JP2003262433A - Heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger capable of improving capacity in condensation while lessening an increase in refrigerant pressure loss in evaporation by appropriately determining the arrangement of two or more kinds of heat exchanger tubes with different helix angles. <P>SOLUTION: This heat exchanger has a heat exchanger tube 21a performing heat exchange by the condensation or evaporation of a refrigerant in the tube with a groove 33 spirally formed on the inner surface of the tube at a prescribed helix angle to the axis of the tube, and a fin 22 into which the heat exchanger tube 21a is inserted. In constituting the heat exchanger, a plurality of heat exchanger tubes 1-5 with different helix angles are connected, and the heat exchanger, tubes 3-5 with the large helix angles out of a plurality of connected heat exchanger tubes 1-5 are arranged on the small dryness side of the refrigerant rather than the large dryness side. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger used in an air conditioner, a heat pump, etc., and particularly to a heat exchanger using a heat transfer tube for exchanging heat by condensing or evaporating a refrigerant in the tube. Regarding

[0002]

2. Description of the Related Art Generally, a heat exchanger in an air conditioner, a heat pump or the like has a heat transfer tube for exchanging heat by passing a refrigerant through the heat transfer tube and evaporating or condensing the refrigerant in the heat transfer tube. Is used.

FIG. 6 is a view showing a refrigerating cycle of a conventional air conditioner, heat pump and the like. In FIG. 6, 12 is a compressor, 13 is an indoor heat exchanger, 14 is an outdoor heat exchanger, 15 is an expansion valve, and 16 is a four-way valve. Dashed line 10
Indicates the flow of the refrigerant during the cooling operation, and the solid line 11 indicates the flow during the heating operation.

FIG. 7 is a diagram showing the structure of a heat exchanger used in a conventional air conditioner, heat pump, etc.,
(A) is a side view and (b) is a front view. Heat exchanger
A heat transfer tube 21, fins 22 that exchange heat with an external fluid,
The U-shaped pipe 23 and the side plate 24 are provided.

The inner surface of the heat transfer tube 21 used in this heat exchanger was initially smooth, but with the progress of thermodynamic research, it is better to form predetermined irregularities to improve the heat transfer coefficient. It has been found that recently, mainly the outer diameter is 4 mm to 10 mm.
The inner surface grooved tube in which the grooves having a substantially trapezoidal cross section on the inner surface of the heat transfer tube 21 and the fins 22 having a substantially triangular cross section separating the grooves are continuously formed in a spiral shape has become the main stream.

An example thereof is shown in FIG. 8A and 8B are views showing a conventional heat transfer tube for evaporation and condensation in a tube, FIG. 8A is a vertical sectional view, FIG. 8B is a lateral sectional view, and FIG. 8C is an enlarged view of part A shown in FIG. 8B. In FIG. 8A, H indicates the groove depth, and β indicates the angle (twist angle) with respect to the tube axis direction. The heat transfer tube 31 for vaporization and condensation in the tube has a spiral groove 33 and a spiral fin 34 which are continuous with the inner surface of the heat transfer tube body 32.

Such a spiral groove 33 and a spiral fin 34
By forming the, the surface area in the tube is increased and the heat transfer area is increased. In addition to that, high evaporation heat transfer coefficient and high condensation heat transfer coefficient can be obtained by promoting the turbulent flow effect and reducing the refrigerant liquid film thickness, so that the performance of the air conditioner, the heat pump and the like can be improved.

By the way, as shown in FIG. 6, during the heating operation and the cooling operation, the flow of the refrigerant flowing in the pipe is reversed. That is, as shown in FIG. 7, when the refrigerant condenses, it flows from the heat transfer tube 1 to the heat transfer tube 5 (from the bottom to the top in the figure), and conversely when it evaporates, from the heat transfer tube 5 to the heat transfer tube 1. Will flow (flow from top to bottom).

FIG. 9 shows the measured values of the condensation heat transfer coefficient in the heat transfer tubes 1 to 5 in these cases, FIG. 10 shows the measured values of the evaporation heat transfer coefficient, and FIG. 10 shows the measured values of the evaporation pressure loss. 11 shows. Table 1 below shows the measurement conditions of the refrigerant at this time, and Table 2 below shows the specifications of the two kinds of inner grooved tubes having different twist angles.

