CA1326481C - Condenser - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A condenser adapted for use in the car cooling system, the condenser comprising a pair of headers provided in parallel with each other; a plurality of tubular elements whose opposite ends are connected to the headers; fins provided in the air paths between one tube and the next, wherein each of the headers is made of a cylindrical pipe of aluminum; wherein each of the tubular elements is made of a flat hollow tube of aluminum by extrusion; and wherein the opposite ends of the tubular elements are inserted into slits produced in the headers so that they are liquid-tightly brazed therein.

Description

This application is a divisional application of copending application 543,185, filed July 28, 1987 (now Canadian patent 1,301,161, issued May 19, 1992).

The present invention relates to a condenser for use as a cooler in automobiles, and more particularly to a condenser for such use, which is made of aluminum. Herein "aluminum"
includes aluminum alloys.

In ~eneral, heat exchangers, as car coolers, use a high pressure gaseous coolant, and they must have an anti-pressure construction.

To this end the known heat exchangers are provided with ` 15 a core which includes flat tubes arranged in zigzag forms, each tube having cores, and fins interposed between one tube and the next. Hereinafter this type of heat exchanger will be referred to as a serpentine type heat exchanger.

The serpentine type heat exchangers are disadvantageous in that the coolant undergoes a relatively large resistance while flowing throughout the tubes. To reduce the resistance v the common practice is to use wider tubes so as to increase the cross-sectional area thereof. However, this leads to a large core which is difficult to accommodate in the limited space in an automobile. As a result, this practice is not always effective.

Another practice i8 to place more fins by reducing the distances between the tubes. This re~uires that the height of each fin be reduced. However, when the fins are too small the bending work becomes difficult, and takes more time and labor.

In general, the condenser has a coolant path which consists of two sections, that is, an inlet section, hereinafter referred to as "condensing section" in which the coolant is still gaseous, and an outlet section, hereinafter referred to as "supercooling section" in which it becomes liquid. In order to increase the heat exchange efficiency it is essential to increase the area for effecting heat transfer in the condensing section, whereas it is no problem for the supercooling section to have a reduced area for heat transfer.

The conventional serpentine type heat exchangers have a coolant passageway which consists of a single tube. It is impossible for a single tube to be large in some parts, and small in others. If the tube is to have a wide cross-section, the tube per se must be large throuqhout its entire length: in other words a large tube must be used. This of course leads to a larger condenser.

As is evident from the foregoing description, ît is difficult to improve the conventional serpentine type heat exchangers merely by changing the dimensional factors thereof.

Basically, the serpentine type heat exchangers involve the complicated process which consists of bending tubes, and then assembling them into a core in combination with fins.
This i8 why it is difficult to produce the heat exchangers on an automatic mass production line. Non-automatic production is costly.

The present invention solves the difficulties pointed out with respect to the conventional serpentine type heat exchangers, and provides a condenser having a relatively small core which nevertheless includes a large effective cross-sectional area for coolant passageways, thereby reducing a possible resistance to the flow of coolant.
The present invention also provides a condenser having coolant passageways which are divided into a condensing ~, --2--section and a supercooling section which are different in the numbers of tubes from each other.

The present invention again provides a condenser having a core whose construction is adapted for enhancing the heat exchange efficiency.

According to the parent invention there is provided a condenæer adapted for use in a car cooling system, the condenser comprising: a pair of headers provided in parallel with each other; a plurality of tubular elements whose opposite ends are connected to the headers; fins provided in air paths present between one tube and the next; wherein each header is made of an aluminum pipe having a circular cross-section; wherein each of the tubular elements is made of aflat hollow aluminum tube made by extrusion; and wherein the opposite ends of the tubular elements are inserted in slits produced in the headers, and liquid-tightly brazed therein;
wherein the brazing substance is previously coated in the headers or the tubular elements or both; wherein at least one of the headers is internally divided by a partition into at least two groups of coolant passageways, wherein one group is located toward the inlet whereas the other is located toward the outlet, thereby enabling the flow of coolant to make at least one U-turn in the header: wherein the opposite ends of the partition are inserted in a semi-circular slit produced in the header and brazed therein: and wherein the partition i8 disc-shaped, having a larger circular portion and a smaller circular portion, the partition is inserted in the header through the slit with the larger circular portion being secured in the slit and with the smaller circular portion being kept in contact with the inside wall surface of the header.

