EP2980516B1

EP2980516B1 - Heat exchanger and refrigeration cycle air conditioner using same

Info

Publication number: EP2980516B1
Application number: EP13880586.6A
Authority: EP
Inventors: Akira Ishibashi; Takuya Matsuda; Takashi Okazaki; Atsushi Mochizuki
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2013-03-27
Filing date: 2013-03-27
Publication date: 2018-01-31
Anticipated expiration: 2033-03-27
Also published as: EP2980516A1; EP2980516A4; JP6157593B2; JPWO2014155560A1; WO2014155560A1; CN203798027U

Description

Technical Field

The present invention relates to a heat exchanger and a refrigeration cycle air-conditioning apparatus using the heat exchanger.

Background Art

Heat exchangers often have a problem of degradation in heat exchanging capacity caused by frost formation. As an invention relating to this problem, a heat exchanger disclosed in Patent Literature 1 is exemplified. In the heat exchanger, heat exchange units are separated from each other in a front-and-back direction and arranged so as to overlap each other in the front-and-back direction. A gap is secured between the pair of heat exchange units and between a pair of header portions arranged above or below the heat exchange units.
The above-mentioned heat exchanger is designed so that, even if any one of the front and back heat exchange units loses a ventilating property due to the frost formation, another one of the heat exchange units can obtain a minimum heat exchanging function owing to a flow of the air passing through the gap. JP2010002102A discloses a heat exchange unit provided with a first fin and tube type heat exchanger and the second parallel flow type heat exchanger the second serpentine type heat exchanger. The first heat exchanger is arranged windward and the second heat exchanger is arranged leeward in an air current generated by an air blower. JP2002013840A discloses a back side core disposed on the back face of a parallel flow type front side core and refrigerant passed through the front side core is introduced to the back side core. JP2000329486A discloses a finned heat exchanger comprising an auxiliary heat exchanger and a main heat exchanger juxtaposed from the gas inlet side to the gas outlet side. The row of heating tube group on the gas inlet side is separated from a plurality of rows of heating tube group on the gas outlet side. Step pitch of the heating tube group on the gas inlet side is set smaller than the step pitch of the heating tube group on the gas outlet side and the number of heating tubes in a row is set lower on the gas inlet side than on the gas outlet side. Since increase in the heat transfer area and the pressure loss is suppressed in the heating tube on the gas inlet side, a high performance auxiliary heat exchanger is realized.

Citation List

Patent Literature

[PTL 1] JP 08-226727 A (FIGS. 1)

Summary of Invention

Technical Problem

However, in the above-mentioned related-art heat exchanger, consideration has not been made to prevent growth of the frost itself when the heat exchanger is used as an evaporator, thereby causing a problem in that it is difficult to eliminate the frost once formed on a lower portion of the heat exchanger.
The present invention has been made in view of the above, and has an object to provide a heat exchanger capable of preventing growth of frost accumulated on a lower portion of the heat exchanger.

Solution to Problem

In order to attain the above-mentioned object, a heat exchanger according to the independent claim is provided. According to one embodiment of the present invention, there is provided a heat exchanger, including: a parallel-flow-type heat exchange unit including a plurality of heat exchange pipes each extending in an up-and-down direction, the parallel-flow-type heat exchange unit including at least a front row portion and a back row portion, the front row portion and the back row portion each including the plurality of heat exchange pipes each extending in the up-and-down direction; and a plate fin-and-tube-type heat exchange unit being arranged in front of a lower portion of a front surface of the parallel-flow-type heat exchange unit, the plate fin-and-tube-type heat exchange unit including a plurality of plate fins each extending in the up-and-down direction, in which an outlet end of the plate fin-and-tube-type heat exchange unit and an inlet end of the parallel-flow-type heat exchange unit are connected to each other by a pipe.

Advantageous Effects of Invention

According to the one embodiment of the present invention, it is possible to prevent the growth of the frost accumulated on the lower portion of the heat exchanger.

