Patent Application
20180100659
The present invention relates to a heat exchanger that is to be used in air-conditioning apparatuses such as a room air-conditioning apparatus and a package air-conditioning apparatus, and to an air-conditioning apparatus including the heat exchanger.
There has been the following problem in a related-art corrugated-fin heat exchanger mounted to an outdoor unit of an air-conditioning apparatus. During a heating operation, heat of air flowing through air passages is removed by flat tubes through corrugated fins, so that water vapor in the air is brought into a supersaturated state. When surface temperatures of the flat tubes and the corrugated fins are 0 degrees Celsius or less, the supersaturated water vapor turns into ice, and frost is formed on surfaces of the flat tubes and the corrugated fins. When the frost formation proceeds, spaces formed by each fin are closed, with the result that airflow resistance increases to degrade heating performance.
To solve this problem, there has been proposed a corrugated-fin heat exchanger in which the corrugated fins partially protrude to a windward side with respect to windward-side end portions of the flat tubes (see, for example, Patent Literature 1).
In the corrugated-fin heat exchanger disclosed in Patent Literature 1, the protruding portions of the corrugated fins, which protrude to the windward side with respect to the windward-side end portions of the flat tubes, have a large heat-transfer distance from the flat tubes. Consequently, the fin efficiency (thermal conductivity in the fins) is lowered, so that the surface temperature of the corrugated fins is less likely to be lowered. Thus, the amount of formed frost is reduced, thereby being capable of preventing the spaces formed by each fin from being closed.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 6-147785
In the related-art corrugated-fin heat exchanger as disclosed in Patent Literature 1, when lug portions formed in an airflow orthogonal direction are provided on the protruding portions of the corrugated fins to promote heat transfer (promote heat transfer between the fins and air), the fin efficiency is further lowered, thereby preventing frost formation on the lug portions.
However, there has been a problem in that, in a case where frost is once formed on the protruding portions or the lug portions of the corrugated fins, when the frost is melted by refrigerant heat during a defrosting operation, heat is less likely to be transferred from the flat tubes to the frost through the corrugated fins, with the result that the defrosting performance is degraded.
The present invention has been made to solve the above-mentioned problem and has an object to provide a heat exchanger and an air-conditioning apparatus that are capable of preventing degradation of defrosting performance while promoting heat transfer.
According to one embodiment of the present invention, there is provided a heat exchanger, including a plurality of flat tubes arranged in a right-and-left direction orthogonal to a front-and-back direction, the front-and-back direction being an airflow direction of the heat exchanger, a corrugated fin sandwiched by adjacent ones of the plurality of flat tubes and thermally connected to the adjacent ones of the plurality of flat tubes at each of apexes of the corrugated fin, an inlet header connected to one end of each of the plurality of flat tubes, and an outlet header connected to the other end of each of the plurality of flat tubes, the plurality of flat tubes extending along an up-and-down direction of the heat exchanger, the corrugated fin including a protruding portion protruding to a front side with respect to a front-side end portion of each of the plurality of flat tubes, the protruding portion including a first lug portion oriented obliquely to the front-and-back direction, the corrugated fin further including a second lug portion formed in the right-and-left direction at a part sandwiched by the adjacent ones of the plurality of flat tubes.
In the heat exchanger of one embodiment of the present invention, the corrugated fin includes the protruding portion protruding to the front side with respect to the front-side end portion of each of the flat tubes. The protruding portion includes the (first) lug portion to promote heat transfer. The lug portion is oriented obliquely to the front-and-back direction that is the airflow direction. Consequently, a heat transfer passage is less likely to be divided by the lug portion during a defrosting operation as compared to a case where the lug portion is formed in the airflow orthogonal direction. As a result, heat can sufficiently be transferred to the protruding portion and the lug portion of the corrugated fin, thereby being capable of preventing the degradation of the defrosting performance.
Embodiments of the present invention are described below with reference to the drawings. The present invention is not limited to Embodiments described below. Moreover, in the drawings referred to below, the size relationship of components may be different from the actual size relationship in some cases.
