KR20020078806A - Heat exchanger - Google Patents

Abstract

PURPOSE: A heat exchanger is provided to have structure enduring high pressure for gas cooling and evaporation needed for using carbon dioxide as refrigerant. CONSTITUTION: A heat exchanger includes a first lower header tank(21) and a second lower header tank(22) having baffles(21a,22a) formed therein, respectively, to intercept flowing of refrigerant, end parts connected with each other by a U-turn tank(23) and contacting with each other in parallel; a first upper header tank(24) and a second upper header tank(25) placed in parallel with the first and the second lower header tanks to separate from the first and the second lower header tanks and forming flowing passages of the refrigerant; a first extruding tube(26) and a second extruding tube connecting the first and the second upper header tanks and the first and the second lower header tanks, having radiating fins(26a) joined on outer surfaces thereof and a plurality of fine channels with diameters from 0.5mm to 1.0mm and sectional areas approximately circular formed therein to form fine flowing passages of the refrigerant; two tank covers(28) sealing end parts on a same side of the first and the second upper header tanks; and an inlet(29b) and an outlet(29a) of the refrigerant joined to ends of the first and the second header tanks on opposite side of the U-turn tank of the first and the second lower header tanks, respectively.

Description

Heat exchanger

The present invention relates to a heat exchanger, and more particularly to a heat exchanger using carbon dioxide as a refrigerant.

Generally, a heat exchanger is a device for transferring heat from a high temperature fluid to a low temperature fluid through a heat transfer wall. The most commonly used type of heat exchanger is a metal tube as a heat transfer wall, and this type includes cast type, double tube type, multi-tube type with tube type, and tube type type.

HFC refrigerants have been mainly used as an operating medium of air conditioner systems having such heat exchangers. However, such HFC refrigerants have been recognized as one of the main factors of global warming, and the regulations on their use have been gradually expanded. Under these circumstances, researches on carbon dioxide refrigerants have been actively conducted worldwide as representatives of next generation refrigerants to replace HFC refrigerants.

First, carbon dioxide has excellent compression efficiency due to its low operating compression ratio. Second, it has very good heat transfer characteristics, so that the difference between the inlet temperature of the secondary fluid air and the outlet temperature of the refrigerant is much smaller than that of the conventional refrigerant. In addition to the large size, it is highly applicable to the heat pump.

In addition, since carbon dioxide has a volume cooling capacity (evaporative latent heat x gas density) of 7 to 8 times that of the conventional refrigerant R134a, the air conditioner unit can be greatly reduced, and the surface tension is small, so that the boiling heat is excellent, the specific heat is large, and the liquid viscosity is high. It has low thermodynamic characteristics as a refrigerant. In addition, since the operating pressure is 5 to 6 times higher than the conventional method, the loss of the pressure drop of the refrigerant in the system due to the fine formation of the flow path is significantly smaller than that of the conventional refrigerant. Microchannels with excellent furnace heat exchange performance can be used.

Moreover, the refrigeration cycle of carbon dioxide is driven out of critical pressure, as shown in FIG. 1. Referring to the drawings, when the refrigerant is cooled in the gas cooler (2 → 3), the temperature decreases as the material close to the gas changes to the material close to the liquid. Therefore, since the temperature of the gas cooler inlet is higher than the temperature of the outlet, heat transfer occurs through the extruded tube and the heat dissipation fan. Therefore, it is necessary to reduce heat transfer through the extruded tube and the heat dissipation fan. In addition, the lower the temperature of the refrigerant at the outlet of the gas cooler close to the temperature of the fluid flowing from the outside, the better the cooling performance. For example, in FIG. 1, when the temperature is 40 ° C. at the outlet of the gas cooler, the cycle is 1 → 2 → 3 → 4 → 1, whereas when the temperature is 20 ° C. at the outlet of the gas cooler, the cycle It can be seen that the cooling effect of the evaporator side is greatly increased from Q1 to Q2 as 1 → 2 → 3 '→ 4' → 1. Therefore, there is a characteristic that the coefficient of performance (Q / W) varies greatly depending on the temperature of the outlet portion of the gas cooler.