Brief Description of Drawings

FIG. 1 is a front view of a heat exchanger according to a first embodiment of the present invention.
FIG. 2 is a side view of the heat exchanger according to the first embodiment.
FIG. 3 is a view similar to FIG. 1 according to a second embodiment of the present invention.
FIG. 4 is a view similar to FIG. 2 according to the second embodiment.
FIG. 5 is a schematic view of a refrigeration cycle air-conditioning apparatus according to a third embodiment of the present invention.
FIG. 6 is a schematic plan view of an outdoor unit of the refrigeration cycle air-conditioning apparatus according to the third embodiment.

Description of Embodiments

Now, embodiments of the present invention are described with reference to the accompanying drawings. Note that, in the drawings, the same reference symbols represent the same or corresponding parts. Further, directions described in this specification are defined as follows. An upstream side of intended ventilation is defined as "front", and a downstream side thereof is defined as "back". An acting direction of gravity is defined as "down", and a direction opposite thereto is defined as "up". In addition, a direction orthogonal to both the front-and-back direction and the up-and-down direction (gravity direction) is defined as "lateral". An example is given with reference to FIG. 2. An up-and-down direction of the drawing sheet of FIG. 2 corresponds to the up-and-down direction defined in this specification. A left side and a right side of the drawing sheet of FIG. 2 correspond to the front side and the back side, respectively. A direction along front and back sides of the drawing sheet of FIG. 2 corresponds to the lateral direction. Note that, reference symbol WD in FIG. 2 denotes an air direction in ventilation.

