Patent Description:
There has been known a heat exchanger constituting a refrigerant circuit of an air conditioner.

<CIT> discloses a heat exchanger including a plurality of pipes (heat transfer tubes) and a branching pipe connected to the pipes. In the heat exchanger according to <CIT>, the plurality of pipes is aligned to the windward and to the leeward of wind generated by a fan. The branching pipe includes a single inlet pipe and two branch ports, and allows a refrigerant flowing in via the inlet pipe to flow to the windward pipe and the leeward pipe via the two branch ports.

In the heat exchanger according to <CIT>, the two branch ports of the branching pipe are provided with orifices different from each other in flow path diameter, to have a difference in flow rate of an incoming refrigerant between the windward pipe and the leeward pipe. The heat exchanger according to <CIT> can accordingly suppress a difference in degree of superheating generated in the windward pipe and the leeward pipe, and inhibit deterioration in performance of the heat exchanger.

<CIT> relates to a refrigerant distribution device that is provided for distributing refrigerant to a plurality of heat transfer tubes that constitute a heat exchanger. The refrigerant distribution device includes a first distribution device dividing refrigerant into a plurality of portions, and a plurality of two-way branch pipes each dividing refrigerant divided by the first distribution device into two portions to flow into two of the plurality of heat transfer tubes. <CIT> relates to an air conditioner that uses a liquid connection pipe and a gas connection pipe to connect an outdoor unit and an indoor unit. The outdoor unit includes a heat source side heat exchanger and an outdoor blower. The heat source-side heat exchanger is formed into a fin-tube heat exchanger with three or more rows. The heat exchanger is provided with a pipe such that the flow direction of the refrigerant in the pipe is opposite to the air flow direction of the blower during a cooling operation and parallel to the air flow direction of the blower during a heating operation.

The heat exchanger disclosed in <CIT> has difficulty in production cost reduction because the orifices need to be attached to the branching pipe.

The present disclosure proposes a heat exchanger that suppresses increase in production cost as well as achieves improvement in performance.

The present invention is defined in appended claim <NUM>. The dependent claims define preferred embodiments.

A heat exchanger according to a first aspect, which is the invention as defined in appended claim <NUM>, includes a first heat transfer tube, a second heat transfer tube, and a branching tube. The branching tube has a first end connected to an end of the first heat transfer tube, a second end connected to an end of the second heat transfer tube, and a third end. The branching tube connects the first end, the second end, and the third end to each other. The first heat transfer tube is larger in heat exchange quantity than the second heat transfer tube. The branching tube includes a first flow path connecting the first end and the third end, and a second flow path connecting the second end and the third end, and the first flow path is shorter than the second flow path. The first flow path and the second flow path have a length ratio corresponding to a heat exchange quantity ratio between the first heat transfer tube and the second heat transfer tube.

In the heat exchanger according to the present invention, the first flow path is shorter than the second flow path. Accordingly, a refrigerant flowing in the first flow path receives a pressure loss smaller than a pressure loss received by a refrigerant flowing in the second flow path. The refrigerant flowing into the first heat transfer tube via the branching tube is thus larger in flow rate than the refrigerant flowing into the second heat transfer tube via the branching tube.

As a result, even when the first heat transfer tube is larger in heat exchange quantity than the second heat transfer tube, suppressed is increase in difference between a degree of superheating generated in the first heat transfer tube and a degree of superheating generated in the second heat transfer tube. This inhibits deterioration in performance of the heat exchanger due to the difference in degree of superheating between the first heat transfer tube and the second heat transfer tube.

The heat exchanger can thus suppress increase in production cost by adopting the branching tube simply structured, as well as achieve improvement in performance.

A heat exchanger according to a second aspect is the heat exchanger according to the first aspect, in which the first heat transfer tube is disposed windward of the second heat transfer tube.

A heat exchanger according to a third aspect is the heat exchanger according to the first or second aspect, and further includes a third heat transfer tube connected to the third end.

A heat exchanger according to a fourth aspect is the heat exchanger according to the third aspect, in which the third heat transfer tube is disposed windward of the first heat transfer tube.

In the heat exchanger according to the present invention, quantity of the refrigerant flowing out of the first end and quantity of the refrigerant flowing out of the second end are determined in accordance with the pressure loss received by the refrigerant in the first flow path and the pressure loss received by the refrigerant flowing in the second flow path. Accordingly, a ratio between the quantity of the refrigerant flowing into the first heat transfer tube and the quantity of the refrigerant flowing into the second heat transfer tube is determined in accordance with the length ratio between the first flow path and the second flow path.

In an exemplary case where the length ratio between the first flow path and the second flow path is equal to the heat exchange quantity ratio between the first heat transfer tube and the second heat transfer tube, the branching tube can decrease the difference in degree of superheating between a central heat exchange unit and a leeward heat exchange unit, for provision of a heat exchanger exerting higher performance.

