The present disclosure relates generally to heat exchangers, and more specifically, to a method for manufacturing a heat exchanger tube from a single metal strip having different thickness in portions.
BACKGROUND
Typically, heat exchangers are employed as condensers and evaporators for use indifferent heat exchanging applications. A heat exchanger includes a large number of relatively thin-walled flat tubes with small-sized ports through which a refrigerant passes and exchanges heat with air on the other side of the heat exchanger before exiting it. The tube-based heat exchangers could fail due to inlet end corrosion or erosion and tube end cracking. Further, in automotive applications, the heat exchanger tubes may be subjected to external impacts such as a stone impingement on the nose of the tubes which are exposed to the front of the vehicle. Additionally, the tubes have to withstand internal stresses due to thermal variations and pressure pulsations.
Further, the process of forming tube and various ports therein often entails a significant number of processing steps to accurately shape the ports that allow for heat transfer. Typically, there are two types of tubes that are utilized in the automotive sectors. Out of these two types, a first type of tube is made by an extrusion process wherein the ports are formed in an extrusion die. A second type of tube can be referred to as a fabricated or formed tube. The second type of tube can be described broadly as being manufactured by two different methods. In a first known method, the second type of tube is formed by utilizing a single flat sheet of metal which is folded in various steps to form a structure that has the walls of the ports of the same thickness as the outside wall of the tube. As a result, the second type of tube thus created is heavier than would be normally required from a strength and/ora corrosion standpoint.

To overcome this problem, another manufacturing process entails use of two sheets of different thickness to form the second type of tube. The first sheet forms an enclosure while the second, a relatively thinner sheet is corrugated to form channels internally. The second sheet is then inserted into the enclosure. Subsequently, the whole structure is brazed to produce the heat exchanger tube. This is a very difficult and expensive process because of the need to handle two separate pieces that includes a difficult insertion process.
As described above, the existing solutions have limitations which are overcome by the present invention.
SUMMARY
The present disclosure seeks to provide a method of fabricating a metal strip adapted to be used for producing a heat exchanger tube.
The present disclosure seeks to provide a heat exchanger tube comprising a plurality of heat exchanging channels, a top wall, and a bottom wall folded around the plurality of heat exchanging channels using the metal strip.
In an embodiment, a method of fabricating a heat exchanger tube is disclosed. The method includes providing a tube formed with one strip of heat conducting material with at least two thicknesses folded so that the tube has a cross section that defines a bottom wall with two opposing edges transitioning into a top wall spaced apart from the bottom wall to define an interior surface that surrounds a corrugated portion formed of a plurality of heat exchanging channels extending between and in contact with the interior surface of the top and bottom walls, wherein the corrugated portion is substantially thinner than the top and bottom walls.
In an embodiment, the heat conducting material is a metal strip. The metal strip includes a first portion of a first thickness and a second portion of a second thickness. The first portion forms the top and bottom walls and the second portion forms the corrugated portion.

In an embodiment, the method of fabricating the heat exchanger tube includes a method of manufacturing the metal strip. The method further includes computing a first volume of the first portion and a second volume of the second portion in accordance with predetermined requirements of the heat exchanger tube and determining an initial length and an initial thickness of a first ingot before performing a rolling operation in accordance with the first volume of the first portion, wherein the first ingot after performing the rolling operation thereupon is transformed into the first portion in such a way that a width of the first ingot after performing the rolling operation is substantially equal to a width of the first portion of the metal strip. The method further includes deriving at least one relation between an initial length and an initial thickness of a second ingot, wherein the at least one relation is dependent on the initial length of the first ingot, initial thickness of the first ingot, the first thickness of the first portion and the second thickness of the second portion, wherein the second ingot after performing the rolling operation thereupon is transformed into the second portion in such a way that a width of the second ingot after performing the rolling operation is substantially equal to a width of the second portion. The method includes performing the rolling operation on the first ingot and the second ingot; and pressing the first ingot and the second ingot at a predetermined temperature upon completion of the rolling operation to fabricate the single metal strip comprising the first portion of the first thickness and the second portion of the second thickness.
In an embodiment, the method further includes determining at least one of the initial length and the initial thickness of the second ingot in accordance with the at least one relation.
In a yet another embodiment, the method further includes determining the widths of the first ingot and the second ingot respectively required to undergo the rolling operation, wherein the respective widths of the first ingot and the second ingot remains substantially same after performing the rolling operation.
In another embodiment, the method includes defining the plurality of heat exchanging channels extending between and in contact with the interior surface of the

top and bottom walls; and folding the second portion of the metal strip to create the plurality of heat exchanging channels.
In an embodiment, the method includes folding the first portion around the folded second portion to create the top and bottom walls around the plurality of heat exchanging channels of the heat exchanger tube.
In a yet another embodiment, a width of the first ingot is selected based on a perimeter of the walls of the heat exchanger tube.
In an embodiment, a heat exchanger tube comprising a plurality of heat exchanging channels and a top wall and a bottom wall folded around the plurality of heat exchanging channels is disclosed. The plurality of heat exchanging channels are made from a first portion of a first thickness of a metal strip and the wall is made from a second portion of a second thickness of the metal strip, wherein the metal strip is fabricated using a method comprising steps of:
computing a first volume of the first portion and a second volume of the second portion in accordance with predetermined requirements of the heat exchanger tube;
determining an initial length and an initial thickness of a first ingot before performing a rolling operation in accordance with the first volume of the first portion, wherein the first ingot after performing the rolling operation thereupon is transformed into the first portion in such a way that a width of the first ingot after performing the rolling operation is substantially equal to a width of the first portion of the metal strip;
deriving at least one relation between an initial length and an initial thickness of a second ingot, wherein the at least one relation is dependent on the initial length of the first ingot, initial thickness of the first ingot, the first thickness of the first portion and the second thickness of the second portion, wherein the second ingot after performing the rolling operation thereupon is transformed into the second portion in such a way that a width of the second ingot after performing the rolling operation is substantially equal to a width of the second portion;
performing the rolling operation on the first ingot and the second ingot; and

pressing the first ingot and the second ingot at a predetermined temperature upon completion of the rolling operation to fabricate the single metal strip comprising the first portion of the first thickness and the second portion of the second thickness.
