U.S. patent application number 10/443186 was filed with the patent office on 2004-11-25 for magnetohydrodynamic pumps for non-conductive fluids.
This patent application is currently assigned to NANOCOOLERS INC.. Invention is credited to Ghoshal, Uttam, Kolle, Key, Miner, Andrew Carl.
Application Number | 20040234392 10/443186 |
Document ID | / |
Family ID | 33450355 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040234392 |
Kind Code |
A1 |
Ghoshal, Uttam ; et
al. |
November 25, 2004 |
Magnetohydrodynamic pumps for non-conductive fluids
Abstract
The present invention provides an improved fluid pump that
combines a liquid metal MHD pump with a plurality of fluid flow
valves. The pump comprises a suction and pumping assembly, the
suction and pumping assembly in turn comprising a first vertical
chamber and a second vertical chamber connected using an
intermediate horizontal chamber, a liquid metal partially filling
the suction and pumping assembly, and an AC-powered reciprocating
MHD pump. The AC-powered reciprocating MHD pump drives the liquid
metal in an oscillatory manner, causing the suction and pumping of
a working fluid. The pump further comprises at least one inlet
conduit connected to the suction and pumping assembly for enabling
the suction of a working fluid, at least one outlet conduit
connected to the suction and pumping assembly for enabling the
pumping of the working fluid, and a plurality of valves in the
inlet and outlet conduits to regulate the flow of the working
fluid.
Inventors: |
Ghoshal, Uttam; (Austin,
TX) ; Miner, Andrew Carl; (Austin, TX) ;
Kolle, Key; (Luling, TX) |
Correspondence
Address: |
ZAGORIN O'BRIEN & GRAHAM, L.L.P.
7600B N. CAPITAL OF TEXAS HWY.
SUITE 350
AUSTIN
TX
78731
US
|
Assignee: |
NANOCOOLERS INC.
|
Family ID: |
33450355 |
Appl. No.: |
10/443186 |
Filed: |
May 22, 2003 |
Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04F 1/06 20130101; F04B
17/044 20130101; F04B 53/141 20130101; F04B 19/006 20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04B 035/04 |
Claims
What is claimed is:
1. An apparatus for pumping a working fluid, the apparatus
comprising: a. a suction and pumping assembly comprising: i. a
first vertical chamber and a second vertical chamber connected
using an intermediate horizontal chamber, ii. liquid metal
partially filling the vertical chambers of the suction and pumping
assembly, and iii. an AC-powered reciprocating MHD pump for driving
the liquid metal in the chambers of the suction and pumping
assembly in an oscillatory manner; b. at least one inlet conduit
connected to the suction and pumping assembly, the inlet conduit
allowing the working fluid to be sucked into the suction and
pumping assembly, the working fluid being sucked in due to the
oscillatory motion of the liquid metal; c. at least one outlet
conduit connected to the suction and pumping assembly, the outlet
conduit allowing the working fluid to be pumped out of the suction
and pumping assembly, the working fluid being pumped out due to the
oscillatory motion of the liquid metal; and d. a plurality of
valves in the inlet and outlet conduits for controlling the inlet
and outlet flow of the working fluid.
2. The apparatus as recited in claim 1 wherein the suction and
pumping assembly is U-shaped.
3. The apparatus as recited in claim 1 wherein the working fluid is
a non-conductive fluid.
4. The apparatus as recited in claim 3 wherein each of the
plurality of valves is a one-way valve.
5. The apparatus as recited in claim 3 wherein each of the
plurality of valves is a Tesla valve.
6. The apparatus as recited in claim 1 wherein the apparatus
comprises only one inlet conduit and only one outlet conduit.
7. The apparatus as recited in claim 6 wherein the inlet conduit
and the outlet conduit have one valve each.
8. The apparatus as recited in claim 7 wherein the inlet conduit is
connected to the first vertical chamber of the suction and pumping
assembly and the outlet conduit is connected to the second vertical
chamber of the suction and pumping assembly.
9. The apparatus as recited in claim 8 wherein the liquid metal
partially fills both the first vertical chamber of the suction and
pumping assembly and the second vertical chamber of the suction and
pumping assembly.
10. The apparatus as recited in claim 9 wherein the pumping is
achieved by: a. the AC-powered reciprocating MHD pump driving down
the liquid metal in the first vertical chamber of the suction and
pumping assembly during one half of the AC cycle, the driving down
of the liquid metal causing the sucking in of the working fluid
into the first vertical chamber of the suction and pumping assembly
through the inlet conduit and the pumping out of the working fluid
through an outlet conduit of the suction and pumping assembly; b.
the AC-powered reciprocating MHD pump driving up the liquid metal
in the first vertical chamber of the suction and pumping assembly
during the other half of the AC cycle, the driving up of the liquid
metal causing the working fluid to be transferred from the first
vertical chamber to the second vertical chamber of the suction and
pumping assembly through an intermediate conduit, the intermediate
conduit connecting the first vertical chamber and the second
vertical chamber.
11. The apparatus as recited in claim 10 wherein the intermediate
conduit contains a valve to control the transfer of the working
fluid between the first vertical chamber and the second vertical
chamber.
12. The apparatus as recited in claim 7 wherein both the inlet
conduit and the outlet conduit are connected to the first vertical
chamber of the suction and pumping assembly.
