JP2003090646A - Heat exchanger for air conditioner - Google Patents

Abstract

(57) Abstract: A heat exchanger for an air conditioner that can distribute a refrigerant evenly and flow evenly through a plurality of paths even when a two-phase gas-liquid refrigerant having a high degree of dryness is targeted. I will provide a. SOLUTION: A groove 2 is arranged in a circumferential direction on an inner surface of an inflow pipe 1 of a refrigerant distributor 6, and a refrigerant storage section 3 having a larger sectional area than another part is formed in a part of the inflow pipe 1 in an axial direction. I do. The liquid refrigerant 9a flowing through the pipe wall once flows through the entire groove 2 under its own surface tension greater than the gravity after temporarily accumulating in the refrigerant reservoir 3, so that the refrigerant 9a is distributed to the outflow pipes 4a and 4b. Can be performed evenly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger for an air conditioner, and in particular, even when a gas-liquid two-phase refrigerant having a high degree of dryness is targeted, the refrigerant is evenly distributed to a plurality of paths. The present invention relates to a heat exchanger for an air conditioner that allows uniform flow.

[0002]

2. Description of the Related Art FIG. 10 shows a refrigeration cycle of a generally known air conditioner. In the air conditioner for both cooling and heating, the refrigerant made into a high-temperature and high-pressure gas by the operation of the compressor 21 first flows to the point A at the inlet of the condensation heat exchanger 23 via the four-way valve 22 that switches the flow direction. .

FIG. 11 shows a general structure of the cross fin tube type heat exchanger used in FIG.
It has a configuration in which a meandering heat transfer tube 25 is penetrated through a plurality of fins 24 arranged in parallel at regular intervals. The refrigerant is the heat transfer tube 25.
Heat is exchanged with the air as it flows through and through the fins 24.

In FIG. 10, the refrigerant that has flowed through the condensing heat exchanger 23 having the above structure and has radiated heat by exchanging heat with air under high pressure is liquefied by the condensing action of the heat exchanger 23. It becomes a supercooled state (a temperature lower than the saturated liquid temperature), flows out to the point B, and is subsequently subjected to isenthalpic expansion by the expansion section 26 such as an electrically operated valve, and then the gas-liquid mixture of gas liquid mixed under low temperature and low pressure is used. It becomes a phase flow and flows to the inlet C point of the evaporation heat exchanger 27.

The refrigerant sent to the evaporative heat exchanger 27 is
In order to cool the air, it evaporates by the endothermic action from the air and flows inside the heat exchanger 27 while increasing the dryness [= gas mass flow rate / (gas mass flow rate + liquid mass flow rate)], and at the intermediate point D and It returns to the compressor 21 via the exit point E.

In this closed loop, the loss due to the flow resistance in the heat exchanger 27 acts so as to reduce the heat exchange performance, so that a parallel branch configuration is formed by combining a plurality of paths 28 and 29 or 30 and 31. Is normally adopted, and therefore, at points C and D, a refrigerant distributor 32 for dividing the refrigerant is attached.

However, according to the above cycle configuration, since the liquid refrigerant and the gaseous refrigerant having a density difference of several tens of times are mixed in the split flow field, a free interface of gas and liquid is generated in the refrigerant pipe. When the installation angle of the refrigerant distributor 32 is varied due to individual differences in production or the like, the difference in gravity received by the liquid refrigerant causes, for example, between 30 and 31. Thus, a path with a sufficient amount of liquid refrigerant and a path with exhaustion will occur, and the heat exchange after the exhaustion portion will be reduced to lower the function as an air conditioner.

[0008] Further, in the cycle dry system, that is, a part of the evaporative heat exchanger serving as an indoor heat exchanger is made to function as a condensing heat exchanger, and the respective outlet air is mixed so that the blowout temperature of the indoor unit is not lowered. When adopting the high comfort reheat dehumidification method as described above, the evaporative heat exchanger 2
Since the refrigerant distributor 32 is provided in the middle of step 7, the dryness of the refrigerant is further increased, and the distribution of the refrigerant becomes more difficult.