[0010]

[Table 1]

[Table 2] From this result, when the twist angle of the inner grooved tube is increased, the effect of stirring the refrigerant is increased, the condensation heat transfer rate is improved, and the performance of the heat exchanger can be improved. That is, as shown in FIG. 9, an inner grooved tube with a large helix angle (β: 35 degrees)
Shows a higher condensation heat transfer coefficient than the inner grooved tube (β: 16 degrees) with a small twist angle, and it is possible to improve the performance of the heat exchanger by increasing the twist angle of the heat transfer tube. Becomes

[0011]

However, in the conventional heat exchanger for air conditioning, when the refrigerant evaporates in the heat exchanger, the evaporation heat transfer coefficient is slightly lowered as shown in FIG. As a larger problem, as shown in FIG. 11, the evaporation pressure loss increases due to an increase in the twist angle. Due to this increase in pressure loss, there is a problem that the capacity of the heat exchanger when the refrigerant evaporates is significantly reduced.

As shown in FIG. 11, vaporization pressure loss in the outlet side, the heat transfer tube 1 and the vicinity of the heat transfer tube 2 becomes large, especially during evaporation of the refrigerant, so it is necessary to reduce the pressure loss in this portion.

Further, as described above, the method of increasing the twist angle to increase the condensation heat transfer coefficient can improve the capacity of the heat exchanger when the heat exchanger is used only as the condenser. However, when applied to a refrigeration cycle that also serves as a cooling and heating system as shown in FIG. 6, when the refrigerant is evaporated in the heat exchanger, the pressure loss increases and the capacity of the heat exchanger during evaporation operation decreases. There is a problem.

The present invention has been made in view of the above point, and by appropriately arranging two or more types of heat transfer tubes having different twist angles, the increase in refrigerant pressure loss during evaporation can be suppressed, Moreover, it is an object of the present invention to provide a heat exchanger capable of improving the capacity at the time of condensation.

[0015]

In order to solve the above problems, the heat exchanger according to the present invention is a refrigerant in a pipe in which a groove is spirally formed on the inner surface of the pipe at an arbitrary helix angle with respect to the axis of the pipe. In a heat exchanger having a heat transfer tube that exchanges heat by condensing or evaporating, and a fin in which this heat transfer tube is inserted, a plurality of heat transfer tubes having different twist angles are connected, and a plurality of the connected plurality of heat transfer tubes are connected. The heat transfer tube, on the side of the dryness of the refrigerant is small,
It is characterized in that a heat transfer tube having a larger twist angle than that on the dry side is arranged.

In the heat exchanger of the present invention, heat transfer is carried out by condensing or evaporating the refrigerant in the tube having a spiral groove formed on the inner surface of the tube at a predetermined twist angle with respect to the axis of the tube. In a heat exchanger having a heat pipe and a fin into which the heat transfer pipe is inserted, two types of heat transfer pipes having different twist angles are connected to each other, and the two kinds of connected heat transfer pipes have a dryness of the refrigerant. It is characterized in that a heat transfer tube having a larger twist angle of 10 degrees or more is arranged on the smaller side than on the side having a higher dryness.

Further, in the heat exchanger of the present invention, heat transfer is carried out by condensing or evaporating the refrigerant in the tube having a spiral groove formed on the inner surface of the tube at a predetermined twist angle with respect to the axis of the tube. In a heat exchanger having a heat pipe and a fin into which the heat transfer pipe is inserted, three types of heat transfer pipes having different twist angles are connected to each other, and the three types of connected heat transfer pipes have a dryness of the refrigerant. It is characterized in that a heat transfer tube having a larger twist angle of 10 degrees or more is arranged on the smaller side than on the side having a higher dryness.

The outer diameter of the heat transfer tube is 4 to 10 mm,
The groove formed on the inner surface has a depth of 0.1 to 0.3 mm.

The difference in groove depth between the heat transfer tubes having different twist angles is 0.04 mm or less.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment) FIG. 1 is a diagram showing a configuration of a heat exchanger according to an embodiment of the present invention, (a) is a side view and (b) is a front view.

The heat exchanger shown in FIG. 1 is applied to an air conditioner, a heat pump, etc., and has a heat transfer tube 21a.
, A fin 22 that exchanges heat with an external fluid, a U-shaped pipe 23, and a side plate 24. Further, the heat transfer tubes 21a have inner grooved tubes having a small helix angle (shown in the conventional example) on the heat transfer tube 1 and the heat transfer tube 2 on the side having a high degree of dryness (described later), that is, when the refrigerant condenses. Using the inner grooved tube with a helix angle of 16 degrees in Table 2), the inner grooved tube with a large helix angle (the helix angle of 35 degrees in Table 2) is used for the heat transfer tubes 3, 4, and 5 on the dry side. Inner grooved tube).

