BACKGROUND OF THE INVENTION
[0001] This application relates to microchannels heat exchangers of refrigerant systems
that utilize a distributor insert mounted within a manifold, and more particularly
to heat exchangers incorporating dividing elements separating the manifold into a
plurality of chambers, each associated with at least one heat exchange tube.
JP-6-159983 discloses a heat exchanger as defined in the preamble of claim 1.
[0002] In recent years, much interest and design effort has been focuse on the efficient
operation of heat exchangers (and condensers and evaporators in particular) of refrigerant
systems. One relatively recent advancement in the heat exchanger technology is the
development and application of parallel flow, or so-called microchannel or minichannel,
heat exchangers (these two terms will be used interchangeably throughout the text),
as the condensers and evaporators. Also, throughout the text, the reference will be
made to a heat rejection heat exchanger as a condenser, with the understanding that
the heat rejection heat exchanger may operate as a gas cooler, at least for a portion
of the time.
[0003] Such microchannel heat exchangers are provided with a plurality of parallel heat
exchange tubes, among which refrigerant is distributed and flown in a parallel manner.
The heat exchange tubes are orientated generally substantially perpendicular to a
refrigerant flow direction in the inlet, intermediate and outlet manifolds that are
in flow communication with the heat exchange tubes. When utilized in condenser and
evaporator applications, these heat exchangers may be designed in multi-pass configuration,
typically with a plurality of parallel heat exchange tubes within each refrigerant
pass, in order to obtain superior performance by balancing and optimizing heat transfer
and pressure drop characteristics. Single-pass configurations are typically more desirable
in the evaporator applications, since the refrigerant pressure drop plays a dominant
role in the evaporator performance.
[0004] However, there have been some obstacles to the use of the microchannel heat exchangers
within a refrigerant system. In particular, a problem, known as refrigerant maldistribution,
typically occurs in the microchannel heat exchanger manifolds when the two-phase flow
enters the manifold. A vapor phase of the two-phase flow has significantly different
properties, moves at different velocities and is subjected to different effects of
internal and external forces than a liquid phase. This causes the vapor phase to separate
from the liquid phase and to flow independently. The separation of the vapor phase
from the liquid phase has raised challenges, such as refrigerant maldistribution in
parallel flow heat exchangers.
[0005] It is known in certain refrigerant systems to utilize a distributor insert for delivering
refrigerant into an evaporator manifold (see, for example,
JP 6-159983). Such systems have been employed in refrigerated merchandisers, such as refrigeration
display cases. The proposed inlet distributor insert utilized in refrigerant display
cases would not solve the problem of refrigerant maldistribution mentioned above.
[0006] Another proposed heat exchanger is constructed of a plurality of plates. The heat
exchange refrigerant channels are formed of spaced plates, and remote ends of those
spaced plates provide inlet plenums for each refrigerant channel. The plates separate
adjacent plenums, and an insert tube extends through the plates and into the plenums.
This tube includes a plurality of orifices which direct refrigerant into the individual
plenums. This arrangement would not be practical for microchannel heat exchangers,
and would only be a practical construction for the one type of heat exchanger formed
of the spaced plates.
SUMMARY OF THE INVENTION
[0007] The present invention provides a microchannel heat exchanger comprising: a plurality
of heat transfer tubes; a manifold for communicating refrigerant into said plurality
of heat transfer tubes; and a distributor insert connectable to a source of refrigerant
and having a plurality of orifices in an outer periphery of said distributor insert,
characterised by dividing elements on an outer wall of said distributor insert such
that a plurality of distribution chambers are defined and associated with said plurality
of heat transfer tubes, wherein the plurality of orifices are arranged to uniformly
direct the refrigerant into the plurality of distribution chambers.
[0008] In one embodiment, the heat exchanger manifold is an inlet manifold of an evaporator
and, in another embodiment, the heat exchanger manifold is an intermediate manifold
of a condenser or an evaporator.
[0009] While all separation chambers may be of an identical size and the distributor dividing
elements uniformly spaced, in one embodiment, they are of a variable size to further
fine tune refrigerant distribution. Although the invention is disclosed in relation
to a two-phase refrigerant, it is also applicable to a single-phase refrigerant and
refrigerant-oil mixtures.