FIG. 12 shows the cycle configuration of FIG. 10 on the Mollier diagram. A broken line shows a general refrigeration cycle for an air conditioner using a chlorofluorocarbon refrigerant, which operates counterclockwise. A to E in the figure correspond to A to E in FIG. In this figure, the problem in refrigerant distribution is C
It is a part of the low-temperature and low-pressure evaporation heat exchanger from the point to the point E.

After the isenthalpic expansion, the refrigerant flows into the evaporative heat exchanger from point C. The dryness near this C point is
There is a saturated liquid line (dryness x = 0), which is relatively small, and the level is around x = 0.2 in the case of a general air conditioner. Further, at this point, since the amount of the refrigerant is large, it is theoretically possible to generate a force larger than gravity by giving a swirling component to the refrigerant liquid, thereby improving the refrigerant distribution.

Specific means for giving a swirling component to the refrigerant liquid include, for example, Japanese Patent Laid-Open Nos. 5-18638 and 6-
317364, JP-A-7-12429, JP-A-200
0-105026 or JP 2000-27488.
Measures such as No. 5 can be mentioned. These are provided with spiral grooves on the inner surface of the pipe before and after the branch portion of the refrigerant distributor incorporated in the heat exchanger, and the groove gives a swirling force to the flow of the refrigerant. It has been shown that this suppresses the uneven flow of the refrigerant.

According to Japanese Patent Laid-Open No. 8-68575,
An air conditioner incorporating a refrigerant distributor in which a bundle of small-diameter tubes is spirally formed inside the distributor to cause the refrigerant to swirl and the non-uniform flow of the refrigerant is eliminated by the stirring action by this A heat exchanger for use is shown, and each of the above-mentioned heat exchangers is described as having a corresponding drift prevention effect.

[0013]

However, according to these conventional heat exchangers for air conditioners, when the branch path is provided in the middle of the evaporative heat exchanger, the condition that the dryness of the refrigerant is particularly high is Therefore, there is a problem that the liquid refrigerant becomes extremely small and swirl flow is difficult to be generated.

For example, R, which is often used in air conditioners
Taking the 410A refrigerant as an example, the evaporation pressure is 1300 kPa,
At the branching position where the evaporation temperature is 16 ° C and the dryness is about 0.65, the state of the gas is 93% of the cross section of the pipe.
On the other hand, since the liquid substance is a gas-liquid two-phase containing only 7%, it is extremely difficult to give a swirling force to this.

Therefore, an object of the present invention is to provide a heat for an air conditioner capable of evenly distributing the refrigerant and allowing it to flow evenly through a plurality of paths even when a gas-liquid two-phase refrigerant having a high degree of dryness is targeted. To provide an exchange.

[0016]

In order to achieve the above-mentioned object, the present invention provides a refrigerant distributor comprising a refrigerant inflow pipe and a plurality of outflow pipes branched from the inflow pipe and outflowing the refrigerant. In the heat exchanger for an air conditioner, the inflow pipe has a plurality of groove portions arranged in the circumferential direction of the inner surface, and a refrigerant storage portion having a cross-sectional area in a part of the axial direction larger than other parts. The present invention provides a heat exchanger for an air conditioner, which comprises:

In the present invention, in order to achieve even distribution of the refrigerant to a higher degree, the constituent conditions of the inflow pipe in the built-in refrigerant distributor are shown below according to the type of the refrigerant used (1). It is preferable to set as in the formula and the formula (2).

That is, when a CFC refrigerant is used as the refrigerant, the angle of the inflow pipe with respect to the gravity direction in the axial direction is θ, the minimum inner diameter of the inflow pipe formed by the convex portions on both sides of the groove is D _min , and the groove is _Let W _{max be} the maximum width of
It is preferable that the relation of the following formula (1) is established, while it is preferable that the relation of the following formula (2) is established when the refrigerant is a natural refrigerant such as carbon dioxide gas or propane gas. .

