DE9218615U1 - Full-rib evaporator core - Google Patents

Description

PCT/CA92/00512

VOILFIN EVAPORATOR CORE TECHNICAL FIELD

The present invention relates generally to plate heat exchangers for vehicle applications.

STATE OF THE ART

Common heat exchangers for use in vehicles for applications such as air conditioning are already known and are usually flat plate heat exchangers. These flat plate heat exchangers or evaporators as they are sometimes called, are constructed with alternating and laterally adjacent extending liquid and air flow passages. The cooling liquid passages are provided with a number of liquid flow obstructions arranged therein and are formed by permanently connecting pairs of elongated plates with recesses arranged therein. The number of liquid flow obstructions thus formed causes a tortuous flow path in the liquid flow passages to create turbulence and to increase the contact surface area between the walls of the passage and the cooling liquid to increase the efficiency of heat exchange from the air to the liquid.

DISCLOSURE OF THE INVENTION

In one type of evaporator, the inlet and outlet ports for the cooling liquid are located adjacent the ends of the elongated plates, as in U.S. Patent Nos. 4,470,455 (Sacca) and 4,600,053 (Patel et al.). These ports are formed from raised areas, sometimes called cups, located adjacent the end portions of each plate. The raised areas are generally circular and have a lip portion at the bottom of the cup, the edge of which has a

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opening in the bottom of the cup. When the pairs of elongated plates are joined together, the cups of each plate of the pair are in register with each other and form either a liquid inlet or outlet passageway therethrough. The liquid entering the inlet enters the lateral liquid passageways between the plates via inlets located in these opposing cup sections,

The evaporator is assembled by joining a number of these mated plate pairs together. The plate pairs are coupled together around the lips on the bottoms of the bowls and a tight seal is created by soldering. In this way, a multi-plate structure is assembled. An airflow passage is created between adjacent mated plate pairs by arranging a fin with a large surface area for effective heat exchange.

In another type of evaporator, the inlet and outlet containers containing the liquid connections are located adjacent to each other and at one end of the evaporator, as shown in U.S. Patent No. 4,696,342 (Yamauchi et al.) and U.S. Patent No. 4,723,601 (Ohara et al.).

A disadvantage of these common evaporator designs is a loss of efficiency due to the fact that the entire front area of the evaporators is not utilized because the coolant inlet and outlet reservoir areas containing the liquid passages are located along its entire width on one or both sides. The area occupied by the reservoir areas precludes the presence of fins, resulting in a fin area/pipe area ratio that is significantly less than one, typically ranging between 0.70 and 0.80.

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Another disadvantage of these evaporators using the above deep drawn cup design is the need for strength and accuracy testing when positioning the two plates relative to each other during assembly, since a good seal between the lip areas of adjacent cups is required for proper operation of the evaporator. Furthermore, these large surface area types with self-supporting joints have low burst strength and are prone to breakage. This is becoming an increasingly significant problem as common air conditioning refrigerants containing chlorine, e.g. R-12, are replaced by more environmentally friendly ones. Some of these, e.g. R-134, operate at higher vapor pressures than common refrigerants, and therefore heat exchangers using these alternative refrigerants require greater burst strength.

Previous prior art heat exchanger designs include long, small diameter tubes passing through a flat finned area, with the tubes passing through the fins multiple times in parallel, thus providing the entire front area for air flow. A disadvantage of this design is the relatively small surface area that the hot fluid comes into contact with as it flows through the heat exchanger, since the fluid can only flow through the tubes.

Another disadvantage of some prior art air conditioning evaporators relates to the residence time of the coolant in various areas of the evaporator. It has been found that the flow rate of the coolant in some areas of the prior art evaporators is reduced compared to other areas, creating dead zones or spots. The coolant undergoes chemical analysis under operating conditions in the vicinity of the evaporator outlet ports, which results in the formation of strong acids such as hydrochloric and fluoric acids.

hydrogen acid. These acids are known to cause corrosion of solder joints and cause small leaks in the dead zones.

