CONDENSER FOR AIR CONDITIONING SYSTEM
TECHNICAL FIELD
The present subject matter, in general, relates to a condenser for an Air conditioning
system and in particular, relates to providing a plurality of tubes with a plurality of flow
channels in condensers to obtain higher performance and weight reduction of a condenser
operating in an air conditioning system.
BACKGROUND
In an air conditioner the main function of condenser is to supply refrigerant fluid to
evaporator passing through receiver drier that provides cooling effect inside the designed
space for human comfort. For an automobile air conditioning system, a compact, lightweight,
high thermal performance and robust condenser is required. The growing demand for
efficient condensers with variable performance capacity designed under very short time is a
big challenge. To meet these demands, the general trend is to change the size of the
condenser or the fin and tube completely to attain the desired performance.
Hence, there exists a need for a condenser in air conditioning system which is
efficient, lightweight, compact, and cost effective and which can be efficiently employed in
automobile as well as domestic applications.
SUMMARY
The present invention relates to a condenser for an air conditioning system. The
condenser comprises a core having a plurality of tubes. The plurality of tubes comprising a
plurality of first tubes, a plurality of second tubes, a plurality of third tubes and a plurality of
fourth tubes. The plurality of first tubes, the plurality of second tubes, the plurality of third
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tubes and the plurality of fourth tubes comprises a plurality of flow channels respectively in
the longitudinal direction of the tubes for fluid flow. Further, the size of flow channels of the
plurality of second tubes is greater than size of flow channels of the plurality of first tubes,
size of flow channels of the plurality of third tubes is greater than size of flow channels of the
plurality of second tubes, size of flow channels of the plurality of fourth tubes is greater than
size of flow channels of the plurality of third tubes.
In an embodiment, the plurality of first tubes comprises 5 tubes, the plurality of
second 7 tubes comprises tubes, the plurality of third tubes comprises 10 tubes and the
plurality of fourth tubes comprises 16 tubes.
In another embodiment, each of the plurality of first tubes comprises 14 flow
channels, each of the plurality of second tubes comprises 12 flow channels, each of the
plurality of third tubes comprises 10 flow channels and each of the plurality of fourth tubes
comprises 8 flow channels.
In yet another embodiment, the core comprises a plurality of fins inserted alternately
between the pluralities of tubes.
In yet another embodiment, the length and outer perimeter of all the tubes of the
plurality of tubes is same.
In yet another embodiment, the core has a constant size, length being 398 mm, height
being 338 mm and depth being 12 mm.
In yet another embodiment, the condenser comprises a first header and a second
header positioned vertically to support the core from both sides.
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In yet another embodiment, the condenser comprises a pair of inlet outlet pad
configured for fluidly connecting an inlet pipe and an outlet pipe with the first header and the
second header respectively.
In yet another embodiment, the condenser comprises a receiver drier tank for
receiving refrigerant from the second header.
In yet another embodiment, the first header and the second header are configured to
enable refrigerant flow.
BRIEF DESCRIPTION OF DRAWINGS
The foregoing and further objects, features and advantages of the present subject
matter will become apparent from the following description of example 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
limiting of its scope, for the subject matter may admit to other equally effective
embodiments.
Figure 1 illustrates a perspective view of a condenser 100 employed in automobiles
as well as domestic air conditioning system in accordance with the present subject matter.
Figure 2 illustrates a cross-sectional view of a first tube 104 depicting its internal
structure in accordance with an embodiment of the present subject matter.
Figure 3 illustrates a cross-sectional view of a second tube 106 in accordance with an
embodiment of the present subject matter.
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Figure 4 illustrates a cross-sectional view of a third tube 108 in accordance with an
embodiment of the present subject matter.
Figure 5 illustrates a cross-sectional view of a fourth tube 110 in accordance with an
embodiment of the present subject matter.
Figure 6 illustrates a front view of the condenser 100 depicting flow of refrigerant in
accordance with an embodiment of the 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.