According to the present application there is provided a condenser for liquefying gaseous coolant in an air ~ - 3 -` ` 1 326481 .:
conditioning system of an automobile after the system has compressed the coolant, said condenser comprising:
(i) a plurality of flat tubular elements defining flow paths and disposed in a spaced, substantially parallel relation, each element including at least one inside wall;
(ii) a plurality of fin members, each fin member disposed between adjacent tubular elements;
(iii) a pair of headers disposed in a spaced, - substantially parallel relation at opposite ends of the 10 tubular elements, the one and/or the other header defining a coolant inlet and a coolant outlet for the condenser, each header being an elongate member and defining, for each ~ tubular element, an opening through which it receives the .~ tubular element and establishes fluid communication with the element:
(iv) at least one partitioning plate mounted in one of the headers transversely of the header to divide the inside opening of the header;
the coolant flowing from the inlet into one header and making 20 a first pass through a plurality of the tubes to the other header, the coolant also making a final pass through a plurality of tubes to thè outlet, the tubular elements and headers forming a first zone which receives gaseous coolant from the inlet and a final zone through which the coolant flows before di~charging through the outlet, the effective cross-sectional area of the flow paths defined by the tubular elements through which the coolant makes the final pass being smaller than the effective cross-sectional area of the flow paths of those through which the coolant makes the first pass; 6aid condenser being able to resist internal pressures greater than 10 atmospheres.

Thus, the present invention adopts a multi-flow pattern .
sy6tem, whereby the coolant flows through a plurality of tubular elements at one time. The effective cross-sectional area for coolant passageways can be increased merely by increasing the number of tubular elements, thereby reducing ~.

resistance acting on the coolant. This leads to a reduction in the pressure loss of coolant.

In general, the multi-flow pattern system has difficulty in withstanding a high pressure provided by a pressurized gaseous coolant because of the relatively fragile joints between the headers and tubular elements, and the headers per se which are constructed without presupposing the high pressure which would act thereon by the coolant. In order to solve this problem encountered by the multi-flow pattern system, the condenser of the present invention uses a cylindrical pipe for the header, the flat tubes for the tubular elements, whose opposite ends are inserted in the slits produced in the headers and brazed therein, thereby ensuring that the condenser withstands a high pressure provided by the coolant.

Each of the headers is internally divided by a partition into at least two sections; that is a condensing section and a supercooling section, wherein the condensing section has a coolant in its gaseous state whereas the supercooling section has a coolant in its liquid state. When the coolant is in a gaseous state its volume is large, which requires a relatively large effective cross-sectional area for the coolant passageways. When it is in a liquid state the volume is reduced, thereby allowing the coolant passageway to have a relatively small cross-sectional area.

According to a preferred embodiment of the present invention there are provided dimensional relationships among the width, height and pitch of the tubular elements and fins as follows: Width of the tubular element: 6 to 12 mm;
Height of the tubular element: 5 mm or less; Height of each fin: 8 to 16 mm; Fin pitch: 1.6 to 3.2 mm.
The tubular elements are jointed to the headers; more specifically, the opposite ends of each tubular element are ~ _ 5 _ inserted into slits produced in the headers so that they fit therein in a liquid-tight manner and then they are brazed therein. Prior to the insertion, the tubular elements or the headers or both are provided with a layer of a brazing S substance. All the brazing is effected at one time by placing the assembled unit in a furnace, thereby saving time and labor in the assembling work. Suitably, the headers are made of an electrically seamed clad metal pipe having its inner surface coated with a brazing substance. Desirably, the coolant passageways have effective cross-sectional areas which are progressively reduced from the inlet side to the outlet side. Suitably, each tubular element is provided with stop means whereby the tubular element is prevented from being inserted through the semi-circular slit of the header.
Preferably, each tubular element has a body and a head with a shoulder interposed therebetween, and wherein the stop means is provided by the shoulder. Desirably, the stop means are provided by bulged portions left after the corners of each tubular element are cut out. Suitably, the tubular elements have different lengths, and are grouped with respect to their lengths, and wherein at least one of the headers is divided into two small headers so as to enable one of the small headers to accept the shorter tubular elements, thereby forming a space void of tub~lar elements.
The present invention will be further illustrated by way of the accompanying drawings, in which:

Fig. l is a front view showing a condenser embodying the present invention;

Fig. 2 is a plan view showing the condenser of Fig. l;

Fig. 3 is a perspective view showing the joint between the header and the individual tubes;

Fig. 4 is a cross-sectional view through the line 4-4 in Fig. 1, Fig. 5 is a cross-sectional view showing the joint between the header and the tube;

Fig. 6 is a cross-sectional view of the tube exemplifying its dimensional relationship;

