FIN-TUBE HEAT EXCHANGER, FIN FOR HEAT EXCHANGER, AND HEAT PUMP APPARATUS
A fin-tube heat exchanger 1 includes a plurality of fins 3 arrayed spaced apart from and parallel to each other so as to form gaps for allowing a first fluid to flow therethrough, and a plurality of heat transfer tubes 2 penetrating the plurality of fins 3 and for allowing a second fluid to flow therethrough. The plurality of heat transfer tubes 2 includes first heat transfer tubes 2A and second heat transfer tubes 2B arranged in a predetermined row direction that intersects the flow direction of the first fluid. The fins 3 have protrusions 5 each disposed between a first heat transfer tube 2A and a second heat transfer tube 2B, for guiding the first fluid toward the first heat transfer tube 2A side and the second heat transfer tube 2B side. The equivalent diameter of the protrusion 5, as viewed in the axis direction of the heat transfer tubes 2, is equal to or greater than the outer diameter of the heat transfer tubes 2.
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The present invention relates to fin-tube heat exchangers, fins for heat exchangers, and heat pump apparatuses.
BACKGROUND ARTConventionally, fin-tube heat exchangers have been used for various apparatuses such as air conditioners, freezer-refrigerators, dehumidifiers, and hot water heaters. A fin-tube heat exchanger is composed of a plurality of fins that are arranged parallel to each other and spaced apart with a predetermined gap, and heat transfer tubes that extend through these fins.
Known fin-tube heat exchangers include ones with various fin shape designs so as to, for example, enhance heat transfer and reduce pressure loss. For example, in a fin-tube heat exchanger, the leeward side of the heat transfer tube usually becomes a dead fluid zone, in which the heat transfer coefficient is locally low. In view of this, there are known fin-tube heat exchangers having fins provided with protuberances on the surfaces of the fins so as to reduce the dead fluid zone.
For example, JP 7-239196 A discloses a fin-tube heat exchanger that uses a fin on the surface of which a large number of very small dimples are provided. Specifically, it is disclosed that, as illustrated in
JP 63-294494 A discloses a fin-tube heat exchanger in which protuberances in a triangular pyramidal shape are provided on the surface of the fins. In this heat exchanger, triangular pyramidal-shaped protuberances 111 are provided on both sides of each heat transfer tube 112, as illustrated in
The heat exchanger disclosed in JP 63-294494 A (see
JP 6-300474 A discloses a fin-tube heat exchanger in which quadrangular pyramidal-shaped protrusions are provided on the surface of each fin. In this heat exchanger, as illustrated in
In the heat exchanger disclosed in JP 6-300474 A (see
JP 2002-90085 A discloses a fin-tube heat exchanger that uses a fin 105 in which raised parts 106 are formed, as illustrated in
It has been known that, in the fin-tube heat exchanger, if the velocity of the fluid is increased to raise the heat transfer coefficient for the purpose of increasing the amount of heat transfer between the refrigerant and the fluid (for example, the air), the pressure loss when the fluid passes through the heat exchanger also increases, so the mechanical power required for the fan for causing the fluid to flow becomes too high. In other words, there is a trade-off between pressure loss and heat transfer coefficient, which is an indicator of heat transfer performance. As an attempt for the fin-tube heat exchanger to achieve both good heat transfer performance and low pressure loss, various types of heat exchangers that employ a corrugated fin, in which a plate-shaped fin is bent in a wave-like shape, have been proposed.
For example,
In recent years, demands for reducing energy consumption of heat pump apparatuses used for hot water heaters and air conditioners have been growing due to various issues such as urban heat island issues, natural resource issues, and global environment issues. For further reduction in energy consumption of a heat pump apparatus, it is essential to improve the heat exchanger, as well as the compression mechanism and the expansion mechanism. Specifically, a fin-tube heat exchanger that achieves better heat transfer performance and lower pressure loss than the one that uses a corrugated fin has been desired.
The present invention has been accomplished in view of the foregoing circumstances, and it is an object of the invention to provide a fin-tube heat exchanger that has excellent heat transfer performance and at the same time shows low pressure loss. It is another object of the invention to provide a heat pump apparatus that has the fin-tube heat exchanger. It is yet another object of the invention to provide a fin that suitably can be employed for the fin-tube heat exchanger.
Accordingly, the present invention provides a fin-tube heat exchanger for exchanging heat between a first fluid and a second fluid, including:
a plurality of fins arranged spaced apart from and parallel to each other so as to form a space or spaces for allowing the first fluid to flow therethrough; and
a plurality of heat transfer tubes penetrating the plurality of fins, for allowing the second fluid to flow therethrough, wherein:
the plurality of heat transfer tubes include a first heat transfer tube and a second heat transfer tube arranged in a predetermined row direction that intersects with a flow direction of the first fluid;
the first heat transfer tube and the second heat transfer tube are adjacent to each other with respect to the row direction;
each of the fins has a protrusion formed between the first heat transfer tube and the second heat transfer tube, the protrusion guiding the first fluid toward a first heat transfer tube side and a second heat transfer tube side; and
the equivalent diameter of the protrusion, as viewed in an axis direction of the heat transfer tubes, is equal to or greater than the outer diameter of the heat transfer tubes.
The present invention also provides a fin that is used for the just-mentioned fin-tube heat exchanger.
