U.S. patent application number 10/804232 was filed with the patent office on 2004-12-16 for heat exchanger system for cooling optical fibers.
Invention is credited to Ghani, M. Usman, Giacobbe, Frederick W., Marin, Ovidiu.
Application Number | 20040251006 10/804232 |
Document ID | / |
Family ID | 33135140 |
Filed Date | 2004-12-16 |
United States Patent
Application |
20040251006 |
Kind Code |
A1 |
Marin, Ovidiu ; et
al. |
December 16, 2004 |
Heat exchanger system for cooling optical fibers
Abstract
A heat exchanger system for cooling a fiber includes an outer
tube section, an inner tube section disposed within and separated a
selected distance from the outer tube section to form an annular
gap therebetween, and a plurality of fins extending transversely
from internal peripheral wall portions of the inner tube section
toward a central axis of the inner tube section. The inner tube
section includes an internal passage configured to receive and cool
the fiber as the fiber moves through the heat exchanger, and the
fins facilitate heat transfer between a cooling medium flowing
through the annular gap and a coolant fluid flowing within the
inner tube section during system operation.
Inventors: |
Marin, Ovidiu; (St.Cloud,
FR) ; Giacobbe, Frederick W.; (Naperville, IL)
; Ghani, M. Usman; (Bolingbrook, IL) |
Correspondence
Address: |
LINDA K. RUSSELL
AIR LIQUIDE
SUITE 1800
2700 POST OAK BLVD
HOUSTON
TX
77070
US
|
Family ID: |
33135140 |
Appl. No.: |
10/804232 |
Filed: |
March 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60460121 |
Apr 3, 2003 |
|
|
|
Current U.S.
Class: |
165/157 ;
165/164 |
Current CPC
Class: |
F28F 1/36 20130101; C03B
2205/50 20130101; F28D 7/106 20130101; C03B 37/02718 20130101 |
Class at
Publication: |
165/157 ;
165/164 |
International
Class: |
F28D 007/10; F28D
007/02; D21F 001/00; D21F 011/00 |
Claims
1. A heat exchanger system for cooling a fiber moving continuously
through the heat exchanger, comprising: an outer tube section; an
inner tube section disposed within and separated a selected
distance from the outer tube section to form an annular gap
therebetween, wherein the inner tube section includes an internal
passage configured to receive and cool the fiber as the fiber moves
through the heat exchanger; and a plurality of fins extending
transversely from internal peripheral wall portions of the inner
tube section toward a central axis of the inner tube section,
wherein the fins facilitate heat transfer between a cooling medium
flowing through the annular gap and a coolant fluid flowing within
the inner tube section during system operation.
2. The system of claim 1, wherein the fins are formed by a
spiraling element extending in an axial dimension along an internal
periphery of the inner tube section.
3. The system of claim 1, wherein the fins are hollow to permit
cooling medium to flow from the annular gap into portions of the
fins.
4. The system of claim 1, wherein the internal passage includes a
plurality of active zones that direct the coolant fluid toward the
fiber to facilitate cooling of the fiber within the active zones
and a plurality of passive zones that direct the coolant fluid away
from the fiber to facilitate heat transfer between the cooling
medium and the coolant fluid in the passive zones.
5. The system of claim 4, wherein the fins are spaced from each
other along an axial dimension of the inner tube section and the
active and passive zones are at least partially defined along a
portion of the fins.
6. The system of claim, wherein the fins are hollow and are
configured to permit cooling medium to flow from the annular gap
into portions of the fins.
7. The system of claim 5, wherein the passive zones are at least
partially defined within spaces formed between adjacent fins.
8. The system of claim 7, further comprising: a plurality of
cooling enclosures, each enclosure being disposed within the space
defined between adjacent fins so as to define a sub-chamber between
the enclosure and the adjacent fins, wherein the cooling enclosures
are hollow and configured to receive a cooling medium to facilitate
heat exchange between the coolant fluid and the cooling medium
within at least the passive zones.
9. The system of claim 1, further comprising: a coolant fluid inlet
and a coolant fluid outlet in fluid communication with the internal
passage and disposed at axially spaced locations along the heat
exchanger; and a recycle line connecting the coolant fluid outlet
to the coolant fluid inlet.
10. The system of 9, further comprising: a mechanical device
disposed within the recycle line to establish a pressure
differential within the heat exchanger between the coolant fluid
inlet and the coolant fluid outlet.
11. The system of claim 10, wherein the mechanical device is at
least one of a pump and a fan.
