JPS62102092A - Heat transfer tube equipped with internal grooves - Google Patents

Abstract

PURPOSE:To promote the destruction of oil film as well as the mixing of liquid refrigerant and improve the thermal efficiency of a heat transfer tube by a method wherein a groove, provided on the internal surface of the tube, is provided with small protuberances on the bottom surface thereof with a given pitch. CONSTITUTION:The groove 3 of a heat transfer tube 1, which is separated by a rib-like protuberance 2 and provided on the internal surface of the tube 1 so as to be continuous in spiral, is provided with rhombic protuberances 4, low in height and having flat surfaces on the upper surfaces thereof, on the bottom surface thereof regularly along the lengthwise direction thereof. These protuberances 4 are preferable to have heights which are not spoiling the flow of liquid refrigerant 5, caused by the spiral effect of the groove 3, or the heights lower than one half of the depth of the groove 3 while the edge angle of the protuberance with respect to the flow of the refrigerant is preferable to be as sharp as possible. A distance between the protuberance 4 and the side surface of the rib-like protuberance 2 separating the groove 3 is preferable to be 1/4 of the bottom width of the groove 3 at the maximum. The liquid refrigerant 5 and gas refrigerant are in the condition of being mixed since the groove 3 or the rib-like protuberance 2 is provided and whereby evaporation of the refrigerant 5 may be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in internally grooved heat exchanger tubes used in heat exchangers of air conditioners and the like.

[Prior art and its problems] Conventionally, heat transfer tubes used in heat exchangers of air conditioning equipment, etc. have spiral grooves or rib-like protrusions on their inner surfaces to increase the heat transfer area and improve the flow inside the tube. Heat transfer performance has been improved by promoting turbulence. However, as evaporation progresses in the evaporator, the concentration of refrigerating machine oil in the liquid refrigerant increases, and an oil layer is observed to form on the inner surface of the heat exchanger tube at the rear end of the heat exchanger tube. In addition, the higher the viscosity of the frozen frozen oil, the more oil film formation occurs from the early stage of the evaporation process, and the oil film thickness becomes larger, resulting in a greater reduction in the thermal efficiency of the heat exchanger tube. As a result, the length of the heat transfer tubes required to obtain the desired heat exchange amount of the evaporator increases, resulting in problems such as an increase in the cost of the evaporator and the inability to design it compactly.

[Objective of the Invention 1] An object of the present invention is to provide an improved refrigerant-in-tube type heat transfer tube that can eliminate the drawbacks of the prior art described above and improve the evaporation or condensation performance within the tube.

[Summary of the Invention] The gist of the present invention is to improve the thermal efficiency of heat exchanger tubes by providing small protrusions at a constant pitch on the bottom of the grooves provided on the inner surface of the pipe, thereby promoting the destruction of the oil film and stirring of the liquid refrigerant. The reason is that we have made it possible to do so.

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

FIG. 1 shows a heat exchanger tube 1 having a spirally continuous groove 3 separated by rib-like protrusions 2 on its inner surface, on the bottom surface of the groove 3,
As shown in FIG. 2, diamond-shaped protrusions 4 with low heights and flat upper surfaces are provided regularly along the longitudinal direction. .

These protrusions 4 should have a height that does not obstruct the flow of liquid refrigerant 5 due to the spiral effect of the grooves 3, for example, 1/2 or less of the depth of the grooves 3, and the tip angle with respect to the flow should be as acute as possible. is desirable.

Further, it is desirable that the distance between these protrusions 4 and the side surface of the rib-like protrusion 2 that separates the groove 3 is at most 1/4 or less of the bottom width of the groove 3.

In such a heat exchanger tube, grooves 3 or rib-like projections 2
Therefore, the liquid refrigerant 5 and the gas refrigerant are in a mixed state, and their evaporation is promoted.

As evaporation progresses, the oil concentration in the liquid refrigerant increases and the flow of the liquid refrigerant 5 is obstructed, and there is a risk that an oil film will adhere to the bottom of the groove. Therefore, the speed of the liquid is increased or decreased before and after the projections 4, thereby increasing the destruction of the oil film and the promotion of agitation between the oil and the liquid refrigerant, thereby further improving the thermal efficiency of the heat transfer tube.

This heat transfer surface can also be used for condensation, but since the projections 4 are provided to increase the heat transfer area, the heat transfer performance can also be improved in the case of condensation.

3 and 4 show other examples of the protrusion 4, the example in FIG. 3 is a case where a triangular protrusion 4 is provided, and the example in FIG. 4 is a case where the protrusion 4 is provided with a change in thickness. It shows the case.

The protrusion 4 does not have to be angular as shown in the illustrated example;
The shape may be formed by a combination of straight lines or curved lines.

[Effects of the Invention] According to the heat exchanger tube of the present invention, since the small protrusions are provided on the bottom of the inner groove, the surface area not only increases and improves evaporation and condensation performance, but also improves the performance of refrigerators, etc. during the evaporation process. It is possible to reduce the oil film thickness and significantly improve the agitation of the refrigerant liquid and oil, thereby reducing the cost and realizing a compact design of the evaporator.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the heat exchanger tube according to the present invention,
FIG. 2 is a partially enlarged view, and FIGS. 3 and 4 are views showing other examples of the protrusions. 1: heat transfer tube, 2: rib-like projection, 3: groove, 4: projection, 5: liquid refrigerant. Agent Patent Attorney Fujio Sato 1 Figure Legs 2 Figure A 3
4 countries

Claims (1)

[Claims] (1) A heat exchanger tube having a plurality of spirally continuous grooves on its inner surface, characterized in that protrusions are provided at a constant pitch on the bottom surface of the grooves.