In an embodiment, the first thickness of the first portion is relatively greater than the second thickness of the second portion of the metal strip.
The present disclosure provides a method of manufacturing the heat exchanging tube from a metal strip having varying thickness level. The present disclosure provides a greater stability to the heat exchanger tube as the tube has a thicker wall, an increased heating capacity due to a relatively increased number of heat exchanging channels of the heat exchanger tube.
Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments construed in conjunction with the appended claims that follow.
It will be appreciated that numerous modifications and variations in addition to those mentioned herein will occur to those skilled in the art. Accordingly, it is intended that the invention not be limited to the disclosed embodiment, but that it have the full scope permitted by the language of the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:

Figure 1 is a schematic illustration of an exemplary cross-sectional view of a heat exchanger tube in accordance with an embodiment of the present disclosure;
Figures 2A and 2B are schematic illustrations of pre-rolling and post-rolling forms of a first ingot and a second ingot in accordance with an embodiment of the present disclosure;
Figures 3A and 3B are exemplary perspective and cross-sectional views of the single metal strip respectively in accordance with an embodiment of the present disclosure; and
Figure 4is a schematic illustration of steps of a method for fabricating the metal strip in accordance with an embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
The heat exchanging tubes of the present disclosure are used within a condenser of a system. The condenser includes two headers wherein each header among the two headers is disposed on an either side of the condenser. The plurality of heat exchanging tubes are disposed within each header of the condenser. Further the condenser includes a refrigerant inlet port and a refrigerant outlet port. A super¬heated refrigerant enters inside the condenser and a condensation of the super-

heated refrigerant happens within the plurality of heat exchanging channels of the heat exchanging tubes. Optionally, the condenser may be installed with an integrated receiver dryer bottle (IRD bottle). Once the refrigerant is condensed within the condenser, the condensed refrigerant goes out from the refrigerant outlet port in a sub cooled state.
Figure 1 is a schematic illustration of an exemplary cross-sectional view of a heat exchanger tube 100 in accordance with an embodiment of the present disclosure. As illustrated in Figure 1, the heat exchanger tube 100 is made up from one strip of a heat conducting material with at least portions having different thicknesses. The heat conducting material can be a metal strip. The metal strip is folded in such a manner that the heat exchanger tube 100 has a cross section that defines a bottom wall 102 with two opposing edges transitioning into a top wall 104spaced apart from the bottom wall 102 to define an interior surface 106. The interior surface 106surrounds a corrugated portion formed of a plurality of heat exchanging channels such as 108a, 108b, 108c and a 108d, collectively hereinafter referred to as 108extending between and in contact with the interior surface 106of the bottom wall 102 and the top wall 104. The corrugated portion is substantially thinner than the top and bottom walls. The heat exchanging channels 108 facilitates transfer of heat through a contact with the refrigerant. The heat exchanging channels are corrugated channels which are of a triangular shape. However, the corrugated channels can be of a square, rectangular or any other geometric shape in order to maintain the heat transfer efficiency of the heat exchanger tube 100.
The heat exchanger tube 100 of the present disclosure is manufactured from a single metal strip. The metal strip includes two portions namely a first portion and a second portion. The first portion has a first thickness and the second portion has the second thickness. The first portion of the metal strip has a relatively higher thickness than the second portion of the metal strip. Further, the heat exchanger tube 100 is formed by folding the first portion and the second portion at specified points respectively in a manner so that the second portion is transformed into the corrugated heat exchanging channels 108 and the first portion is folded over the corrugated heat exchanging channels 108 as the bottom wall 102 and the top wall 104. As a result,

the first portion of the metal strip provides rigidity to the heat exchanger tube 100 and the second portion of the metal strip facilitates and enhances heat exchanging capabilities of the heat exchanger tube 100. Further, the heat exchanger tube 100 being made from the single metal strip has relatively more tensile strength and a longer life than the heat exchanger tube made from multiple metal strips.
In an embodiment, a method for manufacturing the heat exchanger tube 100 from the metal strip is disclosed. Firstly, corrugated channels are formed on the second portion of the metal strip. Subsequently, the corrugated heat exchanging channels are folded within the first portion of the metal strip. Further, another fold of the first portion of the metal strip is formed so that the first portion can entirely cover the corrugated heat exchanging channels from top as well as bottom surfaces. In addition, after folding the first portion of the metal strip over the corrugated heat exchanging channels, an end portion of the second portion of the metal strip is prevented from aligning with the top wall 104. This ensures that the end portion does not interfere with the fins which will be brazed to the heat exchanger tube 100. As illustrated in Figure 1, the end portion terminates at least a distance of t3 units from a surface of the top wall 104. Furthermore, the heat exchanger tube 100 is passed through a brazing furnace so that a brazing operation is performed onto the heat exchanger tube 100 and an opening end of the first portion is securely tightened with the folded portion of the heat exchanger tube 100.
In an embodiment, a method of fabricating the metal strip adapted to be used for manufacturing the heat exchanger tube is disclosed. Normally, the heat exchanger tube specifications are first defined and subsequently, the metal strip requirements are derived so that when folding process is performed on the first portion and the second portion of the metal strip, the heat exchanger tube 100 of desired specifications can be obtained.
In an embodiment, a first volume of the first portion and a second volume of the second portion is computed in accordance with the desired requirements of the heat exchanger tube. For example, the design engineer may indicate a number of corrugated heat exchanging channels required in the heat exchanger tube 100 and specifications of the wall encircling the corrugated heat exchanging channels of the

heat exchanger tube 100. Accordingly, the number of the corrugated heat exchanging channels can be a representative of the specifications for the second portion of the metal strip and the wall encircling the corrugated heat exchanging channels can be a representative of the specifications for the first portion of the metal strip. The different portions i.e., the first portion and the second portion of the metal strip are obtained after performing a rolling operation on a first ingot and a second ingot.