First Embodiment

FIG. 1 and FIG. 2 are a front view and a side view of a heat exchanger according to a first embodiment of the present invention, respectively. A heat exchanger 1 is an aluminum heat exchanger for use in an outdoor unit of a refrigeration cycle air-conditioning apparatus.
The heat exchanger 1 includes a parallel-flow-type heat exchange unit 3. In front of the parallel-flow-type heat exchange unit 3 of the heat exchanger 1, a plate fin-and-tube-type heat exchange unit 5 is arranged.
First, the parallel-flow-type heat exchange unit 3 includes a front row portion 7 and a back row portion 9 separated from each other in the front-and-back direction and aligned in the front-and-back direction. The front row portion 7 and the back row portion 9 respectively include a plurality of heat exchange pipes 11 and a plurality of heat exchange pipes 13 extending in the up-and-down direction. The heat exchange pipes 11 and 13 are flat pipes each having a shape flattened from the lateral direction. The plurality of heat exchange pipes 11 of the front row portion 7 are aligned in the lateral direction, and the plurality of heat exchange pipes 13 of the back row portion 9 are also aligned in the lateral direction. A gap 15 is secured between the plurality of heat exchange pipes 11 of the front row portion 7 and the plurality of heat exchange pipes 13 of the back row portion 9 in the front-and-back direction, and the heat exchange pipes 11 and the heat exchange pipes 13 are separated from each other in the front-and-back direction. Further, the number of the heat exchange pipes 11 is equal to the number of the heat exchange pipes 13, which is merely an example.
Fins 17 are arranged between the plurality of heat exchange pipes 11 and 13. Specifically, the fins 17 are corrugated fins, and each of the fins 17 extends in the up-and-down direction while meandering laterally between a pair of adjacent fins. In other words, each of the fins 17 is formed into a corrugated shape so as to be alternately held in contact with the left heat exchange pipe and the right heat exchange pipe.
Further, the heat exchange pipes 11 and 13 are arranged in two rows in the fore-and-after direction, whereas the fins 17 are arranged in one row in the front-and-back direction. That is, one piece of the corrugated fins is positioned between a corresponding pair of the heat exchange pipes 11 of the front row portion 7, and also positioned between a corresponding pair of the heat exchange pipes 13 of the back row portion 9. The fins 17 protrude windward from the heat exchange pipes 11 of the front row portion 7. That is, front edge portions of the fins 17 are positioned forward of front ends of the heat exchange pipes 11 of the front row portion 7.
An inlet header 19 serving as a lower header on the front row portion 7 side is arranged below the front row portion 7, and an outlet header 21 serving as a lower header on the back row portion 9 side is arranged below the back row portion 9. A row straddling header 23 is arranged above the front row portion 7 and the back row portion 9. The front row portion 7 and the back row portion 9 share the same row straddling header 23 as an upper header. Note that, the inlet header 19, the outlet header 21, and the row straddling header 23 each have one chamber. As described above, the lower headers are arranged separately for the respective rows of the front row portion 7 and the back row portion 9, and the upper header is integrally arranged for the front row portion 7 and the back row portion 9 in a row straddling manner.
Further, in terms of function, the inlet header 19 and the outlet header 21 arranged below the parallel-flow-type heat exchange unit 3 have a mechanism for attaining uniform distribution to the heat exchange pipes in a windward-side row, and have a mechanism for concentrating gas in a leeward-side row. When the parallel-flow-type heat exchange unit 3 is seen as a whole, the lower headers are arranged separately for the respective rows. On the other hand, the row straddling header 23 arranged above the parallel-flow-type heat exchange unit 3 has a mechanism for enabling refrigerant to move between the rows. When the parallel-flow-type heat exchange unit 3 is seen as a whole, the upper header is integrally arranged for the two rows.
Lower ends of the heat exchange pipes 11 of the front row portion 7 are connected to the inlet header 19, and upper ends of the heat exchange pipes 11 of the front row portion 7 are connected to the row straddling header 23. Further, lower ends of the heat exchange pipes 13 of the back row portion 9 are connected to the outlet header 21, and upper ends of the heat exchange pipes 13 of the back row portion 9 are connected to the row straddling header 23.
The plate fin-and-tube-type heat exchange unit 5 is arranged in front of a lower portion of a front surface of the parallel-flow-type heat exchange unit 3. More specifically, the plate fin-and-tube-type heat exchange unit 5 is arranged in front of the lower portion of the front surface of the front row portion 7 and above the inlet header 19. A lowermost portion of the plate fin-and-tube-type heat exchange unit 5 (lowermost portions of plate fins 25) is positioned between lowermost portions of the fins 17 of the parallel-flow-type heat exchange unit 3 and the inlet header 19.
The plate fin-and-tube-type heat exchange unit 5 includes the plurality of plate fins 25 and a heat transfer pipe 27 for forming at least one passage.
The plurality of plate fins 25 extend in the up-and-down direction, and are aligned substantially in parallel to each other in the lateral direction. Further, back portions of the plurality of plate fins 25 are held in abutment on or close to front ends of lower portions of the fins 17 of the parallel-flow-type heat exchange unit 3.
In the illustrated example, the heat transfer pipe 27 is a circular pipe forming one passage, and extends in the up-and-down direction through the plurality of plate fins 25 while meandering in the lateral direction. An inlet end 27a of the heat transfer pipe 27, which serves as a refrigerant inlet when the heat exchanger functions as an evaporator, is formed in the lower portions of the plate fins 25, whereas an outlet end 27b of the heat transfer pipe 27, which serves as a refrigerant outlet when the heat exchanger functions as the evaporator, is formed in upper portions of the plate fins 25. Note that, as the heat transfer pipe 27, a plurality of circular pipes may be employed to form a plurality of passages as long as the number of the circular pipes is smaller than the number of passages of the parallel-flow-type heat exchange unit 3. Further, instead of the above-mentioned one or the plurality of circular pipes (of a plate fin and circular tube type), one or a plurality of flat pipes (of a plate fin and flat tube type) may be employed as the heat transfer pipe 27.