[Equation 3]

[Equation 4]

The cross-sectional shape of the grooves arranged in the circumferential direction of the inner surface of the inflow pipe is preferably trapezoidal, triangular, quadrangular or semicircular, and the above formulas (1) and (2) are used. For example, if the groove has a triangular cross section, the inner width of the opening end corresponds to W _max in.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a heat exchanger for an air conditioner according to the present invention will be described. FIG. 1 shows the configuration of a refrigerant distributor incorporated in a heat exchanger, where 1 is an inflow pipe through which a gas-liquid two-phase refrigerant flows in the direction of arrow F, and 2 is a plurality of groove portions formed on the inner surface thereof. Reference numeral 3 denotes a refrigerant storage portion formed in a part of the inflow pipe 1 on the base side, and has a larger cross-sectional area than other portions.

4a and 4b are provided at the tip of the inflow pipe 1, and a plurality of outflow pipes 5 for distributing and sending out the refrigerant sent from the inflow pipe 1 side, and 5 are inflow pipe 1 and outflow pipes 4a and 4b.
The joint part by the brazing provided in the integrated part is shown. The angle θ in the figure means the installation angle of the refrigerant distributor 6 having the above-mentioned configuration with respect to gravity in the heat exchanger.

FIG. 2A shows a sectional shape of the inflow pipe 1 in the axial direction, and has a structure in which a plurality of groove portions 2 are arranged on the entire inner surface in the circumferential direction. D _min indicates the minimum inner diameter of the inflow pipe 1 formed by the convex portions 2 a located on both sides of the groove 2 as a component of the groove 2.

FIG. 2B is a horizontal development view of the portion H of FIG. 2A, in which the groove 2 is trapezoidal and W
_max indicates the maximum width in this trapezoidal shape. Figure 3
A part of the inflow pipe 1 is expanded and shown, and the groove 2 has
An angle β is given to the axial direction of the inflow pipe 1.

FIG. 4 shows a refrigerant distributor 6 joined to a pipe 7 via an elbow 8 in a heat exchanger of an air conditioner.
The installation state of is shown. In such a configuration, the liquid refrigerant 9a in the gas-liquid two-phase refrigerant whose dryness is increased in the middle of the heat exchanger (not shown) is, by its nature, flown into the pipe wall surface as an annular flow. On the other hand, the gaseous refrigerant 9b also flows at high speed in the central portion due to its nature.

In this case, in the normal flow, if there is a curved portion such as the elbow 8 in the front flow portion, it is common that the liquid refrigerant 9a has a non-uniform thickness, so that a uniform flow is obtained. It becomes difficult to maintain such a smooth flow, and the function of uniform distribution originally possessed by the distributor is lost. However, in the case of the present embodiment, since the refrigerant storage part 3 having a large cross-sectional area exists, The liquid refrigerant 9a once collects in the storage section 3,
After that, it flows into the groove portions 2 arranged in the circumferential direction.

The inflow and the subsequent flow of the liquid refrigerant 9a from the storage portion 3 into the groove portion 2 are evenly performed in the circumferential direction of the inflow pipe 1 under the surface tension of the refrigerant 9a itself which is larger than gravity. Therefore, even if there is a production variation in the installation angle θ, the refrigerant flow during this period is not affected by gravity, and stable and uniform refrigerant distribution is performed. Like An equal amount of gas-liquid two-phase refrigerant 9 is discharged from the outflow pipes 4a and 4b.