The present invention also provides a heat pump apparatus including:
a compressor for compressing a refrigerant;
a radiator for cooling the refrigerant compressed by the compressor;
an expansion mechanism for expanding the refrigerant cooled by the radiator; and
an evaporator for evaporating the refrigerant expanded by the expansion mechanism, wherein
at least one of the evaporator and the radiator includes the above-described fin-tube heat exchanger.
The foregoing fin-tube heat exchanger according to the present invention aims at enlarging the heat transfer area in the fin and at the same time hindering development of a thermal boundary layer and a velocity boundary layer, by forming a protrusion with a large surface area between the first heat transfer tube and the second heat transfer tube. By enlarging the heat transfer area and hindering development of the boundary layers, the heat transfer performance of the fin-tube heat exchanger is improved. In addition, the equivalent diameter of the protrusion, as viewed in the axis direction of the heat transfer tubes, is equal to or greater than the outer diameter of the heat transfer tubes. In other words, when the protrusion is orthogonally projected onto a plane parallel to the plurality of fins, the area of the image of the protrusion appearing on the plane becomes greater than the cross-sectional area of the heat transfer tube. Such a protrusion makes it possible to gain a sufficient surface area of the fin. Moreover, the protrusion with a relatively large size has the effect of increasing the flow velocity on the first fluid in the flat region between the protrusion and the first heat transfer tube, or in the flat region between the protrusion and the second heat transfer tube. An increased flow velocity is desirable because the heat transfer coefficient accordingly becomes high. In particular, it allows the side face portion in the outer circumferential surface of heat transfer tube (including the outer circumferential surface of the fin collar surrounding the heat transfer tube) that faces the protrusion to contribute to the heat transfer. Furthermore, the protrusion guides the first fluid to the rear of the heat transfer tubes. This prevents the development of a large dead fluid zone in the rear of the heat transfer tubes, resulting in an improvement of the heat transfer performance of the fin-tube heat exchanger.
Hereinbelow, one embodiment of the present invention is described with reference to the appended drawings.
The heat exchanger 1 is installed in such a position that the flow direction of the air A (X direction) is approximately perpendicular to the stacking direction of the fins 3 (Y direction) and the row direction of the heat transfer tubes 2 (Z direction). That said, the airflow direction may be slightly inclined from the X direction as long as a sufficient heat exchange amount can be ensured. It should be noted that, in the present specification, the stacking direction (Y direction) that is perpendicular to the principal surfaces of the fins 3 is defined as a height direction.
Each of the fins 3 has a rectangular, flat plate-like shape, and they are arranged along the Y direction shown in
Protrusions 5 in a regular square pyramidal shape are formed on the surface of the fin 3. The protrusions 5 protrude from one of the surfaces of the fin 3. The protrusions 5 are disposed between the respective heat transfer tubes 2 in each of the rows. In the present embodiment, the protrusions 5 are disposed at the midpoints between the adjacent heat transfer tubes 2 in a row direction. The area of the protrusions 5 viewed in the Y direction, that is, the area of the protrusions 5 in the plan view of
The width of each of the protrusions 5 along the Z direction increases from an upstream edge 8a thereof to an intermediate portion 8b thereof, and it decreases from the intermediate portion 8b to a downstream edge 8c thereof, along the flow direction of the air A. Each of the protrusions 5 had a first slanted surface 6a facing toward the top left of
In the present heat exchanger 1, the protrusions 5 are disposed at a relatively upstream side. Specifically, the upstream edges 8a of the protrusions 5 are located upstream of the centers C of the heat transfer tubes 2. The intermediate portions 8b of the protrusions 5 are located upstream of the downstream edges 2e of the heat transfer tubes 2. In other words, the upstream edges 8a of the protrusions 5 are located upstream of the line 9 connecting the centers C of the heat transfer tubes 2, and the intermediate portions 8b of the protrusions 5 are located upstream of the line 10 connecting the downstream edges 2e of the heat transfer tubes 2. The downstream edges 8c of the protrusions 5 are located downstream of the downstream edges 2e of the heat transfer tubes 2.
In the present embodiment, the height H of the protrusions 5 is greater than the fin pitch FP, as illustrated in
However, as shown in
Next, the flow of the air in the present heat exchanger 1 will be discussed.
As illustrated in
Next, airflow A3 that has flowed around to the rear of the first heat transfer tube 2A collides against a protrusion 5 in the second row, and it is guided toward a heat transfer tube 2C side in the second row by the second slanted surface 6b of the protrusion 5. Likewise, airflow A3′ that has flowed around to the rear of the second heat transfer tube 2B collides against a protrusion 5 in the second row, and it is guided toward a heat transfer tube 2C side in the second row by the first slanted surface 6a of the protrusion 5. Then, airflows A4 and A4′ guided by the slanted surfaces 6a and 6b flow around to the rear of the heat transfer tube 2C. As a result, in the rear of the heat transfer tube 2C of the fin 3 as well, the heat transfer coefficient is hindered from degrading, and the area of the dead fluid zone is reduced.
Table 1 shows simulation results in which the fin-tube heat exchanger according to the present embodiment (see
In evaluating the performance of a heat exchanger, it is more preferable that heat transfer coefficient α be greater, while it is more preferable that pressure loss ΔP be less. That is, it is more preferable that α/ΔP be greater. As seen from Table 1, the fin-tube heat exchanger of the present embodiment shows that the longer the airflow-wise length L of the protrusions 5, the greater the α/ΔP, while the higher the height H of the protrusions 5, the less the α/ΔP. In other words, the greater the parameter L/H is, the greater the α/ΔP.