[0010] These and other features of the present invention can be best understood from the
following specification and drawings, the following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
Figure 1 schematically shows a basic exemplary refrigerant system.
Figure 2 shows a portion of an inlet manifold of an inventive heat exchanger.
Figure 3 shows a portion of an intermediate manifold of an inventive heat exchanger.
Figure 4 shows an exemplary design of a distributor insert.
Figure 5A shows a cross-sectional view of an exemplary heat transfer tube.
Figure 5B shows a cross-sectional view of an exemplary dividing element.
Figure 5C shows a side view of an exemplary dividing element of Figure 5B.
Figure 5D shows a cross-sectional view of another exemplary dividing element.
Figure 5E shows a side view of an exemplary dividing element of Figure 5D.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0012] A basic exemplary refrigerant system 20 is illustrated in Figure 1 including a compressor
22 compressing a refrigerant and delivering it downstream into a condenser 24. From
the condenser 24 the refrigerant passes through an expansion device 26 into an inlet
refrigerant pipe 28 leading into an evaporator 30. From the evaporator 30, the refrigerant
is returned to the compressor 22 to complete the closed-loop refrigerant circuit.
[0013] A portion of the evaporator 30, that includes an inlet refrigerant manifold 34 incorporating
the present invention, is illustrated in Figure 2. The evaporator 30 is a microchannel
heat exchanger, such heat exchangers particularly benefit from this inventive design
and construction. The benefits of this invention can extend to other applications,
such as, for instance, condenser applications.
[0014] Although the benefits of the invention will be disclosed in reference to a two-phase
refrigerant flow passing through the heat exchanger, single-phase refrigerant flows
and refrigerant-oil mixtures are also within the scope and can benefit from the invention.
[0015] As shown in Figure 2, the inlet refrigerant pipe 28 fluidly communicates with a distributor
insert 32, which provides a refrigerant flow path along its longitudinal axis. An
inlet manifold 34 of the evaporator 30 receives the distributor insert 32, and in
turn fluidly communicates with a plurality of heat exchange tubes 36 positioned generally
perpendicular to and downstream, with respect to the direction of refrigerant flow,
of the inlet manifold 34. The inlet refrigerant pipe 28 may be positioned at the end
of the inlet manifold 34, in the middle of the inlet manifold 34 or at any intermediate
location in-between. Further, the inlet refrigerant pipe 28 may comprise two inlet
refrigerant pipes connected at the opposite ends of the inlet manifold 34 or at any
intermediate locations. Obviously, more than two inlet refrigerant pipes can be utilized,
but all of them need to be fluidly connected and provide refrigerant paths into the
distributor insert 32.
[0016] As known, a plurality of heat transfer fins 38 may be disposed between and rigidly
attached, usually by a furnace braze process, to the heat exchange tubes 36, in order
to enhance external heat transfer and provide structural rigidity for the heat exchanger
30. Also, as known, each heat exchange tube 36 of a microchannel heat exchanger (evaporator)
30 typically has a plurality of small internal channels 41 providing multiple parallel
refrigerant flow paths along longitudinal axis of each heat exchange tube 36 (see
Figure 5A). The internal channels 41 enhance internal heat transfer and also provide
structural rigidity for the heat exchanger 30.
[0017] As also illustrated in Figure 2, a plurality of refrigerant distribution orifices
42 of a small size are formed to protrude through the walls of the distributor insert
32 and to provide the refrigerant paths from an internal cavity of the distributor
insert 32 into the inlet manifold 34. The distribution orifices 42 can be, for instance,
of a round shape, rectangular shape, oval shape or any other shape. Furthermore, the
distributor insert 32 has dividing elements 44 located on its periphery and rigidly
attached to the outside walls of the distributor insert 32. Upon positioning the distributor
insert 32 within the inlet manifold 34 of the evaporator 30, the dividing elements
44 form refrigerant separation chambers 46 within the internal cavity of the inlet
manifold 34, with each chamber communicating refrigerant downstream to at least one
heat exchange tube 36. Typically, each separation chamber would be fluidly connected
to several refrigerant distribution orifices 42 and several heat exchange tubes 46.
