Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HEAT AND ENERGY EXCHANGE
DESCRIPTION
[001] This application claims priority to U.S. Provisional Application No.
61/347,446, filed May 23, 2010, the contents of which are incorporated herein
by
reference. This application is related to co-pending U.S. Application No.
12/585,981,
filed September 30, 2009, the contents of which are incorporated by reference,
and
which itself claims the benefit of U.S. Provisional Application No.
61/101,227, filed
September 30, 2008.
Field
[002] Materials, components, and methods consistent with the present
disclosure are directed to the fabrication and use of micro-scale channels
with a fluid,
where the micro-scale channels are arranged according to certain macroscopic
configurations so as to at least partially control the temperature and flow of
the fluid.
Background
[003] A volume of fluid, such as air, can be characterized by a temperature
and pressure. When considered as a collection of constituent particles,
comprising, for
example, molecules of oxygen and nitrogen, the volume of fluid at a given
temperature can also be characterized as a distribution of constituent
particle speeds.
This distribution can be characterized, generally, by an average speed which
is
understood to bear a relationship with the temperature of the fluid (as a gas,
for
example).
[004] Accordingly, the internal thermal energy of a fluid can provide a
source of energy for applications related to heating, cooling, and the
generation of
fluid flow.
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SUMMARY
[005] In one aspect, embodiments can provide a system that utilizes one or
more micro-scale channels (a "micro channel") configured to accommodate the
flow
of a fluid, and where the walls of the micro channel and the constituent
particles in the
fluid are configured such that collisions between the constituent particles
and the
walls of the micro channel are substantially specular. Moreover the micro
channel can
be arranged in a macroscopic configuration to provide at least one wall with
at least a
first wall portion that is at least approximately planar, a second wall
portion that is at
least approximately planar, a third wall portion that is approximately planar,
a first
intermediate wall portion, and a second intermediate wall portion, where a
boundary
of the first wall portion is contiguous with a first boundary of the first
intermediate
wall portion, a first boundary of the second wall portion is contiguous with a
second
boundary of the first intermediate wall portion, a second boundary of the
second wall
portion is contiguous with a first boundary of the second intermediate wall
portion,
and a boundary of the third wall portion is contiguous with a second boundary
of the
second intermediate wall portion, such that the first wall portion, the first
intermediate
wall portion, the second wall portion, the second intermediate wall portion,
and the
third wall portion form a contiguous wall of a portion of the micro channel.
Further
still, embodiments can provide that a first normal to the approximate plane
defined by
the first wall portion is not parallel to a second normal to the approximate
plane
defined by the second wall portion, and is also not parallel to a third normal
to the
approximate plane defined by the third wall portion, and where the second
normal is
also not parallel to the third normal. Further still, embodiments can provide
that the
angle offset between the first normal and the second normal is less than 90
degrees,
and is approximately the same as the angle offset between the second normal
and the
third normal. Where the separation between the first wall portion and the
second wall
portion is at least N times the largest width of the micro channel over that
separation
(where N can be an integer), the angle offset between the first normal and the
second
normal can be less than N/10 degrees. Likewise, where the separation between
the
second wall portion and the third wall portion is at least N times the largest
width of
the micro channel over that separation, the angle offset between the second
normal
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and the third normal can be less than N/10 degrees. For example purposes only,
where
the separation between the first wall portion and the second wall portion (and
the
separation between the second wall portion and the third wall portion) is at
least
twenty-five times the largest width of the micro channel over that separation,
the
angle offset between the first normal and the second normal (and the second
normal
and the third normal) can be less than 2.5 degrees. Likewise, for example
purposes
only, where the separation between the first wall portion and the second wall
portion
is at least fifty times the largest width of the micro channel over that
separation, the
angle offset between the first normal and the second normal can be less than 5
degrees.
[006] In another aspect, embodiments can provide for the the manipulation
of flow and temperature of a volume of fluid, where the fluid can comprise
molecules,
and can allow for the population of molecular vibrational levels through
enhanced
heating of a volume of the fluid. Where such vibrationally-excited molecules
are
allowed to relax, embodiments can allow for the creation and manipulation of
electromagnetic radiation emitted thereby.
