JP2008116135A - Heat exchanger and refrigeration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent, in a heater exchanger provided in a refrigerant circuit performing vapor compressing refrigeration cycle and functioning at least as a vaporizer, reduction in heat transfer performance of the heat exchanger resulted from remaining of refrigerating machine oil within the heat exchanger. <P>SOLUTION: A refrigerant passage 26 within the heat exchanger 12, 13 which functions as the vaporizer is formed so that refrigerant flows downward. A refrigerant passage 36, 46, 56 just has to be formed so that the refrigerant flows downward at least in a middle part between an inlet 27 and an outlet 28, and the refrigerant may flow upward in other parts. Particularly, the passage 56 is preferably formed so that the refrigerant flows downward in a range of more than half on the outlet side. A bridge circuit 60 is preferably provided so that the refrigerant flows in the same direction to the heat exchanger 12, 13 even if the circulating direction of refrigerant within a refrigerant circuit 10 is changed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat exchanger applied to a refrigeration apparatus that performs a vapor compression refrigeration cycle, and particularly relates to measures for promoting heat transfer.

  Conventionally, a refrigeration apparatus that performs a vapor compression refrigeration cycle is known, and is widely applied to an air conditioner, a water heater, and the like.

  For example, an air conditioner disclosed in Patent Document 1 has a refrigerant circuit to which a compressor, an outdoor heat exchanger, an expander, and an indoor heat exchanger are connected. This refrigerant circuit is filled with carbon dioxide as a refrigerant.

  For example, in the cooling operation of the air conditioner, the refrigerant compressed to a critical pressure or higher by the compressor flows through the outdoor heat exchanger, and the refrigerant and the outdoor air exchange heat with the outdoor heat exchanger to release heat to the outdoor air. To do. The refrigerant radiated by the outdoor heat exchanger is depressurized by the expander, and then flows through the indoor heat exchanger. The indoor heat exchanger exchanges heat between the refrigerant and the indoor air. It absorbs heat and evaporates. As a result, the room is cooled. The refrigerant evaporated in the indoor heat exchanger is sucked into the compressor and compressed again.

  On the other hand, in the heating operation of the air conditioner, the refrigerant compressed to the critical pressure or higher by the compressor flows through the indoor heat exchanger, and the refrigerant and the indoor air exchange heat with the indoor heat exchanger, thereby returning to the indoor air. Dissipate heat. The refrigerant radiated by the indoor heat exchanger is depressurized by the expander and then flows through the outdoor heat exchanger. The outdoor heat exchanger exchanges heat between the refrigerant and the outdoor air. It absorbs heat and evaporates. The refrigerant evaporated in the outdoor heat exchanger is sucked into the compressor and compressed again.

Thus, although the circulation direction of the refrigerant in the refrigerant circuit differs between the cooling operation and the heating operation, the flow direction of the refrigerant with respect to the heat exchanger generally depends on the function of the heat exchanger in the refrigerant circuit. It has been decided. Specifically, as shown in FIG. 10, when the heat exchanger functions as an evaporator, the refrigerant flows upward as a whole as indicated by a solid arrow, while the heat exchanger functions as a gas cooler. In this case, the refrigerant flows downward as a whole as indicated by a broken arrow. That is, when the heat exchanger functions as an evaporator, the refrigerant flows upward so that the vaporized refrigerant flows easily, and when the heat exchanger functions as a gas cooler, the cooled refrigerant flows. In order to facilitate, the coolant is allowed to flow downward. Here, in FIG. 10, reference numeral 121 is a flat fin, 122 is a heat transfer tube, 122a is a straight tube portion, and 122b is a curved portion.
JP 2001-116371 A

  By the way, in the refrigeration apparatus as described above, lubricating oil (refrigerating machine oil) is used to lubricate each sliding portion of the compressor, and this lubricating oil flows in the refrigerant circuit together with the refrigerant. Therefore, when the refrigerant flows through a heat exchanger such as an evaporator or a gas cooler, the oil that could not be dissolved in the refrigerant adheres to the inner wall of the heat transfer tube, and an oil film is formed over the entire inner wall of the heat transfer tube. There is a case. If it does so, the heat transfer of a refrigerant | coolant and air was inhibited by the oil film, and there existed a problem that the heat transfer performance of a heat exchanger will fall.

  In particular, in a refrigerating apparatus that performs a refrigerating cycle using carbon dioxide as a refrigerant as disclosed in Patent Document 1, it is common to use PAG (polyalkylene glycol) as refrigerating machine oil. Since oil has low compatibility with carbon dioxide, an oil film as described above is easily formed in the heat transfer tube of the heat exchanger. Therefore, in a heat exchanger applied to a refrigeration apparatus using carbon dioxide as a refrigerant, the heat transfer performance is significantly reduced due to the oil film.

