U.S. patent application number 13/839867 was filed with the patent office on 2013-12-05 for outdoor heat exchanger coil.
The applicant listed for this patent is AAF-McQuay Inc.. Invention is credited to John M. Bauer, Kazuo Fujisaki, David B. Gist, Kazushige Kasai.
Application Number | 20130319636 13/839867 |
Document ID | / |
Family ID | 49668823 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130319636 |
Kind Code |
A1 |
Gist; David B. ; et
al. |
December 5, 2013 |
OUTDOOR HEAT EXCHANGER COIL
Abstract
A coil system for an outdoor heat exchanger in a HVAC system.
The coil system comprises an integrated subcooler coil section
positioned between the primary coil section and the expansion
valve. A distributor combines the individual refrigerant streams
from the coils of the primary coil section into a single
refrigerant stream before separating the stream among the different
coils of the subcooler section. The subcooler coil section is
positioned such that the incoming air stream is directed directly
at the subcooler coil section to maximize the difference in
temperature between the air stream and the refrigerant within the
subcooler section.
Inventors: |
Gist; David B.; (Buffalo,
MN) ; Bauer; John M.; (Hanover, MN) ; Kasai;
Kazushige; (Minnetonka, MN) ; Fujisaki; Kazuo;
(St Louis Park, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AAF-McQuay Inc.; |
|
|
US |
|
|
Family ID: |
49668823 |
Appl. No.: |
13/839867 |
Filed: |
March 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61655317 |
Jun 4, 2012 |
|
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|
Current U.S.
Class: |
165/104.19 |
Current CPC
Class: |
F25B 39/04 20130101;
F28D 1/0477 20130101; F28F 1/00 20130101; F25B 40/02 20130101 |
Class at
Publication: |
165/104.19 |
International
Class: |
F28F 1/00 20060101
F28F001/00 |
Claims
1. A heat exchanger for transferring heat between a refrigerant
stream and an outdoor air stream in an HVAC system, comprising: a
plurality of primary coils defining a first primary coil section
and a second primary coil section, each primary coil receiving a
portion of a primary refrigerant stream, the primary coils arranged
in an outdoor airstream path such that the portions of the primary
refrigerant stream exchange a first quantity of heat with the
outdoor airstream path; a plurality of subcooler coils defining a
subcooler coil section having a front face mount orientation with
respect to the plurality of primary coils, each subcooler coil
receiving a portion of a subcooler refrigerant stream, the
subcooler coils arranged such that the portions of subcooler
refrigerant stream exchange a second quantity of heat with the
outdoor airstream path; and a subcooler distributor assembly
fluidly coupled between the primary coil section and the subcooler
coil section, wherein the subcooler distributor assembly receives
the portions of primary refrigerant stream from each of the
plurality of primary coils and combines the plurality of primary
refrigerant streams into a subcooler refrigerant stream, wherein
the subcooler refrigerant stream is separated into the portions of
subcooler refrigerant stream, each subcooler refrigerant stream
being directed into one of the subcooler coils.
2. The heat exchanger of claim 1, wherein the first primary coil
section defines a bottom primary coil section and the second
primary coil section defines a top primary coil section.
3. The heat exchanger of claim 1, wherein the front face mount
orientation of the subcooler coil section positions the subcooler
coil section in front of the bottom primary coil section, such that
an outdoor air stream passes over the subcooler coils before
contacting the primary coils of the bottom primary coil
section.
4. The heat exchanger of claim 1, wherein the subcooler distributor
assembly comprises at least one venturi distributor in a vertical
orientation, said vertical orientation promoting even distribution
of the portions of subcooler refrigerant steam into each subcooler
coil.
5. The heat exchanger of claim 1, wherein the first primary coil
section includes at least as many primary coils as the second
primary coil section, and wherein the subcooler coil section has a
front face mount orientation with respect to the first primary coil
section.
6. The heat exchanger of claim 1, wherein the second primary coil
section includes at least as many primary coils as the first
primary coil section, and wherein the subcooler coil section has a
front face mount orientation with respect to the first primary coil
section.