[007] In a further aspect, embodiments can provide for the manipulation of
flow and temperature of a volume of fluid, and can provide for practical
applications
ranging from heating and cooling, refrigeration, electricity generation,
coherent and
non-coherent light emission, gas pumping, plasma and particle beam production,
particle beam acceleration, chemical processes, and others.
[008] Additional objects and advantages of the disclosure will be set forth in
part in the description which follows, and in part will be obvious from the
description,
or may be learned by practice of embodiments consistent with the disclosure.
The
objects and advantages can be realized and attained by means of the elements
and
combinations particularly pointed out in the appended claims.
[009] It is to be understood that both the foregoing general description and
the following detailed description are exemplary and explanatory only and are
not
restrictive of the invention, as claimed.
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BRIEF DESCRIPTION OF THE DRAWINGS
[010] The accompanying drawings, which are incorporated in and constitute
a part of this specification, illustrate an embodiment of the disclosure and
together
with the description, serve to explain the principles of the disclosure.
[011 ] Figure 1 depicts an exemplary heat exchange system consistent with
the present disclosure;
[012] Figure 2 is an exemplary view of the micro channels within an
accelerating element of the system of FIG. 1;
[013] Figure 3 is an exemplary illustration of a specular collision consistent
with the present disclosure;
[014] Figure 4 is an exemplary view of the micro channels within a
decelerating element of the system of FIG. 1;
[015] Figure 5 depicts an exemplary view of an interface and a connection
channel connecting an accelerating element and a decelerating element of the
system
of FIG. 1; and
[016] Figure 6 depicts exemplary normal vectors to the walls of the micro
channels and the angular offsets within an accelerating element of the system
of FIG.
1.
DESCRIPTION OF THE EMBODIMENTS
[017] Reference will now be made in detail to the present embodiment
(exemplary embodiment) of the disclosure, characteristics of which are
illustrated in
the accompanying drawings. Wherever possible, the same reference numbers will
be
used throughout the drawings to refer to the same or like parts.
[018] FIG. 1 depicts a view of exemplary heat exchange system 100
consistent with the present disclosure. Pump 150 is configured to generate
and/or
maintain a flow of fluid (such as air, for example) from channel 152 to
channel 151.
Arrow 118 indicates an exemplary fluid flow into channel 151, and arrow 128
indicates an exemplary fluid flow from channel 152.
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[019] In general, consistent with the present disclosure, sub-system 110 can
include a plurality of accelerating elements 115, where each accelerating
element 115
includes micro channels (to be described further below) in fluid communication
with
channel 151. Further, sub-system 120 can include a plurality of decelerating
elements
125, where each decelerating element 125 also includes micro channels (to be
described further below) in fluid communication with channel 152. Further
still,
consistent with an exemplary embodiment of the present disclosure, there can
be a
one-to-one correspondence between each of micro channel of each accelerating
element 115 and each of micro channel of each decelerating element 125, where
the
one-to-one correspondence can be realized by ensuring that the micro channel
of each
accelerating element 115 is in fluid communication with a micro channel of a
decelerating element 125 through interface 130.
