U.S. patent application number 16/203843 was filed with the patent office on 2019-03-28 for tube pattern for a refrigerator evaporator.
The applicant listed for this patent is Brazeway, Inc.. Invention is credited to Matt BAKER, Brian John CHRISTEN, Scott C. PETERS, Scot REAGEN, William SPROW, Gary WOLFE.
Application Number | 20190093939 16/203843 |
Document ID | / |
Family ID | 65807255 |
Filed Date | 2019-03-28 |
View All Diagrams
United States Patent
Application |
20190093939 |
Kind Code |
A1 |
REAGEN; Scot ; et
al. |
March 28, 2019 |
Tube Pattern For A Refrigerator Evaporator
Abstract
A refrigeration system for a refrigerator or a freezer,
comprising a compressor; a condenser; and an evaporator, wherein
the evaporator includes a coil formed of a plurality of linear
sections connected by a plurality of curved sections, and the coil
is attached to a plurality of fins, each fin has a length and a
width, and the width defines an evaporator depth; and the plurality
of curved sections are arranged in a number of columns to define a
tube pattern formed along the evaporator depth.
Inventors: |
REAGEN; Scot; (Sylvania,
OH) ; CHRISTEN; Brian John; (Monroe, MI) ;
SPROW; William; (Adrian, MI) ; PETERS; Scott C.;
(Adrian, MI) ; WOLFE; Gary; (Blissfield, MI)
; BAKER; Matt; (Onsted, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Brazeway, Inc. |
ADRIAN |
MI |
US |
|
|
Family ID: |
65807255 |
Appl. No.: |
16/203843 |
Filed: |
November 29, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14643065 |
Mar 10, 2015 |
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16203843 |
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61950916 |
Mar 11, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28D 1/024 20130101;
F25B 39/02 20130101; F25B 2339/0242 20130101; F28D 1/0477 20130101;
F25D 17/067 20130101; F25B 2500/01 20130101; F28F 1/26 20130101;
F28F 1/32 20130101 |
International
Class: |
F25D 17/06 20060101
F25D017/06; F28D 1/02 20060101 F28D001/02; F28D 1/047 20060101
F28D001/047; F28F 1/26 20060101 F28F001/26 |
Claims
1. A refrigeration system for a refrigerator or a freezer,
comprising: a compressor; a condenser; and an evaporator, wherein
the evaporator includes a plurality of fins and a serpentine coil
attached to each of the plurality of fins, the serpentine coil
being formed from a tube having a plurality of linear sections
interconnected by a plurality of curved sections, each fin has a
length and a width, and the width defines an evaporator depth; and
the plurality of curved sections that interconnect the plurality of
linear sections are arranged in a number of columns to define a
tube pattern formed along the evaporator depth, the plurality of
linear sections in each column are staggered to provide for air
flow between the plurality of linear sections to increase heat
transfer between a refrigerant carried by the serpentine coil and
the air, the number of columns is selected based on the evaporator
depth such that when the plurality of fins have a first evaporator
depth the number of columns is at least one, when the plurality of
fins have a second evaporator depth greater than the first
evaporator depth the number of columns is at least two, when the
plurality of fins have a third evaporator depth greater than the
second evaporator depth the number of columns is at least three,
and when the plurality of fins have a fourth evaporator depth
greater than the third evaporator depth the number of columns is at
least four, an outer diameter of the tube is in the range of 6.5 mm
to 7.5 mm.
2. The refrigeration system according to 1, wherein a wall
thickness of the tube is in the range of 0.3 mm to 0.7 mm.
3. The refrigeration system of claim 1, wherein the fins have the
second evaporator depth, and the tube pattern includes two columns
of curved sections.
4. The refrigeration system of claim 3, wherein the second
evaporator depth is about 50 mm.
5. The refrigeration system of claim 1, wherein the fins have the
third evaporator depth, and the tube pattern includes three columns
of curved sections.
6. The refrigeration system of claim 5, wherein the third
evaporator depth is about 60 mm.
7. The refrigeration system according to claim 6, wherein the
columns are spaced apart in a width direction of the fin such that
the fin cannot be divided into three fins having an evaporator
depth of about 20 mm each having a single column of curved
sections.
8. The refrigeration system of claim 5, wherein the third
evaporator depth is about 75 mm.
9. The refrigeration system of claim 1, wherein the fins have the
fourth evaporator depth, and the tube pattern includes four columns
of curved sections.
10. The refrigeration system of claim 9, wherein the fourth
evaporator depth is about 100 mm.
11. The refrigeration system of claim 1, wherein the outer diameter
of the tube is about 7.0 mm.
12. The refrigeration system of claim 1, wherein a spacing between
the columns is smaller than a radius of curvature of the curved
sections.
13. The refrigeration system according to claim 12, wherein the
radius of curvature of the curved sections is in the range of 9 to
12 mm.
