JP2007333319A - Heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the heat exchange efficiency of a gas cooler by preventing a refrigerant on the inlet side of the gas cooler and a refrigerant on the outlet side of the gas cooler from exchanging heat with each other. <P>SOLUTION: Heat exchangers 1, 1a functioning in a refrigerating cycle using a supercritical refrigerant comprise heat transfer tubes 2, 2a and a plurality of heat transfer fins 3, 3a. The heat transfer tubes allow the supercritical refrigerant to flow through. The plurality of heat transfer fins are connected to the heat transfer tubes to assist the heat exchange between a first fluid and the supercritical refrigerant in the heat transfer tubes. The plurality of heat transfer fins are arranged separated with respect to the flow direction R1 of the supercritical refrigerant. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat exchanger that functions in a refrigeration cycle using a supercritical refrigerant.

Conventionally, a heat exchanger that functions in a refrigeration cycle using a supercritical refrigerant such as a CO 2 refrigerant is, for example, a cross-fin type heat exchanger. In such a cross fin type heat exchanger, the heat exchange area is increased by turning one heat transfer tube through which the refrigerant flows and increasing the number of portions that come into contact with the fins. High efficiency is achieved (see Patent Document 1).
Japanese Patent Laid-Open No. 2004-77021

  However, in a heat exchanger (gas cooler) that uses a supercritical refrigerant such as a CO2 refrigerant, the supercritical refrigerant operates in the supercritical region in the entire heat exchanger and does not condense and operates with a sensible heat change. To do. Therefore, when the heat exchanger functions as a gas cooler, the refrigerant temperature changes greatly, and a large temperature difference occurs between the inlet side and the outlet side of the refrigerant in the heat exchanger. That is, a large temperature difference occurs between the upstream side and the downstream side of the heat transfer tube in the refrigerant flow direction. In the technique of Patent Document 1, since the upstream side and the downstream side of the heat transfer tube in the refrigerant flow direction are connected by the heat transfer fin, heat exchange is performed between the upstream side and the downstream side of the heat transfer tube in the heat transfer fin. Doing so increases the amount of heat loss.

  An object of the present invention is to prevent heat exchange between the refrigerant on the inlet side of the gas cooler and the refrigerant on the outlet side of the gas cooler, thereby improving the heat exchange efficiency of the gas cooler.

  A heat exchanger according to a first invention is a heat exchanger that functions in a refrigeration cycle using a supercritical refrigerant, and includes a heat transfer tube and a plurality of heat transfer fins. The heat transfer tube can circulate a supercritical refrigerant. The plurality of heat transfer fins are connected to the heat transfer tube and facilitate heat exchange between the first fluid and the supercritical refrigerant in the heat transfer tube. The plurality of heat transfer fins are arranged separately from each other in the supercritical refrigerant flow direction.

  This heat exchanger is a gas cooler under supercritical conditions and operates in the supercritical region. In such a heat exchanger, the refrigerant does not condense in the entire heat exchanger and operates with a sensible heat change. Therefore, when the heat exchanger functions as a gas cooler, the refrigerant temperature changes greatly, and a large temperature difference occurs between the upstream side and the downstream side of the heat transfer tube in the refrigerant flow direction.

  In the present invention, the heat transfer fins are separated from the refrigerant flow direction so that the upstream side and the downstream side of the heat transfer tube in the refrigerant flow direction of the heat exchanger are not connected by the heat transfer fins. Thereby, it can prevent that the upstream and downstream of a heat exchanger tube perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  A heat exchanger according to a second aspect of the present invention is the heat exchanger according to the first aspect of the present invention, wherein the heat transfer tube is spirally wound a plurality of times with respect to the substantially cylindrical first space.

  In this heat exchanger, the heat transfer tube is spirally wound a plurality of times. And it forms so that the heat-transfer fin of one heat-transfer tube may not contact the heat-transfer fin of another one-roll heat-transfer tube adjacent.