The present invention provides a full-fin plate heat exchanger. In accordance with one aspect of the invention, the full-fin heat exchanger includes a number of coupled plate pairs, each plate of the pair having a substantially planar portion, and the plates of each pair being sealably coupled together, the planar portions being spaced apart from one another to thereby enclose a longitudinal flow passage disposed therebetween and to provide spaces between adjacent plate pairs defining lateral air passages. The plates are each provided with at least two through-openings spaced from the side edges of the plate. Each opening in one plate is substantially in register with an opening in the other plate of the pair. The plates are formed with tubes laterally surrounding each opening and extending transversely from the plates. The plurality of plate pairs are stacked in spaced relationship with each tube extending from a plate pair being in register with a tube extending from an adjacent plate pair to form a sealable coupling, the coupling having an overlap region overlapping a region of at least one of the tubes. The connected tubes substantially surround transverse flow passages, wherein said transverse flow passages are spaced from each other and in flow communication with the lateral flow passages. Means are provided defining an inlet port in flow communication with one of the transverse passages and means defining an outlet port in flow communication with another of the transverse passages. The transverse passages have end portions and means for sealing the end portions not in contact with the inlet and

Outlet ports are in flow communication. In addition, fins are arranged in the side air passages, which are in thermal contact with the plates and have transverse fluid passages extending through them.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative embodiments of both the heat exchanger and methods of manufacturing components thereof will now be described by way of example with reference to the accompanying drawings:

Figure 1 is a front view of a preferred embodiment of a heat exchanger according to the present invention;

Figure 2 is a perspective cross-sectional view of the heat exchanger of Figure 1;

Figure 3 is a front view, partially in cross section, of another embodiment of a heat exchanger according to the present invention;

Figure 4 is an exploded perspective view of a pair of plates forming a plate pair of the heat exchanger;

Figure 4a is a perspective, partially exploded view, similar to Figure 4, of another embodiment of the heat exchanger plate;
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Figure 5 is an enlarged front view of a portion of a plate pair in cross section;

Figure 6 is an enlarged cross-sectional view of a portion of a pair of plates showing details of the alignment mechanism for the plates;

Figure 7 illustrates another method of coupling the tubes or pipes of adjacent plate pairs;

Figures 8a to 8d are cross-sectional views illustrating the process steps of drilling and expanding a plate to form the tubes therein;

Figures 9a to 9g are cross-sectional views illustrating another method of forming the tubes by a deep drawing and piercing operation;

Figures 10a, 10b and 10c show preferred embodiments of the fin that can be used in the heat exchanger; and

Figure 11 shows the details of the coupling connection between the inlet and outlet passages for the liquid and the related hose coupling.

PREFERRED EMBODIMENT OF THE INVENTION 20

The structure and operation of the full-fin evaporator of the present invention will now be described, with like reference numerals being used throughout to designate similar parts of different embodiments of the heat exchanger.

Referring to Figures 1 and 2, a full fin evaporator or heat exchanger is generally designated by the reference numeral 10 and comprises a number of elongated plates 12 arranged in adjacent pairs 18, each pair comprising an upper plate 14 and a lower plate 16 sealed to each other to form a flow passage 20 for the coolant therebetween. A number of such plate pairs 18 are coupled in a manner described below to form part of the heat exchanger 10. Air passages 22 are formed between adjacent plate pairs 18.

and ribs 24 are arranged in the air passages 22, the ribs 24 being in thermal contact with adjacent plate pairs 18 in order to create a large surface area for the heat exchange between the ribs 24 and the air flowing through the air passages 22.

The heat exchanger 10 includes an inlet port 26 and an outlet port 28 for the cooling liquid extending from the top of the heat exchanger 10. The ports 26 and 28 are spaced inwardly from the end or edge portions 30 of the heat exchanger 10. The heat exchanger 10 is provided with an upper protective plate 32 through which the ports 26 and 28 can protrude. The plate 32 is adjacent to the uppermost pair of plates to protect the uppermost fin 24 from damage. The evaporator IO also includes a lower protective plate 34 to protect the lowermost fin 24 from damage and also to provide support for the evaporator IO.

Figure 2 shows the heat exchanger 10 provided with a cooling liquid inlet passage 36 communicating with the inlet port 26 and a liquid outlet passage 37 communicating with the outlet port 28. The passages 36, 37 extend transversely through the plate pairs 18 and the fins 24 through the interior of the heat exchanger 10.

Figure 3 shows another embodiment of a heat exchanger, generally designated by the reference numeral 40 and similar to heat exchanger 10 except that an inlet port 26' and an outlet port 28' are located on the same side of heat exchanger 40, but adjacent to respective lower and upper plates 34, 32. An extension tube 41 connects outlet port 28' to transverse flow passage 36', and another extension tube 44 connects inlet port 26' to transverse flow passage 37'. In the liquid inlet and

-outlet passages 37' and 36' are provided with plugs 42 and 43. The function of the plugs 42, 43 is described here.

The details of the construction and manufacture of various embodiments of plates 12 and passages 36 and 37 will now be described with reference to Figures 4 to 8.