However, since the refrigeration cycle of carbon dioxide is a transcritical pressure cycle, not only the evaporation pressure but also the condensation pressure is 5 to 6 times higher (about 100 to 130 bar) than conventional cycles. Evaporators and condensers in use must be redesigned to withstand these high pressures.

The drawn-cup type evaporator of the conventional vehicle air conditioner evaporator cannot use carbon dioxide as a refrigerant because it cannot withstand high pressure, and when carbon dioxide is used as a refrigerant in a conventional gas cooler, excessive temperature deviation in the heat exchanger Due to this, heat transfer occurs through the heat exchanger surface without heat transfer with the external inlet air, which is the main cause of the decrease in performance. Conventionally, carbon dioxide is generally used as a refrigerant by increasing the thickness of a serpentine heat exchanger without considering such refrigerant characteristics.

However, the conventional heat exchanger has a problem that the thickness of the conventional heat exchanger decreases in heat exchange performance and causes a price increase as well as a large pressure drop on the air side.

The present invention is to solve the above problems, an object of the present invention is to provide a heat exchanger having a structure capable of withstanding the high gas schooling and evaporation pressure required when using carbon dioxide as a refrigerant.

Another object of the present invention is to provide a heat exchanger having a high performance coefficient by minimizing heat transfer between heat dissipation cells in consideration of refrigerant characteristics.

It is another object of the present invention to provide a compact heat exchanger while having a high coefficient of performance.

1 is a P-h graph of a carbon dioxide refrigeration cycle used as a refrigerant in a heat exchanger according to the present invention.

Figure 2a is a perspective view showing a heat exchanger according to a preferred embodiment of the present invention.

FIG. 2B is an enlarged view of part of an ablation enlarged by partially ablation of the U-turn tank region shown in FIG. 2A; FIG.

FIG. 3 is a perspective view illustrating a cross-section taken along line II of FIG. 2A; FIG.

Figure 4 is a view showing a flow path of the refrigerant flowing inside the heat exchanger according to a preferred embodiment of the present invention.

FIG. 5 is a cross-sectional view taken along the line II-II of FIG. 2A. FIG.

<Brief description of symbols for main parts of the drawings>

20: heat exchanger. 21, 22: 1st and 2nd lower header tanks.

21a, 22a: baffle; 23: U-turn tank.

24, 25: 1st, 2nd upper header tank. 26, 27: 1st, 2nd extrusion tube.

26a, 27a: Heat dissipation 휜. 28: Tank cover.

29a, outflow pipe. 29b: inflow pipe.

In order to achieve the above object, the heat exchanger of the present invention, the first and second baffles are respectively formed to block the flow of the refrigerant therein and the ends are connected to each other and in parallel contact with each other by the U-turn tank A lower header tank; First and second upper header tanks spaced apart from each other in parallel with the first and second lower header tanks to form a flow path of the refrigerant; The first and second upper header tanks and the first and second lower header tanks are interconnected to each other, and a heat radiation beam is coupled to an outer surface thereof, and a plurality of minute channels having a predetermined shape are formed therein to form a fine flow passage of the refrigerant. A plurality of parallel first and second extrusion tubes; Two tank covers for sealing respective ends on the same side of the first and second upper header tanks; Refrigerant inlet and outlet pipes coupled to respective ends of the first and second lower header tanks opposite to the U-turn tanks of the first and second lower header tanks; It is characterized by including.

In addition, it is preferable that a gap is formed between the first extruded tubes and the second extruded tubes so that heat transfer is blocked.

Further, it is preferable that the first extruded tube and the second extruded tube are arranged to be offset from each other.

In addition, the diameter of the fine channel formed in the first and second extrusion tube is preferably 0.5 to 1.0 mm.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2a is a perspective view showing a heat exchanger according to a preferred embodiment of the present invention.

