JPS6361894A - Heat exchanger with fins - Google Patents

Abstract

PURPOSE:To reduce the heat resistance of fins and provide a compact device with high performance by a method wherein heat transfer tubes in the second and subsequent rows to the air flow direction have partial overlapping parts with projection plane projecting to the down stream side from any heat transfer tube located on the upstream side of an air flow and a plurality of cut and raised parts opened to the air flow direction between the tubes on a fin are installed at the upper and lower parts of fin base plates which are left as they are and the relations among the height of the cut and raised part, a fin space, and a fin thickness are specified. CONSTITUTION:Heat transfer tubes 10 in the second and subsequent rows to the air flow direction are so arranged to overlap by half with the projection plane projecting to the down stream side from any heat transfer tube located on the upstream side of an air flow and the base plates 11 are so constituted to exist between a plurality of bridge-shaped cut and raised parts 13a, 13b which are opened at the upper and lower surface sides to the fins 11 as the base plates in the air flow direction on the fins 11 between the tubes 11. Assuming that a space between adjoining fins 11 is s, and a fin plate thickness is t, the height of the cut and raised part h is set as s/3<h<=(s+t)/2. Thereby, the distribution of the air flow velocity in the directions of parallel and right angles to the fins is made uniform.

Description

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

BACKGROUND OF THE INVENTION Conventionally, this type of heat exchanger has a U
It has a configuration 2 in which a copper tube 1 and a fin 2 made of aluminum or the like are connected to each other by a bend, and a refrigerant flowing inside the copper tube 1 and air 3 flowing between the fins 2 exchange heat. In recent years, such heat exchangers have been required to be smaller and have higher performance, but the air flow velocity between the fins is kept low from the viewpoint of noise etc., compared to the thermal resistance inside the tube.
Thermal resistance on the air side is high. Therefore, efforts are currently being made to reduce the difference in thermal resistance from the inside of the tube by expanding the heat transfer area on the air side. However, there are physical limits to enlarging the heat transfer surface, and there are also problems in terms of economy and space saving. This is an important issue when it comes to pottery.

FIGS. 9 and 10 show conventional examples of such heat exchangers. FIG. 9 is a plan view, and FIG. 10 is a cross-sectional view of the fin along the line CC. A refrigerant such as fluorocarbon is circulating inside the copper tube 4, and its heat is transmitted 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, air sent by a fan or the like from the direction of arrow 8 passes between 7476, but at that time, it exchanges heat with the fin surfaces having different temperatures. This action causes continuous heat exchange between the refrigerant and the air.

Problems to be Solved by the Invention The above-mentioned conventional example is called a slit fin having a fin cut to 6) and a raised 7. Compared to a flat fin with no processing on the fin surface, the surface thermal resistance is 4Q. ~60
It is lowering the temperature. However, when the fin surface is cut and raised in this way, the heat transfer coefficient in the run-up section of laminar flow is extremely high when applying the flat plate theory. It should be possible to achieve a thermal resistance value that is 60% or more lower than that of the surface. There are various possible reasons why this theoretical value cannot be achieved, but
Among them, the important reasons are: ■
The ventilation resistance of the airflow passing through the cut-and-raised portion 7 is high, and the amount of air passing through the portion other than the cut-and-raised portion 7 increases, so that the thermal performance at the cut-and-raised portion cannot be fully utilized.

In other words, 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 determined by the circumference and cut edges of the heat exchanger tubes 4, as shown in FIG. 9 and FIG. 1Q. The flow velocity in the gap between the cut-out 7 and the fin e above it is high, and the leading edge effect of the boundary layer of the cut-up 7 cannot be fully utilized.

■ The effective heat transfer area decreases because there is a wide still area. In particular, the cut-off area downstream of the copper pipe 4 on the upstream side of the airflow 8 covers the cut-out area 7 at the rear thereof, so these cut-off areas 7
increases the thermal resistance of the fins, increasing the average thermal resistance of the fins.

■ Copper tubes 4 are arranged in a staggered manner, and cut-outs 7 are provided at the front or rear of the copper tubes 4, which obstructs heat flow from the copper tubes 4 and reduces fin efficiency ■ Cuts on the upstream side of air flow 8 Since the downstream cut-off 7 is covered in the temperature boundary layer generated from the tip of the raised-up 7, the leading edge effect of the boundary layer of the cut-off 7 located on the downstream side is hardly utilized.

Therefore, the present invention aims to: (1) equalize the flow between the heat transfer tubes and between the cut and raised portions, prevent the amount of air passing through the cut and raised portions from decreasing, and realize a flow between parallel plates to achieve heat transfer close to the theoretical value; You can get the rate.

