrigerant saving effect and the figure of merit.
If the refrigerant used is changed from one kind to another, then the influence that N1 and N2 exert on the figure of merit FM changes slightly in dependence on the operating refrigerant pressure P and the amount of change in latent heat ΔH. However, the influence is small as long as the ratio between N1 and N2 remains the same. For example, it was confirmed that even if the refrigerant used is changed from R32 to R410A, or to another refrigerant with a lower gas density than these refrigerants, such as an olefin-based refrigerant, propane, or dimethyl ether, the relative change in the ratio of N2 to N1 at which the figure of merit FM peaks is small, being less than or equal to 8%. It can be therefore expected that the above-mentioned range of (L1/N1)×(N2/L2), which was observed to be effective for the refrigerant R32, is also effective in improving the figure of merit FM even if the refrigerant used is changed to a different kind of refrigerant.
Even when the flow of air that has passed through the first heat exchanger 21, and the flow of air that has passed through the second heat exchanger 22 are at different temperatures, these flows of air are mixed together by the indoor fan 13b. This leads to enhanced performance per unit temperature of air provided to an indoor space.
In Embodiment 4, reference will be made to the relationship between the indoor heat exchanger 10 and the indoor fan 13b in the indoor unit 202 of the air-conditioning apparatus 200 according to Embodiment 1. In Embodiment 4, an axial-flow fan is employed as the indoor fan 13b. The air-conditioning apparatus 200 and the indoor heat exchanger 10 are similar in configuration to those in Embodiment 1, and thus will not be described in further detail. Elements in Embodiment 4 that are similar or corresponding to those in Embodiment 1 will be designated by the same reference signs.
In the indoor heat exchanger 10, the first header 213 and the second header 214 of the first heat exchanger 21 are positioned to extend in a direction parallel to a direction orthogonal to the rotation axis 18 of the indoor fan 13b. In the second heat exchanger 22, the third header 223 and the fourth header 224 are positioned to extend in a direction parallel to a direction orthogonal to the rotation axis 18 of the indoor fan 13b. That is, the first header 213, the second header 214, the third header 223, and the fourth header 224 extend in a direction tangential to a circle centered on the rotation axis 18 of the indoor fan 13b. As seen in the direction of the rotation axis 18, the first heat exchanger 21 and the second heat exchanger 22 are disposed at locations around the rotation axis 18 that do not overlap each other. The angular range within which the first heat exchanger 21 is located around the rotation axis 18 differs from the angular range within which the second heat exchanger 22 is located around the rotation axis 18.
As illustrated in
As described above, the first heat exchanger 21 and the second heat exchanger 22 are disposed side-by-side with respect to the air flow. As compared with disposing these heat exchangers in series with respect to the air flow, the above-mentioned configuration leads to decreased static pressure of the air flow, enhanced air flow rate, and improved heat transfer. This makes it possible to, during condenser mode operation of the indoor heat exchanger 10, reduce formation of subcooled refrigerant regions, and consequently reduce refrigerant density to thereby achieve refrigerant saving.
As illustrated in
In the indoor heat exchanger 10, the first header 213, the second header 214, the third header 223, and the fourth header 224 are positioned to extend in a direction tangential to a circle centered on the rotation axis 18. The first heat transfer tube 212 of the first heat exchanger 21, and the second heat transfer tube 222 of the second heat exchanger 22 are each located at one end at the height of the straight line F, and located at the other end at the height of the lowermost part G.
Consequently, there is no difference among the first heat transfer tubes 212 in the rate of the air flow around the first heat transfer tubes 212, and likewise there is no difference among the second heat transfer tubes 222 in the rate of the air flow around the second heat transfer tubes 222. As a result, the difference in the amount of heat exchange among the first heat transfer tubes 212, and the difference in the amount of heat exchanger among the second heat transfer tubes 222 are reduced. This makes it possible to reduce formation of subcooled regions during condenser mode operation, and improve performance during condenser mode operation or evaporator mode operation. Therefore, both refrigerant saving and enhanced performance can be achieved.
Although the foregoing description is directed to a case where air flows from the air inlet 35 toward the air outlet 36, reversing the direction of flow from the air inlet 35 to the air outlet 36 does not affect the above-mentioned effect.
The air-conditioning apparatus 200 according to Embodiment 4 described above employs an axial-flow fan as the indoor fan 13b, and includes the first heat exchanger 21 and the second heat exchanger 22 that are disposed side-by-side with respect to the air flow. The above-mentioned configuration results in decreased static pressure of the air flow and enhanced air flow rate, which leads to reduced formation of subcooled regions during condenser mode operation. The above-mentioned configuration also results in reduced variations in heat exchange capacity among the first heat transfer tubes 212 and among the second heat transfer tubes 222. This makes it possible to achieve refrigerant saving during condenser mode operation, and improved performance during evaporator mode operation.