14. A refrigeration system for a refrigerator or a freezer,
comprising: a compressor; a condenser; and an evaporator, wherein
the evaporator includes a plurality of fins and a serpentine coil
attached to each of the plurality of fins, the serpentine coil
being formed from a tube having a plurality of linear sections
interconnected by a plurality of curved sections, each fin has a
length and a width, the width defines an evaporator depth, and the
width is about 60 mm; and the plurality of curved sections that
interconnect the plurality of linear sections are arranged in a
three columns to define a tube pattern formed along the evaporator
depth, the plurality of linear sections in each column are
staggered to provide for air flow between the plurality of linear
sections to increase heat transfer between a refrigerant carried by
the serpentine coil and the air, and an outer diameter of the tube
is in the range of 6.5 mm to 7.5 mm.
15. The refrigeration system according to claim 14, wherein the
three columns are spaced apart in a width direction of the fin such
that the fin cannot be divided into three fins having an evaporator
depth of about 20 mm each having a single column of curved
sections.
16. The refrigeration system of claim 15, wherein a spacing between
the three columns is smaller than a radius of curvature of the
curved sections.
17. The refrigeration system according to claim 16, wherein the
radius of curvature of the curved sections is in the range of 9 to
12 mm.
18. The refrigeration system of claim 14, wherein the outer
diameter of the tube is about 7.0 mm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 14/643,065 filed on Mar. 10, 2015, which
claims priority to U.S. Provisional Patent Application No.
61/950,916 filed Mar. 11, 2014. The entire disclosures of the above
applications are incorporated herein by reference.
FIELD
[0002] The present disclosure relates to a tube pattern for a
refrigerator evaporator, and also relates to a refrigerator
evaporator equipped with the tube pattern.
BACKGROUND
[0003] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0004] The cost pressure in household appliance market is extremely
intense, and the increasingly strict governmental regulations are
requiring the household appliance to possess even higher energy
efficiency, which drives demands for more cost-beneficial and more
efficient components.
[0005] In the 1990's, the tube used for a refrigerator evaporator
in most of the markets was modified in its outer diameter from 9.5
mm to 8.0 mm to improve the return flow of oil being utilized with
new refrigerants. Although some improvements in performance were
noticed, such change has not been well understood.
[0006] It is generally known that when the diameter of a tube is
decreased, the wall thickness thereof and the material consumption
are also reduced, with the burst pressure being maintained. A
variety of heat transfer models would suggest that it may or may
not improve the heat transfer by reducing the tube diameter within
the operation area of the refrigerator, but the previous change in
diameter has suggested that it may involve certain improvement.
[0007] One of the severe uncertainties in further decreasing the
diameter is its unknown influence to the compressor. The
refrigerator evaporator is working at a condition near atmosphere
pressure or of slight vacuum. When the pressure approaches absolute
zero, the influence to the compressor increases, so that any
increase in the pressure drop may heavily influence the
compressor.
[0008] In order to reduce global warming, flammable refrigerants
are becoming more prevalent in the market. It is desired to
minimize the amount of refrigerants used in these applications, and
in some cases government regulation limits the amount of
refrigerant that can be used.
SUMMARY
[0009] This section provides a general summary of the disclosure,
and is not a comprehensive disclosure of its full scope or all of
its features.
[0010] According to a first aspect, the present disclosure provides
a refrigeration system for a refrigerator or a freezer that
includes a compressor; a condenser; and an evaporator. The
evaporator includes a plurality of fins and a serpentine coil
attached to each of the plurality of fins. The serpentine coil is
formed from a tube having a plurality of linear sections
interconnected by a plurality of curved sections. Each fin has a
length and a width, and the width defines an evaporator depth. The
plurality of curved sections that interconnect the plurality of
linear sections are arranged in a number of columns to define a
tube pattern formed along the evaporator depth. The plurality of
linear sections in each column are staggered to provide for air
flow between the plurality of linear sections to increase heat
transfer between a refrigerant carried by the serpentine coil and
the air. The number of columns is selected based on the evaporator
depth such that when the plurality of fins have a first evaporator
depth the number of columns is at least one, when the plurality of
fins have a second evaporator depth greater than the first
evaporator depth the number of columns is at least two, when the
plurality of fins have a third evaporator depth greater than the
second evaporator depth the number of columns is at least three,
and when the plurality of fins have a fourth evaporator depth
greater than the third evaporator depth the number of columns is at
least four, and an outer diameter of the tube is in the range of
6.5 mm to 7.5 mm.
[0011] According to the first aspect of the present disclosure, a
wall thickness of the tube may be in the range of 0.3 mm to 0.7
mm.
[0012] According to the first aspect of the present disclosure, the
fins may have the second evaporator depth, and the tube pattern may
include two columns of curved sections.
[0013] According to the first aspect of the present disclosure, the
second evaporator depth may be about 50 mm.
[0014] According to the first aspect of the present disclosure, the
fins may have the third evaporator depth, and the tube pattern may
include three columns of curved sections.
[0015] According to the first aspect of the present disclosure, the
third evaporator depth may be about 60 mm.
[0016] According to the first aspect of the present disclosure, the
columns may be spaced apart in a width direction of the fin such
that the fin cannot be divided into three fins having an evaporator
depth of about 20 mm each having a single column of curved
sections.
