JP2690234B2 - Heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger that functions as an evaporator in an air conditioner that constitutes a refrigeration cycle.

[0002]

2. Description of the Related Art Conventionally, it has been emphasized that the uniformity of the split flow of the refrigerant is important when the refrigerant flow paths of the evaporator of the air conditioner are plural. As one of the refrigerant distribution systems, there is a header system. An example of a conventional heat exchanger will be described below with reference to the drawings. FIG. 4 is a schematic view of a conventional heat exchanger. The heat exchanger is composed of a heat transfer tube group 1, a fin group 2 inserted into the heat transfer tube group 1, and a plurality of headers 3 into which both ends of the heat transfer tube group 1 are inserted to form a refrigerant flow path. The plurality of headers 3 are 3a, 3 from the upstream side in the refrigerant flow direction.
b, 3c, 3d and 3e. Also, the header 3a
The refrigerant flowing in from flows through the header 3e as shown by the arrow 4.
Spill out of. At that time, heat is exchanged with the air flowing between the fin groups 2 to evaporate.

[0003]

However, in the case of header division, the following problems occur.

FIG. 5 is an explanatory view showing the flow state of the refrigerant in the header. The refrigerant 5 flowing into the header 3 from the inflow heat transfer tube group 1A rises in the header 3 and flows out of the outflow heat transfer tube group 1B.
Spill out of. At that time, in the case of a gas-liquid two-phase flow having a large liquid phase ratio and a low degree of dryness, a so-called floss flow in which a discontinuous gas phase exists in a continuous liquid phase is formed and flows while being stirred, The gas / liquid phase ratio is evenly distributed to the outflow heat transfer tube group 1B. However, the refrigerant that continues to evaporate gradually becomes a gas-liquid two-phase flow in which the liquid phase ratio is small and the dryness is large, and the gas phase velocity increases. When such a refrigerant flows into the header, the liquid phase forms a so-called annular flow in which the gas phase flows in the header wall surface and the gas phase flows in the central portion, collides with the header upper surface portion 31, is stirred, and flows out from the heat transfer tube group 1B. leak. Therefore, the outflow heat transfer tube near the header upper surface portion 31 has a larger circulation amount, and the outflow heat transfer tube separated from the header upper surface portion 31 has a smaller circulation amount.

The refrigerant in the heat transfer tube, which has a small circulation amount, evaporates completely on the way, and thereafter, the gas phase only exchanges sensible heat. To some extent, such a phenomenon occurs not only in the header near the outlet of the heat exchanger but also in the header in the middle. Then, the temperature inside the heat transfer tube gradually rises above the dew point temperature of the inflowing air, and it becomes difficult for dew condensation to occur on the fin surface. Therefore, the inflow air tends to flow between the fins in which dew condensation does not occur, rather than between the fins in which dew condensation occurs and the ventilation resistance is large, and a wind velocity distribution is generated. As a result, a heat transfer tube with a smaller circulation amount exchanges heat more vigorously and evaporates violently.

[0006] Once the divergence becomes uneven in this way, the degree of unevenness tends to increase,
As a result, there is a problem that the effective heat transfer area where the refrigerant actually evaporates is reduced.

In view of the above-mentioned conventional problems, the present invention aims to improve the performance by dividing the refrigerant evenly and increasing the effective heat transfer area where the refrigerant actually evaporates.

[0008]

In order to solve the above-mentioned problems, the present invention provides a fin group through which air flows, a heat transfer tube group through which a refrigerant flows inside the fin group, and both ends of the heat transfer tube group are inserted. And is composed of a plurality of headers forming a flow path, of the header in the direction perpendicular to the flow direction of the refrigerant .
Cross-sectional area sequentially from the upstream header to the downstream header
Those were the size comb.

[0009] The present invention, the opening area of the aperture provided between the inlet heat transfer tubes that are inserted into the header and outlet heat transfer tubes,
The size is increased from the upstream header to the downstream header.

Further, according to the present invention, the end opening surface of the heat transfer tube group on the side flowing out of the header is inclined with respect to the header axis, and the inclination angle with respect to the header axis is sequentially changed from the lowermost heat transfer tube to the uppermost heat transfer tube. It is a small one.

[0011]

The operation of the above means is as follows.

[0012] In the vertical direction to the flow direction of the refrigerant,
The cross-section area of the header is from the upstream header to the downstream header
By sequentially increased to over, when the refrigerant flows in the header, header rate of the refrigerant, since successively slower from the upstream side of the header to the downstream side of the header, uniformly to the heat transfer tubes refrigerant in each header The effective heat transfer area that splits and actually evaporates increases, and the capacity as an evaporator can be maximized.