In an embodiment, an initial length and an initial thickness of the first ingot before performing a rolling operation is determined in accordance with the first volume of the first portion. The first ingot after performing the rolling operation thereupon is transformed into the first portion in such a way that a width of the first ingot after performing the rolling operation is substantially equal to a width of the first portion of the metal strip.
Further, one or more relations are derived between an initial length and an initial thickness of the second ingot. The one or more relations are dependent on the initial length of the first ingot, initial thickness of the first ingot, the first thickness of the first portion and the second thickness of the second portion. The second ingot after performing the rolling operation thereupon is transformed into the second portion in such a way that a width of the second ingot after performing the rolling operation is substantially equal to a width of the second portion of the metal strip.
In an embodiment, the initial length of the second ingot is determined using the one or more relations and a fixed initial thickness of the second ingot. Alternatively, the initial thickness of the second ingot is determined using the one or more relations and a fixed length of the second ingot.
Further, the widths of the first ingot and the second ingot respectively required to undergo the rolling operation are determined in accordance with the specifications of the heat exchanger tube 100. The respective widths of the first ingot and the second ingot remains substantially same after performing the rolling operation. In an embodiment, the width of the first ingot is selected based on a perimeter of the walls of the heat exchanger tube 100 and the width of the second ingot is selected based on the number of heat exchange channels required within the heat exchanger tube.
10

Subsequently, rolling operation on the first ingot and the second ingot is performed and the rolled forms of the first ingot and the second ingot are pressed against each other at a predetermined temperature upon completion of the rolling operation to fabricate the single metal strip comprising the first portion of the first thickness and the second portion of the second thickness.
In an embodiment, the rolled forms of the first ingot and the second ingot are pressed against each other along their respective lengths in such a manner that a longitudinal axis of the rolled form of the second ingot is aligned with a longitudinal axis of the rolled form of the first ingot. In another embodiment, the longitudinal axis of the rolled form of the second ingot is above the longitudinal axis of the rolled form of the first ingot and the top surfaces of the rolled forms of the first and second ingots are aligned with each other. In a yet another embodiment, the rolled forms of the first ingot and the second ingot are pressed against each other by adding a relative offset between them.
Figures 2A and 2B are schematic illustrations of pre-rolling and post-rolling forms of the first ingot and the second ingot respectively in accordance with an embodiment of the present disclosure. Referring to Figure 2A, a block 202 illustrates a pre-rolling form of the first ingot and a block 204 illustrates a post-rolling form of the first ingot. Referring to Figure 2B, a block 212 illustrates a pre-rolling form of the second ingot and a block 214 illustrates a post-rolling form of the second ingot. On performing the rolling operation on the first ingot and the second ingot in an illustrated direction, post-rolling forms of the first ingot and second ingot are pressed together at the predetermined temperature to generate the metal strip having two portions. The first portion is obtained from the first ingot and the second portion is obtained from the second ingot.
Since the thickness of the first portion is relatively higher than the thickness of the second portion and the metal strip specification requires length of the first portion and the second portion be of equal size, it is important that a size of the first ingot and the second ingot must be selected in a manner so that the first portion and the second portion are of desired equal length. In other words, either length or thickness of the
11

second ingot is appropriately determined to fabricate the metal strip of desired specifications.
If a volume of the first ingot before the rolling operation is Volume1i= t1iw1l1i; and
a volume of the first ingot after the rolling operation is Volume1f= t1fw1l1f;
wherein,
t1i – thickness of the first ingot before the rolling operation;
w1 – width of the first ingot before and after the rolling operation;
l1i – length of the first ingot before the rolling operation;
t1f – thickness of the first ingot after the rolling operation;
l1f – length of the first ingot after the rolling operation;
Since there is no loss of mass during the rolling operation, it can be derived that: volume of the first ingot before the rolling operation is = volume of the first ingot after the rolling operation; That is to say,
Volume1i= Volume1f Or t1iw1l1i= t1fw1l1f; Or t1il1i= t1fl1f Or l1f = (t1i *l1i)/t1f - equation 1
In a similar manner, if a volume of the second ingot before the rolling operation is Volume2i = t2iw2l2i;and
a volume of the second ingot after the rolling operation is Volume2f = t2fw2l2f;
wherein,
t2i – thickness of the second ingot before the rolling operation;
w2 – width of the second ingot before and after the rolling operation;
l2i – length of the second ingot before the rolling operation;
t2f – thickness of the second ingot after the rolling operation;
l2f – length of the second ingot after the rolling operation;
Since there is no loss of mass during the rolling operation, it can be derived that:
12

volume of the second ingot before the rolling operation is = volume of the second ingot after the rolling operation; That is to say,
Volume2i= Volume2f
Or t2iw2l2i= t2fw2l2f;
Or t2il2i= t2fl2f - equation 2
Further, as discussed above, the length of the first portion and the second portion of the metal strip is equal. That is to say, the length of the post-rolling form of the first ingot is equal to the length of the post-rolling form of the second ingot.
Or l1f should be equal to l2f
l1f = l2f
Thus, referring to the equation no 2;
t2i * l2i = t2f * l1f
Since l1f = (t1i *l1i)/t1f - see equation 1
Or t2i * l2i = t2f * (t1i *l1i)/t1f Or l2i = (t2f/t2i )* (t1i *l1i)/t1f
Therefore, if the rolling will start with a first ingot having specification as t1i=1m, l1i=1m length to achieve the post-rolling thickness t1f=0.27mm for the first ingot and the post rolling thickness t2f=0.135mm for the second ingot, then
l2i = (0.135 mm/t2i mm)*(1000 mm*1000 mm/0.27 mm) l2i = (0.5*1000*1000/t2i) mm
Thus, for the predetermined specifications of the pre-rolling forms of the first ingot, the first thickness of the first portion, and the second thickness of the second portion, a relation can be derived between the pre-rolling length and the pre-rolling thickness of the second ingot.
