JPS633185A - Finned heat exchanger - Google Patents

Abstract

PURPOSE:To improve the heat transfer performance of the finned heat exchanger by constituting respective heat transfer tubes so that a plane of projection of any of heat transfer tubes which is located at the upstream side of an airstream onto the downstream side is partially overlapped on the heat transfer tube on the down stream side, and further specifying a pitch between heat transfer tubes in a direction rectangular to the airstream direction. CONSTITUTION:Heat transfer tubes 13a and 13b of an outer diameter D inserted in flat fins 12, aligned in parallel at a predetermined interval S, are constituted so that a plane 14 of profection of the heat transfer tube 13a located on the upstream side is partially overlapped on the heat transfer tube 13b on the downstream side. A pitch B between the heat transfer tubes 13 has relationships B>2D and (7S+D)<=B<=(18S+D). Further, fins 12 slits 16 having openings in an airstream direction 15 are provided at the upper and lower parts with respect to the base plates of flat fins 12. The leg parts of the slits 16 have an angle of inclination with respect to the airstream direction 14. In this case, as a flowpath of the airstream between heat transfer tubes 13 in a direction rectangular to the airstream direction, an aspect ratio beta satisfies the relationship of 7<='<=18, and hence lowering of the fin efficiency and increase in the draft resistance are suppressed and a parallel planar flow can be realized. Therefore, the heat transfer performance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat exchanger with fins for gas to gas-liquid two-phase fluid (or liquid), which is widely used in evaporators and condensers in the field of refrigeration and air conditioning equipment. It is related to.

2. Description of the Related Art In a conventional finned heat exchanger, as shown in FIG.
The heat exchanger tube 2 was inserted through the heat exchanger tube 2 at right angles to the heat exchanger tube 2, and the airflow 3 flowed between the fins 1 and exchanged heat with the fluid flowing inside the heat exchanger tube 2.

In recent years, there has been an increasing demand for such heat exchangers to be smaller and have higher performance.However, from the viewpoint of noise etc., it is necessary to keep the flow velocity of the airflow 3 flowing between the fins 1 low, so heat exchanger tubes are used. There was a problem in that the thermal resistance on the air side was higher than the thermal resistance on the inside.

Therefore, efforts were made to reduce the difference in thermal resistance between the air side and the inside of the tube by expanding the heat transfer area on the air side. However, expanding the heat transfer area is problematic in terms of economy, space saving, etc. Therefore, it is difficult to increase the heat transfer coefficient on the air side and reduce the thermal resistance on the air side.
This is an important issue in this type of heat exchanger.

6 and 6 show a conventional example of a heat exchanger with fins aimed at overcoming the above-mentioned problems. FIG. 5 is a plan view, and FIG. FIG. The flat plate fins 4 are provided with cut-and-raised portions 6 with openings on two sides facing the airflow between the heat transfer tubes 5 arranged in a staggered manner.

In this finned heat exchanger, a refrigerant such as fluorocarbon is circulated inside the heat exchanger tubes 5, and the heat is transmitted from the heat exchanger tubes 5 to the flat fins 4 and the raised cutouts 6 via the fin collars 7. On the other hand, the airflow 8 sent by a fan or the like passes between the flat plate fins 4, but at that time, it exchanges heat with the flat plate fins 4, cut and raised parts 6, and the surfaces of the heat exchanger tubes 5, which have different temperatures. In particular, a thin temperature boundary layer is formed in each of the cut and raised portions 6, and the so-called boundary layer front effect improves the efficiency of 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 in which the flat plate fin 4 has cut and raised parts 6, and when compared with a flat fin without processing on the fin surface, the surface thermal resistance is about 20. ~30% decrease. However, in this conventional example, since the heat transfer tubes 5 are arranged in a staggered manner, (2) ventilation resistance during air blowing becomes large. ■The dead area that occurs downstream of the heat exchanger tubes 5 becomes larger and covers part of the above cut-up group,
Effective heat transfer area is reduced. (2) The presence of the cut and raised portions 6 between the heat transfer tubes 5 in the air flow direction obstructs the movement of heat flow from the heat transfer tubes 5 and reduces fin efficiency.