12. The system of claim 9, wherein the coolant fluid inlet is
disposed between first and second ends of the heat exchanger, the
coolant fluid outlet is disposed proximate the first end of the
heat exchanger, and the heat exchanger further comprises a second
coolant fluid outlet in fluid communication with the internal
passage and disposed proximate the second end of the heat
exchanger.
13. A method of cooling a fiber in a heat exchanger system, the
system including a heat exchanger with an outer tube section, an
inner tube section disposed within and separated a selected
distance from the outer tube section to form an annular gap
therebetween, and a plurality of fins extending transversely from
internal peripheral wall portions of the inner tube section toward
a central axis of the inner tube section, the method comprising:
passing a fiber through an internal passage of the inner tube
section between the fiber inlet and the fiber outlet; directing a
cooling medium through the annular gap; and directing a coolant
fluid through the internal passage of the inner tube section and
around the fins to facilitate heat transfer between the cooling
medium and the coolant fluid.
14. The method of claim 13, wherein the fins are formed by a
spiraling element extending in an axial dimension along an internal
periphery of the inner tube section.
15. The method of claim 13, wherein the fins are hollow to permit
cooling medium to flow from the annular gap into portions of the
fins.
16. The method of claim 13, wherein the coolant fluid is at least
one of helium, neon, argon, krypton, xenon, hydrogen, nitrogen, and
carbon dioxide.
17. The method of claim 13, wherein the cooling medium is at least
one of water, a cryogenic fluid, a liquid hydrocarbon and a gaseous
hydrocarbon.
18. The method of claim 13, wherein the coolant fluid is directed
through the internal passage in an undulating manner between active
zones and passive zones, the coolant fluid being directed toward
the fiber within the active zones to facilitate cooling of the
fiber and the coolant fluid being directed away from the fiber in
the passive zones to facilitate heat transfer between the cooling
medium and the coolant fluid within the passive zones.
19. The method of claim 18, wherein the coolant fluid is forced
through the internal passage in the undulating manner between the
active zones and the passive zones by a mechanical device.
20. The method of claim 18, wherein the fins are spaced from each
other along an axial dimension of the heat exchanger, and the
active and passive zones are at least partially defined along a
portion of the fins.
21. The method of claim 20, wherein the fins are hollow, and the
method further comprises: flowing the cooling medium into the fins
to facilitate heat exchange between the cooling medium and the
coolant fluid within at least the passive zones.
22. The method of claim 20, wherein the system further includes a
plurality of hollow cooling enclosures, each enclosure being
disposed within the space defined between adjacent fins so as to
define a sub-chamber between the enclosure and the adjacent fins,
wherein the sub-chambers at least partially define the passive
zones to direct coolant fluid away from the fiber, and the method
further comprises: flowing the cooling medium into the cooling
enclosures.
23. The method of claim 13, further comprising: recycling the
coolant fluid between a coolant fluid inlet and a coolant fluid
outlet in fluid communication with the internal passage and
disposed at axially spaced locations along the heat exchanger.
24. The method of claim 23, wherein the system further includes a
mechanical device disposed within the recycle line, and the coolant
fluid is recycled by establishing a pressure differential within
the heat exchanger between the coolant fluid inlet and the coolant
fluid outlet.
25. The method of claim 24, wherein the mechanical device is at
least one of a pump and a fan.
26. The method of claim 23, wherein the coolant fluid inlet is
disposed between first and second ends of the heat exchanger, the
coolant fluid outlet is disposed proximate the first end of the
heat exchanger, the heat exchanger further includes a second
coolant fluid outlet in fluid communication with the internal
passage and disposed proximate the second end of the heat
exchanger, and the coolant fluid is further recycled between the
coolant fluid inlet and the second coolant fluid outlet.
27. The method of claim 13, wherein the fiber is an optical
fiber.
28. A heat exchanger system for cooling a fiber moving continuously
through the heat exchanger, comprising: an outer tube section; an
inner tube section disposed within and separated a selected
distance from the outer tube section to form an annular gap
therebetween, wherein the inner tube section includes an internal
passage configured to receive and cool the fiber as the fiber moves
through the heat exchanger; and a means for facilitating heat
transfer between a cooling medium flowing through the annular gap
and a coolant fluid flowing within the inner tube section during
system operation, wherein the means for facilitating heat transfer
extends transversely from internal peripheral wall portions of the
inner tube section toward a central axis of the inner tube section.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 60/460,121, entitled "Optical Fiber
Heat Exchanger", and filed Apr. 3, 2003. The disclosures of this
provisional patent application is incorporated herein by reference
in its entirety.