As discussed above, in the fin-tube heat exchanger 1 according to the present embodiment, each of the fins 3 has the protrusions 5 in a quadrangular pyramidal shape between the heat transfer tubes 2A and 2B, and the protrusions 5 are formed so as to divide the air toward the one heat transfer tube 2A side and the other heat transfer tube 2B side. Specifically, each of the protrusions 5 has the first slanted surface 6a for guiding the air toward the one heat transfer tube 2A side and the second slanted surface 6b for guiding the air toward the other heat transfer tube 2B side. In addition, the upstream edge 8a of the protrusion 5 is located upstream of the centers C of the heat transfer tubes 2A and 2B. Thus, the air starts to be guided in a region upstream of the centers C of the heat transfer tubes 2A and 2B, so the flow directions change at a relatively early stage. As a result, the air tends to flow around to the rear of the heat transfer tubes 2A and 2B easily. Thus, according to the present embodiment, the dead fluid zone can be reduced.
Moreover, the intermediate portion 8b, which is the widest portion of the protrusion 5, is located upstream of the downstream edges 2e of the heat transfer tubes 2A and 2B. This also serves to allow the air to flow around to the rear of the heat transfer tubes 2A and 2B more easily, thus the dead fluid zone reduces.
Furthermore, in the present embodiment, after the air is divided by the protrusion 5 toward the one heat transfer tube 2A side and toward the other heat transfer tube 2B side, the flow of the air is accelerated in the spaces between the protrusion 5 and each of the heat transfer tubes 2A and 2B. Therefore, the heat transfer coefficient of the fin 3 improves corresponding to the acceleration of the flow of the air.
In addition, the accelerated air collides against a protrusion 5 provided at a more downstream side. As a result, the thermal boundary layer becomes thinner at the protrusion 5 in the downstream side. Accordingly, the heat transfer coefficient at the protrusions 5 of the downstream side improves, leading to an improvement in the heat transfer coefficient of the fin 3 as a whole.
In addition, the width of each of the protrusions 5 increases from the upstream edge 8a to the intermediate portion 8b, while it decreases from the intermediate portion 8b to the downstream edge 8c. Thus, the protrusions 5 are configured so that they do not narrow the flow passage of the air after the air is guided toward the heat transfer tube 2A and 2B sides by the portion from the upstream edge 8a to the intermediate portion 8b (the first slanted surface 6a and the second slanted surface 6b). Accordingly, by the protrusions 5 of the present embodiment, the pressure loss can be prevented from becoming too large.
In the present heat exchanger 1, the protrusions 5 are disposed in a relatively upstream side. Therefore, as illustrated in
In the present heat exchanger 1, the equivalent diameter d of the protrusions 5 is equal to or greater than the outer diameter D of the heat transfer tubes 2, which means that the protrusions 5 is formed to be relatively large. Therefore, the flow direction can be changed in a relatively large scale. Accordingly, it is possible to guide the air to the rear of the heat transfer tubes 2 desirably even when the flow velocity of the air is relatively small (for example, when the front velocity is less than 2 m/s) and even when it is particularly small (for example, when the front velocity is less than 1 m/s). The present heat exchanger 1 can exhibit good heat transfer characteristics even for the airflow in a laminar flow condition. Moreover, since the protrusions 5 are formed to be relatively large in this way, the air can be accelerated greatly locally between the protrusions 5 and the heat transfer tubes 2, so that the heat transfer coefficient can be improved.
From the viewpoint of making the protrusions 5 large, it is preferable that the occupied area of the protrusions 5 in the entire fin 3 (excluding the portion of cross-sectional area of the heat transfer tubes) be made large to a certain degree. For this reason, the occupied area of the protrusions 5 may be, for example, equal to or greater than the occupied area as in the above-described simulation model (30%) but less than the maximum possible value at which the protrusions 5 can be placed in between the heat transfer tubes 3 (for example, 75%). More desirably, when the occupied area is from 43% to 73%, as is shown in Table 1, it is appropriate because the α/ΔP value will be 1 or greater.
Furthermore, in the present embodiment, the protrusions 5 are formed in a quadrangular pyramidal shape, and therefore, the flow direction of the air can be changed relatively abruptly at the first slanted surface 6a and the second slanted surface 6b. As a result, it becomes possible to guide the air to the rear of the heat transfer tubes 2 more efficiently.
In addition, the surface area of the fin 3 is greater in the present embodiment by the area of the protrusions 5 than in the case in which the entire surface of the fin is flat. Thus, the amount of heat exchange can be increased because of the enlargement of the heat transfer area. The amount of the increased heat transfer area may be, but is not limited to, from 3% to 5%, for example.
When the present heat exchanger 1 is used as a condenser for cooling the air (for example, an evaporator in a refrigeration cycle apparatus), dew condensation may take place on the surfaces of the fins 3. Also, when the present heat exchanger 1 is installed in an outdoor unit in a cold area, frost formation may take place on the surfaces of the fins 3. However, in the present heat exchanger 1, the portion of the fin 3 other than the protrusions 5 is a flat surface. For this reason, water drops formed due to dew condensation or after defrosting tend not to stay on the surface of the fin 3 and tend to fall down more quickly in comparison with what is called a slit fin. Therefore, the present heat exchanger 1 can exhibit an excellent advantageous effect also as a condenser.