13

Figure 3A illustrates an exemplary perspective view of the metal strip formed from the first ingot and the second ingot in accordance with an embodiment of the present disclosure. The metal strip includes the first portion of the first thickness t1 and the second portion of the second thickness t2. Figure 3B illustrates an exemplary cross-sectional view of the metal strip formed from the first ingot and the second ingot in accordance with an embodiment of the present disclosure.
Figure 4 illustrates exemplary steps of a method for fabricating the metal strip in accordance with an embodiment of the present disclosure. The metal strip is adapted to be used for manufacturing the heat exchanger tube comprising a plurality of heat exchanging channels and a wall folded around the plurality of heat exchanging channels. The plurality of heat exchanging channels are made from a second portion of a second thickness of a metal strip and the wall is made from a first portion of a first thickness of the metal strip.
At step 402, a first volume of the first portion and a second volume of the second portion is computed in accordance with predetermined requirements of the heat exchanger tube.
At step 404, an initial length and an initial thickness of a first ingot before performing a rolling operation in accordance with the first volume of the first portion is determined. The first ingot after performing the rolling operation thereupon is transformed into the first portion in such a way that a width of the first ingot after performing the rolling operation is substantially equal to a width of the first portion of the metal strip.
At step 406, at least one relation between an initial length and an initial thickness of a second ingot is derived. The at least one relation is dependent on the initial length of the first ingot, initial thickness of the first ingot, the first thickness of the first portion and the second thickness of the second portion. The second ingot after performing the rolling operation thereupon is transformed into the second portion in such a way that a width of the second ingot after performing the rolling operation is substantially equal to a width of the second portion.
14

At step 408, the rolling operation on the first ingot and the second ingot is performed.
At step 410, first ingot and the second ingot are pressed against each other at a predetermined temperature upon completion of the rolling operation to fabricate the single metal strip comprising the first portion of the first thickness and the second portion of the second thickness.
The present disclosure offers several advantages. Firstly, the second portion, a relatively thinner portion allows an increase in the number of the corrugated heat exchanging channels within the heat exchanger tube 100. As a result, a relatively higher number of corrugated heat exchanging channels can be formed resulting into an increased efficiency of the heat exchanger tube 100. Further, the present disclosure facilitates reduction in the usage of the material and thus renders a cost-effective approach for manufacturing the heat exchanger tube 100. Furthermore, the wall encircling the corrugated heat exchanging channels is relatively thicker which protects the corrugated heat exchanging channels from corrosion and facilitates in sustaining burst pressure specifications.
Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.

WE CLAIM
Claims:A method of fabricating a heat exchanger tube, the method comprising:
providing a tube formed with one strip of heat conducting material with at least
two thicknesses folded so that the tube has a cross section that defines a bottom wall
with two opposing edges transitioning into a top wall spaced apart from the bottom
wall to define an interior surface that surrounds a corrugated portion formed of a
plurality of heat exchanging channels extending between and in contact with the
interior surface of the top and bottom walls, wherein the corrugated portion is
substantially thinner than the top and bottom walls.
2. The method as claimed in claim 1, wherein the one strip of the heat conducting
material is a metal strip, wherein:
the metal strip comprising a first portion of a first thickness and a second portion
of a second thickness;
the first portion forms the top and bottom walls; and
second portion forms the corrugated portion.
3. The method as claimed in claim 2, further comprising:
computing a first volume of the first portion and a second volume of the second
portion in accordance with predetermined requirements of the heat exchanger tube;
determining an initial length and an initial thickness of a first ingot before
performing a rolling operation in accordance with the first volume of the first portion,
wherein the first ingot after performing the rolling operation thereupon is transformed
into the first portion in such a way that a width of the first ingot after performing the
rolling operation is substantially equal to a width of the first portion of the metal strip;
deriving at least one relation between an initial length and an initial thickness of
a second ingot, wherein the at least one relation is dependent on the initial length of
the first ingot, initial thickness of the first ingot, the first thickness of the first portion
and the second thickness of the second portion, wherein the second ingot after
performing the rolling operation thereupon is transformed into the second portion in
such a way that a width of the second ingot after performing the rolling operation is
substantially equal to a width of the second portion;
17
performing the rolling operation on the first ingot and the second ingot; and
pressing the first ingot and the second ingot at a predetermined temperature
upon completion of the rolling operation to fabricate the single metal strip comprising
the first portion of the first thickness and the second portion of the second thickness.
4. The method as claimed in claim 3, further comprising:
determining at least one of the initial length and the initial thickness of the
second ingot in accordance with the at least one relation.
5. The method as claimed in claim 4 further comprising:
determining the widths of the first ingot and the second ingot respectively
required to undergo the rolling operation, wherein the respective widths of the first
ingot and the second ingot remains substantially same after performing the rolling
operation.
6. The method as claimed in claim 3, wherein a width of the first ingot is selected
based on a perimeter of the walls of the heat exchanger tube.
7. The method as claimed in claim 2, further comprising:
defining the plurality of heat exchanging channels extending between and in
contact with the interior surface of the top and bottom walls; and
folding the second portion of the metal strip to create the plurality of heat
exchanging channels.
8. The method as claimed in claim 7, further comprising:
folding the first portion around the folded second portion to create the top and
bottom walls around the plurality of heat exchanging channels of the heat exchanger
tube.