Fig. 7 is a cross-sectional view of the fin exemplifying its dimensional relationship;

Fig. 8 is an explanatory view showing a flow pattern of coolant;
Fig. 9 is a perspective view showing a modified version of the joint between the tubes and the header;

Fig. 10 is a cross-sectional view showing the relationship between the tube and the header after they are jointed to each other;

Fig. 11 is a cross-sectional view showing a modified version of the stopper produced in the tube;
Fig. 12 is a cross-sectional view showing another modified version of the stopper;

Fig. 13 is a cross-sectional view showing a further modified version of the stopper;

Fig. 14 is a front view showing a modified version of the condenser;

Fig. 15 is a graph showing the relationship between the width of the tubes and the rate of air passage therethrough;

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Fig. 16 is a graph showing the relationship between the height of the tubes and the pressure loss of air; and Fig. 17 is a graph showing variations in the heat exchange efficiency with respect to the height of the fins and the pressure loss of air.

As shown in Fig. 1, the condenser lo of the prese~t invention includes a plurality of planar tubes 11, and corrugated fins 12 alternately arranged. The tubes 11 are connected to headers 13 and 14 at their opposite ends.

The tube 11 is planar, made of aluminum, and preferably, of a multi-hollow type.
The headers 13, 14 are made of a cylindrical pipe of aluminum. They are provided with slits 15 (see Fig. 3) produced at equal intervals along their lengths, where the ends of the tubes 11 are brazed to the respective headers 13, 14. The left-hand header 13 is provided with a coolant inlet pipe 16 at its upper end and a plug 17 at the lower end. The right-hand header 14 is provided with a coolant outlet pipe 18 at its lower end and a plug 19 at its upper end. The coolant inlet and outlet are diametrically located. The reference numerals 23 and 24 denote side plates fixed to the fins 12 located at the outermost positions.

Each header 13, 14 is provided with a partition 20, 21, respectively, thereby dividing the internal chamber into upper and lower sections, wherein the partition 20 in the header 13 is located slightly toward the inlet 16, whereas the partition 21 in the header 14 is located about 1/3 the length toward the outlet 18.

Because of the provision of the partitions 20 and 21 in the headers 13 and 14, the flow pattern of the coolant is formed as shown in Fig. 8; that is, the coolant passageway is ~' - 8 -grouped into an inlet section (A), a middle section (B) and an outlet section (C). As seen from Fig. 8, the coolant flows in three different directions. In addition, the tubes are different in number from group to group; that i6, group (B) has more tubes than the group (C) (outlet section), and group (A) (inlet section) has more tubes than group (B).
This means that group (A) has a larger effective cross-sectional area for coolant passageway than group (B), which in turn has a greater area for it than qroup (C).
Referring to Fig. 8, the coolant introduced into the core through the inlet pipe 16 flows to the right-hand header 14 in the inlet section (A), and then in a reversed direction in the middle section (B). In the outlet section (C) the flow coolant is again reversed, and led to the right-hand header 14, where it is discharged through the outlet pipe 18.
While the coolant is flowing through the sections (A), (B) and (C) heat exchange takes place between the coolant and the air passing through the fins 12. In the inlet section (A) the coolant is in its gaseous state, but because of the large effective cross-sectional area in section (A) heat exchange proceeds efficiently between the coolant and the air. In section (C) the coolant is in its liquid state, and reduced in its volume, which allows section (C) to have a relatively small cross-sectional area for coolant passageway as compared with section (B). In this way the coolant passes through the first condensing section (A~, the second section (B) and the third supercooling section (C), in the course of which heat ~ exchange smoothly and efficiently takes place.

In the illustrated embodiment, the numbers of tubes are progressively decreased from section (A) to section (B) and to section (C). However, it is possible to have the same number of tubes in sections (A) and (B), and a smaller number of tubes in section (C). Alternatively, it is possible to arrange each section (A) to (C) to have the same number of tubes, but their cross-sectional areas are progressively f _ g _ ~,"

reduced from section (A) to section (B) and to section (C).
As a further modification, the intermediate section (B) can be omitted; in this case the flow pattern is called a two-path system. In contrast, the above-mentioned embodiment i8 S called a three-path system. As a still further modification, one or more intermediate sections can be added.

The illustrated embodiment has the headers located at the left-hand side and the right-hand side, but they can be located at the upper side and the lower side, wherein the tubes and fins are vertically arranged.