BACKGROUND OF INVENTION
[0002] 1. Field of Invention
[0003] The present invention pertains to heat exchangers employing
a coolant gas to cool fibers, in particular optical fibers, moving
through the exchangers.
[0004] 2. Related Art
[0005] Optical fibers are typically formed by a process in which
hot fibers are drawn from the end of a massive cylindrical silica
or glass perform that has been heated up to its softening point in
a drawing furnace. This drawing process is followed by cooling the
fibers within a coolant chamber or heat exchanger utilizing a
coolant fluid that flows through the heat exchanger in a co-current
or countercurrent direction with respect to the velocity vector of
the fiber traveling through the exchanger. The drawn fibers must be
cooled to a sufficient temperature within the heat exchanger prior
to cladding the fiber with a heat sensitive protective coating.
[0006] Drawing speeds for optical fibers are presently on the order
of about 20 meters per second and increasing. As the fiber drawing
speeds increase, it becomes increasingly important to rapidly and
effectively cool the hot drawn optical fibers while minimizing the
height or length of the heat exchanger required to cool the fibers.
Thus, it is desirable to provide a heat exchanger system that
effectively controls the cooling rate of fibers flowing through the
system.
SUMMARY OF THE INVENTION
[0007] Accordingly, it is an object of the present invention to
provide a heat exchanger system for a fiber that effectively cools
the fiber at a selected rate.
[0008] It is another object of the present invention to provide a
heat exchanger system that effectively controls the cooling rate of
the fiber by controlling the temperature of the coolant fluid used
to cool the fiber during system operation.
[0009] The aforesaid objects are achieved individually and/or in
combination, and it is not intended that the present invention be
construed as requiring two or more of the objects to be combined
unless expressly required by the claims attached hereto.
[0010] In accordance with the present invention, a heat exchanger
system for cooling a fiber includes an outer tube section, an inner
tube section disposed within and separated a selected distance from
the outer tube section to form an annular gap therebetween, and a
plurality of fins extending transversely from internal peripheral
wall portions of the inner tube section toward a central axis of
the inner tube section. The inner tube section includes an internal
passage configured to receive and cool the fiber as the fiber moves
through the heat exchanger, and the fins facilitate heat transfer
between a cooling medium flowing through the annular gap and a
coolant fluid flowing within the inner tube section during system
operation. The fins can be formed in any suitable configuration and
with any one or more selected geometries. Optionally, the fins may
include hollow portions to facilitate the flow of cooling medium
through portions of the fins.
[0011] In one embodiment of the invention, the internal passage
includes a plurality of active zones that direct the coolant fluid
toward the fiber to facilitate cooling of the fiber within the
active zones and a plurality of passive zones that direct the
coolant fluid away from the fiber to facilitate heat transfer
between the cooling medium and the coolant fluid in the passive
zones. In this embodiment, the heat exchanger includes a plurality
of fins extending transversely from at least one internal wall and
toward an axial center of the heat exchanger, where fins are spaced
from each other along an axial dimension of the heat exchanger and
the active and passive zones are at least partially defined along a
portion of the fins. Optionally, cooling enclosures can be disposed
within spaces defined between adjacent fins so as to define a
series of sub-chambers between the enclosures and their adjacent
fins. The fins and cooling enclosures are hollow and are further
configured to receive a cooling medium to facilitate heat transfer
between the cooling medium and the coolant fluid within at least
the passive zones during travel of the coolant fluid within the
heat exchanger.
[0012] In another embodiment, the fins are formed by a spiraling
element extending in an axial dimension along an internal periphery
of the inner tube section.
[0013] The above and still further objects, features and advantages
of the present invention will become apparent upon consideration of
the following detailed description of specific embodiments thereof,
particularly when taken in conjunction with the accompanying
drawings wherein like reference numerals in the figures are
utilized to designate like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic cross-sectional view of a desired flow
path of coolant fluid through a heat exchanger in accordance with
an embodiment of the present invention.
[0015] FIG. 2 is a schematic view in partial section of one
embodiment of a heat exchanger system in accordance with the
present invention.
[0016] FIG. 3 is a cross-sectional view in perspective of the heat
exchanger of the system of FIG. 1.
[0017] FIG. 4 is a further sectional view in perspective of the
heat exchanger of FIG. 3.
