TECHNICAL FIELD
The present subject matter described herein, in general, relates to the field of 5 automobile air conditioning systems and in particular, relates to a header evaporator assembly used in automobile air-conditioning systems and method of manufacturing thereof.
BACKGROUND 10
Conventionally the air-conditioning system thereafter referred to as AC system used in automobiles uses the basic principles of vapor compression refrigerant cycle. This close cycle includes a compressor, heat exchanger (condenser), expansion valve (TXV), cooling coil or 2nd heat exchanger (evaporator). The compressor which is either powered by the engine or by a battery (in case of electric and hybrid 15 vehicles) compresses the refrigerant fluid thereby increasing temperature and pressure of refrigerant. The condenser is exposed to atmosphere that exchanges heat to surrounding through natural convection or forced convection with a fan. After cooling in condenser the refrigerant is expanded in Expansion valve (TXV) Expansion is an endothermic process in which refrigerant absorbs the heat from 20 environment and evaporates in evaporator. The gaseous refrigerant is then discharged from the evaporator and returned back to compressor. The evaporator controls cabin temperature and humidity by vapor compression in refrigeration cycle by a phase change from liquid to gas-liquid mixture.
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Thus, the evaporator is the critical part of the AC system which defines the cooling performance thereof. There are various types of evaporator designs which have evolved in series of 3 generations.
First generation evaporators were based on Serpentine type technology 30 (tube & fin) which is relatively easy for manufacturing whereby different sizes of evaporators were possible with less tooling. This technology had however low performance to weight ratio and the evaporators occupy large space in HVAC casing in addition to the larger weight. Another major disadvantage of this technology is it
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leads to high refrigerant pressure drop which is a critical to cabin cool down performance and moreover, refrigerant quantity consumed in said evaporator is high because of low performance to volume ratio.
The 2nd generation evaporators are of Plate & fin type construction that has high 5 performance to weight ratio. A Plate & Fin type Construction uses plates and finned chambers to transfer heat between fluids. It is often categorized as a compact heat exchanger to emphasize its relatively high heat transfer surface area to volume ratio. The plate & fin design is widely used for its compact size and lightweight properties, as well as in cryogenics where its ability to facilitate heat transfer with small 10 temperature differences is utilized.
However, the cost of Plate & Fin Evaporator is generally higher than Serpentine Type technology due to a higher level of detail required during manufacture.
Design of the third generation of evaporators is based on multi-flow double row flat 15 tube and fin evaporators. Headers used in third generation of evaporators are susceptible to external leakage.
Thus, there is a need for an evaporator having a header is in single piece in order to prevent external leakage, which can achieve a superior heat exchange and high 20 performance in less space. Moreover, there is a need for an evaporator with lower size and weight reduction.
SUMMARY
It is an object of the present subject matter to provide an evaporator having 25 unique microchannel construction providing a superior heat exchange and high performance.
It is an object of the present subject matter to provide an evaporator which is of compact design.
It is another object of the present subject matter to provide an evaporator 30 capable of withstanding substantial pressure.
It is another object of the present subject matter to provide an evaporator having high efficiency.
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It is yet another object of the present subject matter to provide an evaporator which can be manufactured with less tooling and thus lower manufacturing cost.
It is yet another object of the present subject matter to provide an evaporator of easy design which can be modified without any additional tooling costs.
It is yet another object of the present subject matter to provide evaporator 5 which has increased burst pressure resistance and strength as compared with Generation 2 Evaporator
It is yet another object of the present subject matter to provide an evaporator manufactured from the sheet metal of less thickens thus having light weight.
It is yet another object of the present subject matter to provide an evaporator 10 made of higher strength material and non-extrude able materials thus providing higher pressure and corrosion resistance.
It is yet another object of the present subject matter to provide an evaporator having increased size of the core thus higher thermal performance.
It is yet another object of the present subject matter to have flexibility in 15 design with less manufacturing challenges.