Referring to the exploded perspective view of Figure 4, a pair of plates 18 includes an upper plate 14 and a lower plate 16. The plates 14 and 16 are identical and therefore the following description applies equally to both plates. The plates 14, 16 include a central planar region 56 and are provided with a number of recesses 58 evenly distributed throughout each plate. Each plate includes a pair of spaced apart openings 60 ₇ spaced inwardly from the side edges 62 of the plates. Tubes or pipes 64 and 66 are integrally formed about or sealably attached to the side edges of the associated openings 60 and extend transversely from the plates in the opposite direction to the recesses 58. The plates include a raised edge region 68 adjacent the side edge 62 as best seen in the lower half of Figure 4. The recesses 58 and the raised edge region 68 extend over an equal distance transverse to the planar region 56.

The tube 64 has a diameter D1 and the tube 66 has a diameter D2, where D1 is preferably larger than D2 by a suitable amount so that the tube 66 can be nested within a corresponding tube 64 located on another plate. To facilitate this nesting, the smaller diameter tube 66 can be curved radially inward at 70 (see Figure 5) while the tube 64 is flared outward at 72.

Referring particularly to Figure 6, the plates 14 , 16 are provided with an approximately spherical projection 74 located near one end and extending in the same direction as the recesses 58. A spherical recess 78 is also provided near the other end of the plate and extends in the opposite direction with respect to the projection 74. The projection 74 and the recess 78 are provided to prevent relative lateral movement between the plates 14 and 16 during assembly of the heat exchanger. The projection 74 extends over more than half the plate spacing (D3) and fits into the recess 78 when the plates are pressed together, thereby preventing lateral movement between the plates. Preferably, the projection 74 and the receptacle 78 are disposed on each plate along a line extending between the tubes 64 and 66, as shown in Figure 4, and are each adjacent to a tube so as to provide an additional flow obstruction in the flow passage between the plates.

The plate pairs 18 are individually assembled by pressing the plates together so that the raised edge areas 68 of each plate are in precise position relative to one another and the projections 74 of one plate fit into the recesses 78 provided on the other plate.

When assembled, the plate pairs each contain two pairs of concentrically aligned tubes, with the concentric alignment being accomplished by arranging the openings 60 in each plate to align with the openings 60 in the other plate of the pair. The tubes of each pair attached to each plate are formed with different diameters. Adjacent plate pairs are coupled together by aligning the plate pairs so that the larger diameter tube on one plate is aligned collinearly with the smaller tube of the adjacent plate pair. The plate pairs are then pressed together,

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where the smaller tube is inserted telescopically into the larger tube as can be seen in Figure 5.

Figure 7 shows another plate construction and method for coupling the tubes or pipes between adjacent plate pairs, such as plate pairs 110 and 112. The tubes 114 and 116 are of the same diameter and are formed to a length short enough that they do not overlap when they are assembled to form the heat exchanger core. When the plate pairs 110 and 112 are assembled in this coupling arrangement, the tubes 116 and 114 are inserted into a collar or receiving ring 118. When the entire heat exchanger is fully assembled and welded, an airtight connection is created between the collar 118 and the tubes 116 and 114.

Figures 5 and 7 also illustrate another plate arrangement in which the lateral end portions of the plates include transversely extending flange members 100, 130 having curvilinear end portions 102, 132. When the plate pairs 90, 92 and 110, 112 are coupled together, the curvilinear portions 102, 102' and 132, 132', respectively, overlap to help hold the plate pairs together while also preventing sharp edges. These overlapping flanges also partially define the boundaries of the airflow passage 22.

In a further embodiment of the heat exchanger of the present invention, aligned ribs (not shown) may be provided at the end regions of the plate pairs near the openings 60 instead of the recesses 58 so that the cooling liquid can flow out of the end regions.

It is easy for the expert to see that the heat exchangers have more than one inlet or outlet passage for liquids

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fluids may be provided by forming more than one tube 64 or 66 at each end of the plate.

Figures 8 and 9 illustrate two methods of forming the tube or pipe regions 64, 66 in a plate 160. Figure 8 shows a preferred manufacturing technique using a piercing and expanding process in which the plate 160 is first pierced at 162 (Figure 8a), which corresponds to a preferred position for a tube. The plate is then expanded in the vicinity of the hole 162 (Figure 8b) to form a tube 164 having a diameter Dl. The tube or pipe region 164 can be lengthened, if necessary, by a stretch-forming operation (Figure 8c) if the desired length is not achieved during expansion. The end portions of the smaller diameter tubes are bent radially inward as shown at 166, see Figure 8d, while the end portions of the larger diameter tubes are flared outward (not shown).