A heat exchanger according to a fifth aspect is the heat exchanger according to any one of the first to fourth aspects, in which the branching tube includes a U portion, and an inflow portion having an end connected to the U portion. The U portion includes a bent portion, a first linear portion, and a second linear portion. The bent portion is bent to have a predetermined radius. The first linear portion extends linearly from an end of the bent portion. The second linear portion extends linearly from the other end of the bent portion. The first linear portion has an end far from the bent portion, and the end corresponds to the first end. The second linear portion has an end far from the bent portion, and the end corresponds to the second end. The inflow portion has the end connected to the first linear portion, and the other end corresponding to the third end. The first flow path includes the inflow portion and part of the first linear portion. The second flow path includes the inflow portion, part of the bent portion, and the second linear portion.

In the heat exchanger according to the present disclosure, the branching tube is simply structured to include the U portion and the inflow portion, and can thus be produced at low cost. The first flow path and the second flow path can be easily adjusted in length by changing a position of attachment of the inflow portion to the U portion.

A heat exchanger according to a sixth aspect is the heat exchanger according to the fifth aspect, and further includes a third linear portion extending linearly from a point connected to the first linear portion. In a plain including a center axis of the first linear portion and a center axis of the third linear portion, among angles formed between the center axis of the third linear portion and the center axis of the first linear portion, an angle adjacent to the first end is <NUM> degrees or more and <NUM> degrees or less.

When the angle formed between the center axis of the third linear portion and the center axis of the first linear portion is within this range, in comparison to a case where the angle is less than <NUM> degrees, the refrigerant passing the first flow path flows more smoothly from the inflow portion into the first linear portion. This secures a larger flow rate of the refrigerant flowing into the first heat transfer tube, to provide a heat exchanger exerting higher performance.

A heat exchanger according to the present disclosure is exemplarily applied as a heat exchanger of a refrigeration cycle apparatus configured to achieve a vapor compression refrigeration cycle, though not limited in terms of its use. Described herein with reference to the drawings is a case where the heat exchanger according to the present disclosure is applied as a heat source heat exchanger <NUM> of an air conditioner <NUM> exemplifying the refrigeration cycle apparatus. The air conditioner merely exemplifies the refrigeration cycle apparatus. The heat exchanger according to the present disclosure may be applied to a different refrigeration cycle apparatus such as a refrigerator, a freezer, a hot water supplier, or a floor heater. Description is hereinafter made initially to the air conditioner <NUM> including the heat source heat exchanger <NUM>. Described thereafter are details of the heat source heat exchanger <NUM>.

The air conditioner <NUM> will be described with reference to the drawings. <FIG> is a schematic configuration diagram of the air conditioner <NUM> including, as the heat source heat exchanger <NUM>, a heat exchanger according to an embodiment of the present disclosure.

The air conditioner <NUM> is configured to achieve the vapor compression refrigeration cycle to cool and heat an air conditioning target space. Examples of the air conditioning target space include a space in a building such as an office building, a commercial facility, or a residence.

As depicted in <FIG>, the air conditioner <NUM> principally includes a heat source unit <NUM>, a utilization unit <NUM>, a liquid-refrigerant connection pipe <NUM>, a gas-refrigerant connection pipe <NUM>, and a control unit <NUM> configured to control devices constituting the heat source unit <NUM> and the utilization unit <NUM>. The liquid-refrigerant connection pipe <NUM> and the gas-refrigerant connection pipe <NUM> are refrigerant connection pipes connecting the heat source unit <NUM> and the utilization unit <NUM>. In the air conditioner <NUM>, the heat source unit <NUM> and the utilization unit <NUM> are connected via the refrigerant connection pipes <NUM> and <NUM> to constitute a refrigerant circuit <NUM>.

The air conditioner <NUM> depicted in <FIG> includes the single utilization unit <NUM>. The air conditioner <NUM> may alternatively include a plurality of utilization units <NUM> connected parallelly to the heat source unit <NUM> by the refrigerant connection pipes <NUM> and <NUM>. The air conditioner <NUM> may still alternatively include a plurality of heat source units <NUM>. Furthermore, the air conditioner <NUM> may be of an integral type including the heat source unit <NUM> and the utilization unit <NUM> that are formed integrally with each other.

As depicted in <FIG>, the heat source unit <NUM> principally includes an accumulator <NUM>, a compressor <NUM>, a flow direction switching mechanism <NUM>, the heat source heat exchanger <NUM>, an expansion mechanism <NUM>, a liquid-side shutoff valve <NUM>, a gas-side shutoff valve <NUM>, and a heat source fan <NUM>. As depicted in <FIG>, the utilization unit <NUM> principally includes a utilization heat exchanger <NUM> and a utilization fan <NUM>.

The air conditioner <NUM> will be described in terms of its behavior.

