JPH10132424A - Flat heat exchanger tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an efficient heat exchange in all refrigerant paths by making the width in the direction crossing the direction the flow of wind gradually smaller toward the lee side from the windward side while the cross sections of a plurality of refrigerant passages are gradually reduced toward the lee side from the windward side. SOLUTION: The diameters of refrigerant passages p1, p2, p3 and p4 are arranged to be gradually smaller toward the lee side from the windward side and hence, the cross sections of the refrigerant passages are reduced toward the lee side. The refrigerant passages with the larger cross section have the larger flow rate of a refrigerant. In other words, in flat heat exchanger tube 1, the flow rate of the refrigerant is adjusted according to the position in the direction of the flow of wind. As air flowing in the perimeter of the flat heat exchanger tube 1 is cooled gradually toward the lee side, the degree of heat exchange is lowered. Thus, in the flat heat exchanger tube 1, in view of the fact that the degree of heat exchange lowers the more on the lee side, the cross section is made the smaller in the refrigerant passages positioned on the lee side to reduce the flow rate of the refrigerant. This can prevent drop in the efficiency of the heat exchange on the lee side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flat heat transfer tube suitable for use in an evaporator of an air conditioner.

[0002]

2. Description of the Related Art Conventionally, as a flat heat transfer tube of this type, as shown in FIG.
It is known that 1 ', p2', p3 ', p4' are arranged along the direction of wind flow. The flat heat transfer tube 100 has a constant width w from the windward side to the leeward side.

In the air conditioner, usually, a plurality of flat heat transfer tubes 100 having a certain length in the vertical direction are installed at a predetermined interval from each other, or
Two long ones are installed in a meandering state.

[0004]

Since the air flowing around the flat heat transfer tube is gradually cooled downwind,
The difference (Δt = ta−tr) between the low pressure equivalent saturation temperature tr and the air temperature ta in each refrigerant passage, that is, each refrigerant passage p1 ′, p2 ′,
The temperature difference between the refrigerant inside p3 'and p4' and air is shown in FIG.
As shown in (b), the refrigerant passage located on the leeward side (simply represented as a passage in the drawing) becomes smaller. As described above, since Δt becomes smaller toward the leeward side, the amount of heat exchange also decreases.

However, the conventional flat heat transfer tube 100
Since the refrigerant passage located on the leeward side and the refrigerant passage located on the lower side also have the same cross-sectional area, a region that is not as gaseous as the refrigerant passage located on the leeward side, that is, a liquid-gas two-phase region increases, and heat There is a problem that the exchange efficiency is poor. FIG.
(c) shows the area ratio of the saturated region to the total surface area in each refrigerant passage. The portion below the curve is the saturated region, that is, the liquid-gas two-phase region, and the portion above the curve is the gas region. From this figure, it can be seen that the saturation area increases toward the leeward side, and therefore, the heat exchange efficiency becomes worse toward the leeward side.

When the air cools, dew condensation occurs on the surface of the heat transfer tube, and this dew causes the air passage having a certain width to be narrowed. As a result, there is a problem that ventilation resistance increases and pressure loss increases. FIG.
The vertical axis of (d) shows the cumulative ventilation resistance at each refrigerant passage position of the conventional flat heat transfer tube. As is clear from this figure, the cumulative ventilation resistance increases proportionally toward the leeward side. It can be seen that the pressure loss is large and the pressure loss is large.

Therefore, an object of the present invention is to enable efficient heat exchange in all refrigerant passages,
It is an object of the present invention to provide a flat heat transfer tube capable of reducing the accumulated ventilation resistance and therefore the pressure loss even when dew condensation occurs on the surface.

[0008]

According to a first aspect of the present invention, there is provided a flat heat transfer tube having a plurality of refrigerant passages arranged along a flow direction of a wind. The width in the direction intersecting with the flow direction of the wind is reduced as going from the windward side to the leeward side, and the cross-sectional area of the plurality of refrigerant passages is also reduced as going from the windward side to the leeward side. I have.