[0018] As mentioned above, a plurality of small refrigerant distribution orifices 42 is
provided to direct the refrigerant from the distributor insert 34 into a plurality
of separation chambers 46 defined by adjacent dividing elements 44 of the distributor
insert 32 within the cavity of the inlet manifold 34. The distance between the dividing
elements 44 can be uniform or can be adjusted to control the ultimate size of the
separation chambers 46 associated with any particular cluster of heat transfer tubes
36. This distance between the dividing elements 44 may vary from one cluster of heat
transfer tubes 36 to another, or in an extreme case, from one heat transfer tube 36
to another. As an example, for a single inlet refrigerant pipe 28 located at the end
of the inlet manifold 34, the size of the chambers 46 may be uniform along the longitudinal
axis of the manifold 34 or, for instance, may decrease from the manifold inlet end
to its remote end, where refrigerant velocity is expected to be lower. Any particular
configuration of the dividing elements 44 could depend on operational parameters and
particular application.
[0019] The distributor insert 32 receives the two-phase refrigerant from the inlet refrigerant
pipe 28 and delivers this refrigerant, through a plurality of small distribution orifices
42, into the heat exchanger manifold 34 that has been divided into the separation
chambers 46 by the dividing elements 44 of the distributor insert 32. A relatively
small size of the distributor insert 32 provides significant momentum for the refrigerant
flow preventing the phase separation of the two-phase refrigerant. The plurality of
the distribution orifices 42 uniformly directs the two-phase refrigerant into the
plurality of separation chambers 46 of the manifold 34 defined by the spaced dividing
elements 44 of the distributor insert 34. Since the size of the separation chambers
46 is relatively small, the refrigerant liquid and vapor phases do not have conditions
and time to separate, as in the prior art, when the two-phase refrigerant was expanded
into the entire inlet manifold cavity. Even in cases where some separation of the
refrigerant phases occurs, it would be within a relatively small manifold chamber
46, and on average, the refrigerant distribution would be still predominantly uniform
across the entire heat exchanger 30. Therefore, the inventive distributor concept
having a plurality of small distribution orifices 42 and dividing elements 44 prevents
refrigerant maldistribution and assures uniform refrigerant distribution into the
heat exchange tubes 36. In this manner, the refrigerant being delivered into the heat
exchange tubes 36 through the distributor insert orifices 42 and separation chambers
46 of the inlet manifold 34 will not have different quantities of vapor and liquid
phases flowing through different heat exchange tubes and heat exchanger tube clusters.
[0020] An outer periphery of the dividing elements 44 is tightly received within an inner
wall of the inlet manifold 34. Similarly, an inner periphery of the dividing elements
44 is closely received on an outer wall of the insert 32. In this manner, adjacent
separation chambers 46 are maintained predominantly isolated from each other preventing
refrigerant migration from one separation chamber 46 to another. Therefore, the overall
characteristics of the refrigerant flow into the heat exchange tubes 36 can be controlled
such that the effects of phase separation and/or refrigerant migration can be eliminated
or minimized.
[0021] Figure 3 shows another embodiment 300, wherein the manifold 301 is an intermediate
manifold, downstream of heat exchange tubes 302, and feeding the refrigerant into
heat exchange tubes 312. As shown, the distributor insert 306 has orifices 308, a
top separator plate 304, and intermediate separator plates 310. This embodiment functions
as in the prior embodiment to reduce refrigerant phase separation and maldistribution.
In this embodiment, the heat exchanger could be a condenser, or an evaporator.
[0022] The dividing elements 44 can be of any shape and form, such as, for instance, flat
plates (see Figure 5B), as long as they do not drastically block refrigerant flow
into the heat exchange tubes 36 and isolate one separation chamber 46 from another
(e.g. by a small clearance or mechanical/chemical bonding). Furthermore, dividing
elements 44 may have cutouts 200, in case the heat exchange tubes 36 penetrate inside
the inlet manifold 34 (see Figures 5B and 5C). The dividing elements 44 may be attached
to the distributor insert 32 mechanically (e.g. snapped into place into small groves
manufactured on the outer wall of the distributor insert 32), or by brazing, welding
or soldering. The dividing elements 44 may be also attached to the inner wall of the
inlet manifold 34 (e.g. by furnace brazing). Both attachment processes can be performed,
for instance, during furnace brazing of the entire heat exchanger 30.