  In addition, as described above, the heat exchanger is used as a gas cooler for cooling the refrigerant in the refrigerant circuit or an evaporator for evaporating the refrigerant. In particular, the refrigerant evaporates in the middle, and the refrigerant as a whole moves upward. In the case of an evaporator in which a flow path is formed so that only flows, only the refrigerating machine oil tends to remain inside, and the above-described deterioration in heat transfer performance tends to occur.

  The present invention has been made in view of the above points, and an object of the present invention is to provide at least a heat exchanger provided in a refrigerant circuit for performing a vapor compression refrigeration cycle and functioning as an evaporator. The purpose is to prevent the heat transfer performance of the heat exchanger from deteriorating due to residual refrigeration oil in the chamber.

  In order to achieve the above object, in the heat exchanger (12, 13, 31, 41, 51) according to the present invention, of the flow paths (26, 26 ', 36, 46, 56) formed inside the heat exchanger (12, 13, 31, 41, 51) Refrigerant flows from top to bottom at least in the middle of the inlet (27) and outlet (28), and the refrigerating machine oil in the heat exchanger (12, 13, 31, 41, 51) is easily discharged to the outside. I tried to be.

  Specifically, the first invention is provided in a refrigerant circuit (10) for performing a vapor compression refrigeration cycle, and the refrigerant is placed in a flow path (26, 26 ', 36, 46, 56) formed therein. Assuming a heat exchanger that flows and functions as at least an evaporator, the flow path (26, 26 ', 36, 46, 56) has at least an intermediate portion between the inlet (27) and the outlet (28). It is assumed that it is formed so as to flow downward.

  With this configuration, at least the inlet (27) and the outlet (27) of the flow paths (26, 26 ', 36, 46, 56) in the heat exchanger (12, 13, 31, 41, 51) functioning as an evaporator. 28) Since the refrigerant flows downward in the middle part with the refrigerant, even if the refrigeration oil is separated in the middle part where most of the refrigerant is vaporized, the refrigerant oil is carried downward by the refrigerant flow in addition to its own weight. It is. If it does so, it can prevent that refrigeration oil adheres to the said intermediate part, and it remains in a heat exchanger. In addition, since the vaporized refrigerant has a relatively high flow rate, the refrigerating machine oil is transported to the outside of the heat exchanger by the vaporized refrigerant on the outlet side from the intermediate portion where most of the refrigerant vaporizes in the flow path. .

  The flow path (26, 26 ', 56) is formed so that the refrigerant flows downward in a range of more than half of the outlet (28) side (second invention). In this way, even when the refrigerant is vaporized, the refrigerating machine oil separated from the refrigerant flows toward the outlet (28) by its own weight, and the outlet (28) is also vaporized by the flow of the refrigerant having a relatively large flow velocity. Carried to the side. Therefore, it is possible to reliably prevent the refrigerating machine oil from remaining in the heat exchanger (12, 13, 51).

  In the above configuration, the flow path (26, 26 ′, 36, 46, 56) is formed such that the outlet (28) is positioned below the inlet (27) (third invention). By doing so, the refrigerating machine oil in the heat exchanger (12, 13, 31, 41, 51) moves more reliably to the outlet (28) side due to the height difference between the inlet (27) and the outlet (28). Therefore, it is possible to more reliably prevent the refrigeration oil from remaining in the heat exchanger (12, 13, 31, 41, 51).

  Further, the channel (26 ′, 56) is preferably formed such that the outlet (28) is located at the lower end of the channel (26 ′, 56) (fourth invention). Thus, by providing the refrigerant outlet (28) of the heat exchanger (12, 13, 51) at the lower end of the flow path (26 ', 56), the refrigeration oil is more reliably supplied to the heat exchanger (12, 13). , 51) can be discharged to the outside, and the refrigerating machine oil can be further reliably prevented from remaining in the heat exchanger (12, 13, 51).

  A fifth invention is directed to a refrigeration apparatus including a refrigerant circuit (10) for performing a vapor compression refrigeration cycle, and the refrigerant circuit (10) is a heat exchanger according to any one of claims 1 to 4. (12, 13, 31, 41, 51) and a switching mechanism (15) for switching the circulation direction of the refrigerant so that the heat exchanger (12, 13, 31, 41, 51) functions as a gas cooler or an evaporator. And at least an inlet (27) and an outlet (28) of the flow paths (26, 26 ', 36, 46, 56) in the heat exchanger (12, 13, 31, 41, 51) It is assumed that the intermediate portion is configured such that the refrigerant always flows downward even when the refrigerant circulation direction is switched by the switching mechanism (15).