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 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 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” when used in this
specification, specify the presence of stated features, integers, steps, operations, elements,
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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 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 what is shown.
The present invention is aimed at providing a condenser with multiple tubes having
multiple flow channels. The present subject matter allows variable performance
specifications of condenser to be selected under a very less effort towards entire design and
development of the condenser. The condenser uses four different types of micro-tubes of
same height and external perimeter with varying internal structure and free flow area to attain
different required specifications without altering the structure of core and other components
like headers, inlet outlet pads etc. The invention uses different flow passes and different tubes
to obtain a required cooling capacity that can be used well in refrigerant air conditioning
system in automobile as well as domestic applications. By keeping the same tube height and
length with different internal structure of tubes and rest of the components of condenser
same, the cost of product development is reduced to a great extent. Hence it leads to a highly
economic design.
Refer Figure 1 illustrating an aluminium condenser 100 used in automobiles as well
as domestic air conditioning systems in accordance with an embodiment of the present
subject matter. For example, and by no way limiting the scope of the subject matter, the
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condenser 100 of the present subject matter is fabricated using a plurality of components. The
components of the condenser 100 include, but are not limited to a core 102, a first header
122, a second header 124, a pair of inlet outlet pad 126 and a receiver drier tank 128. Further,
the core 102 comprises a plurality of tubes and a plurality of fins 120 inserted alternately
between the pluralities of tubes. The first header 122 and the second header 124 are
positioned vertically to support the core 102 from both sides and configured to enable
refrigerant flow. The pair of inlet outlet pad 126 is configured for fluidly connecting an inlet
pipe and an outlet pipe (not shown in Figure) with the first header 122 and the second header
124 respectively. The receiver drier tank 128 is provided for receiving refrigerant from the
second header 124 and to allow refrigerant flow to the evaporator.
The manufacturing procedure of the condenser 100 includes furnace assembled
brazing of aluminium parts. The plurality of tubes is formed through the extrusion process in
high pressure aluminium injection moulding machines. The plurality of tubes is cut to length
from long rolls after straightening in cutter machines. The cutting is done with low carbon
high speed stainless steel cutter to avoid bur and deformation of plurality of tubes. The cut to
length tubes are palletized in tube tray to be used in core for the condenser. The plurality of
fins 120 is made from thin strips of aluminium coiled in large rolls. The strip is made from
aluminium moulds passed through high pressurized fin rollers. Further, cladding material is
added in both sides of fins. The fin thickness is constantly measured in computerized system
to obtain a uniform thickness. The hot rolling process with required cooling oil and
distributed multi stage pulley rollers are used to get a perfect fin raw material. Required
length of the plurality of fins 120 is obtained from fin cutter machine. Fin is straightened in a
strained pulley system before the cutting of louvers. Dies are used to cut louvers on fin strips
with a high pressure cast iron die. The cut length is pressurized to form louvers with required
pitch. Then the required fin length is cut and kept in tray for core formations.
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The parts are cleaned properly in washing plant. Initially the parts are cleaned in hot
water for five minutes. Than subsequently it is cleaned in alkaline and plain water for ten to
fifteen minutes. After cleaning of parts it is dried in a hot oven to eliminate moisture and
other contaminants from surfaces. The cleaned parts packed properly and sent to assembly
area for making condenser. The plurality of fin 120 and the plurality of tubes along with the
first header 122 and the second header 124 are assembled in core builder machine. The
procedure of making core 102 can be of three types i.e. manual, semi-automatic and
automatic. In manual core builder operation the operator builds the core in the core builder
bed. The operator has to set the required no of tubes and fins alternatively by counting. Then
the first header 122 and the second header 124 are inserted with appropriate mallet strokes. In
a semi-automatic core builder machine the plurality of tubes get settled in tube pockets.