To joint the tubes 11 to the headers 13~ 14 the tubes or the headers or both are previously provided with a lS layer of brazing substance on their adjoining surfaces. More specifically, as shown in Fig. 3 there is provided an aluminum pipe 13a, such as a clad metal pipe, which is used as the headers 13 and 14. The clad pipe 13a has a layer of a brazing substance 13b. The pipe 13a is electrically seamed but can be made by extrusion or any other known method. For the brazing substance an Al-Si alloy, preferably containing 6 to 13% by weight of Si, is used. The tubes 11 are inserted in the slits lS for their end portions to be held therein.
Then they are heated together to melt the brazing substance.
In this case, as clearly shown in Fig. 5 the adjoining parts of the tube 11 and the clad pipe 13a have fillets 29, whereby the headers 13, 14 and the tubes 11 are jointed to each other without gaps interposed therebetween. Likewise, the corrugated fins 12 can be provided with a layer of the brazing substance, thereby effecting the brazing joint between the fins 12 and the tubes 11 simultaneously when the tubes 11 are jointed to the headers 13, 14. This facilitates the brazing joint among the headers 13, 14, the tubes 11 and the fins 12, thereby saving labor and time in the assembling work. ~he layer of the brazing substance can be provided in the inner surface of the clad pipe 13a but the place is not limited to it.

~G9~ - lo The partitions 20, 21 are jointed to the respective headers 13, 14 in the following manner:

The clad pipe 13a is previously provided with a semi-circular slit 28 in its wall, wherein the slit 28 covers halfthe circumference of the pipe 13a. The partitions 20, 21 are made of a disc-shaped plate having a smaller circular portion 20a and a larger circular portion 20b, wherein the smaller circular portion 2Oa has a diameter equal to the inside diameter of the pipe 13a, and wherein the larger circular portion 20b has a diameter equal to the outside diameter of the pipe 13a. The larger diameter portion 20b is inserted and brazed in the slit 28. The headers 13, 14 and the partitions 20, 21 are preferably provided with layers of brazing substances as described above, so that the brazing joint between them can be performed simultaneously when the tubes 11 are soldered to the headers 13, 14. This finishes the brazing joints among the headers, the tubes, the fins and the partitions at one time. The larger diameter portion 20b fits in the slit 28 so that no leakage of coolant is likely to occur, and the appearance of the outer surface of the pipe 13a is maintained. In addition, the larger diameter portion 20b is embedded in the slit 28, thereby preventing the partitions 20, 21 from being displaced by an unexpected force acting thereon.

As is generally known in the art, a possible pressure loss of air largely depends on the relative positional relationship between the tubes 11 and the fins 12. A reduced pressure loss leads to an increased heat exchange efficiency.
Accordingly, the heat exchange efficiency depends on this positional relationship. Now, referring to Figs. 6 and 7 this positional relationship will be described:

It is prescribed that the tube 11 has a width (W~ of 6 to 12 mm, and a height (Ht) of not larger than 5 mm, and that the fin 12 has a height (Hf) of 8 to 16 mm, and a fin pitch ~.~ ., -- 1 1 --.

(Fp) of 1.6 to 3.2 mm. Referring to Figs. 15, 16 and 17 the reasons for the prescriptions are as follows:

As shown in Fig. 15, if the tube 11 has a width of smaller than 6 mm the fin 12 will be accordingly narrower, thereby reducing the number of louvers 12a. The reduced number of louvers 12a leads to less efficient heat exchange.
If the tube is wide enough to allow an adequate number of louvers 12a to be provided on the fins 12, the heat exchange efficiency will be enhanced. However, if the width (W) of the tube is more than 12 mm, the fins 12 will be accordingly widened, thereby increasing its weight. In addition too wide fins and too many louvers are likely to increase resistance to the air passing therethrough, thereby causing a greater pressure loss of air.

If the tu~es ll have a height (Ht) of more than 5 mm the pressure loss of air will increase. The inside height (Hp) of the tube 11 is preferably not smaller than 1.8 mm. The inside height (Hp) is important in that it defines the size of an effective coolant passageway. If it is smaller than 1.8 mm the pressure loss of coolant will increase, thereby reducing the heat exchange efficiency. In order to maintain a height (Hp) of at least 1.8 mm for the coolant passageway, the height (Ht) of the tube ll will have to be at least 2.5 mm, inclusive of the thickness of the tube wall.

As shown in Fig. 17, if the height (Hf) of the fin 12 is smaller than 8 mm the pressure loss of air will i~crease, but if it is larger than 16 mm the number of fins will have to be reduced, thereby reducing the heat exchange efficiency.