  With this configuration, in the configuration in which the heat exchanger (12, 13, 31, 41, 51) functions as a gas cooler or an evaporator by switching the refrigerant circulation direction in the refrigerant circuit (10), the heat exchanger (12 , 13, 31, 41, 51) of the flow path (26, 26 ', 36, 46, 56), the refrigerant always flows downward at least in the intermediate portion between the inlet (27) and the outlet (28). Therefore, the separated refrigerating machine oil is carried downward by its own weight and the flow of the refrigerant. Thereby, even when the circulation direction of the refrigerant in the refrigerant circuit (10) is switched, it is possible to prevent the refrigerating machine oil from adhering to the intermediate portion where most of the refrigerant is vaporized. Therefore, it is possible to reliably prevent the refrigeration oil from adhering to the wall surface of the flow path (26, 26 ', 36, 46, 56) in the heat exchanger (12, 13, 31, 41, 51). Can do.

  The refrigerant circuit (10) always has a constant direction with respect to the heat exchanger (12, 13, 31, 41, 51) even if the refrigerant circulation direction is switched by the switching mechanism (15). It consists of four on-off valves (63, 64, 65, 66) between the inlet (27) and outlet (28) of the heat exchanger (12, 13, 31, 41, 51) so that the refrigerant flows. It is assumed that a bridge circuit (60) is provided (sixth invention).

  Accordingly, even if the refrigerant circulation direction is switched by the switching mechanism (15), the refrigerant always flows in a constant direction with respect to the heat exchanger (12, 13, 31, 41, 51). The configuration of the invention can be realized.

  As described above, in the heat exchanger (12, 13, 31, 41, 51) according to the first aspect of the invention, at least at the intermediate portion between the inlet (279 and outlet (28), the flow path ( 26, 26 ', 36, 46, 56) is formed, the refrigerating machine oil separated at the intermediate portion where most of the refrigerant evaporates in the evaporator moves downward not only by its own weight but also by the flow of the refrigerant. Thereby, it is possible to prevent the refrigeration oil from adhering to the inner wall of the flow passage of the portion and remaining in the heat exchanger, and it is possible to prevent a decrease in heat transfer performance due to the refrigeration oil.

  In the second invention, the flow path (26, 26 ', 56) is formed so that the refrigerant flows downward in a range of more than half of the outlet (28) side. Thus, the refrigerating machine oil can be reliably moved downward and discharged from the outlet, and the refrigerating machine oil can be reliably prevented from remaining in the heat exchanger (12, 13, 51).

  In the third invention, the flow path (26, 26 ', 36, 46, 56) is formed so that the outlet (28) is positioned below the inlet (27), so that the refrigerant is The difference in height between the inlet (27) and outlet (28) makes it easier to flow to the outlet (28) side, ensuring that the refrigerating machine oil remains in the heat exchanger (12,13,31,41,51). Can be prevented. In particular, as in the fourth invention, by positioning the outlet (28) at the lower end of the flow path (26 ', 56), the refrigerating machine oil is further prevented from remaining in the heat exchanger (12, 13, 51). It can be surely prevented.

  In the refrigeration apparatus (1) according to the fifth invention, the switching mechanism (15) switches the circulation direction of the refrigerant in the refrigerant circuit (10), so that any one of the first to fifth heat exchangers (12 , 13, 31, 41, 51) is configured to function as a gas cooler or an evaporator, at least in the middle portion between the inlet (27) and the outlet (28), the refrigerant always flows downward. Therefore, it is possible to reliably prevent the refrigerating machine oil from remaining in the heat exchanger (12, 13, 31, 41, 51) of the refrigeration apparatus (1) that can be switched between the cooling operation and the heating operation.

  In the sixth invention, since the bridge circuit (60) by the on-off valve (63, 64, 65, 66) is provided between the entrance and exit of the heat exchanger (12, 13, 31, 41, 51), the heat exchanger The refrigerant can always flow in a certain direction with respect to the exchanger (12, 13, 31, 41, 51), and the configuration of the fifth aspect of the invention can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature and is not intended to limit the present invention, its application, or its use.

Embodiment 1
The heat exchanger (12, 13) according to Embodiment 1 of the present invention is applied to a refrigeration apparatus (1) that performs a vapor compression refrigeration cycle. The refrigeration apparatus of Embodiment 1 constitutes an air conditioner (1) that switches between indoor cooling and heating.