Therefore, the present invention solves the above problems by devising the arrangement of heat transfer tube groups arranged in multiple rows in the airflow direction, and by devising the tube pinch and fin pitch of the heat transfer tubes in the direction perpendicular to the airflow direction. The purpose is to make the finned heat exchanger more compact and improve its performance.

Means for Solving the Problems The technical means of the present invention for solving the above problems consists of flat plate fins arranged in parallel at a constant interval S, through which gas flows, and a flat plate fin that penetrates through the flat plate fins and is configured by arranging multiple rows of heat transfer tubes with an outer diameter through which fluid flows in the airflow direction, and the heat transfer tubes are partially aligned with the downstream projection plane of any of the heat transfer tubes located on the upstream side of the airflow. Furthermore, when the tube pitch in the direction perpendicular to the airflow direction of the heat transfer tubes is B, B>2D and "≦(B-D)/
The configuration has a relationship of ≦18.

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

In other words, each heat exchanger tube partially overlaps the downstream projection plane of any heat exchanger tube located upstream of the airflow, so that the airflow is Flow can be achieved. In other words, the ventilation resistance is lower than in the case of a staggered arrangement, and the size of the dead area is smaller than in the case of a base arrangement, so that the heat transfer coefficient is improved. Also,
For a finned heat exchanger in which heat transfer tubes with outer diameters are arranged in multiple rows in the airflow direction on flat fins arranged parallel to the direction of gravity with a distance S between the fins, Fig. 5 shows B, D, S and airflow velocity. Experiments were conducted using UF as a parameter, and the same fan power Δ
These are the results of evaluating the heat transfer performance using the heat transfer coefficient α based on p, UF (ΔP: ventilation resistance of the heat exchanger).

When a group of heat transfer tubes is arranged almost parallel to the airflow direction, a dead zone occurs behind the heat transfer tubes, so the airflow path is vertical: S, horizontal:
(B-D) is considered to be a rectangular flow path.

When the distance between the fins S is knee constant, the larger the tube pitch B, that is, the larger the aspect ratio β: (B-D)/S, the closer it becomes to a parallel plate flow, and the higher the heat transfer coefficient in the flow path. However, on the contrary, the fin efficiency decreases, and as a result, the heat transfer coefficient has a maximum value with respect to the aspect ratio β. On the other hand, if the pipe pitch B is made smaller, the wind speed passing between the fins increases at the same front wind speed UF, so the ventilation resistance ΔP increases. Therefore, the same fan power ΔP”U
Aspect ratio β-10 when evaluated with F standard heat transfer coefficient α
The heat transfer performance is maximized at . Furthermore, 90% of the maximum value
The aspect ratio β is 7≦β≦18, and within this range, the heat transfer performance is excellent in practical use.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

1 and 2 show a heat exchanger according to an embodiment of the present invention, with FIG. 1 being a plan view thereof, and FIG. 2 being a YY sectional view of FIG. 3. Reference numeral 12 denotes flat fins arranged in parallel at constant intervals S. 13a and 13b are outer diameter heat exchanger tubes inserted through the flat plate fins N12, and are the heat exchanger tubes 1 on the upstream side of the airflow.
The projection surface 14 of 3d and the heat exchanger tube 13b on the downstream side are configured to partially overlap, and a refrigerant circulates inside thereof. The pitch B between the heat exchanger tubes 13 is B)2
D, and (S+D)≦B≦(1sS+D).

Further, the flat plate fin 12 is provided with cut-and-raised parts 16 having openings in the airflow direction 16 above and below the substrate of the flat-plate fin 12, and the legs of the cut-and-raised parts 16 are arranged in the airflow direction 16.
has an inclination angle relative to 4.

With this configuration, the refrigerant flowing in the heat transfer tubes 13 and the air flowing between the flat fins 12 exchange heat.

