Multi -Channeled Flat Tube And Heat Exchanger

Abstract

There is provided a multi-channeled flat tube that includes a flat outer tube and a plurality of partitions that divide the inside of the outer tube into a plurality of channels. Each partition in the multi-channeled flat tube has a mountain-shaped cross-sectional form composed of two sides, each of the two sides has a thickness ti and a length a, the partitions are disposed so that a face-to-face distance between adjacent partitions along inner surfaces of the outer tube is Li, and a thickness to of the outer tube satisfies a condition below. By selecting an appropriate pressure when expanding the multi-channeled flat tube, it is possible to prevent deformation of the tube outer surface into a wavy or undulating pattern Li·ti·a2-ti23⁢a≦to.

Description

TECHNICAL FIELD [0001] The present invention relates to the construction of a multi-channeled flat tube used in a heat exchanger. BACKGROUND ART [0002] A plate-fin heat exchanger equipped with a plurality of plate fins disposed in parallel at regular intervals and a plurality of tubes disposed so as to pass through such fins is known as one example of a heat exchanger used in refrigeration apparatuses, radiators, and the like. One method of manufacturing a plate-fin heat exchanger includes passing the tubes through the fins to assemble, and expanding or enlarging the tubes to join the tubes and fins together. In the expanding the tubes, a rigid rod or a tube expander is inserted into the tubes to press out and widen the tubes from the inside. By expanding the tubes, the tubes and fins are brought into contact. [0003] The use of multi-channeled flat tubes (multi-channel flat tubes) in heat exchangers is also known. A multi-channeled flat tube includes a plurality of partitions provid...

AI Technical Summary

Benefits of technology

[0008] With a multi-channeled flat tube with an outer tube whose thickness satisfies Condition (1) given above, the outer walls at parts of the outer tube between partitions will not deform in a range of pressure that is high enough to change the inclination of the partitions. Accordingly, a multi-channeled flat tube that satisfies Condition (1) described above can prevent deformation in the outer walls until the partitions have become straightened out. This means that by using an internal pressure in a range where there is deformation in the inclination of the partitions, the multi-channeled flat tube can be expanded in a state where deformation in the tube outer surface into a wavy or undulating state is prevented.

[0010] Another aspect of this invention is a heat exchanger that includes: a plurality of multi-channeled flat tubes that satisfy Condition (1); and a plurality of fins that are attached to the multi-channeled flat tubes. It is preferable that the plurality of multi-channeled flat tubes pass through the plurality of fins. As described earlier, with a multi-channeled flat tube that satisfies Condition (1), regardless of whether pressurized tube expansion is carried out using a fluid or whether the tube is expanded using tube expanders, it will be possible to extend the partitions while suppressing deformation in the outer walls. This means that it is possible to raise the contact efficiency after tube expansion between the plurality of multi-channeled flat tubes and the plate fins through which the tubes pass and to which the tubes are attached. Accordingly, it is possible to raise the heat transfer efficiency of the heat exchanger. In particular, when using pressurized tube expansion using a fluid, it is not necessary to insert a tube expander, which makes this method suited to expanding all of the narrow channels of the multi-channeled flat tubes substantially uniformly.

[0012] Here, in terms of making products smaller and lighter, it would not be economic to increase the thickness of the outer tube of a multi-channeled flat tube that includes a plurality of partitions to the thickness of an outer tube required for a flat tube not equipped with partitions. One merit of using multi-channeled flat tubes is that since the flat tubes can be made sufficiently strong by providing partitions inside the tube, it is possible to reduce the thickness of the outer walls or outer tube.

[0014] A pressure that is equal to or greater than the pressure used during tube expansion is not a normal operating pressure of a multi-channeled flat tube. If such pressure were applied during normal operation, there would be the possibility of further deformation in the multi-channeled flat tube since this is not how multi-channeled flat tubes are designed. Accordingly, the pressure used during tube expansion is an upper limit of the withstand pressure conditions for normal operation or even higher. Also, the pressure used during tube expansion is set up to at a pressure whereby the partitions become straightened out and is not set at a pressure whereby stretch deformation of partitions, which makes the partitions thinner, commences. This means it is economical to set the thickness of the outer tubes so that the outer walls deform at a pressure where stretch deformation, which makes the partitions thinner, commences. The heat transfer efficiency also increasing when thin outer tubes are used.

Problems solved by technology

This would reduce the contact surface area between the tube outer surface and the fins and reduce the heat transfer performance.

However, if tube expansion is stopped before the partitions have extended to reach the desired size, the desired performance cannot be obtained.

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