[0018] FIG. 5 is a cross-sectional view of another embodiment of a
heat exchanger for use in a system in accordance with the present
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0019] The heat exchanger system of the present invention utilizes
a heat exchanger configured to receive a continuously moving fiber
(e.g., an optical fiber formed from silica or glass) at a fiber
inlet, one or more inlets and outlets to receive coolant fluid that
contacts and cools the fiber within the heat exchanger and,
optionally, one or more mechanical devices (e.g., pumps, fans,
etc.) to recycle or circulate the coolant fluid through the heat
exchanger. In addition, the coolant system may also include one or
more controllers, flow meters, valves, etc. within the recycle
lines to selectively control the flow rate of recycled coolant
fluid to the heat exchanger. Further, the heat exchanger of the
coolant system may include gas seals disposed at one or more
suitable locations to minimize or prevent the escape of coolant
fluid from the heat exchanger during system operation. Examples of
suitable sealing arrangements that may be employed in the heat
exchanger of the present invention are described in co-pending U.S.
Pat. application Ser. No. 10/765,468, the disclosure of which is
incorporated herein by reference in its entirety.
[0020] Coolant fluid is delivered from a coolant supply source into
the heat exchanger at a selected flow rate. The coolant fluid may
be any one or combination of suitable cooling gases and/or cooling
liquids. Exemplary cooling gases suitable for use include, without
limitation, helium, neon, argon, krypton, xenon, hydrogen,
nitrogen, and carbon dioxide. Helium is a preferred coolant fluid
for cooling optical fibers. However, certain combinations of
coolant gases, such as a combination of substantially pure helium
and substantially pure hydrogen, or a combination of one or more
gases with one or more liquids or a combination of two or more
liquids, may be utilized in certain situations. Selected
combinations of coolant fluids are useful in that they can provide
a certain "fine tuning" or more precise control of the cooling rate
of the fiber in the heat exchanger due to the modification in the
overall heat transfer coefficient that occurs by combination of
different gas mixtures and/or gas purity levels. Optionally, a
coolant gas or a combination of coolant gas mixtures can include
one or more gas dopants that are capable of modifying the
structural and/or chemical properties of the surface of the fiber
in a desirable and beneficial manner when the coolant gas contacts
the fiber within the exchanger. Exemplary dopants include, without
limitation, silanes, phosphines, fluorine, chlorine, gaseous
organometallic compounds, and combinations thereof.
[0021] The heat exchanger system of the present invention provides
effective cooling of fibers at a desired cooling rate during system
operation and facilitates a reduction in the size of the heat
exchanger through which the fiber travels while increasing the
cooling rate within the heat exchanger. This is accomplished by
providing an inner tube section within an outer tube section, where
an annular gap separates the two sections and a cooling fluid
medium is provided within the annular gap. Cooling fins extend
within an internal passage of the inner tube section to facilitate
control of the cooling rate of the fiber traveling through the
internal passage as it is being cooled by a coolant fluid also
traveling through the internal passage system operation. The
arrangement and configuration of the cooling fins can be selected
to control the flow path of the coolant fluid through the internal
passage, as described below, so as to ensure the coolant fluid is
within a selected temperature range and the fiber is cooled at a
desired rate during system operation. The term "cooling fins" or
"fins", as used herein, refers to a vane, rib or other suitable
extension member that extends transversely from internal wall
portions of the inner tube section and facilitates heat transfer
along the extension member. Preferably, the cooling fins extend a
selected distance toward the central axis of the inner tube section
to facilitate heat transfer from the outer surface portions of the
inner tube section a sufficient distance within the inner tube
section.
[0022] In one embodiment of the present invention, the coolant
fluid flowing through the internal passage of the heat exchanger is
controlled such that the coolant fluid travels between active
regions or zones, where the coolant fluid is directed toward and/or
engages and cools the fiber, to passive regions or zones, where the
coolant fluid is directed away from the fiber and is cooled by the
internal fin and/or other surfaces of the inner tube section of the
heat exchanger. An exemplary flowpath for the coolant fluid through
the heat exchanger is illustrated in the schematic of FIG. 1. In
particular, FIG. 1 generally depicts a hot optical fiber 4
traveling in a substantially linear manner through a heat exchanger
2, while coolant fluid 6 travels in a winding or undulating path
through the exchanger between passive zones 8, where the coolant
fluid 6 is directed away from the fiber 4 and toward one or more
internal cooling walls 12 of the heat exchanger to effect heat
transfer between the internal cooling walls and the coolant fluid,
and active zones 10, where the coolant fluid 6 is directed toward
the fiber 4 to effect cooling of the fiber. This undulating flow
path can be achieved by natural convection and/or forced flow
(e.g., via one or more mechanical devices such as pumps, fans,
etc.) as the coolant fluid travels the axial dimension of the inner
tube section.