[0017] According to the first aspect of the present disclosure, the
third evaporator depth may be about 75 mm.
[0018] According to the first aspect of the present disclosure, the
fins may have the fourth evaporator depth, and the tube pattern may
include four columns of curved sections.
[0019] According to the first aspect of the present disclosure, the
fourth evaporator depth may be about 100 mm.
[0020] According to the first aspect of the present disclosure, the
outer diameter of the tube may be about 7.0 mm.
[0021] According to the first aspect of the present disclosure, a
spacing between the columns may be smaller than a radius of
curvature of the curved sections.
[0022] According to the first aspect of the present disclosure, the
radius of curvature of the curved sections may be in the range of 9
to 12 mm.
[0023] According to a second aspect of the present disclosure,
there is provided a refrigeration system for a refrigerator or a
freezer that includes a compressor; a condenser; and an evaporator.
The evaporator includes a plurality of fins and a serpentine coil
attached to each of the plurality of fins, and the serpentine coil
may be formed from a tube having a plurality of linear sections
interconnected by a plurality of curved sections. Each fin has a
length and a width, the width defines an evaporator depth, and the
width may be about 60 mm. The plurality of curved sections that
interconnect the plurality of linear sections may be arranged in a
three columns to define a tube pattern formed along the evaporator
depth, the plurality of linear sections in each column are
staggered to provide for air flow between the plurality of linear
sections to increase heat transfer between a refrigerant carried by
the serpentine coil and the air, and an outer diameter of the tube
may be in the range of 6.5 mm to 7.5 mm.
[0024] According to the second aspect of the present disclosure,
the three columns may be spaced apart in a width direction of the
fin such that the fin cannot be divided into three fins having an
evaporator depth of about 20 mm each having a single column of
curved sections.
[0025] According to the second aspect of the present disclosure, a
spacing between the three columns may be smaller than a radius of
curvature of the curved sections.
[0026] According to the second aspect of the present disclosure,
the radius of curvature of the curved sections may be in the range
of 9 to 12 mm.
[0027] According to the second aspect of the present disclosure,
the outer diameter of the tube may be about 7.0 mm.
[0028] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
DRAWINGS
[0029] All the technical features of the present disclosure will
become more apparent from the accompanying drawings. The drawings
described herein are for illustrative purposes only of selected
embodiments and not all possible implementations, and are not
intended to limit the scope of the present disclosure.
[0030] FIG. 1 illustrates an example refrigerator/freezer including
a refrigeration system according to the present disclosure;
[0031] FIG. 2 is a schematic representation of a refrigeration
system according to the present disclosure;
[0032] FIG. 3 illustrates an evaporator of the refrigeration system
illustrated in FIG. 2;
[0033] FIG. 4 is a front perspective view of the evaporator
illustrated in FIG. 3;
[0034] FIG. 5 is a partial side-perspective view of the evaporator
illustrated in FIG. 3;
[0035] FIG. 6 illustrates another evaporator with a depth of about
75 mm and three columns of curved sections according to a principle
of the present disclosure;
[0036] FIG. 7 illustrates another evaporator with a depth of about
50 mm and two columns of curved sections according to a principle
of the present disclosure;
[0037] FIG. 8 illustrates another evaporator with a depth of about
60 mm and three columns of curved sections according to a principle
of the present disclosure;
[0038] FIG. 9 illustrates another evaporator with a depth of about
100 mm and four columns of curved sections according to a principle
of the present disclosure;
[0039] FIG. 10 is a graph illustrating the amount of heat transfer
that is achieved using evaporators having tube diameters of 1/4
inches (6.35 mm), 5/16 inches (8 mm), and 3/8 inches (9.5 mm),
respectively;
[0040] FIGS. 11-13 are graphs illustrating the evaluation of
influence to the heat transfer and pressure drop performance caused
by the tube outer diameter, representing three types of tubes with
different outer diameters which are 6.35 mm, 8.00 mm and 9.50 mm,
respectively;
[0041] FIGS. 14 and 15 graphically illustrate the comparison
between a 7.00 mm tube and a 8.00 mm tube arranged on an evaporator
with a depth of about 50 mm and 2 columns of tubes;
[0042] FIG. 16 and FIG. 17 graphically illustrate the comparison
between an evaporator with a depth of about 60 mm and 2 columns of
8 mm tubes and an evaporator with a depth of about 60 mm and 3
columns of 7 mm tubes;
[0043] and
[0044] FIG. 18 illustrates normalized energy results obtained by
testing three refrigerators using evaporators having tube diameters
of 5/16'', 7 mm, and 1/4''.
[0045] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0046] Example embodiments will now be described more fully with
reference to the accompanying drawings. For those skilled in the
art, all the features and advantage of the present utility model
will become more apparent from the accompanying drawings and
corresponding description.
