Heat exchanger fins of an air conditioner

DESCRIPTION

Fins of the heat exchanger of an air conditioner.

Background of the invention

Field of the invention

The present invention relates to the heat exchanger of an air conditioner, and more in particular to the heat exchanger of an air conditioner in which projections are formed on a flat fin.

Description of the previous technique

A heat exchanger of an air conditioner of the prior art includes, as illustrated in Figure 1, a plurality of flat fins 1 arranged in parallel and with a predetermined spacing, and heat transfer tubes 2 arranged perpendicular to the fins. 1, zigzag shape. The air stream moves between the fins 1 in a direction represented by an arrow to carry out a heat exchange with the fluid inside the heat transfer tubes 2.

Furthermore, with regard to the characteristics of the heat flow around the fins, and as illustrated in Figure 2, a temperature limotrophic layer 3 on the heat transfer surface of the fins 1 becomes thicker, in proportion to the square root of a distance from an inlet end of the air stream. Consequently, there is a drawback that the heat transfer rate between the air stream and the fins is greatly reduced as the distance from the inlet end of the air stream increases, thereby decreasing the efficiency of the air stream. heat transfer from the heat exchanger.

There is still another drawback in the sense that, when the air stream passes at low speed over the heat transfer tubes 2, a cavitation zone 4 is generated in the posterior area of ​​each heat transfer tube 2 (i.e. , the shaded area of ​​figure 3), which causes a considerable decrease in the heat transfer rate in the cavitation zone 4, there is a decrease in the heat transfer performance of the heat exchanger.

A prior art intended to overcome the aforementioned drawbacks is described in Japanese Utility Model Laid-Open Application No. Sho. 55-110995, in which, as illustrated in Figure 4, the fins of an air conditioner are composed of groups of slit-forming projections 5a, 5b, 5c, 5d, 5e and 5f, arranged in a vertical spacing formed between heat transfer tubes 2.

In other words, and as illustrated in figure 5, the projections 5a, 5c and 5e protrude from a surface of the fin 1 as a result of a cutting and bending process, said projections being arranged in a predetermined interval, while the remaining projections 5b, 5d and 5f project from the opposite surface of the fin 1, being arranged between the projections 5a, 5c and 5e.

The fins 1 formed with the groups of projections 5a, 5b, 5c, 5d, 5e and 5f can provide a higher heat transfer performance than the fins devoid of projections. The upstream ridges 5a and 5b provide high heat transfer performance because they form a thin temperature boundary layer. However, the performance of heat transfer decreases in the downstream ribs 5c, 5d, 5e and 5f, since said ribs 5c, 5d, 5e and 5f are arranged in the temperature boundary layer formed by the shoulders 5a and 5b. .

There is another problem, in that a cavitation zone is generated in which the air stream does not flow on a rear side of the heat transfer tube 2, which reduces the efficiency of heat transfer.

There is yet another problem, in that the fin has a limited heat transfer area, and furthermore it bends relatively easily. Summary of the invention

The present invention relates to a heat exchanger adapted to be used in an air conditioner. The heat exchanger includes a plurality of spaced parallel fins adapted to conduct air flow between each pair of adjacent fins. Heat transfer tubes extend through the fins, perpendicular thereto, and conduct a heat transfer fluid. The fins comprise first, second, third and fourth groups of slit-forming ribs disposed between each pair of vertically spaced tubes. The first and third groups are arranged below the first tube of the pair, and the second and fourth groups are arranged above the second tube of the pair. The third group was positioned behind the first group in relation to the direction of fluid flow, and the fourth group was positioned behind the second group. An intermediate crevice-forming boss was located behind the first and second groups and in front of the third and fourth groups. Each of the ribs extends transversely in relation to the direction of flow of the fluid. The projections of each first and second groups project from the fin to respective heights that become progressively greater in the direction of fluid flow. The projections of every third and fourth groups project from the fin to respective heights that become progressively greater in the direction of fluid flow.

Alternatively, the projections of the third and fourth groups could project from the fin to heights that become progressively lower in the direction of fluid flow.

Preferably, each group includes some ridges that extend from a first side of the fin and some ridges that extend from a second side of the fin in an alternating relationship with respect to the ridges on the first side and with respect to the flow direction of the fluid. .

Preferably, each rib is separated from adjacent ribs through a solid portion of the fin.

Preferably, the projections of the first and third groups extend in a generally radial direction with respect to the first tube, and the projections of the second and fourth groups extend in a generally radial direction with respect to the se2

ES 2 149 079 A1 second tube.

