JP2003214724A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner that can improve air conditioning performance and can simplify structure. <P>SOLUTION: The air conditioner 10 comprises a heat exchanger 12 and a cross flow fan 13 both arranged in a casing 11. The heat exchanger 12 is arranged substantially in a Λ shape including a first-stage part 40 arranged between an air inlet 22 in a front face of the casing 11 and the cross flow fan 13, and a second-stage part 41 arranged between an air inlet 26 in a top face of the casing 11 and the cross flow fan 13, so as to enclose a suction side circumference of the cross flow fan 13; and comprises a number of flat tubes 31 arranged for parallel flat faces to an airflow direction and arrayed parallel in a vertical attitude, and corrugated fins 32 each arranged between adjacent flat tube 31. The first-stage part 40 includes a curved portion 40a curved along the circumference of the cross flow fan 13. <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 an air conditioner provided with a heat exchanger and a crossflow fan which are arranged in a housing having air inlets on its front and upper surfaces.

[0002]

2. Description of the Related Art FIG. 13 is a schematic configuration diagram of a conventional air conditioner 1 viewed from the side. The air conditioner 1 includes a plate fin tube type heat exchanger 6 and a cross flow fan 7, which are arranged in a housing 3 and are divided into a plurality of parts. Air inlets 4 and 8 are formed in the front panel 2 and the upper panel 5.

The heat exchanger is of a so-called plate fin tube type, and a plurality of plate fins 10 are arranged between the side plates, and a circular tube 11 through which a refrigerant flows is arranged between the side plates and the plate fins 10. Is divided into a plurality of parts so as to face the air suction ports 4 and 8,
It is arranged so as to surround the suction side peripheral surface of the cross flow fan 7 in a Λ shape.

[0004]

In the conventional air conditioner 1, the plate fin tube type heat exchanger 6 is divided into a substantially Λ shape, bent, and arranged in the housing 3 so that the heat in the housing 3 is reduced. Although the density of the exchanger 6 is increased and the air conditioning performance is improved, the plate fin tube type heat exchanger 6 has a limit in increasing the density, and the length of the tubes constituting the heat exchanger must be long. Therefore, the heat exchange rate greatly changed in the length direction of the tube, and a portion having a low heat exchange rate occurred in the heat exchanger as a whole, so that the temperature distribution was not uniform and unevenness was likely to occur. For this reason, the heat exchange tube is divided into other circuits, and a distributor is provided to distribute and flow the refrigerant to each circuit.
Not only is the problem that the piping becomes complicated and the number of joints in the piping increases, but it is not easy to evenly distribute the refrigerant to each circuit.By addressing these problems, further improvement in air conditioning performance is possible. Is required.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an air conditioner capable of improving air conditioning performance and simplifying the structure. .

[0006]

In order to solve the above-mentioned problems, the present invention provides an air conditioner comprising a heat exchanger and a crossflow fan which are arranged in a housing having air inlets on its front and upper surfaces. The heat exchanger has a substantially Λ shape consisting of a first step portion facing the air suction opening on the front surface of the housing and a second step portion facing the air suction opening on the upper surface, and the suction of the cross flow fan. The heat exchanger is arranged so as to surround the side peripheral surface, and the heat exchanger is arranged between the flat tubes in parallel with each other in the vertical direction by disposing flat surfaces in parallel along the air flow direction and between the flat tubes. The heat exchanger is composed of corrugated fins arranged. In this air conditioner, since the heat exchanger having the above-described configuration is arranged so as to surround the suction side peripheral surface of the cross flow fan so as to form a substantially Λ shape, a large heat exchange is performed in the housing of the limited space. A heat exchanger having an area can be easily arranged.
As a result, the density of the heat exchangers can be increased and the air conditioning performance can be improved, and since a distributor and extra connection pipes are not required, the piping structure around the heat exchangers can be simplified.

In this case, the heat exchanger has the first
The stepped portion may have a curved portion that curves along the peripheral surface of the cross flow fan. Thereby, the heat exchanger can be further densified.

In this case, in the heat exchanger, a plurality of laminated flat tubes in which drawn plate-like members are stacked and a flow path for a heat medium is provided therein, and a plurality of corrugated fins are provided. May be alternately laminated. This allows the first step portion to be easily curved.