In the present embodiment, the protrusions 5 are configured to protrude from one surface of the fin 3. However, it is also possible that some of the protrusions 5 are configured to protrude from one surface of the fin 3 while the other protrusions 5 are configured to protrude from the other surface of the fin 3. For example, a plurality of protrusions 5 arranged in a row direction may be configured to protrude alternately from the obverse side and the reverse side of the fin 3.
The airflow-wise length of each protrusion 5 is not particularly limited. For example, when the airflow-wise length of the fins 3 is 36 mm, the length of the protrusions 5 may be set to be equal to or greater than 4.5 mm but less than 36 mm.
The shape of each of the protrusions 5 is not limited to a quadrangular pyramidal shape. The shape of the protrusion 5 may be other pyramidal shapes, such as a triangular pyramidal shape, as long as it is possible to obtain a significant effect shown in the present specification, such as the effect of guiding the air A toward the first heat transfer tube 2A and the second heat transfer tube 2B or the effect of hindering the dead fluid zone from developing.
In addition, a fin 43 as shown in
Furthermore, the protrusions having other shapes described in the following embodiments may be employed suitably likewise.
Embodiment 2As illustrated in
In the present embodiment as well, the width of each of the protrusions 15 increases from the upstream edge 8a to the intermediate portion 8b, while it decreases from the intermediate portion 8b to the downstream edge 8c. The upstream edges 8a of the protrusions 15 are located upstream of the centers C of the heat transfer tubes 2A and 2B. The intermediate portions 8b of the protrusions 15 are located upstream of the downstream edges 2e of the heat transfer tubes 2A and 2B. The diameter d of the protrusions 15 is equal to or greater than the diameter D of the heat transfer tubes 2.
The height of the protrusions 15 may be either greater or less than the fin pitch. The height of the protrusions 15 may be equal to the fin pitch.
The rest of the configurations are the same as those in Embodiment 1 and the description thereof will be omitted.
In the present embodiment as well, the area of the dead fluid zone at the rear of the heat transfer tubes 2 becomes smaller, as in Embodiment 1. As a result, the heat transfer characteristics can be improved. Moreover, according to the present embodiment, the air can be guided relatively gently toward the first heat transfer tube 2A side and toward the second heat transfer tube 2B side because the first slanted surface 6a and the second slanted surface 6b are curved surfaces.
Embodiment 3As illustrated in
In the present embodiment as well, the protrusion 25 has no clear ridge line. However, as in the case of Embodiment 2, assuming a virtual line 7a extending from an upstream edge 8a to an apex 11 in the X direction and a virtual line 7b extending through the apex 11 in the Z direction, it is understood that a first slanted surface 6a, which guides the air toward the first heat transfer tube 2A side, and a second slanted surface 6b, which guides the air toward the second heat transfer tube 2B side, are formed between the virtual line 7a and the virtual line 7b.
In the present embodiment as well, the width of each of the protrusions 25 increases from the upstream edge 8a to the intermediate portion 8b, while it decreases from the intermediate portion 8b to the downstream edge 8c. The upstream edges 8a of the protrusions 25 are located upstream of the centers C of the heat transfer tubes 2A and 2B. The intermediate portions 8b of the protrusions 25 are located upstream of the downstream edges 2e of the heat transfer tubes 2A and 2B. The equivalent diameter d of the protrusions 25 is equal to or greater than the diameter D of the heat transfer tubes 2. The height of the protrusions 25 may be either greater or less than the fin pitch, or may be equal to the fin pitch.
The rest of the configurations are the same as those in Embodiment 1 and the description thereof will be omitted.
In the present embodiment as well, the area of the dead fluid zone at the rear of the heat transfer tubes 2 becomes smaller and the heat transfer characteristics improve, as in Embodiment 1. Also, as in Embodiment 2, the air can be guided relatively gently toward the first heat transfer tube 2A side and the second heat transfer tube 2B side because the first slanted surface 6a and the second slanted surface 6b are curved surfaces. Furthermore, according to the present embodiment, the degree of guiding the air to the first heat transfer tubes 2A and the second heat transfer tubes 2B can be set as appropriate by changing the ellipticity of the protrusions 25 appropriately. Thus, by appropriately setting the ellipticity of the protrusions 25 according to the conditions of use of the heat exchanger 1, the heat transfer characteristics can be more finely adjusted or optimized.
Next, embodiments of the fins in which the protrusions are formed in a circular hump shape or in an elliptical hump shape will be discussed.
Embodiment 4In addition, as illustrated in
As has been described earlier, the heat transfer tubes 2 are disposed in a staggered manner in two rows, one of the two rows being the front row that is closer to the leading edge 30p of the fin 30 and the other row being the rear row that is parallel to the front row. Other protrusions 35 are formed between two adjacent heat transfer tubes 2, 2 disposed in the rear row, the other protrusions having the same shape and the same dimensions as those of the protrusions 35 that are formed between two adjacent heat transfer tubes 2, 2 disposed in the front row. Thereby, the effect of improving the heat transfer coefficient can be expected in the rear row as well as in the front row.