In the flat heat transfer tube of the present invention as well, like the conventional flat heat transfer tube shown in FIG. 2, the difference between the air temperature and the refrigerant temperature becomes smaller toward the leeward side, so that the amount of heat exchange also becomes leeward. The refrigerant passage on the side is smaller. However, unlike the conventional one shown in FIG. 2, the cross-sectional area of the refrigerant passage is smaller toward the leeward side, and thus the flow rate of the refrigerant is also smaller toward the leeward side. Therefore, the heat exchange efficiency does not decrease even in the leeward side refrigerant passage.

According to the present invention, the width of the flat heat transfer tube in the direction intersecting with the flow direction of the wind is large on the windward side and small on the leeward side, so that the width of the air passage increases toward the leeward side. spread. Therefore, even if dew condensation occurs on the surface of the flat heat transfer tube, a sufficient air passage width is secured, and the accumulated ventilation resistance, that is, the pressure loss, is reduced.

In addition, the width of the flat heat transfer tube is increased on the windward side,
By making it small on the leeward side, the air flows easily, and the generation of vortices, and hence the generation of sound, on the leeward side of the flat heat transfer tube is suppressed.

Further, the flat heat transfer tube according to the present invention is characterized in that it has a streamlined cross-sectional shape.

According to the second aspect of the present invention, since the flat heat transfer tube has a streamlined cross-sectional shape, air flows along the surface of the flat heat transfer tube without separation, so that vortices are generated on the leeward side. Therefore, generation of sound is prevented well.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments.

FIG. 1A shows a cross section of a flat heat transfer tube 1 according to an embodiment of the present invention. The flat heat transfer tube 1 is formed by extruding aluminum, and has a streamline sectional shape in which one side is wide and the other side is narrow.
The flat heat transfer tube 1 is arranged substantially parallel to the flow of wind, with the wide part on the windward side and the narrow part on the leeward side. In the air conditioner, a plurality of flat heat transfer tubes 1 having a certain length are provided.
May be arranged adjacent to each other at a predetermined interval, or 1
Two long flat heat transfer tubes 1 may be arranged in a meandering manner.

As shown in FIG. 1 (a), a plurality of cylindrical refrigerant passages p1, p1 are formed in the flat heat transfer tube 1 in the flow direction of the wind.
p2, p3, and p4 are arranged in a line. The refrigerant passage p
The diameter of 1, p2, p3, and p4 is gradually reduced from the windward side to the leeward side. Therefore, the cross-sectional area of each refrigerant passage becomes smaller toward the leeward side. The larger the cross-sectional area of the refrigerant passage, the larger the refrigerant flow rate. That is, in the flat heat transfer tube 1, the flow rate of the refrigerant is adjusted according to the position in the flow direction of the wind.

The graph shown in FIG. 1 (b) shows the difference (Δt = ta−tr) between the low pressure equivalent saturation temperature tr and the air temperature ta in each of the refrigerant passages p1, p2, p3, p4, that is, each refrigerant passage. The temperature difference between the internal refrigerant and the air around the flat heat transfer tube 1 is shown. Since the air flowing around the flat heat transfer tube 1 is gradually cooled as going downwind, as in the case of the conventional flat heat transfer tube 100 shown in FIG. The amount of replacement is reduced.

In the flat heat transfer tube 1, in consideration of the fact that the amount of heat exchange decreases on the leeward side, the cross-sectional area decreases on the leeward side of the refrigerant passage, thereby reducing the refrigerant flow rate. Therefore, a decrease in heat exchange efficiency on the leeward side can be prevented.

FIG. 1C shows the area ratio of the saturated region (ie, the liquid-gas two-phase region) to the total surface area in each refrigerant passage.
This is a comparison between the present embodiment and a conventional example.
The solid line relates to the flat heat transfer tube 1 according to the present embodiment, and the dotted line relates to the conventional flat heat transfer tube 100. In the figure, the portion below the curve is the liquid-gas two-phase region, and the portion above the curve is the gas region. As is clear from this figure, in the conventional flat heat transfer tube 100, the area ratio of the saturated region increases toward the leeward side, whereas in the flat heat transfer tube 1 of the present embodiment, the flattened heat transfer tube 100 is located on the leeward side. The area ratio of the saturation region in the three refrigerant passages p2, p3, and p4 is kept substantially constant, and it can be seen that heat exchange is performed efficiently.