[0023] Figures 5D and 5E show another embodiment, wherein the dividing elements 44 do not
include the cutout 200, but do include a groove or indentation 202. The purpose of
this indentation is to provide a holding cavity for brazing flux such that the distributor
insert can be inserted into a manifold and brazed upon construction of the overall
heat exchanger
[0024] In general, each of the disclosed embodiments teaches a distributor insert which
will receive refrigerant, and distribute refrigerant through a plurality of orifices
into separation chambers defined between dividing elements. Since the insert and the
dividing elements are attached to each other as a rigid sub-assembly, the entire assembly
can be inserted into a manifold. This will allow the use of this feature without requiring
any specific heat exchanger design, as has been the case in the prior art.
[0025] Although an embodiment of this invention has been disclosed, a worker of ordinary
skill in the art would recognize that certain modifications would come within the
scope of this invention, which is defined by the claims. For that reason, the following
claims should be studied to determine the scope of the invention.
1. A microchannel heat exchanger (30) comprising:
a plurality of heat transfer tubes (36);
a manifold (34) for communicating refrigerant into said plurality of heat transfer
tubes; and
a distributor insert (32) connectable to a source of refrigerant and having a plurality
of orifices (42) in an outer periphery of said distributor insert,
characterised by dividing elements (44) on an outer wall of said distributor insert such that a plurality
of distribution chambers (46) are defined and associated with said plurality of heat
transfer tubes, wherein the plurality of orifices are arranged to uniformly distribute
the two-phase refrigerant into the plurality of distribution chambers.
2. The heat exchanger as set forth in Claim 1, wherein said distributor insert and said
dividing elements improve refrigerant distribution in said heat exchanger.
3. The heat exchanger as set forth in Claim 1, wherein said dividing elements are spaced
uniformly along a length of said distributor insert.
4. The heat exchanger as set forth in Claim 1, wherein said dividing elements are attached
to said distributor insert by one of mechanical attachment and chemical bonding.
5. The heat exchanger as set forth in Claim 1, wherein the distributor insert has a round
cross-sectional shape.
6. The heat exchanger as set forth in Claim 1, wherein said manifold has an internal
bore of a round cross-sectional shape.
7. The heat exchanger as set forth in Claim 1, wherein the refrigerant passing through
said distributor insert is a two-phase refrigerant.
8. A refrigerant system comprising:
a compressor, said compressor for compressing a refrigerant and delivering it said
refrigerant downstream into a condenser, refrigerant from said condenser passing through
an expansion device and then into an evaporator, at least one of said condenser and
said evaporator being a heat exchanger as set forth in Claim 1.
9. The refrigerant system as set forth in Claim 8, wherein said distributor insert extends
from an upstream end of said manifold toward a downstream end of said manifold, and
the size of said separation chambers defined between adjacent ones of said dividing
elements is determined to optimize the flow of refrigerant within the plurality of
heat transfer tubes.
10. The refrigerant system as set forth in Claim 8, wherein said plurality of heat transfer
tubes, each including a plurality of channels, are spaced generally perpendicularly
to an upstream to downstream direction of said distributor insert.
11. The heat exchanger or refrigerant system as set forth in Claim 1 or 8, wherein the
heat exchanger is an evaporator, and said manifold is an inlet manifold.
12. The heat exchanger or refrigerant system as set forth in Claim 1 or 8, wherein said
manifold is an intermediate manifold.
13. The heat exchanger or refrigerant system as set forth in Claim 1 or 12, wherein said
distributor insert extends along only a portion of said manifold, and is not aligned
with heat transfer tubes communicating into said manifold, but is aligned with heat
transfer tubes communicating out of said manifold.