Referring to the drawings, the heat exchanger 20 according to the preferred embodiment of the present invention has baffles 21a and 22a respectively formed therein to block the flow of the refrigerant therein, and the end portion is formed by the U-turn tank 23. First and second lower header tanks 21 and 22, which are connected to each other and are in parallel contact with each other; First and second upper header tanks 24 and 25 spaced apart from each other in parallel with the first and second lower header tanks 21 and 22 to form a flow path of the refrigerant; The first and second upper header tanks 24 and 25 and the first and second lower header tanks 21 and 22 are interconnected to each other, and heat dissipation caps 26a and 27a are coupled to an outer surface thereof. A plurality of parallel first and second extruded tubes 26 and 27 formed with a plurality of predetermined shapes of fine channels 26b and 27b to form fine flow passages of the refrigerant; Two tank covers (28) sealing each end on the same side of the first and second upper header tanks (24, 25); Inlet pipes of the refrigerant respectively coupled to the respective ends of the first and second lower header tanks 21 and 22 opposite to the U-turn tanks 23 of the first and second lower header tanks 21 and 22. 29b and outlet pipe 29a; It is characterized by including.

Here, the cross sections of the first and second lower header tanks 21 and 22 are preferably formed so that two inner surfaces separated from each other may have a cross-sectional shape of a round shape, so that they can endure high pressure, but are not necessarily limited thereto. The present invention may be modified in various ways within the scope of the present invention, for example, an ellipse or the like. The cross section of the outer circumferential surface surrounding the two inner surfaces does not necessarily have to be in the shape of a circle and may have various shapes such as an ellipse within the scope of the present invention.

In addition, by forming baffles 21a and 22a in the first and second lower header tanks 21 and 22, respectively, the carbon dioxide refrigerant through the inside of the first and second lower header tanks 21 and 22 may be formed. Allow flow to be interrupted midway. At this time, it is preferable that the formation position of the baffles 21a and 22a is a central portion of each of the first and second lower header tanks 21 and 22, but is not necessarily limited thereto, and it is various within the scope of the present invention. Can be modified.

Furthermore, each end of the first and second lower header tanks 21 and 22 is interconnected by a U-turn tank 23 to the first lower header tank 21 from the second lower header tank 22. The refrigerant is allowed to flow. That is, referring to a partially enlarged view of the U-turn tank 23 shown in FIG. 2B, a hole 23a having a predetermined shape is formed in the inner central portion of the U-tank 23, so that the second lower header tank is formed. The refrigerant flowing out from the 22 passes through the hole 23a and flows into the first lower header tank 21.

In addition, the inlet pipe 29b and the outlet pipe 29a in which the refrigerant flows in and out at each end of the first and second lower header tanks 21 and 22 opposite to the U-turn tank 23 are provided. Are combined respectively. The refrigerant that will flow in the heat exchanger flows into the inlet pipe 29b, and the refrigerant that flows in the heat exchanger flows out into the outlet pipe 29a. The inlet of the outlet pipe 29a is a direction in which a portion in contact with the fluid to be heat-exchanged with the refrigerant is made as wide as possible, for example, as shown in FIG. It is preferable to form so that it may become a phosphorus direction. The inlet of the inlet pipe (29b) is formed to have an appropriate direction in consideration of heat exchange with the outside air, smooth flow of the refrigerant. Preferably, as shown in Figure 2a, it is preferable to form so as to be in a direction parallel to the outlet pipe (29a).

The cross section of the first and second upper header tanks 24 and 25 is the first and second lower header tanks 21 and 22, as shown in FIG. 5 showing the II-II cross section of FIG. 2A. Similar to the cross section of the two inner surfaces that are separated from each other, each of which has a circular cross section, the outer peripheral surface surrounding them is preferably formed so that it is not necessarily a cross section of the round shape.