[0047] Example embodiments are provided so that this disclosure
will be thorough, and will fully convey the scope to those who are
skilled in the art. Numerous specific details are set forth such as
examples of specific components, devices, and methods, to provide a
thorough understanding of embodiments of the present disclosure. It
will be apparent to those skilled in the art that specific details
need not be employed, that example embodiments may be embodied in
many different forms and that neither should be construed to limit
the scope of the disclosure. In some example embodiments,
well-known processes, well-known device structures, and well-known
technologies are not described in detail.
[0048] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a," "an," and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. The
method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the
particular order discussed or illustrated, unless specifically
identified as an order of performance. It is also to be understood
that additional or alternative steps may be employed.
[0049] When an element or layer is referred to as being "on,"
"engaged to," "connected to," or "coupled to" another element or
layer, it may be directly on, engaged, connected or coupled to the
other element or layer, or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly engaged to," "directly connected to," or
"directly coupled to" another element or layer, there may be no
intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0050] Although the terms first, second, third, etc. may be used
herein to describe various elements, components, regions, layers
and/or sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the example embodiments.
[0051] Spatially relative terms, such as "inner," "outer,"
"beneath," "below," "lower," "above," "upper," and the like, may be
used herein for ease of description to describe one element or
feature's relationship to another element(s) or feature(s) as
illustrated in the figures. Spatially relative terms may be
intended to encompass different orientations of the device in use
or operation in addition to the orientation depicted in the
figures. For example, if the device in the figures is turned over,
elements described as "below" or "beneath" other elements or
features would then be oriented "above" the other elements or
features. Thus, the example term "below" can encompass both an
orientation of above and below. The device may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
spatially relative descriptors used herein interpreted
accordingly.
[0052] FIG. 1 illustrates an example refrigerator/freezer 10
including an upper enclosure 12 and a lower enclosure 14 for
storing food or other articles to be cooled or frozen. Upper
enclosure 12 may be a freezer compartment, and lower enclosure 14
may be a refrigerating compartment. Refrigerator/freezer 10
includes a casing 16 that defines each of the upper enclosure 12
and lower enclosure 14, while also housing a refrigeration system
18 that is schematically illustrated in FIG. 2. Although
refrigerator/freezer 10 is described as including an upper
enclosure 12 and a lower enclosure 14, it should be understood that
the refrigerator/freezer 10 can include side-by-side enclosures,
only include a refrigerator compartment, only include a freezer
compartment, or be any other type of combination refrigeration and
freezer that is known to one skilled in the art.
[0053] Referring to FIG. 2, refrigeration system 18 may generally
include a compressor 20, a condenser 22, and an evaporator 24 that
are connected by connection lines 26. Disposed between condenser 22
and evaporator 24 may be an expansion device 27 such as a valve or
capillary tube. Compressor 20 receives low-pressure refrigerant
from evaporator 16 through one of the connection lines 26 at a
suction side and dispenses high-pressure refrigerant at a discharge
side through another of the connection lines 26 to condenser
14.
[0054] During refrigeration, refrigeration system 18 uses the
cooling effect of evaporation of the refrigerant to lower the
temperature of the surroundings near one heat exchanger (i.e.,
evaporator 24) and uses the heating effect of high pressure, high
temperature gas to raise the temperature of the surroundings near
another heat exchanger (i.e., condenser 22). This is usually
accomplished by releasing a refrigerant under pressure (usually in
a liquid phase) into a low pressure region to cause the refrigerant
to expand into a low temperature mixture of liquid and vapor.
Commonly, this low pressure region comprises a coil 28 that forms
part of evaporator 24. Once in the evaporator coil 28, the
refrigerant mixture may exchange heat with the tubing 30 of the
coil 28, which in turn exchanges heat with high temperature ambient
air of the region desired to be cooled. Evaporation of refrigerant
from liquid to gas absorbs heat from the ambient air and thereby
cools it.
[0055] Referring to FIG. 3, an evaporator 24 of refrigeration
system 18 is illustrated. Evaporator 24 includes coil 28 which
includes tubing 30 that meanders back and forth in a serpentine
pattern through a plurality of spaced apart fins 32. Fins 32 assist
tubing 30 with exchanging heat from the refrigerant mixture to the
ambient air, and are attached to tubing 30 either mechanically
(e.g., press-fit) or by brazing as is known in the art. Fins 32 are
spaced apart to allow for air to flow between fins 32 and around
tubing 30. Fins 32 and tubing 30 may be formed of aluminum, or any
other known heat exchange material. Fins 32 are generally
rectangular-shaped members having a length L, a width W, and a
thickness T, wherein the width W defines a depth of the evaporator
24.
[0056] FIG. 4 is a front perspective view of the evaporator 24
illustrated in FIG. 3. As shown in FIG. 4, fin 32 includes length
L, which in the illustrated embodiment is about 125 mm. It should
be understood, however, that length L of fin 32 is variable and can
be any length L desired. Fin 32 also includes a width W of about 25
mm. Fin 32, therefore, defines an evaporator depth of about 25
mm.
[0057] The tubing 30 of coil 28 may include a single tube that
includes a plurality of linear sections 34 that are interconnected
by curved sections 36. Alternatively, coil 28 may be formed of a
plurality of linear tubes (sections) 34 that are attached to
hairpin tubes (curved sections) 36 by brazing in substantially the
same manner as fins 32 are attached to tubing 30. As shown in FIG.