9. A heat exchanger tube comprising a plurality of heat exchanging channels and
a top wall and a bottom wall folded around the plurality of heat exchanging channels,
wherein the plurality of heat exchanging channels are made from a second portion of
18
a second thickness of a metal strip and the top wall and the bottom wall is made from
a first portion of a first thickness of the metal strip, wherein the metal strip is fabricated
from a method comprising steps of:
computing a first volume of the first portion and a second volume of the second
portion in accordance with predetermined requirements of the heat exchanger tube;
determining an initial length and an initial thickness of a first ingot before
performing a rolling operation in accordance with the first volume of the first portion,
wherein the first ingot after performing the rolling operation thereupon is transformed
into the first portion in such a way that a width of the first ingot after performing the
rolling operation is substantially equal to a width of the first portion of the metal strip;
deriving at least one relation between an initial length and an initial thickness of
a second ingot, wherein the at least one relation is dependent on the initial length of
the first ingot, initial thickness of the first ingot, the first thickness of the first portion
and the second thickness of the second portion, wherein the second ingot after
performing the rolling operation thereupon is transformed into the second portion in
such a way that a width of the second ingot after performing the rolling operation is
substantially equal to a width of the second portion;
performing the rolling operation on the first ingot and the second ingot; and
pressing the first ingot and the second ingot at a predetermined temperature
upon completion of the rolling operation to fabricate the single metal strip comprising
the first portion of the first thickness and the second portion of the second thickness.
10. The heat exchange tube as claimed in claim 9, wherein first thickness of the
first portion is relatively greater than the second thickness of the second portion of the
metal strip. , Description:TECHNICAL FIELD
The present disclosure relates generally to heat exchangers, and more
specifically, to a method for manufacturing a heat exchanger tube from a single metal
strip having different thickness in portions.
BACKGROUND
Typically, heat exchangers are employed as condensers and evaporators for
use indifferent heat exchanging applications. A heat exchanger includes a large
number of relatively thin-walled flat tubes with small-sized ports through which a
refrigerant passes and exchanges heat with air on the other side of the heat exchanger
before exiting it. The tube-based heat exchangers could fail due to inlet end corrosion
or erosion and tube end cracking. Further, in automotive applications, the heat
exchanger tubes may be subjected to external impacts such as a stone impingement
on the nose of the tubes which are exposed to the front of the vehicle. Additionally, the
tubes have to withstand internal stresses due to thermal variations and pressure
pulsations.
Further, the process of forming tube and various ports therein often entails a
significant number of processing steps to accurately shape the ports that allow for heat
transfer. Typically, there are two types of tubes that are utilized in the automotive
sectors. Out of these two types, a first type of tube is made by an extrusion process
wherein the ports are formed in an extrusion die. A second type of tube can be referred
to as a fabricated or formed tube. The second type of tube can be described broadly
as being manufactured by two different methods. In a first known method, the second
type of tube is formed by utilizing a single flat sheet of metal which is folded in various
steps to form a structure that has the walls of the ports of the same thickness as the
outside wall of the tube. As a result, the second type of tube thus created is heavier
than would be normally required from a strength and/ora corrosion standpoint.
3
To overcome this problem, another manufacturing process entails use of two
sheets of different thickness to form the second type of tube. The first sheet forms an
enclosure while the second, a relatively thinner sheet is corrugated to form channels
internally. The second sheet is then inserted into the enclosure. Subsequently, the
whole structure is brazed to produce the heat exchanger tube. This is a very difficult
and expensive process because of the need to handle two separate pieces that
includes a difficult insertion process.
As described above, the existing solutions have limitations which are overcome
by the present invention.
SUMMARY
The present disclosure seeks to provide a method of fabricating a metal strip
adapted to be used for producing a heat exchanger tube.
The present disclosure seeks to provide a heat exchanger tube comprising a
plurality of heat exchanging channels, a top wall, and a bottom wall folded around the
plurality of heat exchanging channels using the metal strip.
In an embodiment, a method of fabricating a heat exchanger tube is disclosed.
The method includes providing a tube formed with one strip of heat conducting
material with at least two thicknesses folded so that the tube has a cross section that
defines a bottom wall with two opposing edges transitioning into a top wall spaced
apart from the bottom wall to define an interior surface that surrounds a corrugated
portion formed of a plurality of heat exchanging channels extending between and in
contact with the interior surface of the top and bottom walls, wherein the corrugated
portion is substantially thinner than the top and bottom walls.
In an embodiment, the heat conducting material is a metal strip. The metal strip
includes a first portion of a first thickness and a second portion of a second thickness.
The first portion forms the top and bottom walls and the second portion forms the
corrugated portion.
4
In an embodiment, the method of fabricating the heat exchanger tube includes
a method of manufacturing the metal strip. The method further includes computing a
first volume of the first portion and a second volume of the second portion in
accordance with predetermined requirements of the heat exchanger tube and
determining an initial length and an initial thickness of a first ingot before performing a
rolling operation in accordance with the first volume of the first portion, wherein the
first ingot after performing the rolling operation thereupon is transformed into the first
portion in such a way that a width of the first ingot after performing the rolling operation
is substantially equal to a width of the first portion of the metal strip. The method
further includes deriving at least one relation between an initial length and an initial
thickness of a second ingot, wherein the at least one relation is dependent on the initial
length of the first ingot, initial thickness of the first ingot, the first thickness of the first
portion and the second thickness of the second portion, wherein the second ingot after
performing the rolling operation thereupon is transformed into the second portion in
such a way that a width of the second ingot after performing the rolling operation is
substantially equal to a width of the second portion. The method includes performing
the rolling operation on the first ingot and the second ingot; and pressing the first ingot
and the second ingot at a predetermined temperature upon completion of the rolling
operation to fabricate the single metal strip comprising the first portion of the first
thickness and the second portion of the second thickness.
In an embodiment, the method further includes determining at least one of the
initial length and the initial thickness of the second ingot in accordance with the at least
one relation.
In a yet another embodiment, the method further includes determining the
widths of the first ingot and the second ingot respectively required to undergo the
rolling operation, wherein the respective widths of the first ingot and the second ingot
remains substantially same after performing the rolling operation.
In another embodiment, the method includes defining the plurality of heat
exchanging channels extending between and in contact with the interior surface of the
5
top and bottom walls; and folding the second portion of the metal strip to create the
plurality of heat exchanging channels.
