U.S. patent application number 14/541867 was filed with the patent office on 2016-05-19 for shear flow condenser.
The applicant listed for this patent is Hamilton Sundstrand Corporation. Invention is credited to Robert S. Downing.
Application Number | 20160138874 14/541867 |
Document ID | / |
Family ID | 55961363 |
Filed Date | 2016-05-19 |
United States Patent
Application |
20160138874 |
Kind Code |
A1 |
Downing; Robert S. |
May 19, 2016 |
SHEAR FLOW CONDENSER
Abstract
A plate-fin condenser includes a plate body defining an interior
channel having a fluid inlet, a first interior channel section
having a first cross-sectional area in fluid communication with the
inlet, a second interior channel section downstream of the first
interior channel section, and a fluid outlet in fluid communication
with the converging interior channel. The second interior channel
section has a second cross-sectional area that is smaller than the
first cross-sectional area.
Inventors: |
Downing; Robert S.;
(Rockford, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hamilton Sundstrand Corporation |
Charlotte |
NC |
US |
|
|
Family ID: |
55961363 |
Appl. No.: |
14/541867 |
Filed: |
November 14, 2014 |
Current U.S.
Class: |
165/166 |
Current CPC
Class: |
F28D 9/0093 20130101;
F28D 9/00 20130101; F28F 3/025 20130101; F28F 13/08 20130101; F28D
2021/0063 20130101; F28B 1/00 20130101 |
International
Class: |
F28D 9/00 20060101
F28D009/00 |
Claims
1. A plate condenser, including: a plate body defining an interior
channel including, an fluid inlet; a first interior channel section
having a first cross-sectional area in fluid communication with the
inlet; a second interior channel section downstream of the first
interior channel section, wherein the second interior channel
section has a second cross-sectional area that is smaller than the
first cross-sectional area; and a fluid outlet in fluid
communication with the second interior channel.
2. The plate condenser of claim 1, wherein the plate body is in
thermal communication with fin thermal transfer devices and
channels laterally defined thereby.
3. The plate condenser of claim 1, wherein the second interior
channel is tapered in cross-sectional area.
4. The plate condenser of claim 1, wherein the second interior
channel is uniform in cross-sectional area.
5. The plate condenser of claim 1, wherein the interior channel is
connect together with one or more headers, wherein each header
directs flow from one interior channel to another interior channel
to change the direction of flow.
6. The plate condenser of claim 1, further comprising an
intermediate interior channel section between the first and second
interior channel sections that converges, such that the
intermediate and second channel sections successively reduce in
cross-sectional area.
7. The plate condenser of claim 6, wherein the first interior
channel is defined by uniform shaped walls parallel with an axial
direction of flow within the first interior channel.
8. The plate condenser of claim 7, wherein the intermediate and
second interior channel sections are defined by at least one wall
that is angled relative to the axial direction of flow.
9. The plate condenser of claim 8, wherein the intermediate and
second interior channel sections are two tapered converging channel
sections, wherein the at least one wall is a single angled wall
defining the two tapered converging channels.
10. A method of condensing a fluid, comprising: increasing a
velocity of a working fluid within an interior channel of a plate
condenser between a fluid inlet and a fluid outlet thereof while
condensing the working fluid within the interior channel.
11. The method of claim 10, wherein increasing the velocity of the
working fluid routing the working fluid through a converging
cross-sectional area of the interior channel of the plate
condenser.
12. The method of claim 10, wherein increasing the velocity of the
working fluid routing the working fluid through a uniformly
converging cross-sectional area of the interior channel of the
plate condenser.
13. The method of claim 10, wherein increasing the velocity of the
working fluid routing the working fluid through a non-uniformly
converging cross-sectional area of the interior channel of the
plate condenser.
Description
BACKGROUND
[0001] 1. Field
[0002] The present disclosure relates to heat exchangers, more
specifically to condensers for condensing fluids in their vapor
state.
[0003] 2. Description of Related Art
[0004] Condensers can include an arrangement whereby a working
fluid, i.e. a vapor, is cooled by a cooler stream (coolant) such
that the amount of heat removed by the coolant is used to condense
all or some of the vapor flow. A plate fin condenser includes the
cooling and condensing fluid flow in alternating layers which are
separated by solid sheets, called parting sheets.
[0005] Each plate of a typical plate fin condenser includes an
interior channel(s) for routing a working fluid (vapor) flow
therethrough. The flow space for the condensing vapor is between
parting sheets. Both the vapor and coolant flow spaces include a
series of conductive fins which are metallurgically or otherwise
bonded to both sides of each space. For example, each plate can be
connected together and/or separated by thermal transfer fins which
create fin channels for a coolant to pass therethrough.