Brief description of the drawings

For a better understanding of the nature and objects of the invention, reference should be made to the following detailed description in conjunction with the accompanying drawings, in which:

Figure 1 is a perspective view of a heat exchanger according to the prior art;

Figure 2 is an enlarged view illustrating a thermal fluid feature around a flat fin of Figure 1;

Figure 3 is an enlarged view illustrating a characteristic of the thoracic fluid around a heat transfer tube of Figure 1;

Figure 4 is a plan view of a flat fin of another heat exchanger according to the previous technique;

Figure 5 is a sectional view taken along line AA of Figure 4;

Figure 6 is a side view illustrating a flat fin of a heat exchanger according to the present invention;

Figure 7 is an enlarged view of part B of Figure 6;

Figure 8 is a sectional view taken along line CC of Figure 7; and Figure 9 is a sectional view illustrating the height difference of the projections according to another embodiment of the present invention.

Detailed description of the preferred embodiments of the invention

A detailed description of the preferred embodiments of the heat exchanger of an air conditioner according to the present invention is provided below, in which reference is made to the accompanying drawings.

Throughout all the drawings the same reference numbers and symbols are used to designate those equal or equivalent parts or parts of the prior art.

Reference number 20 (and box B) represents a set of slit-forming ridges that provide slits that extend transversely of the flow direction of the air stream. Each assembly 20 is arranged between two vertically spaced heat transfer tubes 2A, 2B and arranged generally radially with respect to the central axes of respective heat transfer tubes 2, so that the air stream flowing along of each surface of the fin 1 is disturbed (ie, made turbulent) and mixed. This reduces the cavitation zone that is generated on a back side of the heat transfer tubes 2 and increases the heat transfer efficiency, providing better heat transfer performance.

In other words, and as illustrated in Figures 6, 7 and 8, assembly 20 includes first, second, third and fourth groups of slit-forming projections 30, 40, 50, 60. The projections of each group 30- 60 are separated by solid parts 21 of the fin, and are inclined obliquely with respect to a central plane P that extends in an intermediate position between the two tubes 2, as can be seen in figure 6.

The first group 30 comprises four shoulders 31-34. The shoulders 31 and 33 project from a first side 1A of the fin, and the shoulders 32 and 34 project from a second side 1B of the fin. The first group 30 was located along an upstream half of a lower portion of tube 2A. That is, the shoulder 31 is disposed adjacent the front side 2A 'of a respective tube 2A, and the shoulder 34 is disposed approximately midway between the front and rear sides 2A', 2A "of the tube 2A. The projections 31-34 have a progressively shorter length L from the projection 31 to the projection 34, as seen in Figure 6. The first group of projections 30 causes the disturbance of the air stream as it passes through the upstream half of the lower part of the tube 2A.

The second group 40 comprises four shoulders 41-44. The bosses 41 and 43 project from a first side 1A of the fin, and the bosses 42 and 44 project from a second side 1B of the fin. The second group of ribs 40 was located along an upstream half of an upper portion of tube 2B. That is, the shoulder 41 is disposed adjacent the front side 2B 'of a respective tube 2B, and the shoulder 44 is disposed approximately midway between the front and rear sides 2B', 2B "of the tube 2B. The ribs 41-44 are progressively shorter in length from the rib 41 to the rib 44. The inclination of the ribs 41-44 is such that they converge in a forward direction (ie, upstream) with the respective ribs 31- 3. 4. The second group 40 produces the disturbance of the air stream as it passes through the upstream half of the upper part of the tube 2B.

The third group 50 comprises four shoulders 51-54. Said projections are inclined so that they are located substantially parallel to the projections 41-44 of the second group. The bosses 51 and 53 project from a first side 1A of the fin, and the bosses 52 and 54 project from a second side 1B of the fin. The third group 50 is located along a downstream half of a lower part of the tube 2A. That is, the shoulder 51 is disposed approximately midway between the front and rear sides 2A ', 2A "of the tube 2A, and the shoulder 54 is disposed adjacent the rear side 2A" of the tube 2A. The ribs 51-54 have a progressively shorter length from the rib 51 to the rib 54. The third group of ribs 50 causes the disturbance of the air stream as it passes through the downstream half of the lower part of the tube 2A.

The fourth group 60 comprises four shoulders 61-64. Said projections are inclined relative to the plane P, so that they extend parallel to the first group of projections 31-34. The ridges 61 and 63 project from a first side 1A of the fin, and the ridges 62 and 64 project from a second side 1B of the fin. The fourth group of ribs 60 is located along a downstream half of an upper portion of tube 2B. That is, the projection 61 is disposed approximately midway between the front and rear sides 2B ', 2B "of the tube 2B, and the projection

ES 2 149 079 A1 is located adjacent to the rear side 2B "of the tube 2B. The ribs 61-64 are progressively shorter in length from the rib 61 to the rib 64. The fourth group of ribs 60 disturbs the air stream as it passes through the downstream half of the top of tube 2B.

An intermediate shoulder 70 projects from the first side 1A of the fin 1 and extends perpendicular to the plane P, along a plane P 'containing the axes of the tubes 2A, 2B. The intermediate projection 70 produces the disturbance of the air flow that moves between the first and third groups 30, 50, and also produces the disturbance of the air flow that moves between the second and fourth groups 40, 60.