■ Only the cutting edges on the downstream side of the airflow are covered by the temperature boundary layer of the upstream cutting edges, and the leading edge effect of the boundary layer due to the cutting edges can be fully utilized. 0 Flow is guided by the phenomenon of fluid adhesion to the still area. ■ By adopting a heat transfer tube and heat transfer surface configuration that does not impede heat flow between heat transfer tubes, the above problems are solved and the thermal resistance of the fins is reduced, resulting in a compact and high-performance finned heat exchanger. The purpose is to propose the following.

Means for Solving the Problems The technical means of the present invention for solving the above problems is that the heat transfer tubes in the second and subsequent rows are located on the downstream side of any of the heat transfer tubes located on the upstream side of the airflow. A plurality of cutouts that partially overlap the projection plane of the fin and are open in the airflow direction between the heat transfer tubes of the fin are installed above and below, leaving the fin substrate, and the height of the cutouts is The relationship between the height h, the fin spacing S, and the thickness t of the fin plate is s/3 (h≦(s + t)/2).

For production The effect of this technical means is as follows.

In other words, ■ Since the tube rows in each heat transfer tube group are installed slightly offset in the airflow direction, a bridge-like or louver-like cut-out is constructed so that a part of it enters the downstream part of the tubes. As a result, there are no areas with high air velocity near the heat transfer tubes, and a sufficient flow rate of air can pass through the cut-and-bore, making it possible to fully utilize the thermal performance of the cut-and-bore. . ■Multiple cutouts opening in the airflow direction on the fins between the heat transfer tubes are installed above and below, leaving the fin substrate, and the relationship between the cutout height h, the fin spacing 8, and the fin plate thickness t. Since s/3 (h≦(s+t)/2), the air flow velocity in the interval between adjacent fins becomes uniform, and sufficient air flow can flow to the cut-and-raised part, so the cut-and-raised part It is possible to fully utilize the leading edge effect of the boundary layer. As described above, it is possible to achieve a value sufficiently close to the theoretical heat transfer coefficient of the run-up section of a parallel plate. ■ Each heat transfer tube is placed on the upstream side of the air flow. Because it is installed so that it partially overlaps with one of the projected planes of the pipe, the flow direction of the wake of the upstream pipe is induced by the downstream pipe to the cutoff area side of the downstream pipe.
The still area will decrease. Moreover, this phenomenon becomes more noticeable because cut-and-raised portions are provided between the heat exchanger tube groups. In other words, the cut-and-raised part has a side part that opens in the airflow direction and a leg part that is connected to the fin, but since this leg part is provided so as to enter the downstream part of the heat exchanger tube, the airflow is directed to the stop area side. As water flows, the still water area decreases. This effect will be even greater if the legs are tilted with the airflow and have an elevation angle.

■ Each heat exchanger tube row is not installed with a significant position shift from the upstream tube when viewed from the air flow direction, so the flow of heat to the fins between the heat exchanger tube groups is inhibited by the cut-and-rise. Less is.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying 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 in FIG. 1, and FIG. 3 is a detailed view of FIG. 2. 10 is a heat exchanger tube, 11 is a fin, 12 is a fin collar, and 13a and 13b are bridge-like cut-outs. A refrigerant circulates inside the heat exchanger tubes 10, and the heat of the refrigerant is transferred to the heat exchanger tubes 10. It is sequentially transmitted to the fin collar 12, the fin 11, and the cut-and-raised portions 13& and 13b. On the other hand, the airflow flowing from the airflow direction 14 is 74
When passing between 711 and 711, the heat transferred from the refrigerant is transferred indirectly through the surface in contact with the air.

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

With respect to the airflow direction, the heat exchanger tubes 1o in the second and subsequent rows are arranged so as to overlap by half with the downstream projection plane of any heat exchanger tube 10 located on the upstream side of the airflow. That is, since it can be configured so that a part of the cut-and-raised parts 13a and 13b enters the downstream part of the heat exchanger tube 10, a part where the air flow velocity is high does not occur in the vicinity of the heat exchanger tube 10, and the air flow direction 1
A uniform air flow velocity is obtained between the heat exchanger tubes 10 in the direction perpendicular to the direction of the heat exchanger tubes 4.