  Thereby, it can prevent that the upstream and downstream of a heat exchanger tube perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  A heat exchanger according to a third aspect is the heat exchanger according to the second aspect, wherein the supercritical refrigerant flows in a direction from the first plane of the first space to the second plane while drawing a spiral trajectory. The first fluid flows in the direction of the first plane from the second plane through the first fluid channel outside the heat transfer tube.

  In this heat exchanger, the flow direction of the refrigerant faces the flow direction of the first fluid. Therefore, a large temperature difference between the refrigerant and the first fluid can be maintained in the entire heat exchanger, and the efficiency of the heat exchanger can be increased.

  A heat exchanger according to a fourth aspect is the heat exchanger according to the first aspect, wherein the heat transfer tube has a plurality of straight tube portions and at least one or more bent tube portions. The plurality of straight pipe portions are adjacent to each other substantially parallel to each other and are spaced apart from each other.

  In this heat exchanger, the heat transfer tubes are turned, and the straight tube portions of the heat transfer tubes are adjacent to each other in parallel and are spaced apart from each other. And the heat-transfer fin connected to one straight pipe part is arrange | positioned so that it may not contact the heat-transfer fin connected to another adjacent straight pipe part.

  Thereby, it can prevent that the upstream and downstream of a heat exchanger tube perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  A heat exchanger according to a fifth aspect of the present invention is the heat exchanger according to any one of the first to fourth aspects of the present invention, wherein the heat transfer fins are plate-shaped fins and are radially outward from the outer peripheral surface of the heat transfer tube. It extends to.

  The heat transfer fin is connected to the heat transfer tube at one end in the form of a plate, and is connected at one place. That is, the heat transfer fin is formed in the heat transfer tube so as not to contact the upstream side or the downstream side of the connection location to which the heat transfer fin is connected.

  Therefore, it is possible to prevent heat exchange between the upstream side and the downstream side of the heat transfer tube, and it is possible to reduce a large heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  A heat exchanger according to a sixth aspect of the present invention is the heat exchanger according to any one of the first to fourth aspects of the present invention, wherein the heat transfer fins are needle-like fins and are radially outward from the outer peripheral surface of the heat transfer tube. It extends to.

  This heat transfer fin is connected to the heat transfer tube at one end in a needle shape, and is connected at one place. That is, the heat transfer fin is formed in the heat transfer tube so as not to contact the upstream side or the downstream side of the connection location to which the heat transfer fin is connected.

  Therefore, it is possible to prevent heat exchange between the upstream side and the downstream side of the heat transfer tube, and it is possible to reduce a large heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  A heat exchanger according to a seventh aspect of the present invention is the heat exchanger according to any one of the first to fourth aspects of the present invention, wherein the heat transfer fins are substantially U-shaped fins, and both ends thereof are the outer periphery of the heat transfer tube. Connected to the surface.

  In this heat exchanger, the heat transfer fins are substantially U-shaped fins, and both ends thereof are connected to the outer peripheral surface of the heat transfer tube. That is, the heat transfer fin is not in contact with the upstream side or the downstream side of the connection portion to which the heat transfer fin is connected in the heat transfer tube.

  Therefore, it is possible to prevent heat exchange between the upstream side and the downstream side of the heat transfer tube, and it is possible to reduce a large heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  In the heat exchanger according to the first aspect of the invention, the heat transfer fins are separated in the refrigerant flow direction so that the upstream side and the downstream side of the heat transfer tube in the refrigerant flow direction of the heat exchanger are not connected by the heat transfer fins. Yes. Thereby, it can prevent that the upstream and downstream of a heat exchanger tube perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  In the heat exchanger which concerns on 2nd invention, it can prevent that the upstream and downstream of a heat exchanger tube perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  In the heat exchanger according to the third aspect of the invention, the flow direction of the refrigerant faces the flow direction of the first fluid. Therefore, a large temperature difference between the refrigerant and the first fluid can be maintained in the entire heat exchanger, and the efficiency of the heat exchanger can be increased.