As illustrated in
The corrugated fins 2 are each a metal thin plate shaped to have peaks and troughs that are apexes 2a alternately as viewed from one side. The peaks of the corrugated fin 2 are joined to a surface of one flat tube 1 of the two flat tubes 1 adjacent in the airflow orthogonal direction (right-and-left direction), and the troughs of the corrugated fin 2 are joined to a surface of the other flat tube 1. The peaks and the troughs of the corrugated fin 2 have a shape extending in the airflow direction (front-and-back direction). Consequently, joined portions between the corrugated fin 2 and the flat tube 1 each have a linear shape being continuous in the airflow direction (front-and-back direction). The joined portions each have a width enough for the joining. Further, when the peaks and the troughs have flat surfaces, and the flat surfaces are joined to the flat tubes 1, the joined portions between the corrugated fins 2 and the flat tubes 1 each have a wide linear shape.
As illustrated in
The first lug portions 7 are formed in the protruding portion 5 in a radial direction extending from the flat tubes 1 toward a center portion of a windward-side end portion (front-side end portion) of the protruding portion 5. Those first lug portions 7 formed to be inclined (oblique) to the airflow direction (front-and-back direction) are provided such that the two first lug portions 7 are arranged in a bilaterally symmetrical manner. As illustrated in
Further, on a part of the corrugated fin 2 other than the protruding portion 5, that is, the part sandwiched by the adjacent flat tubes 1, there are provided second lug portions 6 formed in the airflow orthogonal direction (right-and-left direction), and the five second lug portions 6 are formed to be arrayed in the airflow direction (front-and-back direction).
As illustrated in
As the outdoor unit in which the corrugated-fin heat exchanger 10 is mounted, a side-flow type illustrated in
In the outdoor unit of the side-flow type, as illustrated in
Further, in the outdoor unit of the top-flow type, as illustrated in
Next, an operation of the corrugated-fin heat exchanger 10 according to Embodiment 1 is described.
As illustrated in
Next, the flow of the refrigerant is described.
During a heating operation, refrigerant that is returned after exchanging heat with air in the indoor unit to transfer heat to be liquefied and then being decompressed into a low-temperature and low-pressure two-phase gas-liquid state flows into the corrugated-fin heat exchanger 10 serving as an evaporator, which is mounted to the outdoor unit, through the inlet header 3. Then, the refrigerant flows through the flat tubes 1, exchanges heat with air flowing through the heat-exchanger air passages to receive heat to be evaporated, then flows out through the outlet header 4, and flows into the indoor unit again. In this manner, the refrigerant circulates in the refrigeration circuit.
During the heating operation, the heat of the air flowing through the heat-exchanger air passages is removed by the flat tubes 1 through the corrugated fins 2, and water vapor in the air is brought into a supersaturated state. Then, the supersaturated water vapor is condensed on surfaces of the flat tubes 1 and the corrugated fins 2 to turn into water. Part of this water flows along the surfaces of the flat tubes 1, and part of this water flows through the slits formed in the protruding surface of the corrugated fin 2, to be drained to a lower part of the corrugated-fin heat exchanger 10. In this case, when the amount of condensed dew is large, or the drainage performance is poor, water stagnates in spaces formed by the fin of the corrugated fin 2, so that the heat-exchanger air passages are closed. As a result, the performance of the corrugated-fin heat exchanger 10 is degraded, thereby leading to degradation of heating performance. To solve this problem, in the corrugated-fin heat exchanger 10 according to Embodiment 1, the first lug portions 7 are formed in the radial direction extending from the flat tubes 1 toward the center of the windward-side end portion (front-side end portion) of the protruding portion 5.
As illustrated in
Further, when the surface temperatures of the flat tubes 1 and the corrugated fins 2 are 0 degrees Celsius or less, supersaturated water vapor turns into ice, so that frost is formed on the surfaces. In particular, the effect of promoting the heat transfer is significant at the lug portions, and hence the amount of formed frost is large at the lug portions.
Next, when the performance of the corrugated-fin heat exchanger 10 is degraded due to closure of the heat-exchanger air passages caused by frost formation in the corrugated-fin heat exchanger 10 or due to other factors, and the heating performance is degraded, a defrosting operation is started.