It is preferable that the location and orientation of the protrusions 35 be determined in the following manner. As illustrated in
In addition, the orientation of the protrusions 35, the outer shape 5s of which is in an elliptical shape, are determined so that the minor axis of the ellipse is parallel to the row direction (Z direction) in which the first heat transfer tubes 2A and the second heat transfer tubes 2B are arranged. In other words, the flow direction of the air A and the major axis of the ellipse are parallel to each other. In this way, the air A can be guided more smoothly to the left and right of the protrusions 35, and the degree of increase of the pressure loss originating from the formation of the protrusions 35 can be lessened. Of course, it is also possible to set the major axis of the ellipse to be along a direction parallel to the row direction.
In addition, each of the protrusions 35 is formed at a location equidistant from the center C1 of the first heat transfer tube 2A and the center C2 of the second heat transfer tube 2B. In other words, the location of the protrusion 35, relative to the first heat transfer tube 2A and the second heat transfer tube 2B, is determined so that the major axis of the image of the elliptical shape in a plane on which the protrusion 35 is orthogonally projected is contained in a virtual plane MD that perpendicularly bisects the line segment C1C2 connecting the center C1 of the first heat transfer tube 2A and the center C2 of the second heat transfer tube 2B at the shortest distance. This makes it possible to allow the air A to flow along both the flat region between the protrusion 35 and the first heat transfer tube 2A and the flat region between the protrusion 35 and the second heat transfer tube 2B uniformly. In other words, both the first heat transfer tube 2A and the second heat transfer tube 2B are allowed to contribute to heat transfer equally, and in this case, the heat transfer performance of the fin-tube heat exchanger 1 can be maximized.
As illustrated in
In addition, the height H of each of the protrusions 35 monotonously increases toward the apex TP1. The apex TP1 corresponds to the center of the ellipse when the protrusion 35 is viewed in plan. By employing such a shape, the air A is allowed to flow toward the apex TP1 smoothly, and therefore, an increase in pressure loss can be hindered.
There are several preferable examples of the surface shape of the protrusion 35. First, the cross-sectional view of the fin 30 shown in
It is also possible that the shape of the protrusion 35 may be adjusted so that the surface 5p thereof forms a sine curve represented by the equation Y=Kcos(X) {K: constant, −180°≦X≦180°}, as shown in
Another example of the curve that can make the bending seamless is a clothoid curve. It is possible to employ the clothoid curve for the surface shape of the protrusion 35. That is, the shape of the protrusion 35 may be adjusted so that the surface 5p thereof forms a clothoid curve in the XY cross section.
Generally, the way of bending of a curve is represented by a circle of curvature. A curve in which the way of bending does not leap but changes seamlessly from small to large or from large to small is best suited to the line for an expressway. One of the best examples of such a curve is “clothoid.” The radius r of the circle of curvature of a clothoid is inversely proportional to the travel distance (the distance s from the origin in
r=a2/s (a: constant) (1)
Although it has been described that the surface 5p may form a clothoid curve in the XY cross section, one single clothoid curve does not fit the surface 5p of the protrusions 35. For this reason, the shape of the protrusion 35 may be adjusted so that the ascending section of the surface 5p appearing in the XY cross section, which is from the upstream edge 5f to the apex TP1, is divided into a plurality of sections and each of the divided sections forms a clothoid curve. It is recommended that adjustment should be done so that the radius of the circle of curvature changes seamlessly at the boundaries of the sections. It is recommended that the descending section from the apex TP1 to the downstream edge 5e should be symmetrical to the ascending section. In this way, the entire surface 5p forms a clothoid curve in the XY cross section.
Alternatively, the shape of the protrusion 35 may be adjusted so that a portion of the surface 5p forms a clothoid curve while the rest of the surface forms another type of curve, such as a circular arc. For example, as illustrated in the XY cross section in
Of course, there is an advantage for the case in which the shape of the protrusion 35 is adjusted so that the curve formed by the surface 5p contains no inflection point between the upstream edge 5f and the apex TP1 in the XY cross section. Although excellent performance is obtained in the case in which an inflection point is contained (
It is desirable that the shape of the protrusion 35 in the cross section that contains the minor axis and is perpendicular to the principal surface of the fin 30, i.e., in the YZ cross section, be adjusted so that the surface 5p forms an easement curve, such as a sine curve or a clothoid curve. More preferably, the shape of the protrusion 35 should be adjusted so that the surface 5p forms an easement curve in an arbitrary cross section that contains the apex TP1 and is perpendicular to the principal surface of the fin 30. In this way, the effect of hindering a decrease in flow velocity can be maximized, and at the same time, the air A that has reached the protrusions 35 can be guided more smoothly toward the heat transfer tubes 2.
Thus, the shape of the protrusion 35 may be adjusted so that the surface 5p forms a curve containing an inflection point between the upstream edge 5f and the apex TP1 in a cross section that is perpendicular to the principal surface of the fin 30 and contains the minor axis or the major axis of the ellipse. When such a configuration is employed, the effect of hindering a decrease in the flow velocity at the protrusions 35 can be expected. It is also possible to adjust the shape of the protrusion 35 so that the surface 5p forms a curve containing an inflection point in an arbitrary cross section that is perpendicular to the principal surface of the fin 30 and contains the apex TP1.
On the other hand, when the surface 5p is configured to form a curve containing no inflection point, production of the fin 30 is easy. That is, it is also possible to adjust the shape of the protrusion 35 so that the surface 5p forms a curve containing no inflection point in an arbitrary cross section that contains the apex TP1 and is perpendicular to the principal surface of the fin 30.
