JP3417825B2 - Inner grooved pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a room air conditioner and the like.
Suitable for heat exchangers, for example, with internal grooves made of copper or copper alloy
The present invention relates to a pipe, and more particularly, to a pipe with an inner groove which is reduced in weight. [0002] 2. Description of the Related Art Recently, a room air conditioner is used for both cooling and heating.
Type heat pump air conditioners are the mainstream. Soshi
Copper or copper used for this heat pump type air conditioner
Copper alloy heat transfer tube has excellent evaporation and condensation performance
Is required. To improve the evaporation performance of heat transfer tubes
Spreads the refrigerant liquid over the entire inner surface of the pipe, which is the heat transfer surface.
A structure is required so that the refrigerant evaporates in the body. one
On the other hand, in order to improve the condensation performance of the heat transfer tube,
Refrigerant liquid to prevent it from being covered with
It is necessary to have a structure that prevents it from spreading over the entire inner surface of the pipe.
Is done. Therefore, transmission with excellent evaporation performance and condensation performance
In order to obtain a heat tube, a structure that satisfies the aforementioned conflicting characteristics
Is required. Therefore, such a heat transfer tube has a spiral inside the tube.
Of multiple parallel grooves to improve heat transfer efficiency
Surface grooved tubes are used. And this inner grooved tube
Weight per unit length in the pipe axis direction (hereinafter referred to as single weight
To reduce the cost of heat exchangers.
Is being used. For example, a lightweight inner grooved pipe is
JP-A-5-1891 and JP-A-5-79783
Information has been proposed. Described in JP-A-5-1891
In the grooved inner grooved pipe, the groove depth is
Ratio, torsion angle of groove to pipe axis, groove cross section to groove depth
By specifying the product and the fin's peak angle,
Higher performance and lighter weight of the tube. On the other hand, it is described in Japanese Patent Application Laid-Open No. 5-79783.
The inner diameter of the grooved pipe,
Torsion angle, ratio of groove depth to pipe inner diameter, pipe wall thickness, groove
Defines the width of the groove bottom with respect to the depth and the peak angle of the fin
By improving the performance and weight of the internally grooved tube,
I have. In addition, a plurality of parallel pipes crossing each other on the inner surface of the pipe.
An internally grooved tube with a groove has been proposed.
3-148078). Inner surface described in this publication
In a grooved pipe, grooves that cross each other are formed on the inner surface of the pipe.
The inner surface of the tube has a plurality of square pyramid-shaped protrusions.
Has been established. By adopting such a shape,
The heat transfer performance is improved compared to the inner grooved tube up to. [0006] However, the above-mentioned problem is not solved.
Reducing single weight and maintaining heat transfer performance with conventional inner grooved tubes
Is not enough. [0007] Japanese Patent Application Laid-Open No. 5-1891 discloses
In a surface grooved pipe, the ratio of the groove depth to the pipe inner diameter is set to 0.1.
Defined as 02 to 0.03, fins are high and single weight
Is not enough. Further, it is described in JP-A-5-79783.
In the grooved inner grooved pipe, the groove depth is
The ratio is defined as 0.023 to 0.025,
And the reduction of simple weight is not enough. On the other hand, the ratio of the groove depth to the inner diameter of the pipe is simply reduced.
With a lower setting, the fins are lower and the heat transfer performance is lower.
I will drop it. Further, Japanese Utility Model Application Laid-Open No. Sho 63-148078 discloses
Even with the described inner grooved pipe, the reduction of single weight is sufficient
is not. The present invention has been made in view of such a problem.
Therefore, the simple weight can be reduced without reducing the heat transfer performance.
With the aim of providing an inner grooved tube that can be reduced
I do. [0012] SUMMARY OF THE INVENTION According to the present invention, there is provided an inner grooved tube.
Is inclined in the pipe axis direction on the pipe inner surfaceOneSpiral extending in the direction
Inner grooved tube formed with a plurality of parallel grooves in a shape,Said
The grooves form fins that are separated from each other by the grooves.
The tubeThe maximum inner diameter is Di, formed between the grooves.
The height of the fin is Hf, the width of the base of the fin is Wf,
The torsion angle between the direction in which the groove is formed and the tube axis
θ, when the groove pitch in the circumferential direction of the groove is P,
Where Hf / Di is 0.01 to 0.02 and θ / Di is
2.0 to 4.5, Hf / Wf is less than 1.6, P is 0.2.
