JP2020109329A - Heat exchanger double tube - Google Patents

Abstract

To provide a heat exchanger double tube capable of adequately reducing the fluid resistance of fluid flowing between an inner tube having spiral ridges and an outer tube.SOLUTION: The heat exchanger double tube is formed with an inner tube 20 on which two-four circularly swollen ridges are spirally circulated and which is mounted in an outer tube 10 to actualize heat exchange between fluid flowing in a clearance 35 between the outer tube 10 and the inner tube 20 and fluid flowing in the inner tube. A height (Ha) of one of the ridges 21 is made a ratio of 8-26% higher than a height (Hb) of the other ridge 23, and the higher ridge 22 is made to abut on the outer tube inner peripheral face throughout the whole periphery.SELECTED DRAWING: Figure 2

Description

The present invention relates to a heat exchange double pipe for exchanging heat between a fluid flowing through a gap between an outer pipe and an inner pipe and a fluid flowing inside the inner pipe.

In a conventional heat exchanger of an air conditioner of an automobile, a spiral inner pipe in which a refrigerant sent from an evaporator flows is surrounded by an outer pipe to form a double pipe, and a liquid refrigerant from a compressor is provided in a gap between the inner pipe and the outer pipe. The heat exchange is locally performed with relatively high efficiency.
The applicant of the present invention, as shown in FIG. 1(C) of Patent Document 1 and the straight pipe portion of FIG. 1 of Patent Document 2, engraves spiral irregularities on the inner pipe and uses it on the outer pipe. We have proposed a double tube that is closely contacted with each other to improve contact efficiency and improve heat exchange efficiency.
By the way, when the applicant further studied this spiral double tube, the double tube has good contact efficiency, but the gap between the spiral inner tube and the outer tube becomes narrow, so that the fluid resistance is The issue of increasing numbers was raised. For example, when the resistance of the fluid flowing through the gap increases, a load is applied to a pressure-feeding device such as a compressor for pressure-feeding the fluid, and improvement in energy saving effect has been demanded.
Therefore, in order to solve this, for example, as shown in FIG. 3 and FIG. 8 of Patent Document 2, a slightly wide gap is provided between the spiral inner pipe and the outer pipe, and the refrigerant is allowed to flow in this gap. The passage resistance should be reduced.
However, if the gap between the inner pipe and the outer pipe is simply widened in this way, the refrigerant passes through the gap in a short time because the fluid resistance is reduced, and the contact time is lost. This raises the problem of reducing the exchange efficiency.

Patent No. 5995354 Patent No. 5709733 Patent No. 4350079 JP 2002-318083

The present invention has been made in order to solve the above problems, while reducing the resistance of the spiral flow swirling the gap between the outer tube and the inner tube, on the other hand, adverse effects such as shortening of the contact time resulting therefrom. This is to avoid and try to realize a double tube for heat exchange in which flow resistance and contact time are balanced.

In order to solve the above-mentioned problems, the double tube for heat exchange according to claim 1 of the present invention is an outer tube in which an inner tube formed by spirally circling a convex strip that bulges in an arc into two to four rows. In a double pipe for which heat is exchanged between the fluid flowing in the gap between the outer pipe and the inner pipe and the fluid flowing in the inner pipe, the height (Ha) of one of the ridges is set to The height (Hb) of the other ridges is increased at a rate of 8 to 26%, and the raised ridges are brought into contact with the inner peripheral surface of the outer pipe over the entire circumference.

In the double tube for heat exchange according to claim 2, the height (Wa) of the raised ridge is equal to the width (Wb) of the other ridge, and the radius of curvature (Ra) of the ridge is different. It is characterized in that it has an inferior arc shape smaller than the radius of curvature (Rb) of the ridge.

In the double tube for heat exchange according to claim 1 of the present invention, the number of spiral projections of the inner tube is two, three or four, and the height (Ha) of one of the projections is Ha. By increasing the height of other convex stripes (Hb) at a rate of 8 to 26%, the height difference (Hs) between one raised convex stripe and another convex shape lower than Since a large gap is formed, the overall fluid resistance can be reduced in proportion to the formed gap, and the load problem can be solved.
On the other hand, since the raised ridge is joined to the outer pipe in abutting state over the entire circumference, only one of the two ridges, three ridges, or four ridges extends from the inlet to the outlet. This eliminates the concern that the flow path to be closed will be blocked and the flow path resistance will be excessively reduced to reduce the thermal efficiency due to the short contact time.
In general, while eliminating the load on the pumping device caused by the magnitude of fluid resistance, it also eliminates the concern that it loses contact time and lowers heat exchange efficiency, resulting in a balanced working effect. be able to.
At this time, if the height (Ha) of one of the ridges is set to a high value at a rate of 8 to 26% with respect to the height (Hb) of the other ridges, the height difference of the separated spaces Is not too small and the contact efficiency of the spiral is not lowered by being too large, and the optimum gap effect can be obtained.

