JPH0796994B2 - 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. 3, a heat exchanger of this type has a heat transfer tube 1 made of copper and a fin 2 made of aluminum, etc., which are connected to each other by a U-bend. The refrigerant flowing inside 1 and the air 3 flowing between the fins 2 perform heat exchange. In recent years, such heat exchangers have been required to be small in size and have high performance, but the air flow velocity between the fins is kept low from the viewpoint of noise, etc. Side thermal resistance is high. Therefore, we are currently trying to reduce the difference with the heat resistance inside the tube by expanding the heat transfer area on the air side. However,
There is a physical limit to expanding the heat transfer area, and there are problems from the viewpoint of economical efficiency and space saving.
Reducing the thermal resistance on the air side is an important issue in such heat exchangers.

FIG. 2 is a plan view of a conventional example of such a heat exchanger. Refrigerant such as CFC is circulated inside the heat transfer tube 4, and the heat is transferred from the heat transfer tube 4 to the fin collar 5, fins 6 and cut-and-raised parts 7. On the other hand, the air sent from the airflow direction 8 by the fan or the like passes between the fins 6, and at that time, heat is transferred to and from the surfaces of the fins 6 having different temperatures. Due to this action, heat exchange between the refrigerant and air is continuously performed.

Problems to be Solved by the Invention The above-mentioned conventional example is called a slit fin having a cut-and-raised portion 7 in the fin 6, and has a surface thermal resistance of 40 to 50 as compared with a flat fin having no processing on the fin surface.
% Has been reduced. However, when such a cut-and-raised is applied, the heat transfer coefficient in the run-up section of the laminar flow is very high when the parallel plate theory is applied, which is 50% of the current heat resistance value of the fin surface of such a slit fin. The lower thermal resistance value should be realized. There are various possible reasons why this theoretical value cannot be achieved, but the most important of these is as follows.

(1) Since the ventilation resistance of the air flow passing through the cut-and-raised part 7 is high and the amount of air passing through the portion other than the cut-and-raised part 7 increases, the thermal performance of the cut-and-raised part 7 cannot be fully utilized.
That is, as shown in FIG. 4, the flow velocity distribution in the plane parallel to the fins 6 is such that the flow velocity around the heat transfer tube 4 is fast, and the boundary layer leading edge effect in the cut-and-raised portion 7 is not sufficiently utilized.

(2) Since there is a wide dead water region generated in the wake of the heat transfer tube 4, the effective heat transfer area contributing to heat transfer is reduced.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems and to propose a fin heat exchanger which is small in size, high in heat resistance, and high in fin performance.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to increase the pipe pitch in the direction perpendicular to the air flow to be larger than the pipe pitch in the air flow direction of the heat transfer pipes, and In addition to providing cut-and-raised on the fin surface at, and with respect to the air flow direction,
The projection surface of the (2N-1) th row (N: positive integer) to the downstream side of the heat transfer tube has a partial overlap with the heat transfer tube in the 2Nth row immediately after that, but the (2N + 1) th row And the heat transfer tubes in the 2 (N + 1) th column are designed not to have a partial overlap.

Action The action of this technical means is as follows.

(1) The projection plane to the downstream side of the (2N-1) th row (N: positive integer) of the heat transfer tubes in the airflow direction partially overlaps with the heat transfer tube immediately following it in the 2Nth row. In other words, because the heat transfer tubes in the 2N-th row are installed slightly offset from the heat transfer tubes in the (2N-1) -th row, the bridge-shaped or louver-shaped cut-and-raised parts of the heat-transfer tubes are It can be installed so as to enter the wake part, and as a result, a part with a high air velocity does not occur in the vicinity of the heat transfer tube and a sufficient flow rate of air can pass to the cut and raise, and the boundary layer before the cut and raise The edge effect can be fully utilized. That is, it is possible to realize a value sufficiently close to the theoretical heat transfer coefficient in the run-up section of the parallel plate.

(2) Similar to (1), (2N-1)
Since the projection surface of the heat transfer tubes in the second row (N: positive integer) to the downstream side has a partial overlap with the heat transfer tubes in the second row immediately after that, that is, the heat transfer tubes in the second row Since the heat transfer tubes in the (2N-1) th row are slightly displaced from each other, the upstream side, that is, the wake of the heat transfer tubes in the (2N-1) th row is the downstream side, that is, the 2Nth row. By the heat transfer tube, the flow direction is toward the dead water region side of the 2Nth row heat transfer pipe, and although the flow velocity is slow, the dead water region that is attracted and generated in the wake of the heat transfer pipe decreases, and the shape resistance due to the heat transfer pipe also decreases. Further, this phenomenon becomes more remarkable because the fin surface is provided on the fin surface between the heat transfer tubes in the direction perpendicular to the air flow. 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 this leg part is provided so as to enter the wake part of the heat transfer tube, the air flow is the dead water region side. The flow of water to the heat transfer tube is reduced, and the dead water area generated behind the heat transfer tube is reduced. this is,
Increasing the effect by inclining the legs with respect to the airflow gives them an elevation angle.

