JPH0686996B2 - Heat exchanger with fins - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger used for air conditioning, refrigeration, etc., for exchanging heat between a refrigerant and a fluid such as air.

2. Description of the Related Art Conventionally, as shown in FIG.
The copper pipe 1 and the fins 2 made of aluminum or the like are connected to each other by a bend, and the refrigerant flowing inside the copper pipe 1 and the air 3 flowing between the fins 2 exchange heat. In recent years, such heat exchangers are required to be smaller and have higher performance, but the air flow velocity between fins is kept low from the viewpoint of noise, etc. Side thermal resistance is high. Therefore, we are currently working to expand the area of the heat transfer tube on the air side to reduce the difference with the heat resistance inside the tube. However, there is a physical limit to the expansion of the heat transfer surface, and there is a problem in terms of economical efficiency and space saving, and reducing the heat resistance on the air side is such a heat exchange. This is an important issue for vessels.

9 and 10 show a conventional example of such a heat exchanger. FIG. 9 is a plan view, and FIG. 10 is a sectional view of a C-C plane fin. Refrigerant such as CFCs circulates inside the copper tube 4, and the heat is transferred from the copper tube 4 to the fin collar 5 and then to the fins 6 and the cut and raised portions 7. On the other hand, the air sent by the fan or the like from the direction of the arrow 8 passes between the fins 6, and at that time, heat is transferred to and from the fin surfaces having different temperatures. By this action, heat exchange between the refrigerant and air is continuously performed.

Problems to be Solved by the Invention The above-described conventional example is called a slit fin having a cut-and-raised fin 7 and has a surface thermal resistance of 40 to 50 as compared with a flat fin having no fin surface. % Has been reduced. However, when the cut-and-raised parts are provided on the fin surface in this manner, the application of the flat plate theory causes the heat transfer coefficient in the run-up section of the laminar flow to be very high. It should be possible to achieve a thermal resistance value that is 50% or more lower than the thermal resistance value of the surface. There are various reasons why this theoretical value cannot be achieved. Among them, the most important reason is that the ventilation resistance of the air flow passing through the cut-and-raise 7 is high and the cut-and-raised 7
Since the amount of air passing through other parts increases, the thermal performance at the cut-and-raised part is not fully utilized.

That is, the flow velocity distribution in the plane parallel to the fins 6 and the flow velocity distribution in the plane perpendicular to the fins 6 ′ are, as shown in FIGS. 9 and 10, around the heat transfer tube 4 and cut and raised. The flow velocity in the gap between 7 and the fin 6 on the upper side is high, and the leading edge effect of the boundary layer of the cut-and-raised 7 is not sufficiently utilized. The effective heat transfer area decreases due to the wide existence of the still water area. In particular, the water-stopping region of the wake of the copper tube 4 on the upstream side of the air flow 8 covers the cut-and-raised parts 7 at the rear part thereof, so that the thermal resistance of these cut-and-raised parts 7 increases and the average thermal resistance of the fins increases. . Since the copper pipes 4 are arranged in a striped pattern and the cut-and-raised parts 7 are provided in front of or behind the copper pipe 4, heat flow from the copper pipe 4 is impeded and fin efficiency is reduced. In front of the boundary layer of the cut-and-raised portion 7 located on the downstream side, the downstream-side cut-and-raised portion 7 is covered in the temperature boundary layer generated from the tip of the cut-and-raised portion 7 on the upstream side of the air flow 8. The edge effect is hardly used.

Therefore, the present invention makes the flows between the heat transfer tubes and between the cut-and-raised parts uniform, does not reduce the amount of air passing through the cut-and-raised parts, and realizes the flow between parallel plates to achieve a heat transfer coefficient close to the theoretical value. Can be obtained. The cut-raising on the downstream side of the air flow is prevented from being covered by the temperature boundary layer of the cut-raising on the upstream side, and the boundary layer leading edge effect due to the cut-raising can be fully utilized. Flow is induced by the phenomenon of fluid adhesion to the still water area. By adopting a heat transfer tube and heat transfer surface configuration so as not to obstruct the heat flow between the heat transfer tubes, the above problems are solved, the heat resistance of the fins is reduced, and a compact and high-performance heat exchanger with fins is provided. It is intended to be a proposal.