4, the evaporator 24 includes a single column 38 of curved sections
36. Moreover, curved sections 36 may be arranged at an inclined
orientation with respect to the evaporator depth (i.e., width W)
such that adjacent linear sections 34 are staggered, which improves
the flow of air between linear sections 34 and fins 32, thereby
providing optimal heat transfer. The angle of inclination theta
(.crclbar.) may range between twenty-five degrees and seventy-five
degrees relative an edge 40 of fin 32. Preferably, the angle of
inclination theta (.crclbar.) may range between 30 degrees and
seventy degrees relative an edge 40 of fin 32. In the illustrated
embodiments, the angle of inclination is about forty-five degrees.
Moreover, as best shown in FIG. 5, curved sections 36 are bent such
that a radius of curvature (R) of the curved sections 36 ranges
between 9.0 mm to 12.0 mm. In this manner, curved sections 36 are
bent as tightly as possible, with high bending quantity, to ensure
that the greatest number of linear sections 34 can be used to form
coil 28 of evaporator 24.
[0058] The present disclosure is also directed to evaporators 24
having multiple columns 38 of curved sections 36. As best shown in
FIGS. 6-9, evaporators 24 having two columns 38 of curved sections
36, three columns 38 of curved sections 36, and four columns 38 of
curved sections 36 are illustrated. It should be understood,
however, that the number of columns 38 can be greater than four,
without departing from the scope of the present disclosure.
[0059] In FIG. 6, which illustrates an evaporator 24 having three
columns 38 of curved sections 36, the fins 32 have a width W of
about 75 mm. FIG. 7 illustrates an evaporator 24 having two columns
38 of curved sections 36, where the fins 32 have a width W of about
50 mm. FIG. 8 illustrates an evaporator 24 having three columns 38
of curved sections 36, where the fins 32 have a width W of about 60
mm. Lastly, FIG. 9 illustrates an evaporator 24 having four columns
38 of curved sections 36, where the fins 32 have a width W of about
100 mm.
[0060] Regardless, it should be understood the refrigeration system
18 utilizes an evaporator 24 that includes either a single column
38 of curved sections 36 (FIG. 4), or multiple columns 38 of curved
sections 36. If multiple columns 38 of curved sections 36 are used,
it should be understood that a column 38 of curved sections 36 is
used for every 15 to 30 mm of fin 32 width W, preferably for every
18 to 27 mm of fin 32 width W, and most preferably for every 20 to
25 mm of fin 32 width W. Thus, an evaporator 24 having a depth (fin
width W) of about 50 mm may include two columns 38 of curved
sections 36; an evaporator 24 having a depth (fin width W) of about
60 mm may include three columns 38 of curved sections 36; an
evaporator 24 having a depth (fin width W) of about 75 mm may
include three columns 38 of curved sections 36; and an evaporator
24 having a depth (fin width W) of about 100 mm may include either
four or five columns 38 of curved sections 36.
[0061] The selection of the number of columns 38 of curved sections
36 is system dependent. In this regard, the size of the evaporator
24 is selected on the size of the refrigeration/freezer 10. For
example, a smaller refrigerator/freezer 10 may require a smaller
evaporator such as the evaporator 24 illustrated in FIG. 4 having
only a single column 38 of curved sections 36. In a larger
refrigerator/freezer 10, a larger evaporator 24 may be selected
such as the evaporators 24 illustrated in any of FIGS. 6-9 that
each have multiple columns 38 of curved sections 36. Regardless,
the appropriate evaporator 24 should be selected based on the
desired amount of maximum heat exchange capability in conjunction
with the effect on the compressor 20.
[0062] When evaporator 24 includes multiple columns 38 of curved
sections 36, it should be understood that the columns 38 of curved
sections 36 may be spaced apart in a width W direction of the fin
32 in a manner such that the fin 32 cannot be subsequently divided
into multiple fins 32 that each have a single column 38 of curved
sections 36. This is accomplished by having the columns 38 of
curved sections 36 be spaced apart at a distance that is less than
the radius of curvature R of the curved sections 36. For example,
FIG. 8 illustrates a 60 mm evaporator 24 having three columns 38 of
curved sections 36 that are spaced apart from each other such that
fin 32 cannot be divided into three fins 32 each having a width W
(i.e., evaporator depth) of about 20 mm and each having a single
column 38 of curved sections. By spacing the multiple columns 38 of
curved sections 36 apart in this manner, evaporator 24 will have a
compact design while still maintaining a maximum amount of heat
transfer capability. Alternatively, the columns 38 of curved
sections 36 may be spaced apart at a distance that is greater than
the radius of curvature R of the curved sections 36. Such a spacing
between columns 38 of curved sections 36 may be used with
evaporators 24 having a width W (evaporator depth) of about 50 mm,
about 75 mm, about 100 mm, and greater.