  In the heat exchanger according to the fourth aspect of the invention, it is possible to prevent heat exchange between the upstream side and the downstream side of the heat transfer tube, and to reduce a large heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  In the heat exchanger which concerns on 5th invention, it can prevent that the upstream and downstream of a heat exchanger tube perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  In the heat exchanger according to the sixth aspect of the present invention, it is possible to prevent heat exchange between the upstream side and the downstream side of the heat transfer tube and to reduce a large heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  In the heat exchanger which concerns on 7th invention, it can prevent that the upstream and downstream of a heat exchanger tube perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the heat exchanger can be improved.

  Hereinafter, an embodiment of a gas cooler 12 according to the present invention will be described based on the drawings.

<Supercritical refrigeration cycle>
FIG. 1 shows a refrigeration circuit 1 that uses CO2, which is a supercritical refrigerant, as a refrigerant. FIG. 2 shows a refrigeration cycle using a refrigeration circuit 1 under supercritical conditions by a ph diagram (Mollier diagram). The refrigeration circuit 1 includes a compressor 11, a gas cooler 12, an expansion valve 13, and an evaporator 14. A, B, C, and D in FIG. 2 represent refrigerant states corresponding to the respective points in FIG.

  In the refrigeration circuit 1, the refrigerant is compressed by the compressor 11 and becomes high temperature and pressure (A → B). At this time, CO2 which is a refrigerant changes from gas to a supercritical state. The “supercritical state” referred to here is a state of a substance at a temperature and pressure above the critical point K and is a state having both gas diffusibility and liquid solubility. The supercritical state is the state of the refrigerant in the region on the right side of the critical temperature isotherm Tk in FIG. 2 and above the critical pressure Pk. Note that when the refrigerant (substance) is in a supercritical state, there is no distinction between the gas phase and the liquid phase. The “gas phase” referred to here is the state of the refrigerant on the right side of the saturated vapor line Sv and in the region below the critical pressure Pk. Further, the “liquid phase” is a state of the refrigerant in a region on the left side of the saturated liquid line S1 and on the left side of the critical temperature isotherm Tk. And the refrigerant | coolant which was compressed by the compressor 11 and became the supercritical state of the high temperature / high pressure is radiated by the gas cooler 12, and becomes a high pressure refrigerant (B → C). At this time, since the refrigerant is in a supercritical state, it operates with a sensible heat change (temperature change) inside the gas cooler 12. The refrigerant that has dissipated heat in the gas cooler 12 expands when the expansion valve 13 is opened, and the pressure is reduced from P1 to P2 (C → D). The refrigerant decompressed by the expansion valve 13 absorbs heat in the evaporator 14, evaporates, and returns to the compressor 11 (D → A).

  The heat exchanger according to the present invention is the gas cooler 12 in FIG. 1, and changes the state of the refrigerant as B → C in FIG. The gas cooler 12 plays a role of a condenser in a refrigeration cycle using, for example, an HFC-based chlorofluorocarbon refrigerant. Since the gas cooler 12 uses CO2 that operates under supercritical conditions as a refrigerant, unlike the condenser, the refrigerant operates with a sensible heat change, and the refrigerant inlet 21 and the refrigerant into which the refrigerant flows. A large temperature difference occurs between the refrigerant outlet portion 22 from which the refrigerant flows out.

<Configuration of gas cooler>
FIG. 3 is a schematic view of the gas cooler 12 according to an embodiment of the present invention. The gas cooler 12 is one of devices incorporated in a refrigerant circuit such as an air conditioner or a heat pump water heater, and is a gas cooler that cools a supercritical refrigerant such as a CO 2 refrigerant. The gas cooler 12 is mainly composed of the heat transfer tubes 2 and the heat transfer fins 3.

  The heat transfer tube 2 has a spiral shape that is wound around the substantially cylindrical first space S1. And the supercritical refrigerant | coolant which was compressed by the compressor 11 and became high temperature / high pressure distribute | circulates the inside of the heat exchanger tube 2. FIG. This high-temperature and high-pressure supercritical refrigerant flows in from the refrigerant inlet 21 and flows out of the refrigerant outlet 22 and flows in the direction of the white arrow R1 shown in FIGS.