During the defrosting operation, normally, the fan 31 is stopped and the refrigeration cycle is switched to a cooling operation, or other measures are taken so that high-temperature refrigerant is caused to flow into the corrugated-fin heat exchanger 10. In this manner, the frost adhering to each of the surfaces of the flat tubes 1 and the corrugated fins 2 is melted. Then, the melted frost turns into water and flows along the surfaces of the flat tubes 1. Further, the water flows through the slits, which are formed in the protruding surface of the corrugated fin 2 in the course of forming the first lug portions 7, to thereby be drained to the lower part of the corrugated-fin heat exchanger 10. After the defrosting is completed, the heating operation is started again.
In this case, when the lug portions are formed in the corrugated fins 2, the lug portions, specifically, the slits formed in the course of forming the lug portions divide heat transfer passages from a leeward side (back side) that is a side at the position of the flat tube 1, through which the refrigerant flows, to the windward side (front side), with the result that the fin efficiency (thermal conductivity in the fins) is lowered. As a result, during the defrosting operation, heat from the refrigerant cannot sufficiently be transferred to the windward-side end portion (front-side end portion) of the protruding portion 5 and the lug portions, with the result that a time period required for the defrosting is prolonged. Meanwhile, when the heat-exchanger air passages are closed due to the frost formation, the heating performance is degraded.
To solve this problem, in the corrugated-fin heat exchanger 10 according to Embodiment 1, the first lug portions 7 are formed in the protruding portion 5 in the radial direction extending from the flat tubes 1 toward the center portion of the windward-side end portion (front-side end portion) of the protruding portion 5. Consequently, the heat transfer passages are less likely to be divided by the lug portions as compared to the case where the lug portions are formed in the airflow orthogonal direction (right-and-left direction). As a result, during the defrosting operation, heat can sufficiently be transferred to the windward-side end portion (front-side end portion) of the protruding portion 5 and the first lug portions 7, thereby being capable of preventing the degradation of the defrosting performance. That is, the time period required for the defrosting can be prevented from being prolonged.
Further, an interval is secured between the right and left first lug portions 7. Thus, even when frost is formed on the first lug portions 7 during the defrosting operation, the heat-exchanger air passages can be secured, thereby being capable of preventing the degradation of the heating performance.
In the corrugated-fin heat exchanger 10 of Embodiment 1, it is unnecessary to take a measure of, for example, increasing pitches of the corrugated fins 2 (interval between the adjacent apexes 2a) by sacrificing the performance during the normal operation, to achieve the above-mentioned effect.
In Embodiment 1, the number of the first lug portions 7 is two. However, the number of the first lug portions 7 is not limited to two, and the number of the first lug portions 7 may be one. Further, as illustrated in
As illustrated in
In the first modification example, the heat transfer performance is degraded as compared to the louver type illustrated in
Further, as illustrated in
In the second modification example, the heat transfer performance is degraded as compared to the louver type illustrated in
Further, as illustrated in
As compared to the first lug portions 7b illustrated in
Further, as illustrated in
The first lug portions 7d illustrated in
Further, the slits of the first lug portions 7d are small, and hence the heat transfer passages are less likely to be divided. As a result, heat can sufficiently be transferred to the windward-side end portion (front-side end portion) of the protruding portion 5 and the first lug portions 7d during the defrosting operation, thereby being capable of preventing the degradation of the defrosting performance. That is, the time period required for the defrosting can be prevented from being prolonged.
The corrugated fins 2 are each sandwiched by the adjacent flat tubes 1 and thermally connected to the flat tubes 1 at each apex 2a.