The present subject matter relates to an evaporator assembly comprising a single piece D-shaped header, tube, fins, core, side channel, inlet and outlet pipe, inlet outlet block, end plates and baffles wherein the plurality of aluminum tubes are connected at the end of end plate of the D-shaped header and wherein the baffles are 20 inserted between the D-shaped header for the flow distribution inside the core of the evaporator.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The foregoing and further objects, features and advantages of the present 25 subject matter will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements.
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter, and are therefore, not to be considered for 30 limiting of its scope, for the subject matter may admit to other equally effective embodiments.
Figure 1 illustrates a perspective view of a partition plate and baffle assembly in evaporator in accordance with an embodiment of the present subject matter.
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Figure 1A, B,C illustrate a perspective view of different types of attaching pipes to the evaporator in accordance with an embodiment of the present subject matter.
Figure 2 A, B, C, D illustrate an isometric, top, side and bottom view of D-Header Type-A in accordance with another embodiment of the present subject matter. 5
Figures 3 A, B, C illustrate an isometric, top, side view of D-Header Type-B in accordance with an embodiment of the present subject matter.
Figure 4 illustrates an isometric view of D-header Type-C in accordance with an embodiment of the present subject matter.
Figure 5 illustrates a front view of partition plates in accordance with an 10 embodiment of the present subject matter.
Figure 6 illustrates a front view of baffles and end caps in accordance with an embodiment of the present subject matter.
Figure 7 illustrates an isometric view of baffles and partition plate assembly in accordance with an embodiment of the present subject matter. 15
Figure 8A, B, C illustrates an isometric view of a header, a partition plate, a baffle plate assembly process in accordance with an embodiment of the present subject matter.
Figure 9 illustrates a cross-sectional view of D-header (Stage 1) showing bends in accordance with an embodiment of the present subject matter. 20
Figure 10 illustrates a cross-sectional view of D-header (Stage 2) showing Trench in accordance with an embodiment of present subject matter.
Figure 11 illustrates a cross-sectional view of D-header showing Trench in accordance with an embodiment of present subject matter.
Figure 12 illustrates a cross-section view of D-header stage 3 showing ribs in 25 accordance with an embodiment of present subject matter.
DETAILED DESCRIPTION
The following presents a detailed description of various embodiments of the present subject matter with reference to the accompanying drawings. 30
The embodiments of the present subject matter are described in detail with reference to the accompanying drawings. However, the present subject matter is not limited to these embodiments which are only provided to explain more clearly the present subject matter to a person skilled in the art of the present disclosure. In the
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accompanying drawings, like reference numerals are used to indicate like components.
The specification may refer to “an”, “one”, “different” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single 5 embodiment. Single features of different embodiments may also be combined to provide other embodiments.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” 10 when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being “attached” or “connected” or “coupled” or “mounted” to another element, it can 15 be directly attached or connected or coupled to the other element or intervening elements may be present. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.
The figures depict a simplified structure only showing some elements and functional entities, all being logical units whose implementation may differ from 20 what is shown.
Figure 1 illustrates a perspective view of an evaporator assembly 100 in accordance with an embodiment of the present subject matter. The evaporator assembly (100) comprises a core (102) consisting of plurality of tubes (104) and plurality of fins (106) wherein plurality of tubes (104) and the plurality of fins (106) 25 are inserted between a pair of headers (108a, 108b) so that the pair of headers (108a, 108b) holds the core 102 made of the plurality of fins 106 and plurality tubes 104 firmly in position.
The pair of headers consists of a top header (108a) and a bottom header (108b) having the core (102) affixed between the top and bottom header (108a, 108b). 30 In order to create two chambers in the each of the headers (108a, 108b) a pair of partition plates (110a, 110b) is inserted thereto to divert the flow of the refrigerant across the plurality of tubes (104) so the higher heat transfer coefficient is obtained. Figure 1 further shows a plurality of baffles (128) attached to a pair of partition plates
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(110a, 110b). The pipes (105) are connected to the bottom header (108b) as described in Figure 1A via a top plate (107) and a bottom plate (109). Further, the pipes (105) can be attached to the bottom header (108b) through an end cap (120) which is positioned at the end of the bottom header (108b) as illustrated in Figure 1B. The pipes (105) can be also directly mounted to the inlet and outlet apertures (122a, 122b) 5 provided on the upper surface of the bottom header (108b). The top header (108a, 108b) are made in single piece.