If the pitch (Fp) of fins 12 is smaller than 1.6 mm there will occur an intexference between the adjacent louvers ~2a, thereby amplifying the preæsure loss of air. However, if it exceeds 3.2 mm the heat exchange efficiency will decrease.

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Referring to Figs. 9 and 10 a modified version will be described.

This embodiment is characterized in that it is provided with shoulders 25 which work as stop means to prevent the tube from being inserted too deeply into the headers 13, 14.
More specifically, the tube 11 includes a body 111 and a head llla which has shoulders 25 therebetween. The shoulders 25 are adapted to come into abutment with the headers 13, 14 when the tube 11 is inserted into the slit 15.

As modified versions of the stop means various examples are shown in Figs. 11 to 13:

Fig. 11 shows the process of forming stop means 125. In (a) the tube 211 has sharp or acute corners. The corners are cut away in such a manner as to form bulged portions 125, which provide stop means. Fig. 12 shows a tube 311 having round corners, which are split lengthwise in such a manner as to form shoulders 225. Fig. 13 shows a tube 411 having a relatively thin wall. In this case the cutting and splitting are jointly used in such a manner as to form shoulders 325.

Fig. 14 shows an example of the condenser embodying the present invention, characterized in that the condenser is provided with a space 27 void of any tube or fin so that an obstacle 26 is avoided when it is installed in an engine compartment or elsewhere. This embodiment has a pair of headers 113 and 14, and the left-hand header 113 is divided into two parts 113a and 113b. The tubes 11 consist of longer tubes lla and shorter tubes llb, which are connected to the header 113b at their left-hand ends. The other ends thereof are connected to the header 14. The outlet pipe 18 i8 provided on the header 113b. The coolant introduced through the inlet pipe 16 flows in the direction of the arrows up to the right-hand header 14, and makes a U-turn to flow through the shorter tubes llb up to the header 113b, where it is let . .

i 1326481 out through the outlet pipe 18. The number of the space 27 is determined in accordance with that of the obstacle 26;
when three spaces are to be provided, three different lengths of tubes are used.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A condenser for liquefying gaseous coolant in an air conditioning system of an automobile after the system has compressed the coolant, said condenser comprising:
(i) a plurality of flat tubular elements defining flow paths and disposed in a spaced, substantially parallel relation, each element including at least one inside wall;
(ii) a plurality of fin members, each fin member disposed between adjacent tubular elements;
(iii) a pair of headers disposed in a spaced, substantially parallel relation at opposite ends of the tubular elements, the one and/or the other header defining a coolant inlet and a coolant outlet for the condenser, each header being an elongate member and defining, for each tubular element, an opening through which it receives the tubular element and establishes fluid communication with the element;
(iv) at least one partitioning plate mounted in one of the headers transversely of the header to divide the inside opening of the header;
the coolant flowing from the inlet into one header and making a first pass through a plurality of the tubes to the other header, the coolant also making a final pass through a plurality of tubes to the outlet, the tubular elements and headers forming a first zone which receives gaseous coolant from the inlet and a final zone through which the coolant flows before discharging through the outlet, the effective cross-sectional area of the flow paths defined by the tubular elements through which the coolant makes the final pass being smaller than the effective cross-sectional area of the flow paths of those through which the coolant makes the first pass; said condenser being able to resist internal pressures greater than 10 atmospheres.

2. A condenser of claim 1, wherein the partitioning plate is mounted in the header, and the partitioning plate includes a first portion which extends into a slit in the header and a second portion which is generally co-extensive with the inside opening of the header.

3. The condenser of claim 1, in which one header defines the inlet and outlet and includes the partitioning plate.

4. The condenser of claim 1, in which each header has at least one partition and wherein the coolant makes a second pass between the first and the final passes through a plurality of tubular elements.

5. A condenser as defined in claim 4, wherein the effective cross-sectional area of the coolant passageways formed through the tubular elements is reduced stepwise from the first pass, to the second pass, to the final pass.

6. A condenser as defined in claim 5, wherein the number of the tubular elements is reduced stepwise from the first pass towards the final pass.

7. A condenser as defined in claim 1, wherein each header is a clad pipe having either one or both of its surfaces coated with a brazing agent layer.

8. A condenser as defined in claim 1, wherein each header is a seam-welded pipe.

9. A condenser as defined in claim 1, wherein the partitioning plate is a disc which has a large diameter portion and a small diameter portion.

10. A condenser as defined in claim 1, wherein the tubular elements are extruded, elongate members.