Heat exchanger tube

Abstract

A heat exchanger tube is constituted by a flat tube body 14 shaped like a plurality of cylindrical tubes arranged mutually proximally in a plane and connected together at mutually proximate portions of the tubes as communicating portions 13. Cylindrical portions 15 corresponding to the cylindrical tubes of the flat tube body 14 have inner peripheries formed with swirling-flow-forming protrusions 16 directed along spiral trajectories coaxial with central axes O of the cylindrical portions 15 so that the respective cylindrical portions 15 may have individual swirling flows of the exhaust gas 10.

Claims

1. A heat exchanger tube comprising: a flat tube body shaped like a plurality of cylindrical tubes arranged mutually proximately along a plane and connected together at mutually proximate portions of the cylindrical tubes as communicating portions; and cylindrical portions corresponding respectively to the cylindrical tubes of the flat tube body, the cylindrical portions being concaved into grooves on outer peripheries of the cylindrical portions to thereby provide swirling-flow-forming protrusions on inner peripheries of the cylindrical portions along spiral trajectories coaxial with central axes of the cylindrical portions so that swirling flows of heat medium may be individually formed in the respective cylindrical portions, wherein each of the cylindrical portions has a circular cross-section, wherein neighboring cylindrical portions are shaped to have the swirling-flow-forming protrusions directed along mutually reversed spiral trajectories, and wherein each of the grooves is formed to extend less than 180 degrees around a periphery of the circular cross-section of each of the cylindrical portions.

2. A heat exchanger tube comprising: a flat tube body shaped like a plurality of cylindrical tubes arranged mutually proximately along a plane and connected together at mutually proximate portions of the cylindrical tubes as communicating portions; and cylindrical portions corresponding respectively to the cylindrical tubes of the flat tube body, the cylindrical portions including concave grooves on outer peripheries of the cylindrical portions to thereby provide swirling-flow-forming protrusions on inner peripheries of the cylindrical portions along spiral trajectories coaxial with central axes of the cylindrical portions so that swirling flows of heat medium may be individually formed in the respective cylindrical portions, wherein each of the cylindrical portion has a circular cross-section, wherein each of the grooves is formed to extend less than 180 degrees around a periphery of the circular cross-section of each of the cylindrical portions, wherein the grooves on adjacent cylindrical portions are slanted with respect to a longitudinal axis of the tube body in opposite directions so that the swirling flows of the heat medium of adjacent cylindrical portions swirl in opposite directions, and wherein the swirling flows are guided by the grooves only along the inner peripheries of the cylindrical portions where the grooves are formed.

3. The heat exchanger tube of claim 1, wherein the swirling flows are guided by the grooves only along the inner peripheries of the cylindrical portions where the grooves are formed.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a sectional view showing an example of a usual EGR cooler;

(2) FIG. 2 is a perspective view showing a conventional example;

(3) FIG. 3 is a perspective view showing a trial model with the tube of FIG. 2 being flattened;

(4) FIG. 4 is a perspective view showing an embodiment of the invention;

(5) FIG. 5 is a sectional view of the flat tube body shown in FIG. 4; and

(6) FIG. 6 is a sectional view schematically showing an application to an EGR cooler.

DESCRIPTION OF EMBODIMENT

(7) An embodiment of the invention will be described in conjunction with the drawings.

(8) FIGS. 4 and 5 show the embodiment of a heat exchanger tube according to the invention, which is applied to an EGR cooler as is the case in the above-mentioned prior art. In the figures, parts similar to those in FIGS. 1-3 are represented by the same reference numerals.

(9) As shown in FIG. 4, the embodiment of the heat exchanger tube comprises a flat tube body 14 shaped like a plurality of cylindrical tubes arranged mutually proximally in a plane and connected together at mutually proximal portions thereof as communicating portions 13. Cylindrical portions 15 corresponding to the cylindrical tubes of the flat tube body 14 have inner peripheries formed with swirling-flow-forming protrusions 16 along spiral trajectories coaxial with central axes O of the cylindrical portions 15 (the respective cylindrical portions 15 are concaved into grooves on outer peripheries thereof to thereby provide swirling-flow-forming protrusions 16 as inverse formations) so that swirling flows of the exhaust gas 10 may be individually formed in respective cylindrical portions 15.

(10) Specifically, as shown in FIG. 5, despite of the communicating portions 13 between the respective cylindrical portions 15, the exhaust gas 10 flowing through the respective cylindrical portions 15 is caused to swirl by properly tuning, for example, pitch L between central axes of the respective cylindrical portions 15, vertical gap C of the communicating portions 13 and raised height H of the swirling-flow-forming protrusions 16.