In the double tube for heat exchange according to claim 2, by making the radius of curvature (Ra) of the raised ridge smaller than the radii of curvature (Rb) of the other ridges, the lateral width ( Wa) can be made equal to the lateral width (Wb) of the other ridges, and the widths of the ridges consisting of two, three or four ridges can all be made uniform.
As a result, if the height (Ha) of the selected one strip is increased as it is, the lateral width of the convex strip is enlarged by the height and the fear that it is not aligned with the lateral width of other convex strips is eliminated. It is possible to obtain a stable and uniform flow by making the flow generated in the uniform flow path uniform and balanced.

It is a side view showing the state where the outer pipe of the double pipe of the present invention was longitudinally cut and the inner pipe was exposed. It is a cutting side view which shows the principal part of an outer pipe and an inner pipe. It is a vertical side view which shows the use condition connected to the connection pipe. It is a schematic diagram when determining a curvature radius.

The double pipe of the present invention is used, for example, as a heat exchanger of an air conditioner of an automobile, and is composed of an outer pipe 10 and an inner pipe 20 installed therein as shown in FIGS. An arcuate bulge is engraved in a spiral shape on the tube, and a gap is formed between the inner tube 20 and the outer tube 10 to surround the refrigerant in the inner tube flowing from the evaporator. The structure allows heat exchange with the liquid refrigerant from the compressor flowing through the gap.
An inflow pipe 13 is arranged at one end of the gap and an outflow pipe 14 is arranged at the other end thereof, and an inflowing fluid is introduced below the inflow pipe 13 and the outflow pipe 14 for guiding the inflowing fluid to the gap 35 of the air space portion 30. A space 31 and a lead-out space 32 for leading to discharge are formed.

The outer pipe 10 is provided with an inflow port 13 communicating with the inflow pipe 13 on one side and an outflow port 14a communicating with the outflow pipe 14 on the other end.
The form is a straight tube, the inner peripheral surface 11 of a flat surface is arranged on the inner side, and the end portions 12a and 12b are arranged on the left and right sides thereof so as to be fixed to the closing convex portions 25a, 25b of the inner pipe 20 described later, A closed space surrounded by the inner peripheral surface 11 and the left and right ends 12a and 12b is formed.

The inner pipe 20 is installed in the outer pipe 10 to form a gap 35 sandwiched between the outer pipe 10 and the inner pipe 20 in the closed space. An inlet 33 for taking in the fluid from is provided, and an outlet 34 is provided on the side of the outlet space 32 that serves as an outlet.

A ridge 21 is provided on the inner pipe 20. A ridge 21 adjacent to the ridge 21 and a gap 35 is formed between the ridge 21 and the inner peripheral surface 11 of the outer pipe 10. The ridges 21 spirally circulate around the inner pipe 20, and the ridges 21 form several lines to form a group of channels 36.
That is, in the form of a spiral, two-, three-,... spirals circulate in pairs to form a group of flow paths. For example, when the intake ports 33 from the introduction space 31 are three intake ports 33a, 33b, 33c, the ridges 22a, 22b, 22b are provided in correspondence with the three intake ports, and Three flow paths 36a, 36b, 36c are formed in the gaps 35a, 35b, 35c sandwiched between the strips, and three outlets 34a, 34b, 34c are correspondingly arranged.

In the present invention, this group of convex strips 21 is intended to be spirally wound over 2 to 4 strips.
The reason is that one-row is not effective for the present invention, and if the number of threads is five or more, the pitch of one spiral becomes large, the number of turns decreases and the flow resistance decreases, but on the other hand, the fluid flows out quickly. This is because the contact time becomes short.