In Embodiment 5, reference will be made to the relationship between the indoor heat exchanger 10 and the indoor fan 13b in the indoor unit 202 of the air-conditioning apparatus 200 according to Embodiment 1. In Embodiment 5, a centrifugal fan including a scroll casing 5 is employed as the indoor fan 13b. The air-conditioning apparatus 200 and the indoor heat exchanger 10 are similar in configuration to those in Embodiment 1, and thus will not be described in further detail. Elements in Embodiment 5 that are similar or corresponding to those in Embodiment 1 will be designated by the same reference signs.
With regard to the indoor heat exchanger 10, the first header 213 and the second header 214 of the first heat exchanger 21 are positioned to extend in a direction parallel to the direction of the rotation axis 18 of the indoor fan 13b. In the second heat exchanger 22, the third header 223 and the fourth header 224 are positioned to extend in a direction parallel to the direction of the rotation axis 18 of the indoor fan 13b. The first heat transfer tube 212 and the second heat transfer tube 222 extend in a direction orthogonal to the rotation axis of the indoor fan 13b.
In the second heat exchanger 22, as viewed in the winding direction 32 of the casing 5, the distance from the winding start position 19 of the casing 5 to the position I is less than the distance from the winding start position 19 of the casing 5 to the position H. That is, the second heat exchanger 22 is located close to the winding start position 19 of the casing 5, and the first heat exchanger 21 is located remote from the winding start position 19 of the casing 5 as viewed in the winding direction 32 of the casing 5.
In the indoor fan 13b including the casing 5, the air flow is comparatively small near the winding start position 19 of the casing 5, and increases with increasing distance from the winding start position 19. This results in high rate of air flow through the first heat exchanger 21 during condenser mode operation of the indoor heat exchanger 10, which in turn facilitates heat transfer in the first heat exchanger 21 and reduces formation of subcooled refrigerant regions in the first heat exchanger 21. As a result, refrigerant density can be reduced to thereby achieve refrigerant saving.
During evaporator mode operation of the indoor heat exchanger 10, the refrigerant pressure in the second heat exchanger 22 is on the low-pressure side, which causes condensation water to form due to the difference between the air temperature and the refrigerant temperature. In the presence of a large air flow through the second heat exchanger 22, the condensation water is blown out to an indoor space from the surface of the second fin 221. Disposing the second heat exchanger 22 at a location near the winding start position 19 of the casing 5 and upstream with respect to the air flow reduces the inertial force that causes such condensation water to be blown out from the surface of the second fin 221. This makes it possible to increase the air flow rate without causing quality degradation of the indoor heat exchanger 10, and consequently enhance the performance of the air-conditioning apparatus 200.
In the air-conditioning apparatus 200 according to Embodiment 5 described above, the second heat exchanger 22 is disposed such that the distance from the winding start position 19 of the casing 5 to the second heat exchanger 22 is less than the distance from the winding start position 19 of the casing 5 to the first heat exchanger 21. During condenser mode operation, the above-mentioned configuration results in comparatively large air flow rate through the first heat exchanger 21, which in turn results in reduced formation of subcooled regions and reduced refrigerant density. This makes it possible to achieve refrigerant saving. During evaporator mode operation, the second heat exchanger 22 is located upstream with respect to the air flow. This helps to reduce the inertial force that causes condensation water to be blown out to an indoor space, and consequently increase the air flow rate without causing quality degradation of the indoor heat exchanger 10.
As illustrated in
When viewed in the direction of the rotation axis 18 of the indoor fan 13b, the first heat exchanger 21 and the second heat exchanger 22 are disposed at locations around the rotation axis 18 that do not overlap each other. The angular range within which the first heat exchanger 21 is located around the rotation axis 18 differs from the angular range within which the second heat exchanger 22 is located around the rotation axis 18. Accordingly, disposing the first heat exchanger 21 and the second heat exchanger 22 side-by-side with respect to the air flow as described above with reference to Embodiment 4 allows for decreased static pressure of the air flow, enhanced air flow rate, and improved heat transfer, as compared with disposing these heat exchangers in series with respect to the air flow. This makes it possible to, during condenser mode operation of the indoor heat exchanger 10, reduce formation of subcooled refrigerant regions, and consequently reduce refrigerant density to thereby achieve refrigerant saving.
As described above, the first heat exchanger 21 and the second heat exchanger 22 are disposed side-by-side with respect to the air flow. This results in decreased static pressure of the air flow and enhanced air flow rate, which leads to reduced formation of subcooled regions during condenser mode operation.
The present disclosure is applicable to an air-conditioning apparatus including a heat exchanger capable of serving both as a condenser and as an evaporator.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/012941 | 3/26/2021 | WO |
