JP6664172B2 - Heat exchanger and air conditioner using the same - Google Patents

Description

  The present invention relates to a heat exchanger and an air conditioner using the same.

  In an air conditioner that adjusts the temperature, humidity, cleanliness, and the like of indoor air, in order to improve the heat exchange efficiency of a heat exchanger (hereinafter, sometimes simply referred to as “efficiency”), it is particularly necessary to use an evaporator. It is effective to suppress an increase in pressure loss due to the evaporation of the refrigerant. For this reason, conventionally, for example, a configuration in which a refrigerant is divided into a plurality of flow paths at a heat exchanger inlet and flows therein has been adopted in many cases.

  Since the refrigerant in the evaporator is in a two-phase state of liquid and gas (gas), it is difficult to make the liquid and gas flow into each of the plurality of flow paths at the same ratio. That is, a state called so-called "drift" occurs in which the ratio of the liquid to the gas is different for each of the plurality of flow paths, which causes a reduction in efficiency.

  For example, Patent Literature 1 relates to a multi-pass heat exchanger, in which refrigerant flowing through a plurality of refrigerant pipes is once merged in the middle of a path and then re-divided immediately thereafter, thereby preventing drift as much as possible and lowering efficiency. Is disclosed.

JP-A-8-313115

  However, in the technique of Patent Document 1, as can be seen from FIG. 1 and the like of Patent Document 1, a horizontal merging portion is provided at an intermediate portion of a plurality (two) of refrigerant pipes arranged in a meandering manner in parallel. Therefore, due to the rectilinearity of the refrigerant flowing through each refrigerant tube, it is not sufficient to reduce the drift due to the merging of the refrigerant.

  Therefore, an object of the present invention is to improve the heat exchange efficiency by reducing the drift when using a plurality of parallel refrigerant tubes in a heat exchanger.

In order to solve the above-described problems, the present invention provides a refrigerant pipe through which a refrigerant flows for performing heat exchange, a first parallel path in which a plurality of refrigerant pipes are arranged in parallel, and a plurality of refrigerant pipes arranged in parallel. A second parallel path, which is connected to the first parallel path, and a merging section for merging the refrigerant, and which is connected to the merging section via a first path member , and sets the refrigerant flow direction from a horizontal direction. A flow direction changing means for changing the flow direction in the vertical direction, the flow direction changing means and the second path member are connected via a second path member, from the flow direction change means, the refrigerant received by the second path member in the vertical direction. A flow dividing unit that divides the flow into the second parallel path. Other means will be described later.

  According to the present invention, when a plurality of parallel refrigerant pipes are used in the heat exchanger, the heat exchange efficiency can be improved by reducing the drift.

1 is an overall configuration diagram of an air conditioner according to an embodiment of the present invention. It is a schematic diagram for explaining a refrigerant course of an indoor heat exchanger in an air conditioner concerning an embodiment of the present invention. FIG. 3 is a diagram illustrating a specific configuration example of a junction in the refrigerant path in FIG. 2. FIG. 3 is a diagram illustrating a specific configuration example of a flow path direction changing unit in the refrigerant path in FIG. 2. FIG. 3 is a diagram illustrating a specific configuration example of a branch portion in the refrigerant path in FIG. 2. It is a graph which shows specification A and specification B of the indoor heat exchanger concerning an embodiment of the present invention, and shows a relation between a refrigerant pipe position and pressure. It is a graph which shows the relation between the number of rotations of a compressor and the capacity about specification A and specification B of the indoor heat exchanger concerning an embodiment of the present invention. 4 is a graph showing a relationship between a refrigerant circulation amount and a pressure loss when a two-phase flow in a refrigerant pipe is assumed to be a homogeneous flow with respect to specifications A and B of the indoor heat exchanger according to the embodiment of the present invention.

  Hereinafter, the configuration, function, and operation of the air conditioner according to the embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the air conditioner 100 includes a compressor 1, a four-way valve 2 (flow path switching means), an outdoor heat exchanger 3 installed outdoors, and a flow control valve 4 (throttle device for cooling and heating operation). And an indoor heat exchanger 5 installed indoors, which are connected in a ring through a refrigerant pipe 8 to constitute a refrigeration cycle device capable of cooling and heating.

The outdoor heat exchanger 3 is provided with an outdoor blower 6 such as a propeller fan, and the air is passed through the outdoor heat exchanger 3 to exchange heat with the refrigerant.
Further, the indoor heat exchanger 5 is provided with an indoor blowing means 7 such as a once-through fan, and the air is circulated through the indoor heat exchanger 5 to exchange heat with the refrigerant.

  Next, the refrigerant path of the indoor heat exchanger 5 will be described with reference to FIG. The refrigerant path flowing through the indoor heat exchanger 5 includes a single path 50, a first parallel path 52 including a plurality of (for example, four) paths, a junction 53, a single path 54, and a flow direction changing unit 55. , A single path 56, a branching section 57, and a second parallel path 58 composed of a plurality of (for example, eight) paths. Note that the heat exchange position 51 is a portion where the first parallel path 52 performs heat exchange. The heat exchange position 59 is a portion where heat exchange is performed in the second parallel path 58.