In this case, in the heat exchanger, the first stage portion and the second stage portion are connected to each other.
The laminated flat tubes of the step portion and the laminated flat tubes of the second step portion may be alternately laminated. By connecting the first step portion and the second step portion, the structure of the pipe for supplying and discharging the heat medium can be simplified.

In this case, in the heat exchanger, one of the laminated flat tubes of the first step portion and the laminated flat tube of the second step portion has an end portion of one laminated flat tube and another laminated flat tube of the other laminated flat tube. The ends may be inserted and connected. As a result, the first-stage portion and the second
The stepped portion can be connected and the thickness of the stack can be reduced.

Further, the heat exchanger may be one in which the first stage portion and the second stage portion are integrally formed. Thereby, the structure of the heat exchanger can be further simplified.

The heat exchanger includes a plurality of flat tubes having a plurality of heat medium flow passages therein, a header to which both ends of the flat tubes are connected, and a plurality of flat tubes arranged between the flat tubes. It may be configured with a plurality of fins that are provided to promote heat exchange. Thereby, the structure of the heat exchanger can be simplified.

In this case, the heat exchanger may be a multi-flow type heat exchanger in which the flow of the heat medium is determined for each of the plurality of flat tubes. Due to the flow of the heat medium due to the multi-flow, heat unevenness in the heat exchanger can be suppressed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of an air conditioner according to the present invention will be described below with reference to the drawings. Figure 1
FIG. 1 is a schematic configuration diagram of a so-called wall-mounted air conditioner 10 seen from a side surface. The air conditioner 10 has a housing 11
And a heat exchanger 12 and a cross flow fan 13 arranged in the housing 11.

The housing 11 is formed in a box shape as a whole by combining the front panel 21 and the top panel 25 with the base. The front panel 21 and the upper panel 25 may be integrally formed. The front panel 21 has an air suction port 22 formed on the front surface and an air outlet port 23 formed below. Also,
An air suction port 26 is also formed in the upper panel 25.
The air outlet 23 is provided with a louver 24 for changing the air outlet direction.

2 and 3 are diagrams schematically showing the basic structure of the heat exchanger 12. As shown in FIG. The heat exchanger 12 is formed by stacking a plurality of drawn plate-shaped members 30 on top of each other and is formed with a substantially U inside.
A plurality of laminated flat tubes 31 (hereinafter, referred to as laminated flat tubes) provided with V-shaped heat medium flow paths, and a plurality of corrugated fins (corrugated fins) 32 that promote heat exchange, and these alternate. It is configured to be stacked in (stacked tube type). The plate member 30 includes
Communication holes 33, 34 are provided, and a plurality of plate-shaped members 3
0 communication holes 33 and 34 are connected to each other to form a heat medium tank (inlet tank 35 and outlet tank 36). In the heat exchanger 12, the heat medium (including the refrigerant) is supplied from the supply pipe (not shown) into the inlet tank 35, and the heat medium is discharged from the outlet tank 36 to the discharge pipe (not shown). In each laminated flat tube 31, the heat medium flows from the inlet tank 35 side to the outlet tank 36 side in the substantially U-shaped heat medium flow passage. And the fin 32
Air introduced into the housing of the air conditioner is cooled or heated by heat exchange via the air conditioner.

Returning to FIG. 1, the heat exchanger 12 of this example has a first-stage portion 40 disposed between the air suction port 22 of the housing 11 and the crossflow fan 13 so as to face the air suction port 22.
And a second step portion 41 arranged between the air suction port 26 and the cross flow fan 13 so as to face the air suction port 26. The first step portion 40 is formed to be larger than the air suction port 22 and is arranged obliquely with respect to the flow of air introduced from the air suction port 22 of the housing 11. Also, the first
The fins 32 of the step portion 40 are arranged so as to be substantially parallel to the air flow. Further, the fins 32 are provided so that the resistance to the air flow is reduced.
The interval between them is defined. The fins 32 may be arranged with different density depending on the area so that the air resistance is small and the heat exchange is performed efficiently, for example, the fins 32 are sparser in the upper part and more dense in the lower part. It should be noted that in the present invention, the arrangement of the fins 32 is not limited to that described above, and various changes can be made.