[0006] The thermal transfer fins and the fin channel defined
thereby can be arranged such that coolant flows orthogonally to the
working fluid flowing within the interior channel of the plates.
The condensing working fluid can contain a pure or mixture of
condensable vapors and, in some cases, non-condensable gases (e.g.,
fluids that will not condense at the operating temperature of the
condenser).
[0007] Traditionally, the interior channel is defined within the
plates as linear channels of constant cross-sectional area.
However, as portions of the working fluid condense on the walls of
the interior channel, the remaining vapor flow slows down. In some
cases, this creates a buildup of condensate within the interior
channel in such a manner that the thickness of the condensate film
grows non-uniformly along the length of the interior channel.
[0008] The condensation layer is the principle resistance to heat
transfer, such that a thickened layer significantly reduces the
efficiency of the condenser. The reduced local heat transfer will
require longer channels to condense the working fluid completely
and/or a large enough temperature gradient to negate these effects.
Also, non-condensates gases will blanket the local condensing
surfaces when the vapor velocities are too small and this can
further limit the efficiency of the condenser.
[0009] Local non-condensable gases are convectively transferred to
the condensate surface with the condensing vapor flow. This
mechanism enriches the non-condensable fraction near the condensing
surface and inhibits the condensation rate because the partial
pressure of the vapor is reduced and the vapor must diffuse through
the layer.
[0010] Such conventional methods and systems have generally been
considered satisfactory for their intended purpose. However, there
is still a need in the art for improved condensers. The present
disclosure provides a solution for this need.
SUMMARY
[0011] In at least one aspect of this disclosure, a plate condenser
includes a plate body defining an interior channel having a fluid
inlet, a first interior channel section having a first
cross-sectional flow area in fluid communication with the inlet, a
second interior channel section downstream of the first interior
channel section, and a fluid outlet in fluid communication with the
second interior channel. The second interior channel section has a
second cross-sectional flow area that is smaller than the first
cross-sectional area.
[0012] The plate body is in thermal communication with fin thermal
transfer devices and channels laterally defined thereby. The second
interior channel can be tapered in cross-sectional flow area. The
second interior channel can be uniform in cross-sectional area. The
interior channel can be connected together with one or more
headers, wherein each header directs flow from one interior channel
to another interior channel to change the direction of flow.
[0013] The plate condenser can further include an intermediate
interior channel section between the first and second interior
channel sections that converges, such that the intermediate and
second channel sections successively reduce in cross-sectional
area. The first interior channel can be defined by uniform shaped
walls parallel with an axial direction of flow within the first
interior channel.
[0014] The intermediate and second interior channel sections can be
defined by at least one wall that is angled relative to the axial
direction of flow. The intermediate and second interior channel
sections can include two tapered converging channel sections,
wherein the at least one wall is a single angled wall defining the
two tapered converging channels.
[0015] In at least one aspect of this disclosure, a method of
condensing a fluid includes increasing a velocity of a working
fluid (e.g., uncondensed vapor) within an interior channel of a
plate condenser between a fluid inlet and a fluid outlet thereof
while condensing the working fluid on the walls of the interior
channel. Increasing the velocity of the working fluid can include
routing the working fluid through a converging cross-sectional area
of the interior channel of the plate condenser. In certain
embodiments, increasing the velocity of the working fluid can
include routing the working fluid through a uniformly converging
cross-sectional area of the interior channel of the plate
condenser. In other embodiments, increasing the velocity of the
working fluid can include routing the working fluid through a
non-uniformly converging cross-sectional area of the interior
channel of the plate condenser.
[0016] These and other features of the systems and methods of the
subject disclosure will become more readily apparent to those
skilled in the art from the following detailed description taken in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] So that those skilled in the art to which the subject
disclosure appertains will readily understand how to make and use
the devices and methods of the subject disclosure without undue
experimentation, embodiments thereof will be described in detail
herein below with reference to certain figures, wherein:
[0018] FIG. 1A is a schematic, perspective view of an embodiment of
a plate condenser in accordance with this disclosure, depicting a
working fluid flowing therethrough within the interior channel
thereof;
[0019] FIG. 1B is a partial, schematic, exploded view of the plate
condenser shown in FIG. 1A, depicting a plurality of plates
assembled together;
[0020] FIG. 2 is a schematic view of a uniformly tapered channel in
accordance with this disclosure, showing in principle, shear flow
condensing on walls thereof; and
[0021] FIG. 3 is a graph depicting the flow patterns that occur
over a range of liquid and vapor mass flows in a closed channel
which are applicable to flow in a condenser. Flow patterns are the
vapor-liquid phase distribution such as bubbles within a liquid
flow or liquid flowing as a film on wall with a vapor core.