In the two to four ridges, the present invention forms the height of one ridge 22 of the ridges higher than the height of the other ridge 23 which is lower, and The raised protrusion 22 is brought into contact with the inner peripheral surface of the outer pipe over the entire circumference.
For example, as shown in FIG. 3, when there are three ridges, the height Ha of one of the ridges 22a is 8 to 26% with respect to the height Hb of the other ridges 23a and 23b. Set a higher value.
As shown in the figure, there is a configuration in which one convex strip 22a1 and another convex strip 22a1 sandwich the other convex strips 23a and 23b, and the raised convex strip 22a extends over the entire circumference. When the pipe is also brought into contact with the inner peripheral surface 11, a closed space is formed between one of the ridges 22a1 and the next ridge 22a1 and a new gap 35 is formed therein. Becomes
That is, when the upper part of the ridge is the top part and the left and right sides thereof are the ridge parts and the other parts are the flat parts, the height difference Hs between the raised ridge top part 22a and the lower ridge part 23a of another ridge is increased to a new gap 35a. On the other hand, the conventional gap 35b is secured above the flat portions 24a, 24b, 24c and the peak portions 22a, 23a2, 23b2.
Then, these gaps 35 form a partitioned space partitioned by the convex line 22a1 of the previous round and the convex line 22a1 of the next round, and a new gap 35a created from the height difference in the partitioned space and a collateral. The gap 35 will be formed as the total of the gap 35b.

And at this time, the ratio Ha ((Ha-Hb)/Hb) of the height Ha of one convex strip 22a among the two to four convex strips to the height Hb of the other convex strips 23a, 23b, Set 8 to 26% higher.
This means that when the height of one ridge 22a is 8% or less of the height Hb of the other ridges 23a and 23b, the height difference between the separated spaces is small and the effect of the gap 35 is small. On the other hand, when it is 28% or more, the gap becomes excessively large and the contact efficiency due to the spiral is reduced, and the most suitable effect of the gap 35 is obtained in the range of 8 to 26%.

Specifically, when the outer diameter of the inner tube to be the flat portion is 16.0 mm, the diameter of the spiral top with the small protrusion as the apex is 18.3 mm, and the diameter of the top of the ridge is about 18.5 mm. In addition, the optimum gap size was 0.1 to 0.3 mm in the experiment by the applicant.
When this is ratioed, it corresponds to 8% to 26%.

In order to bring the tops 22a2 and 22a2 of the raised projections 22a1 into contact with the inner peripheral surface 11 of the outer tube, they are brought into close contact with each other, or a part of the top is crushed and placed in a pressure contact state. May be.

On the other hand, in the raised ridge, if the top is raised as it is, the lateral width of the ridge will follow up and it will be formed between the raised ridge and the adjacent ridge. It is pointed out that the width of the flat part is narrowed and the flat part becomes uneven as a whole.
Therefore, it is desirable to make the width of one ridge equal to the width of the ridge of another ridge while increasing the height of one ridge. The means will be described below.

As shown in FIG. 4, the height of the raised ridges is Ha, the height of the other ridges is Hb, the half width of the raised ridges is Wa, and the half width of the other ridges is Wb. The radius of curvature of the ridge is Ra, and the radii of curvature of the other ridges are Rb.
At this time, the right-angled triangle ΔAaNaCa including the height Ha and the lateral width Wa of the raised ridge and the right-angled triangle OaMaAa including the radius of curvature Ra are similar shapes in which θa is equal.
Therefore, ΔAaNaCa∽ΔOaMaAa is established.
Similarly, even in other convex stripes,
ΔAbNbCb∽ΔObMbAb holds.

Therefore, the following relational expression holds for the radius of curvature of the raised ridge and the radius of curvature of the other ridges Ra and Rb.
Ra=1/2·√(Wa ² +Ha ² )/sin θa... (1)
(However, θa=tan ⁻¹ Ha/Wa)
Rb=1/2·√(Wb ² +Hb ² )/sin θb (2)
(However, θb=tan ⁻¹ Hb/Wb)
That is, when a height difference between Ha and Hb is provided between the raised ridge and another ridge, the respective radii of curvature Ra and Rb have the above-described relationships (1) and (2).
At this time, when it is attempted to set the lateral widths of the raised ridges and the lateral widths of the other ridges equal, the relationship Wa=Wb is established.