In an embodiment, the method includes folding the first portion around the
folded second portion to create the top and bottom walls around the plurality of heat
exchanging channels of the heat exchanger tube.
In a yet another embodiment, a width of the first ingot is selected based on a
perimeter of the walls of the heat exchanger tube.
In an embodiment, a heat exchanger tube comprising a plurality of heat
exchanging channels and a top wall and a bottom wall folded around the plurality of
heat exchanging channels is disclosed. The plurality of heat exchanging channels are
made from a first portion of a first thickness of a metal strip and the wall is made from
a second portion of a second thickness of the metal strip, wherein the metal strip is
fabricated using a method comprising steps of:
computing a first volume of the first portion and a second volume of the second
portion in accordance with predetermined requirements of the heat exchanger tube;
determining an initial length and an initial thickness of a first ingot before
performing a rolling operation in accordance with the first volume of the first portion,
wherein the first ingot after performing the rolling operation thereupon is transformed
into the first portion in such a way that a width of the first ingot after performing the
rolling operation is substantially equal to a width of the first portion of the metal strip;
deriving at least one relation between an initial length and an initial thickness of
a second ingot, wherein the at least one relation is dependent on the initial length of
the first ingot, initial thickness of the first ingot, the first thickness of the first portion
and the second thickness of the second portion, wherein the second ingot after
performing the rolling operation thereupon is transformed into the second portion in
such a way that a width of the second ingot after performing the rolling operation is
substantially equal to a width of the second portion;
performing the rolling operation on the first ingot and the second ingot; and
6
pressing the first ingot and the second ingot at a predetermined temperature
upon completion of the rolling operation to fabricate the single metal strip comprising
the first portion of the first thickness and the second portion of the second thickness.
In an embodiment, the first thickness of the first portion is relatively greater than
the second thickness of the second portion of the metal strip.
The present disclosure provides a method of manufacturing the heat
exchanging tube from a metal strip having varying thickness level. The present
disclosure provides a greater stability to the heat exchanger tube as the tube has a
thicker wall, an increased heating capacity due to a relatively increased number of
heat exchanging channels of the heat exchanger tube.
Additional aspects, advantages, features and objects of the present disclosure
would be made apparent from the drawings and the detailed description of the
illustrative embodiments construed in conjunction with the appended claims that
follow.
It will be appreciated that numerous modifications and variations in addition to
those mentioned herein will occur to those skilled in the art. Accordingly, it is intended
that the invention not be limited to the disclosed embodiment, but that it have the full
scope permitted by the language of the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The summary above, as well as the following detailed description of illustrative
embodiments, is better understood when read in conjunction with the appended
drawings. For the purpose of illustrating the present disclosure, exemplary
constructions of the disclosure are shown in the drawings. However, the present
disclosure is not limited to specific methods and instrumentalities disclosed herein.
Moreover, those in the art will understand that the drawings are not to scale. Wherever
possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of
example only, with reference to the following diagrams wherein:
7
Figure 1 is a schematic illustration of an exemplary cross-sectional view of a
heat exchanger tube in accordance with an embodiment of the present disclosure;
Figures 2A and 2B are schematic illustrations of pre-rolling and post-rolling
forms of a first ingot and a second ingot in accordance with an embodiment of the
present disclosure;
Figures 3A and 3B are exemplary perspective and cross-sectional views of the
single metal strip respectively in accordance with an embodiment of the present
disclosure; and
Figure 4is a schematic illustration of steps of a method for fabricating the metal
strip in accordance with an embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an
item over which the underlined number is positioned or an item to which the underlined
number is adjacent. A non-underlined number relates to an item identified by a line
linking the non-underlined number to the item. When a number is non-underlined and
accompanied by an associated arrow, the non-underlined number is used to identify
a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present
disclosure and ways in which they can be implemented. Although some modes of
carrying out the present disclosure have been disclosed, those skilled in the art would
recognize that other embodiments for carrying out or practicing the present disclosure
are also possible.
The heat exchanging tubes of the present disclosure are used within a
condenser of a system. The condenser includes two headers wherein each header
among the two headers is disposed on an either side of the condenser. The plurality
of heat exchanging tubes are disposed within each header of the condenser. Further
the condenser includes a refrigerant inlet port and a refrigerant outlet port. A superheated
refrigerant enters inside the condenser and a condensation of the super8
heated refrigerant happens within the plurality of heat exchanging channels of the heat
exchanging tubes. Optionally, the condenser may be installed with an integrated
receiver dryer bottle (IRD bottle). Once the refrigerant is condensed within the
condenser, the condensed refrigerant goes out from the refrigerant outlet port in a sub
cooled state.
Figure 1 is a schematic illustration of an exemplary cross-sectional view of a
heat exchanger tube 100 in accordance with an embodiment of the present disclosure.
As illustrated in Figure 1, the heat exchanger tube 100 is made up from one strip of a
heat conducting material with at least portions having different thicknesses. The heat
conducting material can be a metal strip. The metal strip is folded in such a manner
that the heat exchanger tube 100 has a cross section that defines a bottom wall 102
with two opposing edges transitioning into a top wall 104spaced apart from the bottom
wall 102 to define an interior surface 106. The interior surface 106surrounds a
corrugated portion formed of a plurality of heat exchanging channels such as 108a,
108b, 108c and a 108d, collectively hereinafter referred to as 108extending between
and in contact with the interior surface 106of the bottom wall 102 and the top wall 104.
The corrugated portion is substantially thinner than the top and bottom walls. The heat
exchanging channels 108 facilitates transfer of heat through a contact with the
refrigerant. The heat exchanging channels are corrugated channels which are of a
triangular shape. However, the corrugated channels can be of a square, rectangular
or any other geometric shape in order to maintain the heat transfer efficiency of the
heat exchanger tube 100.