7. The heat exchanger of claim 1, further comprising a first
distributor assembly positioned between a refrigerant inlet and the
plurality of primary coils, the first distributor assembly
receiving a refrigerant inlet stream, the first distributor
separating the refrigerant stream into the portions of primary
refrigerant stream and directing each portion of primary
refrigerant stream into the corresponding primary coil.
8. The heat exchanger of claim 7, further comprising a second
distributor assembly positioned between the subcooler coil section
and a refrigerant outlet, the second distributor assembly receiving
the portions of subcooler refrigerant stream and combining the
portions of subcooler refrigerant stream into a refrigerant outlet
stream.
9. The heat exchanger of claim 8, wherein the first distributor
assembly, the second distributor assembly and the subcooler
distributor assembly each comprise at least one venturi distributor
in a vertical orientation.
10. A method for transferring heat between a refrigerant stream and
an outdoor air stream in an HVAC system, comprising: separating a
refrigerant stream into a plurality of primary coil streams, each
primary coil stream being directed through a corresponding one of a
plurality of primary coils positioned so as expose each primary
coil to an outdoor air stream, wherein a first quantity of heat is
transferred between each primary coil stream stream and the outdoor
air stream; collecting a portion of the plurality of primary coil
streams exiting from the primary coils; combining the portion of
the plurality of primary coils stream into a subcooler coil stream;
separating the subcooler coil stream into a plurality of portions
of subcooler coil stream; and feeding each portion of subcooler
coil stream through a corresponding one of a plurality of subcooler
coils, each subcooler coil positioned to expose each subcooler coil
to the outdoor air stream, wherein a second quantity of heat is
transferred between each portion of subcooler coil stream and the
outdoor air stream.
11. The method of claim 10, further comprising: arranging the
plurality of primary coils into a first primary coil section and a
second primary coil section, wherein the portion of the plurality
of primary coils streams is collected from the first primary coil
section.
12. The method of claim 11, further comprising: arranging the
plurality of subcooler coil sections into a subcooler coil section;
and mounting the subcooler coil section to the first primary coil
section such that the subcooler coil section has a front face mount
orientation with respect to the outdoor air stream.
13. The method of claim 12, wherein arranging the plurality of
primary coils into the first primary coil section and the second
primary coil section, further comprises: including at least as many
primary coils in the first primary coil section as are included in
the second primary coil section.
14. The method of claim 12, wherein arranging the plurality of
primary coils into the first primary coil section and the second
primary coil section, further comprises: including at least as many
primary coils in the second primary coil section as are included in
the first primary coil section.
15. The method of claim 10, wherein collecting a portion of the
plurality of primary coil streams exiting from the primary coils,
further comprises: collecting a condensed portion of the plurality
of primary coil streams exiting from the primary coils.
16. The method of claim 10, wherein combining the portion of the
plurality of primary coils stream into a subcooler coil stream,
further comprises: using a vertically oriented venturi distributor
to combine the portions of the plurality of primary coils stream
into the subcooler coil stream.
Description
RELATED APPLICATION
[0001] The present application claims priority to U.S. Provisional
Application No. 61/655,317, filed Jun. 4, 2012, and entitled,
"OUTDOOR HEAT EXCHANGER COIL", which is hereby incorporated herein
in its entirety by reference.
FIELD OF THE DISCLOSURE
[0002] The present invention is generally directed to a heat
exchanger coil system for a heat exchanger in a HVAC system.
Specifically, the present invention is directed to a heat exchanger
coil system for facilitating the exchange of heat between a
refrigerant stream and an outdoor air stream.
BACKGROUND OF THE DISCLOSURE
[0003] A conventional HVAC system generally comprises a compressor,
an expansion valve and at least two heat exchangers. A refrigerant
is sent from the compressor through the first heat exchanger to the
expansion valve and sent back to the compressor after passing
through the second heat exchanger. One of the heat exchangers is
typically positioned to exchange heat with an interior air stream,
while the other heat exchanger is positioned to exchange heat with
an outdoor air stream. Depending on whether the HVAC system is
functioning as a cooling system or a heating system, the exterior
heat exchanger can function as either a condenser or an evaporator
while the interior heat exchanger operates in the opposite
capacity.