[0063] In addition to arranging curved sections 36 at an inclined
orientation with respect to the evaporator depth (i.e., width W)
such that adjacent linear sections 34 are staggered to improve the
flow of air between the linear sections 34 and the fins 32 to
provide maximum heat transfer, and in addition to spacing multiple
columns 38 of the curved sections 36 in a manner that achieves a
compact design while still maintaining a maximum amount of heat
transfer, the evaporator 24 used in the refrigeration system 18
according to the present disclosure also utilizes linear sections
34 and curved sections 36 that have an outer diameter that ranges
between 6.5 mm to 7.5 mm, inclusive. In addition, a wall thickness
of the linear and curved sections 34 and 36 ranges between 0.3 mm
to 0.7 mm as required by a burst pressure. Use of linear and curved
sections 34 and 36 having these dimensions reduces the material
manufacturing costs, and also further reduces internal volume
required refrigerant charge.
[0064] During development of refrigeration system 18 of the present
disclosure, two unexpected results were encountered during design
of evaporator 24. A first unexpected result was that the heat
transfer performance of evaporator 24 was much greater than
expected.
[0065] More particularly, one skilled in the art of evaporators for
heat transfer will readily acknowledge and appreciate that a widely
accepted correlation for heat transfer around a cylinder (i.e., a
tube) was developed by Hilpert and is commonly referenced in
textbooks and technical papers. The correlation for heat transfer
developed by Hilpert is as follows:
Nu=CRe.sup.mPr.sup.1/3 (1)
[0066] In equation (1), Nu=h D/k (Nusselt number), Re=.rho.VD/.mu.
(Reynolds number), and Pr=Cp .mu./k (Prandtl number). Further, h
represents a heat transfer coefficient, D represents a diameter of
a cylinder, K represents the air thermal conductivity, .rho.
represents the air density, V represents the air velocity, and .mu.
represents the air viscosity.
[0067] Moreover, the constants C and m are dependent upon Re as
shown in the below Table 1.
TABLE-US-00001 TABLE 1 Re C m 0.4-4 0.989 0.330 4-40 0.911 0.385
40-4000 0.683 0.466 4000-40,000 0.193 0.618 40,000-400,000 0.027
0.805
[0068] With the above in mind, FIG. 10 shows the measured amount of
heat transfer that can be achieved using an evaporator 24 having
linear and curved section tube diameters of 1/4 inches (6.35 mm),
5/16 inches (8 mm), and 3/8 inches (9.5 mm), and two columns 38 of
tubes. In FIG. 10, the term "UA" represents the overall heat
transfer coefficient and can be broken downs as it relates to the
tubes 34 and 36 and fin 32 of the evaporator 24 as follows:
UA=h.sub.TA.sub.T+h.sub.fA.sub.f (2)
[0069] In equation (2), the terms h.sub.T and A.sub.T represent the
heat transfer coefficient and surface area of the linear and curved
sections 34 and 36, respectively, and the terms h.sub.f and A.sub.f
represent the heat transfer coefficient (including fin efficiency
and fin-tube contact) and surface area of the fin 32,
respectively.
[0070] The heat transfer analysis was performed at 45 CFM (cubic
feet per minute), a common flow rate for a refrigerator or freezer
evaporator. The UA values from the data set above and the heat
transfer coefficient of the linear and curved sections 34 and 36
from Hilpert's correlation are utilized to calculate the heat
transfer coefficient across the fin 32.
TABLE-US-00002 TABLE 2 Tube OD Re Nu h.sub.T A.sub.T A.sub.f UA
h.sub.f 1/4'' 465.2 10.78 7.51 1.22 7.99 30.9 2.7 5/16'' 582.4
11.97 6.66 1.53 9.72 36.9 2.7 3/8'' 697.8 13.02 6.05 1.83 11.27
40.1 2.6
[0071] As can be seen from the above calculations, the heat
transfer coefficient (h.sub.f) of the fin 32 varies less than 4%,
and that any one data set can be used to accurately predict one of
the other data sets by simply adjusting the heat transfer
coefficient (h.sub.T) of the tubes 34 and 36 per Hilpert's
correlation. In fact, one skilled in the art will appreciate that
this is a common method of using data to empirically predict the
performance of a heat exchanger such as evaporator 24 in comparison
to another with only a minor difference, such as a difference in
tube diameter.
[0072] This methodology can now be applied to the design depicted
in, for example, FIG. 8 of the patent application where the fin has
an evaporator depth of about 60 mm, and there are three columns 38
of curved sections 36 (i.e., one column 38 of curved sections 36
for every 20 mm of evaporator depth). First, the fin heat transfer
coefficient (h.sub.f) was determined per the method above for a
typical 5/16'' tube design that includes a 60 mm evaporator depth
and two columns of curved sections, and a 7 mm design having the
column configuration illustrated in FIG. 8. Then, attempts were
made to predict the 7 mm performance utilizing the heat transfer
coefficient of the fin (h.sub.f) from the 5/16'' data and the heat
transfer coefficient of the tube (h.sub.T) per Hilpert's
correlation.
