U.S. patent application number 12/669004 was filed with the patent office on 2010-08-05 for refrigeration circuit.
This patent application is currently assigned to INDUSTRIE ILPEA S.P.A.. Invention is credited to Paolo Cittadini.
Application Number | 20100192623 12/669004 |
Document ID | / |
Family ID | 40130806 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100192623 |
Kind Code |
A1 |
Cittadini; Paolo |
August 5, 2010 |
REFRIGERATION CIRCUIT
Abstract
A refrigeration circuit (3) for household appliances comprises a
compressor (4) suitable for compressing a predetermined cooling
fluid and for allowing the circulation thereof within said circuit
(3), a first heat exchanger (5) or condenser in fluid communication
with the compressor (4) for allowing the cooling and the consequent
condensation of the cooling fluid going through, and a second heat
exchanger (7) or evaporator in fluid communication with the first
exchanger (5) through a circuit with a special device (6) suitable
for decreasing the pressure of the cooling fluid at a space (2) to
be cooled (normally inside the refrigerator). The second exchanger
(7) allows the cooling fluid to evaporate, absorbing heat, thus
cooling the space (2) and returning through the tubing (17) to the
compressor (4). The cooling fluid circulates from the compressor
(4) towards the first exchanger (5), from the latter towards the
second exchanger (7) and then returns to the compressor (4) for a
subsequent cycle. At least one of the heat exchangers (5, 7)
comprises a plastic tubing (9), at least a portion whereof exhibits
such corrugated profile as to impart flexibility thereof and/or
increase the thermal exchange surface.
Inventors: |
Cittadini; Paolo; (Luvinate,
IT) |
Correspondence
Address: |
Pearne & Gordon LLP
1801 East 9th Street, Suite 1200
Cleveland
OH
44114-3108
US
|
Assignee: |
INDUSTRIE ILPEA S.P.A.
I-21023 MALGESSO (VARESE)
IT
|
Family ID: |
40130806 |
Appl. No.: |
12/669004 |
Filed: |
July 8, 2008 |
PCT Filed: |
July 8, 2008 |
PCT NO: |
PCT/IB08/01795 |
371 Date: |
March 25, 2010 |
Current U.S.
Class: |
62/498 |
Current CPC
Class: |
F28F 9/0246 20130101;
F28F 1/08 20130101; F25B 41/40 20210101; F25B 39/00 20130101; F28F
21/062 20130101 |
Class at
Publication: |
62/498 |
International
Class: |
F25B 1/00 20060101
F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2007 |
IT |
MI2007A001419 |
Claims
1-53. (canceled)
54. Refrigeration circuit (3) for household appliances, in
particular household appliances for cooling such as refrigerators,
freezers and the like, comprising: at least a first heat exchanger
(5), suitable for being placed in fluid communication with a
compressor (4), for allowing the cooling of a cooling fluid
substantially in liquid phase in crossing; at least a second heat
exchanger (7) in fluid communication with said first exchanger (5)
and active at a space (2) to be cooled, said second exchanger (7)
allowing the cooling fluid at least partly in gaseous phase to
absorb heat cooling said space (2), the cooling fluid circulating
from the first exchanger (5), towards the second exchanger (5) and
thus being directable to a compressor (4) for a subsequent cycle;
and preferably a lamination device (6) arranged between said first
(5) and second (7) heat exchanger for generating an expansion of
said cooling fluid, at least one of said first (5) and second (7)
heat exchanger comprising at least one flexible tubing (9),
characterised in that at least a portion of said tubing (9) is a
flexible corrugated tubing adaptable to be arranged according to a
plurality of different configurations by simply bending tubing (9)
without intervening plastically and irreversibly deforming tubing
(9) itself.
55. Refrigeration circuit (3) according to claim 54, characterised
in that said tubing (9) is made of a material not permeable to said
cooling fluid circulating in said tubing (9), preferably a material
not permeable to cooling fluids selected from the group comprising
HC, HFC or mixtures thereof.
56. Refrigeration circuit (3) according to claim 54, characterised
in that said tubing (9) comprises at least one layer (S1) of
plastic material, preferably polyamide and even more preferably
polyamide 6-6 or polyamide 6-12.
57. Refrigeration circuit (3) according to claim 54, characterised
in that said tubing (9) is made of a material not permeable to
humidity to prevent external humidity from penetrating in said
tubing (9) containing said circulating cooling fluid.
58. Refrigeration circuit (3) according to claim 54, characterised
in that said tubing (9) comprises at least two superimposed layers
(S1, S2) of different materials, preferably both plastic materials,
a first layer (S1) of a material impermeable to the cooling fluid
and/or to incondensable gases, a second layer (S2) impermeable to
humidity.
59. Refrigeration circuit (3) according to claim 58, characterised
in that said first layer (S1), preferably external, is made of a
material selected from the group comprising polyamides 6; 6-6;
6-12; 11; 12 and the respective copolymers, preferably polyamide
6-6 or polyamide 6-12, and that said second layer (S2), preferably
internal, is made of a material selected from the group comprising
olephinic copolymers, low density polyethylene modified with maleic
anhydride and polypropylene, preferably modified with maleic
anhydride, type BYNEL 4206 by DuPont.
60. Refrigeration circuit (3) according to claim 54, characterised
in that said tubing (9) is defined by at least two, preferably a
plurality of, modular tube segments connected to each other by
respective junction elements for obtaining a fluid-dynamic
continuity between said tube segments.
61. Refrigeration circuit (3) according to claim 54, characterised
in that at least one of said heat exchangers (5, 7) is entirely
defined by said tubing (9), said tubing (9) being in particular
entirely provided with such corrugated profile as to impart
flexibility thereto.
62. Refrigeration circuit (3) according to claim 54, characterised
in that at least one of said heat exchangers (5, 7) is entirely
defined by said tubing (9), said tubing (9) consisting of portions
of rectilinear tube spaced by portions of tube having corrugated
profile so as to impart flexibility thereto for example in portions
where it is necessary to make the bending zones, keeping the other
zones stiff and self-supporting.
63. Circuit according to claim 54, characterised in that the tubing
(9) exhibits a non-circular cross section and comprises at least a
portion (44), for example flat, suitable for coupling with a
surface of a household appliance at least partly counter-shaped,
for example flat, to said portion (44).
64. Refrigeration circuit according to claim 54, characterised in
that a wall thickness (S) of the tubing (9) is comprised within a
range between 0.3 mm and 2 mm and preferably between 0.6 mm and 1.2
mm.
65. Circuit according to claim 58, characterised in that the
thickness of the first layer (S1) of material impermeable to the
cooling fluid is comprised between 60% and 80% and preferably it is
about 70% of the total thickness (S) of the tubing (9), the
thickness of the second layer (S2) of material impermeable to
humidity is comprised between 20% and 40%, and preferably it is
about 30% of the total thickness (S) of the tubing (9).