As illustrated in
In the corrugated fins 2, the intervals formed by the fin are smaller on the inner peripheral side at the vicinity of each apex 2a. However, as illustrated in
As described above, in the corrugated-fin heat exchanger 10 of Embodiment 1, the two first lug portions 7 are formed in the protruding portion 5 on the right and left sides to promote heat transfer. Further, the first lug portions 7 are formed in the radial direction extending from the flat tubes 1 toward the center portion of the windward-side end portion (front-side end portion) of the protruding portion 5. That is, the first lug portions 7 are oriented obliquely to the airflow direction (front-and-back direction). With this configuration, as compared to a case where the lug portions are formed in the airflow orthogonal direction (right-and-left direction), water is easily drained with the action of guiding air to the flat tubes 1 serving as the drainage passages, and further, the heat transfer passages are less likely to be divided by the lug portions. As a result, the drainage performance is enhanced during the heating operation. Further, during the defrosting operation, heat can sufficiently be transferred to the windward-side end portion (front-side end portion) of the protruding portion 5 and the first lug portions 7, thereby being capable of preventing the degradation of the defrosting performance. That is, the time period required for the defrosting can be prevented from being prolonged.
Further, an interval is secured between the right and left first lug portions 7. Thus, even when dew condensation or frost formation occurs on the first lug portions 7 during the defrosting operation, the heat-exchanger air passages can be secured, thereby being capable of preventing the degradation of the heating performance.
As basic configurations of the flat tubes 1 and the corrugated fins 2 of the corrugated-fin heat exchanger 10 according to Embodiment 1, there are provided the flat tubes 1 serving as the drainage passages extending in the up-and-down direction and the meandering corrugated fins 2 each sandwiched by the adjacent flat tubes 1 and thermally joined to the flat tubes 1. In
Effects similar to those described above can be obtained also in an air-conditioning apparatus including the corrugated-fin heat exchanger 10 according to Embodiment 1.
Embodiment 2 of the present invention is described below. Description of the same components as those of Embodiment 1 is omitted or partly omitted. The parts same as or corresponding to those of Embodiment 1 are denoted by the same reference signs.
As illustrated in
As illustrated in
In the protruding portion 5, the two first lug portions 7 that are formed to be inclined (oblique) to the airflow direction (front-and-back direction) are provided on the right and left sides. The first lug portions 7 are oriented obliquely in the same direction with respect to the airflow direction (front-and-back direction).
Further, on the part of the corrugated fin 2 other than the protruding portion 5, that is, the part sandwiched by the adjacent flat tubes 1, there are provided the second lug portions 6 formed in the airflow orthogonal direction (right-and-left direction), and the five second lug portions 6 are formed to be arrayed in the airflow direction (front-and-back direction).
As illustrated in
Next, an operation of the corrugated-fin heat exchanger 20 according to Embodiment 2 is described.
As illustrated in
Next, the flow of the refrigerant is described.
During the heating operation, refrigerant that is returned after exchanging heat with air in the indoor unit to transfer heat to be liquefied and then being decompressed into a low-temperature and low-pressure two-phase gas-liquid state flows into the corrugated-fin heat exchanger 20 serving as an evaporator, which is mounted to the outdoor unit, through the inlet header 3. Then, the refrigerant flows through the flat tubes 1 on the windward side (front side), flows through the flat tubes 1 on the leeward side (back side) through the intermediate header 11, exchanges heat with air flowing through the heat-exchanger air passages to receive heat to be evaporated, then flows out through the outlet header 4, and flows into the indoor unit again. In this manner, the refrigerant circulates in the refrigeration circuit.
Other operations are similar to those in Embodiment 1, and hence description of the operations is omitted.
The amount of formed frost is small at a portion on the corrugated fin 2 at which the airflow velocity is low in the airflow velocity distribution, and the amount of formed frost is large at a portion on the corrugated fin 2 at which the airflow velocity is high in the airflow velocity distribution. As illustrated in
As illustrated in
The frost on the frost formation portion 40 illustrated in
As described above, in Embodiment 2, the flat tubes 1 are provided in two rows in the airflow direction (front-and-back direction). Consequently, in addition to the passage for water flowing through the slits and the passage for water flowing along the flat tube 1, there is formed the passage for water flowing through the part between the flat tube 1 on the windward side (front side) and the flat tube 1 on the leeward side (back side). Consequently, not only water flows along the flat tube 1 to be drained due to the gravity when the flat tubes 1 are provided in only one row, but also the water is sucked by a capillary force of a gap formed between the flat tube 1 on the windward side (front side) and the flat tube 1 on the leeward side (back side), so that the water is easily drained to the lower part of the corrugated-fin heat exchanger 10, thereby enhancing the drainage performance. Further, when air is caused to flow after the defrosting, the drainage performance can further be enhanced with the above-mentioned air guiding action. The enhancement of the drainage performance with the air guiding action exerts the effect to promote drainage of water to the flat tubes 1 not only during the defrosting operation but also during the normal heating operation even in a case where dew condensation occurs on the surfaces of the flat tubes 1 or the corrugated fins 2.