[020] Ina preferred embodiment, each pair of accelerating element 115 and
decelerating element 125 can transfer 100 watts from the cold side
(accelerating
element 115) to the hot side (decelerating element 125). The dimensions of
such an
accelerating element 115 within such a 100 watt pair of accelerating and
decelerating
elements can be 100 millimeters by 100 millimeters. In a further embodiment,
an
additional heat exchange element (not shown) may be affixed to each
accelerating
element 115 and decelerating element 125. In an embodiment consistent with the
disclosure, the additional heat exchange element can be substantially planar
(such as
accelerating element 115 and decelerating element 125 are planar) and serve to
conduct heat away from decelerating element 125 into the ambient air (by
providing
additional surface area to dissipate such energy) or serve to conduct heat to
accelerating element 115 from the ambient air (again, by providing provide
additional
surface area for cooling purposes). The additional heat exchange element can
be 100
millimeters by 100 millimeters, thereby making the dimensions of the combined
accelerating element 115 and additional heat exchange element 100 millimeters
by
200 millimeters, and making the dimensions of the combined decelerating
element
125 and additional heat exchange element 100 millimeters by 200 millimeters in
one
embodiment. In the embodiment depicted in FIG. 1, with twenty (20) such pairs
of
accelerating element 115 and decelerating element 125 depicted, system 100 can
be
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capable of transferring 2 kilowatts from sub-system 110 to sub-system 120. In
a
further preferred embodiment, with 35 such pairs capable of transferring 3.5
kilowatts
from a cold side to a hot side, the height, H, of a 3.5 kilowatt system can be
approximately 300 millimeters. Where interface 130 is 10 millimeters wide (and
taking into account the additional heat exchange elements described above),
the
overall dimensions of such a 3.5 kilowatt system can be 300 millimeters by 210
millimeters by 200 millimeters. Further, the exemplary diameter of channel 151
and
channel 152 can be 25 millimeters or more. Furthermore, in such an exemplary
3.5
kilowatt system, where the fluid is air, pump 150 can be a 300-500 watt air
pump.
Further still, in such an exemplary embodiment, the air to be circulated
through
system 100 can be drawn from the immediate environment of system 100.
[021] Channel 151 is in fluid communication with channel 152 through a
plurality of micro channels within the plurality of accelerating elements 115,
interface
130, and decelerating elements 125. Arrow 138 depicts the flow of fluid from
accelerating element 115 to decelerating element 125 through interface 130.
[022] FIG. 2 is a schematic view of micro channel 210 within an exemplary
accelerating element 115 of FIG. 1. Channel 151 is depicted as an opening in
accelerating element 115, and in fluid communication with micro channel 210.
The
scale of micro channel 210 as depicted in FIG. 2 is for illustration purposes.
Micro
channel 210 can be engineered to be small (i.e., with an internal surface area
that may
be as small as approximately 3e-11 m^2 per linear micron to 6e-10 m^2 per
linear
micron in a preferred embodiment, which can correspond, respectively, to a
channel
with an approximate diameter of 9 microns to 180 microns). As depicted in FIG.
2 in
an exemplary embodiment, micro channel 210 is approximately confined to a
planar
region (i.e., accelerating element 115) and exhibits a spiral such that a
fluid entering
from channel 151 enters micro channel 210, describing arcs of increasing
radius until
the fluid enters entering linear channel 220. In a preferred embodiment, the
total
length of micro channel 210 from channel 151 until reaching linear channel 220
can
be approximately 10 mm to more than 1 meter. Further still, as discussed
above, in a
preferred embodiment where accelerating element 115 is one of a 100 watt pair
of
accelerating and decelerating elements, the width W can be 100 millimeters.
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[023] Furthermore, in a preferred embodiment, the walls of micro channel
210 can be substantially specular, FIG. 3 depicts a portion of FIG. 2 in more
detail.