−Configuration−
<Refrigerant circuit>
As shown in FIG. 1, the air conditioner (1) includes a refrigerant circuit (10) filled with carbon dioxide as a refrigerant. In this air conditioner (1), polyalkylene glycol (PAG), which is a polar oil, is used as a lubricating oil (refrigerating machine oil) for lubricating each sliding portion of the compressor (11). Yes. And this PAG flows out into a refrigerant circuit (10) with the refrigerant discharged from the compressor (11). Therefore, in the refrigerant circuit (10), carbon dioxide as the refrigerant and PAG as the refrigerating machine oil circulate. In the refrigerant circuit (10), a refrigeration cycle (so-called supercritical cycle) for compressing carbon dioxide to a critical pressure or higher is performed.

  The refrigerant circuit (10) is provided with a compressor (11), an outdoor heat exchanger (12), an indoor heat exchanger (13), and an expansion valve (14).

  The compressor (11) is constituted by, for example, a scroll type compressor. The compressor (11) includes a discharge pipe (11a) for letting out the discharge refrigerant from the compressor (11), and a suction pipe (11b) for letting the suction refrigerant into the compressor (11). Is connected.

  The outdoor heat exchanger (12) is disposed in the outdoor space. In the outdoor heat exchanger (12), heat is exchanged between the refrigerant flowing inside and the outdoor air. On the other hand, the indoor heat exchanger (13) is disposed in the indoor space. In the indoor heat exchanger (13), heat is exchanged between the refrigerant flowing in the indoor heat exchanger and the room air. The outdoor heat exchanger (12) and the indoor heat exchanger (13) are heat exchangers according to the present invention, and constitute a cross fin type heat exchanger as will be described later.

  The expansion valve (14) is provided between the outdoor heat exchanger (12) and the indoor heat exchanger (13). This expansion valve (14) is comprised by the electronic expansion valve, for example.

  The refrigerant circuit (10) is provided with a four-way switching valve (15). The four-way switching valve (15) has four ports from first to fourth, the first port is connected to the outdoor heat exchanger (12), and the second port is the suction of the compressor (11). The third port is connected to the discharge side of the compressor (11), and the fourth port is connected to the indoor heat exchanger (13). The four-way switching valve (15) communicates the first port with the third port and simultaneously communicates the second port with the fourth port (solid line in FIG. 1), It is possible to switch to the second state (the state of the broken line in FIG. 1) in which the first port and the second port are communicated with each other, and at the same time the third port and the fourth port are communicated.

<Heat exchanger>
As shown in FIGS. 2 and 3, each heat exchanger (12, 13) includes a plurality of fins (21, 21,...) And a heat transfer tube (22). The plurality of fins (21, 21,...) Are aluminum plate members and are formed in a rectangular shape. The fins (21) are arranged in parallel with each other at a predetermined interval.

  The heat transfer tube (22) is composed of a copper tube, and a plurality of straight tube portions (22a, 22a,...) And a curved portion (22b, 22b,. ...). Each straight pipe portion (22a) extends straight in the arrangement direction of the fins (21) and penetrates the fins (21). The curved portion (22b, 22b,...) Is attached to the front row and the last row fins (21, 21) among the plurality of fins (21, 21,...). 22a and 22a) are curved so as to connect the ends thereof.

  As schematically shown in FIG. 4, when each of the heat exchangers (12, 13) functions as an evaporator, the refrigerant flows downward in the heat transfer tube (22) as a whole. And the outlet (28) is located below the inlet (27). That is, in each of the heat exchangers (12, 13), the refrigerant flowing in from the inlet (27) flows through the straight pipe portion (22a), and then passes through the curved portion (22b). The flow path (26) of the refrigerant by the plurality of straight pipe parts (22a, 22a,...) And the curved parts (22b, 22b,...) So as to flow through the pipe part (22a) and be discharged from the outlet (28). Is configured.

  Thereby, the refrigerating machine oil moves in the heat exchangers (12, 13) to the outlet (28) side due to its own weight and the flow of the refrigerant, and remains in the heat exchangers (12, 13). Can be prevented.

  In FIG. 4, the heat exchangers (12, 13) are formed with flow paths (26) so that the refrigerant flows almost directly under one of the curved portions (22 b, 22 b,...). Not limited to this, as shown in FIG. 5, the flow path (26 ′) may be formed so that the refrigerant flows obliquely downward in both curved portions (22b, 22b,...).