Means for Solving the Problems The technical means of the present invention for solving the above problems is such that the heat transfer tubes in the second and subsequent rows are downstream of one of the heat transfer tubes located upstream of the air flow with respect to the air flow direction. The projection and the projection surface are partially overlapped with each other and the fins are installed above and below the fin substrate with the fin substrate left open in the airflow direction between the heat transfer tubes. The relationship between the height h, the fin spacing s, and the fin plate thickness t is s / 3 <h ≦ (s + t) / 2.

Action The action of this technical means is as follows.

That is, since the tube rows in each heat transfer tube group are installed slightly displaced in the air flow direction, a bridge-shaped or louvered cut-and-raised part can be configured so that a part of the cut-and-raised part enters the wake of the tubes. Since there is no part where the air velocity is high near the heat transfer tube, a sufficient flow rate of air can be passed to the cut-and-raised parts, and the thermal performance of the cut-and-raised parts can be fully utilized. A plurality of cut-and-raised parts opened in the air flow direction are installed above and below the fins between the heat transfer tubes, leaving the fin substrate, and the cut-and-raised height and h, the fin spacing s, and the fin plate thickness t.
And s / 3 <h ≦ (s + t) / 2, the air flow velocity in the space between adjacent fins becomes uniform, and a sufficient air flow rate can be made to flow to the cut and raised portions. The leading edge effect of the boundary layer due to the raising can be fully utilized. From the above, by the above, it is possible to realize a value close enough to the theoretical heat transfer coefficient in the run-up section of a parallel plate. Since each heat transfer tube is installed so that it partially overlaps with one of the projection planes on the upstream side of the air flow, the wake of the upstream side tube will flow toward the downstream side of the downstream side tube by the downstream side tube. It is attracted to the water stop side and the water stop area decreases. Further, this phenomenon becomes more remarkable because the cut and raised portions are provided between the heat transfer tube groups. In other words, the cut-and-raised part has a side part that is open in the air flow direction and a leg part that is connected to the fins, but since the leg part is provided so as to enter the wake part of the heat transfer tube, the air flow flows to the water stop region side. As a result, the water cutoff area will decrease. This is more effective if the legs are inclined with respect to the airflow and have an elevation angle.
Since each heat transfer tube row is not installed so as to be significantly displaced from the upstream tube in the air flow direction, the heat flow to the fins between the heat transfer tube groups may be hindered by cutting and raising. Few.

Embodiment One embodiment of the present invention will be described below with reference to the accompanying drawings.

1 is a plan view of a heat exchanger with fins according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is a detailed view of FIG. 10 is a heat transfer tube, 11 is a fin, 12 is a fin collar, and 13a and 13b are bridge-shaped cut-and-raised parts. Heat transfer tube
A refrigerant circulates inside 10 and the heat of the refrigerant is sequentially transferred to the heat transfer tube 10, the fin collar 12, the fin 11, and the cut-and-raised parts 13a and 13b. On the other hand, airflow direction 14
When passing between the fins 11, the air flow flowing from heat exchanges the heat transferred from the refrigerant indirectly via the surface in contact with the air.

Next, the operation of the configuration of this embodiment will be described.

The heat transfer tubes 10 in the second and subsequent rows are arranged so as to be half overlapped with the downstream projection surface of one of the heat transfer tubes 10 on the upstream side of the air flow in the air flow direction. That is, since the cut-and-raised parts 13a and 13b can be configured such that a part of the cut-and-raised parts 13a and 13b enter into the wake of the heat transfer tube 10, there is no part where the air flow velocity is high in the vicinity of the heat transfer tube 10, and in the airflow direction 14. A uniform air flow velocity can be obtained between the heat transfer tubes 10 in the orthogonal direction.

In addition, on the fins 11 between the heat transfer tubes 10, a plurality of bridge-shaped cut-and-raised portions 13a opened on the upper surface side with respect to the substrate of the fins 11 in the air flow direction 14 and bridge-shaped cut-outs opened on the lower surface side. It is configured such that the substrate of the fin 11 is present between the raised portion 13b and
Assuming that the space between adjacent fins 11 is s and the fin substrate is t, the cut-and-raised height h is set to h = (s + t) / 2, so the cut-and-raised parts 13a and 13b are located at the center of the fin space s, exactly. To position. Therefore, as shown in FIG. 3, a uniform air flow velocity can be obtained between the adjacent fins 11.

As described above, since the air flow velocity is uniform both between the heat transfer tubes 10 and between the fins 11, a sufficient air flow rate can be made to flow to the cut-and-raised portion 13, and the boundary layer leading edge effect due to the cut-and-raised 13 can be obtained. You can make good use of it. That is, it is possible to obtain a high value which is sufficiently close to the theoretical heat transfer coefficient in the approaching section of the parallel plate.