During cooling operation, the control unit <NUM> controls behavior of the flow direction switching mechanism <NUM> to switch the refrigerant circuit <NUM> into a state where the heat source heat exchanger <NUM> functions as a refrigerant radiator (condenser) and the utilization heat exchanger <NUM> functions as a refrigerant evaporator. Specifically, the control unit <NUM> controls behavior of the flow direction switching mechanism <NUM> to cause a suction tube <NUM> connected to a suction side of the compressor <NUM> to communicate with a second gas refrigerant tube <NUM> connecting the flow direction switching mechanism <NUM> and the gas-side shutoff valve <NUM>. Furthermore, the control unit <NUM> controls behavior of the flow direction switching mechanism <NUM> to cause a discharge tube <NUM> connected to a discharge side of the compressor <NUM> to communicate with a first gas refrigerant tube <NUM> connecting the flow direction switching mechanism <NUM> and a gas side of the heat source heat exchanger <NUM> (see solid lines in the flow direction switching mechanism <NUM> in <FIG>). During cooling operation, the control unit <NUM> operates the compressor <NUM>, the heat source fan <NUM>, and the utilization fan <NUM>. During cooling operation, the control unit <NUM> adjusts, in accordance with measurement values and the like of various sensors, the compressor <NUM>, the number of revolutions of a motor of each of the heat source fan <NUM> and the utilization fan <NUM>, and an electronic expansion valve exemplifying the expansion mechanism <NUM> to have a predetermined opening degree.

When the control unit <NUM> controls behavior of various devices in the air conditioner <NUM>, a low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor <NUM>, is compressed to have high pressure in the refrigeration cycle, and is then discharged from the compressor <NUM>. The high-pressure gas refrigerant discharged from the compressor <NUM> is sent to the heat source heat exchanger <NUM> via the flow direction switching mechanism <NUM>. The high-pressure gas refrigerant sent to the heat source heat exchanger <NUM> exchanges heat with air serving as a cooling source supplied by the heat source fan <NUM> in the heat source heat exchanger <NUM> functioning as a refrigerant radiator, to radiate heat and come into a high-pressure liquid refrigerant. The high-pressure liquid refrigerant obtained by radiating heat in the heat source heat exchanger <NUM> is sent to the expansion mechanism <NUM> via a liquid refrigerant tube <NUM>. In the expansion mechanism <NUM>, the high-pressure liquid refrigerant is decompressed to come into a low-pressure refrigerant in a gas-liquid two-phase state. The low-pressure refrigerant in the gas-liquid two-phase state obtained by decompression in the expansion mechanism <NUM> is sent to the utilization heat exchanger <NUM> via the liquid refrigerant tube <NUM>, the liquid-side shutoff valve <NUM>, and the liquid-refrigerant connection pipe <NUM>. The low-pressure refrigerant in the gas-liquid two-phase state sent to the utilization heat exchanger <NUM> exchanges heat to be evaporated, with air supplied into the air conditioning target space by the utilization fan <NUM> in the utilization heat exchanger <NUM> functioning as a refrigerant evaporator. In this case, air cooled through heat exchange with the refrigerant is supplied into the air conditioning target space to cool the air conditioning target space. A low-pressure gas refrigerant obtained by evaporation in the utilization heat exchanger <NUM> is sucked into the compressor <NUM> again via the gas-refrigerant connection pipe <NUM>, the gas-side shutoff valve <NUM>, the flow direction switching mechanism <NUM>, and the accumulator <NUM>.

During heating operation, the control unit <NUM> controls behavior of the flow direction switching mechanism <NUM> to switch the refrigerant circuit <NUM> into a state where the heat source heat exchanger <NUM> functions as a refrigerant evaporator and the utilization heat exchanger <NUM> functions as a refrigerant radiator (condenser). Specifically, the control unit <NUM> controls behavior of the flow direction switching mechanism <NUM> to cause the suction tube <NUM> to communicate with the first gas refrigerant tube <NUM> and cause the discharge tube <NUM> to communicate with the second gas refrigerant tube <NUM> (see broken lines in the flow direction switching mechanism <NUM> in <FIG>). During heating operation, the control unit <NUM> operates the compressor <NUM>, the heat source fan <NUM>, and the utilization fan <NUM>. During heating operation, the control unit <NUM> adjusts, in accordance with measurement values and the like of various sensors, the compressor <NUM>, the number of revolutions of the motor of each of the heat source fan <NUM> and the utilization fan <NUM>, and the electronic expansion valve exemplifying the expansion mechanism <NUM> to have a predetermined opening degree.

When the control unit <NUM> controls behavior of various devices in the air conditioner <NUM> in this manner, the low-pressure gas refrigerant in the refrigeration cycle is sucked into the compressor <NUM>, is compressed to have high pressure in the refrigeration cycle, and is then discharged from the compressor <NUM>. The high-pressure gas refrigerant discharged from the compressor <NUM> is sent to the utilization heat exchanger <NUM> via the flow direction switching mechanism <NUM>, the gas-side shutoff valve <NUM>, and the gas-refrigerant connection pipe <NUM>. The high-pressure gas refrigerant sent to the utilization heat exchanger <NUM> exchanges heat with air supplied into the air conditioning target space by the utilization fan <NUM> in the utilization heat exchanger <NUM> functioning as a refrigerant radiator (condenser) to radiate heat and come into a high-pressure liquid refrigerant. In this case, air heated through heat exchange with the refrigerant is supplied into the air conditioning target space to heat the air conditioning target space. The high-pressure liquid refrigerant obtained by radiating heat in the utilization heat exchanger <NUM> is sent to the expansion mechanism <NUM> via the liquid-refrigerant connection pipe <NUM>, the liquid-side shutoff valve <NUM>, and the liquid refrigerant tube <NUM>. The refrigerant sent to the expansion mechanism <NUM> is decompressed by the expansion mechanism <NUM> to come into a low-pressure refrigerant in the gas-liquid two-phase state. The low-pressure refrigerant in the gas-liquid two-phase state obtained by decompression in the expansion mechanism <NUM> is sent to the heat source heat exchanger <NUM> via the liquid refrigerant tube <NUM>. The low-pressure refrigerant in the gas-liquid two-phase state sent to the heat source heat exchanger <NUM> exchanges heat with air serving as a heating source supplied by the heat source fan <NUM> in the heat source heat exchanger <NUM> functioning as a refrigerant evaporator to be evaporated and come into a low-pressure gas refrigerant. The low-pressure refrigerant obtained by evaporation in the heat source heat exchanger <NUM> is sucked into the compressor <NUM> again via the flow direction switching mechanism <NUM> and the accumulator <NUM>.