It is 35 to 0.45 (mm). In the present invention, the groove formed on the inner surface of the tube
The shape is specified as appropriate, so it is
Single weight without deteriorating evaporation and condensation performance
Can be reduced. [0014] DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have solved the above-mentioned problems.
As a result of intensive experimentation and research, the maximum inner diameter Di
Ratio Hf / Di of fin height Hf to maximum diameter D
ratio of the helix angle θ of the spiral groove to the pipe axis with respect to i / θ / D
i, the ratio H of the height of the fin to the width Wf of the base of the fin, H
By defining f / Wf and groove pitch P to appropriate values,
Of copper or copper alloy without deteriorating heat transfer performance
Finding that the simple weight of a surface grooved tube can be reduced
did. Hereinafter, the number of the inner grooved pipe according to the present invention will be described.
The reason for limiting the value will be described. Fig. 1 shows the maximum internal grooved pipe.
Inner diameter Di, fin height Hf, fin base width Wf
FIG. 2 is a schematic sectional view illustrating a position corresponding to a groove pitch P.
is there. The inner surface of the inner grooved pipe 1 is inclined with respect to the pipe axis direction.
DoOneSpiral grooves 2 extending in the direction are formed at regular intervals
Have been. Thereby, a mountain shape is formed between the adjacent grooves 2.
Fins 3 are formedAnd the fins 3 are
Separated from each other. That is, the base of adjacent fins 3
The parts do not contact each other, but are separated from each other by the bottom 4 of the groove 2.
Separated.Here, the maximum inner diameter Di is the bottom of the groove 2
The distance from 4 to the pipe axis (not shown) is doubled.
You. Also, the fin height Hf is determined by whether the top 5 of the fin 3
From the pipe axis to a cylindrical surface with a radius of (Di / 2)
Is the distance. The width of the base of the fin is the base of the fin 3
Is the distance between both side surfaces 6. And the groove pitch P
Is the distance between adjacent fins 3 on the cylindrical surface.
When the number of grooves in the pipe circumferential direction is m, (π × Di / m)
Is represented by FIG. 2A shows the relationship between the torsion angle θ of the inner grooved pipe.
FIG. 4 is a schematic perspective view illustrating a corresponding position, and FIG.
FIG. Twist of spiral groove with respect to pipe axis
The angle θ means that the inner grooved pipe 1 is cut along an incision 7 parallel to the pipe axis.
When it is cut open, the direction of the pipe axis and the direction in which the groove 2 extends
Angle. [0017]Of the fin height Hf with respect to the maximum inner diameter Di
Ratio Hf / Di: 0.01 to 0.02 The present inventors have determined that the fin height H with respect to the maximum inner diameter Di.
The relationship between the ratio ff / Di of f and the heat transfer coefficient of evaporation was investigated.
The result is shown in FIG. FIG. 3 shows the ratio Hf / Di on the horizontal axis.
The vertical axis shows the heat transfer coefficient in the pipe during evaporation to show the relationship between the two.
FIG. In the measurement of the heat transfer coefficient in the pipe,
Two kinds of inner grooved pipe with outer diameter of 7mm or 9.52mm
R22 was used as a refrigerant. R22 is the United States
This is the name given by the Japan Society of Heating, Refrigeration and Air Conditioning (ASHRAE).
And the chemical formula CHF_TwoCl-based refrigerant represented by Cl
You. The length of the inner grooved tube is 3m with an outer diameter of 7mm,
It is 4 m with an outer diameter of 9.52 mm. Also, if the outside diameter is
Refrigerant flow rate when using 7mm inner grooved pipe is 30k
g / h, using an internally grooved tube with an outer diameter of 9.52 mm
The refrigerant flow rate at this time is 40 kg / h.
Furthermore, the evaporation temperature is 7.5 ° C, the temperature before the expansion valve is 40 ° C,
Mouth superheat is 5 ° C. In FIG. 3, the solid line indicates that the outer diameter is 7
The results are shown for an internally grooved tube with an outer diameter of 9.52 mm.
4 shows the results for an internally grooved tube of mm. The height Hf of the fin with respect to the maximum inner diameter Di
When the ratio Hf / Di is less than 0.01, as shown in FIG.
In addition, the heat transfer coefficient of evaporation is extremely low. This is the fin height
Is extremely low, the capillary phenomenon does not occur and the refrigerant liquid diffuses.
The effect is almost lost and the refrigerant liquid reaches the top of the pipe
This is because it does not spread wet. On the other hand, the ratio Hf / Di is
If it exceeds 0.02, the single weight is reduced compared to the conventional product.