The heat exchanger tube 100 of the present disclosure is manufactured from a
single metal strip. The metal strip includes two portions namely a first portion and a
second portion. The first portion has a first thickness and the second portion has the
second thickness. The first portion of the metal strip has a relatively higher thickness
than the second portion of the metal strip. Further, the heat exchanger tube 100 is
formed by folding the first portion and the second portion at specified points
respectively in a manner so that the second portion is transformed into the corrugated
heat exchanging channels 108 and the first portion is folded over the corrugated heat
exchanging channels 108 as the bottom wall 102 and the top wall 104. As a result,
9
the first portion of the metal strip provides rigidity to the heat exchanger tube 100 and
the second portion of the metal strip facilitates and enhances heat exchanging
capabilities of the heat exchanger tube 100. Further, the heat exchanger tube 100
being made from the single metal strip has relatively more tensile strength and a longer
life than the heat exchanger tube made from multiple metal strips.
In an embodiment, a method for manufacturing the heat exchanger tube 100
from the metal strip is disclosed. Firstly, corrugated channels are formed on the
second portion of the metal strip. Subsequently, the corrugated heat exchanging
channels are folded within the first portion of the metal strip. Further, another fold of
the first portion of the metal strip is formed so that the first portion can entirely cover
the corrugated heat exchanging channels from top as well as bottom surfaces. In
addition, after folding the first portion of the metal strip over the corrugated heat
exchanging channels, an end portion of the second portion of the metal strip is
prevented from aligning with the top wall 104. This ensures that the end portion does
not interfere with the fins which will be brazed to the heat exchanger tube 100. As
illustrated in Figure 1, the end portion terminates at least a distance of t3 units from a
surface of the top wall 104. Furthermore, the heat exchanger tube 100 is passed
through a brazing furnace so that a brazing operation is performed onto the heat
exchanger tube 100 and an opening end of the first portion is securely tightened with
the folded portion of the heat exchanger tube 100.
In an embodiment, a method of fabricating the metal strip adapted to be used
for manufacturing the heat exchanger tube is disclosed. Normally, the heat exchanger
tube specifications are first defined and subsequently, the metal strip requirements are
derived so that when folding process is performed on the first portion and the second
portion of the metal strip, the heat exchanger tube 100 of desired specifications can
be obtained.
In an embodiment, a first volume of the first portion and a second volume of the
second portion is computed in accordance with the desired requirements of the heat
exchanger tube. For example, the design engineer may indicate a number of
corrugated heat exchanging channels required in the heat exchanger tube 100 and
specifications of the wall encircling the corrugated heat exchanging channels of the
10
heat exchanger tube 100. Accordingly, the number of the corrugated heat exchanging
channels can be a representative of the specifications for the second portion of the
metal strip and the wall encircling the corrugated heat exchanging channels can be a
representative of the specifications for the first portion of the metal strip. The different
portions i.e., the first portion and the second portion of the metal strip are obtained
after performing a rolling operation on a first ingot and a second ingot.
In an embodiment, an initial length and an initial thickness of the first ingot
before performing a rolling operation is determined in accordance with the first volume
of the first portion. The first ingot after performing the rolling operation thereupon is
transformed into the first portion in such a way that a width of the first ingot after
performing the rolling operation is substantially equal to a width of the first portion of
the metal strip.
Further, one or more relations are derived between an initial length and an initial
thickness of the second ingot. The one or more relations are dependent on the initial
length of the first ingot, initial thickness of the first ingot, the first thickness of the first
portion and the second thickness of the second portion. The second ingot after
performing the rolling operation thereupon is transformed into the second portion in
such a way that a width of the second ingot after performing the rolling operation is
substantially equal to a width of the second portion of the metal strip.
In an embodiment, the initial length of the second ingot is determined using the
one or more relations and a fixed initial thickness of the second ingot. Alternatively,
the initial thickness of the second ingot is determined using the one or more relations
and a fixed length of the second ingot.
Further, the widths of the first ingot and the second ingot respectively required
to undergo the rolling operation are determined in accordance with the specifications
of the heat exchanger tube 100. The respective widths of the first ingot and the second
ingot remains substantially same after performing the rolling operation. In an
embodiment, the width of the first ingot is selected based on a perimeter of the walls
of the heat exchanger tube 100 and the width of the second ingot is selected based
on the number of heat exchange channels required within the heat exchanger tube.
11
Subsequently, rolling operation on the first ingot and the second ingot is
performed and the rolled forms of the first ingot and the second ingot are pressed
against each other at a predetermined temperature upon completion of the rolling
operation to fabricate the single metal strip comprising the first portion of the first
thickness and the second portion of the second thickness.
In an embodiment, the rolled forms of the first ingot and the second ingot are
pressed against each other along their respective lengths in such a manner that a
longitudinal axis of the rolled form of the second ingot is aligned with a longitudinal
axis of the rolled form of the first ingot. In another embodiment, the longitudinal axis
of the rolled form of the second ingot is above the longitudinal axis of the rolled form
of the first ingot and the top surfaces of the rolled forms of the first and second ingots
are aligned with each other. In a yet another embodiment, the rolled forms of the first
ingot and the second ingot are pressed against each other by adding a relative offset
between them.
Figures 2A and 2B are schematic illustrations of pre-rolling and post-rolling
forms of the first ingot and the second ingot respectively in accordance with an
embodiment of the present disclosure. Referring to Figure 2A, a block 202 illustrates
a pre-rolling form of the first ingot and a block 204 illustrates a post-rolling form of the
first ingot. Referring to Figure 2B, a block 212 illustrates a pre-rolling form of the
second ingot and a block 214 illustrates a post-rolling form of the second ingot. On
performing the rolling operation on the first ingot and the second ingot in an illustrated
direction, post-rolling forms of the first ingot and second ingot are pressed together at
the predetermined temperature to generate the metal strip having two portions. The
first portion is obtained from the first ingot and the second portion is obtained from the
second ingot.