The heat source unit <NUM> will be described next in terms of its shape, structure, and the like.

<FIG> is a schematic external perspective view of the heat source unit <NUM>. <FIG> is a schematic front view of the heat source unit <NUM> (excluding refrigerant circuit constituent components other than the heat source heat exchanger <NUM>). <FIG> is a schematic plan view of the heat source unit <NUM> (excluding a fan module <NUM> to be described later and the refrigerant circuit constituent components other than the heat source heat exchanger <NUM>).

The following description may include expressions such as "up", "down", "left", "right", "front", "rear", "front surface", and "rear surface" to indicate directions and positional relationships. The directions indicated by these expressions follow directions of arrows in the drawings unless otherwise specified.

The heat source unit <NUM> is a heat exchange unit of an upward blow type configured to suck air via a side surface of a casing <NUM> and send out air via a top surface of the casing <NUM>.

The heat source unit <NUM> principally includes the casing <NUM> having a substantially rectangular parallelepiped box shape, and the refrigerant circuit constituent components constituting part of the refrigerant circuit <NUM>. The refrigerant circuit constituent components include the accumulator <NUM>, the compressor <NUM>, the heat source heat exchanger <NUM>, the flow direction switching mechanism <NUM>, the expansion mechanism <NUM>, the liquid-side shutoff valve <NUM>, the gas-side shutoff valve <NUM>, and the like. The heat source fan <NUM> and the refrigerant circuit constituent components are accommodated in the casing <NUM>.

The casing <NUM> principally includes a pair of installation legs <NUM> extending transversely, a bottom frame <NUM> spanning the pair of installation legs <NUM>, a pillar <NUM>, the fan module <NUM>, and a side panel <NUM>. The pillar <NUM> extends vertically from a corner of the bottom frame <NUM>. The fan module <NUM> is attached to an upper end of the pillar <NUM>. The side panel <NUM> is a plate-shaped member. The side panel <NUM> is disposed to cover a front surface and a front-side portion of a left side surface of the heat source unit <NUM>.

The bottom frame <NUM> constitutes a bottom surface of the casing <NUM>. The bottom frame <NUM> is provided thereon with the heat source heat exchanger <NUM>, the compressor <NUM>, the accumulator <NUM>, and the like.

The side panel <NUM> is a plate-shaped member extending vertically from the bottom frame <NUM> to the fan module <NUM>. The side panel <NUM> is approximately positioned not to face a heat exchange unit <NUM> to be described later, of the heat source heat exchanger <NUM>. The side panel <NUM> includes a front panel 45a disposed to the front surface and a left side panel 45b disposed to the left side surface.

The front panel 45a extends transversely from a position adjacent to a right end 50R of the heat exchange unit <NUM> to be described later to a left front corner of the heat source unit <NUM>.

The left side panel 45b extends anteroposteriorly from the left front corner of the heat source unit <NUM> to a position adjacent to a left end <NUM> of the heat exchange unit <NUM>.

The fan module <NUM> is disposed above the heat source heat exchanger <NUM> (on the casing <NUM>). The fan module <NUM> is an aggregate including a substantially rectangular parallelepiped box having opened upper and lower faces and the heat source fan <NUM> accommodated in the box. The fan module <NUM> has a top opening serving as an air blow-out port 40b of the casing <NUM>. The air blow-out port 40b is provided with a blow-out grill <NUM>. The heat source fan <NUM> is disposed to face the air blow-out port 40b in the casing <NUM>. As indicated by arrows in <FIG> and <FIG>, the heat source fan <NUM> imports air into the casing <NUM> via an air intake port 40a in the side surface of the casing <NUM> and discharges air via the air blow-out port 40b.

The air intake port 40a is provided in the side surface (in this case, each of a front surface, a rear surface, and right and left side surfaces) of the casing <NUM>, and the air blow-out port 40b is provided in the top surface. As indicated by the arrows in <FIG> and <FIG>, air having passed the air intake port 40a is imported from outside to inside the casing <NUM> by an air flow generated by the heat source fan <NUM> accommodated in the fan module <NUM>. The air intake ports 40a include an air intake port 40a1 provided in the front surface, an air intake port 40a2 provided in a right side surface, an air intake port 40a3 provided in the rear surface, and an air intake port 40a4 provided in a left side surface.