[0073] Based on the above and common practice it would be expected
that the heat transfer coefficient UA could be accurately predicted
for the 7 mm design utilizing the above methodology. Please note,
however, that the actual data obtained for a heat exchanger
manufactured with the design of FIG. 8 and a 7 mm tube yielded a
heat transfer coefficient that was different from what was
predicted using the above methodology. The results are shown below,
in Table 3.
TABLE-US-00003 TABLE 3 Tube OD UA source Re Nu h.sub.T A.sub.T
A.sub.f UA h.sub.f Standard 5/16'' design Data 582.4 11.97 6.66
2.30 11.85 45.5 2.53 FIG. 8, 7 mm design Data 511.3 11.27 7.14 3.20
11.23 57.4 3.05 FIG. 8, 7 mm design Predicted 511.3 11.27 7.14 3.2
11.23 51.5 2.53
[0074] As can be seen from Table 3, the fin heat transfer
coefficients (h.sub.f) calculated from the experimental data
utilizing the above methodology varied widely. Moreover, Table 3
indicates that if the data from the standard 5/16'' design were
used to predict the performance of the evaporator 24 illustrated in
FIG. 8, it would be largely inaccurate. Indeed, utilizing the
5/16'' data predicted a performance improvement of 14%
(UA.sub.predicted=51.5), while the actual design provided a 27%
improvement (UA.sub.actual=57.4). Thus, the evaporator 24 of FIG. 8
clearly and unexpectedly outperforms what would be predicted by one
skilled in the art.
[0075] A second unexpected result is the effect of the design of
the evaporator 24 on overall performance of refrigeration system
18. In this regard, it is well accepted in the industry that for
every 10% change in heat transfer coefficient UA, the energy
performance of a refrigerator or freezer (i.e., refrigeration
system 18) will change 1%. While one skilled in the art will
understand that there is some variation in this rule of thumb, this
effect on energy performance has generally held true for decades
across the industry.
[0076] As can be seen from the above analysis, smaller tube
diameters yield a higher heat transfer coefficient UA. Smaller tube
diameters also allow for tighter bend diameters and increases in
burst pressure so that thinner wall thicknesses can be utilized to
provide a more compact and material-efficient design. In addition,
smaller tube diameters have a much higher ratio of surface area to
internal volume. Hence, to provide the same heat transfer surface
area, much less internal volume is required, which results in a
reduced refrigerant charge. Reducing the refrigerant charge not
only saves cost on the refrigerant itself, but is also known to
improve energy performance due to reduced cyclic losses. It is
desirable, therefore, to reduce tube diameters to capture these
benefits.
[0077] Two evaporators each having three columns of curved sections
and an evaporator depth of about 75 mm were prepared that utilized
a 5/16'' tube and a 1/4'' tube, respectively, such that the heat
transfer coefficients UA of the designs were equivalent (i.e., no
impact on energy performance would be anticipated). The UA values
were confirmed by calorimeter (wind tunnel) testing.
[0078] Three refrigerators were utilized to test both designs.
Energy values after optimizing the refrigerant charge were:
TABLE-US-00004 TABLE 4 5/16'' 1/4'' % Difference Refrigerator #1
1.772 1.824 3.0% Refrigerator #2 1.680 1.755 4.5% Refrigerator #3
1.710 1.789 4.6%
[0079] It should be noted that the 1/4'' design reduced refrigerant
charge by 10% compared to the 5/16'' design.
[0080] The heat transfer performance would have predicted no change
in energy and the reduced refrigerant charge could improve energy,
so such a large degradation was highly unexpected.
[0081] The data was deeply analyzed and it was determined that the
1/4'' design placed too much restriction on the compressor of the
refrigerator, and that there was a "sweet spot" to take full
advantage of smaller tube diameters while not restricting the
compressor. The analysis showed that a diameter of 0.275'' was
optimal, which was later changed to a nominal 7 mm (0.276'').
[0082] An evaporator utilizing 7 mm tube was designed to have the
same UA value as the previous 5/16'' and 1/4'' designs (i.e., three
columns of curved sections and an evaporator depth of about 75 mm).
Again, the same UA values for these designs were confirmed by
calorimeter testing.
[0083] The three refrigerators were tested again with the following
energy results:
TABLE-US-00005 TABLE 5 5/16'' 7 mm % Difference Refrigerator #4
1.815 1.824 0.5% Refrigerator #5 1.729 1.754 1.4% Refrigerator #6
1.780 1.797 0.9%
[0084] The results for both tests are graphed (FIG. 18) with the
data being normalized such that the 5/16'' design has a UA value of
1.0. As shown in FIG. 18, the actual results vary from the
predicted results, and reducing the tube diameter below 7 mm has
detrimental effects, which is unexpected. Indeed, on average, the 7
mm performed within 1% of the 5/16'' design, with 1% considered the
accuracy of the test.
[0085] It should be noted that the 7 mm evaporator was
significantly smaller and lighter than the 5/16'' design, providing
both a 17% space savings and a 26% material savings.