In addition, a coolant flowing in the first and second upper header tanks 24 and 25 may be connected to both end surfaces of the first and second upper header tanks 24 and 25 by engaging the tank cover 28. To prevent spills. At this time, the tank cover 28, as shown in Figure 2a, may be integrally formed so as to be combined with the two ends on the same side of the first, second upper header tank 24, 25 at the same time, The present invention is not necessarily limited thereto, and may be, for example, separately formed to be coupled to the two ends.

As shown in FIG. 2A, the first and second extruded tubes 26 and 27 respectively include the first and second lower header tanks 21 and 22 and the first and second upper header tanks 24 ( 25 is connected to the first upper and lower header tanks 24 and 21, or the second upper and lower header tanks 25 and 22, respectively. At this time, the first extrusion tube 26 connects the first upper and lower header tanks 24 and 21, and the second extrusion tube 27 is the second upper and lower header tanks 25 and 22. It is desirable to connect.

In addition, heat dissipation fins 26a and 27a are formed on the outer surfaces of the first and second compression tubes 26 and 27 so that heat exchange between the refrigerant and the fluid in which heat is exchanged is smoothly performed.

Furthermore, refrigerant flows between the first and second upper header tanks 24 and 25 and the first and second lower header tanks 21 and 22 inside the first and second extrusion tubes 26 and 27. A plurality of fine channels 26b and 27b are formed for the purpose. The diameters of the fine channels 26b and 27b may be determined by first and second extruded tubes from the carbon dioxide refrigerant through the inner wall of the fine channels 26b and 27b in consideration of thermodynamic characteristics and high condensation pressure characteristics of the carbon dioxide refrigerant. It is formed as small as possible so as to increase the heat transfer efficiency to 26) (27), preferably 0.5 to 1.0 mm. In the case of the conventional refrigerant R134a, since the operating pressure is about 5 to 6 times lower than that of the carbon dioxide refrigerant, when the diameter of the flow passage of the refrigerant is 1 mm or less, there is a problem that the pressure is remarkably lowered. In the case of the example, even if the diameter of the flow passage of the refrigerant is less than 1mm, which is a fine channel, this problem does not occur.

In addition, each of the first extruded tubes 26 and the second extruded tubes 27 are alternately arranged so as to alternate with each other, as shown in FIG. It is preferable to increase the heat transfer by increasing the contact with the fluid to be heat exchanged.

In addition, between the first extruded tubes 26 and the second extruded tubes 27, as shown in FIG. 3, a second extruded tube forming a rear surface of the heat exchanger by forming a gap having a predetermined width ( It is preferable to prevent the high temperature of the refrigerant flowing in each of the 27) from being transferred to the refrigerant in the first extruded tubes 26 forming the front side of the heat exchanger.

Hereinafter, the operation of the heat exchanger according to the present invention having the above configuration will be described.

FIG. 4 flows through the first, second, lower header tanks 24, 25, 21, 22 and any first, second extrusion tubes 26, 27 of the heat exchanger shown in FIG. 2a. It is a figure which shows the flow path of the refrigerant | coolant which becomes.

Looking at the flow path of the carbon dioxide refrigerant with reference to Figures 2a and 4, the carbon dioxide refrigerant introduced from the outside through the inlet pipe 29b of the second lower header tank 22, first, the second lower header tank 22 It flows through the interior of the block and is blocked by the baffles 22a formed therein and can no longer flow [1]. Accordingly, the refrigerant in the second lower header tank 22 is connected to the second upper header tank 25 along the channels 27b in the second extrusion tubes 27 disposed between the baffle 22a and the inlet pipe 29b. ) Ascend to [2]. The elevated refrigerant flows along the inner passage of the second upper header tank 25 [3] and the second extruded tubes 27 disposed between the baffle 22a and the U-turn tank 23. It descends into the second lower header tank 21 along the channels 27b in it [4]. The lowered refrigerant flows along the inside of the second lower header tank 21 [5] and then changes the direction along the inside of the U-turn tank 23 [6]. Flows inwardly [7]. As such, the flow of the refrigerant flows along the inside of the first lower header tank 21 and is blocked by the baffle 21a formed therein, so that the refrigerant cannot flow any more and the U-turn tank 23 and the baffle ( 21a) it rises along the channels 26b in the first extruded tubes 26 disposed between 21a) and flows into the first upper header tank 24 [8]. Thereafter, the refrigerant flows inside the first upper header tank 24 and the first extruded tubes 26 in the reverse order of 1 → 2 → 3 and then flows out through the outlet pipe 29a. → 10 → 11]