Since the thickness of the first portion is relatively higher than the thickness of
the second portion and the metal strip specification requires length of the first portion
and the second portion be of equal size, it is important that a size of the first ingot and
the second ingot must be selected in a manner so that the first portion and the second
portion are of desired equal length. In other words, either length or thickness of the
12
second ingot is appropriately determined to fabricate the metal strip of desired
specifications.
If a volume of the first ingot before the rolling operation is Volume1i= t1iw1l1i;
and
a volume of the first ingot after the rolling operation is Volume1f= t1fw1l1f;
wherein,
t1i – thickness of the first ingot before the rolling operation;
w1 – width of the first ingot before and after the rolling operation;
l1i – length of the first ingot before the rolling operation;
t1f – thickness of the first ingot after the rolling operation;
l1f – length of the first ingot after the rolling operation;
Since there is no loss of mass during the rolling operation, it can be derived that:
volume of the first ingot before the rolling operation is = volume of the first
ingot after the rolling operation; That is to say,
Volume1i= Volume1f
Or t1iw1l1i= t1fw1l1f;
Or t1il1i= t1fl1f
Or l1f = (t1i *l1i)/t1f - equation 1
In a similar manner, if a volume of the second ingot before the rolling
operation is Volume2i = t2iw2l2i;and
a volume of the second ingot after the rolling operation is Volume2f = t2fw2l2f;
wherein,
t2i – thickness of the second ingot before the rolling operation;
w2 – width of the second ingot before and after the rolling operation;
l2i – length of the second ingot before the rolling operation;
t2f – thickness of the second ingot after the rolling operation;
l2f – length of the second ingot after the rolling operation;
Since there is no loss of mass during the rolling operation, it can be derived that:
13
volume of the second ingot before the rolling operation is = volume of the
second ingot after the rolling operation; That is to say,
Volume2i= Volume2f
Or t2iw2l2i= t2fw2l2f;
Or t2il2i= t2fl2f - equation 2
Further, as discussed above, the length of the first portion and the second portion of
the metal strip is equal. That is to say, the length of the post-rolling form of the first
ingot is equal to the length of the post-rolling form of the second ingot.
Or l1f should be equal to l2f
l1f = l2f
Thus, referring to the equation no 2;
t2i * l2i = t2f * l1f
Since l1f = (t1i *l1i)/t1f - see equation 1
Or t2i * l2i = t2f * (t1i *l1i)/t1f
Or l2i = (t2f/t2i )* (t1i *l1i)/t1f
Therefore, if the rolling will start with a first ingot having specification as t1i=1m,
l1i=1m length to achieve the post-rolling thickness t1f=0.27mm for the first ingot and
the post rolling thickness t2f=0.135mm for the second ingot, then
l2i = (0.135 mm/t2i mm)*(1000 mm*1000 mm/0.27 mm)
l2i = (0.5*1000*1000/t2i) mm
Thus, for the predetermined specifications of the pre-rolling forms of the first ingot,
the first thickness of the first portion, and the second thickness of the second portion,
a relation can be derived between the pre-rolling length and the pre-rolling thickness
of the second ingot.
14
Figure 3A illustrates an exemplary perspective view of the metal strip formed
from the first ingot and the second ingot in accordance with an embodiment of the
present disclosure. The metal strip includes the first portion of the first thickness t1
and the second portion of the second thickness t2. Figure 3B illustrates an exemplary
cross-sectional view of the metal strip formed from the first ingot and the second ingot
in accordance with an embodiment of the present disclosure.
Figure 4 illustrates exemplary steps of a method for fabricating the metal strip
in accordance with an embodiment of the present disclosure. The metal strip is
adapted to be used for manufacturing the heat exchanger tube comprising a plurality
of heat exchanging channels and a wall folded around the plurality of heat exchanging
channels. The plurality of heat exchanging channels are made from a second portion
of a second thickness of a metal strip and the wall is made from a first portion of a first
thickness of the metal strip.
At step 402, a first volume of the first portion and a second volume of the second
portion is computed in accordance with predetermined requirements of the heat
exchanger tube.
At step 404, an initial length and an initial thickness of a first ingot before
performing a rolling operation in accordance with the first volume of the first portion is
determined. The first ingot after performing the rolling operation thereupon is
transformed into the first portion in such a way that a width of the first ingot after
performing the rolling operation is substantially equal to a width of the first portion of
the metal strip.
At step 406, at least one relation between an initial length and an initial
thickness of a second ingot is derived. The at least one relation is dependent on the
initial length of the first ingot, initial thickness of the first ingot, the first thickness of the
first portion and the second thickness of the second portion. The second ingot after
performing the rolling operation thereupon is transformed into the second portion in
such a way that a width of the second ingot after performing the rolling operation is
substantially equal to a width of the second portion.
15
At step 408, the rolling operation on the first ingot and the second ingot is
performed.
At step 410, first ingot and the second ingot are pressed against each other at
a predetermined temperature upon completion of the rolling operation to fabricate the
single metal strip comprising the first portion of the first thickness and the second
portion of the second thickness.
The present disclosure offers several advantages. Firstly, the second portion,
a relatively thinner portion allows an increase in the number of the corrugated heat
exchanging channels within the heat exchanger tube 100. As a result, a relatively
higher number of corrugated heat exchanging channels can be formed resulting into
an increased efficiency of the heat exchanger tube 100. Further, the present
disclosure facilitates reduction in the usage of the material and thus renders a costeffective
approach for manufacturing the heat exchanger tube 100. Furthermore, the
wall encircling the corrugated heat exchanging channels is relatively thicker which
protects the corrugated heat exchanging channels from corrosion and facilitates in
sustaining burst pressure specifications.
Modifications to embodiments of the present disclosure described in the
foregoing are possible without departing from the scope of the present disclosure as
defined by the accompanying claims. Expressions such as “including”, “comprising”,
“incorporating”, “have”, “is” used to describe and claim the present disclosure are
intended to be construed in a non-exclusive manner, namely allowing for items,
components or elements not explicitly described also to be present. Reference to the
singular is also to be construed to relate to the plural.