Further, in this example, at least a part of the first step portion 40 of the heat exchanger 12 is formed to be curved along the peripheral surface of the fan 13 for introducing air into the housing 11.
In this example, the curved portion 40 is provided below the first step portion 40.
a is formed with a curvature substantially equal to the peripheral surface of the fan 13. The shape of the curved portion 40a is not limited to that described above, and can be set arbitrarily.

The second-stage portion 41 of the heat exchanger 12 is arranged above the crossflow fan 13 between the air suction port 26 and the crossflow fan 13 at an angle with respect to the air flow. The cross-flow fan 13 is arranged in a substantially Λ shape so as to sandwich the cross-flow fan 13 with the step portion 40 so as to sandwich the cross-flow fan 13 therebetween.

In this example, a heat medium supply pipe and a heat medium discharge pipe are connected to both the first stage portion 40 and the second stage portion 41 of the heat exchanger 12, and the heat medium supply pipe and the heat medium supply pipe are connected through these pipes. The heat medium flows in the first step portion 40 and the second step portion 41 independently of each other. In addition, the heat exchanger 12 is configured such that the flat planes of the laminated flat tubes 31 in the first stage portion 40 and the second stage portion 41 are parallel to the air flow direction, and a plurality of laminated flat laminates are stacked. The tubes 31 are installed so as to be arranged in parallel in the vertical direction, and further, the first stage portion 40 and the second stage portion 41 are provided.
Drain pans 27 and 28 are respectively installed in the lower part of the, and are configured to be able to receive the drain flowing down along the laminated flat tube 31.

In the air conditioner 10 having the above structure, when the crossflow fan 13 is driven, air is introduced into the housing 11 through the air suction port 22 of the front panel 21 and the air suction port 26 of the upper panel 25. . The air introduced into the housing 11 is transferred to the first stage portion 40 and the second stage portion 40 of the heat exchanger 12.
The heat is exchanged through the step portion 41 and is cooled or heated. Then, the heat-exchanged air in the housing 11 is blown into the room from the air outlet 23 by driving the fan 13.

Here, the heat exchanger 12 is arranged between a large number of flat tubes 31 having flat surfaces arranged in parallel along the air flow direction and arranged in parallel in the vertical direction, and between the flat tubes 31. And a second step portion 41 facing the air suction port 22 on the front surface of the housing 11 and a second step portion 41 facing the air suction port 26 on the upper surface. None, cross flow fan 1
Since it is arranged so as to surround the suction side peripheral surface of 3, the heat exchanger 12 having a large heat exchange area can be easily arranged in the housing 11 in a limited space. Then, by circulating a refrigerant in the heat exchanger 12 in the direction shown by the arrow in FIG. 2 or in the opposite direction, heat is exchanged with the room air, and the room can be cooled or heated. Therefore, according to this example, it is possible to increase the density of the heat exchangers and improve the air conditioning performance, and to simplify the piping structure around the heat exchangers because no distributor or extra connection piping is required. Moreover, since the flat tubes 31 are arranged in the vertical direction, the drain generated during cooling and dehumidifying can be swiftly collected in the drain pans 27 and 28 by flowing down the surface thereof.

Also, the first stage portion 40 of the heat exchanger 12 is
Since it is curved along the peripheral surface of the fan 13, the heat exchanger 12 having a larger heat exchange area can be easily arranged in the housing 11 of the limited space, and the heat exchanger can be further densified. be able to. In this example, the heat exchanger 12 is
Laminated flat tube 31 in which a plurality of plate-shaped members 30 that have been drawn are stacked and a heat medium flow path is provided inside.
And the corrugated fins 32 are alternately laminated, the first step portion 40 can be easily curved. That is, the curved portion 40a can be easily formed by forming the plate-shaped member 30 that is a component of the laminated flat tube 31 in a curved shape in advance.