Regarding the cut-and-raised height h, as shown in FIG.
= (S + t) / 2, the heat transfer performance is maximized, but h> s /
If it is 3, the performance is about 90% or more of the maximum, but conversely, h
When> (s + t) / 2, the ventilation resistance due to the legs of the cut-and-raised parts 13a and 13b is increased. Therefore, s / 3 <h ≦ (s
If + t) / 2, the heat transfer performance is sufficiently excellent in practical use. Next, the heat transfer tubes 10 in the second and subsequent rows with respect to the air flow direction 14
Is arranged so as to half overlap with the downstream projection surface of one of the heat transfer tubes 10 on the upstream side of the air flow, so that the wake of the upstream heat transfer tube 10 has a flow direction due to the presence of the downstream heat transfer tube 10. Is attracted to the water stop side of the downstream heat transfer pipe 10, and the water stop area decreases. Furthermore, since partitioning and raising 13a and 13b are provided between the heat transfer tubes 10, and leg portions connected to the fins 11 of the raising and cutting 13a and 13b are provided to be inclined with respect to the air flow direction 14,
This phenomenon becomes more prominent, and the effect of reducing the still water area becomes greater.

Further, since the heat transfer tubes 10 are substantially in line with the air flow direction 14, the heat transfer tubes 10 in the direction perpendicular to the air flow direction 14 are arranged.
Without hindering the transfer of heat on the fins 11 between
Fin efficiency is also high.

From the above points, the heat transfer performance of the entire fin is significantly improved.

Next, another embodiment of the present invention will be described.

FIGS. 5, 6, and 7 show one of other embodiments of the present invention. FIG. 5 is a plan view and FIG. 6 is a fifth view.
FIG. 7 is a detailed view of FIG. 6 taken along the line BB of FIG. 10 is a heat transfer tube, 11 is a fin, 12 is a fin collar, and 15a and 15b are bridge-shaped cut-and-raised parts. When the cut-and-raised parts provided on the upper surface side of the fin substrate 11 are 15a and the cut-and-raised parts provided on the lower surface side are 15b, the upper-surface-side cut-and-raised parts 15a, the fin substrate 11, and the lower surface side in the airflow direction 14. Cuts and cuts are installed in the order of 15b. In a series of cut-and-raised group, if the 'height and lower surface cut-raised 15b of the most downstream side of the' height of the figure cutting force without 15a of most upstream side is h ₁ for the air flow direction 14 h ₁ =
(S + t) / 2, and the other cut-and-raised height h ₂ is h ₂ = (s
-T) / 2. The arrangement of the heat transfer tubes 10 is the same as in the first embodiment.

Next, the operation of the configuration of this embodiment will be described.

In the series of cut-and-raised groups as shown in FIG. 7, the height h _{1 of the} uppermost-side cut-and-raised portion 15a ′ on the uppermost stream side and the lowermost-side cut-and-raised portion 15b ′ on the most downstream side in the airflow direction 14 is h ₁ = (S + t) / 2
Therefore, 15a 'and 15b' are located at the center of the fin spacing s. Therefore, a uniform air flow velocity can be obtained between the fins 11 at the air flow inlet and outlet of the series of cut and raised parts. In addition, in the central part, the cut and raised height h ₂
Is h ₁ = (s−t) / 2, the cut-and-raised parts 15 a and 15 b are displaced from the center line between the adjacent fins 11 by the fin plate thickness t. That is, a gap corresponding to the plate thickness t is generated between the lower surface cut-and-raised part 15b and the upper surface cut-and-raised part 15a of the adjacent fin, and the airflow flowing through the gap is accelerated, so that the temperature generated in the cut-and-raised part 15a is increased. The boundary layer becomes thinner and the local heat transfer coefficient improves. Moreover, the deviation of the cut-and-raised parts 15a and 15b between the adjacent fins 11 with respect to the center line is only the fin plate thickness, so that the air flow distribution between the fins is substantially uniform. Therefore, since the airflow distribution in the cut-and-raised group is almost uniform overall, the cut-and-raised 15a, 15
The boundary layer leading edge effect in each of a ′, 15b, and 15b ′ can be fully utilized, and the local heat transfer coefficient is improved by locally forming the portion with high flow velocity. The heat transfer performance is further improved as compared with the first embodiment.