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

First, by arranging the heat exchanger tubes 13a and 13b as described above, it is possible to realize an air flow that cannot be achieved with either the υ base arrangement or the staggered arrangement.

In other words, the ventilation resistance is lower than in the case of a staggered arrangement, and
The size of the dead area is smaller than in the case of the base arrangement, so the heat transfer coefficient is improved. Furthermore, the turbulent flow is promoted by the eddy flow generated from the cut and raised legs 16 provided diagonally with respect to the air flow direction, and the flow velocity around the heat transfer tube 13 and the flow velocity passing through the cut and raised 16 are almost uniform, which makes the cut Since the leading edge effect of the boundary layer due to the risers 16 can be sufficiently exerted, the heat transfer coefficient is greatly improved.

As described above, by arranging the heat exchanger tubes 13 as in this example, the flow velocity around the heat exchanger tubes 13 and the main flow velocity between the heat exchanger tubes become almost uniform. Even in this arrangement, the flow between each heat transfer tube 13 can be considered to be within a substantially rectangular flow path. In addition, the flat plate fin 12
Even if cut and raised 16 are provided on the top, the adjacent flat fins 1
2 also has cut and raised 16, so the distance between the cut and raised 16 is also S as in the case of the flat fin.

Therefore, in this case, the heat exchanger tube 13 in the direction perpendicular to the airflow direction
The airflow path in between has an aspect ratio β of 7≦β.
Since ≦18 is satisfied, a parallel plate flow can be realized while suppressing a decrease in fin efficiency and an increase in ventilation resistance, thereby improving heat transfer performance.

Effects of the Invention As described above, the present invention arranges a plurality of fins with a distance S between the fins, connects heat exchanger tubes with an outer diameter through the fins, arranges them in multiple rows in the air flow direction, and connects the heat exchanger tubes with each other. is configured so that it partially overlaps the downstream projection plane of any of the heat exchanger tubes on the upstream side of the airflow, and furthermore, when B is the pitch between the heat exchanger tubes in the direction perpendicular to the airflow direction, B ＞2D and “≦(
Since it is a heat exchanger with fins that satisfies the relationship: B-D)/≦18, it suppresses a decrease in fin efficiency and an increase in normal resistance, and can realize parallel plate flow, which significantly improves heat transfer performance. This makes it possible to create a high-performance, compact heat exchanger with fins.

[Brief explanation of the drawing]

Figures 1 and 2 are a plan view and a sectional view of a main part of a heat exchanger with fins according to an embodiment of the present invention, Figure 3 is a performance evaluation diagram of the present invention, and Figure 4 is a fin of a conventional example. A perspective view of a heat exchanger,
5 and 6 are a plan view and a sectional view of a main part of a conventional finned heat exchanger. 12... Flat plate fin, 13... Heat exchanger tube, 14... Projection plane, 15... Air flow direction, 16... Cut and raise. Name of agent: Patent attorney Toshio Nakao Haga 1/2
−−−+2 pronged fins Figure 2 Figure 3 Anunomakt ratio p=L2Jλ−

Claims (3)

[Claims] (1) Flat plate fins arranged in parallel at a constant interval S, through which gas flows, and heat transfer tubes with an outer diameter D arranged in multiple rows in the airflow direction, through which the fluid flows through the flat plate fins. , each of the heat transfer tubes partially overlaps the downstream projection plane of any of the heat transfer tubes on the upstream side of the air flow, and further includes a tube in a direction perpendicular to the air flow direction of the heat transfer tubes. When the pitch is B, B>2D and 7≦(
A finned heat exchanger having a relationship of B-D)/S≦18. (2) The heat exchanger with fins according to claim 1, wherein a plurality of cut and raised portions opening in the airflow direction are provided in the portion of the flat fin between the heat transfer tubes. (3) The finned heat exchanger according to claim 2, wherein the cut-and-raised legs opening in the airflow direction have an inclination angle with respect to the airflow direction.