The heat source heat exchanger <NUM> is configured to cause heat exchange between a refrigerant and outdoor air. The heat source heat exchanger <NUM> is a fin-and-tube heat exchanger of a cross-fin type. The heat source heat exchanger <NUM> includes three heat exchange units <NUM>, a plurality of branching tubes <NUM>, and a U tube <NUM>. The heat source heat exchanger <NUM> is an exemplary heat exchanger. The heat exchange units <NUM>, the branching tubes <NUM>, and the U tube <NUM> are made of aluminum or an aluminum alloy, and are joined by brazing.

The heat source heat exchanger <NUM> is formed into a substantially quadrilateral shape in a planar view so as to follow the side surfaces of the casing <NUM> (see <FIG>). However, the heat source unit <NUM> is not provided, at a front side except a right portion and at a left front side, with the heat exchange units <NUM> of the heat source heat exchanger <NUM> that is formed into a substantially quadrilateral shape with an absent portion (a left front portion).

The heat exchange units <NUM> include a windward heat exchange unit 50a, a central heat exchange unit 50b, and a leeward heat exchange unit 50c. Hereinafter, the windward heat exchange unit 50a, the central heat exchange unit 50b, and the leeward heat exchange unit 50c will also be collectively called the heat exchange units <NUM>.

The heat exchange units <NUM> are each constituted by a plurality of heat transfer tubes <NUM> extending horizontally to have a predetermined shape. Specifically, the windward heat exchange unit 50a is constituted by a plurality of heat transfer tubes 52a, the central heat exchange unit 50b is constituted by a plurality of heat transfer tubes 52b, and the leeward heat exchange unit 50c is constituted by a plurality of heat transfer tubes 52c. Hereinafter, the heat transfer tubes 52a, 52b, and 52c will also be collectively called the heat transfer tubes <NUM>.

The heat transfer tubes <NUM> are each formed into a substantially quadrilateral shape having each side following the side surfaces of the casing <NUM> in a planar view, and partially absent at the front side except the right portion and at the left front side of the heat source unit <NUM>. The heat transfer tubes <NUM> of each of the heat exchange units <NUM> are provided to have a predetermined number along a column direction as a normal direction.

The windward heat exchange unit 50a, the central heat exchange unit 50b, and the leeward heat exchange unit 50c are aligned in a direction of the air flow generated by the heat source fan <NUM>. The direction of the air flow generated by the heat source fan <NUM> indicates an air flow direction (in a planar view) when the heat exchange units <NUM> are viewed from above. The heat exchange units <NUM> are disposed in the order of the windward heat exchange unit 50a, the central heat exchange unit 50b, and the leeward heat exchange unit 50c from a windward side in the direction of the air flow generated by the heat source fan <NUM>. In other words, the windward heat exchange unit 50a is disposed outside the central heat exchange unit 50b so as to surround the central heat exchange unit 50b in a planar view. The central heat exchange unit 50b is disposed outside the leeward heat exchange unit 50c so as to surround the leeward heat exchange unit 50c in a planar view.

In this manner, in each of the heat exchange units <NUM>, the heat transfer tubes <NUM> are disposed to have multiple columns in the normal direction (column direction), and to have multiple rows (three rows in this case) in an air ventilation direction (row direction).

The heat exchange units <NUM> are disposed as described above, and the heat source fan <NUM> thus generates the air flow such that the windward heat exchange unit 50a is larger in heat exchange quantity than the central heat exchange unit 50b and the central heat exchange unit 50b is larger in heat exchange quantity than the leeward heat exchange unit 50c.

The heat transfer tubes <NUM> are supported by a plurality of fins 50d to have a predetermined gap therebetween in the normal direction. The fins 50d are each provided with a hole (not depicted) to receive the heat transfer tube <NUM>. The plurality of fins 50d is aligned to be perpendicular to a horizontal direction and have a predetermined gap therebetween in an extending direction of the heat transfer tubes <NUM>. The heat transfer tubes <NUM> are inserted to the holes provided in the fins 50d to be supported by the fins 50d. For effective heat exchange between the refrigerant and outdoor air, the heat transfer tubes <NUM> are disposed in the normal direction such that center axes of the heat transfer tubes <NUM> of the heat exchange units <NUM> are not overlapped with each other when viewed in the horizontal direction. <FIG> depicts only part of the plurality of fins 50d for convenience.

Each of the heat exchange units <NUM> has pipes disposed at the right end 50R and the left end <NUM> so as to allow the incoming refrigerant to flow in the normal direction while meandering in the heat transfer tubes <NUM>. The right end 50R of the heat exchange unit <NUM> is positioned in a right portion of the front surface of the heat source unit <NUM> in a planar view. The left end <NUM> of the heat exchange unit <NUM> is positioned in a front portion of a left surface of the heat source unit <NUM> in a planar view. More specifically, the heat transfer tubes <NUM> have right ends 52R positioned at the right end 50R and provided with a plurality of U tubes <NUM>. The heat transfer tubes <NUM> have left ends <NUM> positioned at the left end <NUM> and provided with a plurality of branching tubes <NUM>.