  The heat transfer fins 3 have a plate shape as shown in FIG. 4, and a plurality of the heat transfer fins 3 are radially connected so as to extend outward from the outer peripheral surface of the heat transfer tube 2. The heat transfer fins 3 release the heat of the high-temperature and high-pressure supercritical refrigerant flowing into the heat transfer tube 2 to the outside air outside the heat transfer tube 2.

  The gas cooler 12 further includes a first cylindrical pipe 4 and a second cylindrical pipe 5. The heat transfer tube 2 is spirally wound around the first cylindrical pipe 4 a plurality of times. The second cylindrical pipe 5 has a larger diameter than the first cylindrical pipe 4 and is formed so as to cover the outside of the heat transfer tube 2. In this way, a second space S2 through which external air flows is formed between the first cylindrical pipe 4 and the second cylindrical pipe 5. Here, both the first cylindrical pipe 4 and the second cylindrical pipe 5 are made of metal. The external air that has flowed into the second space S2 exchanges heat with the supercritical refrigerant flowing in the heat transfer tube 2, and cools the supercritical refrigerant in the heat transfer tube 2.

  In the gas cooler 12, the supercritical refrigerant flows in the heat transfer tube 2 from the first plane As1 to the second plane As2 in the first space S1 (see the arrow R1a in FIG. 3), and the external air is in the opposite direction. (See the white arrow A1 in FIGS. 3 and 4). Thus, in the gas cooler 12, the flow direction R1a of the supercritical refrigerant and the flow direction A1 of the external air face each other. For this reason, in the whole gas cooler 12, the temperature difference of a supercritical refrigerant | coolant and external air can be maintained large, and the high efficiency of the gas cooler 12 can be achieved.

<Features>
(1)
In the gas cooler 12, the heat transfer fins 3 are separated in the refrigerant flow direction so that the upstream side and the downstream side of the heat transfer tube 2 in the refrigerant flow direction are not connected by the heat transfer fins 3. Thereby, it can prevent that the upstream and downstream of the heat exchanger tube 2 perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency in the gas cooler 12 can be improved.

(2)
In this gas cooler 12, the heat transfer tube 2 is wound a plurality of times into a spiral shape. Further, in the gas cooler 12, the heat transfer fins 3 are plate-like fins, and extend radially outward from the outer peripheral surface of the heat transfer tube 2. The heat transfer fin 3 is connected to the heat transfer tube 2 at one end in the form of a plate, and the connection location is one location. That is, the heat transfer fin 3 is not in contact with the upstream side or the downstream side of the heat transfer tube 2 with respect to the connection portion to which the heat transfer fin 3 is connected.

  Thereby, it can prevent that the upstream and downstream of the heat exchanger tube 2 perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the gas cooler 12 can be improved. Furthermore, in the whole gas cooler 12, the temperature difference between the refrigerant and the first fluid can be maintained large, and the efficiency of the gas cooler 12 can be increased.

<Modification>
Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention.

(1)
In the said Example, although the heat exchanger tube 2 was wound in multiple turns and made into the spiral shape, the shape which turned not only this but the heat exchanger tube 2a in multiple times may be sufficient. FIG. 5 is a schematic view of the gas cooler 12a when the heat transfer tube 2a is turned a plurality of times. In this gas cooler 12, the heat transfer tube 2a has a plurality of straight tube portions 23a arranged substantially in parallel, and a curved tube portion 24a that alternately connects ends of the plurality of straight tube portions 23a. One refrigerant path is formed. And the heat transfer fin 3 connected to one straight pipe part 23a is arrange | positioned so that it may not contact the heat transfer fin 3 connected to another one straight pipe part 23a adjacent.

  Here, the high-temperature and high-pressure supercritical refrigerant flows in from the upper refrigerant inlet portion 21a, flows out from the lower refrigerant outlet portion 22a, and flows in the directions of white arrows R2 and R3 shown in FIG. Further, the external air flows in a direction perpendicular to the straight pipe portion 23a of the heat transfer tube 2a (the direction of the white arrow A2 shown in FIG. 5).

  Thereby, it can prevent that the upstream and downstream of the heat exchanger tube 2a perform heat exchange, and can reduce a big heat loss. For this reason, the heat exchange efficiency of the gas cooler 12 can be improved.

