JPS61280393A - Heat transfer tube - Google Patents

Abstract

PURPOSE:To improve the performance of the heat transfer tube along the whole length of the tube by a method wherein the depth of spiral grooves, provided on the inner surface of the tube, is decreased gradually from the inlet port side of the tube toward the outlet port side thereof to shorten the distance of approach run of fluid and lengthen the area of turbulent flow in the tube. CONSTITUTION:The groove 2 at a part nearest to the inlet port side of the heat transfer tube 1 is formed deeper than the groove of conventional tube, therefore, the fluid for heat exchange, which flows into the heat transfer tube 1, begins to whirl immediately along the spiral groove 2 and becomes eddy current condition near the inlet port. The distance of approach run of the fluid for heat exchange becomes shorter in this heat transfer tube 1 before. The depth of the groove 2 is formed so as to be shallower gradually toward the outlet port side of the tube and the sectional area for flowing the fluid for heat exchange is widened, therefore, the resistance of flow is reduced gradually toward the outlet port side of the tube, increase of pressure loss of the fluid may be reduced and the deterioration of flow energy may be reduced. Accordingly, better turbulent flow is generated along the whole length of the heat transfer tube 1 substantially and the heat transfer performance of the tube may become more prominent than before.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to heat exchanger tubes used in heat exchangers, and particularly to heat exchanger tubes having spiral grooves on the inner surface of the tube (hereinafter referred to as this type of heat exchanger tube). Regarding improvements.

(B) Conventional technology As a conventional technology for this type of heat exchanger tube, there is known one in which the depth of the spiral groove is constant over the entire length of the tube [for example, Publication of Utility Model Publication No. 41-24229]. .

(c) Problems to be solved by the invention This type of heat transfer tube can easily make the fluid turbulent due to the function of the spiral grooves even if the flow inside the tube is low speed, and can improve its heat transfer performance. Therefore, it has been used for a long time as a material for heat exchangers in absorption refrigerators, as shown in, for example, Japanese Patent Application Laid-Open No. 46-2490. However, when fluid flows into a tube, it does not become a small flow immediately from the entrance of the tube, but becomes a turbulent flow after a certain distance (hereinafter referred to as the run-up distance). The run-up distance is long (
This has the problem that it becomes

In view of this problem, it is an object of the present invention to provide a heat transfer tube of this type that can shorten the run-up distance and lengthen the turbulent region within the tube compared to conventional tubes.

B) Means for Solving the Problems The present invention, as a means for solving the above problems, makes the spiral groove deeper on the inlet side of the pipe than the conventional one, and increases the depth toward the outlet side. This type of heat exchanger tube is configured to gradually become smaller.

(E) Function In the heat transfer tube of the present invention, the groove on the inlet side of the tube is formed deeply and has the function (effect) of promoting swirling of the fluid flowing into the tube near the inlet. The run-up distance can be shorter than that of a conventional model. Also, the groove is the protrusion of the tube [
] Since it is formed so that it becomes gradually shallower toward the side and has the function of reducing flow resistance, it can also reduce the increase in fluid pressure loss and create a good turbulent area over almost the entire length of the pipe. is possible. therefore,
According to the present invention, the performance of this type of heat exchanger tube can be improved compared to conventional ones.

(F) Embodiment The drawing is a schematic structural diagram showing a cross section of an embodiment of a heat exchanger tube according to the present invention. In the figure, (1) is a heat exchanger tube used as a material for heat exchangers such as generators and absorbers in absorption refrigerators, and the inner surface of this heat exchanger tube has spiral grooves (2), (2). ... is formed. and,
The groove (2) is formed so that its depth I becomes gradually smaller from the inlet side (right side in the figure) to the outlet side of the tube (for example, if the inner diameter of the tube is 8.5 mm, 1.8m long, H is 0.68mtx to 0ryu]. Note that H is appropriately selected depending on the flow rate, pipe diameter, length, etc. of the heat exchange fluid flowing into the heat transfer tube (11).
+31 is a tube sheet for a heat exchanger.

Next, an example of the operation of the heat exchange fluid in the heat exchanger tube configured as described above (hereinafter referred to as the main heat exchanger tube) will be described.

The groove (2) at the part closest to the inlet side of the present heat exchanger tube +11 is deeper than that of the conventional one [for example, the H of the present heat exchanger tube is 0
．． 68mg, whereas the conventional one is 0.0
It is about 2 to 0.2 u. ], the heat exchange fluid that flows into the main heat exchanger tube (1) immediately begins to swirl along the spiral groove (2) and becomes a vortex near the inlet of the main heat exchanger tube (11). .That is, this heat exchanger tube (1
), the run-up distance of the heat exchange fluid is shorter than that of the conventional method. In addition, the groove (2) is formed to become gradually shallower toward the outlet side, and the flow cross section of the heat exchange fluid becomes wider, so the flow resistance gradually decreases toward the outlet side, and the heat exchange fluid becomes shallower. The increase in fluid pressure loss is also reduced, and the decline in flow momentum is also small. Therefore, in the present heat transfer tube (1), good turbulence is generated within the tube over almost its entire length, and its heat transfer performance is superior to that of the conventional tube. In particular, the present heat exchanger tube is suitable as a material for absorption refrigerators and other heat exchangers in which the flow rate of heat exchange fluid is limited.

Note that various types of heat exchange fluid can be used as the heat exchange fluid flowing inside the pipe, such as water or other liquids, air or other gases, or fluids that change phase such as steam.

(G) Effects of the Invention As described above, according to the present invention, the turbulence of the heat exchange fluid that has flowed into the pipe is promoted at the inlet part, and a good turbulent area can be created over almost the entire length of the pipe. This has the effect of improving the performance of heat exchanger tubes compared to conventional ones.

[Brief explanation of drawings]

The drawing is a schematic structural explanatory diagram showing a cross section of an embodiment of this type of heat exchanger tube according to the present invention. (1)...heat exchanger tube, +21, (2)...groove,
13+, (3)...Tube plate.

Claims (1)

[Claims] (1) A heat exchanger tube having a spiral groove on the inner surface of the tube, characterized in that the groove is formed so that the depth of the groove gradually decreases from the inlet side to the outlet side of the tube. .