[0004] The efficiency of the heat exchangers is typically gauged by
determining the "temperature approach" of the heat exchanger. The
temperature approach is the difference between the inlet
temperature of one stream and the outlet temperature of the second
stream and is commonly used as an efficiency measurement of the
heat exchanger. An efficient heat exchanger has a low temperature
approach while an inefficient heat exchanger has a high temperature
approach. In a HVAC system, a low temperature approach occurs when
the refrigerant output temperature from the heat exchanger is
nearly identical to the temperature of the air stream entering the
heat exchanger.
[0005] A typical heat exchanger configuration for HVAC systems is a
"fin and tube" configuration in which the refrigerant is fed
through an elongated tube and the air stream is passed across the
tube to cool or heat the refrigerant. The arrangement is effective
at providing maximum contact between the refrigerant and the air
stream. A challenge for exterior heat exchangers is that adverse
weather conditions, such as extremely low temperatures, can cause
frost to form on pipes, rob heat from the refrigerant instead of
supplying heat and otherwise reduce the efficiency of the heat
exchanger and HVAC system as a whole. As such, HVAC systems having
exterior fin and tube heat exchangers installed in less temperate
climates are often less efficient when the exterior weather
conditions as less than ideal.
[0006] A common feature of fin and tube heat exchangers used in
HVAC systems is having a plurality of individual tube coils instead
of a single elongated tube coil. The refrigerant input is typically
split evenly by a distributor into amongst the coils. The
refrigerant must be evenly distributed and constantly supplied to
each coil to maximize the heat transfer and efficiency of the heat
exchanger. However, in cooler temperatures, evenly distributing the
refrigerant between the different coils is often difficult as the
increased viscosity of the refrigerant and other factors cause the
refrigerant to be unevenly distributed through the heat
exchanger.
[0007] The reduced efficiency of exterior heat exchangers in less
temperate climates reduces the overall efficiency of HVAC systems
installed in those climates. As energy efficiency is a primary
concern with HVAC systems, the increased energy required by the
HVAC system to overcome the inefficiencies caused by poor
performance of the exterior heat exchanger is a significant
concern. As such a need exists to improve the efficiency of
exterior shell and tube heat exchangers in less temperate
climates.
SUMMARY OF THE DISCLOSURE
[0008] The present invention is directed to a coil system for an
outdoor heat exchanger in a HVAC system. The coil system comprises
an integrated subcooler coil section positioned between the primary
coil section and the expansion valve. A distributor can be
positioned between the primary coil section and the subcooler coil
section to combine the individual refrigerant streams from the
coils of the primary coil section into a single refrigerant stream
before separating the stream among the different coils of the
subcooler section. The subcooler coil section can be positioned
such that the incoming air stream is directed directly at the
subcooler coil section to maximize the difference in temperature
between the air stream and the refrigerant within the subcooler
section.
[0009] In a cooling mode where the coil system acts a condenser,
the condensed liquid refrigerant is drawn from the primary coil
section as the refrigerant condenses and is fed into the subcooler.
Continually removing the condensed liquid refrigerant improves the
efficiency of the heat exchanger and overall HVAC system by
dropping the condensing temperature in the primary section and
lowering the amount of energy required by the compressor supplying
the high pressure, gaseous refrigerant to the coil system.
Similarly, positioning the subcooler such that the incoming air
stream is directed at the subcooler maximizes the temperature
difference between the air stream and the refrigerant stream, which
facilitates further lowering of the refrigerant stream temperature
to nearly the temperature of the incoming air stream. The lower
refrigerant temperature leaving the coil system boosts the
evaporative capacity of the refrigerant stream thereby improving
the efficiency of the evaporator and the overall HVAC system.
[0010] In a heating mode where the coil system acts an evaporator,
the subcooler section is operated at an intermediate pressure and
an intermediate temperature between the evaporator temperature and
the condenser temperature. The operating conditions allow the
subcooler section to still draw heat from the air stream. The
smaller temperature difference between the subcooler and the air
stream can also prevent the subcooler coils from frosting too
quickly. This feature is particularly advantageous in wet and cold
weather conditions.