Next, the workings of the fin-tube heat exchanger 1 according to the present embodiment will be described below.
As illustrated in
On the other hand, a fin 203 in which two protrusions 205a and 205b having an elliptical hump shape are formed between a first heat transfer tube 2A and a second heat transfer tube 2B, as illustrated in
However, because the airflow AF3 between the protrusion 205a and the protrusion 205b is relatively away from the heat transfer tubes 2A and 2B, the airflow AF3 does not contribute to improvements in the heat transfer performance as much as the flows AF1 and AF2 that are closer to the heat transfer tubes 2A and 2B. If this is the case, it is believed more effective to form a large protrusion 35 as in the present invention than to form two protrusions 205a and 205b.
Embodiment 5A fin 31 shown in the plan view of
As illustrated in
The protrusion 51 in a circular hump shape is free from the issue of orientation, unlike the protrusion 35 in an elliptical hump shape (
The height and the surface shape of the protrusion 51 are also the same as in the case of the protrusion 35 described in Embodiment 4. For example, the shape of the protrusion 51 may be adjusted so that the surface 51p forms an easement curve, such as a sine curve (see
In Embodiments 4 and 5 as well, when assuming a virtual line extending in the X direction from the upstream edge 5f, 51f of the protrusion 35, 51 and a virtual line extending in the Z direction through the apex TP1, TP2 of the protrusions 35, 51, a first slanted surface that guides the air toward the first heat transfer tube 2A and a second slanted surface that guides the air toward the second heat transfer tube 2B are formed between the two virtual lines, as in Embodiment 1.
As illustrated in
A fin 32 shown in the plan view of
In the fin 30 according to Embodiment 4 (see
In addition, a fin 33 as illustrated in
The protrusions 35, 51, and 53 described in Embodiments 4 to 6 are formed so that all the protrusions protrude in the same direction. However, as has been mentioned in Embodiment 1, this is not essential. Specifically, a fin 34 as illustrated in
When the protrusions 35, 35′ with different protruding directions are formed to coexist as described above, the following effects are achieved. A fin in which all the protrusions protrude in the same direction is produced through the following steps: the step of cutting a metal plate into a predetermined size, the step of forming through holes for accommodating the heat transfer tubes, and the step of forming the protrusions in the metal plate by a pressing process. When the protruding direction of the protrusions is limited to one direction, the metal plate warps during the step of forming the protrusions, resulting in warpage in the fin obtained. If such warpage occurs, there may be cases in which, when assembling the heat exchanger, the fin pitch becomes non-uniform or the heat transfer tubes cannot be inserted smoothly in the through holes because of misalignment of the through holes.
In contrast, when producing the fin 34 in which the protrusions 35, 35′ with different protruding directions are formed, a metal plate that forms the fin 34 is pressed from both sides. Since the pressing is conducted from both sides, the warpage can be balanced between the obverse side and the reverse side, and the warpage can be prevented.
Regarding the dimensions and locations, the protrusions 35, 35′ are made in the same manner as described in Embodiment 4, except that the protruding directions are made different. In addition, it is preferable that the numbers of the protrusions 35, 35′ be the same and that they be formed alternately along the row direction. In this case, a high warpage prevention effect can be obtained. Of course, such a configuration may be combined with any other embodiments.
Further, a fin 36 shown in
The above-described embodiments 1 through 7 may be combined freely as long as such combinations do not depart from the scope of the present invention. For example, the second protrusions 53 described in
The fin-tube heat exchanger 1 described above may be applied to a heat pump apparatus for heating or cooling an object such as air or water. As illustrated in
The above-described heat pump apparatus 70 may be applied to an air conditioner 80 or a hot water heater 90, as illustrated in
As illustrated in
Characteristics of fin-tube heat exchangers employing the fin shown in
Fin size: 16.94 mm (air flow direction)×7.65 mm (row direction)
Fin thickness: 0.1 mm
Fin pitch: 1.06 mm
Outer diameter of the heat transfer tube: 5.0 mm
Inner diameter of the heat transfer tube: 4.0 mm
Front velocity Vair: 1 m/sec.
Conditions of Example 1Shape of the protrusion: Circular hump with a cosine curve (−90°≦X≦90°)
Diameter of the protrusion: 6.0 mm
Height of the protrusion: 1.0 mm
Conditions of Example 2Shape of protrusion: Circular hump with a cosine curve (−180°≦X≦180°)
Diameter of the protrusion: 6.0 mm
Height of the protrusion: 1.0 mm
Conditions of Example 3Shape of the protrusion: Circular hump with a clothoid curve
Diameter of the protrusion: 6.0 mm
Height of the protrusion: 1.0 mm
Conditions of Comparative Example 1Shape: Corrugated
Level difference between the ridge and the valley: 1.0 mm
The computer simulation results for Examples 1 through 3 and Comparative Example 1 are shown in
First, as will be appreciated from
In addition, as will be appreciated from
The flow velocity distribution shown in each view B is represented by the values at midpoints between a fin and another fin. When the fin pitches are equal, no significant difference in flow velocity distribution is seen between the corrugated fin and the fins according to the present invention. However, primary factors responsible for the improvement in heat transfer performance are that the boundary layer along the fin surface is thin and that the flow velocity around the heat transfer tubes is great. These two factors are seen from the Nusselt number distribution.