The present invention provides 3 embodiment of the header (108), Type-A header (108A), Type-B header (108B) and Type-C header (108C) said header (108) is 10 also called D-Header for having D-shaped cross section.
The first embodiment of the present invention is depicted by Figures 2A , 2B, 2C and 2D illustrating isometric, top and side and bottom view respectively of Type-A header (108A). Type-A header (108A ) comprises plurality of ribs (114) are 15 arranged on the surface of Type-A header (108A) wherein the plurality of ribs (114) is disposed in a first row (116a) in the longitudinal direction of the Type-A header (108A) and in the second row (116b) opposite the first row (116a) in the longitudinal direction of the Type-A header (108A).
The plurality of ribs (114) provides strength and burst pressure resistance and 20 helps in stiffening and act as load paths. The ribs used in thin sheets are very flexible and likely to either buckle of flex excessively thus if the partition plate (110 a, 110b) is compressed in the plane, the stiffeners will significantly increase the buckling load. However, if the partition plate (110a, 110b) is loaded out of plane, the stiffeners act as beams to resist deformation and carry load to the supports. The loadings that are 25 out of plane can be withstood by the ribs (114) by approximating subdivision of the partition plate (110a, 110b) as beams with a trapezoidal cross section. If the sheet is being compressed in plane the ribs (114) provide strength from buckling.
In an embodiment of present subject matter the ribs (114) are on the surface of the Type-A header (108A). The ribs (114) are punched into the surface by the help 30 of a punch (not shown). The ribs (114) are punched into surface of the first portion (116a) and the second portion (116b) of the Type-A header (109) in the distance from the center of the Type-A header (108A). The surface of the ribs (114) is made with fillet type which releases stress in the sheet and also help to protect the sheet metal
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from buckling. The ribs (114) also ensure the turbulence of flow inside the Type-A header (10A) for the better heat transfer.
Fig. 2D illustrates a plurality of pocket of tubes (118) disposed on the flat portion of the D-shaped cross section, in two identical rows in the longitudinal direction of the length of the Type-A header (108A). The pocket tubes (118) are cut 5 during its manufacturing process and include the inward projection of parts to hold the plurality of tubes (104) firmly. This supports the tubes (104) to be in position and provides necessary strength during vibrations while the vehicle is on the road. The pocket tubes (118) are needed to be coated with an extra thick layer of nocolux flux for its sufficient brazing. This is also a critical zone on the process consideration 10 while the evaporator is brazed in an electric nitrogen conveyor furnace.
As further indicated in Figure 2A, 2B and 2C a plurality of slits (112a) are disposed on the upper surface of the Type-A header (108A) to accommodate at least one end cap (120) not shown, which is disposed at the proximity of each edge of the Type-A header (108A) hence defining the horizontal length of the evaporator (100) 15 whereas position of end cap (120) is defined according to design of the core (102). The end cap (120) is placed at a marginal distance so that it is brazed properly and it is able to sustain operating pressure inside the header (108). Moreover, at least one slit (112b) dispose on the upper surface of the Type-A header accommodates at least one baffle (128). 20
The second embodiment of the present invention is shown in Figures 3A, 3B and 3C illustrating isometric, top and side view respectively of Type-B header (108B) having a different distribution of ribs (114) in order to accommodate the inlets of the refrigerant (122a, 122b). The plurality of ribs (114) are disposed in the first row (116a) in the longitudinal direction of the Type-B header (108B) whereas the 25 second row (116b) comprises less ribs (114) in order to accommodate inlets of the refrigerant (122a, 122b) disposed the side of the Type-B header (108B). The ribs (114) are used mainly to increase the strength of Type-B header (108B).