I can't. Therefore, the filter for the maximum inner diameter Di
The ratio Hf / Di of the height Hf is 0.01 to 0.02.
I do. [0019]Spiral groove for the maximum inner diameter Di
Ratio of twist angle θ / Di: 2.0 to 4.5 The inventors of the present application have stated that the pipe shaft of the spiral groove with respect to the maximum inner diameter Di
Torsion angle θ / Di, heat transfer coefficient of evaporation, heat of condensation
The relationship between transmissibility and pressure loss was investigated. Fig.
4 (a) and (b) and FIG. FIG. 4 (a) and
(B) shows the ratio θ / Di on the horizontal axis and the heat transfer coefficient in the pipe on the vertical axis.
(A) shows the ratio θ / Di and the tube at the time of evaporation.
FIG. 4B is a graph showing the relationship with the internal heat transfer coefficient, and FIG.
FIG. 6 is a graph showing the relationship between i and the heat transfer coefficient in a pipe during condensation.
You. The measurement conditions for the heat transfer coefficient in the pipe during evaporation are the same as those described above.
It is like. In the measurement of the heat transfer coefficient in the pipe during condensation,
Use the same inner grooved pipe and refrigerant as described above, and set the condensation temperature to 4
5 ° C., the inlet temperature was 70 ° C., and the outlet subcooling degree was 5 ° C.
4 (a) and 4 (b), the solid line indicates that the outer diameter is 7 mm.
The result of the inner grooved tube of mm is shown.
The result of an inner surface grooved tube is shown. As shown in FIG. 4A, the ratio θ / Di is about
When it is 2.0, the heat transfer coefficient of evaporation is maximum.
To make the refrigerant easily spread over the entire inner surface of the pipe, the groove is
Spiral extending in the direction inclined to the tube axis
Have been. However, if the twist angle θ becomes excessively large,
The gravity component of the force acting on the refrigerant increases,
The upper part of the tube is difficult to spread and spread,
Delivery rate decreases. As shown in FIG. 4B, the ratio θ / D
Although the condensed heat transfer coefficient increases with increasing i, the ratio θ / D
Almost saturated when i reaches around 4.5. Coagulation
In order to improve the heat transfer coefficient, the case of evaporation heat transfer rate
Conversely, it is necessary to reduce the wetting and spreading properties of the refrigerant.
You. The gaseous refrigerant flowing into the inner grooved pipe generates heat on the inner wall of the pipe.
It is deprived and condensed to become liquid, but spreads wet
In the case of high performance, the liquefied refrigerant covers the inner surface of the tube. And
Refrigerant itself acts as thermal resistance, lowering the condensation heat transfer coefficient
Resulting in. For this reason, the top of the tube is always dry.
To condense the gaseous refrigerant, and the liquefied refrigerant flows through the bottom of the tube.
Is desirable. As described above, the twist angle θ increases.
And the refrigerant hardly spreads over the upper part of the pipe,
It becomes possible to form a dry area in the part. But,
Even if the torsion angle θ is increased,OrthogonalCross section
Does not increase the area of the region where the refrigerant can flow
Therefore, there is an upper limit on the area of the dry region. others
Therefore, as shown in FIG. 4B, the improvement of the ratio θ / Di is saturated.
There exists a torsion angle θ. FIG. 5 shows the ratio θ / Di on the horizontal axis and steam ratio on the vertical axis.
FIG. 4 is a graph showing the relationship between the pressure loss at the time of power generation and the two.
You. The measurement conditions are the same as those described above. In FIG.
In addition, the solid line shows the result of an inner grooved tube with an outer diameter of 7 mm.
The dashed line shows the result for a 9.52 mm internally grooved tube.
You. When the torsion angle θ is increased in the inner grooved pipe,
As shown in FIG. 5, the pressure loss increases accordingly.
As the pressure drop increases, the heat exchanger inlet temperature rises during evaporation.
As the temperature rises, the temperature difference between the air and the refrigerant becomes smaller. For this reason,
The heat transfer coefficient of evaporation decreases. From the above, when the evaporation performance is important,
When the ratio θ / Di is set to about 2.0,
When the ratio θ / Di is set to about 4.5,
Performance can be obtained. However, recent room airco
Air conditioners are mainly used for
High evaporation performance and high condensation performance are required for the attached pipe.