DETAILED DESCRIPTION
[0022] Reference will now be made to the drawings wherein like
reference numerals identify similar structural features or aspects
of the subject disclosure. For purposes of explanation and
illustration, and not limitation, an illustrative view of an
embodiment of a plate condenser in accordance with the disclosure
is shown in FIG. 1A and is designated generally by reference
character 100. The systems and methods described herein can be used
to at least partially condense vapor flow of a working fluid (e.g.,
a refrigerant).
[0023] In at least one aspect of this disclosure, referring to
FIGS. 1A and 1B, a plate-fin condenser 100 includes a plate body
101 defining an interior channel having channel sections 103, 105,
and 107. The interior channel includes a fluid inlet 109 in fluid
communication with a vaporized working fluid 119 (e.g., from a heat
sink with the working fluid flowing therethrough).
[0024] A first interior channel section 103 has a first
cross-sectional area in fluid communication with the inlet 109.
Vapor can flow through the inlet 109 into the first interior
channel section 103. As shown in FIG. 1A, the first interior
channel section 103 includes a uniform cross-sectional area with
walls that are parallel with an axial direction of flow, but it is
contemplated that the cross-sectional area of the first interior
channel section 103 can be variable along the length of the first
channel section 103.
[0025] The condenser 100 further includes a second interior channel
section 107 downstream of the first interior channel section 103.
At least a portion of the second interior channel section 107
includes a second cross-sectional area that is smaller than the
first cross-sectional area of the first interior channel section
103. For example, second interior channel section 107 includes a
tapered shape defined by wall 107a. In other embodiments, it is
contemplated that the second interior channel section 107 can
include a uniform cross-sectional area along its length with the
cross-sectional area smaller than that of first interior channel
section 103. In certain embodiments, the cross-sectional area of
the second interior channel section 107 can be defined such that
vapor flow, condensate thickness, and/or liquid flow are optimized
for thermal transfer efficiency.
[0026] An approach to optimize the cross-section would reduce the
passage size in a proportional manor to the vapor that in
uncondensed. For example if the vapor flow at the end of the
section is estimated to be half that of the inlet, the flow area at
the end would be sized to be half the value at the start of the
passage. Since liquid densities greatly exceed vapor densities, to
a first order the vapor velocity will remain nearly constant. With
a near constant vapor velocity the condensate film will be thinned
by the "shear" force of the vapor flow and the heat transfer
coefficient and subsequent condensation rate will be enhanced over
a channel of uniform cross-sectional area. Because the condensation
rate, film thickness, and vapor velocity are dependent quantities,
the tapering rate for near uniform vapor velocity must be
determined iteratively or alternately by a numerical model which
determines the local conditions like the condensation heat transfer
coefficient and condensation rate.
[0027] A prescribed optimum area profile is not necessary to
improve the condensation process over a non-tapered design. Any
design with a reducing (e.g., tapered) flow area in the direction
of flow will improve the heat exchange process, resulting in a
smaller device needed or a required coolant-to-vapor temperature
difference.
[0028] A fluid outlet 111 is in fluid communication with the second
interior channel section 107. The fluid outlet 111 can also be
connected to a suitable heat exchanger location (e.g., recycled to
a heat sink to absorb heat and convert the liquid working fluid 121
into vapor).
[0029] As shown in FIG. 1A, one or more intermediate channel
sections 105 are disposed between the first interior channel
section 103 and the second interior channel section 107, however,
it is contemplated that the first and second interior channel
sections 103, 107 be directly adjacent with no intermediate channel
section 105 therebetween. The intermediate interior channel section
105 can have any suitable cross-sectional area (e.g., uniform or
variable) and can also be tapered (e.g., defined by the opposite
side of wall 107a).
[0030] The interior channel sections 103, 105, 107 are connected
together with one or more headers 113. Each header 113 directs flow
from one interior channel to another interior channel to change the
direction of flow in a labyrinth manner within the plate body 101.
As would be appreciated the headers 113 can be integrated as part
of the plate body 101 instead of a separate component as shown.
[0031] Referring to FIG. 1B, a core of the condenser 100 with
alternating vapor passages (i.e., interior channel sections 103,
105, 107 defined in plate body 101) and fin channels 117 (i.e.,
defined by the fins 115) is shown. The plate body 101 can be in
thermal communication with fin thermal transfer devices 115 and fin
channels 117 laterally defined thereby. As shown in FIGS. 1A and
1B, the fin thermal transfer devices are formed by accordion shaped
sheet metal. In addition, as shown in FIG. 1B, a plurality of plate
bodies 101 as described above can be assembled together around one
or more fin thermal transfer devices 115. Any other suitable
thermal transfer device and/or shape thereof is contemplated herein
instead of or in conjunction with the fin thermal transfer devices
115.