Specifically, arrow 325 represents a velocity component of constituent
particle 310
before constituent particle 310 collides with wall 305. (Wall 305 is an
enlarged view
of an exemplary wall of micro channel 210, and constituent particle 310
corresponds
to a constituent particle in an exemplary fluid flowing through micro channel
210
according to a preferred embodiment.) Normal 306 represents an axis that is
perpendicular to the plane defined by wall 305. Arrow 335 represents a
velocity
component of constituent particle 310 after constituent particle 310 collides
with wall
305.. As used herein, a specular collision between constituent particle 310
and wall
305 is a collision in which the velocity component of constituent particle 310
parallel
to plane 302 determined by local portion 301 of wall 305 proximal to the
collision
between constituent particle 310 and wall 305, is substantially the same
before and
after the collision. Moreover, during a specular collision, the speed of
constituent
particle 310 associated with the velocity component perpendicular to the plane
of wall
305 can be substantially the same before and after the collision. One skilled
in the art
should appreciate that the term "specular collision" as used herein should not
be
interpreted to apply to elastic collisions only. Rather, because there can be
a transfer
of energy (on the average) between wall 305 of the micro channel and a
plurality
constituent particles 310, it is understood that any one particular specular
collision
between constituent particle 310 and wall 305 can increase or decrease the
kinetic
energy of constituent particle 310 relative to the kinetic energy it possessed
prior to
the collision. For example, if there is a transfer of energy from wall 305 to
constituent
particle 310, then one would expect that the acute angle between constituent
particle
310 and the plane parallel to wall 305 would be larger after the collision
than before
the collision. Likewise, if there is a transfer of energy from constituent
particle 310 to
wall 305, then one would expect that the acute angle between constituent
particle 310
and the plane parallel to wall 305 would be smaller after the collision than
before the
collision. Furthermore, where the temperature of the fluid comprising a
plurality of
constituent particles is different from the temperature of the wall, there can
be a
transfer of internal energy from the fluid to the wall, or from the wall to
the fluid
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(depending upon which is at the higher temperature). Where the collisions
between a
plurality of constituent particles 310 and wall 305 are substantially specular
as used
herein, a transfer of energy from a fluid flowing through micro channel 210 to
wall
305 or from wall 305 to the fluid flowing through micro channel 210 can occur
predominantly through the average change in the speed of constituent particle
310
associated with the change in its velocity component perpendicular to the
plane of
wall 305 during the collision. One should also appreciate that such a change
in the
velocity component of constituent particle 310 during the collision can change
the
overall speed of constituent particle 310 as a result of the collision
process.
[024] In an embodiment consistent with the present disclosure, the surface of
the walls of micro channel 210 can include any suitable material configured
for
specular collisions, such as silicon, tungsten, gold, platinum, and diamond.
Such a
surface may be deposited onto micro channel 210 using any of a variety of MEMs
fabrication techniques, including, but not limited to, sputtering and
evaporative
deposition. Furthermore, consistent with the present disclosure, diamond
smooth films
with grains as small as 100 nm and 20nm Ra roughness can be grown onto channel
walls. In one embodiment, diamond can be preferable as a result of its melting
point
(i.e., approx. 4000 K at one atmosphere) and as a result of its hardness
(i.e., a10 in
Mohs scale for hardness). Consistent with further embodiments of the present
disclosure, the surface of the walls of micro channel 210 can also include
tungsten
carbide, glass and pyrolytic graphite-in part at least because of its high
thermal
conductivity of 1700 W/mK. Micro channel 210 can also include a diamond
nanoparticle film on pyrolytic graphite substrate.
[025] FIG. 4 is a schematic view of micro channel 410 within an exemplary
decelerating element 125 of FIG. 1. Channel 152 is depicted as an opening in
decelerating element 125, and in fluid communication with micro channel 410.
Again,
the scale of micro channel 410 as depicted in FIG. 4 is for illustration
purposes. Micro
channel 410 can be engineered to be small (i.e., with an internal surface area
that may
be as small as approximately 3e-11 mA2 per linear micron to 6e-10 mA2 per
linear
micron in a preferred embodiment, which can correspond, respectively, to a
channel
with an approximate diameter of 9 microns to 180 microns). As depicted in FIG.
4 in
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an exemplary embodiment, micro channel 410 is approximately confined to a
planar
region (i.e., accelerating element 125) and exhibits a spiral such that a
fluid entering
from linear channel 420 enters micro channel 410, describing arcs of
decreasing
radius until the fluid enters entering channel 152. In a preferred embodiment,
the total
length of micro channel 410 from linear channel 420 until reaching channel 152
can
be approximately 10 mm to more than 1 meter. Further still, as discussed
above, in a
preferred embodiment where decelerating element 125 is one of a 100 watt pair
of
accelerating and decelerating elements, the width W can be 100 millimeters.
Furthermore, in a preferred embodiment, the walls of micro channel 410 can be
substantially specular.