Furthermore, on the fins 11 between the heat exchanger tubes 1o, there are a plurality of bridge-like cutouts 13a that are open to the upper surface side with respect to the substrate of the fins 11 with respect to the air flow direction 14, and a plurality of bridge-like cutouts 13a that are open to the bottom surface side. The structure is such that the substrate of the fin 11 is present between the riser 13b, and the interval between adjacent fins 11 is set to 81.
If the thickness of the fin plate is t, then the cut height h is h=(s+
t)/2, the cut-and-raised portions 13a and 13b are located exactly at the center of the fin spacing S. Therefore, as shown in FIG. 3, a uniform air flow velocity can be obtained between adjacent fins 11.

As described above, both between the heat exchanger tubes 1o and between the fins 11,
Since the air flow velocity becomes uniform, a sufficient amount of air can flow to the cut and raised portions 13, and the boundary layer leading edge effect of the cut and raised portions 13 can be fully utilized. That is, it is possible to obtain a high value sufficiently close to the theoretical heat transfer coefficient of the run-up section of parallel flat plates.

In addition, as for the cut height h, as shown in Fig. 4, h
When = (s + t) / 2, the heat transfer performance is maximum, but h)
If it is s/s, it will have a maximum performance of about 90, or better than chi, but on the other hand, if it is h)(s+t)/2, the performance will be 13
This results in an increase in ventilation resistance due to the leg portions a and 13b. Therefore, if s/3 (h≦(s+t)/2), the heat transfer performance is sufficiently excellent for practical use. Next, in the airflow direction 1
4, the heat exchanger tubes 10 in the second and subsequent rows are arranged so as to overlap only half of the downstream projection plane of one of the heat exchanger tubes 1o on the upstream side of the airflow. Due to the presence of the downstream heat exchanger tube 1o, the flow direction is guided toward the cutoff area side of the downstream heat exchanger tube 1o, and the cutoff area is reduced. Furthermore, this phenomenon can be prevented by providing the cut and raised portions 13a and 13b between the heat exchanger tubes 10, and the leg portions of the cut and raised portions 13a and 13b that connect to the fins 11 are provided at an angle with respect to the airflow direction 14. This will become more noticeable, and the effect of reducing the still area will become greater.

In addition, since each of the heat exchanger tubes 1o is generally in a line with respect to the airflow direction 14, the transfer of heat on the fins 11 between the heat exchanger tubes 10 in the direction perpendicular to the airflow direction 14 is not hindered, and the fins Efficiency also increases.

From the above points, the overall heat transfer performance of the fins is significantly improved.

Next, other embodiments of the present invention will be described.

6, 6 and 7 show one of the other embodiments of the present invention, FIG. 6 is a plan view, and FIG.
The BB sectional view in the figure, and FIG. 7 is a detailed view of FIG. 6. 10
is a heat exchanger tube, 11 is a fin, 12 is a fin collar,
16a and 16b are bridge-like cutouts. Cut-out 'fr: 15 provided on the upper surface side of the fin substrate 11
a1 If the cut-off provided on the bottom side is 16b, the cut-off is installed in the order of the top-side cut-off 16a, the fin board 11, and the bottom-side cut-off 16b with respect to the airflow direction 14. . In a series of cut-and-raised groups, the height of the upper cut-out 16a' on the most upstream side with respect to the airflow direction 14 and the height of the lower-face cut-off 16b' on the most downstream side with respect to the airflow direction 14 are Ih1, then h1
= (g+t)/2, and the other cut height h2 is
h 2 =(s − t)/2. and,
The arrangement of the heat exchanger tubes 10 is the same as in the first embodiment.

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

As shown in FIG. 7, in a series of cut and raised groups, the height hl of the uppermost cut and cut 16a' on the most upstream side and the lower surface cut and cut 16' on the most downstream side with respect to the airflow direction 14 is h1=
(s+t)/2, so 15a' and 16
b' is located exactly at the center of the fin spacing S. Therefore,
Fins 11 at the airflow inflow and outflow portions of a series of cut-and-raised groups
A uniform air flow velocity is obtained between the two. In addition, in the central part, the cut height h2 is h1=(tt)/2, so the cut and raise heights 15a and 15b are equal to the fin plate thickness t with respect to the center line between adjacent 74711s. It has a misconfigured configuration. That is, a gap equal to the thickness of the plate is created between the lower surface cut and raised 15b and the upper surface cut and raised 15a of the adjacent fin, and since the airflow flowing through the gap is accelerated, the temperature generated at the lower surface cut and raised 15a is The boundary layer becomes thinner and the local heat transfer coefficient increases. Moreover, since the only deviation from the center line of the cut-outs 15a and 15b between adjacent fins 11 is the thickness of the fin plate, the airflow distribution between the fins becomes substantially uniform.

Therefore, the airflow distribution in the cut-and-raised group is generally uniform throughout, so the cut-and-raised groups 15a and 15a'.