The bond number, which is a dimensionless number, can be cited as an index that is effective when determining the size of the groove 2 from the relationship between the surface tension of the refrigerant 9a and the gravity. Below (3)
The formula is a formula for obtaining the bond number Bo by weaving the installation angle θ of FIG. 1 and the minimum inner diameter D _min and the maximum width W _max of FIG. 2, and the gravity acceleration is g, the liquid density is ρ1, and the gas density is It is a relational expression when (rho) v and the surface tension of the liquid refrigerant 9a are set to (sigma).

[Equation 5]

In this equation, the effect of surface tension is larger than the effect of gravity in the range where the bond number Bo is less than 1, and this shows the relationship between the installation angle θ and the dimension of the groove 2 with respect to the direction of gravity. Can be set.

FIG. 5 shows the reciprocal of the product of the minimum inner diameter D _min (unit: mm) and the maximum width W _max (unit: mm) in the groove portion 2 calculated by substituting the physical property values into the above equation (3). Is a relational diagram when the allowable installation angle θ is taken as the vertical axis.
In the figure, in addition to the CFC-based refrigerant R410A that is often used in air conditioners, R407C, R134a, and R2.
2 and R32, and the application results of carbon dioxide gas and propane gas that are natural refrigerants are shown.

It should be noted that each refrigerant was calculated using the physical property value at -20 ° C which is considered to be the lowest temperature of the evaporation condition as an air conditioner. Therefore, when the temperature is higher than this, the slope of the line shown in the graph becomes gentler than that displayed.

The angle θ is obtained by the following equation (4), and the coefficient C
Was set to 80 in the case of R410A, 91 in the case of R32, and 166 in the case of propane gas, and the right side of the line in the drawing was within the scope of the present invention.
That is, according to FIG.
2. In natural refrigerants, propane gas can be representative of each refrigerant system, and thus their lower zone is within the scope of the invention. In FIG. 5, the above-mentioned (1)
The meanings of the expressions and (2) are shown.

[Equation 6]

FIG. 6 shows, by experiments, the effect of the presence of the refrigerant reservoir 3 in the inflow pipe 1 of the refrigerant distributor 6 in the heat exchanger for an air conditioner of the present invention. An elbow 8 is provided on the inlet side of the inflow pipe 1 of the refrigerant distributor 6, and the circulation rate of the refrigerant is set to 62 kg / h.
It shows the deviation from the proper amount of the refrigerant amount on the one outflow pipe 4a side when the dryness at the inlet of the distributor 6 is set to 0.65.

In the figure, the data shown on the left side shows the case where a refrigerant distributor in which the refrigerant storage part 3 is not formed is incorporated in the inflow pipe 1, while the data on the right side shows the refrigerant storage part 3.
When a refrigerant distributor having a cross-sectional area of 2 times that of the other parts is incorporated, this shows that the former shows a deviation of 10% from the proper distribution amount. The latter is only 2%, and the existence value of the refrigerant storage portion 3 is remarkably exhibited.

It should be noted that the effect of the even distribution of the refrigerant in the present invention is not based on the conventional application of the turning force.
It has been confirmed by comparing an example in which the angle β is appropriately set within the range of 0 to 8 ° with an example in which the angle β is set to 20 °.

That is, the sufficient effect is obtained in several cases of 0 to 8 ° where turning is difficult to occur, while the effect is at the same level when the angle is 20 °, which is sufficient to impart the turning force. From this, it is clear that the effect of the present invention does not depend on the turning force. It goes without saying that there is no restriction on the angle β.

It should be noted that the groove portion 2 may be formed at a portion other than the entire length of the inflow pipe 1 excluding the refrigerant storage portion 3 as shown in FIG. The configuration and the form are not limited as long as the above-described effect by forming the refrigerant storage portion 3 is achieved, such as the total length including

FIG. 7 shows another embodiment of the present invention, showing an example of the shape of the groove 2. (A) shows an example in which the groove portion 2 is formed in a quadrangle, (b) shows an example in which it is formed in a triangle, and (c) shows an example in which it is formed in a semicircular shape. In each case, the largest width in the groove portion 2 is the maximum width W _{max according} to the present invention.
Therefore, the minimum inner diameter D _min of the inflow pipe 1 is determined by the convex portions 2a located on both sides of the groove portion 2.