[0023] The undulating flow path for coolant fluid within the heat
exchanger is achieved, at least in part, by providing cooling fins
that extend transversely from the internal wall surfaces of the
heat exchanger toward the central axis of the exchanger so as to
define sub-chambers between the fins where heat transfer between
the cooling medium and the coolant fluid can occur. An exemplary
heat exchanger using cooling fins to achieve active and passive
zones and establish the flow of coolant fluid through the heat
exchanger in an undulating manner as described above is depicted in
FIGS. 2-4. Heat exchanger 20 is formed of any one or more suitable
metal materials (e.g., copper, aluminum, stainless steel, etc.) and
includes a generally cylindrical outer tube section 22 and a
generally cylindrical and hollow inner tube section 24 disposed
within and separated from the outer tube section 22 so as to form a
sealed annular gap 23 between the two sections. It is noted,
however, that the outer and inner tube sections may include any
other suitable geometric configurations (e.g., rectangular,
multi-faceted, etc.). A fiber inlet 40 and outlet 42 are disposed
at opposing longitudinal ends of the exchanger 20 and are
configured to receive and permit a moving fiber 44 to travel
through the heat exchanger for processing as described below.
[0024] Cooling fins are formed and extend along and inward toward
the central axis of the inner tube section to provide a winding or
undulating flow path for coolant fluid flowing within and along the
axial dimension of the inner tube section as generally described
above and depicted in FIG. 1. Preferably, the fins are formed of a
suitable material (e.g., copper or aluminum) that facilitates
sufficient heat transfer between cooling medium flowing within the
annular gap between the internal and outer tube sections and
coolant fluid flowing within the inner tube section during system
operation. The fins may be formed in any suitable manner along the
inner tube section of the heat exchanger in order to achieve this
desired flow for coolant fluid. For example, the fins may be
constructed of separate elements extending transversely along and
toward the central axis of the inner tube section. Alternatively,
each pair of fins may be constructed of a single element, with a
cut-out section to form the gap between pairs of fin elements so as
to form the fiber channel. Further still, the fins may be
constructed as a single "forged fin" element that spirals axially
along the peripheral surfaces of the inner tube section (i.e., in a
helical manner, similar to the configuration depicted in the
embodiment of FIG. 5), with the fiber channel being defined between
the terminal edges of the spiral element. The fins may also be
arranged in a double helix configuration around the inner tube
section periphery. The fins can be parallel or non-parallel with
each other depending upon the desired flow path characteristic for
coolant fluid in a particular application.
[0025] Referring to the embodiment of FIGS. 2-4, a series of fins
26 extend transversely within the inner tube section toward the
central axis of the heat exchanger 20. The fins 26 are separated a
selected distance from each other along the axial dimension of the
exchanger 20 and are arranged in pairs. Each fin in a pair is
aligned with and extends toward the other fin in the pair so as to
form a gap within the inner tube section and between each pair of
fins. A generally linear channel 25 is at least partially defined
by the combination of gaps disposed between pairs of fins, and this
channel 25 extends axially between and communicates with the fiber
inlet 40 and the fiber outlet 42 to allow the optical fiber to
travel through the exchanger 20 during system operation. The active
zones within the heat exchanger 20 are defined at least in part at
the gaps between fins 26 which together form the fiber channel 25.
The fins 26 are at least partially hollow and are sealed at the
ends extending within the inner tube section 24 but are open to the
annular gap 23 defined between the outer tube section 22 and the
inner tube section 24 to permit cooling medium flowing within the
annular gap to enter the fins 26 during system operation as
described below. Alternatively, and depending upon a particular
application, the fins may be solid and still provide effective
cooling of both the coolant fluid and the fiber traveling through
the heat exchanger during system operation.
[0026] Optionally, cooling enclosures are placed between adjacent
fins to further define generally curved or U-shaped sub-chambers
that enhance the undulating flow path for coolant fluid within the
heat exchanger. The cooling enclosures can be formed in any
suitable manner within the inner tube section in order to define
such curved sub-chambers. For example, the cooling enclosures may
be formed as a single, spiraling or helical element as described
above for the fins, where the cooling enclosure element winds or is
"threaded" between a corresponding helical fin element.
Alternatively, the cooling enclosures may be formed as a plurality
of separate elements. The separate elements may include pairs of
aligned elements disposed along opposing longitudinal cross
sections of the inner tube section and/or single elements extending
across both longitudinal cross sectional portions of the inner tube
section and with a cut-out portion that defines the fiber
channel.
