JPH0313796A - Heat transfer tube - Google Patents

Abstract

PURPOSE:To improve heat transfer performance in the operation of an air conditioner by forming spiral grooves having mutually opposite angles to a tube axis to an internal surface in a shape that the circumference of a tube is divided by an even number of 4 or more. CONSTITUTION:Spiral grooves having mutually opposite angles to a tube axis are formed to the internal surface of a heat transfer tube 3 in a shape that a circumference is divided into four. Consequently, a reversal in the direction of inclination of the grooves generated by hairpin machining is not conducted, performance is not changed by the direction of flow of refrigerant before and behind a hairpin section 11, and the performance of the whole evaporator is made better than the time of the usage of a heat transfer tube 2. Accordingly, heat transfer performance in an actual air conditioner can be enhanced without altering the direction of flow of the refrigerant or the constitution of the evaporator. When the base body refrigerant 4 condenses in the tube, a condensate 17 is collected to groove crossing sections 8, thus largely improving condensation performance.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to heat exchanger tubes.

[Prior Art] Conventionally, heat transfer tubes used in evaporators and condensers of empty and dry machines have been provided with inclined grooves or rib-like protrusions on the inner or outer surface of the tubes to increase the heat transfer area and improve the flow inside and outside the tube. Heat transfer performance has been improved by promoting turbulence.

By the way, the inner surface of a conventional heat exchanger tube is as shown in Fig. 8.
Since the slopes 11η14a, 14b or rib-like protrusions are provided, the liquid refrigerant 5 and the gas refrigerant 4 are in a state as shown in FIG. 7, and the liquid refrigerant 5 is in a state as shown in FIG. rises along the inclined groove 14a114b,
Evaporation performance is improved.

[Problems to be Solved by the Invention] However, as shown in FIG. 9, an actual heat exchanger for an air conditioner consists of a heat exchanger tube 2'' with a hairpin in the center and a pipe joint 12.
It is configured in a U-bent shape by alternately combining them. As a result, the direction of inclination of the inclined grooves 14a and 14b in the pipe is reversed with respect to the flow direction of the refrigerant before and after the hairpin part 11, and although the evaporation performance is high in the straight pipe part 10, the inverted straight pipe part 10
At ', the liquid refrigerant 5 is conversely pushed down to the lower part of the pipe m 10 a, and the evaporation performance is significantly reduced. For this reason, the evaporation performance of a conventional heat transfer tube (axisymmetric grooved tube) 2', which has two groove intersections 8 formed by grooved and welded on one side, is significantly limited.

The purpose of the present invention is to eliminate the drawbacks of the prior art described above,
The present invention aims to provide a heat exchanger tube that can improve the evaporation performance or condensation performance within the tube.

[Means and effects for solving the problems] In order to achieve the above object, in the present invention, spiral grooves in opposite directions are formed in an even number of 4 or more places in the pipe, thereby making it difficult to actually operate the air conditioner. It has improved heat transfer performance.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram showing the structure of the inner surface of the heat exchanger tube of the present invention. In this embodiment, the inner surface of the heat exchanger tube 3 has a circumference divided into four, and angles facing opposite to each other with respect to the tube axis are formed. A spiral groove is formed. In the figure, 8 is a groove intersection, 9 is a seam weld, 13 is a groove axis pitch, and 15a and 15b are inclined groove pitches.

According to the above embodiment, there is no reversal in the direction of inclination of the grooves caused by hairpin processing, and there is no change in performance depending on the flow direction of the refrigerant before and after the hairpin portion 11, and as shown in FIG. The performance of the entire vessel is better than when heat exchanger tubes 2 are used. In addition, as shown in FIG. 2, when the gas refrigerant 4 condenses in the pipe, the condensed liquid 17 is collected at the groove intersection 8, so that the liquid film thickness in the pipe is leveled, and the liquid film is Since the thermal resistance becomes smaller and the condensate 17 easily leaves the groove intersection 8, the condensing performance is greatly improved.

In addition, as shown in FIG. 3, by providing flat portions 18 having a width 18 that is twice or more the groove pitch 13 at arbitrary positions and at regular intervals, hairpin processing is possible when processing the heat exchanger tube 3 into a hairpin. The bending properties of section 11 are significantly improved.

Furthermore, by setting more groove intersections 8 (six locations in the figure) in groove machining before tube forming, as shown in Figure 4, the rolling operation during machining can be stabilized and the machining speed can be reduced. The improvement or uniformity of the processed shape is achieved, and it becomes possible to achieve cost reduction and quality improvement in heat exchanger tube manufacturing.

[Effects of the Invention] Since the present invention is configured as described above, it produces the following effects.

(1) Heat transfer performance in an actual air conditioner can be improved without changing the flow direction of the refrigerant or the configuration of the evaporator.

(2) The liquid collecting action of the condensed liquid during condensation promotes leveling of the liquid film thickness in the pipe, reducing the thermal resistance of the liquid film thickness, and
By promoting the separation of condensate from groove intersections,
Significant improvements in condensing performance can be achieved.

(3) By arbitrarily combining four or more groove intersections and an unprocessed flat part on the inner surface of the heat exchanger tube, the bending characteristics of the hairpin part can be improved.

(4) When machining grooves on heat exchanger tubes, more accurate and stable machining is possible than when the grooves intersect at two locations, and the machining speed of heat exchanger tubes increases, reducing manufacturing costs and improving quality. It can be achieved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the inner surface structure of a heat exchanger tube according to an embodiment of the present invention, and Fig. 2 shows the state when the heat exchanger tube of the present invention is used for evaporation (a) and condensation (b). Explanatory drawings, FIGS. 3 and 4 are explanatory drawings showing other embodiments of the present invention, FIG. 5 is a graph showing a comparison between the present invention and a conventional example in the evaporation characteristics of heat exchanger tubes, and FIGS. Figure 7 shows a conventional heat exchanger tube for a condenser, where (a) is a longitudinal cross-sectional view, (b) is a cross-sectional view, and Figure 8 is an explanatory diagram showing the inner surface structure of the heat exchanger tube shown in Figure 7. FIG. 9 is an explanatory diagram showing an example of a case where a conventional heat transfer tube is used in an air conditioner. 1: Smooth tube, 2.2-: Axisymmetric grooved tube, 3: Heat transfer tube, 4: Gas refrigerant, 5: Liquid refrigerant, 6: Fin, 7: Groove bottom, 8: Groove intersection, 9, Seam welding Part, 10°14 a. 15 a. 10': straight pipe section, 10a: lower surface inside the pipe, 11: hairpin section, 12: pipe joint, 13: groove axis pitch, 14b = inclined groove, 15b: inclined groove pitch, 16: fin height, 17: condensate, 18: flat part, 18' double flat part width.

Claims (1)

[Scope of Claims] 1. A heat exchanger tube having spiral grooves formed on the inner surface of the tube so as to divide the circumference of the tube into an even number of 4 or more and having opposite angles to the tube axis. 2. The heat exchanger tube according to claim 1, wherein the spiral grooves are formed at a constant pitch and flat portions are provided here and there along the tube axis direction.