66. Refrigeration circuit according to claim 65, characterised in
that the thickness of the first layer (S1) is comprised between 0.2
mm and 0.4 mm, the thickness of the second layer (S2) being
preferably comprised between 0.4 mm and 1 mm.
67. Circuit according to claim 54, characterised in that the tube
thickness (10) of the first exchanger or condenser (5) is such as
to allow a burst resistance of 36 bar, and it is preferably
comprised between 0.8 and 1.4 mm, preferably with maximum outer
diameter of 7 mm.
68. Circuit according to claim 54, characterised in that said
tubing (9) exhibits a maximum outer diameter (Dmax) comprised
between 6 mm and 14 mm and preferably within the range of 8 mm-11
mm.
69. Circuit according to claim 54, characterised in that said
tubing (9) of the first exchanger or condenser (5) exhibits a
maximum outer diameter (Dmax) comprised between 5 mm and 10 mm and
preferably within the range 6 mm-7 mm.
70. Circuit according to claim 54, characterised in that said
tubing (9) is sized for allowing, in standard operating conditions
of the circuit, operating at a velocity of the cooling fluid of at
least 4 m/sec.
71. Circuit according to claim 54, characterised in that said
tubing (9) is sized for working with inside pressures within a
range from 0.3 to 12 bar and preferably in a range of temperatures
between -30.degree. and +70.degree. C.
72. Circuit according to claim 54, characterised in that it may
comprise a filter (18), in particular arranged between the first
exchanger (5) and the lamination device (6), for removing any
humidity present in the circuit, said removal being carried out for
example by a gel capable of absorbing humidity.
73. Circuit according to claim 72, characterised in that the body
of the filter 18 consists of the tube wall (10b) coming from the
first exchanger or condenser (5), said wall being suitably
enlarged, for example during corrugation, to contain the gel so as
to create a filter integral with the tube (10b).
74. Circuit according to claim 73, characterised in that the filter
consists of a body obtained by corrugation from the tube (10b)
closed by a connector, for example, welded thereto by ultrasounds
or glued, which couples to the capillary (21).
Description
[0001] The present invention relates to a refrigeration
circuit.
[0002] More in particular, the present invention relates to a
refrigerating apparatus, preferably of the type used in household
appliances such as refrigerators, freezers, deep-freezers, iceboxes
and the like. The invention is likewise and also applicable, in a
totally similar manner, also to household appliances for
conditioning.
[0003] It is known that refrigerators of the traditional type and
similar refrigerating apparatus, comprise a refrigeration circuit
wherein a refrigerating means is used suitable for subtracting heat
from a closed space to be cooled to a predetermined temperature,
such as the interior of the refrigerator or freezer, transferring
it towards the outer warmer space. The above refrigeration circuit
is a closed circuit wherein a compressor, a condenser, a lamination
or capillary device and an evaporator operate in a sequence
according to known operating modes. In particular, the
refrigerating means is a low boiling point substance suitable for
undergoing a passage of state from liquid to vapour by expansion
with the effect of subtracting heat to the ambient it is in contact
with, and afterwards a reverse passage from vapour to liquid,
during the circulation thereof within the refrigeration circuit.
Focusing on the thermal exchanges of the refrigerating means with
the air of the closed ambient to be refrigerated and of the outer
ambient, such exchange takes place by means of metal coils wherein
the refrigerating means is conveyed so as to increase the thermal
exchange surface between the refrigerating means and the air
itself.
[0004] The metal coils used for such function are generally
obtained starting from a continuous metal tube (steel, aluminium or
copper) which is suitably bent multiple times for following a
profile of a useful surface intended for thermal exchange. Such
useful surface is located at the back of the refrigerator in the
case of the condenser, whereas in the case of the evaporator, the
arrangement of the coils depends on the model of refrigerating
apparatus or refrigerator, freezer or combined, and it concerns one
or more walls inside the refrigerator itself. In particular, it is
known to position the coil of the evaporator at the inside bottom
wall and/or at the inside side walls of the refrigerator, or even
at one or more shelves provided inside the refrigerator. According
to the arrangement inside the refrigerators and on the results to
be achieved, the evaporators may be static (Wire On Tubes or Tubes
On Plates) or dynamic (No Frost). In any case there is a pack
consisting of steel or aluminium or copper tubes suitably bent and
welded or otherwise connected to other metal bodies that increase
the exchange surface thereof (metal wires in the case of WOT, metal
sheets in the case of TOP and aluminium sheets in the case of
NF).
[0005] The bending of the metal tube for making the evaporator coil
is carried out according to different methods depending on the
geometry of the surface whereon the coil itself is intended to be
active. In fact, the bending of the metal tube is generally carried
out by special tube bending machines prior to the final
installation of the coil, and it must therefore be arranged in a
differentiated manner according to the final geometry of the coil.
The bending must be made so as to prevent chocking or section
variations in such zones.
[0006] Disadvantageously, this implies poor operating flexibility,
related to the impossibility of providing for a standard process
for obtaining the coil that will remain unchanged only for the
refrigerators of the same model or same range. Such disadvantage
causes the drawback of implying different production processes that
strongly negatively affect the manufacturing times and as a direct
consequence, imply high production costs.
[0007] Moreover, the storage processes are damaged as they must
provide for the storage of different types of coils, each intended
to be mounted only on predetermined thermal exchange surfaces
having predetermined geometry.
[0008] Moreover, the manufacture of the above coils starting from
metal tubes implies further production costs related to the
procurement of raw materials (metal), to any processing of raw
materials themselves, as well as to the complex operations for
manufacturing the metal tube and the bending thereof for defining
the end profile of the coil. In fact, the metal tube is obtained by
welding a suitable formed flat sheet, and such process is very
expensive and complex, as it must also be carried out in an
accurate manner to prevent leaks of cooling fluid which would
irreparably damage the refrigerator in very short times, with
serious economic consequences for the manufacturer and for the
environment (such fluids are often polluting). Moreover, the metal
tube is supplied in rolls to the manufacturers of evaporators and
is thus unrolled, straightened, the diameter thereof is checked and
then it is suitably bent multiple times at 180.degree. in
alternating direction to obtain the desired thermal exchange
surface, and finally coupled to metal bodies shaped as fins or
straight metal wires, suitable for facilitating the thermal
exchange with the ambient to be cooled. The coupling with such
metal wires is mostly made by spot welding (WOT) or by the
introduction of the tube bundle into special slits obtained in the
aluminium fins (NF). These are mainly manual operations that can be
automated only to the disadvantage of the flexibility of the
production line and moreover the need of making welding spots in
the WOT and that of welding the inlet and outlet tubes of the
evaporator to the remaining parts of the circuit, forces to
chemically treating and then coating or galvanically treating all
the surface of the part, so as to make it corrosion resistant. The
complexity of the production process of the metal coils of known
type and described above is clear. Moreover, the presence of the
metal coil and of the metal bodies greatly increases the overall
mass and as a consequence, the weight of the household
appliance.