The plate fin-and-tube-type heat exchange unit 5 and the parallel-flow-type heat exchange unit 3 are connected to each other by a connection pipe 29. That is, one end of the connection pipe 29 is connected to the outlet end 27b of the heat transfer pipe 27 of the plate fin-and-tube-type heat exchange unit 5, and another end of the connection pipe 29 is connected to an inlet end 19a of the inlet header 19 of the parallel-flow-type heat exchange unit 3.
Next, a flow of refrigerant is described. Note that, the arrows illustrated in FIG. 1 and FIG. 2 schematically indicate the flow of the refrigerant when the heat exchanger 1 functions as the evaporator. Therefore, when the heat exchanger 1 functions as a condenser, the refrigerant flows in a direction reverse to the direction indicated by the arrows. When the heat exchanger 1 is used as the evaporator (for example, when the heat exchanger 1 is arranged in the outdoor unit and performs heating operation), the refrigerant flows through one passage in the plate fin-and-tube-type heat exchange unit 5 upward from below, and then flows out of the plate fin-and-tube-type heat exchange unit 5. After passing through the connection pipe 29, the refrigerant flows into the inlet header 19 of the parallel-flow-type heat exchange unit 3. The refrigerant in the inlet header 19 flows upward from below in the plurality of heat exchange pipes 11 of the front row portion 7 located on the windward side. That is, the refrigerant flows upward in the front row portion 7 while dividing into the same number of passages as the number of the heat exchange pipes 11, and then flows into the row straddling header 23. After flowing into the row straddling header 23, the refrigerant further flows downward from above in the plurality of heat exchange pipes 13 of the back row portion 9 located on the leeward side. That is, after flowing downward in the back row portion 9 while dividing into the same number of passages as the number of the heat exchange pipes 13, the refrigerant flows into the outlet header 21, and finally flows out of the heat exchanger 1 .
In the first embodiment configured as described above, the following advantage is attained. The heat exchanger 1 includes the plate fin-and-tube-type heat exchange unit 5, and hence condensed water is led to the plate fins 25 from the inlet header 19 and the fins 17 at the time of operation that may cause frost formation. In other words, the condensed water is mainly concentrated on the plate fin-and-tube-type heat exchange unit 5 having a good draining property, thereby being capable of preventing accumulation of ice on the lower portion of the heat exchanger 1.
Further, the number of passages of the plate fin-and-tube-type heat exchange unit 5 is smaller than the number of passages of the parallel-flow-type heat exchange unit 3, and a pressure loss in the pipes, through which the refrigerant passes, is larger in the plate fin-and-tube-type heat exchange unit 5 than in the parallel-flow-type heat exchange unit 3. Accordingly, an evaporating temperature in the plate fin-and-tube-type heat exchange unit 5 is higher than an evaporating temperature in the parallel-flow-type heat exchange unit 3, and an amount of frost formed at the time of operation is reduced. Thus, it is possible to prevent concentration of frost on the lower portion of the heat exchanger 1. Further, when the heat exchanger 1 is used as the condenser, a flow rate in a subcooled portion can be increased, and a heat transfer coefficient in the pipes can be increased, thereby increasing an efficiency of the heat exchanger.
In addition, when the heat exchanger 1 is used as the evaporator, an inlet of the plate fin-and-tube-type heat exchange unit 5 is formed in the lowermost portion of the plate fin-and-tube-type heat exchange unit 5, and hence a temperature of a lowermost portion of the heat exchanger 1 can be increased. Also with this, the frost formation amount can be suppressed.
Further, the fins 17 for use in the parallel-flow-type heat exchange unit 3 are formed integrally with the heat exchange pipes 11 and 13 arranged in front and back two rows. Accordingly, when the heat exchange pipes 11 and 13 are laid out in the front and back two rows so that the rows are parallel to each other, assembling properties of the heat exchange pipes can be enhanced.
Further, notches for blocking heat are formed in regions of the fins 17 between the front and back rows. With this configuration, heat transfer caused by a temperature difference between the heat exchange pipes 11 and 13 can be prevented, and the efficiency of the heat exchanger can be increased.
Further, the fins 17 are fixed so as to protrude windward from the heat exchange pipes 11. Thus, a temperature of the front edge portions of the fins 17 is approximated to the air temperature, thereby being capable of avoiding concentration of frost on the front edge portions of the fins 17 at the time of operation that may cause frost formation.
Further, a heat exchanging method using the heat exchanger 1 can be exemplified as the first embodiment. In the heat exchanging method, when the heat exchanger 1 functions as the evaporator, the refrigerant and the air flow substantially in parallel to each other (flow in the same direction) (both the refrigerant and the air flow from the front side to the back side as seen in broad perspective). Further, the evaporating temperature of the refrigerant is reduced due to the pressure loss toward a flowing direction of the refrigerant, and the temperature of the air is also reduced toward a flowing direction of the air. Accordingly, a temperature difference between the refrigerant and the air is reduced. On the other hand, when the heat exchanger 1 functions as the condenser, the refrigerant and the air flow in a substantially opposing manner (flow in opposite directions) (the air flows from the front side to the back side, whereas the refrigerant flows from the back side to the front side as seen in broad perspective). Further, the temperature of the refrigerant is reduced in a superheated region, a two-phase region, and a subcooled region toward the flowing direction of refrigerant, whereas the temperature of the air is increased toward the flowing direction of the air. Accordingly, the temperature difference between the refrigerant and the air is reduced. Also in this manner, the efficiency of the heat exchanger is increased. In other words, as a refrigerant passage extending in the parallel-flow-type heat exchange unit 3 and the plate fin-and-tube-type heat exchange unit 5, the heat exchanger 1 has a refrigerant passage allowing the refrigerant and the air to flow in the same direction along the front-and-back direction when the heat exchanger 1 functions as the evaporator, and allowing the refrigerant and the air to flow in opposite directions along the front-and-back direction when the heat exchanger 1 functions as the condenser.