[026] In an embodiment consistent with the present disclosure, the surface of
the walls of micro channel 410 can include any suitable material configured
for
specular collisions, such as silicon, tungsten, gold, platinum, and diamond.
Such a
surface may be deposited onto micro channel 410 using any of a variety of MEMs
fabrication techniques, including, but not limited to, sputtering and
evaporative
deposition. Furthermore, consistent with the present disclosure, diamond
smooth films
with grains as small as 100 nm and 20nm Ra roughness can be grown onto channel
walls. In one embodiment, diamond can be preferable as a result of its melting
point
(i.e., approx. 4000 K at one atmosphere) and as a result of its hardness
(i.e., alO in
Mohs scale for hardness). Consistent with further embodiments of the present
disclosure, the surface of the walls of micro channel 410 can also include
tungsten
carbide, glass and pyrolytic graphite-in part at least because of its high
thermal
conductivity of 1700 W/mK. Micro channel 410 can also include a diamond
nanoparticle film on pyrolytic graphite substrate
[027] FIG. 5 depicts connection 510 between linear channel 220 and linear
channel 420 through interface 130.
[028] In a preferred embodiment, where the fluid is air, channel 151 can be
kept at a relatively high pressure, and channel 152 can be kept at a
relatively low
pressure, so as to allow for the flow of fluid through the plurality of
accelerating
elements 115 and decelerating elements 125. In a preferred embodiment, the
channel
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151 can exhibit a pressure of approximately 1 atm or more, and channel 152 can
exhibit a pressure that is approximately 0.528 of the pressure of channel 151.
[029] Turning to FIG. 6, which depicts an expanded view of micro channel
210, fluid that is at the inner portion of micro channel 210 (i.e., proximal
to inflow
opening 601) can be induced to flow through. spirals of increasing radii
through the
use of a pressure differential as discussed above. Where the temperature of
the fluid at
inflow opening 601 is T1, then the constituent particles (such as constituent
particle
310 in FIG. 3) can be represented by a distribution of speeds, the average
speed of
which is proportional to temperature.
[030] Where the throat of inflow opening 601 is small (for example,
anywhere from 0.01 m^2 to 500 m^2 where the fluid is air), then the
constituent
particles of a fluid moving through inflow opening 601 into micro channel 210
can
exhibit a velocity that has its component parallel to direction 650 larger
than its
component perpendicular to direction 650. Consequently, the fluid passing
through
micro channel 210 acquires a flow velocity that is predominantly parallel to
direction
650. The kinetic energy that is associated with the flow of fluid in direction
650 is
drawn from the internal thermal energy of fluid, which was at TI before it
entered
inflow opening 601. Conservation of energy dictates that, because a portion of
the
original thermal energy of fluid at TI has been converted to kinetic energy of
flow for
fluid passing through micro channel 210, the temperature of fluid (in a frame
that is
stationary with the velocity of flow) in micro channel 210 can be lower than
T1, which
we will designate as T2. Where T2 is also less than the temperature of wall
610 (which
we will designate as Tw) of micro channel 210, then the fluid in micro channel
210
can cool the material comprising accelerating element 115.
[031] Micro channel 210, consistent with an embodiment of the present
disclosure is configured to enhance the effect this temperature change has on
the fluid
passing through micro channel 210 in at least three ways. Specifically, where
wall
610 and the constituent particles in the fluid are configured such that
collisions
between wall 610 and the constituent particles are substantially specular,
then such
collisions-which are a means of transferring energy between wall 610 and the
fluid-will have a minimal effect on the overall flow of fluid through micro
channel
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210. In other words, where the collision between the constituent particle and
wall 610
is such that the velocity of the constituent particle is equally likely to be
in any
direction away from wall 610 (i.e., a non-specular collision), then a
plurality of such
collisions will have the effect of slowing down the flow of the fluid, which
will also
likely have the effect of raising the internal temperature of the fluid in
micro channel
210. Micro channel 210, consistent with an embodiment of the present
disclosure, is
configured to enhance the effect of cooling by selectively avoiding the effect
of non-
specular collisions.