Each of the U tubes <NUM> connects a right end 52bR of the heat transfer tube 52b and a right end 52cR of the heat transfer tube 52c at a predetermined column with a right end 52aR of the heat transfer tube 52a at an immediately upper column. During heating operation of the air conditioner <NUM>, the refrigerant flowing out of the right end 52bR of the heat transfer tube 52b and the right end 52cR of the heat transfer tube 52c at the predetermined column passes the U tube <NUM> to flow into the windward heat exchange unit 50a at the immediately upper column.

Each of the branching tubes <NUM> connects a left end 52aL of the heat transfer tube 52a at a predetermined column with a left end 52bL of the heat transfer tube 52b and a left end 52cL of the heat transfer tube 52c at the identical column. The branching tube <NUM> will be described in detail later.

The heat transfer tubes 52a constituting the windward heat exchange unit 50a each exemplify a third heat transfer tube. The heat transfer tubes 52b constituting the central heat exchange unit 50b each exemplify a first heat transfer tube. The heat transfer tubes 52c constituting the leeward heat exchange unit 50c each exemplify a second heat transfer tube.

The branching tube <NUM> branches the refrigerant flowing out of the heat transfer tube 52a of the windward heat exchange unit 50a to enter the heat transfer tube 52b of the central heat exchange unit 50b and the heat transfer tube 52c of the leeward heat exchange unit 50c. The branching tube <NUM> has three ends including a first end 80a, a second end 80b, and a third end 80c, and these ends are connected to each other.

<FIG> is a schematic perspective view of the branching tubes <NUM> and the periphery thereof, depicting an attached state to the heat exchange unit <NUM>. <FIG> is a schematic perspective view of the branching tube <NUM>.

The branching tube <NUM> includes a U portion <NUM> and an inflow portion <NUM>. The U portion <NUM> and the inflow portion <NUM> are pipes identical in inner diameter and different in shape.

The U portion <NUM> divides the refrigerant flowing in from the inflow portion <NUM> into two flows to enter the heat transfer tube 52b and the heat transfer tube 52c. The U portion <NUM> includes a bent portion 81a, a first linear portion 81b, and a second linear portion 81c.

The bent portion 81a is bent to have a predetermined radius. The first linear portion 81b extends linearly from an end of the bent portion 81a to have a predetermined length. The second linear portion 81c extends linearly from the other end of the bent portion 81a to have a predetermined length. The first end 80a is an end far from the bent portion 81a, of the first linear portion 81b. The second end 80b is an end far from the bent portion 81a, of the second linear portion 81c.

The inflow portion <NUM> allows the refrigerant flowing out of the heat transfer tube 52a of the windward heat exchange unit 50a to flow into the U portion <NUM>. The inflow portion <NUM> has a first end connected to the first linear portion 81b. The third end 80c is an end far from the first linear portion 81b, of the inflow portion <NUM>.

The branching tube <NUM> has flow paths having flows of the refrigerant and including a first flow path C1 and a second flow path C2. The first flow path C1 connects the first end 80a and the third end 80c, and includes therebetween the inflow portion <NUM> and part of the first linear portion 81b. The first flow path C1 is depicted by two-dot chain lines in <FIG>. The second flow path C2 connects the second end 80b and the third end 80c, and includes therebetween the inflow portion <NUM>, part of the bent portion 81a, and the second linear portion 81c. The second flow path C2 is depicted by broken lines in <FIG>. The branching tube <NUM> is formed such that the first flow path C1 is shorter than the second flow path C2.

The first flow path C1 and the second flow path C2 in the branching tube <NUM> may be formed to have a length ratio corresponding to a heat exchange quantity ratio between the heat transfer tube 52b and the heat transfer tube 52c connected to the branching tube <NUM>. For example, the length ratio between the first flow path C1 and the second flow path C2 may be equal to the heat exchange quantity ratio between the heat transfer tube 52b and the heat transfer tube 52c connected to the branching tube <NUM>.

The branching tube <NUM> connects the left end 52aL of the heat transfer tube 52a with the left end 52bL of the heat transfer tube 52b and a left end 52cL of the heat transfer tube 52c disposed at the identical column. More specifically, the first end 80a of the branching tube <NUM> is connected to the left end 52bL of the heat transfer tube 52b. Furthermore, the second end 80b of the branching tube <NUM> is connected to the left end 52cL of the heat transfer tube 52c. Moreover, the third end 80c of the branching tube <NUM> is connected to the left end 52aL of the heat transfer tube 52a.

The refrigerant flows as follows in the heat source heat exchanger <NUM>.

When the air conditioner <NUM> executes heating operation and the heat source heat exchanger <NUM> functions as a refrigerant evaporator, a refrigerant in the gas-liquid two-phase state flows from the liquid refrigerant tube <NUM> into the heat transfer tube <NUM> at the lowermost column. In this case, the heat transfer tube receiving the refrigerant may be either the heat transfer tube 52b of the central heat exchange unit 50b or the heat transfer tube 52c of the leeward heat exchange unit 50c. The refrigerant flowing from the left end <NUM> into the heat transfer tube <NUM> flows in the heat transfer tube <NUM> to the right end 52R, then passes the U tube <NUM>, and flows into a right end 52aR of the heat transfer tube 52a of the windward heat exchange unit 50a disposed at the immediately upper column. The refrigerant flowing into the heat transfer tube 52a flows to the left end 52aL, then passes the third end 80c, and flows into the inflow portion <NUM> of the branching tube <NUM>.