  The junction 53 connects the first parallel path 52 and the path 54, and is connected to, for example, a main pipe 53 a connected to the path 54 and the first parallel path 52, as shown in FIG. 3. It is configured as a header pipe including a plurality (for example, four) of branch pipes 53b.

  The flow path direction changing means 55 connects the path 54 and the path 56. For example, as shown in FIG. 4, the horizontal path 54 and the vertical (vertical vertical direction) path 56 are connected at a right angle. Is done.

  The branching section 57 connects the path 56 and the second parallel path 58. For example, as shown in FIG. 5, an inlet pipe 57a connected to the path 56, a distributor 57b, and a second parallel path 58 It is composed of a flow divider having a branch pipe 57c connected to each.

  Next, the operation of the refrigeration cycle of the air conditioner 100 according to the present embodiment will be described. As shown in FIG. 1, during the cooling operation, the four-way valve 2 is switched so that the refrigerant flows through a portion indicated by a broken line.

  At this time, the refrigerant proceeds in the direction of the dashed arrow in FIG. 1 and flows through the compressor 1, the four-way valve 2, the outdoor heat exchanger 3, the flow control valve 4, and the indoor heat exchanger 5 in this order. The flow control valve 4 is adjusted to an appropriate opening degree according to the air conditioning load, and the refrigerant condensed and liquefied in the outdoor heat exchanger 3 functioning as a condenser becomes a gas-liquid two-phase flow at the flow control valve 4, It flows into the indoor heat exchanger 5. Thereafter, the refrigerant evaporates in the indoor heat exchanger 5 functioning as an evaporator, and then returns to the compressor 1.

  During the cooling operation, the refrigerant flows in the direction of the dashed arrow in FIG. 2 and flows from the path 50 into the first parallel paths 52 separately. At this time, the mass flow rate ratio (dryness) of the gas to the total flow rate of the refrigerant in the passage 50 is about 0.2. Since the refrigerant exchanges heat with air at the heat exchange position 51 in the first parallel path 52, the dryness increases to about 0.6.

  After passing through the first parallel path 52, the refrigerant joins at the junction 53 and flows into the single path 54 (see FIG. 3), and the flow direction is changed from the horizontal direction to the vertical direction by the flow path direction changing means 55. The flow is changed and flows into a single path 56 (see FIG. 4), and is split again and flows into each of the second parallel paths 58 at the branching section 57 (see FIG. 5). The diverted refrigerant exchanges heat with air at the heat exchange position 59 in the second parallel path 58, and the dryness further increases to 1.0 or more, and returns to the compressor 1 via the path 60. .

By causing the refrigerant diverted in the first parallel path 52 to join one path in the junction 53, the drift generated in the first parallel path 52 is canceled.
Thereafter, when the refrigerant having a relatively high degree of dryness is diverted to flow into the second parallel path 58, the diverter 57 adjusts the heat exchange amount at the heat exchange position 59 in each of the divided second parallel paths 58. The gas is separated at a gas-liquid ratio.

  Further, the two-phase refrigerant having a high degree of dryness and a small amount of liquid refrigerant has an annular flow in which a thin liquid film is stuck to the pipe wall, and the degree of drift at the time of subsequent branching is likely to change depending on the direction of the path. Therefore, by providing the flow direction changing means 55 to change the flow direction of the refrigerant from the horizontal direction to the vertical direction (see FIG. 4), the thin liquid film on the tube wall is broken, and a state close to a homogeneous flow is obtained. Thus, a stable branching (with a small degree of drift) can be performed in the branching section 57.

  At this time, if the flow path cross-sectional area of the pipe of the junction 53 is too small compared to the sum of the flow path cross-sections of the pipes of the first parallel path 52 on the upstream side of the junction 53, the pressure loss increases. Is concerned. When it is desired to obtain a high cooling capacity (hereinafter sometimes simply referred to as “capacity”) due to an increase in the pressure loss, even if the compressor 1 is accelerated to increase the refrigerant circulation amount, the refrigerant circulation amount increases. Instead, their abilities peak off.

  This will be described using a specific example with reference to FIGS. FIG. 6 shows measured values of the pressure distribution in the pipe of the indoor heat exchanger 5. FIG. 7 shows a change in the cooling capacity when the speed of the compressor 1 is increased and the amount of circulating refrigerant is increased.

  For example, the inside diameter of each of the first parallel paths 52 upstream of the junction 53 is DI0, the number of branches (the number of tubes) is N, the inside diameter of the junction 53 is DI1, and DI0 = 5.75 mm, N = 4, DI1 = 7.2 mm. This is designated as specification A.

As shown in FIG. 6, in the specification A, the pressure drops rapidly due to the pressure loss in a short section (path 54 to path 56) from the junction 53 to the branch 57, causing an increase in the overall pressure loss. I have.
For this reason, as shown in FIG. 7, in the specification A, even if the compressor 1 is accelerated, the amount of circulating refrigerant does not increase, and the capacity does not exceed 9 kW (a standard value of the capacity required in recent years). turn into.