[0013] The present invention, the opening area of the aperture provided between the inlet heat transfer tubes that are inserted into the header outlet heat transfer tubes, by sequentially increased toward the downstream side of the header from the upstream side of the header, each header It is possible to uniformly divide the refrigerant into the heat transfer tubes and increase the effective heat transfer area where the refrigerant actually evaporates.

Further, according to the present invention, the end opening surface of the heat transfer tube group on the side flowing out of the header is inclined with respect to the header axis, and the inclination angle with respect to the header axis is sequentially changed from the lowermost heat transfer tube to the uppermost heat transfer tube. By making it small, the refrigerant can be uniformly divided into the heat transfer tubes, and the effective heat transfer area where the refrigerant actually evaporates can be increased.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIG. The same parts as those in the conventional example are designated by the same reference numerals.

In the figure, the heat exchanger comprises a heat transfer tube group 1, a fin group 2 and a header group 3 inserted in the heat transfer tube group 1.
The header group 3 is 3a, 3b, 3c, 3d and 3e from the upstream side in the refrigerant flow direction.
An inflow heat transfer tube group 1A and an outflow heat transfer tube group 1B are inserted in each header to form a flow path. The header diameters Da, Db, Dc, Dd and De of the header groups 3a to 3e have a relationship of Da <Db <Dc <Dd <De. The refrigerant flows in from the header 3a, flows in the heat transfer tube group and the header group, and flows out from the header 3e.

Generally, in an air conditioner, the refrigerant has a dryness of 0.
It flows into the evaporator in a state where the ratio of the liquid phase is about 2 is large.
Therefore, in the header 3b, a froth flow in which a discontinuous gas phase is present in the continuous liquid phase is formed and flows while being stirred, so that the outflow heat transfer tube group has a relatively uniform gas / liquid phase ratio. Divided into 2B. The dryness of the refrigerant that exchanges heat with air and continues to evaporate gradually increases. Therefore, the gas phase velocity is increased and an annular flow is easily formed in the header. Generally, the flow state of a gas-liquid two-phase flow in an unheated vertical tube is related to the Froude number Fr = (Vl2 + Vg2) / D / g Vl: liquid phase velocity, Vg: gas phase velocity D: pipe diameter, g: gravity acceleration However, the larger the Froude number, the easier the transition to the annular flow. However, since the header diameter gradually increases from the upstream side, the liquid-phase velocity decreases and the vapor-phase velocity increases. Therefore, the increase in the Froude number in each header can be suppressed, and the transition to the annular flow becomes difficult. Therefore, the refrigerant collides with the upper surface of each header, and is uniformly split into the outflow heat transfer tubes near the upper surface without being biased. Therefore, it is possible to partially evaporate in the middle of the heat transfer tubes and to perform the same degree of evaporation in all the heat transfer tubes, increasing the effective heat transfer area where the refrigerant actually evaporates and improving the performance. It will be possible.

Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the figure, each header 3b, 3c, 3d
In the inside, there are throttles 7b, 7c and 7d provided between the inflow heat transfer tube group 1A and the outflow heat transfer tube group 1B.
b, dc, and dd have a relationship of db <dc <dd.

The refrigerant flowing into the header 3a exchanges heat with air, flows into the header 3b via the inflow heat transfer tube 1A, passes through the restrictor 7b, and is split into the outflow heat transfer tube 1B.
At this time, the refrigerant having a low degree of dryness and a large liquid phase ratio has a low speed but is accelerated to some extent by the throttle 7b, so that the refrigerant sufficiently reaches the upper heat transfer tube 1B and is evenly divided. The dryness of the refrigerant that exchanges heat with air and continues to evaporate gradually increases. The refrigerant flowing into the headers 3c and 3d in the state where the gas phase ratio is high and the gas phase velocity is high,
After passing through the throttles 7c and 7d, the heat is split into the outflow heat transfer tube 1B. However, since the aperture diameters dc and dd are larger than db, the acceleration of the velocity due to passage through the aperture is sequentially suppressed.
Therefore, the transition to the annular flow becomes difficult. Therefore, the refrigerant uniformly splits without colliding with the upper surface portion of each header and non-uniformly flowing to the outflow heat transfer tubes near the upper surface portion. Next, according to FIG.
A third embodiment of the present invention will be described.