-Driving action-
Next, the operation of the air conditioner (1) according to Embodiment 1 will be described. In the refrigerant circuit (10) of the air conditioner (1), the refrigerant circulation direction is switched according to the setting of the four-way switching valve (15). Specifically, in the cooling operation, the four-way switching valve (15) is in a state indicated by a solid line in FIG. As a result, in the cooling operation, a refrigeration cycle is performed in which the outdoor heat exchanger (12) serves as a gas cooler (heat radiator) and the indoor heat exchanger (13) serves as an evaporator. On the other hand, in the heating operation, the four-way selector valve (15) is in a state indicated by a broken line in FIG. As a result, in the heating operation, a refrigeration cycle is performed in which the outdoor heat exchanger (12) serves as an evaporator and the indoor heat exchanger (13) serves as a gas cooler. Hereinafter, the cooling operation will be described as an example of the operation of the air conditioner (1).

  In the refrigerant circuit (10) shown in FIG. 1, the refrigerant compressed to the critical pressure or higher by the compressor (11) is discharged from the discharge pipe (11a). In addition, from this compressor (11), the oil utilized for lubrication of each sliding part is discharged with a high pressure refrigerant | coolant. Thereafter, the refrigerant flows through the outdoor heat exchanger (12). In the outdoor heat exchanger (12), the high-pressure refrigerant radiates heat to the outdoor air, and the high-pressure refrigerant after radiating heat in the outdoor heat exchanger (12) is decompressed when passing through the expansion valve (14), It becomes a low-pressure refrigerant. Thereafter, the refrigerant flows through the indoor heat exchanger (13), and the refrigerant absorbs heat from the indoor air and evaporates. As a result, the room is cooled. The refrigerant evaporated in the indoor heat exchanger (13) flows through the suction pipe (11b), is sucked into the compressor (11), and is compressed again.

  By the way, in the operation operation such as the cooling operation described above, when the refrigerant flows through the outdoor heat exchanger (12) or the indoor heat exchanger (13), the oil that cannot be dissolved in the refrigerant is separated from the refrigerant. It may cover the inner wall of the heat transfer tube (22). For this reason, in the conventional heat exchanger, the oil film was formed in the whole area of the inner peripheral wall of a heat exchanger tube, and the problem that the heat transfer performance of a refrigerant | coolant and air fell occurred. In particular, when carbon dioxide is used as the refrigerant and PAG is used as the refrigerating machine oil as in the present embodiment, since the compatibility of the PAG with carbon dioxide is low, the refrigerant and the oil are easily separated, and the oil film as described above is formed. Easy to form. As a result, there is a problem that the heat transfer performance of each heat exchanger is remarkably lowered, and the cooling capacity and heating capacity of the air conditioner are also lowered.

  In general, when a heat exchanger is used as a gas cooler, the refrigerant flows from the top to the bottom, while when used as an evaporator, the refrigerant flows from the bottom to the top so that the refrigerant flows through the heat exchanger. In the case of an evaporator in which the refrigerant evaporates in the middle and the refrigerating machine oil is easily separated, a large amount of refrigerating machine oil adheres to the inner peripheral wall of the heat transfer tube. Thus, the problems as described above are likely to become obvious.

  Therefore, in the heat exchanger (12, 13) of the present embodiment, when used as an evaporator, the refrigerant is allowed to flow downward as described above so that the refrigerating machine oil separated from the refrigerant is not only its own weight. It is also moved downward by the flow of the refrigerant to prevent the heat transfer tube from adhering to the inner peripheral wall. Thereby, the refrigeration oil in the heat exchanger (12, 13) flows out from the outlet (28) together with the refrigerant, and is sucked into the compressor (11).

  Here, in general, when the heat exchanger functions as an evaporator, most of the refrigerant is vaporized in the middle part of the flow path in the heat exchanger, so the refrigerant and the refrigerating machine oil are separated in the middle part. Thus, the refrigeration oil easily adheres to the part. Therefore, as described above, if the flow path (26) is formed so that the refrigerant flows downward at least in the intermediate portion, the separated refrigerating machine oil moves downward due to the flow of the refrigerant in addition to its own weight. It is possible to reliably prevent the refrigeration oil from adhering to the inner peripheral wall of the heat transfer tube at the intermediate portion.

  In addition, even if the circulation direction of the refrigerant is reversed by switching the operation, the refrigerant circuit (the second embodiment described later) (so that the refrigerant always flows in a constant direction with respect to the heat exchanger (12, 13)). By configuring 10), not only a heat exchanger that functions as an evaporator, but also a heat exchanger that functions as a gas cooler, it is possible to reliably prevent refrigeration oil from remaining inside. It is possible to reliably prevent a decrease in the heat transfer performance.