[0009] Also the above further chemical treatments are expensive and
very polluting (we may consider for example, nickel-plating): since
after such treatments, sludge containing heavy metals is generated
which must be disposed of to special collection centres for highly
toxic waste.
[0010] A refrigerator is known from patent EP1479987, comprising an
evaporator equipped with a flexible tube. The flexible tube, made
of plastic material, is cylindrical and wound spiral-wise around
respective supports and can be elongated or packed for varying its
configuration based on a part of the refrigerator wherein a cooling
action is desired.
[0011] The flexibility of the tube, however, is limited and the
same may be deformed substantially along a single direction around
which the coils are wound.
[0012] Moreover, a refrigerator is known from patent KR 20010094016
provided with an evaporator made of plastic material.
[0013] To prevent the known problems of frosting, such evaporator
(with rigid structure and shaped as a flat surface defining the
cooling tubes and the fins) exhibits a coating of electrically
conductive paste to be connected to an external metal conductor and
a further external insulating layer of plastic as well. With
reference to the European intellectual property mentioned above,
disadvantageously, the adoption of a similar plastic tube having
perfectly cylindrical shape, does not allow optimum thermal
exchange by the cooling fluid circulating therein. Moreover, the
above cylindrical tube wound spiral-wise is suitable for being
elongated or packed along a predetermined direction, however it
does not exhibit high properties of flexibility in any direction,
and in particular in the case of very marked bending such as narrow
radius bending generally required in making flat coils for
refrigerators.
[0014] In detail, such intellectual property does not ensure high
performance as regards the operating flexibility and adaptability
of the heat exchanger geometry as is currently required on the
market.
[0015] Also the Korean document makes no mention of the problems of
adaptability and modularity of the heat exchanger.
[0016] The above patent also refers to the making of a layer of
conductive material comprised between an internal plastic material
in contact with the cooling fluid and an external coating material
the nature and application technology whereof are absolutely not
described.
[0017] In the above patents in any case one of the most important
problems was not solved: how to prevent gas leaks through the
evaporator or condenser surfaces or through the connecting devices
of such apparatus with the other components of the refrigerating
circuit. The perfect seal to any gas leaks through the
refrigeration circuit is a necessary condition for a is
refrigerator to work properly and for several years. The making of
a flexible tube is also known from patent EP 918182 for conveying a
coolant in an air conditioning system.
[0018] The structure described by such intellectual property in any
case appears very complex as it envisages a first inner layer and
an outer layer of plastic material coupled by the adoption of an
intermediate layer.
[0019] A cover is provided outside the tubes of plastic material,
consisting of synthetic fibres in turn protected by a further outer
sheath.
[0020] Such a complex structure makes the tubing described in the
European intellectual property substantially unsuitable for use
within heat exchangers that must attain the passage of the heat
itself between the cooling fluid and the external ambient.
[0021] On the other hand, the tube described in the above European
patent exclusively serves for carrying such fluid and not for a
thermal exchange with the ambient, which takes place in different
and not described structures.
[0022] Hereinafter it is also noted that tubing of plastic material
for heat exchangers is known for applications totally different
from refrigeration circuits for household appliances.
[0023] In particular, such heat exchangers are designed for the
most varied applications in the automotive field. For example,
exchangers are known according to patent US2007/0289725 and U.S.
Pat. No. 5,706,864.
[0024] However, it should be noted that the devices according to
one or the other of the indicated patents cannot be used in
refrigeration circuits according to the present invention since
their field of application makes them totally unsuitable for
carrying the refrigerating gases commonly used in household
appliances and also they are not suitable for allowing thermal
exchange in conditions of liquid phase and gaseous phase of the
fluid circulating therein. These applications typically use only a
fluid that must work at operating temperatures and pressures
totally different from those normally used in a refrigerating
circuit for household appliances. In this respect, using the one or
the other of the devices described in the two patents mentioned
above is unconceivable since the man skilled in the art would
immediately recognise a plurality of difficulties of adaptation
related to the leaks of refrigerating material, to the insufficient
thermal exchange, to the impossibility of a correct velocity of the
fluid inside the tubing, etc.
[0025] The technical task of the present invention is to provide a
refrigeration circuit and household appliance which should be free
from the drawback mentioned above.
[0026] Within such technical task, an object of the invention is to
provide a household appliance for cooling whose production should
imply a high operating flexibility.
[0027] A further object of the invention is to provide a household
appliance for cooling which should be made in a simple, inexpensive
and more environment-friendly way.
[0028] A further object of the invention is to provide a household
appliance for cooling which should be made in a more automated and
thus reliable manner, with special reference to the above welding
operations, eliminating manual welding that are presently carried
out for connecting the various circuit devices to one another.
[0029] A further object of the invention is to combine, where
possible, the materials used to make the is various cooling system
parts (presently copper, aluminium and steel), replacing them with
plastic materials compatible and recyclable without separation, so
as to simplify the storage processes of the parts themselves.
[0030] It is also an object of the invention to provide a household
appliance for cooling which should have smaller mass and
weight.
[0031] It further is an object of the invention to provide a
household appliance for cooling which should exhibit high
flexibility in a plurality of directions, and in particular in the
case of small bending radiuses.
[0032] These and yet other objects, as will appear hereinafter in
the present description, are substantially achieved by a household
appliance for cooling having the features respectively expressed in
claim 1 and/or in one or more of the dependent claims.
[0033] The invention results from the observation that the slow
step phase of the thermal exchange process on the current
refrigerating circuits is not heat conduction through the thickness
of the exchanger tube, but thermal exchange by natural or forced
convection (no frost) between the air and the surface is of the
tube itself.
[0034] So far, the exchangers for household appliances have always
been made of metal material (even very expensive like copper), to
increase the thermal conductivity of the tube. The invention, on
the contrary, uses a plastic material, less expensive, better
processable, but with lower thermal conductivity, just because the
exchange process is not generated by the thermal conductivity of
the tube.
[0035] This applies to thickness of the plastic tube not larger
than 1.5 mm; in order to improve the thermal exchange of the
circuit it has been thought to intervene in the slow phase of the
process (thermal exchange between tube and air), increasing the
exchange surface with the use of corrugated tube surfaces that with
the same diameter allow 30-50% increase of the exchange surface per
unit of length of the tube.