FIG. 8 shows a connection state of the inflow pipe 1 and the outflow pipes 4a and 4b of the refrigerant distributor 6 in the present invention. In FIG. 8A, the refrigerant flows from the groove portion 2 to the outflow pipes 4a and 4b. This is an example in which the end portions of the inflow pipe 1 and the outflow pipes 4a and 4b are brought into contact with each other so as to be easy, and are integrated so that the mutual gap is L = 0. On the other hand, FIG. Outflow pipe 4
In this example, a gap L is formed between a and 4b.

The latter example is a structure that tends to occur when the ends of the pipes are difficult to contact with each other due to the precision in the brazing work for forming the joint 5, but the inflow pipe 1 and the outflow pipe 4a.
As long as the refrigerant is circulated between 4 and 4b, there is no problem and the configuration is allowed.

FIG. 9 shows an outline of the path piping in the air conditioner in which the heat exchanger of the present invention is incorporated in the middle of the piping. The upper heat exchanger 10, the lower heat exchanger 11 and the cross flow fan 12 are shown in FIG. It is composed of a combination.

During the cooling operation, the refrigerant is branched by the refrigerant distributor 13 and flows in the upper heat exchanger 10. After that, the refrigerant collectively passes through the cycle dry valve (dehumidification expansion valve) 14 and then passes through two paths. And flows in the lower heat exchanger 11. The cycle dry valve 14 is fully opened during the normal cooling operation and throttled during the dehumidifying operation.

Reference numeral 6 denotes the refrigerant distributor shown in FIGS. 1 to 3, and the lower heat exchanger 11 is provided in the outflow pipes 4a and 4b thereof.
The two paths 15 and 16 in are connected. The refrigerant flowing into the refrigerant distributor 6 passes through the refrigerant storage portion 3 of the inflow pipe 1 of the distributor 6 and then flows into all the groove portions 2 arranged in the circumferential direction of the inflow pipe 1, and thereafter, The surface tension evenly flows into the two outflow pipes 4a and 4b while suppressing the influence of gravity, and flows out to the paths 15 and 16.

As a result, the lower heat exchanger 11 passes through the path 15
An even refrigerant flow in and 16 will be ensured and a given function will be launched. Therefore, the installation angle θ of the refrigerant distributor 6 due to variations in manufacturing the heat exchanger
Even if there is a displacement in the air conditioner, the influence does not appear, and the air conditioner can always be operated in a good condition.

In FIGS. 1 to 9 described above, a configuration example in which the outflow pipes 4a and 4b are arranged above and the flow of the refrigerant is an upward flow with respect to the gravity direction has been described. It is needless to say that the same effect can be obtained also in the case of the downward flow configuration in which 4b is arranged downward.

[0045]

As described above, according to the heat exchanger for an air conditioner of the present invention, a plurality of grooves are formed in the circumferential direction of the inner surface of the inflow pipe of the incorporated refrigerant distributor, and the inflow pipe is Since the refrigerant storage part having a larger cross-sectional area than the other part is formed in a part of the axial direction, the refrigerant flowing into the inflow pipe may be temporarily stored in the refrigerant storage part and then be affected by gravity. Instead, the refrigerant uniformly flows into all the groove portions in the circumferential direction of the pipe, so that it is possible to uniformly distribute the refrigerant to the plurality of outflow pipes.

The distribution of the refrigerant based on the above mechanism is performed regardless of the degree of dryness of the refrigerant, and therefore, it is possible to provide a heat exchanger for an air conditioner which always has a stable function. it can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a refrigerant distributor in an embodiment of a heat exchanger for an air conditioner according to the present invention.