Thus, the heat exchanger according to the present invention makes it possible to reduce the thickness of the boundary layer over the surfaces of the protrusions and to increase the flow velocity in a region between the protrusion and the heat transfer tube. Thereby, the heat exchanger according to the present invention achieves a superior heat transfer coefficient to the heat exchanger using a corrugated fin. Moreover, as shown in Table 2, each of the heat exchangers of Examples 1 to 3 shows a less pressure loss than the conventional heat exchanger using a corrugated fin.
Next, similar computer simulations were conducted for a heat exchanger employing the fin shown in
Fin size: 27.0 mm (air flow direction)×10.5 mm (row direction)
Fin thickness: 0.1 mm
Fin pitch: 1.49 mm
Outer diameter of the heat transfer tube: 7.0 mm
Inner diameter of the heat transfer tube: 5.8 mm
Front velocity Vair: 1 m/sec.
Conditions of Example 4Shape of the protrusion: Elliptical hump with a cosine curve (−90°≦X≦90°)
Orientation of the protrusion: The major axis is parallel to the air flow direction
Major axis of the protrusion: 13.0 mm
Minor axis of the protrusion: 10.0 mm
Height of the protrusion: 0.765 mm
Conditions of Example 5Shape of the first protrusion: Circular hump with a cosine curve (−90°≦X≦90°)
Diameter of the first protrusion: 10 mm
Height of the first protrusion: 0.765 mm
Shape of the second protrusion: Circular hump with a cosine curve (−90°≦X≦90°)
Diameter of the second protrusion: 5.7 mm
Height of the second protrusion: 0.765 mm
Conditions of Comparative Example 2Shape: Corrugated
Level difference between the ridge and the valley: 1.49 mm
The computer simulation results for Examples 4 and 5 as well as Comparative Example 2 are shown in
As will be appreciated from
On the other hand, as will be appreciated from
Claims
1. A fin-tube heat exchanger for exchanging heat between a first fluid and a second fluid, comprising:
- a plurality of fins arranged spaced apart from and parallel to each other so as to form a space or spaces for allowing the first fluid to flow therethrough; and
- a plurality of heat transfer tubes penetrating said plurality of fins, for allowing the second fluid to flow therethrough, wherein:
- said plurality of heat transfer tubes include a first heat transfer tube and a second heat transfer tube arranged in a predetermined row direction that intersects with a flow direction of the first fluid;
- said first heat transfer tube and said second heat transfer tube are adjacent to each other with respect to the row direction;
- each of said fins has a protrusion formed between said first heat transfer tube and said second heat transfer tube, said protrusion guiding the first fluid to said first heat transfer tube side and said second heat transfer tube side;
- the equivalent diameter of said protrusion, as viewed in an axis direction of said heat transfer tubes, is equal to or greater than the outer diameter of said heat transfer tubes;
- only one said protrusion is formed between said first heat transfer tube and said second heat transfer tube; and
- said upstream edge of said protrusion is located upstream of centers of said first and second heat transfer tubes with respect to the flow direction of the first fluid.
2. The fin-tube heat exchanger according to claim 1, wherein:
- the width of said protrusion along the row direction increases from an upstream edge of said protrusion to an intermediate portion thereof but decreases from said intermediate portion to a downstream edge thereof, along the flow direction of the first fluid;
- a first slanted surface slanted toward said first heat transfer tube side so as to guide the first fluid toward said first heat transfer tube side, and a second slanted surface slanted toward said second heat transfer tube side so as to guide the first fluid toward said second heat transfer tube side, are formed between said upstream edge and said intermediate portion of said protrusion;
- and
- said intermediate portion of said protrusion is located upstream of downstream edges of said first and second heat transfer tubes.
3. The fin-tube heat exchanger according to claim 1, wherein said heat transfer tubes and said protrusion are arrayed in a staggered manner, when viewed in an axis direction of said heat transfer tubes.
4. The fin-tube heat exchanger according to claim 1, wherein said protrusion is formed in a pyramidal shape.
5. The fin-tube heat exchanger according to claim 4, wherein said protrusion is formed in a quadrangular pyramidal shape.
6. The fin-tube heat exchanger according to claim 1, wherein said protrusion is formed in a circular conic shape or an elliptic conic shape.
7. The fin-tube heat exchanger according to claim 1, wherein said protrusion is formed in a circular hump shape or an elliptical hump shape.
8. The fin-tube heat exchanger according to claim 1, wherein the ratio L/H is greater than 5.5, where L is the length of said protrusion with respect to the flow direction of the first fluid and H is the protruding height of said protrusion.
9. The fin-tube heat exchanger according to claim 1, wherein the occupied area of said protrusion in each of said fins is from 43% to 73%.
10. The fin-tube heat exchanger according to claim 1, wherein:
- said protrusion is such that, when said protrusion is orthogonally projected onto a plane parallel to said plurality of fins, an image of said protrusion appearing on the plane shows a circular shape or an elliptical shape; and
- the area of the image of said protrusion appearing on the plane is greater than the cross-sectional area of each of said heat transfer tubes.
11. (canceled)
12. The fin-tube heat exchanger according to claim 10, wherein said upstream edge of said protrusion is located, with respect to the flow direction of the first fluid, closer to leading edges of said plurality of fins than upstream edges of said first heat transfer tube and said second heat transfer tube.