[032] In addition, because the outer wall of micro channel 210 is configured
as a generally increasing spiral, the specular scattering of a constituent
particle off of
successive portions of the wall of micro channel 210 (such as portions 610,
615, and
620), can convert a portion of the velocity component which was perpendicular
to the
direction of flow through micro channel 210 (i.e., a radial velocity
component) to a
component parallel to the direction of flow through micro channel 210. Because
the
spiral grows larger along the path of micro channel 210, the constituent
particles can
undergo less and less collisions with the wall (along the path of micro
channel 210) as
the fluid travels towards linear channel 220.
[033] Moreover, because micro channel 210 is engineered to be small (i.e.,
with an internal surface area that may be as small as approximately 3e-11 m^2
per
linear micron to 6e- 10 mA2 per linear micro in a preferred embodiment), then
the ratio
of the surface area presented by the wall of micro channel 210 to a given
volume of
fluid in any region within micro channel 210 is relatively large (i.e., where
the volume
of the fluid enclosed by the above surface is approximately 8e-17 m^3 per
linear
micron to 3e-15 m^3 per linear micron). Because the surface area presented by
the
wall of micro channel 210 to a volume of fluid is a primary means of energy
exchange
between the walls and the fluid 115, this can tend to maximize the overall
energy
exchange interaction between the fluid and micro channel 210.
[034] For example, as shown in FIG. 6, a constituent particle can enter
inflow opening 601 with a component predominantly parallel to direction 650,
and
undergoes a specular collision with local region 610 of the wall of micro
channel 210,
and acquires a velocity component in direction 651. The constituent particle
may now
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undergo a specular collision with local region 615 of the wall of micro
channel 210,
and acquires a velocity component in direction 652. The constituent particle
can
undergo a specular collision with local region 620 of the wall of micro
channel 210,
and acquire a further velocity component along the general direction of micro
channel
210.
[035] Angle R corresponds to the angular offset between normal 625 and
normal 630. Angle a corresponds to the angular offset between normal 630 and
normal 635. In a preferred embodiment, where the separation between the first
wall
portion and the second wall portion is at least N times the largest width of
the micro
channel over that separation (where N can be an integer), the angle offset
between the
first normal and the second normal can be less than N/10 degrees. Likewise,
where the
separation between the second wall portion and the third wall portion is at
least N
times the largest width of the micro channel over that separation, the angle
offset
between the second normal and the third normal can be less than N/10 degrees.
For
example, preferably where the separation between the first wall portion and
the
second wall portion (and the separation between the second wall portion and
the third
wall portion) is at least twenty-five times the largest width of the micro
channel over
that separation, the angle offset between the first normal and the second
normal (and
the second normal and the third normal) is less than 2.5 degrees. Likewise,
preferably
where the separation between the local region 610 and local region 615 is at
least fifty
times the largest width of micro channel 210 over that separation, the angle
offset
between normal 625 and normal 630 can be less than 5 degrees. Similarly, where
the
separation between local region 615 and local region 620 is at least fifty
times the
largest width of micro channel 210 over that separation, the angle offset
between
normal 630 and normal 635 can be less than 5 degrees.
[036] In this manner, accelerating element 115 can be cooled by the passage
of a fluid, where the fluid is configured to exhibit specular collisions with
the walls of
micro channel 210. Moreover, a fluid passing through accelerating element 115
can
be accelerated: i.e., when the fluid arrives at linear channel 220, the
velocity
components of the fluid's constituent particles are predominantly along the
direction
of linear channel 220 leading to connection 510.
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[037] Recapping somewhat, and consistent with the present disclosure, the
translational kinetic energy (TKE) of the constituent particles in a fluid
(i.e.,
molecules in a molecular beam) can be reduced by collisions with a surface.
The
percentage of TKE transferred from the fluid to the surface can be dependent
upon the
velocity of the fluid, the smoothness of the surface, the internal kinetic
energy of the
constituent particles in the fluid and the kinetic energy density of the
surface.