[0036] A preferred but non-exclusive embodiment of a household
appliance for cooling shall now be illustrate by way of a
non-limiting example according to the present invention and to the
annexed figures, wherein:
[0037] FIG. 1 shows a schematic representation of a refrigeration
circuit according to the present invention, and in particular of
the type with evaporating tubes;
[0038] FIG. 2 shows a perspective view of a portion of the
refrigeration circuit of a household appliance according to the
present invention;
[0039] FIG. 3 shows a partly side and partly dissected
representation of a tube usable in a refrigeration circuit
according to the present invention and according to a first
embodiment;
[0040] FIG. 3a shows a possible version of section of the tube of
FIG. 3;
[0041] FIG. 4 shows a partly side and partly dissected
representation of the detail of FIG. 3 consisting of a double layer
of plastic material suitable for making the tube wall totally
gas-proof according to a different embodiment;
[0042] FIGS. 5 and 6 show two possible sections of a capillary tube
used in the circuit according to the finding;
[0043] FIGS. 7 to 10a show a section of possible embodiments of the
heating means used in the tubing according to the finding;
[0044] FIGS. 11-13 show different embodiments of connectors for
connecting portions of tubing used in the circuit according to the
invention;
[0045] FIGS. 14 and 15 show the coupling between a capillary tube
and tubing according to the present invention;
[0046] FIGS. 14a, 14b and 14c show three possible embodiment
versions of a coupling between capillary and corrugated tube for
thermal exchange and energy recovery;
[0047] FIG. 16 shows the coupling between metal tubing and a
plastic tubing according to the present invention;
[0048] FIGS. 17-19 show the coupling between two end portions of
tubes of plastic material used in the circuit according to the
present invention;
[0049] FIG. 20 shows a possible configuration of coupling between a
tubing and the compressor; and
[0050] FIGS. 21a and 21b show two possible configurations of
engagement between tubing and capillary.
[0051] According to the schematic view of FIG. 1, reference numeral
1 globally indicates a refrigeration apparatus which may be, by way
of an example, a refrigerator, a freezer, a deep-freezer, a
conditioner or any other appliance mainly for household purpose
suitable for cooling a closed ambient, in particular a space 2,
particularly for storing food products or for conditioning a living
room.
[0052] Apparatus 1 comprises a refrigeration circuit 3 object of
the present invention, which is suitable for carrying out a
thermo-dynamic refrigerating cycle and is suitable for conveying a
cooling fluid along a closed path according to an advance direction
indicated with "A" in FIG. 1. The refrigeration circuit 3 works by
a liquid-vapour phase change of the cooling fluid, and comprises a
compressor 4, a condenser 5, a filter 18, a lamination device 6 and
an evaporator 7, besides other optional devices suitable for
improving the yield of the cooling cycle. The detailed operation of
the refrigeration circuit 3 is beyond the contents of the present
invention and therefore, it shall not be described hereinafter in
detail.
[0053] Evaporator 7 defines a first heat exchanger which has the
function of drawing energy in the form of heat from an inner
portion of apparatus 1, and in particular from space 2, and
transferring it to the cooling fluid circulating through evaporator
7. Space 2, which in the case of refrigerators is generally
intended for storing food or in any case perishable food, is
delimitated by walls 8 and is accessible from the exterior of the
apparatus, for example by one or more closing ports.
[0054] More in detail, evaporator 7 comprises a tubing 9 that
extends from a first end 9a, connectable (optionally through
further tubing portions) to the lamination device 6, to a second
end 9b which usually has the function of heat exchanger with the
lamination device 6, connectable (optionally by further tubing
segments as well) to compressor 4. Tubing 9 is intended for
conveying the cooling fluid and allowing transfer of thermal energy
(heat) from space 2 towards the cooling fluid circulating in tubing
9 itself.
[0055] Likewise, condenser 5 comprises a coil 10 which extends from
a first end 10a, connectable to compressor 4, to a second end 10b,
connectable to the lamination device 6 and that usually, contains a
gas filtering element 18. Coil 10 is intended for conveying the
cooling fluid and allowing transfer of thermal energy from the
cooling fluid circulating in coil 10 itself towards an external
ambient wherein the apparatus is placed or towards a hot
source.
[0056] Unless otherwise stated in the following description, coil
10 may consist of a tubing similar to tubing 9 mentioned above but
with a smaller diameter, due to the highest operating pressures or,
as an alternative, it maybe made by a metal tubing as it commonly
happens at present in the refrigerating circuits on the market.
[0057] According to the regulations in force, the refrigerating
fluid belongs to classes HFC (hydrofluorocarbons), HC
(hydrocarbons) or mixtures thereof. Preferably, the cooling fluid
used is an aliphatic hydrocarbon such as isobutane, R600a.
[0058] According to the configuration shown in FIG. 1, both tubing
9 and coil 10 are arranged according to respective winding paths
(which by way of an example may form 180 degree deflections;
however, other equivalent operating geometrical configurations may
be taken, as better explained hereinafter), so as to substantially
bend on themselves for taking a compact configuration suitable for
obtaining an efficient thermal exchange. FIG. 2 shows an example of
embodiment of tubing 9 of evaporator 7, which is applied to a
(bottom, or intermediate supporting) surface 11 of a refrigerator
and is schematised with a thread-wise pattern to highlight the
winding path of tubing 9 itself. More in detail, tubing 9 is built
in a thickness of surface 11 so as to be steadily associated
thereto but as an alternative, of course it may be positioned also
inside a wall of the apparatus being buried into the same.
Advantageously, tubing 9 is made of synthetic and preferably
plastic material, so as to simplify the production processes and
reduce the overall weight of the circuit.
[0059] Tubing 9 shall exhibit at least two peculiarities: it shall
be not permeable to the cooling fluid that flows therein to prevent
contaminations of the environment and loss of refrigerating
capability of the circuit, and it shall also ensure humidity/water
impermeability to prevent infiltrations (and consequent freezing)
of the latter into the refrigeration circuit; moreover, the tubing
shall also ensure impermeability to O.sub.2 and N.sub.2
(incondensable gases).
[0060] Tubing 9 is at least partly, preferably entirely or at least
at the curves, defined by a corrugated tube, exhibiting a profile
of the type illustrated in FIG. 3. In detail externally, preferably
also internally, tubing 9 exhibits an alternation of protrusions 12
and recesses 13, alternating with one another for defining a
substantially undulated outer profile, according to what
illustrated in FIGS. 3 and 4.
[0061] This advantageously achieves an increase of the turbulence
in the passage of the cooling fluid that allows making the heat
exchange more efficient.