-Effect of Embodiment 1-
As described above, in the first embodiment, in the heat exchangers (12, 13) functioning as an evaporator, the refrigerant flow paths (26, 26 ′) formed therein are arranged so that the refrigerant flows downward as a whole. Since it is formed, the refrigerating machine oil separated from the gas refrigerant is carried downward by the refrigerant flow in addition to its own weight. Thereby, it is possible to prevent the refrigeration oil from adhering to the inner peripheral wall of the flow path (26, 26 ') of the heat exchanger (12, 13), and the refrigeration oil in the heat exchanger (12, 13). Can be prevented from remaining. Therefore, it is possible to prevent the heat transfer performance of the heat exchanger (12, 13) from being significantly lowered by the refrigerating machine oil and the cooling capacity and heating capacity of the air conditioner (1) from being lowered.

  In particular, in the heat exchanger (12, 13), the refrigerant flows downward in an intermediate portion between the outlet (28) and the inlet (27) where most of the refrigerant evaporates in the internal flow path (26, 26 '). Since it is comprised so that it may flow toward, it can prevent reliably that refrigeration oil adheres to this intermediate part.

  Further, since the outlet (28) of the flow path (26, 26 ') in the heat exchanger (12, 13) is positioned below the inlet (27), the heat exchanger is caused by the height difference. The refrigerating machine oil in (12, 13) moves more reliably downward and is more reliably discharged from the outlet (28) to the outside of the heat exchanger (12, 13). Therefore, it is possible to more reliably prevent the refrigeration oil from remaining in the heat exchanger (12, 13). In particular, as shown in FIG. 5, if the outlet (28) of the flow path (26 ′) of the heat exchanger (12, 13) is positioned at the lower end of the flow path (26 ′), the refrigerating machine oil is added to the It becomes possible to discharge more reliably out of the heat exchanger (12, 13) from the outlet (28).

-Modification 1 of Embodiment 1-
The heat exchanger (31) according to the first modified example is configured such that the refrigerant flows upward in the straight pipe portion of the two stages of the heat transfer pipe on the outlet (28) side (lower side). Different from the first embodiment.

  Specifically, as shown in FIG. 6, in the heat exchanger (31), the third straight pipe portion (23) from the bottom and the lowermost straight pipe portion (25) are connected, The lowermost straight pipe portion (25) is connected to the second straight pipe portion (24) from the bottom. As a result, the refrigerant flowing in the heat exchanger (31) flows downward from the bottom to the third straight pipe section (23), and then flows to the bottom straight pipe section (25). , Flows from the bottom to the second straight section (24). That is, in the heat exchanger (31), the flow path (36) is configured so that the refrigerant flows upward in the last two stages on the outlet (28) side.

  As described above, even if the refrigerant flows upward in the last two straight pipe sections (24, 25) on the outlet (28) side, heat exchange is performed until the last two stages. Since the flow path (36) in the cooler (31) has a sufficient height difference, the refrigeration oil is discharged from the outlet (28) together with the refrigerant to the outside due to the height difference, and the heat exchanger (31) Hardly remains.

-Modification 2 of Embodiment 1
The heat exchanger (41) according to the second modification differs from the first embodiment in that the refrigerant flows upward near the inlet (27) and the outlet (28).

  Specifically, as shown in FIG. 7, in the refrigerant flow path (46) in the heat exchanger (41), an intermediate portion between the inlet (27) and the outlet (28) (in the example shown, the inlet The portion between (27) and the second stage from the outlet (28) to the second stage) is configured so that the refrigerant flows downward, and the inlet (27) and outlet (28) side In the vicinity (in the example of the figure, from the inlet (27) to the second stage, from the outlet (28) to the second stage), the refrigerant is configured to flow upward.

  As described above, when the heat exchanger functions as an evaporator, most of the refrigerant is vaporized at an intermediate portion of the flow path in the heat exchanger, and the refrigerating machine oil separated from the refrigerant is likely to adhere to the intermediate portion. As described above, by forming the flow path (46) so that the refrigerant flows downward in the intermediate portion, the separated refrigerating machine oil moves downward due to the flow of the refrigerant in addition to its own weight, Refrigerating machine oil can be prevented from adhering to the inner peripheral wall of the heat transfer tube in the intermediate portion.

  The refrigerating machine oil moved downward from the intermediate portion is discharged from the outlet (28) to the outside of the heat exchanger by the gas refrigerant having a high flow velocity near the outlet (28).