Therefore, the spiral groove with respect to the maximum inner diameter Di
The ratio θ / Di of the skew angle θ is set to 2.0 to 4.5. [0025]Fin height relative to fin base width Wf
Hf ratio Hf / Wf: less than 1.6 The inventors of the present invention have proposed a fin having a width Wf at the base of the fin.
Height Hf ratio Hf / Wf and fin inclination angle after expansion
The relationship was investigated. The result is shown in FIG. Fig. 8 is the horizontal axis
And the vertical axis represents the inclination angle of the fin after expansion.
FIG. 2 is a graph showing the relationship between the two. FIG.
FIG. 4 is a schematic cross-sectional view illustrating a fin inclination angle の. What
In the measurement of the fin inclination angle after expansion, first,
Insert the expansion brit attached to the end of the barrel into the grooved pipe on the inside.
Into the inner grooved tube and expand the inner grooved tube to fin the inner grooved tube.
Adhered to the material. Next, as shown in FIG.
The direction 8 in which the inclined fins protrude and the radial direction 9 make
The angle was measured as the inclination angle ξ. Fin height relative to fin base width Wf
FIG. 8 shows that the ratio Hf / Wf of the height Hf is 1.6 or more.
As shown in FIG. In addition, the expansion
The fins are easily crushed. Thus, the inclination angle ξ is high
If the fins collapse or the fins collapse, the heat transfer performance of the inner grooved tube will increase.
May not be demonstrated. Therefore, the width W of the base of the fin
The ratio Hf / Wf of the fin height Hf to f is less than 1.6.
Be full. [0027]Groove pitch P: 0.35 to 0.45 (m
m) The present inventors have determined that the groove pitch P, the evaporation heat transfer coefficient, the condensation heat transfer
The relationship between delivery rate and single weight was investigated. The result is shown in FIG.
(A) and (b) and FIG. FIG. 6 (a) and
(B) shows the groove pitch P on the horizontal axis and the heat transfer coefficient in the pipe on the vertical axis.
(A) shows the groove pitch P and the tube at the time of evaporation.
FIG. 3 is a graph showing a relationship with an internal heat transfer coefficient, and FIG.
FIG. 4 is a graph showing the relationship between P and the heat transfer coefficient in the pipe during condensation.
You. The measurement conditions for the heat transfer coefficient in the pipe are the same as those described above.
You. FIG. 7 shows the groove pitch P on the horizontal axis and the unit weight on the vertical axis.
It is a graph which shows the relationship between both by taking quantity. The figure
6 (a) and (b) and FIG. 7, the solid line indicates the outer diameter.
The result of a 7 mm internally grooved tube is shown, and the broken line is 9.52 mm.
3 shows the result of the inner grooved tube. When the groove pitch P is less than 0.35 mm,
Since the width of the groove becomes extremely narrow, as shown in FIG.
In addition, the heat transfer coefficient of evaporation is extremely low. Also, as shown in FIG.
In addition, the unit weight increases. On the other hand, the groove pitch is 0.45 mm
When the pressure exceeds the surface area, the surface area of the inner surface of the pipe is reduced.
As shown in (b), the condensation heat transfer coefficient becomes extremely low.
Therefore, the groove pitch P is 0.35 to 0.45 (mm).
I do. The inner grooved tube is made of copper or copper alloy.
It is not limited. For example, aluminum or aluminum
The inner grooved tube made of a ruminium alloy may be used. [0030] EXAMPLES Examples of the present invention will be described below with reference to comparative examples.
This will be described more specifically with reference to FIG. First, grooves having the shapes shown in Tables 1 and 2 below are provided.
An inner grooved tube was prepared. The groove of each inner grooved pipe
Thickness is 0.28mm, outer diameter is 9.52mm, length
The height is 4 m. [0032] [Table 1] [0033] [Table 2]Next, in each of Examples and Comparative Examples,
R22 was used as the refrigerant, and the flow rate of this refrigerant was 40 kg / h.
The heat transfer coefficient of evaporation and the heat transfer coefficient of condensation were measured. Ma
In addition, the single weight and the inclination angle の of the fin after expansion were also measured.
The test material for measurement was expanded at a 105% expansion rate.