However, the dryness is the ratio of the mass flow rate of the gas phase to the total mass flow rate when the gas and the liquid are mixed and flowing, and when the gas is completely gas, the dryness is 1 and the dryness is completely liquid. When the dryness is 0.

The measured values of the condensation heat transfer coefficient in the heat transfer tubes 1 to 5 are shown in FIG. 2, the measured values of the evaporation heat transfer coefficient are shown in FIG. 3, and the measured values of the evaporation pressure loss are shown in FIG. Shown in. 2 to 4, the performance of the heat exchanger according to this embodiment is shown in black.

In the condensation heat transfer coefficient shown in FIG. 2, the heat transfer tubes having a large twist angle are used for the heat transfer tube 1 and the heat transfer tube 2 which have a high degree of dryness. The average value of the condensing heat transfer coefficients of the heat transfer tubes 1 to 5 is lower than that when the heat transfer tubes 1 to 5 are used. However, since the heat transfer tube 2 is a region where the refrigerant starts to condense, the condensation heat transfer coefficient of the refrigerant is very high, and the difference from the heat transfer coefficient of the external fluid becomes very large, so that this portion (heat transfer tube 2) The heat transfer coefficient is affected by the heat transfer coefficient of the external fluid, and the effect of improving the heat transfer coefficient in the tube is reduced. Therefore, in the heat exchanger according to the present embodiment, the capacity of the heat exchanger at the time of condensation can be improved as compared with the case where all the heat transfer tubes (β16 degrees) having a small twist angle are used.

Further, since the pressure loss at the time of condensation is smaller than that at the time of evaporation, the influence on the heat exchanger is small. Regarding the evaporation pressure loss in FIG. 4, the heat transfer tubes 1 and 2 on the refrigerant outlet side at the time of evaporation have a large twist angle (β35).
However, in the heat exchanger according to the present embodiment, since the heat transfer tubes 1 and 2 are heat transfer tubes with a small twist angle (β16 degrees), The pressure loss can be almost the same as when using a heat transfer tube (β16 degrees) with a small twist angle.

Regarding the heat transfer coefficient of evaporation shown in FIG. 3, in the heat exchanger according to this embodiment, the heat transfer coefficient of evaporation is almost the same as when the inner grooved tube (β35) having a large helix angle is used. However, the pressure loss can be reduced as described above. In other words, by using a heat transfer tube with a small twist angle in the part of the heat transfer tube with a high pressure loss during evaporation and a high dryness, and using a heat transfer tube with a large twist angle in the heat transfer tube with a small pressure loss and a low dryness A low-pressure loss, high-performance heat exchanger can be constructed.

Further, as in the present embodiment, if the difference between the twist angles of the two types of heat transfer tubes is 10 degrees or more, a low-pressure loss, high-performance heat exchanger can be constructed. If the difference in the twist angle is less than 10 degrees, the effect of improving the low pressure loss and high performance of the heat exchanger is small, and considering the labor of using two types of heat transfer tubes in manufacturing the heat exchanger, the twist angle of the grooved tube is considered. Difference of 10
A degree or more is desirable.

In the method for manufacturing the heat exchanger for air conditioning shown in FIG. 1, usually, the heat transfer tube 21a is inserted into the fin 22, and a jig having a diameter larger than the inner diameter is inserted into the heat transfer tube 21a.
By expanding 1a, the fins 22 and the heat transfer tubes 21
Make a close contact with a. Therefore, if several kinds of heat transfer tubes having different twist angles have the same inner diameter, the same pressing and expanding jig can be used, and the manufacturability is improved. Since the bottom wall thickness of the inner grooved tube is determined by the design pressure for each refrigerant, if the difference in groove depth is within 0.04 mm, the same pushing jig can be used.

The configuration of the heat exchanger according to the other embodiment is shown in a side view in FIG. 5, and its description will be given. The heat exchanger shown in FIG. 5 is composed of two rows of heat exchangers and one row of heat exchangers. The two rows of heat exchangers are fitted with the inner grooved pipes 35 whose specifications are shown in Table 3 below, and the one row of the heat exchangers are fitted with the inner grooved pipes 36 shown in the same table 3. Also in this other embodiment, the same effect as the above embodiment can be obtained.