The plurality of pocket tubes (118) are pierced to the flat portion of the D-shaped cross section of the Type-B header (108B) distributed in two rows along the 30 longitudinal direction in identical manner as shown in Fig. 2D in order to hold the tubes (104) firmly in the position.
The Type-B header (108B) also comprises a plurality of slits (112a, 112b) disposed on the upper surface of the Type-B header (108B) wherein the plurality of
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slits (112a) are disposed at each end of the Type-B header (108B) to accommodate at least one end cap (120) whereas the plurality of slits (112b) accommodate plurality of baffles (128).
The third embodiment of the present invention is shown in Figure 4 which 5 illustrates isometric view of a The Type-C header (108C) comprising a plurality of ribs (114) punched into surface of the first portion (116a) and the second portion (116b) in the longitudinal direction thereof. The Type-C header (108C) has a different rib (114) pattern for optimizing its strength.
Also as in previous embodiments Type-C header (108C) comprises a plurality 10 of slits (112a, 112b) disposed on the upper surface of the Type-C header (108C) wherein the plurality of slits (112a) are disposed at each end of the Type-C header (108C) to accommodate at least one end cap (120) whereas the plurality of slits (112b) accommodate plurality of baffles (128).
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Figure 5 disclose the partition plates (110a, 110b) which are disposed in the D-shaped header (108) to create two chambers therein. It is used for passing refrigerant through the header (108) and into operative relationship with tube nest. The refrigerant is passed from one chamber to another chamber through transfer holes (124). The partition plates (110a, 110b), in addition of creating two chambers, also 20 provide internal strength to the header (108) from bursting and resist internal leakage of refrigerant inside the plurality of headers (108a, 108b).The partition plates (110a, 110b) have a number of baffle slots (126a, 126b) thereon. The baffle slots (126a) at the both ends of partition plate (110b) accommodate at least one end cap (120) whereas partition plate (110a) has an end cap (120) only on one end thereon. 25
The slots (126a, 126b) disposed on the partition plates (110a, 110b) accommodate different types of baffles (128) including the end cap (120) are illustrated on Figure 6. The baffles (128a, 128b, 128c) are simple a sheet metal plate used to transfer the refrigerant from one chamber to another through passing of multiple tubes (104) attached to the core (102). The baffles (128a, 128b, 128c) 30 increase the path of refrigerant in order to obtain the optimum value performance and lowering the pressure drop of evaporator (100), depends on the number of baffles (128) used in the evaporator (100). Design baffle with hole or slot do not increase the
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path of refrigerant, it adds to increase the strength of header (108) to sustain the burst pressure & to regulate the refrigerant flow in evaporator (100).
The regulated flow result in uniform cooling along the face of evaporator
The baffles (128a, 128b, 129c) direct the flow across the plurality of tubes (104) to obtain a higher heat transfer coefficient as the heat transfer coefficient is 5 higher than the coefficient for undisturbed flow around the tubes without baffles. For a baffled heat exchanger (100) the higher heat transfer coefficient results from the increased turbulence. The velocity of fluid fluctuates because of the constricted area between the adjacent headers (108a, 108b) across the plurality of tubes (104) and fins (106). Moreover, the baffles (128a, 128b, 128c) and the end cap (120) support the 10 plurality of headers (108a, 108b) for structural rigidity and prevent the vibration of header (180) and sagging.