When button is pressed the plurality of tubes get aligned with the fins space in between. The
operator has to put fins in between the plurality of tubes by hand. Then the first header 122
and the second header 124 are put on both the sides of the core 102 with mild strokes of
mallet. In an automated core builder machine the operator has to load fin and tube trays in
respective places. The pre-programmed machine for a particular core size of condenser is
selected for building the core. Sensors monitor and provide feedback to load fins and tube in
input sluts. The tube and fin is loaded in core bed to form the core. The first headers 122 and
the second header 124 are pressed to main core 102 with pneumatic cylinders of core builder
machine. A robotic hand moves the core forward direction to be taken by the operator.
In an embodiment, Figure 2, Figure 3, Figure 4 and Figure 5 illustrate a plurality of
first tubes 104, a plurality of second tubes 106, a plurality of third tubes 108 and a plurality of
fourth tubes 110 respectively. Further, the plurality of first tubes 104, the plurality of second
tubes 106, the plurality of third tubes 108 and the plurality of fourth tubes 110 include a
plurality of flow channels 112, 114, 116 and 118 respectively in the longitudinal direction of
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the tubes for fluid flow. Furthermore, size of the flow channels of the plurality of second
tubes 106 is greater than size of flow channels of the plurality of first tubes 104, size of flow
channels of the plurality of third tubes 108 is greater than size of flow channels of the
plurality of second tubes 106, size of flow channels of the plurality of fourth tubes 110 is
greater than size of flow channels of the plurality of third tubes 108.
In a preferred embodiment, the plurality of first tubes 104 comprises 5 tubes, the
plurality of second tubes 106 comprises 7 tubes, the plurality of third tubes 108 comprises 10
tubes and the plurality of fourth tubes 110 comprises 16 tubes. Further, each of the plurality
of first tubes 104 comprises 14 flow channels 112, each of the plurality of second tubes 106
comprises 12 flow channels 114, each of the plurality of third tubes 108 comprises 10 flow
channels 116 and each of the plurality of fourth tubes 110 comprises 8 flow channels 118.
Referring Figure 1 and Figure 6 in accordance with an embodiment of the present
subject matter, the core 102 is formed with thirty eight tubes in different pass structure.
Thirty nine fins 120 are inserted alternatively in between tubes. The plurality of tubes are
inserted into the first header 122 and the second header 124 at its opposite ends. The pair of
inlet outlet pads 126 is connected in headers. The refrigerant from circuit flows into the first
header 122 and is distributed evenly on the first pass tubes, i.e. the plurality of fourth tubes
110 and then is mixed in second header 124 before the first baffle. The mixed refrigerant is
again evenly distributed and flows in second pass tubes, i.e. the plurality of third tubes 108.
Then refrigerant is mixed in first header 122 before second baffle and flows through third
pass, i.e. the plurality of second tubes 106 after evenly distributions. The refrigerant is mixed
in second header 124 and then flows in to the receiver drier tank 128. It gets dried to form
liquid and is passed in to fourth pass, i.e. the plurality of first tubes 104 after even
distributions. Finally the mixed fluid is passed to outlet pad of the pair of inlet outlet pad 126
after mixing in first header 122.
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Further, the condenser is comprised of tubes (Figure: 2, 3, 4 and 5) of same height
and same outer perimeter though the other parameters of tube like hydraulic diameter,
weight, heat transfer area and fluid flow area changes referred Table 1:
The tubes in core 102 (Figure: 1) of condenser 100 have same outer perimeter of
25.71mm with different internal perimeter and number of holes. First tube 104, second tube
106, third tube 108 and fourth tube 110 has 14, 12, 10 and 8 flow channels respectively with
internal perimeter of 59.638mm, 53.98mm, 48.12mm and 42.69mm respectively. The tubes
have weight of 0.0285kg/m, 0.0268kg/m, 0.0252 kg/m and having free flow area of
7.115mm, 7.717mm, 8.223 mm and 8.922 mm respectively.