It was a thing. The expansion ratio is (outer diameter after expansion) /
(Outer diameter before expansion) × 100. This
The results are shown in Table 3 below. When measuring the heat transfer coefficient of evaporation, the evaporation temperature
7.5 ° C, temperature before expansion valve 40 ° C, outlet superheat 5 ° C
And On the other hand, when measuring the condensation heat transfer coefficient,
Shrink temperature 45 ° C, inlet temperature 70 ° C, outlet subcooling degree 5
° C. The results are shown in Table 3 below. Table 3
The heat transfer coefficient of evaporation and heat transfer of condensation are
Using the value of Comparative Example 3 as the reference value 1.00,
is there. [0037] [Table 3] As shown in Table 3 above, in Example 1,
Is not suitable because the groove shape of the inner grooved pipe is appropriate.
Significantly reduced unit weight while maintaining the same performance as the product
I was able to. In the second embodiment, the inner grooved pipe is used.
Since the groove shape of the
And the heat transfer coefficient of evaporation and heat transfer of condensation
Could be improved. On the other hand, in Comparative Example 4, the groove pitch P was
Since it is less than the lower limit of the range of the present invention, the heat transfer coefficient of evaporation is low.
Was. In Comparative Example 5, the groove pitch P was changed according to the present invention.
Since the upper limit of the range is exceeded, the heat transfer coefficient,
Delivery rate was low. In Comparative Example 6, the ratio Hf / Di
Simple weight is reduced because it is below the lower limit of the light range
However, the evaporative heat transfer coefficient and condensed heat transfer coefficient are extremely low.
Was. In Comparative Example 7, the ratio θ / Di was determined according to the present invention.
Since it was below the lower limit of the range, the condensation heat transfer coefficient was low. In Comparative Example 8, the ratio Hf / Wf was
Fin inclination after expansion because it exceeds the upper limit of the light range
The angle ξ has increased significantly. For this reason, the heat transfer coefficient, especially
The heat transfer coefficient of evaporation was low. [0044] As described in detail above, according to the present invention,
The shape of the groove formed on the inner surface of the pipe is specified as appropriate.
Therefore, heat transfer performance should not be reduced compared to conventional products.
Simple weight can be reduced. This allows for heat exchange
The cost of the vessel can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the maximum inner diameter Di of the inner grooved tube and the height H of the fin.
FIG. 5 is a schematic cross-sectional view illustrating a position corresponding to f, a peak angle α of a fin, and a groove pitch P. 2A is a schematic perspective view illustrating a position corresponding to a twist angle θ of an inner grooved pipe, and FIG. 2B is a schematic cross-sectional view of the same. FIG. 3 is a graph showing the relationship between the ratio Hf / Di on the horizontal axis and the heat transfer coefficient in the pipe during evaporation on the vertical axis. FIG. 4A is a graph showing a relationship between a ratio θ / Di and a heat transfer coefficient in a pipe during evaporation, and FIG. 4B is a graph showing a relation between the ratio θ / Di and a heat transfer coefficient in a pipe during condensation. FIG. FIG. 5 is a graph showing a relationship between a ratio θ / Di and a pressure loss during evaporation. 6A is a graph showing the relationship between the groove pitch P and the heat transfer coefficient in the pipe during evaporation, and FIG. 6B is a graph showing the relation between the groove pitch P and the heat transfer coefficient in the pipe during condensation. is there. FIG. 7 is a graph showing the relationship between the groove pitch P on the horizontal axis and the simple weight on the vertical axis. FIG. 8 is a graph showing the relationship between the ratio Hf / Wf and the inclination angle の of the fin after expansion. FIG. 9 is a schematic cross-sectional view illustrating a fin inclination angle ξ. [Description of Signs] 1; inner grooved tube 2; groove 3; fin 4; bottom 5; top 6; side surface 7;

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-11891 (JP, A) JP-A-56-113998 (JP, A) JP-A-9-101093 (JP, A) JP-A-5-113 79783 (JP, A) Actually open 1988-64-148078 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F28F 1/40 F28F 1/42

Claims (1)

(57) [Claim 1] In an inner grooved pipe in which a plurality of spiral parallel grooves extending in one direction inclined in the pipe axis direction are formed on the inner surface of the pipe, the groove is provided between the grooves. Grooves separated from each other by grooves
The maximum inner diameter of the pipe is Di, the height of the fins formed between the grooves is Hf, the width of the base of the fins is Wf, and the direction in which the grooves are formed and the pipe axis direction. Assuming that the formed torsion angle is θ and the groove pitch in the circumferential direction of the groove is P, Hf / Di is 0.01 to 0.02, θ / D
i is 2.0 to 4.5, Hf / Wf is less than 1.6, and P is 0.35 to 0.45 (mm).