(2)
In the above embodiment, the heat transfer fins 3 are plate-like fins, but are not limited to this, and may be fins such as needles and rods. The heat transfer fin is connected to the heat transfer tube 2 at one end of a needle shape or a rod shape, and is connected at one place.

  Further, it may be a substantially U-shaped heat transfer fin 3a in which both ends are connected (see FIG. 6). The heat transfer fins 3a are connected at two locations on both ends thereof, but the two connection locations are relatively close because the shape is substantially U-shaped. That is, since the heat transfer fins 3a do not contact the upstream side or the downstream side of the connection location, the heat transfer fins 3a hardly exchange heat with the upstream side or the downstream side of the connection location. In this modification, only the shape of the heat transfer fin is different from that in the above embodiment, and the heat transfer tube 2, the refrigerant flow direction R1, and the external air flow direction A1 are all the same.

  Therefore, heat exchange between the upstream side and the downstream side of the heat transfer tube 2 can be prevented, and a large heat loss can be reduced. For this reason, the heat exchange efficiency of the gas cooler 12 can be improved.

(3)
In the said Example, although the 1st cylindrical pipe and the 2nd cylindrical pipe were metal, it may not be restricted to this but may be resin.

  The heat exchanger according to the present invention can improve the heat exchange efficiency of the heat exchanger, and is useful as a heat exchanger that functions in a refrigeration cycle under supercritical conditions.

The refrigeration circuit diagram using the supercritical refrigerant | coolant which concerns on one Embodiment of this invention. The ph diagram (Mollier diagram) of the refrigerating cycle using a supercritical refrigerant. The perspective view of a gas cooler. The enlarged view of the heat-transfer fin (plate shape) connected to a heat-transfer tube. The perspective view of the gas cooler which concerns on a modification (1). The enlarged view of the heat-transfer fin (substantially U shape) concerning a modification (2).

Explanation of symbols

2, 2a Heat transfer tubes 3, 3a Heat transfer fins 12, 12a Gas cooler (heat exchanger)
23a Straight pipe part (straight line part)
24a Curved pipe part (bending part)
S1 first space S2 second space (first fluid flow path)
As1 first plane As2 second plane

Claims (7)

A heat exchanger (1, 1a) that functions in a refrigeration cycle using a supercritical refrigerant,
A heat transfer tube (2, 2a) capable of circulating the supercritical refrigerant;
A plurality of heat transfer fins (3, 3a) that are connected to the heat transfer tubes and facilitate heat exchange between the supercritical refrigerant and the first fluid in the heat transfer tubes;
With
The plurality of heat transfer fins are arranged separately from each other with respect to the supercritical refrigerant flow direction (R1).
Heat exchanger (1, 1a). The heat transfer tube (2) is spirally wound a plurality of times with respect to the substantially cylindrical first space (S1).
The heat exchanger according to claim 1. The supercritical refrigerant flows in a direction from the first plane (As1) to the second plane (As2) of the first space while drawing a spiral orbit,
The first fluid flows through the first fluid flow path (S2) outside the heat transfer tube from the second plane toward the first plane.
The heat exchanger (1a) according to claim 2. The heat transfer tube has a plurality of straight tube portions (23a) and at least one bent tube portion (24a),
The plurality of straight pipe portions are adjacent to each other substantially in parallel, and are spaced apart from each other.
The heat exchanger (1a) according to claim 1. The heat transfer fin (3) is a plate-like fin, and extends radially outward from the outer peripheral surface of the heat transfer tube.
The heat exchanger (1, 1a) according to any one of claims 1 to 4. The heat transfer fin (3a) is a needle-like fin, and extends radially outward from the outer peripheral surface of the heat transfer tube.
The heat exchanger (1, 1a) according to any one of claims 1 to 4. The heat transfer fin (3a) is a substantially U-shaped fin, and both ends thereof are connected to the outer peripheral surface of the heat transfer tube.
The heat exchanger (1, 1a) according to any one of claims 1 to 4.

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