When the two first lug portions 7 that are oriented obliquely in the same direction with respect to the airflow direction (front-and-back direction) are formed on the right and left sides on the protruding portion 5 of the corrugated fin 2, one first lug portion 7 is not formed at a position in the radial direction extending from the flat tubes 1, and hence the defrosting performance is degraded as compared to Embodiment 1. However, in the protruding portion 5 of the corrugated fin 2, in which the first lug portions 7 are formed, the amount of formed frost is relatively small, and hence the influence of the degradation of the defrosting performance is small. Further, the air guiding action is promoted as compared to Embodiment 1, and an effect of being capable of prolonging a time period until the defrosting operation is performed is more significant.
As illustrated in
The case where the thickness of the corrugated fin 2 is varied only at the windward-side end portion (front-side end portion) of the protruding portion 5 as described above is most efficient. However, the thickness of the corrugated fin 2 may be entirely varied in the same manner in the airflow direction (front-and-back direction). In this case, also when frost is formed on a part of the corrugated fin 2 on the leeward side (back side), the defrosting performance can be enhanced.
As described above, in the corrugated-fin heat exchanger 20 of Embodiment 2, the two first lug portions 7 are formed in the protruding portion 5 on the right and left sides to promote heat transfer. The first lug portions 7 are oriented obliquely in the same direction with respect to the airflow direction (front-and-back direction). Thus, the air guiding action is promoted as compared to Embodiment 1, thereby being capable of prolonging the time period until the defrosting operation is performed.
Further, the flat tubes 1 are provided in two rows in the airflow direction (front-and-back direction). Thus, in addition to the passage for water flowing through the slits, the passage for water flowing through the part between the flat tube 1 on the windward side (front side) and the flat tube 1 on the leeward side (back side) is formed. Consequently, as compared to the case where the flat tubes 1 are provided in only one row, water is easily drained to the lower part of the corrugated-fin heat exchanger 10, thereby enhancing the drainage performance. Further, when air is caused to flow after the defrosting, the drainage performance can be further enhanced with the above-mentioned air guiding action.
Further, the thickness of the center portion of the corrugated fin 2 in the airflow orthogonal direction (right-and-left direction) is formed larger than those of other portions (both right and left end portions), and hence, during the defrosting operation, the fin efficiency can be enhanced substantially equally to that in the case where the entire thickness of the fin is increased. Consequently, heat can sufficiently be transferred to the windward-side end portion (front-side end portion) of the protruding portion 5 and the first lug portions 7, thereby being capable of preventing the degradation of the defrosting performance. That is, the time period required for the defrosting can be prevented from being prolonged.
Effects similar to those described above can be obtained also in an air-conditioning apparatus including the corrugated-fin heat exchanger 20 according to Embodiment 2.
1 flat tube 2 corrugated fin 2a apex 3 inlet header 4 outlet header 5 protruding portion 6 second lug portion 7 first lug portion 7a first lug portion 7b first lug portion 7c first lug portion 7d first lug portion 7e first lug portion 7e1 first lug portion 7e2 first lug portion
7α first lug portion 7β first lug portion 10 corrugated-fin heat exchanger 10a corrugated-fin heat exchanger 10b corrugated-fin heat exchanger 11 intermediate header 20 corrugated-fin heat exchanger 30a outdoor-unit main body 30b outdoor-unit main body 31 fan 32a air outlet
32
b air outlet 33a air inlet 33b air inlet 34 compressor 40 frost formation portion
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-069429 | Mar 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/056675 | 3/3/2016 | WO | 00 |