[0062] Preferably, tubing 9 used for evaporator 7 has a maximum
outer diameter "De-max" comprised between 6 mm and 14 mm and
preferably within the optimum range 8-11 mm whereas the length of
tube 9 for the evaporator will be comprised between 8 and 26 m
based on the thermal exchange required and on load losses. On the
contrary, the optimum dimensions of the refrigeration circuit, in
the condenser section (first heat exchanger 5), are as follows:
maximum outer diameter De-max of the tube comprised within the
range 5-10 mm and, preferably within the range 6-8 mm.
[0063] The above results from the fact that the cooling fluid going
through the condenser is subject to higher pressures (condensing
vapour) and thus this requires smaller cross dimensions of the
tubing.
[0064] The tube length will be comprised within a range between
4-15 m based on the thermal exchange required and on load
losses.
[0065] A fundamental feature of refrigeration circuits, besides
ensuring the desired thermal exchange, is to constitute a barrier
as much as possible impermeable to different agents.
[0066] Below are the agents and the typical limits application in
question:
TABLE-US-00001 Maximum admissible Agent permeation Unit of
measurement Isobutane 0.5 g/year Oxygen + 1% Molar fraction,
relative to the Nitrogen coolant, admitted for the entire life of
the refrigerator (10 years) Water 100 p.p.m Fraction by weight,
relative to the coolant, admitted for the entire life of the
refrigerator (10 years)
[0067] It is known that the refrigeration circuits work in a range
of temperatures from -30.degree. to +70.degree. C. and in a range
of pressure varying from 0.3 to 12 bar; of course, the
impermeability specifications of the above table must be kept
within all of these ranges. Moreover, in the standard operation of
a refrigeration circuit, the lubricating oil of the compressor is
partly and uninterruptedly carried along with the coolant it is
perfectly soluble with. The oil does not exhibit the features of
the coolant, that is, those of evaporating at low temperature, and
it is therefore carried by the suction current generated by the
compressor along all the refrigeration circuit, or in solution with
the coolant or in the form of droplets if (evaporator) the coolant
has already evaporated.
[0068] To allow this transport of the coolant, the velocity of the
cooling fluid should in general preferably be higher than 4 m/sec.
If not, there is the risk that the compressor may be deprived of
the oil that gets trapped in the corrugations of the tube and may
burn out.
[0069] Of course this phenomenon poses limitations to the maximum
sections of the circuit itself which will also depend on the type
of corrugation. Cost issues also pose limitations to the maximum
usable sections. On the contrary, for reasons related to the
thermal exchange and to load losses, it is important to have the
higher sections of the refrigeration circuit within their maximum
diameters, to the minimum values mentioned above.
[0070] It is therefore clear that the dimensional and geometrical
ranges shown above are not simple design choices but they are the
result of a compromise that allows ensuring and maintaining all the
requirements of the refrigeration circuit.
[0071] Any variations outside the ranges mentioned above imply the
non observance of one or more operating requirements and the
impossibility of the refrigeration circuit to be used in the
commercial practice.
[0072] The tube diameter, its length and the shape of the profile
corrugation are also involved in the generation of noise inside the
tube by the effect of turbulence and of the frequencies of the
vortices generated inside the tube itself.
[0073] The corrugation and the selection of the diameter must
therefore take into account also this aspect and all the aspects
related to the tubing shape.
[0074] Tubing 9, in a possible embodiment, has a step "p", that is,
the distance between two consecutive protrusions 12, preferably
equal to 2 mm. Moreover, the tubing may have a shape ratio, that
is, the ratio between the outer side surface of a portion of tubing
and a corresponding longitudinal length of the portion itself,
comprised between 20 mm.sup.2/mm and 60 mm.sup.2/mm.
[0075] Advantageously, the corrugated shape of tubing 9 causes an
increase in the outer surface of tubing 9 itself relative to a
cylindrical tubing having a same length, and in this way the
thermal exchange between the cooling fluid circulating inside
tubing 9 and the air outside the same is facilitated.
[0076] Advantageously, moreover, the corrugated profile of tubing 9
of plastic material makes the same more flexible compared to a
similar cylindrical tubing, allowing bending radiuses and angles
that otherwise would cause the squeezing thereof (with reduction of
a passage section of the cooling fluid) and thus, adaptable to be
arranged according to a plurality of different configurations by
simply bending tubing 9 without intervening plastically and
irreversibly deforming tubing 9 itself. According to an embodiment
not shown, tubing 9 may exhibit only some corrugated portions, in
particular only the portions intended for defining curved portions
in the path of tubing 9 itself or those where thermal exchange is
to be maximised. The remaining portions of tubing 9, in that case
intended for defining rectilinear portions, may be smooth or in any
case free from surface shaping. In the case of smooth portions, the
inside diameter of the tubing will be comprised between 4 and 11 mm
and preferably between 6-8 mm.
[0077] Tubing 9 may advantageously be produced by an extrusion
process, wherewith a hollow cylindrical extrusion is obtained which
may be further modified by in line finishing processes, for
obtaining a desired profile of tubing 9. In particular, the
extrusion process may be followed by a shaping step that imparts
the corrugated shape illustrated in FIG. 3 to the entire hollow
cylindrical body or only to a portion thereof. This may be obtained
by coupling a counter-shaped matrix to the corrugated profile to be
obtained externally to the hollow cylinder body, and generating
such pressure inside the body itself as to plastically deform it
forcing it to take a shape counter-shaped to the matrix.
Preferably, this step is carried out when the hollow cylindrical
body is still at a high temperature, corresponding to a state
suitable for a plastic deformation process. As an alternative,
instead of an internal pressure it is possible to generate a
depression between the hollow cylindrical body and the matrix, so
as to force a reciprocal approach of the same and a deformation of
the hollow body that takes the matrix shape. The shaping operation
described above leads tubing 9 to take a corrugated profile both
internally and externally, according to the view of FIG. 3, and
this imparts the flexibility properties mentioned above and of
turbulence of the cooling fluid circulating therein. Besides having
circular shape as in FIG. 3, the geometry of the section of the
corrugated tube can have also other shapes that aid the improvement
of the thermal exchange. For example, on chest freezer, evaporator
7 is wound about a metal rack. The tube presently used, metal as
well (mainly aluminium) generally has a circular shape and
therefore it has a very small contact surface with the metal rack
that may be indicated in a single line on all the tube length.
[0078] Using a corrugated tube, suitably acting on the extrusion
section and on the corrugator shape, it is possible to obtain the D
section of FIG. 3a which, while maintaining its flexibility
required for winding the tube about the rack, allows increasing the
exchange surface as well as considerably improving the performance
of the freezer and decreases the cost.