FIG. 1D shows the cumulative ventilation resistance of the flat heat transfer tube 1 of the present embodiment in comparison with the cumulative ventilation resistance of the conventional flat heat transfer tube 100. A solid line indicates the present embodiment, and a dotted line indicates a conventional example. Although the accumulated draft resistance of the flat heat transfer tube 1 according to the present embodiment is larger on the windward side than in the past, it is kept substantially constant throughout the flat heat transfer tube 1, and finally the cumulative draft resistance on the leeward side. Is greatly reduced than before. The reason for this is that the width of the flat heat transfer tube 1 according to the present embodiment is smaller toward the leeward side, so that the air passage width becomes wider toward the leeward side. This is because a wide air passage width is ensured. Further, since the surface of the flat heat transfer tube 1 is streamlined, the smooth flow of the wind also contributes to the reduction of the accumulated ventilation resistance.

Further, since the flat heat transfer tube 1 is streamlined, there is an advantage that no vortex is generated downwind of the flat heat transfer tube 1 and therefore no sound is produced.

In the above embodiment, the refrigerant passage p
Although the shapes of 1, p2, p3, and p4 are cylindrical, they may be rectangular tubes or other shapes.

[0023]

As is clear from the above, according to the present invention, the cross-sectional area of the refrigerant passage of the flat heat transfer tube is increased on the windward side,
Since the leeward side is made smaller and the refrigerant flow rate is adjusted according to the position in the flow direction of the wind, the saturation region in the refrigerant passage increases even on the leeward side where the difference between the refrigerant temperature and the air temperature becomes smaller. Can be prevented, and the heat exchange efficiency can be improved more than before.

Further, in the flat heat transfer tube of the present invention, the width in the direction intersecting the flow direction of the wind is large on the windward side and small on the leeward side, so that the width of the air passage increases toward the leeward side. Therefore, even if dew condensation occurs on the surface of the flat heat transfer tube, a sufficient air passage width can be secured, and the accumulated ventilation resistance, that is, the pressure loss is reduced. As a result, it is possible to increase the amount of air when the motor torque (is constant, while it is possible to reduce the motor torque when the amount of air is constant.

Further, the width of the flat heat transfer tube is increased on the windward side,
By making it small on the leeward side, the air can easily flow smoothly, and the generation of vortices, and hence the generation of sound, on the leeward side of the flat heat transfer tube is suppressed.

Further, the flat heat transfer tube according to the second aspect of the present invention has a streamlined cross-sectional shape, so that air flows without separating along the surface of the flat heat transfer tube. Therefore, generation of sound can be favorably prevented.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams illustrating the present invention, in which FIG. 1A is a cross-sectional view of a flat heat transfer tube according to an embodiment of the present invention, and FIG. A graph showing a temperature difference, (c) is a graph showing an area ratio of a saturation region to a total surface area in each refrigerant passage, and (d) is a graph showing an accumulated ventilation resistance in each part of the flat heat transfer tube.

2A and 2B are diagrams illustrating a conventional flat heat transfer tube, wherein FIG. 2A is a cross-sectional view of the conventional flat heat transfer tube, and FIG. 2B is a temperature difference between refrigerant and air in each refrigerant passage of the conventional flat heat transfer tube. (C) is a graph showing the area ratio of the saturated region to the total surface area in each refrigerant passage, and (d) is a graph showing the cumulative ventilation resistance in each part of the flat heat transfer tube.

[Explanation of symbols]

 1: Flat heat transfer tubes, p1, p2, p3, p4 ... refrigerant passages.

Claims (2)

[Claims] 1. A flat heat transfer tube (1) having a plurality of refrigerant passages (p1, p2, p3, p4) arranged along the flow direction of a wind, the width in a direction intersecting the flow direction of the wind. However, the cross-sectional area of the plurality of refrigerant passages (p1, p2, p3, p4) decreases from the windward side to the leeward side, and the cross-sectional area of the plurality of refrigerant passages (p1, p2, p3, p4) decreases. Flat heat transfer tube. 2. The flat heat transfer tube according to claim 1, having a streamlined cross-sectional shape.