The refrigerant flowing into the branching tube <NUM> passes the inflow portion <NUM> and then flows into the U portion <NUM> to be branched. The refrigerant flowing into the branching tube <NUM> is thus divided to the refrigerant flowing in the first flow path C1 and the refrigerant flowing in the second flow path C2. Specifically, the refrigerant flowing in the first flow path C1 passes the inflow portion <NUM>, flows into the first linear portion 81b, and flows out of the first end 80a. The refrigerant flowing out of the first end 80a flows into the heat transfer tube 52b of the central heat exchange unit 50b. The refrigerant flowing in the second flow path C2 passes the inflow portion <NUM>, flows into the bent portion 81a, then passes the second linear portion 81c, and flows out of the second end 80b. The refrigerant flowing out of the second end 80b flows into the heat transfer tube 52c of the leeward heat exchange unit 50c. In other words, the refrigerant flowing from the heat transfer tube 52a into the branching tube <NUM> passes the branching tube <NUM> and then flows into the heat transfer tubes 52b and 52c at the identical column with the heat transfer tube 52a.

The refrigerant flowing into the heat transfer tubes 52b and 52c flows toward the right ends 50bR and 50cR, then passes the U tube <NUM>, and flows into the heat transfer tube 52a at the immediate upper column. The refrigerant flowing into the heat transfer tube 52a flows in the heat transfer tube 52a to the left end 52aL, then flows into the branching tube <NUM> connected to the left end 52aL, and flows again into the heat transfer tubes 52b and 52c at the identical column with the heat transfer tube 52a.

As described above, the refrigerant flowing from the liquid refrigerant tube <NUM> into the heat exchange unit <NUM> flows upward while meandering in the heat transfer tube <NUM>. The refrigerant then flows out of the heat transfer tube 52a at the predetermined column, flows to outside the heat source heat exchanger <NUM>, and flows into the first gas refrigerant tube <NUM>.

The heat source heat exchanger <NUM> according to the present disclosure includes the central heat exchange unit 50b (the first heat transfer tube), the leeward heat exchange unit 50c (second heat transfer tube), and the branching tube <NUM>. The branching tube <NUM> has the first end 80a connected to an end of the central heat exchange unit 50b, the second end 80b connected to an end of the leeward heat exchange unit 50c, and the third end 80c. The branching tube <NUM> connects the first end 80a, the second end 80b, and the third end 80c to each other. The central heat exchange unit 50b is larger in heat exchange quantity than the leeward heat exchange unit 50c. The branching tube <NUM> includes the first flow path C1 connecting the first end 80a and the third end 80c, and the second flow path C2 connecting the second end 80b and the third end 80c, and the first flow path C1 is shorter than the second flow path C2.

In the heat source heat exchanger <NUM>, the first flow path C1 is shorter than the second flow path C2. Accordingly, the refrigerant flowing in the first flow path C1 receives a pressure loss smaller than a pressure loss received by the refrigerant flowing in the second flow path C2. The refrigerant flowing into the heat transfer tube 52b via the branching tube <NUM> is thus larger in flow rate than the refrigerant flowing into the heat transfer tube 52c via the branching tube <NUM>.

As a result, even when the heat transfer tube 52b is larger in heat exchange quantity than the heat transfer tube 52c, suppressed is increase in difference between a degree of superheating generated in the heat transfer tube 52b and a degree of superheating generated in the heat transfer tube 52c. This inhibits deterioration in performance of the heat source heat exchanger <NUM> due to the difference in degree of superheating between the heat transfer tube 52b and the heat transfer tube 52c.

The heat source heat exchanger <NUM> can thus suppress increase in production cost by adopting the branching tube <NUM> simply structured, as well as achieve improvement in performance.

In the heat source heat exchanger <NUM>, the first flow path C1 and the second flow path C2 in the branching tube <NUM> may be formed to have a length ratio corresponding to a heat exchange quantity ratio between the heat transfer tube 52b and the heat transfer tube 52c connected to the branching tube <NUM>.

As described above, in the heat source heat exchanger <NUM>, quantity of the refrigerant flowing out of the first end 80a and quantity of the refrigerant flowing out of the second end 80b are determined in accordance with the pressure loss received by the refrigerant in the first flow path C1 and the pressure loss received by the refrigerant flowing in the second flow path C2. Accordingly, a ratio between the quantity of the refrigerant flowing into the heat transfer tube 52b and the quantity of the refrigerant flowing into the heat transfer tube 52c is determined in accordance with the length ratio between the first flow path C1 and the second flow path C2.

Therefore, in an exemplary case where the length ratio between the first flow path C1 and the second flow path C2 is equal to the heat exchange quantity ratio between the heat transfer tube 52b and the heat transfer tube 52c connected with the branching tube <NUM>, the branching tube <NUM> can decrease the difference in degree of superheating between the heat transfer tube 52b and the heat transfer tube 52c, for provision of the heat source heat exchanger <NUM> exerting higher performance.