In the figure, the end opening surface of the heat transfer tube group 1B flowing out of the header 3 is inclined with respect to the axial direction of the header, and the inclination angles θa, θb, θc and θd are θa>θb>θc> θd. Have a relationship. The refrigerant flowing in from the inflow heat transfer tube 1A flows out from the outflow heat transfer tube 1B. At this time, the refrigerant collides with the upper surface of the header and is agitated, so that the refrigerant is lopsided in the outflow heat transfer tube near the upper surface 31 of the header.
However, the end opening surface of the outflow heat transfer tube group 1B is inclined with respect to the header axial direction, and the lowermost heat transfer tube has the largest inclination angle, that is, the opening is large in the refrigerant flow direction. Therefore, it is possible to satisfactorily divert the heat to the outflowing heat transfer tube distant from the upper surface of the header and to divert it uniformly.

Although the present embodiment has been described by using a plurality of independent headers, it goes without saying that the same effect can be obtained with a header which is integrally separated by a partition wall.

[0024]

As is apparent from the above embodiment, the present invention is based on the sectional area of the header in the direction perpendicular to the flow direction.
From the upstream header to the downstream header
By doing so, when the refrigerant flows in the header, the speed in the header of the refrigerant can be gradually decreased from the header on the upstream side to the header on the downstream side, so that in each header, the refrigerant is actually evenly divided into each heat transfer tube. The effective heat transfer area for evaporation is increased, and the capacity of the evaporator can be maximized.

Moreover, by the opening area of the aperture provided between the inlet heat transfer tubes that are inserted into the header and outlet heat transfer tubes, is sequentially increased from an upstream side of the header to the downstream side of the header, the refrigerant is each header top Uneven flow in the heat transfer tube
It is possible to uniformly divide the heat transfer tubes into each heat transfer tube and increase the effective heat transfer area that actually evaporates.

Further, the end opening surface of the heat transfer tube group on the side flowing out of the header is inclined with respect to the header axis, and the inclination angle with respect to the header axis is gradually reduced from the lowermost heat transfer tube to the uppermost heat transfer tube. Accordingly, the refrigerant header top
It is possible to satisfactorily divide the flow into the outflow heat transfer tube distant from the portion, and increase the effective heat transfer area that actually evaporates.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a heat exchanger of the present invention.

FIG. 2 is a sectional view of an essential part showing a second embodiment of the heat exchanger of the present invention.

FIG. 3 is a cross-sectional view of essential parts showing a third embodiment of the heat exchanger of the present invention.

FIG. 4 is a configuration diagram showing a conventional example.

FIG. 5 is a sectional view of the main part of the same.

[Explanation of Codes] 1 heat transfer tube group 1A inflow heat transfer tube group 2B outflow heat transfer tube group 2 fin groups 3, 3a, 3b, 3c, 3d, 3e header group Da, Db, Dc, Dd, De header diameters 7a, 7b, 7c, 7d, 7e Aperture da, db, dc, dd, de Aperture diameter θa, θb , θc, θd Inclination angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Nakayama 3-22 Takada Hondori, Higashi-Osaka City, Osaka Prefecture Matsushita Refrigeration Co., Ltd. (72) Teruhiko Hira 3-22 Takaida Hondori, Higashi-Osaka City, Osaka Prefecture Matsushita Refrigerator Co., Ltd. (56) Reference JP-A-3-177761 (JP, A) Actual development Sho 53-133260 (JP, U)

Claims (3)

(57) [Claims] 1. A fin group in which air flows, a heat transfer tube group inserted in the fin group and in which a refrigerant flows, and both ends of the heat transfer tube group are inserted to form a flow path from a plurality of headers. The vertical direction to the flow direction of the refrigerant.
Change the header cross section from the upstream header to the downstream head.
Sequentially magnitude Kushida heat exchanger Zehnder. 2. A fin group in which air flows, and the fin group
And a heat transfer tube group in which the refrigerant flows,
Multiple headers that insert both ends of the heat tube group and form flow paths
And a heat exchanger in which the opening area of the throttle provided between the inflow heat transfer tube and the outflow heat transfer tube inserted in the header is sequentially increased from the upstream header to the downstream header. 3. A fin group in which air flows and the fin group
And a heat transfer tube group in which the refrigerant flows,
Multiple headers that insert both ends of the heat tube group and form flow paths
It consists, tilting the end opening of the tube bank of the side that flows out of the header relative to the header axis and the inclination angle with respect to the header axis from bottom of the heat transfer tubes gradually decrease to the top of the heat transfer tube heat Exchanger.