13. The fin-tube heat exchanger according to claim 10, wherein said protrusion is such that the image thereof appearing on the plane is in an elliptical shape, and that the orientation of said protrusion is determined such that the minor axis of the ellipse is parallel to the row direction in which said first heat transfer tube and said second heat transfer tube are arranged.
14. The fin-tube heat exchanger according to claim 13, wherein said protrusion is such that the location thereof relative to said first heat transfer tube and said second heat transfer tube is determined so that the major axis of the ellipse is contained in a virtual plane that perpendicularly bisects a line segment connecting the center of said first heat transfer tube and the center of said second heat transfer tube at the shortest distance.
15. The fin-tube heat exchanger according to claim 13, wherein the shape of said protrusion is adjusted so that its surface forms a curve in a cross section that contains the minor axis or the major axis of the ellipse and is perpendicular to principal surfaces of said plurality of fins.
16. The fin-tube heat exchanger according to claim 15, wherein said curve contains an inflection point between an upstream edge and an apex of said protrusion.
17. The fin-tube heat exchanger according to claim 15, wherein said curve contains no inflection point between an upstream edge and an apex of said protrusion.
18. The fin-tube heat exchanger according to claim 13, wherein the shape of said protrusion is adjusted so that its surface forms a sine curve in a cross section that contains the minor axis or the major axis of the ellipse and is perpendicular to principal surfaces of said plurality of fins.
19. The fin-tube heat exchanger according to claim 18, wherein said surface follows a sine curve represented by the equation Y=Kcos(X) {K: constant, −180°≦X≦180°}.
20. The fin-tube heat exchanger according to claim 18, wherein said surface follows a sine curve represented by the equation Y=Kcos(X) {K: constant, −90°≦X≦90°}.
21. The fin-tube heat exchanger according to claim 10, wherein the shape of said protrusion is adjusted so that its surface forms a clothoid curve in a cross section that is parallel to the flow direction of the first fluid and is perpendicular to principal surfaces of said plurality of fins.
22. The fin-tube heat exchanger according to claim 1, wherein the height of said protrusion is adjusted so as to satisfy the expression (FP/4)≦H≦FP, where H is the height of said protrusion and FP is the fin pitch, which is a parallel gap distance between said plurality of fins.
23. The fin-tube heat exchanger according to claim 10, wherein the shape of said protrusion is adjusted so that the image thereof appearing on the plane shows a circular shape and that its surface forms a curve in a cross section that is perpendicular to principal surfaces of said plurality of fins.
24. The fin-tube heat exchanger according to claim 23, wherein said curve contains an inflection point between said upstream edge and an apex of said protrusion.
25. The fin-tube heat exchanger according to claim 23, wherein said curve contains no inflection point between an upstream edge and an apex of said protrusion.
26. The fin-tube heat exchanger according to claim 10, wherein the shape of said protrusion is adjusted so that the image thereof appearing on the plane shows a circular shape and that its surface forms a sine curve in a cross section that is perpendicular to principal surfaces of said plurality of fins.
27. The fin-tube heat exchanger according to claim 26, wherein said surface follows a sine curve represented by the equation Y=Kcos(X) {K: constant, −180°≦X≦180°}.
28. The fin-tube heat exchanger according to claim 26, wherein said surface follows a sine curve represented by the equation Y=Kcos(X) {K: constant, −90°≦X≦90°}.
29. The fin-tube heat exchanger according to claim 1, wherein:
- said heat transfer tubes are disposed in a staggered manner in two rows, one of the two rows being a front row that is closer to leading edges of said plurality of fins and the other row being a rear row that is parallel to the front row; and
- another protrusion is formed between two adjacent ones of said heat transfer tubes disposed in the rear row, said other protrusion having the same shape and the same dimensions as those of said protrusion that is formed between two adjacent ones of said heat transfer tubes disposed in the front row.
30. The fin-tube heat exchanger according to claim 29, wherein a second protrusion is formed between said protrusion formed in the front row and said other protrusion formed in the rear row, said second protrusion having a surface area smaller than that of said protrusion and said other protrusion.
31. A fin used for the fin-tube heat exchanger according to claim 1.
32. A heat pump apparatus comprising:
- a compressor for compressing a refrigerant;
- a radiator for cooling the refrigerant compressed by said compressor;
- an expansion mechanism for expanding the refrigerant cooled by said radiator; and
- an evaporator for evaporating the refrigerant expanded by said expansion mechanism, wherein
- at least one of said evaporator and said radiator comprises the fin-tube heat exchanger according to claim 1.
33. A heat pump apparatus comprising:
- a compressor for compressing a refrigerant;
- a radiator for cooling the refrigerant compressed by said compressor;
- an expansion mechanism for expanding the refrigerant cooled by said radiator; and
- an evaporator for evaporating the refrigerant expanded by said expansion mechanism, wherein at least said evaporator comprises the fin-tube heat exchanger according to claim 1.
Type: Application
Filed: Mar 14, 2007
Publication Date: Aug 13, 2009
Applicant: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD. (Kadoma-shi, Osaka)
Inventors: Osamu Ogawa (Kyoto), Kou Komori (Nara)
Application Number: 12/294,015
International Classification: F25B 13/00 (20060101); F28D 7/00 (20060101); F28F 1/24 (20060101);