In the heat source heat exchanger <NUM>, the branching tube <NUM> includes the U portion <NUM>, and the inflow portion <NUM> having an end connected to the U portion <NUM>. The U portion <NUM> includes the bent portion 81a, the first linear portion 81b, and the second linear portion 81c. The bent portion 81a is bent to have the predetermined radius. The first linear portion 81b extends linearly from an end of the bent portion 81a. The second linear portion 81c extends linearly from the other end of the bent portion 81a. The first linear portion 81b has an end far from the bent portion 81a, and the end corresponds to the first end 80a. The second linear portion 81c has an end far from the bent portion 81a, and the end corresponds to the second end 80b. The inflow portion <NUM> has the end connected to the first linear portion 81b, and the other end corresponding to the third end 80c. The first flow path C1 includes the inflow portion <NUM> and part of the first linear portion 81b. The second flow path C2 includes the inflow portion <NUM>, part of the bent portion 81a, and the second linear portion 81c.

In the heat source heat exchanger <NUM>, the branching tube <NUM> is simply structured to include the U portion <NUM> and the inflow portion <NUM>, and can thus be produced at low cost. The first flow path C1 and the second flow path C2 can be easily adjusted in length by changing a position of attachment of the inflow portion <NUM> to the U portion <NUM>.

Description is made hereinafter to modifications to the embodiment described above. Part or entirety of any one of the modification examples may be combined with contents of a different one of the modification examples within a range causing no inconsistency therebetween.

The inflow portion <NUM> may include the third linear portion 82a extending linearly from a point connected to the first linear portion 81b. <FIG> is a sectional view of the branching tube <NUM> according to the modification example <NUM>, the branching tube <NUM> including the third linear portion 82a. <FIG> is a sectional view of the branching tube <NUM> according to the modification example <NUM>, taken along a plane including the first linear portion 81b and the third linear portion 82a.

When the branching tube <NUM> includes the third linear portion 82a, in a plain including a center axis of the first linear portion 81b and a center axis of the third linear portion 82a, among angles formed between the center axis of the third linear portion 82a and the center axis of the first linear portion 81b, an angle θ adjacent to the first end 80a is preferably <NUM> degrees or more and <NUM> degrees or less.

When the angle θ is within the above range, in comparison to a case where the angle θ is less than <NUM> degrees, the refrigerant passing the first flow path C1 flows more smoothly from the inflow portion <NUM> into the first linear portion 81b. This secures a larger flow rate of the refrigerant flowing into the heat transfer tube 52b, to provide the heat source heat exchanger <NUM> exerting higher performance.

The above description refers to the heat source heat exchanger <NUM> having the three rows constituted by the windward heat exchange unit 50a, the central heat exchange unit 50b, and the leeward heat exchange unit 50c. The branching tube <NUM> may alternatively be applied to a heat exchanger constituted by heat exchange units forming two rows.

The above description refers to the exemplary case where the third end 80c of the branching tube <NUM> is connected to the heat transfer tube <NUM> of the heat exchange unit <NUM>. The third end 80c may alternatively be connected to a tube other than the heat transfer tube <NUM>.

For example, the third end 80c may be connected to the first gas refrigerant tube <NUM> or the liquid refrigerant tube <NUM>, and the first end 80a and the second end 80b may be connected to the heat transfer tubes <NUM> different in heat exchange quantity. The branching tube <NUM> can thus differentiate in flow rate between the refrigerants flowing into the two heat transfer tubes <NUM> via the first gas refrigerant tube <NUM> or the liquid refrigerant tube <NUM>. This can inhibit deterioration in performance of the heat exchange unit <NUM> due to the difference in heat exchange quantity between the two heat transfer tubes <NUM>.

The above description refers to the heat source heat exchanger <NUM> having the difference in heat exchange quantity caused by disposing, on the windward side and the leeward side, the two heat transfer tubes <NUM> connected with the first end 80a and the second end 80b of the branching tube <NUM>. However, the difference in heat exchange quantity between the two heat transfer tubes <NUM> is not limitedly due to this configuration. For example, the branching tube <NUM> may be applied to a heat exchanger having a difference in heat exchange quantity between the two heat transfer tubes <NUM> due to a difference in wind speed of air hitting the heat transfer tubes <NUM>.

The above description exemplifies the case where the branching tube <NUM> is applied to the heat source heat exchanger <NUM>. The branching tube <NUM> may alternatively be applied to the utilization heat exchanger <NUM>.

Claim 1:
A heat exchanger (<NUM>) comprising:
a first heat transfer tube (52b);
a second heat transfer tube (52c); and
a branching tube (<NUM>) having a first end (80a) connected to an end of the first heat transfer tube, a second end (80b) connected to an end of the second heat transfer tube, and a third end (80c), and connecting the first end, the second end, and the third end to each other, wherein
the first heat transfer tube is larger in heat exchange quantity than the second heat transfer tube,
the branching tube has a first flow path (C1) connecting the first end and the third end, and a second flow path (C2) connecting the second end and the third end, the first flow path being shorter than the second flow path,
characterized in that
the first flow path and the second flow path have a length ratio corresponding to a heat exchange quantity ratio between the first heat transfer tube and the second heat transfer tube.