(3) The projection plane to the downstream side of the (2N-1) th row (N: positive integer) of the heat transfer tubes in the airflow direction partially overlaps with the heat transfer tube in the 2Nth row immediately after that. And (2N + 1)
Since there is no partial overlap with the heat transfer tubes in the second row and the second (N + 1) th row, that is, (2N +
1) Since the space between the heat transfer tubes in the first row is large, the airflow easily flows between them and the heat transfer performance around the heat transfer tubes is improved. In addition, since the eddy current generated from the cut-and-raised legs on the upstream side of the air flow passes between the heat transfer tubes in the 2Nth row and the (2N + 1) th row, the cut-and-raised boundary at the downstream side of the airflow The layer leading edge effect is promoted and the heat transfer performance is improved. In addition, even if condensed water adheres to the fin side, 2N
Condensed water easily falls through between the heat transfer tubes in the second row and the heat transfer tubes in the (2N + 1) th row, and the heat exchange performance hardly deteriorates.

Example Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a plan view of a heat exchanger with fins according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. 10 is a heat transfer tube, 11 is a fin, 12 is a fin collar, and 13 is a bridge-shaped cut and raised portion. A refrigerant circulates inside the heat transfer tube 10, and the heat of the refrigerant is generated by the heat transfer tube 10 and the fin collar.
12, the fins 11, and the cut and raised pieces 13 are sequentially transmitted.
The pipe pitch Pd in the direction perpendicular to the air flow is made larger than the pipe pitch Pr in the air flow direction 14 of the heat transfer pipes 10, and the legs 11 are cut and raised on the fin 11 surface between the heat transfer pipes in the direction perpendicular to the air flow to form the air flow direction 14
The projection surface 15a on the downstream side of the heat transfer tube 10a in the first row with respect to the airflow direction 14 is approximately 1 / th of that of the heat transfer tube 10b in the second row immediately after that. Projection surface 15c on the downstream side of the third-row heat transfer tube 10c that has an overlap of 2
Has a half overlap with the heat transfer tube 10d in the fourth row immediately after that, but the projection surface 15b to the downstream side of the heat transfer tube 10b in the second row
However, on the center line of 1/2 of the pipe pitch Pd in the direction perpendicular to the airflow of the heat transfer tubes 10b in the second row so as not to partially overlap with the heat transfer tubes 10c, 10d in the third and fourth rows. It is located in.
In this case, Pd> 3D (D: outer diameter of fin collar). On the other hand, the airflow flowing in the airflow direction 14 indirectly transfers the heat transferred from the refrigerant through the surface in contact with the air when passing between the fins 11.

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

(1) The heat transfer tubes 10a in the first row and the projection surface 15c on the downstream side of the heat transfer tubes 10c in the third row with respect to the air flow direction 14 are the heat transfer tubes 10b in the second row in the subsequent flow, and Since the heat transfer tubes 10d in the fourth row are arranged to partially overlap with each other, that is, the heat transfer tubes 10b in the second row and the heat transfer tubes 10d in the fourth row are the heat transfer tubes 10a in the first row. , And because it is installed slightly offset from the heat transfer tubes 10c in the third row, the bridge-shaped cut-and-raised parts 13 can be installed so as to enter the wake of the heat transfer tubes 10a, 10c. A portion having a high air flow velocity does not partially occur in the vicinity of the heat pipe 10, and a sufficient flow rate of air can be passed to the cut-and-raised parts 13, and the boundary layer leading edge effect by the cut-and-raised parts 13 can be fully utilized. That is, it is possible to realize a value sufficiently close to the theoretical heat transfer coefficient in the run-up section of the parallel plate.

(2) Similarly to (1), the projection plane 15c on the downstream side of the heat transfer tubes 10a in the first row and the heat transfer tubes 10c in the third row with respect to the air flow direction 14 is in the second row in the subsequent flow. Heat transfer tube 10b, and
Since the heat transfer tubes 10d in the fourth row are arranged so as to partially overlap with each other, that is, the heat transfer tubes 10b in the second row,
Also, since the heat transfer tubes 10d in the fourth row are installed slightly displaced from the heat transfer tubes 10a in the first row and the heat transfer tubes 10c in the third row, the upstream side, that is, the first and third rows The wake of the heat transfer tubes 10a, 10c in the second row is the downstream side, that is, the dead water area of the heat transfer tubes 10b, 10d in the second and fourth rows in the flow direction due to the heat transfer tubes 10b, 10d in the second and fourth rows. To the side, the flow velocity is slow, but it is attracted, the dead water area of the heat transfer tubes 10a, 10c decreases,
In addition, the shape resistance due to the heat transfer tube is also reduced. Further, this phenomenon becomes more remarkable because the cut-and-raised parts 13 are provided on the surface of the fin 11 between the heat transfer tubes 10 in the direction perpendicular to the air flow. In other words, the cut-and-raised portion 13 has a side portion opened in the air flow direction 14 and a leg portion connected to the fin 11.
Since it is provided so as to enter the downstream portion of the heat transfer tube 10, the air flow is allowed to flow toward the dead water area, and the dead water area generated in the downstream area of the heat transfer tube 10 is reduced. This is more effective if the legs are inclined with respect to the airflow to have an elevation angle.