2A and 2B are explanatory views showing a sectional structure of the refrigerant distributor shown in FIG. 1, in which FIG. 2A is a sectional view taken along line GG in FIG. 1, and FIG. 2B is a horizontal development view of a portion H in FIG. Indicates.

FIG. 3 is a development view showing an inner surface configuration of the inflow pipe shown in FIG. 1.

FIG. 4 is an explanatory view showing a mounting structure of the refrigerant distributor shown in FIG. 1.

5 is an explanatory diagram showing a relationship between an installation angle and a reciprocal of a product of a minimum inner diameter of an inflow pipe and a maximum width of a groove formed on an inner surface of the inflow pipe in the refrigerant distributor shown in FIG.

FIG. 6 shows a heat exchanger for an air conditioner according to the present invention,
Explanatory drawing which shows the effect of a refrigerant | coolant storage part.

FIG. 7 is an explanatory view showing another embodiment of the heat exchanger for an air conditioner according to the present invention, in which (a) to (c) show the configuration of a groove portion formed on the inner surface of the inflow pipe of the refrigerant distributor. Here is an example:

FIG. 8 is an explanatory diagram showing an example of a relationship between an inflow pipe and an outflow pipe of the refrigerant distributor according to the present invention.

FIG. 9 is an explanatory diagram showing an outline of an example of path piping in an air conditioner incorporating a heat exchanger according to the present invention.

FIG. 10 is an explanatory diagram showing a refrigeration cycle of the air conditioner.

FIG. 11 is an explanatory diagram showing a configuration example of a cross fin tube type heat exchanger.

12 is an explanatory diagram showing the cycle configuration of FIG. 10 on a Mollier diagram.

[Explanation of symbols]

1 inflow pipe 2 groove 2a convex part 3 Refrigerant reservoir 4a, 4b Outflow pipe 5 connection 6,13 Refrigerant distributor 8 Elbow 9 Refrigerant (gas-liquid two-phase) 9a Liquid refrigerant 9b Gaseous refrigerant 10 Upper heat exchanger 11 Lower heat exchanger 12 Cross-flow fans 14 cycle dry valve 15, 16 passes

Continued front page    (72) Inventor Yoshio Suzuki             Hitachi, 1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture             Electric Cable Co., Ltd. (72) Inventor Hobomori             Hitachi, 1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture             Electric Cable Co., Ltd. (72) Inventor Kenichi Inui             Hitachi, 1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture             Electric Cable Co., Ltd. (72) Inventor Shigeyuki Sasaki             502 Kintatemachi, Tsuchiura City, Ibaraki Japan             Tate Seisakusho Mechanical Research Center

Claims (4)

[Claims] 1. A heat exchanger for an air conditioner, comprising: a refrigerant distributor comprising a refrigerant inflow pipe and a plurality of outflow pipes branched from the inflow pipe to let out the refrigerant. A heat exchanger for an air conditioner, wherein a plurality of groove portions are arranged in a circumferential direction of an inner surface, and a refrigerant storage portion having a larger cross-sectional area than the other portion is provided in a part of the axial direction. 2. When the angle of the inflow pipe with respect to the direction of gravity in the axial direction is θ, the minimum inner diameter formed by the convex portions on both sides of the groove is D _min , and the maximum width in the groove is W _max. The heat exchanger for an air conditioner according to claim 1, wherein the relationship of the following formula (1) is established when the refrigerant is a chlorofluorocarbon type. [Equation 1] 3. The inflow pipe, wherein an angle of the axial direction with respect to the gravity direction is θ, a minimum inner diameter formed by convex portions on both sides of the groove is D _min , and a maximum width in the groove is W _max. The heat exchanger for an air conditioner according to claim 1, characterized in that when the refrigerant is a natural refrigerant such as carbon dioxide gas or propane gas, the following equation (2) is satisfied. [Equation 2] 4. The heat exchanger for an air conditioner according to claim 1, wherein the cross section of the groove is trapezoidal, triangular, quadrangular or semicircular.