From this relationship, for example, when the height Ha of the raised ridge and the height Hb of the other ridge, the lateral width Wb of the other ridge, and the radius of curvature Rb of the other ridge are already set, When the lateral width Wa of the raised ridge is made equal to the lateral width Wb of the other ridge (Wa=Wb) and the radius of curvature of the raised ridge is Ra, the above equation (1), The following relational expression can be derived from (2).
Ra=√(4Rb ² ·sin ² θb−Hb ² +Ha ² )/2sin θb ··· (3)
(However, θa=tan ⁻¹ Ha/Wa, θb=tan ⁻¹ Hb/Wb, Rb=½·√(Wb ² +Hb ² )/sin θb)

According to the formula (3), if the height Ha of the raised ridge, the height Hb of the other ridge, the half width Wb of the width of the other ridge, and the radius of curvature Rb of the other ridge are determined. , The radius of curvature Ra of the raised ridge can be correctly determined.

For example, the height Ha of the raised ridges is 1.4 mm, the height Hb of the other ridges is 1.2 mm, the lateral width Wa of the raised ridges is 8.87 mm, and the lateral widths of the other ridges are 8. When it is set equal to 0.87 mm, the result is as follows.
From equation (1) and θa=tan ⁻¹ Ha/Wa,
Rb=1/2·√(Wb ² +Hb ² )/sin θb
= 1/2/√(4.435 ² +1.2 ² )/sin 15.14
= 8.79 mm
Then, from equation (3) and θb=tan ⁻¹ Hb/Wb
Ra=√(4Rb ² sin θb−Hb ² +Ha ² )/2sin θb·
= 1/2/√(4.435 ² +1.4 ² )/sin 17.52
=7.72 mm
Is determined.

For example, if the width Fa of the flat surface on both sides of the raised ridge is 3.8 mm and the width Fb of the flat surface between the other ridges is 3.8 mm, the height of the raised ridge is as shown in the figure. A uniform flow path is formed in which the heights of the other ridges are different from each other and the lateral widths of the raised ridges are equal to the lateral widths of the other ridges and the intervals between the flat portions are also equal. Was confirmed.

The method for producing the double pipe is not limited, and for example, the inner pipe can be produced by expanding the pipe by hydraulic pressure and the outer pipe can be produced by reducing the pipe having a large diameter.
In addition, in order to form a joint that occurs at the apex of the outer tube and the ridge, the outer tube may be once made to have a large diameter, and the apex of the ridge may be partially crushed in the process of contracting the outer tube to bring it into a pressure contact state. The height of the ridge can be set to the required height by changing the size of the crush.
At this time, if the apexes of the ridges are partly crushed into a pressed state, the inner tube can be strongly fixed to the outer tube, and a centering effect on the outer tube can be obtained if necessary.

Next, the action and effect of the double pipe of the present invention including the above steps will be described.
First, when the fluid sent from the compressor reaches the introduction space 31 via the inflow pipe 13 and the inflow port 13a, it is guided to the intake port 33 facing this.
For example, when three intakes 33a, 33b, 33c are provided, they are connected to the gaps 35a, 35b, 35c formed between the protrusions 22a, 23a, 23b, 22a, and formed by the gaps. The flow paths 36a, 36b, 36c are connected to each other. Then, when this spirally turns, two turns, three turns, and so on are connected to form a group of flow paths.
Then, these flow paths form a relatively long spiral flow path that circulates the inner pipe 20, and thus come into long contact with the fluid in the inner pipe 20.

At this time, in the double pipe of the present invention, as described above, the space between the raised ridge 22a1 and the next raised ridge 22a1 is partitioned, and the raised ridge 22 and other lower ridges are formed. A gap 35 is formed between the gaps 23 and 23.
In this gap 35, a gap 35b is secured above the flat portion 23, and a new gap 35a is formed.
That is, first, the main flow of the introduced fluid is formed in the gap 35b secured above the flat portion 23, and the main flow circulates in the spiral path having a relatively long distance and flows into the inner pipe 20. Contact for a long time to promote efficient heat exchange.

Then, the height Ha of one protrusion 22a of the two to four protrusions is set to a high value at a rate of 8 to 26% with respect to the height Hb of the other protrusions 23a and 23b. Then, the height difference between the separated spaces is not too small, and the contact efficiency of the spiral is not excessively lowered to obtain the optimum gap effect.

Next, in the double pipe of the present invention, as described above, in addition to the gap 35b above the flat portion 23, the height difference Hs between the top portion 22a of the raised ridge 22 and the top portion 23a of another lower ridge 23 is generated. A new gap 35a is formed.
The new gap 35a increases the volume of the gap 35, and the fluid resistance generated in the gap 35 sandwiched between the outer pipe 10 and the inner pipe 20 can be reduced in proportion to the increased volume.
As a result, in the conventional device, when the fluid resistance flowing through the gap increases, the load on the compressor for pumping the fluid and the like, which is required to save energy, are solved by reducing the fluid resistance. It becomes possible to do.