Further, in this example, the first stage portion 40 and the second stage portion 41 of the heat exchanger 12 are the air suction port 2 of the housing 11.
Since the fins 32 are arranged obliquely with respect to the flow of air introduced from 2, 26, the heat exchange area of the fins 32 can be made larger than the thickness of the heat exchanger 12. Further, since the fins 32 of the first step portion 40 are arranged so as to be substantially parallel to the air flow, the resistance to the air flow can be reduced. In addition, the fins 32 may be arranged with different density depending on the area so that the air resistance is small and the heat exchange is performed efficiently, which can further improve the air conditioning performance.

Here, the form of the heat exchanger used in the air conditioner is not limited to the above-mentioned example, and other forms of heat exchanger may be used.

FIG. 4 shows an example of another form of the heat exchanger. The heat exchanger 50 includes a plurality of flat tubes 51 having flow passages for a heat medium, such as electric resistance welded pipes or extruded pipes.
It has a plurality of fins 52 that promote heat exchange, and the flat tubes 51 and the fins 52 are joined to each other and are alternately laminated in a plurality of stages (flat tube type). Further, the flat tube 51 has a flat hollow cross section, and a plurality of heat medium flow passages are formed inside the flat tube 51, and end portions thereof are respectively connected to heat medium tanks (inlet tank 53, outlet tank 54). . This heat exchanger 50 is
In the inlet tank 53 and the outlet tank 54, the heat medium flows in a predetermined direction (arrow direction), and a plurality of flat tubes 51
Is a so-called multi-flow type heat exchanger in which the heat medium flows simultaneously in parallel.

FIG. 5 shows another example of another form of the heat exchanger. This heat exchanger 60 has flat tubes 61 and fins (not shown) that are alternately laminated, as in FIG. Prepare,
Each flat tube 61 is connected to the heat medium tanks 63 and 64. Further, this heat exchanger 60 is different from the example of FIG. 4, and is a so-called multi-flow type heat exchanger in which the heat medium flows meandering any number of times in the heat medium tanks 63 and 64 and in each flat tube 61. Has become.

In FIG. 5, the flat tubes 61 are arranged in two upper and lower stages in the air flow direction between the heat medium tanks 63 and 64, and the heat medium flows in the flat tubes 61 in different vertical directions. The inside of each tank 63, 64 is shown in FIG.
As shown in the cross-sectional view of, it is divided into a predetermined shape,
The flow of the heat medium is determined by this section (path structure). In the heat exchanger 60, in the first stage portion 65, as shown in FIG.
The heat medium flows through the flat tubes 61 and the tanks 63 and 64 according to the flow pattern shown in FIG. Although not shown in the figure, the heat medium can also flow through the second stage portion 66 in the same multi-flow manner. The path structure is not limited to the example shown in FIG. 6, various flow patterns are conceivable, and it suffices to select a pattern that causes the least heat unevenness. Due to the flow, heat unevenness in the heat exchanger can be suppressed, and higher efficiency can be achieved.

In the heat exchangers shown in FIGS. 4 and 5, the flat tubes are arranged so as to extend in a direction substantially vertical to the horizontal, that is, in the vertical direction. Conventionally, a flat tube is often arranged horizontally, and in this case, a drain generated due to dew condensation of moisture in the air on the surface of the tube and fins grows and easily falls. However, by disposing the flat tubes in the vertical direction as in the present example, the drain dew flows along the flat tubes, and thus can be properly collected in the drain pans 27 and 28. Further, by using the flat tube type heat exchanger, the structure of the pipe for supplying and discharging the heat medium can be simplified.

Both the heat exchangers of FIGS. 4 and 5 described above can be applied to the air conditioner of the present invention. In addition, in each heat exchanger explained so far, a heat medium supply pipe and a discharge pipe are connected to both the first-stage portion and the second-stage portion of the heat exchanger, and the heat medium supply pipe and the discharge pipe are connected to each other through the pipes. Although the heat medium is made to flow independently in the first-stage part and the second-stage part, the heat-medium flow paths of the first-stage part and the second-stage part are connected,
The supply pipe and the discharge pipe may be combined.