Figure 7 illustrates assembly of the partition plate (110b) and the end caps (120) disposed in the slots (126a) at the end thereof whereas baffles (128a, 128b, 128c) are disposed in the slots (126b) disposed between the end caps (120). 15
Further, Figure 8A illustrates assembly of header (108), at least one partition plate (110) is inserted in at least one headers (108). Once the partition plate (110) is inserted in the header (108) the baffle slots (126a,126b) disposed on the partition plate (110) correspond to the slots (112a, 112b) disposed on the upper surface of the 20 header (108). Thus, enabling insertion of the cap ends (120) in the slots (112a) and insertion of the plurality of baffles (128a, 128b, 128c) in the baffle slots (126b) thereby interlocking with the partition plate (110) as shown in Figure 8B In order to get optimum thermal performance from the evaporator assembly (100) it is necessary to consider manufacturing as it is difficult to place multiple types of baffles (128) and 25 the end caps (120) in a single header at appropriate place where required. Major disadvantage of placing the inappropriate baffles in slots (126) will lead to blockage or lower the performance of evaporator assembly (100) in the vehicle. Thereby, to overcome these issues the assembly as shown in Figure 8C fulfills following conditions. 30
x1 ≠ x2 ≠ x3 ≠ x4 (Depth of baffle Slot)
w1 = w2 (Width of Baffle Slot (w1) > width of Partition Plate (w2))
d1 ≠ d2 ≠ d3 ≠ d4 (Depth of Partition Plate)
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During manufacturing initially the partition plate (110) is inserted in the D-shaped header (108) matching with the slots provided in the header (108) Slots (126) in the partition plate (110) is equal to baffle thickness only with addition of tolerance. Thus, assembly of maximum thickness of baffle (128) and end caps (120) done with maximum width of header (108) and partition plate (110) only. Maximum thickness 5 of baffle (128) and end caps (120) not inserted in minimum width of header slot (126), whereas minimum thickness of baffle freely moved in maximum width of header slot (126) and not brazed with header (108).
The manufacturing process of the D-shaped header (108) is illustrated in 10 Figures 9 and 10. The required size of the aluminum sheet is cut from the raw material or the rolls of the aluminum sheet. The cutting process is done by stamping or blanking process. The ribs are stamped on the surface of the sheet. During the bending process in the first stage the bend-1 (132) is formed on the flat sheet which is blanked to form the present invention. The bend-2 (134) is made after bend-1 (132) 15 followed by bend-3 (136). As per preferred embodiment of present invention bend-1 (132) is at 90deg and includes a radius of 10 mm, followed by bend-2 (134) including bending radius of 10mm and final bend-3 (136) having a bending radius of 3mm.
After the bends trench profile (130) as shown in Figure 10 is punched by a 20 punching die on the top surface of the D-shaped cross section. Appropriate force has to be applied so that no part is damaged. The trench profile (130) is made on the top of the header (108) in two stages. Single mandrel made with complete top was challenging and it was damaging to the header thus to counter the problem mandrel was used in two stages. Two piece chamfered mandrel was used to overcome the 25 thinning problem of the invention.
The trench profile (130) has a slight bow in the partition plate (manufacturing constraint due to thin and long profile) can be taken care of, so that partition plate (110) movement in header (108) is straight and smooth brazing land to be increased 30 to ensure inform brazing between parts.
The trench profile (130) provides proper guiding way to baffle (128) and eliminate internal leakage. During various pressing operation on header (108), profile
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can get disturbed on insertion baffles (128) which might lead to internal leakage or difficulties in insertion of baffles (128). As indicated in Figure 11 headers (108) having baffle slot and form butt joint (138) with baffle (128) after insertion and eliminate internal leakage. Moreover, the contact angle of header and partition plate is smaller which enhance capillary pumping action of filler metal when brazing hence 5 drastically improving brazing joint forming between the header (108) and partition plate (110). Both ends of partition plate can keep in contact with header (108) thanks to header side joint shape that has more flexible holding structure.
Figure 12 illustrate an assembled D-shaped cross- section of the header (108) having punched trench profile (130), ribs (114) with inserted partition plate (110) and 10 pocket tubes (118) cut in the flat portion of the D-shaped cross-section. Thereafter an ultrasonic washing process of the plurality of headers (108a, 108b) is carried out. Consequently headers (108a, 108b) are used for assembly of core (102) in a core builder machine where the other inlet and outlet pipe or the connecting pads are also attached to form evaporator assembly (100). Thin coating of nocolux flux is prayed 15 over finalized the evaporator assembly (100). After fluxing process the evaporator assembly (100) is passed through an electric furnace which is placed on a conveyer belt. The evaporator assembly (100) is brazed under low oxygen nitrogenized atmosphere.