[0079] According to the embodiment illustrated in FIG. 4, tubing 9
is obtained by a multilayer extrusion process (co-extrusion)
suitable for improving the mechanical and impermeability properties
of tubing 9. In fact, with a multilayer extrusion process it is
possible to obtain a tubing 9 having two or more layers, each
suitably selected based on specific functions to be carried out
such as, referring to what already said before, impermeability to
the cooling fluid, impermeability to humidity and to incondensable
gases, flexibility, thermal conductivity, as well as resistance to
the pressure exerted by the cooling fluid.
[0080] According to a first requirement thereof, tubing 9 comprises
a first layer "S1", typically outermost, made of a material
provided with features adapted for imparting to tubing 9 the
necessary resistance to mechanical and thermal strains and
impermeable to the is cooling fluids commonly used in cooling
apparatus for household purpose (hydrocarbons), and in particular
R600a. Preferably, such material is a polyamide 6; 6-6; 6-12; 11;
12 or one of the respective copolymers, preferably polyamide
6-6
[0081] According to a second requirements, tubing 9 comprises a
second layer "S2", usually innermost, made of a material
impermeable to water and resistant to hydrolysis (or also N.sub.2
and O.sub.2) and characterised by good compatibility with the
material of layer S1.
[0082] Preferably, such material is a copolymer, for example of the
type Bynel.RTM. by the company DuPont like Bynel.RTM. 4206, low
density polyethylene modified maleic anhydride or Bynel.RTM.
50E662, polypropylene modified maleic anhydride. The second layer
"S2" is combined, that is, overlapped, to the first layer "S1" for
making a protection of the cooling fluid to any introduction of
humidity or water coming from the exterior, improving at the same
time the chemical inertia of the tube against the above cooling
fluids. In general, the overall thickness S of the tube will be
comprised between a minimum and maximum value of 0.4-1.5 mm and of
a preferred range between 0.6 and 1.2 mm.
[0083] Thickness S1 of the material barrier to humidity and water
is comprised between 20% and 40% of the total thickness and is
about 30%.
[0084] On the contrary, thickness S2 of the material barrier to the
cooling fluid and air is about 70% of the total thickness (in
general comprised between 60% and 80%).
[0085] The thickness of the first layer S1 is comprised between 0.2
mm and 0.4 mm whereas the thickness of the second layer S2 is
preferably comprised between 0.4 mm and 1 mm.
[0086] To alternatively reduce the molar fraction of water in the
circuit, it may be necessary to search for balance conditions of
the refrigeration circuit that provide for the use of different
materials for balancing the permeability of water between condenser
10 and evaporator 7.
[0087] Since condenser 10 operates at a higher pressure (2.5-7 bar)
than the evaporator (normally 0.5-2.5 bar--the pressure of 2.5 bar
common to evaporator and condenser takes place at stationary
circuit), it may be useful for the latter to consist of only the
material PA6-6 or PA12 without the waterproof layer. During the
operation of the compressor, the condenser allows the water entered
through the evaporator to go out again thus maintaining a balanced
situation. This allows maintaining the water molar fraction inside
the circuit below certain critical values that the current
regulations set to 100 ppm.
[0088] Going back now to the exemplifying diagram of FIG. 1, the
above filter 18 is noted, which is arranged between the first
exchanger 5 and the lamination device 6 and is suitable for
removing any humidity present in the circuit, for example by the
use of a gel capable of absorbing it.
[0089] The lamination unit 6, on the contrary, comprises a
capillary tube 19 for reducing the pressure in the passage of the
cooling fluid between the first exchanger 5 and the second
exchanger 7. Moreover, in its path it also performs a function of
energy recovery exchanging heat between the hot coolant at the
liquid state that flows therein and the cold vapour present in the
tube at the outlet of evaporator 7.
[0090] This thermal exchange operation is carried out in the
so-called "exchanger tube" shown enlarged in FIG. 1.
[0091] In order to make the thermal exchange more efficient, with
the same length of the tube and thus same load losses desired in
the capillary, it is possible to make the capillary tube with a
section different from the standard one illustrated in FIG. 5.
[0092] For example it will be possible for at least the portion of
capillary tube 19 that performs the heat exchange exhibits an outer
surface of larger area than that of the tube with circular section;
in that case, the section of the capillary tube 19 may exhibit one
or more lobes 22 for increasing the thermal exchange.
[0093] The "lobed" section is illustrated in FIG. 6 and its primary
purpose is to increase the outer surface of the tube that exchanges
heat with the cooling gas outside.
[0094] In fact, always as visible in FIG. 1, at least a portion of
the capillary tube 19 is placed inside a portion of tube 21 in
output from evaporator 7 for allowing energy recovery.
[0095] Tubing 9 (FIGS. 7, 8, 9, 10) then comprises heating means 23
steadily coupled for allowing a selective defrosting of evaporator
7 when required.
[0096] In dynamic or No Frost evaporators, the defrosting function
of the evaporator circuit is carried out automatically by the
intervention of electrical resistances external to the circuit.
[0097] This method of defrosting is not very efficient as it is
based on the heat transmission from the electrical resistance of
the ice formed on the tubes by radiation.
[0098] In the present finding the aim is to obtain the defrosting
of the ice by the heating means 23 that are differently coupled in
a steady manner to tubing 9.
[0099] The heating means 23 comprise, in a first embodiment, at
least one metal conductor 24, preferably thread-like constrained to
a layer S of tubing 9 (see FIGS. 7, 8, 9, and 10).
[0100] In general, the metal conductor 24 is constrained to the
second layer S2 inside tubing 9 as in particular it is coextruded
with the same and is therefore at least partly buried.
[0101] FIGS. 7 and 8 show the presence of two electro-conductive
wires arranged with prevailing pattern substantially parallel to
the development direction of tubing 9.
[0102] On the contrary, FIGS. 9 and 10 show the adoption of a
thread-like metal conductor 24 wound spiral-wise around the axis of
development of tubing 9.
[0103] In an alternative embodiment (or optionally in combination
with the previous one), the heating means comprise a layer of
conductive material 25 obtained on a surface, preferably external,
of tubing 9 (see FIG. 10a).
[0104] The embodiment of such conductive layer 25 may be obtained
according to different technologies, such as metallization of the
tube surface to be made by metallization in high vacuum, by
deposition of conductive nanoelements on the tube surface, etc.
[0105] As an alternative it will be possible to coextrude a thin
layer of conductive thermoplastic material that has the same
function.
[0106] The coating of the tube with nanoelements may both
constitute a further barrier to the inlet of water into the
refrigeration circuit, and for the peculiarity of the surface
thereof, a factor of increase of the thermal exchange with the
air.
[0107] In general, at least one insulating surface coating 26 will
be provided for protecting the heating means 23 from the ambient
outside tubing 9 (FIG. 10a).