[038] A fluid (as a molecular beam) with a particular root mean square
(RMS) velocity and a constant average angle of incidence can transfer more
energy to
a smooth surface with a lower kinetic energy density than to the same surface
when it
is placed at a higher energy density. If the energy density of the surface is
sufficiently
high with respect to the energy density of an impinging molecular beam no
energy
will be transferred from the beam to the surface.
[039] Surface collisions that result in a net energy transfer to the surface
can
reduce the internal kinetic energy level of constituent particles in the
fluid. When the
internal energy level of a molecule has been reduced sufficiently (such as
through
vibrational energy levels) it can emit one or more photons at a frequency that
is
commensurate with the reduced internal energy level.
[040] The same principle of operation can apply to decelerating element 125,
where micro channel 410 is configured as a spiral that presents successively
smaller
radii to a fluid passing from linear channel 420 to channel 152. In this
manner, a high
velocity fluid arriving from connection 510 to linear channel 420 can undergo
more
and more collisions with the wall (along the path of micro channel 210) as the
fluid
travels towards channel 152.
[041] As with accelerating element 115 and micro channel 210, the walls of
micro channel 410 in decelerating element 125 are configured to cause the
constituent
particles in the fluid passing through micro channel 410 to undergo specular
collisions.
[042] In addition, where the constituent particles of the fluid are molecules
(and, for example, where the fluid is a gas), then certain vibrational states
of the
constituent particles may be populated as a result of the increase in
temperature that is
achieved near the inner opening between micro channel 410 and channel 152.
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[043] Consistent with the present disclosure, a molecular beam in a MEMS
device (such as accelerating element 115 and decelerating element 125) that
can be
used for cooling electronics, refrigeration, air conditioning and other
applications can
exhibit high RMS velocities. A molecular beam composed of room air with an RMS
velocity of 2,000 meters per second has the translational kinetic energy of
still air at
over 4,000 K, a temperature that is well beyond the melting point of most
materials. A
refrigeration system's hot-side heat exchanger preferably would have the
ability to
extract precise quantities of both translational and internal kinetic energy
from the
accelerated molecular beam without damage to a heat exchanger composed of
conventional materials, such as aluminum and thermally conductive plastics
with a
melting point of only 933 K or less.
[044] A gradual reduction in the translational kinetic energy level of a fast
molecular beam with a high energy density relative to that of the surface
allows for
energy transfer to the surface to occur over an extended surface length. This
is a
desirable method of extracting the energy from a molecular beam when a more
concentrated extraction would damage the channel or raise the temperature of a
device beyond practical limits. With this gradual energy extraction approach,
a hot
side heat exchanger in a refrigeration system that is made of aluminum with a
melting
point of 933 K can be used to transfer extracted energy from a high energy
molecular
beam with an RMS velocity of 2,000 m/s or more to the outside environment
without
damaging the channels of the heat exchange device and not overheating any
portion
of the outer surface of the heat exchanger device. With a gradual kinetic
energy
extraction methodology, virtually any conformal channel material including
ceramics
and thermally conductive polymers can be used as channels and thermal
packaging in
hot-side heat exchanger applications.
[045] As described herein, when a molecular beam experiences a series of
surface collisions with an arc of gradually decreasing radius, translational
and internal
kinetic energy is extracted gradually. A variety of MEMS device channel
designs can
permit a molecular beam to experience such a series of collisions with an arc
of
gradually decreasing radius. For example, channels configured as spirals with
an
initially large radii that gradually reduce over length to a smaller radii,
and a spiraling
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molecular beam progressing through an attenuated channel using the centrifugal
force
of the spiral motion to remain in close proximity to the surface at all
diameters of the
channel are two examples of such designs. Any gradual energy extraction design
would serve to facilitate the conversion of the beams kinetic energy to
infrared and
optical wavelengths of light even when the average energy content of the beam,
if
abruptly slowed or stopped could produce higher frequency emissions. For
applications requiring higher frequency emissions, designs that facilitate
more abrupt
energy extraction methods can of course be applied and are within the scope of
this
disclosure.