[0032] As shown, a coolant flow 123 can be passed through the fin
channels 117 in any suitable manner to remove heat from the
vaporized working fluid 119 in order to convert the vaporized
working fluid 119 to liquid working fluid 123. While, the interior
channel sections 103, 105, 107 are shown to be circular with
decreasing size, the interior channel sections 103, 105, 107 can be
any suitable shape (e.g., non-circular cross-section) and can have
fins therein. Also, each plate body 101 can be in thermal
communication with multiple fin thermal transfer devices 115.
[0033] Referring to FIG. 2, the phenomena and flow patterns of a
converging cross-sectional area for condensation is illustrated.
The vapor core, with a high velocity extends far down the tube
length. This flow pattern, with the liquid on the wall as a film is
termed annular and it is the preferred condition for condensation.
Of note are two other flow regimes, plug and chug. These regimes
describe conditions where there is an oscillating nature to flow,
with mostly liquid "slugs" are followed by large bubbles. This flow
distribution is not favorable to condensation.
[0034] FIG. 3 shows a "flow map" which describes the flow patterns
for a vapor and liquid flowing in a tube with various mass fluxes.
Mass flux is the mass flow rate (.about.kg/sec) divided by the tube
flow area (.about.m.sup.2). FIG. 3 is one of several semi-empirical
"flow regime maps" that predicts the flow pattern for a given vapor
flux and liquid flux. As can be seen, a plate condenser 100 having
a tapered cross-sectional area as the embodiment of FIG. 1A
maintains a higher vapor flux with higher liquid flux than a
non-tapered traditional system. As can be seen, the flow is annular
inside the interior channel in this condition, which is beneficial
for heat transfer. Plate condenser 100 with a tapered cross-section
allows for transition from annular flow to frothy and or bubbly
flow which provides near-ideal heat transfer and condensation. For
contrast, traditional plate condensers allow for annular flow to
transition into slug flow, and then into a plug flow for less than
ideal heat transfer.
[0035] In at least one aspect of this disclosure, a method of
condensing a fluid includes increasing (or slowing the rate of
decrease) a velocity of a vaporized working fluid 119 within an
interior channel (e.g., second interior channel section 107) of a
plate condenser 100 between a fluid inlet 109 and a fluid outlet
111 thereof while condensing the working fluid within the interior
channel. Not significantly decreasing the working fluid velocity
can include routing the working fluid through a converging
cross-sectional area of the interior channel of the plate
condenser. In certain embodiments, increasing the velocity of the
working fluid can include routing the working fluid through a
uniformly converging cross-sectional area of the interior channel
of the plate condenser. In embodiments, increasing the velocity of
the working fluid can include routing the working fluid through a
non-uniformly converging cross-sectional area of the interior
channel of the plate condenser.
[0036] The plate condenser 100 can be utilized in any suitable
thermal transfer application. For example, two-phase thermal
management systems are becoming widely used for cooling computer
systems, electronics, weapons, actuation devices, etc. In these
systems, the heat must be rejected by condensation to an outside
heat sink (e.g., water, air or fuel in a condenser). Similarly in
vapor-cycle refrigeration or air conditioning, the heat from the
loop must be rejected in a condenser. Also, Rankine power
generation cycles also require a condenser for waste heat
rejection.
[0037] A shear flow condenser is most applicable to any of these
applications where the condenser cannot be readily drained by
gravity, and/or a size and/or weight reduction is advantageous. For
example, shear flow condensers are highly relevant to the
.mu.-gravity environment of space.
[0038] Another advantage to tapering the condensing vapor core is
the increased stability of flow between condenser passages and into
and out of the headers. The higher velocities that occur in a
tapered design increase the pressure drop which has a stabilizing
effect. Without taper, the deceleration of the vapor results into a
momentum recovery and a smaller pressure drop. Flow reversal can
occur in condensers that have small or no pressure drops. These
stability issues can reduce condenser performance and impact system
operation.
[0039] The methods and systems of the present disclosure, as
described above and shown in the drawings, provide for a plate
condenser with superior properties including improved thermal
efficiency relative to traditional devices. While the apparatus and
methods of the subject disclosure have been shown and described
with reference to embodiments, those skilled in the art will
readily appreciate that changes and/or modifications may be made
thereto without departing from the spirit and scope of the subject
disclosure.
* * * * *