[0108] In particular, such surface coating 26 may be obtained by
deposition of an insulating polymeric film or by other surface
coating treatments.
[0109] The heat required for defrosting the ice is thus transferred
by the heating means 23 by direct conduction from the resistance
buried in the tube to the ice, thus considerably increasing the
efficiency of the defrosting system and reducing energy
consumption.
[0110] It should be noted that the types of resistances mentioned
above are flexible and thus they do not impair the typical
possibility of bending of corrugated tubes.
[0111] Advantageously, according to an embodiment illustrated in
FIGS. 17, 18 and 19, tubing 9 may be obtained both by direct
extrusion and corrugation with elements of different sizes, and by
the assembly of two or more tube portions, preferably corrugated
(FIG. 18) but not necessarily so (FIG. 19), having dimensional
modularity features. In other words, tubing 9 may be obtained from
the reciprocal coupling of two, and preferably a plurality of,
portions of corrugated tube preferably having same dimensions both
in section and in length. This allows obtaining tubing 9 having
different lengths starting in any case from portions having a same
standard length, and thus suitable for facilitating respective
storage processes. In this case in fact it is necessary to have
stored only a reduced range of portions, or optionally only one
type of tubes, which are then assembled in a sufficient number to
make a tubing 9 having a desired length.
[0112] As mentioned before, a less expensive system that prevents
junctions may be obtained by extrusion and continuous corrugation
of the different parts of the refrigeration circuit using elements
of the corrugator made according to different geometries. Some
possible assembly solutions shall now be illustrated hereinafter
with reference to the refrigeration circuit, of the various
components thereof.
[0113] The details of the junctions illustrated may be made with
alternative methods, such as vibration welding, laser etc; the
purpose of the junctions is to provide a connection of mechanical
and/or physical and/or chemical type, which should be impermeable
to the cooling gas and to the other gases and humidity mentioned
above.
[0114] In general, the circuit will exhibit a plurality of coupling
terminals or connectors 15 for connecting to is each other multiple
portions of tube belonging to the refrigeration circuit or
connecting the tube itself to the various components.
[0115] FIG. 11 shows a possible embodiment of the connection
between the capillary tube 19 and the corrugated tube 9 belonging
to the evaporator.
[0116] In particular, connector 15 comprises a seat 27 suitable for
receiving an end 28 of tubing 9; the seal between connector 15 and
tubing 9 is ensured by a suitable welding.
[0117] Connector 15 further comprises a through cavity 29 for
allowing the passage of the cooling fluid between the connected
tubes and the connector itself. In particular, the capillary tube
19 entirely crosses the above through cavity bringing directly the
cooling fluid at the inlet section of the corrugated tube 9.
[0118] In order to ensure the seal between the capillary tube 19
and connector 15, the latter comprises a shaped seating portion 31
suitable for being crossed by the end of the capillary tube 19 for
defining in cooperation with the latter an irremovable constraint
area 30. The constraint is preferably obtained using suitable
glue.
[0119] Going to look at FIG. 12, it should be noted that the same
shows a detail of the exchanger tube, that is, of the portion of
tube wherein the capillary is within tubing 9 for making the above
thermal exchange.
[0120] As it may be noted, the coupling in the left portion between
the connector and the tubing portion 21 that contains the capillary
may be obtained by welding, using the above seat 27 that receives
end 28 of tubing 9 and the welding technology.
[0121] Connector 15 then comprises an inlet/outlet hole 37 for
allowing the passage of the capillary tube 19 from inside tubing 9
to the outer ambient and vice versa (to this end it should be noted
that the inlet zone of the capillary tube will be mirror or with
different configurations compared to that shown in FIG. 12 where
the outlet takes place).
[0122] It should then be noted that the connection between the
exchanger tube with the return tube from the evaporator exhibits
both a glued junction zone (exchanger tube+capillary tube with
return tube), and a junction welded by rotation (exchanger tube to
the connector).
[0123] FIG. 13 shows an embodiment version of connection between
the exchanger tube with the return tube to the evaporator: in fact,
such junction is entirely made by gluing.
[0124] In particular, the shaped seating portion 31 and the tube
end define means for first coupling 32 for allowing a first holding
into position to the purpose of a subsequent irremovable
constraint.
[0125] In particular, the first coupling means 32 of FIG. 19
comprise respective expansions 33 and recesses 34 respectively
defined in one or in the other of the shaped seating portions 31
and of the ends of the tube to ensure a first engagement by
interference that maintains the reciprocal position during the
subsequent permanent junction steps.
[0126] During assembly, such expansions 33 and recesses 34 are
placed relative to each other so as to ensure the keeping of the
position during the irremovable constraint steps (by glue, welding
or the like).
[0127] The same type of first coupling means 32 may be used for
connecting subsequent tubing portions directly to one another, as
clearly shown in FIG. 19.
[0128] Finally, it should be noted that to avoid the use of
connectors at the exchanger tube, it is possible to adopt the
solutions shown in FIG. 14 and in FIG. 15, that is, make in said
tubing 9 an inlet/outlet hole 37 for allowing the passage of the
capillary tube from the exterior inside tubing 9 and vice versa.
The fluid seal may be ensured by glue or welding.
[0129] FIG. 15 shown an embodiment version wherein the inlet/outlet
hole 37, instead of being at the normal corrugations of the tubing,
is defined in a pre-shaped zone 38 suitable for defining a flat
inlet/outlet area of the capillary tube that is substantially
parallel to the axis of the tube itself.
[0130] In this way it is possible to define a reference surface and
ensure better gluing and seal between the tubing.
[0131] In this way, only the seal of the capillary in input and
output from the tube is required without further necessary
processes.
[0132] Finally, FIG. 16 shows how to connect metal tubes belonging
to the circuit (for example the inlets and the outlets from the
compressor identified with reference 35) to tube 9 according to the
invention. In particular, an end of tubing 9 is overlapped to a
corresponding end of a metal tube 35 and there is an over-pressing
element 36 for irremovably constraining said ends.
[0133] In the preferred and illustrated embodiment, only evaporator
7 comprises a flexible tubing 9 made of plastic material, whereas
condenser 5 comprises a conventional metal coil 10 which is welded
to the remaining part of the refrigeration circuit 3. However, it
is possible to make an apparatus 1 exhibiting both coil 10 of
condenser 5 and tubing 9 of evaporator 10 of synthetic material,
preferably one or more plastic materials of the type described
above.
[0134] The present invention attains the proposed objects,
overcoming the disadvantages mentioned in the prior art.