14. The heat exchanger or refrigerant system as set forth in Claim 1 or 8, wherein said
dividing elements are flat plates having a cutout portion at an outer periphery to
provide clearance for said heat transfer tubes.
1. Mikrokanalwärmetauscher (30), umfassend:
eine Mehrzahl von Wärmeübertragungsröhren (36);
einen Verteiler (34) zum Leiten von Kältemittel in die Mehrzahl von Wärmeübertragungs-röhren;
und
einen Verteilungseinsatz (32), der mit einer Quelle von Kältemittel verbindbar ist
und eine Mehrzahl von Mündungen (42) an einem Außenumfang des Verteilungseinsatzes
aufweist,
gekennzeichnet durch Teilungselemente (44) an einer Außenwand des Verteilungseinsatzes, derart, dass eine
Mehrzahl von Verteilungskammern (46) definiert wird und der Mehrzahl von Wärmeübertragungsröhren
zugeordnet wird, wobei die Mehrzahl von Mündungen derart angeordnet ist, dass sie
das zweiphasige Kältemittel gleichmäßig in der Mehrzahl von Verteilungskammern verteilt.
2. Wärmetauscher nach Anspruch 1, wobei der Verteilungseinsatz und die Teilungselemente
die Kältemittelverteilung in dem Wärmetauscher verbessern.
3. Wärmetauscher nach Anspruch 1, wobei die Teilungselemente entlang einer Längserstreckung
des Verteilungseinsatzes gleichmäßig beabstandet sind.
4. Wärmetauscher nach Anspruch 1, wobei die Teilungselemente durch eine von einer mechanischen
Anbringung und chemischer Bindung an dem Verteilungseinsatz angebracht sind.
5. Wärmetauscher nach Anspruch 1, wobei der Verteilungseinsatz eine runde Querschnittform
aufweist.
6. Wärmetauscher nach Anspruch 1, wobei der Verteiler eine Innenbohrung mit einer runden
Querschnittform aufweist.
7. Wärmetauscher nach Anspruch 1, wobei das Kältemittel, das durch den Verteilungseinsatz
gelangt, ein zweiphasiges Kältemittel ist.
8. Kältesystem, umfassend:
einen Kompressor, wobei der Kompressor zum Verdichten eines Kältemittels und zum Leiten
des Kältemittels stromabwärts in einen Kondensator dient, wobei Kältemittel von dem
Kondensator durch eine Ausdehnungsvorrichtung und dann in einen Verdampfer gelangt,
wobei wenigstens einer von dem Kondensator und dem Verdampfer ein Wärmetauscher nach
Anspruch 1 ist.
9. Kältesystem nach Anspruch 8, wobei sich der Verteilungseinsatz von einem Stromaufwärtsende
des Verteilers zu einem Stromabwärtsende des Verteilers erstreckt und die Größe der
Trennungskammern, die zwischen benachbarten der Teilungselemente definiert sind, festgelegt
ist, um den Fluss von Kältemittel innerhalb der Mehrzahl von Wärmeübertragungsröhren
zu optimieren.
10. Kältesystem nach Anspruch 8, wobei die Mehrzahl von Wärmeübertragungsröhren, die jeweils
eine Mehrzahl von Kanälen aufweisen, allgemein senkrecht zu einer Stromaufwärtsstromabwärts-Richtung
des Verteilungseinsatzes beabstandet ist.
11. Wärmetauscher oder Kältesystem nach Anspruch 1 oder 8, wobei der Wärmetauscher ein
Verdampfer ist und der Verteiler ein Einlassverteiler ist.
12. Wärmetauscher oder Kältesystem nach Anspruch 1 oder 8, wobei der Verteiler ein Zwischenverteiler
ist.
13. Wärmetauscher oder Kältesystem nach Anspruch 1 oder 12, wobei der Verteilungseinsatz
sich nur an einem Teil des Verteilers entlang erstreckt und nicht an den Wärmeübertragungsröhren
ausgerichtet ist, die in den Verteiler eingehen, sondern an den Wärmeübertragungsröhren
ausgerichtet ist, die aus dem Verteiler austreten.