[0031]

[Table 3]

As described above, according to the present invention,
A heat transfer tube that performs heat exchange by condensing or evaporating the refrigerant in the tube, which has spiral grooves formed on the inner surface of the tube at a predetermined twist angle with respect to the axis of the tube, and a fin into which the heat transfer tube is inserted. When configuring the heat exchange having, a plurality of heat transfer tubes having different twist angles are connected, and in the connected plurality of heat transfer tubes, the side with a smaller degree of dryness of the refrigerant has a greater twist angle than the side with a greater degree of dryness. Since a heat transfer tube with a large heat transfer tube is arranged, by appropriately deciding the arrangement of two or more types of heat transfer tubes with different twist angles, it is possible to reduce the increase in refrigerant pressure loss during evaporation and to reduce the capacity during condensation. Can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a heat exchanger according to an embodiment of the present invention.

FIG. 2 is a diagram showing measured values of the condensation heat transfer coefficient in the heat transfer tubes 1 to 5 of the heat exchanger.

FIG. 3 is a diagram showing measured values of evaporative heat transfer coefficients in heat transfer tubes 1 to 5 of the heat exchanger.

FIG. 4 is a diagram showing measured values of evaporation pressure loss inside the heat transfer tubes 1 to 5 of the heat exchanger.

FIG. 5 is a diagram showing a configuration of a heat exchanger according to another embodiment.

FIG. 6 is a diagram showing a conventional refrigeration cycle such as an air conditioner and a heat pump.

FIG. 7 is a diagram showing a configuration of a heat exchanger used in a conventional air conditioner, a heat pump, and the like.

FIG. 8 is a view showing heat transfer tubes for in-tube evaporation and condensation in a conventional heat exchanger.

FIG. 9 is a diagram showing measured values of condensation heat transfer coefficients in the heat transfer tubes 1 to 5 of the conventional heat exchanger.

FIG. 10 is a diagram showing measured values of the evaporation heat transfer coefficient in the heat transfer tubes 1 to 5 of the conventional heat exchanger.

FIG. 11 is a diagram showing measured values of evaporation pressure loss in the heat transfer tubes 1 to 5 of the conventional heat exchanger.

[Explanation of symbols]

10 Refrigerant flow during cooling operation 11 Refrigerant flow during heating operation 12 compressor 13 Indoor heat exchanger 14 outdoor heat exchanger 15 Expansion valve 16 four-way valve 21,21a Heat transfer tube 22 fins 23 U type pipe 24 Side plate 31 Inner grooved pipe 32 Heat transfer tube body 33 spiral groove 34 spiral fin 35 Inner grooved pipe with small twist angle 36 Inner grooved tube with large helix angle

Claims (5)

[Claims] 1. A heat transfer tube for exchanging heat by condensing or evaporating a refrigerant in a tube in which a spiral groove is formed on the inner surface of the tube at an arbitrary twist angle with respect to the axis of the tube, and the heat transfer tube is inserted. In a heat exchanger having a fin, the plurality of heat transfer tubes having different twist angles are connected to each other, and the plurality of connected heat transfer tubes are arranged on a side having a low degree of dryness of the refrigerant, from a side having a high degree of dryness. Also, a heat exchanger characterized in that a heat transfer tube having a large twist angle is arranged. 2. A heat transfer tube for heat exchange by condensing or evaporating a refrigerant in a tube in which a spiral groove is formed on the inner surface of the tube at a predetermined twist angle with respect to the axis of the tube, and the heat transfer tube is inserted. In the heat exchanger having the fins, the two kinds of heat transfer tubes having different twist angles are connected, and the two kinds of connected heat transfer tubes have a high degree of dryness on the side of the refrigerant having a low degree of dryness. A heat exchanger characterized in that a heat transfer tube having a twist angle larger than that of the side by 10 degrees or more is arranged. 3. A heat transfer tube for heat exchange by condensing or evaporating a refrigerant in a tube having a spiral groove formed on the inner surface of the tube at a predetermined twist angle with respect to the axis of the tube, and the heat transfer tube being inserted. In the heat exchanger having the fins, the three types of heat transfer tubes having different twist angles are connected, and the three types of connected heat transfer tubes have a high degree of dryness on the side of the refrigerant having a low degree of dryness. A heat exchanger characterized in that a heat transfer tube having a twist angle larger than that of the side by 10 degrees or more is arranged. 4. The outer diameter of the heat transfer tube is 4 to 10 mm, and the depth of the groove formed on the inner surface of the heat transfer tube is 0.1 to 0.3 mm. The heat exchanger described. 5. The heat exchanger according to claim 1, wherein a difference in groove depth between the heat transfer tubes having different twist angles is 0.04 mm or less.