[0135] The use of connectors that in any case are elements of
discontinuity in the circuit and that have a certain cost, may be
avoided using corrugators of higher length and provided with
shaping elements shaped to obtain different sections in the same
continuously extruded corrugated tube; the above sections with
special shape, for example required for coupling to the copper tube
(35), may be obtained by continuous extrusion and corrugation with
shaped elements. In the same way, the exchanger tube 17 may be
extruded continuously with tube 9 of evaporator 7, inserting in the
corrugator, if required, shaped elements that allow obtaining
section 38 for inserting capillary 19 and the final portion 36 for
over-pressing. In this way it is possible to prevent some coupling
joints, making the refrigeration circuit safer and less
expensive.
[0136] The presence of a flexible tubing allows a very simple and
elastic installation of the same on the household appliance, since
no advance definition of the tubing configuration is required but
on the contrary, the latter is bent in optimised and diversified
manner according to the requirements of space and shape of the
thermal exchange surface to be covered.
[0137] The corrugated shape, at least in portions, of the tubing
allows an increase of the thermal exchange surface since the
corrugated shape of the tubing exhibits a greater outer surface
than a corresponding smooth or in any case perfectly cylindrical
tubing. Moreover, the corrugated shape also inside the tubing
itself allows generating whirling motions in the cooling fluid that
positively affect the thermal exchange made by the fluid
itself.
[0138] The lamination device 6 and art of the exchanger tube
constitute a tubular exchanger having an inner tube a calibrated
polyamide tube, wherein the liquid to be cooled flows, and an outer
tube, optionally coextruded with the inner one (FIGS. 14a, 14b) or
rolled up or coextruded/rolled up (14c) externally or internally to
tube 17, wherein the vapour to be heated to be then compressed by
the compressor without droplets flows. The device described above
may be entirely made of plastic material and in the desired shapes,
unlike what occurs presently using metals which, for obvious
reasons, limit shapes and length thereof.
[0139] As said, tube 17 may also be obtained as simple extension of
tube 9 of evaporator 7 thus eliminating a junction.
[0140] Both such device and the various components of the
refrigeration circuit, are then suitable for being made by
coextrusion of plastic material with inserted one or more thin
metal wires, usable as resistances for the quick defrosting of the
evaporator or any other part of the circuit, or for overheating the
vapour to be sent to the compressor.
[0141] In other words, and if required it will thus be possible
(even independently of the corrugation of the tubing or portions
thereof) to bury such resistances (wires of metal or conductive
material) in predetermined portions of the tubing for defrosting or
heating one or more parts of the circuit.
[0142] As an alternative (or in combination) it will be possible to
provide for the tube or portions thereof to be made by coextrusion
of one or more layers of plastic material covered by a special lake
(further outer layer) containing conductive nanoelements; such lake
will be applicable by spray during the extrusion or afterwards on
the already assembled work or as an alternative even by immersion
in a special bath and will have the characteristic of generating
heat when crossed by an electrical current, so as to carry out the
function of defrosting or heating device of specific zones of the
refrigeration circuit.
[0143] Condensers 10 may be made similarly to what described for
evaporators 9, making the plastic material tube shapes and sizes in
the most suitable possible manner for the operating requirements of
the refrigerating appliances.
[0144] Condensers 10 operating upstream of the compressor must
higher pressures than those of evaporators 7. For this reason, they
should meet more restrictive rules, in particular they should
withstand a pressure of 36 bar.
[0145] For this reason, the thickness of corrugated tubes must be
increased to no less than 0.7 mm (preferably 0.8-1.4 mm) and it is
thus important to increase the thermal exchange surfaces making
suitable geometries. All these components of the circuit may be
coupled to each other by the above connectors, allowing assembly
saving (they are presently welded to one another) and assembly
safety.
[0146] The connections between the components of the refrigeration
circuit (evaporator, capillary, exchanger tube, compressor,
condenser and filter) may be obtained by rotation welding
operations or gluing by the use of quick connections with seals
(o-rings or alternative ones) as sealing element.
[0147] It is also possible to make such shapes on the corrugated
tube as to allow snap-wise coupling and creating the deposition
seat of a sealing adhesive or a special sealing element such as for
example an O ring of suitable material (FIG. 20) with the placement
of glue 40 for sealing the space between the two sealing elements
42 and 43. The glue may be inserted through hole 41 (two
symmetrical holes may be required for venting the air).
[0148] Moreover it should be noted that the particular shape of the
capillary appears advantageous in se, irrespective of the presence
of corrugated plastic tubes; also the connectors described above
are per se usable and independent of the presence of corrugated
plastic tubes.
[0149] The described invention thus eliminates the complex and
expensive processes for making the metal tube and bending the same
for obtaining the traditional metal coil of the evaporator, and the
range of products on stock is reduced since it is necessary to
store only the tubing that has not received the final winding and
bent configuration yet. Also the need of storing the tubing may be
easily eliminated having an extrusion and corrugation line for the
plastic tube the cost whereof is at least 20 times less than a
production line for metal tubes and for the operation whereof it is
necessary to have a covered surface much smaller than that required
for a production line of the metal tube.
[0150] The manufacture of the tubing of plastic material and in
particular by extrusion or coextrusion processes drastically
reduces the costs of the raw material required to make the various
components of the refrigeration circuit and greatly simplifies the
manufacturing processes of the tubing itself with consequent
drastic decrease of the manufacturing costs of the household
appliance. Moreover, this allows greatly reducing the mass of the
household appliance, replacing the conventional metal coil with a
coil of plastic material.
[0151] The possibility of obtaining a tubing starting from modular
portions of tube further facilitates storage as only few types of
tube portions may be provided, having predetermined lengths and
sections.
[0152] The coupling of the tubing to the remaining part of the
refrigeration circuit does not require anymore the making of the
traditional welding which besides requiring special apparatus and
being mainly made manually, is also irreversible and thus it would
not allow removing the tubing from the household appliance.
[0153] The availability of quick connectors, the possibility of
having coextruded tubes that perform the function of heat
exchangers and the possibility of alternating parts of straight and
rigid tube to corrugated parts bending as desired, allows creating
different shapes and sections in the refrigeration circuits such as
to open new perspectives to design, to the functionality and to the
performance of the circuits themselves.
[0154] Also in this case, having special corrugators it is possible
to make different sections without discontinuities requiring the
use of joints. For example, the condenser tube 5 may be coextruded
to tube 10b and having special elements in the corrugator, the seat
of filter 18 may be obtained in the same way without the use of
connectors with the economic and safety advantages described above
(FIGS. 21a and 21b).
[0155] There are further advantages, such as corrosion resistance,
less surface porosity that makes it more difficult for the ice to
stick to the surfaces, the recyclability of the materials used for
the refrigeration circuit without the need of expensive operations
for separating the components, which contribute to making the
proposed technology even more competitive and advantageous compared
to the current one.
* * * * *