Second Embodiment

Next, a heat exchanger according to a second embodiment of the present invention is described with reference to FIG. 3 and FIG. 4. FIG. 3 and FIG. 4 are views similar to FIG. 1 and FIG. 2 according to the second embodiment. Note that, the second embodiment is the same as the above-mentioned first embodiment except formatters described below. Further, when illustrating a collective connection pipe and divided connection pipes described later, priority is placed on description of a connection state of divided areas, and hence illustrations of the pipes are different from an actual state. Accuracy of illustrations of pipe diameters and pipe lengths is ignored, and the divided connection pipes are illustrated in a non-overlapping manner on purpose both in FIG. 3 and FIG. 4.
A heat exchanger 101 according to the second embodiment includes, as the lower header of the windward-side row, an inlet header 119 having an interior partitioned into a plurality of chambers (three chambers as a specific example) by partition walls, and further includes a distributor 131.
The distributor 131 is arranged on the downstream side of the plate fin-and-tube-type heat exchange unit 5 and on the upstream side of the parallel-flow-type heat exchange unit 3 when the heat exchanger 101 functions as the evaporator. More specifically, the inlet header 119 has inlet ends 119a for the plurality of respective chambers. The outlet end 27b of the heat transfer pipe 27 of the plate fin-and-tube-type heat exchange unit 5 and the distributor 131 are connected to each other by one collective connection pipe 129a, and each of the plurality of (three) inlet ends 119a of the inlet header 119 and the distributor 131 are connected to each other by corresponding one of the plurality of (three) divided connection pipes 129b. The divided connection pipes 129b function as capillary tubes. Note that, at least a front row side of a row straddling header 123 is also partitioned into a plurality of (three) regions so as to correspond to the inlet header 119.
In the second embodiment configured as described above, when the heat exchanger 101 functions as the evaporator, the refrigerant is divided into three passages by the distributor 131 after flowing out of the plate fin-and-tube-type heat exchange unit 5, and flows into the three chambers of the inlet header 119 located below the windward-side row of the parallel-flow-type heat exchange unit 3. Then, the refrigerant flows upward in the heat exchange pipes 11, and moves from one row to another row through the row straddling header 123. After flowing downward in the heat exchange pipes 13, the refrigerant flows out of the outlet header 21 of the leeward-side row.
In the second embodiment configured as described above, the following advantages are attained in addition to the above-mentioned advantage of the first embodiment. The interior of the header, which is arranged below the windward-side row of the parallel-flow-type heat exchange unit 3, is partitioned into the three chambers, thereby reducing sizes of the respective chambers in the header. Thus, distribution of the refrigerant in the header can be adjusted easily. Further, through adjustment of lengths of the plurality of capillary tubes (divided connection pipes) connecting between the distributor and the header, the refrigerant can be distributed uniformly. Further, a pressure loss in the pipes is large in the distributor and the capillary tubes. Accordingly, when the heat exchanger 101 functions as the evaporator, the evaporating temperature in the plate fin-and-tube-type heat exchange unit can be increased, and growth of frost on the lower portion of the heat exchanger can be prevented.