Further, the formation of the ridges 21 is intended for the spiral ridges of the inner pipe having two ridges, three ridges or four ridges, and the raised ridges 22 contact the outer pipe over the entire circumference. Since they are joined in a state, the gap 35b above the flat portion and the newly formed gap 35a are formed by one protrusion 21 that is raised with another protrusion 23 sandwiched between it and the protrusion 21 that is raised in the next order. Form a closed space defined between them.
Therefore, a group of flow passages composed of two, three or four passages does not cross over this closed space, and as a result, the flow passage resistance is excessively reduced due to the formation of the new gap 35a, which reduces the contact time. It is possible to eliminate the concern that the thermal efficiency is reduced due to the short length.

The gap 35, which is the sum of the gap 35b secured above the flat portion 23 and the new gap 35a, eliminates the load of the pumping device caused by the magnitude of the fluid resistance and loses the contact time. This eliminates the concern that the heat exchange efficiency will be reduced, resulting in balanced effects.

On the other hand, if the height Ha of the selected one strip is increased as it is, the lateral width of the convex strip is enlarged by the height and becomes uneven with the lateral widths of other convex strips. Balance may occur.
However, if the raised ridge lateral width Wa is equal to the other ridge lateral width Wb and the radius of curvature (Ra) of the ridge is smaller than the radius of curvature (Rb) of the other ridge, it is an inferior arc shape. The lateral width Wa can be made equal to the lateral width Wb of the other ridges, and the widths of the ridges consisting of two, three or four ridges can be made uniform.
Therefore, even if one ridge is made high, its lateral width can be made equal to the width of the other ridge that is low, and as a result, all of the flow paths forming a group are balanced and stable. be able to.

At this time, the equations (1) and (2) and Ra=√(4Rb ² ·sin ² θb−Hb ² +Ha ² )/2sin θb (where θa=tan ⁻¹ Ha/Wa and θb=tan ⁻¹ Hb/ According to the equation (3) of Wb, Rb=1/2√(Wb ² +Hb ² )/sin θb), after setting the required height and width, the corresponding radius of curvature can be obtained and increased. The lateral width Wa of the ridge and the lateral width Wb of the other ridge can be accurately matched.

The effect of the above-described double pipe of the present invention has been mainly described in the case where the spiral portion is linear, but the same effect can be exerted even in a portion where the pipe bends.

10 outer pipe 11 inner peripheral surfaces 12a, 12b end 13 inflow pipe 13a inflow port 14 outflow pipe 14a outflow port 20 inner pipe 21 convex ridge 22 raised ridge 22a1 each raised ridge 22a2 top 22a3 ridge 23 other convex Strips 23a, 23b Other convex strips 23a1, 23b1 Tops 23a2, 23b2 Peaks 24 Flats 24a, 24b, 24c Flats 25 Closings 25a, 25b Closing convexes 30 Airspaces 31 Introducing space 32 Deriving space 33 Inlet 33a, 33b, 33c Each inlet 34 Outlet 34a, 34b, 34c Each outlet 35 Gap 35a New gap 35b Secured gap 36 Channels 36a, 36b, 36c Each channel Ha Each height of raised ridge Hb Other Height of ridge Hs Height difference Wa Horizontal width of raised ridge Wb Lateral width of other ridge Ra Ra radius of curvature of raised ridge Rb Radius of curvature of other ridge Fa, Fb, Fc Lateral width of flat portion

Claims (2)

A fluid flowing in a gap between the outer tube and the inner tube and a fluid flowing in the inner tube, wherein an inner tube in which an arcuately bulged ridge is spirally wound into two to four threads is provided inside the outer tube. In a double tube that exchanges heat with
The height (Ha) of one of the ridges is increased at a rate of 8 to 26% with respect to the height (Hb) of the other ridge, and the height of the ridge is increased over the entire circumference. A double tube for heat exchange characterized by being brought into contact with the inner peripheral surface of the tube. The height (Wa) of the raised ridge is equal to the width (Wb) of the other ridge, and the radius of curvature (Ra) of the ridge is smaller than the radius of curvature (Rb) of the other ridge. The double tube for heat exchange according to claim 1, wherein