The diameter of the tube or pipe 164 is preferably in the range of 0.6 cm to 2 cm (1/4 to 3/4 inches) to achieve significant flow rates through the heat exchanger, thereby minimizing the likelihood of dead zones or regions of low flow rates forming.

Figure 9 shows another method of forming the tube regions at a location 180, which first includes a deep drawing step, whereby a closed tube region 182 is formed by means of a known deep drawing operation, Figure 9a, followed by a piercing operation to create an opening 184, see Figure 9b, followed by a stretch drawing step to straighten and extend the tube region 182 as shown in Figure 9c. The tube 182 has an outer diameter D1. Another tube 192 is formed in the same way in plate 180, Figures 9e to 9g, but has a smaller diameter D2. These larger diameter tube regions

The small diameter tubes have outwardly flared end portions as shown at 186 in Figure 9d, while the end portions of the small diameter tubes are curved radially inward as shown at 196 in Figure 9g.
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Numerous fin designs can be used to accommodate the cooling fluid inlet and outlet channels extending therethrough. Figure 10 shows some of these designs. Figure 10a illustrates a preferred arrangement in which a fin 200 having substantially the same planar dimensions as the plates is provided with two rectangular openings at 202 and 204 for the tubes forming the flow passages 36, 37. The openings 202 and 204 can be cut by a laser, a water jet process or by electrochemical machining.

Figure 10b shows at 210 another rib in which the openings 202' and 204' are formed as circular holes.

Figure 10c shows another possible fin arrangement in which a fin 220 has three generally rectangular regions 222, 224 and 226. Multiple inlets and outlets may be used, with Figure 10c showing two inlets 240 and 242 and two outlets 244 and 246.

Referring to Figure 11, the details of one embodiment of the fluid inlet and outlet connections to the heat exchanger of the present invention are shown. An outer plate pair, shown at 240, includes a top plate 242 provided with an opening at 244 that is concentric with the fluid inlet passage 245. A port 248 is provided with a lip portion 250 adapted to fit through the opening 244. The port 248 has a surface 252 that bears against a portion of the top plate 242. A protective receiving plate, shown at 254, is disposed adjacent and spaced from the top plate pair 240 to provide a

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uppermost air passage 241 and a fin 24 (not shown) is disposed in passage 241. A similar arrangement is used on the base of the heat exchanger. The receiving plates 254 are provided with openings 256 through which a fitting 248 is inserted. During brazing of the heat exchanger assembly, the fitting 248 is firmly connected to the plate 242 by means of a brazing joint. The fitting 248 is provided with a first inner shoulder at 258 and a second inner shoulder at 260. A standard internal thread is provided at 262. A coolant hose 264 includes a narrowed portion 266 around which an O-ring 286 is disposed and a wide portion 270 is provided with an external thread 272 which fits into the internal thread 262. The hose 264 is screwed into the port 248 until the O-ring 268 is pressed against the shoulder 258, thereby sealing the hose 264 and the port 248. A similar hose and port assembly can be used for the other fluid port connection (not shown).

The heat exchanger of the present invention may be assembled by first joining the individual plate pairs together, after which the evaporator core is built up by sandwiching the fins between adjacent plate pairs. For the embodiment shown in Figure 5, where different size tubes are used, a flare operation may be carried out when the adjacent plate pairs are joined together, the inner tube being flared outwardly against the outer tube to form a good joint between them. If the tubes are of the same diameter, sleeves may be used as shown in the embodiment of Figure 7. When the upper and lower support plates are in place, the entire evaporator is clamped and the entire assembly is then inserted into a brazing furnace and heated to a suitable temperature to effect the brazing operation, all of the plates being clad with brazing aluminum or similar.

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Furnace soldering materials, as is obvious to the person skilled in the art.

The operation of the heat exchanger shown here will be described with reference to the embodiments shown in Figures 1 and 3. Through cooling liquid inlet and outlet hoses (not shown) connected to the inlet and outlet ports 26 and 28 of the evaporator, respectively, cooling liquid enters the evaporator IO via the inlet passage 36 and flows laterally in a non-linear path through the flow passages 20 to the outlet passage 37. At the same time, air flows through the fins 24 in the air passages 22, the air being cooled by heat transfer from the fins to the cooling liquid. By appropriate selection of the tube diameter, the flow rate of liquid through the outlet passage 37 remains above a limit, thereby avoiding the problem of the formation of dead zones.

In the evaporator construction of Figure 1, the cooling liquid flows into and out of the evaporator IO via the transverse passages 36 and 37 or the lateral flow passages 20 between the latter passages.