[0027] Referring to the embodiment of FIGS. 2-4, cooling enclosures
28 extend transversely within the inner tube section 24 in a
direction (as viewed from the cross-sectional depiction in FIG. 2)
that is generally perpendicular to the direction in which the fins
26 extend within the inner tube section. Each cooling enclosure 28
is hollow and extends between opposing peripheral wall portions of
the inner tube section 24 so as to be in fluid communication with
the annular gap 23 while otherwise being sealed along all other
side wall surfaces.
[0028] Each cooling enclosure 28 is further disposed between two
adjacent fins 26 on each longitudinal cross-sectional portion of
the inner tube section 24 of the heat exchanger 20. A cut-out
section in each cooling enclosure 28 forms a gap which further
defines a portion of the fiber channel 25, and each enclosure 28 is
also spaced a suitable distance from each adjacent fin 26 to form a
curved space or sub-chamber 30 between the internal walls forming
the enclosure and adjacent fins. This sub-chamber 30 at least
partially defines a passive zone through which the coolant fluid
flows as described below.
[0029] A sufficient amount of cooling medium 32 is provided within
the annular gap 23 to fill the fins 26 and cooling enclosures 28 in
order to effectively maintain the coolant fluid within a selected
temperature range during system operation. The cooling medium can
be water, liquid or gaseous cryogenic fluids (e.g., nitrogen,
helium, argon, hydrogen, oxygen, etc.), or any other single or
combination of suitable fluid mediums capable of cooling the
coolant fluid at a selected rate and to a selected temperature when
the coolant fluid travels through the passive zones of the heat
exchanger. Alternatively, the fluid medium may be heated to a
selected temperature to prevent rapid cooling of the fiber in the
heat exchanger. Basically, any one or more combinations of fluids
(e.g., heated or cooled water, liquid or gaseous cryogenics, liquid
or gaseous hydrocarbons or hydrocarbon mixtures, heated oils, etc.)
may be provided at any desired temperatures within the outer tube
section to achieve precise control of the temperature of the
coolant fluid and thus the cooling rate of the fiber traveling
through the heat exchanger.
[0030] An inlet conduit 34 and an outlet conduit 36 extend
transversely from the outer tube section 22 at axially spaced
locations from each other and near the ends of the outer tube
section to facilitate the flow of cooling medium into and through
the annular gap 23 and cooling enclosures 28 when the conduits are
connected to a fluid medium supply source (not shown). The cooling
medium may be continuously flowing through the annular gap 23 and
cooling enclosures 28 or, alternatively, initially filled and then
maintained within these sections during system operation. The
cooling medium may also be purified (e.g., utilizing any suitable
filtration and/or separation devices) and recycled for reuse during
system operation and/or during periods in which the system is not
being used. Further, the cooling medium can be directed through a
secondary heat exchanger prior to re-entry into the heat exchanger
20 so as to ensure the cooling medium is at an appropriate
temperature within the heat exchanger 20.
[0031] The heat exchanger also includes at least one coolant fluid
inlet and at least one coolant fluid outlet extending transversely
from the outer tube section at axially separated locations to
permit the flow of coolant fluid into and out of the heat
exchanger. In the embodiment depicted in FIG. 2, an inlet conduit
46 is provided at a generally central location along the axial
dimension of the heat exchanger to facilitate delivery of coolant
fluid centrally into passage 25 to engage with the fiber 44. A
first outlet conduit 48 is provided near the top portion of the
exchanger 20 to receive coolant fluid flowing up from the inlet
conduit 46 and through passage 25, and a second outlet conduit 50
is provided at the bottom portion of the exchanger 20 to receive
coolant fluid flowing down from the inlet conduit 46 and through
passage 25. Thus, coolant fluid in the heat exchanger of FIG. 2
flows from a central location within the heat exchanger outward
toward the top and bottom of the exchanger. However, it is noted
that the coolant fluid flow in the heat exchanger may be configured
in any other suitable manner depending upon a particular
application (e.g., top to bottom, bottom to top, etc.).
[0032] The coolant fluid emerging from the outlet conduits 48 and
50 can be discarded or, alternatively, purified and/or recycled. In
the embodiment of FIG. 2, the first and second outlet conduits 48
and 50 are connected with the inlet conduit 46 via suitable recycle
lines (e.g., including piping, associated fittings and valves,
etc.) to permit recycling of the coolant fluid during system
operation. The flow of coolant fluid through the heat exchanger can
be achieved by natural and/or forced convection. As depicted in
FIG. 2, recycle pumps 52 and 54 are disposed in the recycle line to
facilitate recycling of the coolant fluid. In particular, the pumps
52 and 54 establish a pressure differential between the inlet
conduit 46 and each outlet conduit 48 and 50 to facilitate the flow
of fluid in the two general directions within the heat exchanger 20
as illustrated by the arrows in FIG. 2. Alternatively, the recycle
of coolant fluid may be achieved by a fan driven mechanism and/or
any other suitable mechanically driven process.