(3) The projection planes 15a, 15c of the heat transfer tubes 10a, 10c in the first and third rows with respect to the air flow direction 14 are the heat transfer tubes 10b, 10d in the second and fourth rows immediately after that.
Has a partial overlap with the second row heat transfer tube 10b.
And the heat transfer tubes 10c in the third row have no partial overlap, that is, the heat transfer tubes 10b in the second row and the heat transfer tubes 10d in the third row.
Since the distance between and is large, the airflow easily flows between them and the heat transfer performance around the heat transfer tube 10 is improved. In addition, since the vortex flow generated from the cut-and-raised legs 15 on the upstream side of the air flow passes between the heat transfer tubes 10b in the second row and the heat-transfer tubes 10c in the third row, the cut-and-raised portions on the downstream side of the air flow 13 Boundary layer leading edge effect is promoted and heat transfer performance is improved. Also fin 11
Even when condensed water adheres to the surface, condensed water easily falls through between the heat transfer tubes 10b in the second row and the heat transfer tubes 10c in the third row, and heat exchange performance hardly deteriorates. .

From the above points, the thermal resistance of the fins can be remarkably reduced as a whole.

Effects of the Invention As described above, the present invention is arranged in parallel at a constant interval, the fins through which the airflow flows, and the heat transfer tubes that are inserted through the fins at a right angle and through which the fluid flows,
The pitch of the heat transfer tubes in the direction perpendicular to the air flow is made larger than the pitch in the direction of the air flow, and fins are provided on the fin surfaces between the heat transfer tubes in the direction perpendicular to the air flow, and (2N- 1) The projection surface of the heat transfer tubes in the second row (N: a positive integer) to the downstream side has a partial overlap with the heat transfer tubes in the second row immediately after that, but the (2N + 1) th row and the second ( N +
1) The heat transfer tubes in the row are finned heat exchangers that do not partially overlap with each other, and therefore have the following effects.

(1) The flow velocity distribution between the heat transfer tubes in the direction perpendicular to the air flow is made uniform, the amount of air passing through the cut and raised portions does not decrease, and the heat transfer coefficient on the fin surface is greatly increased by the boundary layer leading edge effect due to the cut and raised portions. improves.

(2) The wake of the heat transfer tube in the (2N-1) th row is generated in the wake of the heat transfer tube because the flow direction of the heat transfer tube in the 2Nth row is attracted to the dead water region side of the heat transfer tube in the 2Nth row. The dead water area decreases, the effective heat transfer area increases, and the shape resistance due to the heat transfer tube also decreases.

(3) Since the distance between the 2Nth row heat transfer tube and the (2N + 1) th row heat transfer tube is large, the airflow easily flows between them and the heat transfer performance around the heat transfer tube is improved. In addition, since the vortex flow generated from the cut-and-raised legs on the upstream side of the air flow passes between the heat transfer tubes in the 2Nth row and the (2N + 1) th row,
The leading edge effect of the boundary layer in cutting and raising on the downstream side of the air flow is promoted, and the heat transfer performance is improved. In addition, even if condensed water adheres to the fin surface, the heat transfer tubes (2N +
1) Condensed water easily falls through between the heat transfer tubes in the second row and the heat exchange performance hardly deteriorates.

With the above effects, the heat transfer performance is remarkably improved, and a compact and high-performance finned heat exchanger can be realized.

[Brief description of drawings]

FIG. 1 is a plan view of a finned heat exchanger according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 2, and FIG. 3 is a perspective view of a finned heat exchanger showing a conventional example. The figure is a plan view of the same. 10,10a, 10b, 10c, 10d …… Heat transfer tube, 11 …… Fin, 13 ……
Cut and raised, 14 ... air flow direction, 15a, 15b, 15c ... projection plane.

Front Page Continuation (72) Inventor Hachiro Koma 3-22 Takada Hondori, Higashi-Osaka City, Osaka Prefecture Matsushita Refrigerator Co., Ltd. (72) Hiroyuki Tanaka 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. (56) Reference JP-A-61-243292 (JP, A)

Claims (1)

[Claims] 1. A fin which is arranged in parallel at a constant interval and through which an air flow flows, and a heat transfer tube which is inserted through the fin at a right angle and through which a fluid flows, the heat transfer tube having an air flow direction The pipe pitch in the direction perpendicular to the air flow is made larger than the pipe pitch, and the cut-and-raised parts are provided on the fin surfaces between the heat transfer pipes in the direction perpendicular to the air flow, and the (2N-1) th row (N : Positive integer) The projection surface of the heat transfer tube on the downstream side partially overlaps with the heat transfer tube in the 2Nth row immediately after that, but the (2N + 1) th row and 2 (N + 1) th row
A heat exchanger with fins that does not partially overlap the heat transfer tubes in the row.