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The preferred method of manufacturing uses a bending method of sheet material wherein constrain in design of various dimensions is eliminated. Many non-extrude able aluminum alloys can be used in preferred embodiment being capable of increasing performance and strength of evaporator.
The present invention uses a sheet metal of aluminum instead of extrusion or 25 drawing process. The use of sheet metal makes the product lighter by choosing thickness of the sheet metal. A higher strength material and non-extrude able materials can be used resulting in higher pressure and corrosion resistance.
Thus, the present subject matter provides an evaporator assembly (100) having increased thermal performance and strength durability of the headers (108a, 30 108b).
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense.
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Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore, contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined. 5
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We Claim:
1. A header Evaporator assembly (100) comprising:
- a plurality of headers (108a, 108b) to distribute heat exchange liquid;
- a plurality of partition plates (110a, 110b) each inserted in the plurality of 5 headers (108a, 108b) to create a plurality of chambers;
- a plurality of baffles (128 a, 128b, 128c) inserted in a plurality the headers (108) to interlock with the plurality of partition plates (110a, 110b) to divert the flow of refrigerant in the plurality of headers (108a, 108b).
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2. The header evaporator assembly (100) as claimed in claim 1, wherein the plurality of headers (108a, 108b) comprise a top header(108a) and a single piece bottom header (108b) having D-shaped cross section.
3. The header evaporator assembly (100) as claimed in claims 1 and 2, wherein 15 the plurality of slots (112a, 112b) and the plurality of ribs (114) are punched on top surface of D-shaped cross section of the plurality of headers (108a, 108b); said plurality of ribs (114) are placed in a first row (116a) and a second row (116b) facing the first row (116a) in the longitudinal direction.
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4. The header evaporator assembly (100) as claimed in claims 1 and 3, wherein the plurality of partition plates comprises a plurality of slots (126a, 126b) to correspond to the plurality of slots (112a, 112b) when the plurality of partition plate (110a, 110b) is inserted in the plurality of headers (108a, 108b).
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5. The header evaporator assembly (100) as claimed in claims 1 and 2, wherein a plurality of pocket tubes (118) are pierced in the flat part of the D-shaped cross section of the plurality of headers (108a, 108b) in two rows along the longitudinal direction.
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6 The header evaporator assembly (100) as claimed in claim 5, wherein a core (102) comprising a plurality of fins (106) and a plurality of tubes (104) is inserted in the plurality of pocket tubes (118) of each of the plurality of headers (108a,
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108b) to keep the core (102) in the position between the plurality of headers (108a, 108b).
7. The header evaporator assembly (100) as claimed in claim 1, wherein some of the plurality of baffles has a plurality of transfer holes (124) to allow passing of the 5 refrigerant through the plurality of chambers.
8. The header evaporator assembly (100) as claimed in claim 1, wherein each of the plurality of baffles (128 a, 128b, 128c) are disposed in each of a plurality of baffle slots (126b) provided on a plurality of partition plates (110a, 110b). 10
9. The header evaporator assembly (100) as claimed in claim 1, wherein an end cap (120) is disposed in the slot (112a) on each end of the header (108) to interlock with a slot (126a) provided on the each end of the plurality of partition plates (110a, 110b) 15
10. The header evaporator assembly (100) as claimed in claim 1 and 2, wherein a trench profile (130) is punched in the middle of the top surface of D-shaped cross section of the plurality of headers (108a, 108b) along the longitudinal direction in order to allow insertion of each of the partition plates (110a, 110b) into each of the 20 plurality of headers (108a, 108b).
11. The header evaporator assembly (100) as claimed in claim 1, wherein the header evaporator assembly (100) is made of aluminum sheet material.
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12. The header evaporator assembly (100) as claimed in claims 1 to 11, wherein the plurality of headers (108a, 108b) are made in single piece.