[0011] According to an embodiment of the present invention, the
coil system can further comprise at least one Venturi distributer
for distributing the fluid among coils of the primary section. Each
Venturi distributer is oriented in a vertical-up or vertical-down
orientation rather than at a non-vertical angle. Surprisingly,
orienting the Venturi distributer in a vertical orientation avoids
disruptions in the flow of refrigerant to and from the various
coils of the primary coil section that can occur when the Venturi
distributor is oriented in a non-vertical orientation. Similarly,
orienting the Venturi distributer in a vertical orientation
prevents uneven distribution of the refrigerant amongst the coils
that can occur when the Venturi distributer is oriented in a
non-vertical orientation.
[0012] A method for exchanging heat between a liquid refrigerant
and an outdoor air stream, according to the present invention, can
comprise supplying a refrigerant stream to an outdoor heat
exchanger having a primary coil section and subcooler coil section,
each having a plurality of coils. The method can further comprise
dividing the high temperature stream into a plurality of
sub-streams that are each fed into a primary coil of the primary
coil section. An outdoor air stream is passed across each of the
primary coil sections to exchange a first quantity of heat with the
subdivided refrigerant stream. The plurality of sub-streams can
then recombined into a single refrigerant before being
redistributed among the plurality of subcooler coils of the
subcooler coil section. The outdoor air stream is passed across
each of the subcooler coil sections to exchange a second quantity
of heat with the subdivided refrigerant stream. The subdivided
refrigerant stream is than recombined into a single refrigerant
stream.
[0013] The above summary of the various representative embodiments
of the invention are not intended to describe each illustrated
embodiment or every implementation of the invention. Rather, the
embodiments are chosen and described so that others skilled in the
art can appreciate and understand the principles and practices of
the invention. The figures in the detailed description that follow
more particularly exemplify these for embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a representative process flow diagram of a prior
art HVAC system.
[0015] FIG. 2 is a schematic side view of a heat exchanger coil
according to an embodiment of the present invention.
[0016] FIG. 3 is a partial schematic side view of a heat exchanger
coil of FIG. 1.
[0017] FIG. 4 is a perspective view of a heat exchanger coil
according to an embodiment of the present invention.
[0018] FIG. 5 is a side face view of a heat exchanger utilizing a
heat exchanger coil according to a representative embodiment of the
present invention.
[0019] FIG. 6 is a partially hidden side face view of the heat
exchanger of FIG. 5 having exterior fins removed.
[0020] FIG. 7 is a partial, perspective side view of the heat
exchanger of FIG. 5.
[0021] FIG. 8 is a partially hidden side view of the heat exchanger
of FIG. 5 having distributor assemblies and piping removed.
[0022] FIG. 9 is a side view of the heat exchanger of FIG. 5
[0023] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION
[0024] As shown in FIG. 1, a HVAC system 2 for use with the present
invention generally comprises a compressor 4, a first heat
exchanger 6, an expansion valve 8 and a second heat exchanger 10. A
refrigerant stream is fed through the compressor 4 to the first
heat exchanger 6, where a first air stream is passed across the
refrigerant stream to exchange a first quantity of heat with the
refrigerant stream. The refrigerant stream is then fed through the
expansion valve 8 and into the second heat exchanger 10 where a
second air stream is passed across the refrigerant stream to
exchange a second quantity of heat with the refrigerant stream. In
a cooling mode for cooling the interior of the building, the first
air stream is typically an outdoor air stream used to cool the
refrigerant stream, while the second air stream is an indoor air
stream cooled by the refrigerant stream. In a heating mode, the
outdoor air stream is effectively the second air stream that
supplies heat to refrigerant stream, while the indoor air stream is
effectively the first air stream drawing heat from the refrigerant
stream. For the purposes of this disclosure, an outdoor air stream
is an air stream originating from and supplied back to the exterior
of the building while an indoor air stream is an air stream from
and supplied back to the interior of the building.
[0025] As shown in FIG. 2-4, a heat exchanger 20 for exchanging a
quantity of heat with an outdoor air stream, according to an
embodiment of the present invention, "in cooling mode," comprises
an inlet 22, an outlet 25, a primary coil section 24 having a
plurality of primary coils 26 and a subcooler coil section 28
having a plurality of subcooler coils 30. The heat exchanger 20
further comprises a first header assembly 32 positioned between the
inlet 22 and the primary coil section 24, a second distributor
assembly 34 positioned between the primary coil section 24 and the
subcooler coil section 28; a third distributor assembly 36
positioned between the subcooler coil section 28 and the outlet
25.