Third Embodiment

Next, a refrigeration cycle air-conditioning apparatus according to a third embodiment of the present invention is described with reference to FIG. 5 and FIG. 6. FIG. 5 is a schematic view of the refrigeration cycle air-conditioning apparatus according to the third embodiment. FIG. 6 is a schematic plan view of an outdoor unit of the refrigeration cycle air-conditioning apparatus according to the third embodiment.
As illustrated in FIG. 5, a refrigeration cycle air-conditioning apparatus 251 includes a refrigeration cycle circuit including at least a compressor 253, an outdoor heat exchanger 255, an expansion device (expansion valve) 257, and an indoor heat exchanger 259. Note that, the arrow illustrated in FIG. 5 indicates the flowing direction of the refrigerant when cooling operation is performed. Further, the refrigeration cycle air-conditioning apparatus 251 includes a fan 261 for blowing the air to each of the outdoor heat exchanger 255 and the indoor heat exchanger 259, and a drive motor 263 for rotating the fan 261.
An interior of a casing of an outdoor unit 351 of the refrigeration cycle air-conditioning apparatus 251 is partitioned by a partition plate 365 into a machine chamber 367 and an air-blowing chamber 369. The compressor 253 is received in the machine chamber 367, and the outdoor heat exchanger 255 and the fan 261 are received in the air-blowing chamber 369.
In the third embodiment, the heat exchanger 1 according to the first embodiment or the heat exchanger 101 according to the second embodiment is used as one of or both of the outdoor heat exchanger 255 and the indoor heat exchanger 259. With this configuration, the refrigeration cycle air-conditioning apparatus with high energy efficiency can be realized. Note that, the energy efficiency is represented by the following equation. $\begin{array}{l} Heating Energy Efficiency = Capacity of Indoor Heat Exchanger \\ (Condenser) / Entire Input \end{array}$
$\begin{array}{l} Cooling Energy Efficiency=Capacity of Indoor Heat Exchanger \\ (Evaporator) / Entire Input \end{array}$
Further, in a case of the parallel-flow-type heat exchange unit using the corrugated fins, the small number of pipes are arranged at each end in the lateral direction, and the heat exchanger (parallel-flow-type heat exchange unit) can be arranged on a substantially entire surface of the casing on the windward side of the fan of the outdoor unit. Accordingly, a satisfactory mounting area can be secured without bending the heat exchanger. Also with this, there is attained an advantage in that heat exchanging efficiency can be increased. Note that, even when the heat exchanger 1 or the heat exchanger 101 is applied to an indoor unit, the heat exchanger (parallel-flow-type heat exchange unit) can be arranged on a substantially entire surface of a casing on a windward side of the fan of the indoor unit, and the same advantage can be attained.
Although the details of the present invention are specifically described above with reference to the preferred embodiments, it is apparent that persons skilled in the art may adopt various modifications based on the basic technical concepts and teachings of the present invention.
First, the heat exchanger 1 and the heat exchanger 101 described in the first and second embodiments, and the refrigeration cycle air-conditioning apparatus 251 using the heat exchanger can achieve the above-mentioned effects when using refrigerant such as R410A, R32, or HFO1234yf.
Further, the air and the refrigerant are exemplified as an operating fluid. However, the same effects can be attained even when other kinds of gas, liquid, and gas-liquid mixture fluids are used.
Further, the heat exchanger 1 and the heat exchanger 101 described in the first and second embodiments can attain the same effects even when used in the indoor unit.
Further, the heat exchanger 1 and the heat exchanger 101 described in the first and second embodiments, and the refrigeration cycle air-conditioning apparatus 251 using the heat exchanger can achieve the above-mentioned effects even when using any kinds of refrigerating machine oils such as mineral oil-based, alkylbenzene oil-based, ester oil-based, ether oil-based, and fluorine oil-based lubricants irrespective of whether or not the oils dissolve in the refrigerant.
Further, as another example of practical use of the present invention, there can be given an example of use in a heat pump apparatus that is required to facilitate manufacture, enhance heat exchanging performance, and enhance energy saving performance.