Modification 3- of Embodiment 1
In the heat exchanger (51) according to the modified example 3, the refrigerant flows upward on the inlet (27) side of the internal flow path (56), and the refrigerant flows in the range of more than half of the outlet (28) side. The point which is comprised so that it may flow toward the bottom differs from the said Embodiment 1. FIG.

  Specifically, as shown in FIG. 8, in the heat exchanger (51), the refrigerant flows upward in a half of the flow path (56) formed inside the inlet (27) side. On the other hand, in the half on the outlet (28) side, the refrigerant flows downward. That is, as shown in FIG. 8 above, for example, when the heat transfer tube is constituted by a six-stage straight pipe portion, the refrigerant flows upward in the three stages on the inlet (27) side, while on the outlet (28) side. In the third stage, the refrigerant is configured to flow downward.

  In the example of FIG. 8 described above, the entire flow path (56) is divided into a half of a range in which the refrigerant flows upward and a range in which the refrigerant flows downward. You may form a flow path so that a refrigerant | coolant may flow below in the range of half or more. Further, in FIG. 8, the outlet (28) of the flow path (56) of the heat exchanger (51) is provided below the inlet (27). May also be provided below.

  As described above, when the heat exchanger functions as an evaporator, most of the refrigerant flowing inside is vaporized in the middle part of the flow path, so that the refrigerant is directed downward on the outlet (28) side from the vaporized part. By flowing, the separated refrigerating machine oil moves downward by the fast flow of the gas refrigerant in addition to its own weight, and is discharged from the outlet (28) to the outside.

  Therefore, as described above, by forming the flow path (56) so that the refrigerant flows downward in the region of more than half of the outlet (28) side, the refrigerating machine oil remains in the heat exchanger. It can prevent reliably and can prevent that the heat-transfer performance of this heat exchanger falls with refrigeration oil.

<< Embodiment 2 >>
The heat exchanger (12, 13) according to Embodiment 2 of the present invention has the same configuration as that of Embodiment 1 described above, but is based on an electromagnetic valve (63, 64, 65, 66) between its entrance and exit. The difference from the first embodiment is that a bridge circuit (60) is provided. Therefore, the same reference numerals are given to the same parts, and only different parts will be described below.

  Specifically, as shown in FIG. 9, electromagnetic valves (63, 64) are provided on the inlet (27) side and outlet (28) side of the flow path (26) of the heat exchanger (12, 13), respectively. In addition, the upstream side of one solenoid valve (63, 64) and the downstream side of the other solenoid valve (63, 64) are connected by a communication passage (61, 62) and also on the passage (61, 62). Provide solenoid valves (65, 66) for each. Thereby, a bridge circuit (60) is constituted by these four solenoid valves (63, 64, 65, 66).

  For example, when the heat exchanger (12, 13) functions as a gas cooler (when the refrigerant flows in the direction of the solid line arrow in FIG. 9), the electromagnetic valve (63, 64) is opened. Thus, the refrigerant is caused to flow from top to bottom with respect to the heat exchanger (12, 13). On the other hand, when the heat exchanger (12, 13) functions as an evaporator (when the refrigerant flows in the direction of the broken line arrow in FIG. 9), by opening the electromagnetic valve (65, 66), The refrigerant is configured to flow from top to bottom with respect to the heat exchanger (12, 13).

  That is, by providing the bridge circuit (60) as described above, even if the refrigerant circulation direction in the refrigerant circuit (10) changes, the heat exchanger (12, 13) is always in the same direction (downward) ). Therefore, not only when the heat exchanger (12, 13) functions as a gas cooler but also when it functions as an evaporator, the refrigerating machine oil moves downward due to the flow of the refrigerant in addition to its own weight. The refrigeration oil can be prevented from adhering to the inner peripheral wall of the heat transfer tube (22) of the heat exchanger (12, 13) and remaining in the heat exchanger (12, 13).

  The configuration of the heat exchanger (12, 13) is not limited to the same as that of the first embodiment, and may be a configuration as in each modification of the first embodiment.

-Effect of Embodiment 2-
As described above, according to this embodiment, the entrance / exit of the heat exchanger (12, 13) so that the refrigerant always flows in the same direction with respect to the heat exchanger (12, 13) functioning as a gas cooler or an evaporator. Since the bridge circuit (60) is formed using four solenoid valves (63, 64, 65, 66), the heat exchangers (12, 13) function as gas coolers and evaporators, respectively, even when the operating state is switched. ) Can be reliably prevented from remaining in the refrigerating machine oil, and the heat transfer characteristics of the heat exchangers (12, 13) can be prevented from being deteriorated by the refrigerating machine oil.