[0026] As shown in FIGS. 2-3, according to an embodiment of the
present invention, the plurality of primary coils 26 can be
subdivided into a top section 38 and a bottom section 40. The
bottom section 40 can be positioned relative to the subcooler coil
section 28 such that an air stream fed through the heat exchanger
20 will pass across the subcooler coils 30 before intersecting the
primary coils 26 of the bottom section 40. In sizing the subcooler
coil section 28, the mode of operation of heat exchanger 20 will
determine the relative size of the subcooler coil section 28
relative to the primary coils section 24. For example, in a cooling
mode, subcooler coil section 28 is sized based upon pressure drop
and flow rate with the desired goal of having as close an approach
temperature as possible relative to the refrigerant stream and
outdoor air stream. Generally, an approach temperature of at least
5.degree. F. is desired, more preferably about 3-4.degree. F. and
even more preferably, about 2.5.degree. F. In a heating mode,
physical size of the subcooler coil section 28 can be a design
factor based upon potential condensation on the exterior of the
subcooler coils 30. According to one representative embodiment of
the present invention, the primary coil section 24 can comprise
twenty three parallel primary coils 26 with eleven primary coils 26
in the top section 38 and twelve primary coils 26 in the bottom
section 40. In this configuration, the primary coils 26 of the top
section 38 comprise 4-row coils while the primary coils 26 of the
bottom section 40 comprise 3-row coils. According to one
representative embodiment of the present invention, four subcooler
coils 30 can make up the subcooler section 28.
[0027] In cooling operation, a refrigerant stream is fed into the
inlet 22 and divided into a plurality of sub-streams by the first
header assembly 32. Each refrigerant sub-stream is fed into one of
the primary coils 26 and an outdoor air stream is passed across the
primary coils 26. In a cooling configuration, the refrigerant
stream is supplied from the compressor 4 as a high pressure, high
temperature gaseous stream that is cooled by the outdoor air
stream. As the outdoor air stream intersects the primary coils 26 a
portion of each refrigerant sub-stream condenses and exits the
primary coils 26 into the second distributor assembly 34 where the
sub-streams are recombined into a single refrigerant stream. In a
heating configuration, the refrigerant stream is supplied from the
expansion valve 8 as a cooled refrigerant stream that is heated by
the outdoor air stream. The heated refrigerant sub-streams are
similarly recovered in the second distributor assembly 34. In
either operating mode, the recombined refrigerant stream is then
separated again amongst the subcooler coils 30 for additional heat
transfer. The outdoor air stream is passed across the subcooler
coils 30 to either further cool the condensed refrigerant or supply
additional heat in a heating configuration. In cooling, the
subdivided refrigerant stream exiting the subcooler 28 is
recombined into a single refrigerant stream in the third
distributor assembly 36 before exiting the heat exchanger 20
through the outlet 25.
[0028] According to an embodiment of the present invention, at
least one of the distributor assemblies 32, 34, 36 can comprise at
least one Venturi distributer 42. In this configuration, the
Venturi distributer 42 is oriented in a vertical orientation to
avoid uneven distribution of the refrigerant stream that occurs
when the Venturi distributer 42 is oriented in a non-vertical
orientation.
[0029] Referring specifically to FIGS. 5-9, a heat exchanger 50
according to the present invention can comprise a frame 52 to which
individual fins 53 and heat exchanger coil 54 is mounted. As seen
in FIG. 5, fins 52 can be so closely spaced so as to provide a face
side 56 with a substantially solid looking appearance. With fins 52
removed, heat exchanger coil 54 is readily visible including
subcooler coil section 28 and top section 38.
[0030] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and described in detail. It is understood,
however, that the intention is not to limit the invention to the
particular embodiments described. On the contrary, the intention is
to cover all modifications, equivalents, and alternatives falling
within the spirit and scope of the invention as defined by the
appended claims.
* * * * *