The leading edge effect of the boundary layer in each of 1sb and 1sb' can be fully utilized, and the local heat transfer coefficient is improved by forming a region with a locally high flow velocity, so heat transfer is improved. Performance is further improved over the first embodiment.

In addition, to mention the cutting height h2 = (8-t)/2, the fin plate thickness t is usually 0.1 to 0.2- when aluminum is used as the material, and , the fin spacing B should be 8≧0 due to ventilation resistance and clogging problems of the heat exchanger.
．． It is used at 8 to 0.9 mm. Therefore, s) 3
Since t, h2 = (s-t)/2>
It becomes s/3.

It satisfies the scope of this patent claim.

Effects of the Invention As described above, the present invention includes fins that are arranged in parallel at regular intervals and through which the airflow flows, and fins that are inserted at right angles to the fins and through which the fluid flows and are arranged in multiple rows in the airflow direction. It consists of a heat exchanger tube with a second
Heat exchanger tubes 75ζ in the rows and subsequent rows partially overlap with the downstream projection plane of any heat exchanger tube on the upstream side of the airflow, and have a plurality of cutouts opening in the airflow direction between the heat exchanger tubes of the fin. The fins are installed on the top and bottom leaving the fin board, and the relationship between the cut height h, the fin spacing B, and the fin plate thickness t is s/3 (h≦(s+t)/2). Since it is an exchanger, it has the following effects.

■ The airflow velocity distribution between the heat transfer tube groups and between adjacent fins, that is, in the direction parallel and perpendicular to the fins, is made uniform, and the fin surface heat transfer coefficient is improved due to the leading edge effect of the boundary layer of the cut and raised edges. Improve greatly.

■ The flow direction of the wake from the heat transfer tube on the upstream side of the airflow is changed by the heat transfer tube on the downstream side and flows toward the cutoff area, reducing the area of the cutoff area and increasing the effective heat transfer area.

- Since the heat transfer tubes are not installed with significant deviations from each other when viewed from the airflow direction, the flow of heat from the heat transfer tubes to the fins and cutouts is not obstructed, improving fin efficiency.

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

[Brief explanation of the drawing]

Fig. 1 is a plan view of a finned heat exchanger according to an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1, Fig. 3 is a detailed view of the same cross-section, and Fig. 4 is a heat transfer diagram. An explanatory diagram showing the relationship between performance and cut height, FIG. 6 is a plan view of a finned heat exchanger according to another embodiment of the present invention, FIG. 6 is a sectional view taken along the line B-B in FIG. 5,
7 is a detailed cross-sectional view of the same, FIG. 8 is a perspective view of a conventional example of a finned heat exchanger, FIG. 9 is a plan view of the same, and FIG.
It is a sectional view taken along the line CC in the figure. 10... Heat exchanger tube, 11... Fin, 1
3.13a. 13b, 15a, 15b...Cut up, 14.
... Airflow direction, h ... Cutting height, S
...Fin spacing, t...Fin plate thickness. Name of agent: Patent attorney Toshio Nakao and 1 other person/θ
--- Heat exchanger tube l / --- Fin / 3θ 3b --- Raise the sword / 4 --- Sword 6 Δ Shigamesa Figure 2 Figure 3 Figure 4 “Wariri rice cake layer ih-

Claims (4)

[Claims] (1) Consisting of fins arranged in parallel at regular intervals, through which air flows, and heat transfer tubes arranged in multiple rows in the air flow direction, inserted at right angles to the fins, through which fluid flows, With respect to the airflow direction, the heat transfer tubes in the second row and subsequent rows partially overlap the downstream projection plane of any heat transfer tube located on the upstream side of the airflow, and the fins have a portion between the heat transfer tubes. A plurality of cut-outs opening in the airflow direction are installed above and below, leaving the fin board, and the relationship between the cut-out height h, the fin spacing s, and the fin plate thickness t is expressed as s/3<h≦
(s+t)/2 heat exchanger with fins. (2) The cut-outs provided on the upper and lower sides of the fin board are the top-side cut-outs and the bottom-side cut-outs, and in the airflow direction, the top-side cut-outs, the fin board, and the bottom side. Claim 1 in which the cut-offs are installed in the order of the side cut-up
Heat exchanger with fins as described in section. (3) The finned heat exchanger according to claim 1, wherein the cut-outs are installed so that the fin board is present between the upper side cut-outs and the lower side cut-outs with respect to the airflow direction. vessel. (4) The heat exchanger with fins according to claim 2 or 3, wherein the cut-outs are installed so that the height of the cut-outs with respect to the fin board is partially different.