  Subsequently, DI0 = 5.75 mm, N = 4, and DI1 = 8.72 mm. This is designated as specification B. As shown in FIG. 6, in the specification B, since the pressure loss in the section (paths 54 to 56) from the junction 53 to the branching part 57 is significantly smaller than that in the specification A, the overall pressure loss also decreases. I have. In this specification B, since the pressure loss is small, the amount of circulating refrigerant can be increased. As shown in FIG. 7, the cooling capacity is linearly increased even at the rotation speed of the compressor 1 which has reached a plateau in specification A. And 9 kW can be realized.

  FIG. 8 shows the relationship between the pressure loss and the refrigerant circulation amount when the two-phase flow in the pipe is assumed to be a homogeneous flow in the specifications A and B. That is, at least when the pressure loss is equal to or less than the case of the specification B, a high cooling capacity such as 9 kW can be realized by increasing the refrigerant circulation amount (see FIG. 7).

Here, the sum of the cross-sectional areas of the pipes of the first parallel path 52 upstream of the merging section 53 in the specifications A and B is compared with the cross-sectional area of the pipe of the merging section 53.
The cross-sectional area S of the tube can be expressed by the following equation (1) using the pi, where D is the diameter.
S = πD ^2/4 ··· formula (1)

Further, the total sum S0 of the flow path cross-sectional areas of the tubes of the first parallel path 52 can be expressed by the following equation (2) using the number of paths N.
^{S0 = (πDI0 2/4)} × N ··· formula (2)

Further, the flow path cross-sectional area S1 of the pipe of the junction 53 can be expressed by the following equation (3).
S1 = πDI1 ^2/4 ··· (3)

Therefore, the ratio (S1 / S0) of the sum of the cross-sectional areas of the pipes of the first parallel path 52 to the cross-sectional area of the pipe of the junction 53 can be expressed by the following equation (4).
S1 / S0 = DI1 ² / (DI0 ² × N) Equation (4)

  When calculated using this equation (4), the ratio S1 / S0 in the specification A is about 0.39, the ratio S1 / S0 in the specification B is about 0.57, and the specification B is larger.

Therefore, in order to make the pressure loss from the junction 53 to the branch 57 equal to or smaller than the specification B, DI0 (the pipe inner diameter of each of the first parallel paths 52) and DI1 (the pipe of the junction 53) (Inner diameter) may be designed to satisfy the following expression (5).
DI1 ² / (DI0 ² × N) ≧ 0.57 Expression (5)

  As described above, according to the present invention, in the indoor heat exchanger 5, the flow direction of the refrigerant is changed from the horizontal direction to the vertical direction during the cooling operation by providing the flow path direction changing unit 55, thereby reducing the drift. Heat exchange efficiency can be improved.

  In addition, by designing the indoor heat exchanger 5 so as to satisfy the expression (5), the pressure loss from the junction 53 to the branch 57 can be made equal to or smaller than the specification B, and When the speed is increased, the capacity does not reach its peak (see FIG. 7), and the heat exchange efficiency can be improved.

  In addition, the air conditioner 100 includes such an indoor heat exchanger 5 and can achieve high cooling capacity.

This concludes the description of the present embodiment, but aspects of the present invention are not limited thereto. For example, the number of parallel paths in the first parallel path 52 and the second parallel path 58 is not limited to the example shown in the embodiment, and may be another number.
In addition, the specific configuration can be appropriately changed without departing from the gist of the present invention.

1 Compressor 2 Four-way valve (channel switching means)
3 Outdoor heat exchanger 4 Flow control valve (throttle device for cooling and heating operation)
Reference Signs List 5 indoor heat exchanger 6 outdoor blowing means 7 indoor blowing means 8 refrigerant pipe 50, 54, 56, 60 path 51 heat exchange position 52 first parallel path 53 junction section 55 flow direction changing means 57 branching section 58 second Parallel path 59 Heat exchange position 100 Air conditioner

Claims (3)

As a refrigerant pipe through which a refrigerant flows to perform heat exchange,
A first parallel path in which a plurality of refrigerant pipes are arranged in parallel,
A second parallel path in which the plurality of refrigerant tubes are arranged in parallel,
A merging section connected to the first parallel path and merging a refrigerant;
Flow path direction changing means connected through the junction and the first path member to change a flow direction of the refrigerant from a horizontal direction to a vertical direction;
A flow dividing unit connected to the flow path direction changing means and a second path member, and from the flow path direction changing means, for dividing the refrigerant vertically received by the second path member into the second parallel path; ,
A heat exchanger comprising: The heat exchanger according to claim 1,
When operating as an evaporator, refrigerant flows from the first parallel path toward the second parallel path,
When the pipe inner diameter of each of the first parallel paths is DI0, the number of parallel paths is N, and the pipe inner diameter of the junction is DI1,
DI12 / (DI02 × N) ≧ 0.57
A heat exchanger characterized by satisfying the following. A compressor, a flow path switching means, an outdoor heat exchanger, a throttle device for cooling and heating operation, and a refrigeration cycle device in which the indoor heat exchanger is connected by a refrigerant pipe,
The air conditioner, wherein the indoor heat exchanger is the heat exchanger according to claim 1 or 2.

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