Next, a second embodiment of the air conditioner according to the present invention will be described with reference to the drawings. FIG. 8 is a perspective view schematically showing a second embodiment of the air conditioner according to the present invention. Like the first embodiment, the air conditioner 80 includes a housing (not shown), a heat exchanger 82 and a cross flow fan 83 arranged in the housing,
The heat exchanger 82 includes a first stage portion 84 arranged between the air inlet on the front surface of the housing and the crossflow fan, and a first stage portion 84 arranged between the air inlet on the upper surface of the housing and the crossflow fan. And a two-step portion 85. Further, a part of the first step portion 84 is formed to be curved (curved portion 84a). In this example, as the heat exchanger 82, a laminated flat tube type heat exchanger using the laminated tubes 86 and 87 and fins (corrugated fins) 88 described with reference to FIG. 2 is used. The heat medium flows according to the flow pattern shown by the arrow in FIG.

In FIG. 8, in the present embodiment, unlike the first embodiment, the first stage portion 84 and the second stage portion 84 of the heat exchanger 82 are provided.
The heat medium flow path is connected to the step portion 85. In this example, the connecting portion between the two has a structure in which the laminated flat tubes 86 of the first step portion 84 and the laminated flat tubes 87 of the second step portion 85 are alternately laminated.

10 and 11 schematically show the cross-sectional structure of the above-mentioned connecting portion, FIG. 10 shows a horizontal cross-section of the connecting portion, and FIG. 11 shows a vertical cross-section. As shown in FIGS. 10 and 11,
The connecting portion has a structure in which the end portion of the other laminated flat tube is inserted into the end portion of the one laminated flat tube to be connected, and the plurality of laminated flat tubes 86, 87 are connected to each other to form a heat medium. Tanks (an inlet tank 89 and an outlet tank 90) are formed.

In the air conditioner 80 of this embodiment, the structure of the piping for supplying and discharging the heat medium by connecting the first stage portion 84 and the second stage portion 85 of the heat exchanger 82. Can be more simplified. Further, since the end portion of the other laminated flat tube is inserted and connected to the end portion of the one laminated flat tube, the first step portion 84 and the second step portion 85 can be connected with a simple structure, and the connection can be achieved. The laminated thickness of the part can be reduced. In this example, the laminated flat tube type and multi-flow type heat exchangers are used, but the present invention is not limited to this, and the flat tube type and multi-flow type heat exchangers described above are used. You may connect a 1st step part and a 2nd step part.

Next, a third embodiment of the air conditioner according to the present invention will be described with reference to the drawings. FIG. 12 is a perspective view schematically showing a third embodiment of the air conditioner according to the present invention. The air conditioner 100 is configured to include a housing (not shown), a heat exchanger 102 and a crossflow fan 103 arranged in the housing, as in the above-described embodiments, and the heat exchanger 102. Is a first stage portion 104 arranged between the air suction port on the front surface of the housing and the crossflow fan 103, and a second stage portion arranged between the air suction opening on the upper surface of the housing and the crossflow fan 103. And a portion 105. Further, a part of the first step portion 104 is formed to be curved (curved portion 104a). In addition, in this example, the heat exchanger 102 is a laminated flat tube type using the same laminated flat tube 106 and fins (corrugated fins) 108 as those described with reference to FIG. It is a multi-flow type heat exchanger.

12, in the present embodiment, unlike the above-described embodiments, the first stage portion 1 of the heat exchanger 102 is
04 and the second step portion 105 are integrally formed. Specifically, the plate-shaped members forming the laminated flat tubes 106 and 107 are previously formed by the first step portion 104 and the second step portion 105.
It is formed in a predetermined shape with a portion that can be, and does not have a connecting portion like the heat exchanger shown in FIG.

In the air conditioner 100 of this embodiment, since the first-stage portion 104 and the second-stage portion 105 of the heat exchanger 102 are integrally formed, the structure of the heat exchanger is further simplified. be able to. Further, since there is no connecting portion between the first step portion and the second step portion, the resistance of the flow of the heat medium can be reduced, the pressure loss of the heat medium can be suppressed, and the air conditioning performance can be improved. When a laminated flat tube is used as in this example, it can be easily adapted to any shape of the heat exchanger. However, the present invention is not limited to this, and the flat tube type and multi-flow type heat exchangers described above may be used to connect the first stage portion and the second stage portion.

The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. The shapes, combinations, and the like of the constituent members shown in the above-described examples are merely examples, and various changes can be made based on design requirements and the like without departing from the spirit of the present invention.