Following the above, the solid parts 21 of the fin are located on both sides of each of the projections of the four groups of projections, as in the intermediate projection.

The widths W of the ribs of the first, second, third and fourth groups are identical, and narrower than the width W 'of the intermediate rib 70 (see FIG. 7).

Each shoulder has a height dimension defined by the distance through which the shoulder projects from a respective side of the fin. As can be seen in figure 8, the projections of each of the four groups have a progressively greater height H1-H4 in the direction of the air flow S. That is, the heights increase from left to right, follow figure 8. Furthermore, the intermediate shoulder 70 has a height greater than that of any of the other shoulders.

In other words, the heights of the first ridges (31, 41, 51, 61) are less than the heights of the second ridges (32, 42, 52, 62). Said second projections have a lower height than the third projections (33, 43, 53, 63), and the third projections have a lower height than the fourth projections (34, 44, 54, 64). All bosses in groups 30-60 have a height less than intermediate boss 70, as illustrated in Figure 8.

It will be appreciated that, as the air flows in the direction S, a part of the air flow traveling along the first side 1A of the fin is transferred to the second side 1B of the fin through the projections 31, 41, 33, 43, 70, 51, 61, 53, 63. Furthermore, a part of the air flow that travels along the second side 1B of the fin is transferred to the first side 1A through the projections 32, 42, 34, 44, 52, 62, 54, 64. The operation of the heat exchanger described in relation to Figures 6-8 is explained below. When the air flows in the S direction, it becomes turbulent as it passes through the first, second, third and fourth groups of ribs and the intermediate rib 70. The air stream is simultaneously divided into respective air flows F1, F2 which they run around each tube 2, as shown in figure 6. These air flows join at a point adjacent to the downstream or rear side of the tube. This produces a mixing action.

Due to the fact that the air becomes turbulent, the cavitation zone formed on the back side of each tube 2 decreases and the heat transfer efficiency on the back side increases.

The inclinations of the first and second projections 31, 33, 41, 43, 51, 53, 61, 63 is such that part of the air stream flowing along the first surface 1A is transferred to the second surface 1B. Furthermore, the inclinations of the third and fourth bosses 32, 34, 42, 44, 52, 54, 62, 64 is such that part of the air stream flowing along the second surface is transferred to the first surface. The following describes the operation of the heat exchanger of an air conditioner constructed according to the embodiment of the present invention.

When the air stream flows between the fins 1 in the direction of an arrow S illustrated in figure 8, it becomes turbulent as it passes through the first, second, third and fourth groups 30, 40, 50, 60, 70 of set 20.

The flowing air stream is simultaneously divided into two streams F1, F2, which are then joined together to create a mixed air stream.

By becoming turbulent, the air stream in effect reduces the cavitation zone on the rear side of each heat transfer tube 2, thus increasing the efficiency of heat transfer from said rear side.

Furthermore, a part of each flow travels along the first surface 1A and another part travels along the second surface 1B. Part of these flows are transferred from one side to the other between the first and second sides 1A, 1B of the fin through the slits formed by the projections, as shown by the arrows in Figures 8 and 9.

The arrangement of the projections, following which they project from opposite sides of the fin in an alternate relationship and at progressively varying heights, increases the effect of the temperature boundary layer and minimizes pressure drops from the third side, thereby which increases the efficiency of heat exchange.

Furthermore, the arrangement of the projections, following which they extend generally radially in relation to the tubes, causes the fluid flow to be guided to points located behind the tubes, thus reducing cavitation zones.

The ribs also serve to increase the efficiency of heat transfer from the rear of the heat transfer tubes 2 and to expedite the flow of heat to the heat transfer tubes 2.

Although the above description describes the embodiment of a heat exchanger of an air conditioner in which the projections of the third and fourth groups 50, 60 have a gradually increasing height, the present invention is not limited to said embodiment.

As an example, and in the form of another embodiment shown in Figure 9, the projections of the third and fourth groups 50, 60 have a height that gradually decreases in the direction of fluid flow.

In other words, the heights of the bosses 31 and 41 are equal to those of the bosses 54, 64

ES 2 149 079 A1 (see figure 9). The heights of the bosses 32, 42 are equal to those of the bosses 53, 63. The heights of the bosses 33, 43 are equal to those of the bosses 52, 62. The heights of the bosses 34 and 44 are equal to the of the shoulders 51, 61.

These and other changes and modifications are intended to fall within the spirit and scope of the invention, as defined in the appended claims.

As the foregoing remains evident, there is an advantage in the fact that the groups of projection elements are formed radially around the periphery of the heat transfer tubes, open towards the approaching air stream and projecting from the surfaces. internal and external flat fins at predetermined angles and at different heights, whereupon said projection elements serve to thoroughly mix the moving air stream and make it turbulent in order to effectively reduce cavitation zones that are generated at the back of the heat transfer tubes, increasing even more efficient heat transfer.

There is an additional advantage that the heat transfer rate of each heat transfer tube is increased.