[0033] Optionally, any suitable number of valves, flow meters,
fluid analyzers, purification devices and/or branched or other
fluid supply lines may be integrated into the recycle lines as
needed to facilitate the delivery of fresh coolant medium and/or
coolant medium at any desired composition and flow rate to the
inlet conduit 46.
[0034] During system operation, a hot drawn optical fiber 44 is
directed to the inlet 40 of the heat exchanger 20 and into fiber
passage 25, where the fiber continuously moves through the passage
25 to the fiber outlet 42. Coolant fluid is directed into the heat
exchanger 20 via the inlet conduit 46, where it initially engages
the optical fiber. Cooling medium 32 is continuously flowed into
and maintained at a suitable temperature within the fins 28 and
cooling enclosures 28, via inlet and outlet conduits 34 and 36, so
as to selectively control the temperature of the coolant fluid as
it travels from the active zones to the passive zones within the
exchanger as described below.
[0035] The coolant fluid is drawn through the heat exchanger by
natural convection and/or forced flow (e.g., via pumps 52 and 54).
In particular, the coolant fluid engages and cools the fiber 44 in
the active zones, which are at least partially defined at the gaps
between pairs of fins 26. As the coolant fluid moves around the
ends of the fins 26, the coolant fluid is then drawn into the
passive zones, which are at least partially defined by the curved
sub-chambers 30 located between the walls of adjacent fins 26 and
cooling enclosures 28 disposed between the adjacent fins. The
coolant fluid is drawn from the active zones into the passive zones
by natural convection and/or forced flow. Thus, the coolant fluid
alternates between active zones (where it cools the fiber) and
passive zones (where the heat transfer occurs between the cooling
medium and the coolant fluid), resulting in an undulating motion of
the coolant fluid in directions toward and away from the fiber (as
generally indicated by the arrows shown in FIG. 2) as it travels
axially within the heat exchanger toward outlet conduits 48 and 50.
Pumps 52 and 54 are operated as necessary to create a pressure
differential between the inlet conduit 46 and the outlet conduits
48 and 50 in order to drive the coolant fluid in the undulating
motion through the heat exchanger at one or more desired flow
rates.
[0036] The heat exchange between the cooling medium and the coolant
fluid and the cooling rate of the fiber within the heat exchanger
can be adjusted by controlling the thickness dimensions of the
cooling enclosures 28 (as indicated by the dimension "a" in FIG. 2)
and the thickness dimensions of the fins 26 (as indicated by the
dimension "b" in FIG. 2). Controlling the ratio of a/b affects the
dimensions of both the active and passive zones, which in turn
controls the cooling rate for the fiber moving through the
exchanger. For example, the ratio of thickness of cooling
enclosures to fins may varied from values in which a/b approaches
zero to where a/b approaches 100. Preferred ranges of a/b ratios
are from about 2 to about 5.
[0037] Other heat exchanger embodiments are also encompassed by the
present invention with different fin arrangements that provide
effective cooling of both the coolant fluid and the fiber traveling
through the heat exchanger. For example, heat exchangers may
include fin arrangements without the cooling enclosures as
described above and depicted in FIGS. 2-4.
[0038] An example of another heat exchanger embodiment is
illustrated in FIG. 5. Heat exchanger 100 includes a generally
cylindrical outer tube section 122 and a generally cylindrical and
hollow inner tube section 124 disposed within and separated from
the outer tube section 122 so as to form a sealed annular gap 123
between the two sections. It is noted, however, that the outer and
inner tube sections may include any other suitable geometric
configurations (e.g., rectangular, multi-faceted, etc.). The
internal and outer tube sections may be constructed of any suitable
materials (e.g., stainless, steel, copper and/or aluminum). A fiber
inlet 140 and outlet 142 are disposed at opposing longitudinal ends
of the exchanger 100 and are configured to receive and permit a
moving fiber (not shown) to travel through the heat exchanger
during system operation.