Reference Signs List

1, 101 heat exchanger, 3 parallel-flow-type heat exchange unit, 5 plate fin-and-tube-type heat exchange unit, 7 front row portion, 9 back row portion, 11, 13 heat exchange pipe, 17 fin, 19, 119 inlet header (lower header), 21 outlet header (lower header), 23 row straddling header (upper header), 25 plate fin, 27 heat transfer pipe, 129a collective connection pipe, 129b divided connection pipe, 131 distributor, 251 refrigeration cycle air-conditioning apparatus, 253 compressor, 255 outdoor heat exchanger, 257 expansion device, 259 indoor heat exchanger, 261 fan

Claims

A heat exchanger, comprising:
a parallel-flow-type heat exchange unit (3) comprising a plurality of heat exchange pipes (11,13) each extending in an up-and-down direction,
the parallel-flow-type heat exchange unit (3) comprising at least a front row portion (7) and a back row portion (9),

the front row portion (7) and the back row portion (9) each comprising the plurality of heat exchange pipes (11,13) each extending in the up-and-down direction;

fins (17) of the parallel-flow-type heat exchange unit (3) protruding forward from the heat exchange pipes (11) of the front row portion (7); and

a plate fin-and-tube-type heat exchange unit (5) being arranged in front of only a lower portion of a front surface of the parallel-flow-type heat exchange unit (3),
the plate fin-and-tube-type heat exchange unit (5) comprising a plurality of plate fins (25) each extending in the up-and-down direction,

wherein an outlet end of the plate fin-and-tube-type heat exchange unit (5) and an inlet end of the parallel-flow-type heat exchange unit (3) are connected to each other by a pipe, and

the plurality of plate fins (25) are held in abutment or close to front ends of the fins (17) of the parallel-flow-type heat exchange unit (3).
A heat exchanger according to claim 1, wherein a lowermost portion of the plate fin-and-tube-type heat exchange unit (5) is positioned between a lowermost portion of each of the fins of the parallel-flow-type heat exchange unit (3) and a lower header of the front row portion.
A heat exchanger according to claim 1 or 2, wherein a circular pipe is used as a heat transfer pipe of the plate fin-and-tube-type heat exchange unit (5).
A heat exchanger according to any one of claims 1 to 3, wherein a number of passages of the plate fin-and-tube-type heat exchange unit (5) is smaller than a number of passages of the parallel-flow-type heat exchange unit (3).
A heat exchanger according to any one of claims 1 to 4, wherein an inlet end of the heat transfer pipe serving as a refrigerant inlet when the heat exchanger functions as an evaporator is arranged in a lower portion of each of the plate fins.
A heat exchanger according to any one of claims 1 to 5, wherein the heat exchanger has a refrigerant passage for allowing refrigerant and air to flow in the same direction along a front-and-back direction when the heat exchanger functions as the evaporator, and for allowing the refrigerant and the air to flow in opposite directions along the front-and-back direction when the heat exchanger functions as a condenser.
A heat exchanger according to any one of claims 1 to 6,
wherein an interior of the lower header (119) of the front row portion (7) is partitioned by a partition wall into a plurality of chambers,
wherein the lower header (119) has inlet ends for the plurality of chambers,
wherein a distributor (131) is arranged between the plate fin-and-tube-type heat exchange unit (5) and the lower header (119) of the front row portion (7),
wherein an outlet end of the plate fin-and-tube-type heat exchange unit (5) and the distributor (131) are connected to each other by a collective connection pipe (129a), and
wherein each of the plurality of inlet ends of the lower header (119) and the distributor (131) are connected to each other by corresponding one of a plurality of divided connection pipes (129b).
A refrigeration cycle air-conditioning apparatus, comprising a refrigeration cycle circuit including a compressor (253), an outdoor heat exchanger (255), an expansion valve (257), and an indoor heat exchanger (259),
wherein one of or both of the outdoor heat exchanger (255) and the indoor heat exchanger (259) is a heat exchanger of any one of claims 1 to 7.
A refrigeration cycle air-conditioning apparatus according to claim 8,
wherein the fins of the parallel-flow-type heat exchange unit (3) comprise corrugated fins, and

wherein the parallel-flow-type heat exchange unit (3) is arranged on an entire surface of a casing on a windward side of a fan of corresponding one of the outdoor heat exchanger and (255) the indoor heat exchanger (259).