Incidentally, referring to the cut-and-raised height h ₂ = (s−t) / 2, usually, the fin plate thickness t is t = 0.1 to 0.2 mm when aluminum is used as the material, and The fin spacing s is set to s ≧ 0.8 to 0.9 mm because of the problems of ventilation resistance and clogging of the heat exchanger. Therefore, since s> 3t, h ₂ = (s−
t) / 2>s> 3, which satisfies the claims of the present invention.

EFFECTS OF THE INVENTION As described above, according to the present invention, fins that are arranged in parallel at regular intervals and through which an air flow flows, and fins that are inserted at a right angle to the fins and through which fluid flows inside are arranged in a plurality of rows in the air flow direction. It is composed of a heat transfer tube and a second
The heat transfer tubes on and after the second row have a partial overlap with the downstream projection surface of one of the heat transfer tubes on the upstream side of the air flow, and
A plurality of cut-and-raised parts opened in the airflow direction between the heat transfer tubes of the fins are installed above and below the fin substrate, and the relationship between the cut-and-raised height h and the fin spacing s and the fin plate thickness t is shown. Since the heat exchanger with fins satisfies s> 3 <h ≦ (s + t) / 2, it has the following effects.

The airflow velocity distribution is uniform between the heat transfer tube groups and between adjacent fins, that is, in the direction parallel to and perpendicular to the fins, and the fin surface heat transfer coefficient is high due to the boundary layer leading edge effect of cut and raised. Improves width.

The wake of the heat transfer tube on the upstream side of the air flow changes its direction by the heat transfer tube on the downstream side and flows to the water stop area side, so that the area of the water stop area decreases and the effective heat transfer area increases.

Since the heat transfer tubes are not installed so as to be significantly staggered when viewed from the air flow direction, the flow of heat from the heat transfer tubes to the fins and the cut and raised portions is not obstructed, and fin efficiency is improved.

Due to the above effects, heat transfer performance is improved, and a small-sized and high-performance finned heat exchanger can be realized.

[Brief description of drawings]

1 is a plan view of a heat exchanger with fins according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, FIG. 3 is a detailed sectional view of the same, and FIG. 4 is heat transfer. FIG. 5 is an explanatory view showing the relationship between performance and cut-and-raised height, FIG. 5 is a plan view of a heat exchanger with fins according to another embodiment of the present invention, and FIG. 6 is a sectional view taken along line BB of FIG.
FIG. 7 is a detailed view of the same section, FIG. 8 is a perspective view of a heat exchanger with fins showing a conventional example, FIG. 9 is a plan view of the same, and FIG. 10 is a sectional view taken along line CC of FIG. . 10 …… Heat transfer tube, 11 …… Fin, 13,13a, 13b, 15a, 15b ……
Cut and raised, 14 ... Air flow direction, h ... Cut and raised height, s ...
... fin spacing, t ... fin plate thickness.

Front page continuation (72) Inventor Kaoru Kato 3-22, Takaidahondori, Higashi-Osaka, Osaka Prefecture Matsushita Refrigerator Co., Ltd. (72) Inventor Tomoaki Ando 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. ( 72) Inventor Nao Kusuhara, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A fin, which is arranged in parallel at regular intervals and through which an air flow flows, and heat transfer tubes which are inserted at a right angle to the fin and through which a fluid flows, arranged in a plurality of rows in the air flow direction. The heat transfer tubes in the second and subsequent rows have a partial overlap with the downstream projection surface of any of the heat transfer tubes on the upstream side of the air flow with respect to the air flow direction, and the heat transfer tubes of the fins are provided. A plurality of cut-and-raised parts that are open in the air flow direction are installed above and below the fin substrate while leaving the fin substrate, and the relationship between the cut-and-raised height h, the fin spacing s, and the fin plate thickness t is s / 3 < A finned heat exchanger with h ≦ (s + t) / 2. 2. A fin substrate is provided with cut-and-raised parts provided on the upper surface side and the lower-surface side with respect to the fin substrate as upper surface-side cut-and-raised parts, and with respect to the air flow direction. ,
The heat exchanger with fins according to claim 1, wherein the cut-and-raised parts are installed in the order of the cut-and-raised parts on the lower surface side. 3. The finned assembly according to claim 1, wherein the cut-and-raised part is provided so that the fin substrate exists between the cut-and-raised part on the upper surface side and the cut-and-raised part on the lower surface side with respect to the air flow direction. Heat exchanger. 4. The cut-and-raised parts are provided so that the heights of the cut-and-raised parts with respect to the fin substrate are partially different.
A heat exchanger with fins according to item 3 or 3.