[0039]

As described above, according to the air conditioner of the present invention, it is possible to easily dispose the heat exchanger having a large heat exchange area in the housing of the limited space. The density can be improved to improve the air conditioning performance, and the piping structure around the heat exchanger can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of an air conditioner according to the present invention.

FIG. 2 is a diagram schematically showing a basic configuration of a heat exchanger.

FIG. 3 is a cross-sectional view schematically showing the basic structure of a heat exchanger.

FIG. 4 is a diagram showing an example of another form of a heat exchanger.

FIG. 5 is a diagram showing another example of another form of the heat exchanger.

6A is a sectional view taken along the line AA in FIG.
FIG. 6B is a sectional view taken along the line BB of FIG.

7 is a diagram showing a flow of a heat medium of the heat exchanger shown in FIG.

FIG. 8 is a perspective view schematically showing a second embodiment of the air conditioner according to the present invention.

9 is a diagram showing a flow of a heat medium of a heat exchanger of the air conditioner shown in FIG.

FIG. 10 is a transverse cross-sectional view showing a cross-sectional structure of a connecting portion of the heat exchanger, the cross-section being cut along the axis in the extending direction of the laminated tube.

FIG. 11 shows a cross-sectional structure of the connection portion of the heat exchanger, and FIG.
It is an arrow CC sectional view shown in FIG.

FIG. 12 is a perspective view schematically showing a third embodiment of the air conditioner according to the present invention.

FIG. 13 is a schematic configuration diagram of a conventional air conditioner viewed from the side.

[Explanation of symbols]

10,80,100 Air conditioner 11 housing 12,50,60,82,102 heat exchanger 13,83,103 Cross flow fan 22,26 Air inlet 31,86,87,106 Laminated flat tube 32, 52, 88, 108 fins 40,65,84,104 1st stage part 41, 66, 85, 105 Second stage part 40a, 84a, 104a curved portion 51,61 Flat tube

Claims (8)

[Claims] 1. An air conditioner including a heat exchanger and a crossflow fan arranged in a housing having air inlets on a front surface and an upper surface, wherein the heat exchanger is an air inlet on the front surface of the housing. Has a substantially Λ shape consisting of a first step portion opposed to the above and a second step portion opposed to the air suction port on the upper surface, and is arranged so as to surround the suction side peripheral surface of the cross flow fan, and the heat exchange The heat exchanger is a heat exchanger composed of a large number of flat tubes having flat surfaces arranged in parallel along the air flow direction and arranged in parallel in the vertical direction, and corrugated fins respectively arranged between the flat tubes. An air conditioner characterized by. 2. The air conditioner according to claim 1, wherein the first stage portion of the heat exchanger has a curved portion that curves along the peripheral surface of the cross flow fan. 3. In the heat exchanger, a plurality of laminated flat tubes in which plate-shaped members that have been subjected to a drawing process are stacked and a flow path for a heat medium is provided inside, and a plurality of corrugated fins are alternated. The air conditioner according to claim 1 or 2, wherein the air conditioner has a laminated structure. 4. In the heat exchanger, the first stage portion and the second stage portion are connected, and the laminated flat tubes of the first stage portion and the laminated flat tubes of the second stage portion are alternately arranged. It is laminated | stacked, The air conditioner of Claim 2 or 3 characterized by the above-mentioned. 5. The heat exchanger according to claim 1, wherein one of the laminated flat tubes of the first step portion and the laminated flat tube of the second step portion has an end portion of one laminated flat tube and an end portion of the other laminated flat tube. The air conditioner according to claim 4, wherein the air conditioner is inserted and connected. 6. The air conditioner according to claim 2, wherein the heat exchanger has the first stage portion and the second stage portion integrally formed. 7. The heat exchanger comprises: a plurality of flat tubes having a plurality of heat medium flow passages therein; a header to which both ends of the flat tubes are connected; and a plurality of flat tubes arranged between the flat tubes. The air conditioner according to claim 1, wherein the air conditioner comprises a plurality of fins that are provided to promote heat exchange. 8. The air conditioner according to claim 7, wherein the heat exchanger is a multi-flow type heat exchanger in which the flow of the heat medium is determined for each of the plurality of flat tubes.