14. Wärmetauscher oder Kältesystem nach Anspruch 1 oder 8, wobei die Teilungselemente
flache Platten sind, die an einem Außenumfang einen Aussparungsabschnitt aufweisen,
um Platz für die Wärmeübertragungsröhren zu schaffen.
1. Échangeur (30) de chaleur à microcanaux comprenant :
une pluralité de tubes (36) de transfert de chaleur ;
un collecteur (34) servant à mettre le réfrigérant en communication avec ladite pluralité
de tubes de transfert de chaleur ; et
un insert (32) de distribution pouvant être relié à la source d'un réfrigérant et
ayant une pluralité d'orifices (42) sur une périphérie extérieure dudit insert de
distribution,
caractérisé par des éléments diviseurs (44) situés sur une paroi extérieure dudit insert de distribution
de telle sorte qu'une pluralité de chambres (46) de distribution sont définies et
associées à ladite pluralité de tubes de transfert de chaleur, la pluralité d'orifices
étant conçue pour distribuer uniformément le réfrigérant diphasique dans la pluralité
de chambres de distribution.
2. Échangeur de chaleur selon la revendication 1, dans lequel ledit insert de distribution
et lesdits éléments diviseurs améliorent la distribution du réfrigérant dans ledit
échangeur de chaleur.
3. Échangeur de chaleur selon la revendication 1, dans lequel lesdits éléments diviseurs
sont espacés uniformément sur une longueur dudit insert de distribution.
4. Échangeur de chaleur selon la revendication 1, dans lequel lesdits éléments diviseurs
sont fixés audit insert de distribution soit par fixation mécanique soit par liaison
chimique.
5. Échangeur de chaleur selon la revendication 1, dans lequel l'insert de distribution
a une section transversale de forme arrondie.
6. Échangeur de chaleur selon la revendication 1, dans lequel le collecteur a un trou
intérieur dont la section transversale est de forme arrondie.
7. Échangeur de chaleur selon la revendication 1, dans lequel le réfrigérant traversant
ledit insert de distribution est un réfrigérant diphasique.
8. Système réfrigérant comprenant :
un compresseur, ledit compresseur servant à compresser un réfrigérant et à fournir
ledit réfrigérant en aval à un condensateur, le réfrigérant dudit condensateur traversant
un dispositif d'expansion puis arrivant dans un évaporateur, au moins l'un desdits
condensateur et évaporateur étant un échangeur de chaleur selon la revendication 1.
9. Système réfrigérant selon la revendication 8, dans lequel ledit insert de distribution
s'étend d'une extrémité amont dudit collecteur vers une extrémité aval dudit collecteur,
et la taille desdites chambres de séparation définies entre des éléments diviseurs
adjacents desdits éléments diviseurs est définie de sorte à optimiser le flux de réfrigérant
à l'intérieur de la pluralité de tubes de transfert de chaleur.
10. Système réfrigérant selon la revendication 8, dans lequel ladite pluralité de tubes
de transfert de chaleur, comprenant chacun une pluralité de canaux, est espacée généralement
perpendiculairement à une direction d'amont en aval dudit insert de distribution.
11. Échangeur de chaleur ou système réfrigérant selon la revendication 1 ou la revendication
8, dans lesquels l'échangeur de chaleur est un évaporateur, et ledit collecteur est
un collecteur d'entrée.
12. Échangeur de chaleur ou système réfrigérant selon la revendication 1 ou la revendication
8, dans lesquels ledit collecteur est un collecteur intermédiaire.
13. Échangeur de chaleur ou système réfrigérant selon la revendication 1 ou la revendication
12, dans lesquels l'insert de distribution s'étend le long d'une partie dudit collecteur
seulement, et n'est pas aligné avec les tubes de transfert de chaleur mis en communication
à l'intérieur dudit collecteur, mais est aligné avec les tubes de transfert de chaleur
mis en communication à l'extérieur dudit collecteur.
14. Échangeur de chaleur ou système réfrigérant selon la revendication 1 ou la revendication
8, dans lesquels lesdits éléments diviseurs sont des plaques planes dont une partie
est découpée sur une périphérie extérieure pour laisser de l'espace pour lesdits tubes
de transfert de chaleur.