As can be seen from above, all condenser uses 42% of tubes in first pass, 26% number
of tubes in second pass,19% number of tubes in third pass and 13% number of tubes in fourth
pass as per Table 2:
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In an embodiment, the condenser uses 16 numbers of tubes in first pass of fourth tube
110, 10 numbers of third tubes 108 in second pass, 7 numbers of second tubes 106 in third
pass and 5 numbers of first tubes 104 in fourth pass. All the passes have a decreasing trend in
hydraulic diameter as per Table 2.
The condenser has a range of performances referred Table 3, like thermal
performances, fluid flow parameters with a constant fixed core size. The core has a constant
length of 398mm, height of 338mm and depth of 12mm. The change in performance can be
obtained by changing said tube types in different pass structures.
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The use of different combination of tubes provides user to get 2-4% higher
performance to weight ratio than conventional type of condenser design. Given below is
graph depicting condenser performance to weight ratio:
The excess free flow area of a tube in a compact heat exchanger leads to less pressure
resistance and more heat transfer area leads to high heat dissipation capacity. The present
invention provides a very economic and variable performance design.
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An efficient condenser can be obtained through the heat transfer rate optimization and
the present subject matter stands on it. Though it uses a simple heat equation (1) the effect
can be felt very easily. Due to use of plurality of tubes having high heat transfer rate, the
required temperature can be attained through the shorter travel length. The use of required
internal structure of tubes, number of tubes in each passes and pass structure can be
determined according to the specified thermal performance requirement.
where
Q: Heat Transfer U: Total heat transfer coefficient
A: Heat transfer area ΔT: Temperature gradient
The free flow areas of fluid and hydraulic diameter are other critical parameters that
play a vital role in design of a condenser. The more free flow areas and more hydraulic
diameter are required for a low pressure resistance in condenser design. The required number
of tubes having higher free flow area selection depends upon the pressure drop specifications.
The core 102 (Figure 1) plays a vital role during manufacturing of the epitome. The
selected tubes (Figure 2 – Figure 4) are kept in a sequential order. The different band of
condenser is obtained through the selection of number of tubes and type of tubes in each
passes. The epitome highlights the changing of different cross-sections of tubes in different
passes. The free flow areas of fluid and hydraulic diameter are other critical parameter that
plays a vital role in design of a condenser. The more free flow areas and more hydraulic
diameter are required for a low pressure resistance in condenser design. The tube selection in
core of condenser depends upon the pressure drop and heat transfer specifications. The first
tube (Figure 2) having high heat transfer area with low free flow area. This tube (Figure 2)
Q=UAΔT …………………………………………………(1)
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can be used in areas of liquid zone where maximum heat transfer area and lower free flow
area is the best option in condenser. The increase in internal perimeter leads to increase in
contact area between refrigerant fluid and tube surface. Due to increase in contact area heat
transfer area is maximized. If a condenser is made up of only the selected tube it can lead to
obtain a condenser having maximum heat transfer capacity.
Capacity of condenser is affected by two phase behavior of refrigerant fluid. The
middle part of condenser is more exposed to air flow in a system. Two phase zone is good to
be set in these areas to maximize the heat transfer and to optimize performance of condenser.
This zone can be made with moderate thermal and flow pressure drop tubes. Inlet to this zone
of fluid contains in gaseous form or having a mass fraction more than 0.9. It gets cooled and
liquefies to mass fraction of 0.1 or zero. The heat transfer in this region only depends on this
two phase zone can be supplied with tube having medium flow area tube and moderate heat
transfer tubes. A condenser made up of only second tube (Figure 3) will be in the middle
zone of thermal capacity and airflow pressure drop of condensers.
The final pass of a condenser mainly includes the liquid phase of coolant. This phase is the
sub cool zone which has a temperature lower than the boiling temperature at NTP. The third
Tube (Figure 5) is more preferred in this region. The third tube is having moderate transfer
area and more flow area.
The condenser made up of only tube3 is a condenser having moderate heat transfer
capacity and moderate pressure drop. It can be placed in two phase region of condenser. The
fourth tube (Figure 5) is the tube having highest free flow area, hydraulic diameter and
lowest heat transfer area with 8 voids. This tube can be suitable to gas region of condenser.