[0086] The technology can also be utilized to improve energy
performance by matching the size of the 7 mm evaporator to that of
the existing 5/16'' evaporator. In fact, the design of FIG. 8
offers energy improvements of 2% to 4%. This follows the rule of
thumb noted above that for every 10% change in heat transfer
coefficient UA, the energy performance of a refrigerator (i.e.,
overall system) will change 1%. It is evaporators with diameters
below 7 mm that do not.
[0087] Two refrigerators were tested with evaporators having tubing
with 5/16'' diameter and 7 mm diameter, and the configuration
illustrated in FIG. 8. The results can be seen below in Table 6
where energy values after optimizing the refrigerant charge
were:
TABLE-US-00006 TABLE 6 5/16'' 7 mm % Difference Refrigerator #1
1.150 1.114 -2.1% Refrigerator #2 1.124 1.104 -1.8%
[0088] As can be seen in Table 6, the configuration of FIG. 8 when
used in combination with a tube having a diameter of 7 mm takes
full advantage of the heat transfer benefit of a smaller diameter
tube that does not adversely affect the compressor, and delivers a
reduction in energy usage.
[0089] Hereinafter the influence to heat transfer and pressure drop
performance caused by the outer diameter of the tubes is evaluated
by referring to FIG. 11 through FIG. 13. Two types of measurement
criteria are primarily used herein. A first criteria is UA per
pound (Ib) of aluminum, embodied in a heat transfer amount obtained
per material usage. A second criteria is UA per volume,
representing a heat transfer amount that can be obtained from a
given space.
[0090] FIG. 11 through FIG. 13 show three types of tubes with
different outer diameters which are 6.35 mm, 8.00 mm and 9.50 mm,
respectively; wherein the X-axis in FIG. 11 through FIG. 13
represents CFM (Cubic Feet per Minute); the Y-axis in FIG. 11
represents UA/lb; the Y-axis in FIG. 12 represents UA per volume;
and the Y-axis in FIG. 13 represents air side pressure drop.
[0091] As can be seen from FIG. 11 through FIG. 13, the smaller the
outer diameter of the tube 30 is, the higher the UA/lb of aluminum
and UA per volume are, with the decrease of the air side pressure
drop. These factors realize improvement in performance and/or
decrease in cost.
[0092] As also can be seen from FIG. 11 through FIG. 13, the
evaporator 24 arranged with a 6.35 mm tube is similar to the
evaporator arranged with 8.00 mm tube in the heat transfer
performance. In addition, in several tests of refrigerator
evaporators 24, evaporators provided with 6.35 mm tubes can
increase the energy consumption by 4%, on average.
[0093] The inventors, therefore, have found that a 7.00 mm tube can
provide beneficial advantages of a decreased tube diameter without
any negative influence to the performance of compressor 20, and can
maintain the energy efficiency and dramatically reduce the material
consumption.
[0094] Hereinafter the influences to performance of heat transfer
caused by using 7.00 mm tubes and 8.00 mm tubes are evaluated by
referring to FIG. 14 through FIG. 17.
[0095] FIG. 14 and FIG. 15 show a comparison between a 7.00 mm tube
and an 8.00 mm tube arranged on an evaporator with a depth of about
50 mm and two columns of tubes. It can be seen that, compared with
an 8.00 mm tube, the 7.00 mm tube improves the UA/lb by 14% and
improves the UA per volume by 12%.
[0096] FIG. 16 and FIG. 17 show a comparison between an evaporator
with a depth of about 60 mm and two columns of 8 mm tubes, and an
evaporator with a depth of about 60 mm and three columns of 7 mm
tubes.
[0097] As it can be seen from FIG. 16 and FIG. 17, the 7 mm tube is
designed to have a UA/lb (the heat transfer amount obtained per
material usage) higher than that of an 8 mm tube by 33%, and have a
UA per volume (the heat transfer amount that can be obtained from a
given space) higher than that of the 8 mm tube by 31%. Thus, the
overall performance of the system is unexpected.
[0098] While specific examples have been described in the
specification and illustrated in the drawings, it will be
understood by those of ordinary skill in the art that various
changes may be made and equivalents may be substituted for elements
thereof without departing from the scope of the present disclosure
as defined in the claims. Furthermore, the mixing and matching of
features, elements and/or functions between various examples is
expressly contemplated herein, even if not specifically shown or
described, so that one of ordinary skill in the art would
appreciate from this disclosure that features, elements and/or
functions of one example may be incorporated into another example
as appropriate, unless described otherwise, above. Moreover, many
modifications may be made to adapt a particular situation or
material to the teachings of the present disclosure without
departing from the essential scope thereof. Therefore, it is
intended that the present disclosure not be limited to the
particular examples illustrated by the drawings and described in
the specification as the best mode presently contemplated for
carrying out the teachings of the present disclosure, but that the
scope of the present disclosure will include any embodiments
falling within the foregoing description and the appended
claims.
[0099] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not
intended to be exhaustive or to limit the disclosure. Individual
elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the disclosure, and all such modifications are intended to be
included within the scope of the disclosure.
* * * * *