[046] An equation describing the approximate transfer of energy from the
translational energy of a molecular beam to a collision surface temperature
can be
derived through kinetic theory. In the equation (3kT)/2 = (mv^2)/2, k is
Boltzmann's
Constant, T is temperature in Kelvins, m is mass and v is velocity. Because
energy
increases with the square of the velocity, the quantity of kinetic energy that
can be
transferred to a surface by slowing a faster beam by one meter per second can
be more
than the quantity that can be transferred to the same surface by a slower
molecular
beam with the same reduction in velocity. The local temperature of the
collision
surfaces and thermal path that extends to the outer surfaces can be controlled
with
complementary collision angles with known velocity ranges of a molecular beam.
[047] A heat exchanger consistent with the present disclosure that gradually
absorbs the kinetic energy from a high energy molecular beam can be heated as
kinetic energy from the molecular beam is absorbed by the heat exchanger's
inner
channel surfaces. Provided that there is a sufficiently conductive thermal
path
between the inner channel surfaces and the outer surfaces of the heat
exchanger, the
heat exchanger and molecular beam channel surfaces can be maintained with any
desired delta T (change in temperature) with the ambient surroundings with
conventional means of heat transfer from the heat exchanger to the ambient
environment. Heat exchangers that evenly extract energy from a molecular beam
along a channel surface can very nearly approximate nearly isothermal
conditions.
[048] Energy extracted from an equilibrated molecular beam can be used to
precisely quantize the modes of energy in a channel cavity. Emissions of light
with a
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predictable energy are provided by Plank's radiation formula that is equal to
Planck's
constant times the frequency. Plank's radiation formula can be used to
calculate the
average energy of any desired frequency of light emitted from a MEMS device
channel.
[049] Continuous coherent spontaneous emission can also occur when a
collimated and equilibrated molecular beam transfers highly resolved
quantities of
energy to the surface of a channel. Channel transparency to the emitted
frequency of
light can allow for the light to escape the channel for practical purposes
that include
any laser application and conversion of light energy to electric current as
would occur
by a photodiode array in the flux path of the photonic emissions from the
channels.
The voltage of the current can be related to the bandgap energy of the channel
material. Coherent emissions can permit photodiodes with a narrow bandwidth to
efficiently convert extracted energy from a molecular beam to an electric
current of a
desired voltage.
[050] Coherent and in-phase emissions from several channels can be readily
achieved from a series of parallel channel surfaces on a MEMS device using
ultra-flat
wafer surfaces. Energy density of coherent emissions can be accomplished with
sub-
micron gaps between parallel channels. MEMS devices with optically and UV
transparent channels with excellent optical homogeneity can be fabricated
using a
variety of materials. Silicon can provide suitable transparent optical
homogeneity to
some infrared frequencies, as can germanium and Amtir. Sapphire, yttria, and
yttrium
alumina garnet provide excellent optical transmission of infrared as well.
Optical
glass can be used for UV and optical wavelengths.
[051] Ina preferred embodiment, the architecture or micro channel 210 and
micro channel 410 can reduce pumping power requirements. Due at least in part
to
such architecture, the values associated with the coefficient of performance
("COP")
can be 10 or higher.
[052] In a further embodiment consistent with this disclosure, values of COP
can be 10 or higher by operating at different pressures. For example, in an
exemplary
embodiment, the power required per constituent particle (or molecule) is a
function of
the pressure ratio, and not the pressure. For exemplary systems 100 that
operate at
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higher pressures, but that are configured to exhibit the same pressure ratio,
a pumping
cost per constituent particle will remain the same, but a higher density flow
if
constituent particles (i.e., a higher density molecular beam) can provide
higher heat
transfer rates and could produce a COP of 10 or more.
[053] Materials and components consistent with the present disclosure, such
as the exemplary devices described above, offers solutions to all of the
problems that
have been identified
[054] Other embodiments consistent with the disclosure will be apparent to
those skilled in the art from consideration of the specification and practice
of the
embodiments disclosed herein. It is intended that the specification and
examples be
considered as exemplary only, with a true scope and spirit of the invention
being
indicated by the following claims.
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