In the other arrangement shown in Figure 3, the evaporator 40 is constructed such that the liquid flows through the passages several times due to the presence of the plugs 42 and 43 conveniently located in the passages 36' and 37'. The liquid enters the passage 37' through the inlet port 26', flows up to the plug 42 and then sideways through the passages 20' arranged in the plate pairs adjacent to the plug 42 and on reaching the passage 36' it flows upwards to the plug 43 and then sideways through the passages 20' arranged adjacent to the plug 43 to the passage 37' where the liquid rises again and sideways through the passages 20' arranged above the plug 43 to the outlet port 28'.

While the present invention has been described with respect to a preferred and other embodiments, it is obvious that numerous changes can be made to these embodiments without departing from the scope of the invention, which is defined by the following claims.

Claims (7)

Protection claims Plate heat exchanger, with: a plurality of coupled plate pairs (18), each pair including an upper plate (14) and a lower plate (16), each plate of the pair having a substantially planar portion (56), two longitudinal edges extending along the length of the plate, and two end edges connecting the longitudinal edges, the plates of each pair being sealably coupled together, the planar portions being spaced apart from one another, thereby enclosing a longitudinal flow passage (20) extending between them, and spaces being formed between adjacent plate pairs forming lateral air passages (22); wherein the plates are each provided with at least two through openings (60), the openings being spaced from the lateral edges of the plate, each opening in one plate being substantially in register with an opening in the other plate of the plate pair; wherein the plates are formed with connecting regions surrounding the edge of each opening and extending transversely to the plates; wherein the plurality of plate pairs are stacked in spaced relationship and each connecting portion extending from one plate pair is connected to a connecting portion extending from an adjacent plate pair to form a sealable coupling, the connecting portions together substantially enclosing transverse flow passages, the transverse flow passages being spaced from one another and in flow communication with the lateral flow passages; means defining an inlet port (26) in fluid communication with one of the transverse passages (36) and means defining an outlet port (28) in fluid communication with another of the transverse passages (37); wherein the transverse passages (36, 37) have end portions and means for closing the end portions which are not in flow communication with the inlet and outlet ports (26, 28); and with fins (24) disposed in the lateral air passages (22), the fins being in thermal contact with the plates and having transverse fluid passages extending therethrough, characterized in that the connecting regions are tubes (64, 66), the sealable coupling including an overlap region overlapping a region of at least one of the tubes, and in that outer end regions of the fins (24) are disposed laterally adjacent to the tubes or longitudinally outside the tubes, the lateral arrangement of the outer end regions being perpendicular to the longitudinal edges of the plates. 2. Plate heat exchanger according to claim 1, characterized in that the sealable coupling has a sleeve (118), wherein the end regions of the tubes are each inserted in a sealable manner into one end of the sleeve. 3. Plate heat exchanger according to claim 1, characterized in that the tubes (64, 66) each coupled to each plate have a first and a second diameter, the second diameter being smaller than the first diameter, so that the tube (66) with the second diameter can be sealably received by the tube (64) with the first diameter to effect the sealable coupling. 4. Heat exchanger according to claim 1, characterized in that the stack of plate pairs has outermost plate pairs (32, 34) and also includes receiving plates arranged adjacent to and spaced from the outermost plate pairs, the space between the receiving plates and the outermost plate pairs forming outermost air passages (22), and wherein fins (24) are arranged in the outermost air passages and are in thermal contact with the receiving plates. 5. Heat exchanger according to claim 1, characterized in that the plates are each provided with alignment devices which have at least one projection (74) and at least one receptacle (78) which is spaced from the projection, whereby a projection on one plate (14) of a plate pair can be received by a receptacle on the other plate (16) of the plate pair in order to form at least two interlocking connections between the plates of a plate pair. 6. Heat exchanger according to claim 1, characterized in that the plates are formed with two pairs of openings (240, 242, 244, 246) and two pairs of tubes (64, 66) , one of the pairs of openings or tubes being spaced from one end of each plate and the second pair of openings or tubes being spaced from the opposite end of each plate. 7. Heat exchanger according to claim 1, 2 or 3, characterized in that the plate pairs are spaced apart by the ribs after assembly of the plate pairs and ribs such that the distance between adjacent plate pairs in the heat exchanger corresponds to the height of the ribs which are arranged between respectively adjacent plate pairs. - 19 - Heat exchanger according to claim 1, characterized in that the end edges of the plates are each provided with a flange member extending transversely from the planar region thereof, the flange member (100, 130) being provided with a curvilinear end region (102, 132) adapted to overlap a curvilinear end region of a flange member (100, 130) of an adjacent pair of plates.