(11) Especially in the embodiment, neighboring cylindrical portions 15 are shaped to have the swirling-flow-forming protrusions 16 directed along mutually reversed spiral trajectories (see appearances of the respective cylindrical portions 15 in FIG. 4) such that the swirling flows are orientated in one and the same direction at the communicating portions 13 of the neighboring cylindrical portions 15, which is a contrivance for prevention of mutual counteraction of the swirling flows (see directions of the swirling flows of the exhaust gas 10 shown by arrows in FIG. 5).

(12) The flat tube body 14 may be produced by, for example, producing a pair of halved parts constituting upper and lower portions of the flat tube body through press working or the like, placing the halved parts one above the other and welding the parts at opposite ends thereof. Upon such press working, the respective cylindrical portions 15 may be concaved into grooves on outer peripheries thereof for prominence of the swirling-flow-forming protrusions 16 on the inner peripheries as inverse formations.

(13) In such production of the flat tube body 14, various production methods may be, of course, utilized which have been already practiced for existing heat exchangers such as radiators and intercoolers. For example, parts to be joined may be formed to have overlap portions at which the parts are joined together through brazing; alternatively, a lower structure with an upper structure laid out sideways thereof may be pressed as a single piece, the upper structure being folded back on the lower structure and joined together through welding or brazing.

(14) When sides or a side of the flat tube body 14 is to be utilized for joining, to form the swirling-flow-forming protrusions 16 (grooving on the outer periphery: see FIG. 4) on the sides or side may be partly omitted in view of easiness in a joining work. It has been affirmed by the inventors that the partial omission of the swirling-flow-forming protrusions 16 on the sides or side does not greatly affect the formation of the swirling flows.

(15) Then, with the heat exchanger tube thus constituted, the flows of the exhaust gas 10 through the respective cylindrical portions 15 of the flat tube body 14 are guided in directions along the spiral trajectories by the swirling-flow-forming protrusions 16 on the inner peripheries of the respective cylindrical portions 15, so that the swirling flows of the exhaust gas 10 are individually formed in the respective cylindrical portions 15. As a result, the contact frequency and the contact distance of the exhaust gas 10 to the inner peripheries of the respective cylindrical portions 15 are increased to enhance the heat exchange efficiency. Moreover, the fact that the respective cylindrical portions 15 are mutually in communication through the communicating portions 13 ensures a sufficient flow-path cross-sectional area for passage of the exhaust gas 10, so that heat quantity exchanged per unit volume is enhanced and pressure loss is decreased.

(16) In the embodiment, neighboring cylindrical portions 15 are shaped to have the swirling-flow-forming protrusions 16 directed along mutually reversed spiral trajectories, which makes the swirling flows, at the communicating portions 13 of the neighboring cylindrical portions 15, orientated in one and the same direction and mutually accelerated, so that, despite of the communicating portions 13 between the respective cylindrical portion 15, formation of the exhaust gas 10 as swirling flows can be further ensured.

(17) Thus, according to the above-mentioned embodiment, while the exhaust gas 10 is caused to swirl to thereby realize high heat exchange efficiency competing to the prior art, heat quantity exchanged per unit volume can be substantially enhanced to an extent unattainable in the prior art. For example, in an application to an EGR cooler as shown in FIG. 6, accommodated in the shell 1 with rectangular cross-section are the flat tube bodies 14 as mentioned in the above in a plurality of rows (two rows in the example illustrated) and in a multistage (nine stages in the example illustrated), so that the EGR cooler as a whole can be made compact in size to enhance mountability to a vehicle while an amount of the exhaust gas 10 to be recirculated can be increased more than ever to enhance the EGR ratio.

(18) Especially in the embodiment, neighboring cylindrical portion 15 are shaped to have the swirling-flow-forming protrusions 16 directed along mutually reversed spiral trajectories, which makes the swirling flows, at the communicating portions 13 of the neighboring cylindrical portions 15, orientated in one and the same direction and mutually accelerated, so that formation of the swirling flows in the respective cylindrical portions 15 can be further ensured.

(19) It is to be understood that a heat exchanger tube according to the invention is not limited to the above embodiment and that various changes and modifications may be made without departing from the scope of the invention. For example, the invention may be applied to any heat exchanger other than that for an EGR cooler.

REFERENCE SIGNS LIST

(20) 10 exhaust gas (heat medium) 13 communicating portions 14 flat tube body 15 cylindrical portion 16 swirling-flow-forming protrusion