<< Other Embodiments >>
About the said embodiment, it is good also as the following structures.

  In the above embodiments, the four-way switching valve (15) is used to switch between the heating operation and the cooling operation by switching the refrigerant circulation direction. However, the four-way switching valve (15) is not provided and the cooling operation is performed. It may be a cooling only machine that performs only operation.

  In each of the above embodiments, the heat exchanger (12, 13) according to the present invention is applied to a refrigerating apparatus that uses carbon dioxide as a refrigerant and PAG as a refrigerating machine oil. Alternatively, the heat exchanger (12, 13) may be applied to a refrigeration apparatus that uses refrigeration oil. Specifically, examples of the refrigerant include R134a, R410a, R407c, and R32, and examples of the refrigerating machine oil include poly-α-olefin, P06, and fluorine-based oil.

  As described above, when the heat exchanger functions as an evaporator, a flow path is formed so that the refrigerant flows downward at least at an intermediate portion between the inlet and the outlet, thereby freezing the heat exchanger. Since the machine oil can be prevented from remaining, the present invention is particularly useful for a heat exchanger used in a refrigeration apparatus that performs a refrigeration cycle.

It is a piping system diagram which shows schematic structure of the refrigerant circuit of the freezing apparatus which concerns on Embodiment 1 of this invention. It is a perspective view which shows schematic structure of a heat exchanger. It is a front view which shows schematic structure of a heat exchanger. It is a schematic diagram which shows the flow path in a heat exchanger. FIG. 5 is a view corresponding to FIG. 4 when the refrigerant flows obliquely downward. FIG. 6 is a view corresponding to FIG. 4 of a heat exchanger according to Modification 1. FIG. 6 is a view corresponding to FIG. 4 of a heat exchanger according to Modification 2. FIG. 6 is a view corresponding to FIG. 4 of a heat exchanger according to Modification 3. 6 is a piping system diagram showing a part of a refrigerant circuit according to Embodiment 2. FIG. It is a schematic diagram which shows the flow of the refrigerant | coolant in the conventional heat exchanger.

Explanation of symbols

1 Air conditioner (refrigeration equipment)
10 Refrigerant circuit
12 Indoor heat exchanger (heat exchanger)
13 Outdoor heat exchanger (heat exchanger)
15 Four-way selector valve (switching mechanism)
22 Heat transfer tube
26,26 ', 36,46,56 Channel
27 Entrance
28 Exit
31,41,51 heat exchanger
60 bridge circuit
63, 64, 65, 66 Solenoid valve (open / close valve)

Claims (6)

Heat exchange that is provided in the refrigerant circuit (10) that performs the vapor compression refrigeration cycle, and that at least functions as an evaporator through the flow of refrigerant in the flow paths (26, 26 ', 36, 46, 56) formed inside A vessel,
The flow path (26, 26 ', 36, 46, 56) is formed such that the refrigerant flows downward at least at an intermediate portion between the inlet (27) and the outlet (28). Heat exchanger. In claim 1,
The flow path (26, 26 ', 56) is formed so that the refrigerant flows downward in a range of more than half of the outlet (28) side. In claim 1 or 2,
The flow path (26, 26 ', 36, 46, 56) is a heat exchanger characterized in that the outlet (28) is formed below the inlet (27). In claim 3,
The flow channel (26 ', 56) is formed so that the outlet (28) is positioned at the lower end of the flow channel (26', 56). A refrigeration apparatus comprising a refrigerant circuit (10) for performing a vapor compression refrigeration cycle,
The refrigerant circuit (10)
A heat exchanger (12, 13, 31, 41, 51) according to any one of claims 1 to 4;
A switching mechanism (15) that switches the circulation direction of the refrigerant so that the heat exchanger (12, 13, 31, 41, 51) functions as a gas cooler or an evaporator,
Among the flow paths (26, 26 ', 36, 46, 56) in the heat exchanger (12, 13, 31, 41, 51), at least in the intermediate part between the inlet (27) and the outlet (28), A refrigeration apparatus characterized in that the refrigerant always flows downward even when the refrigerant circulation direction is switched by the switching mechanism (15). In claim 5,
Even if the refrigerant circulation direction is switched by the switching mechanism (15), the refrigerant circuit (10) always has a refrigerant in a constant direction with respect to the heat exchanger (12, 13, 31, 41, 51). A bridge circuit comprising four on-off valves (63, 64, 65, 66) between the inlet (27) and the outlet (28) of the heat exchanger (12, 13, 31, 41, 51) so as to flow (60) The freezing apparatus characterized by the above-mentioned.

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