As can be seen from the above refrigerant flow path, the high temperature refrigerant introduced through the inlet pipe 29b first flows through the rear surface of the heat exchanger, that is, the surface from which the fluid undergoes heat exchange, and then the front surface of the heat exchanger, that is, the heat exchanger. The fluid is made to flow through the incoming surface, it is possible to minimize the temperature in the outlet pipe (29a).

On the other hand, during the flow of the refrigerant through the first and second extruded tubes 26, 27 and the heat radiation (26a, 27a) is a heat exchange between the carbon dioxide refrigerant and the fluid heat exchanged with it.

Effects of the heat exchanger according to the present invention having the configuration as described above are as follows.

First, the heat exchanger according to the present invention uses a U-turn tank and a baffle to allow a high temperature refrigerant to flow first in the rear part of the heat exchanger, and then a low temperature refrigerant flows in the front part of the heat exchanger. The temperature was minimized. As a result, the performance coefficient of the present invention is greatly improved.

Secondly, the heat exchanger according to the present invention includes first and second phase and lower header tanks having a round-shaped cross section capable of withstanding high pressure, and first and second extruded tubes having finely formed channels through which refrigerant flows. It is able to withstand the high pressure gas-cooling pressure required in heat exchangers using carbon dioxide as a refrigerant.

Third, the heat exchanger according to the present invention allows the first extruded tubes and the second extruded tubes to be displaced with each other so as to increase the heat transfer area by increasing the contact area between the refrigerant and the heat exchanged fluid. Thereby, the coefficient of performance of the heat exchanger according to the present invention is greatly improved.

Fourth, the heat exchanger according to the present invention forms a gap having a predetermined width between the first extrusion tube and the second extrusion tube so that the high temperature of the refrigerant flowing in the rear portion of the heat exchanger flows in the front portion of the heat exchanger. Minimal impact on the refrigerant. Thereby, the performance coefficient of the heat exchanger according to the present invention is greatly improved.

Fifth, the carbon dioxide used as a refrigerant in the heat exchanger according to the present invention has a volume cooling capacity (evaporation latent heat x gas density) of 7 to 8 times that of the conventional refrigerant R134a, so that the performance coefficient is excellent and the refrigeration system can be miniaturized. The furnace may be used as an evaporator as well, and thus may have excellent heat exchange performance capable of withstanding high pressure even in a heat pump.

Although the present invention has been described with reference to the embodiments illustrated in the accompanying drawings, it is merely an example, and those skilled in the art may realize various modifications and equivalent other embodiments therefrom. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (3)

First and second lower header tanks each having a baffle for blocking a flow of refrigerant therein and having end portions connected to each other by parallel contact with each other by a U-turn tank; First and second upper header tanks spaced apart from each other in parallel with the first and second lower header tanks to form a flow path of the refrigerant; The first and second upper header tanks and the first and second lower header tanks are interconnected to each other, and a heat dissipation beam is coupled to an outer surface thereof. A plurality of parallel first and second extruded tubes having channels formed to form fine flow passages of the refrigerant; Two tank covers for sealing respective ends on the same side of the first and second upper header tanks; Refrigerant inlet and outlet pipes coupled to respective ends of the first and second lower header tanks opposite to the U-turn tanks of the first and second lower header tanks; Heat exchanger characterized in that it comprises. The method of claim 1, And a gap is formed between the first extruded tubes and the second extruded tubes so that heat transfer is blocked. The method of claim 1, And the first extruded tube and the second extruded tube are arranged to be offset from each other.