[0039] The outer tube section 122 includes an inlet conduit 134 and
an outlet conduit 136 extending transversely from the outer tube
section and respectively disposed near the lower and upper ends of
the heat exchanger 100 to facilitate the flow of cooling medium
through the annular gap 123. Similarly, the inner tube section 124
includes an inlet conduit 146 and an outlet conduit 148 extending
transversely from the internal and outer tube sections and
respectively disposed near the lower and upper ends of the heat
exchanger to facilitate the flow of coolant fluid through the inner
tube section in a counter-current manner with respect to the
movement of the fiber through the inner tube section during system
operation. The coolant fluid and cooling medium may be of any
suitable one or combination of fluids as described above. For
example, the coolant fluid can be helium, while the cooling medium
can be water.
[0040] Cooling fins are formed and extend along and inward toward
the central axis of the inner tube section. The cooling fins can be
formed along the internal wall surfaces of the inner tube section
in any suitable manner and can include any selected geometric
configurations. For example, the cooling fins may be formed as
separate elements extending at any number of selected locations
both axially and radially along the inner wall perimeter of the
inner tube section. Alternatively, the cooling fins may be formed
as axially spaced elements, where each element includes a cut-out
portion that defines a generally linear channel for the fiber.
Further still, the cooling fins may be formed from one or more
single spiraling or helical elements disposed on the inner wall
perimeter of the inner tube section.
[0041] Referring to the embodiment of FIG. 5, the cooling fins 126
of the heat exchanger 100 are formed of a single helical or
spiraling formed fin element that extends along the inner periphery
of the inner tube section from its lower end to its upper end. The
fins are solid (i.e., not hollow) and are constructed of a suitable
material (e.g., copper or aluminum) to facilitate effective heat
transfer between cooling medium disposed within the annular gap 123
and coolant fluid flowing within the inner tube section 124 during
system operation. Alternatively, the fins can be hollow to permit
cooling medium to extend within the fins in a similar manner as
described above for the fins of FIGS. 2-4. The fins extend
transversely a selected distance from and toward a central axis of
the inner tube section 124 so as to define a generally linear fiber
channel within the inner tube section.
[0042] Each 180-360.degree. rotational segment of the fin spiral
along the inner tube section wall can be of the same or varying
thickness, thus facilitating similar or different rates of heat
transfer between the cooling medium and the coolant fluid along the
axial dimension of the heat exchanger. Further, the distance
between each 180-360.degree. rotational segment of the fin spiral
(i.e., the pitch of the spiral at different locations) can be the
same or varied so as to provide similar or varied rates of heat
transfer between the cooling medium and the coolant fluid along the
axial dimension of the heat exchanger.
[0043] The coolant fluid inlet and outlet conduits 146 and 148 are
connected to each other in a similar manner as described above and
depicted in FIG. 2 to facilitate recycling and/or purification as
well as selective forced flow (e.g., via pumps and/or fans disposed
in-line with the recycling line) of the coolant fluid during system
operation. Similarly, the inlet and outlet conduits 134 and 136 for
the cooling medium may similarly be connected to each other to
facilitate recycling and/or purification during system operation as
described above.
[0044] During system operation, an optical fiber is directed
between inlet 140 and outlet 142 and through the fiber channel of
the inner tube section 124, while coolant fluid is directed through
the inner tube section 124 (via inlet and outlet conduits 146 and
148) and cooling medium is directed through the annular gap 123
(via inlet and outlet conduits 134 and 136). The fins 126 provide
effective mixing and enhanced heat transfer between the cooling
medium and the coolant fluid to ensure the coolant fluid remains
within a selected temperature range during system operation.
[0045] The heat exchanger embodiments of the present invention
provide high cooling wall surface areas formed by the combination
of fins and/or cooling enclosures disposed within the inner tube
section. This in turn provides a substantial increase in contact
area for heat transfer between the coolant gas flowing within the
inner tube section and the surrounding cooling medium disposed
within the outer tube section of the heat exchanger while
minimizing the axial dimensions of the heat exchanger. Further, the
amount of coolant fluid required to cool the fiber at a selected
rate within the heat exchanger is decreased in comparison to
typical optical fiber heat exchangers due to the enhanced ability
the system provides in controlling the temperature of the coolant
fluid.
[0046] In addition, the arrangement of fins and/or cooling
enclosures within the heat exchanger embodiments described above
facilitates the use of a "clamshell" heat exchanger design (i.e., a
heat exchanger that separates along its axial dimension into two or
more hinged sections), which in turn facilitates easy opening and
closing of the exchanger during periods in which the system is not
being used.
[0047] Having described novel heat exchanger systems for cooling
optical fibers, it is believed that other modifications, variations
and changes will be suggested to those skilled in the art in view
of the teachings set forth herein. It is therefore to be understood
that all such variations, modifications and changes are believed to
fall within the scope of the present invention as defined by the
appended claims.
* * * * *