JPS6396490A - Heat exchanger - Google Patents

Abstract

PURPOSE:To prevent Karman's vortex as well as fluid separation, improve heat transfer characteristics and miniaturize a heat exchanger, by a method wherein primary fluid is made to flow through the outside of heat transfer tubes, whose back surface is formed into aerofoil, while secondary fluid is introduced into the inside of the heat transfer tube. CONSTITUTION:The back surface of a heat transfer tube 1 of ceramics with respect to the flow direction of primary fluid 2 is formed so as to be streamline. The heat transfer tubes 1 are arranged so as to form multiple flow paths. The fore surface of the same tube 1 is provided with a curved surface having a proper curvature. The primary fluid 2 is made to flow through primary fluid flow paths at the outside of the heat transfer tubes 1, while secondary fluid is introduced into the heat transfer tubes 1. As a result, generation of Karman's vortex or fluid separation in the primary fluid may be prevented. Further, the heat transfer characteristic of the title heat exchanger is increased remarkably and the heat transfer tubes 1 can be arranged densely whereby the heat exchanger may be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat exchanger, and particularly relates to the direction of heat transfer characteristics, F, of a heat exchanger.

[Prior Art] Generally, in a heat exchanger type heat exchanger for a forging furnace or the like, a secondary fluid is introduced into heat exchanger tubes a arranged in multiple layers as shown in FIG. A flow path for a primary fluid is formed outside, and the fluid is flowed in a direction perpendicular to the heat exchanger tube a. Thereby, heat exchange is performed between the primary fluid and the secondary fluid via the heat transfer tube a.

[Problems to be Solved by the Invention] By the way, a conventional heat exchanger tube a usually has a perfect circular cross-sectional shape as shown in FIG. . Therefore, Karman vortices C and fluid separation of the primary fluid are likely to occur at the back surface of the heat exchanger tube a, and as a result, the heat transfer coefficient between the fluid supply and the heat exchanger tube a decreases, and the heat transfer as a heat exchanger is reduced. There was a problem that thermal properties deteriorated.

Thus, an object of the present invention is to solve the problems of the prior art described above and to provide a heat exchanger with excellent heat transfer characteristics.

[Means for Solving the Problems] In order to achieve the above object, the heat exchanger of the present invention is a heat exchanger in which a primary fluid is flowed outside the heat exchanger tubes and a secondary fluid is introduced into the heat exchanger tubes. , the back surface of the heat transfer tube in the flow direction of the primary fluid is shaped into a streamlined shape.

[Function] In general, the Nutsselt number Nut, which indicates the heat transfer coefficient at the front surface of a cylinder placed perpendicular to the flow in a flow with a Reynolds number Re, is NIJt = 0.746-
RQ! It is known that it can be expressed as /2.

On the other hand, the Nutsselt number Nur at the back surface of the cylinder is expressed as Nur = 0.114-ReV3. For example, for a flow with a Reynolds number Re = 8000, it becomes It can be seen that the front part has a 32% better heat transfer efficiency than the back part. In other words, the heat transfer efficiency of the back surface of the cylinder is inferior to that of the front surface.

Therefore, by making the back surface of the heat exchanger tube, which had conventionally had a circular cross section in the flow direction of the primary fluid, streamlined to prevent the occurrence of Karman vortices and fluid separation of the primary fluid, the entire circumference of the heat exchanger tube was Heat transfer efficiency can be improved by about 20%.

In addition, by doing this, fluid vibrations due to Karman vortices are prevented, making it possible to reduce the arrangement pitch of the heat transfer tubes and arrange them more densely. Due to the increased velocity of the foam fluid,
Furthermore, extratubular heat transfer is also improved, so that the heat exchanger can be made more compact.

[Example] Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of heat exchanger tube portions arranged in a heat exchanger according to an embodiment of the present invention. Heat exchanger tubes 1 are arranged in multiple layers within the heat exchanger, and a primary fluid flow path is formed outside the heat exchanger tubes 1 in a direction perpendicular to the heat exchanger tubes. Here, heat exchanger tube 1
is made of ceramics, - the front part with respect to the flow direction of the foam fluid is formed from a curved surface having an appropriate curvature;
The back part is shaped to have a streamlined shape.

The primary fluid 2 is caused to flow through the primary fluid flow path of such a heat exchanger, and the secondary fluid is introduced into the heat exchanger tubes 1. Then, since the back side of the heat transfer tube 1 has a streamlined shape, -bubble fluid 2
When it is guided from the front side to the back side of the heat exchanger tube 1 along with the flow, it is smoothly flowed downstream without generating fluid separation or Karman vortices. As a result, heat is efficiently exchanged between the primary fluid 2 and the secondary fluid via the heat transfer tube 1.

Note that, as described above, since the generation of Karman vortices in the primary fluid 2 is prevented, fluid vibrations caused by Karman vortices are suppressed, which makes it possible to arrange the heat exchanger tubes 1 at a smaller pitch. The heat exchanger can be downsized by the combined effect of improving the heat transfer efficiency at the back surface of the heat exchanger tube and improving the extratubular heat transfer due to the reduction in the cross-sectional area of the extratube flow path.

Further, in the above embodiment, a heat exchanger tube made of ceramics is used, but the present invention is not limited to this.

[Effects of the Invention] As explained above, according to the present invention, the following excellent effects are exhibited.

(1) - Occurrence of Karman vortices and fluid separation of bubble fluid is prevented.

(2) Therefore, the heat transfer characteristics of the heat exchanger are significantly improved, and the heat exchanger can be downsized by closely arranging the heat exchanger tubes.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a heat exchanger tube portion arranged in a heat exchanger according to an embodiment of the present invention, and FIG. 2 is a sectional view of a heat exchanger tube portion in a conventional example. In the figure, 1 is a heat exchanger tube, and 2 is a primary fluid. Patent Applicant: Ishikawajima-Harima Heavy Industries Co., Ltd. Representative Patent Attorney Nobuo Kinutani Yugoi Figure 1 Figure 2 1...i.

Claims (1)

[Claims] A heat exchanger in which a primary fluid is flowed outside the heat exchanger tubes and a secondary fluid is introduced into the heat exchanger tubes, characterized in that the back surface of the heat exchanger tubes in the flow direction of the primary fluid is shaped into a streamlined shape. exchanger.