Condenser made up of these tubes has very less pressure drop and heat transfer.
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In the present condenser 100, tube arrangement in different passes are to be made with
decreasing cross-sectional area or flow parameter or in the decreasing trend of hydraulic
diameter. The first pass of condenser contains more free flow area then second pass and the
fourth pass has a lesser free flow area than second and third pass.
Automobile condensers always required to be lightweight and compact for a better
performance of vehicle. This embodiment provides a perfect solution to keep the weigh
almost constant and to provide different performance. Due to use of micro tubes with varying
free flow area it has a little effect towards the weight of condenser. The use of required
internal structure of tubes with number of tubes in each pass and pass structure can be
determined according to the specified thermal performance requirement. The size of core in
condenser design can be kept constant for attaining this performance. This embodiment is
designed by keeping the fin height and depth constant and other internal parameters may be
altered as per performance requirements. The height and depth is to be selected as per the
tube height and condenser. After setting the required core size core was bounded by wires.
Wire binding is an important process for epitome. In this process proper sized c-clamp are
used before binding the wires. Stainless steel wire is used for binding. It prevents the drop of
fin in furnace. It maintains the core size during brazing of other child parts to condenser.
After binding of wires the core proceeds to next station of TIG welding. In this station the
other cleaned child parts like inlet outlet pipe and mounting brackets are welded to main core.
A TIG welding fixture is used for mounting of core. A skilled operator puts spot welding
marks on both side of condenser. The assembled core is sent to the furnace for brazing. The
core with assembled condition goes through a particulate spray of nucolox flux to lower the
brazing temperature. Then the core is passes through the furnace on belt with a speed of
500mm per minutes. The maximum temperature is raised to 650 degree Celsius. The brazed
condenser is flattened on the flapper plate to avoid any deformation of core. The Inlet and
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outlet pipe are fitted to the condenser. After completion of assembly and brazing the fitment
test is done. After fitment test the condenser is processed through helium leak check. A gross
level of 2 Bar pressure and higher level of 12 Bar helium pressure is inserted into condenser
for a pre calibrated time in a vacuumed chamber. The computerized test setup releases a
sticker mark for the condenser those succeeds the test.
The subject matter described herein is designed by keeping the fin height and depth
constant and other internal parameters may be altered as per performance requirements. The
height and depth is to be selected as per the tube height and condenser.
Although the invention has been described with reference to specific embodiments, this
description is not meant to be construed in a limiting sense. 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.

WE CLAIM
1. A condenser 100 for an air conditioning system, the condenser 100 comprising:
a core 102 having a plurality of tubes;
the plurality of tubes comprising a plurality of first tubes 104, a plurality of
second tubes 106, a plurality of third tubes 108 and a plurality of fourth tubes
110;
the plurality of first tubes 104, the plurality of second tubes 106, the plurality
of third tubes 108 and the plurality of fourth tubes 110 comprising a plurality
of flow channels 112, 114, 116 and 118 respectively in the longitudinal
direction of the tubes for fluid flow such that size of the flow channels of the
plurality of second tubes 106 is greater than size of flow channels of the
plurality of first tubes 104, size of flow channels of the plurality of third tubes
108 is greater than size of flow channels of the plurality of second tubes 106,
size of flow channels of the plurality of fourth tubes 110 is greater than size of
flow channels of the plurality of third tubes 108.
2. The condenser 100 as claimed in claim 1, wherein the plurality of first tubes 104
comprises 5 tubes, the plurality of second tubes 106 comprises 7 tubes, the plurality of
third tubes 108 comprises 10 tubes and the plurality of fourth tubes 110 comprises 16
tubes.
3. The condenser 100 as claimed in claim 1, wherein each of the plurality of first tubes
104 comprises 14 flow channels 112, each of the plurality of second tubes 106
comprises 12 flow channels 114, each of the plurality of third tubes 108 comprises 10
flow channels 116 and each of the plurality of fourth tubes 110 comprises 8 flow
channels 118.