13. The apparatus as recited in claim 12 wherein the liquid metal
partially fills the first vertical chamber of the suction and
pumping assembly and completely fills the second vertical chamber
of the suction and pumping assembly.
14. The apparatus as recited in claim 13 wherein the second
vertical chamber of the suction and pumping assembly is connected
to a reservoir of inert fluid.
15. The apparatus as recited in claim 14 wherein the pumping is
achieved by: a. the AC-powered reciprocating MHD pump driving down
the liquid metal in the first vertical chamber of the suction and
pumping assembly during one half of the AC cycle, the driving down
of the liquid metal causing the sucking in of the working fluid
into the first vertical chamber of the suction and pumping assembly
through the inlet conduit; b. the AC-powered reciprocating MHD pump
driving up the liquid metal in the first vertical chamber of the
suction and pumping assembly during the other half of the AC cycle,
the driving up of the liquid metal causing the pumping out of the
working fluid through the outlet conduit of the second vertical
chamber of the suction and pumping assembly.
16. The apparatus as recited in claim 1 wherein the apparatus
comprises two inlet conduits and two outlet conduits.
17. The apparatus as recited in claim 16 wherein the inlet conduits
and the outlet conduits have one valve each.
18. The apparatus as recited in claim 17 wherein one inlet conduit
and one outlet conduit are connected to the first vertical chamber
of the suction and pumping assembly, the other inlet conduit and
the other outlet conduit are connected to the second vertical
chamber of the suction and pumping assembly.
19. The apparatus as recited in claim 18 wherein the liquid metal
partially fills both the first vertical chamber of the suction and
pumping assembly and the second vertical chamber of the suction and
pumping assembly.
20. The apparatus as recited in claim 19 wherein the pumping is
achieved by: a. the AC-powered reciprocating MHD pump driving down
the working fluid in a vertical chamber of the suction and pumping
assembly during one half of the AC cycle, the driving down of the
liquid metal causing the sucking in of the working fluid into the
corresponding vertical chamber of the suction and pumping assembly
through the corresponding inlet conduit; b. the AC-powered
reciprocating MHD pump driving up the working fluid in a vertical
chamber of the suction and pumping assembly during the other half
of the AC cycle, the driving up of the liquid metal causing the
pumping out of the working fluid from the corresponding vertical
chamber of the suction and pumping assembly through the
corresponding outlet conduit;
21. The apparatus as recited in claim 1 wherein the apparatus
comprises a plurality of suction and pumping assemblys connected in
parallel.
22. The apparatus as recited in claim 1 wherein the apparatus is
used as a pump in a two-phase cooling system
23. The apparatus as recited in claim 1 wherein the apparatus is
used as a compressor in a vapor compression system.
24. A system for two-phase cooling of a hot source, the system
comprising: a. an evaporator placed adjacent to the hot source, the
evaporator absorbing the heat from the hot source causing the
evaporation of a coolant circulating over the hot source; b. a
first conduit connected to the evaporator for the transfer of the
vapor formed as a result of the evaporation of the coolant; c. a
condenser connected to the first conduit for liquefying the vapor;
d. a second conduit connected to the condenser for transfer of the
liquid formed as a result of liquefying the vapor. e. a fluid pump
connected to the second conduit, the fluid pump comprising: i. a
suction and pumping assembly comprising: 1. a first vertical
chamber and a second vertical chamber connected using an
intermediate horizontal chamber, 2. liquid metal partially filling
the chambers of the suction and pumping assembly, and 3. an
AC-powered reciprocating MHD pump for driving the liquid metal in
the chambers of the suction and pumping assembly in an oscillatory
manner; ii. at least one inlet conduit connected to the suction and
pumping assembly, the inlet conduit allowing the liquid to be
sucked into the suction and pumping assembly, the liquid being
sucked in due to the oscillatory motion of the liquid metal; iii.
at least one outlet conduit connected to the suction and pumping
assembly, the outlet conduit allowing the liquid to be pumped out
of the suction and pumping assembly, the liquid being pumped out
due to the oscillatory motion of the liquid metal; and iv. a
plurality of valves in the inlet and outlet conduits for
controlling the inlet and outlet flow of the liquid; and v. a third
conduit connected to the fluid pump for transfer of the liquid back
to the evaporator.
25. A system vapor compression, the system comprising: a. an
evaporator for evaporation of a refrigerant at low pressure; b. a
first conduit connected to the evaporator for the transfer of the
low pressure vapor formed as a result of the evaporation of the
refrigerant; c. a compressor connected to the second conduit, the
compressor converting the low pressure vapor into high pressure
vapor, the compressor comprising: i. a suction and pumping assembly
comprising: 1. a first vertical chamber and a second vertical
chamber connected using an intermediate horizontal chamber, 2.
liquid metal partially filling the chambers of the suction and
pumping assembly, and 3. an AC-powered reciprocating MHD pump for
driving the liquid metal in the chambers of the suction and pumping
assembly in an oscillatory manner; ii. at least one inlet conduit
connected to the suction and pumping assembly, the inlet conduit
allowing the low pressure vapor to be sucked into the suction and
pumping assembly, the low vapor being sucked in due to the
oscillatory motion of the liquid metal; iii. at least one outlet
conduit connected to the suction and pumping assembly, the outlet
conduit allowing the high pressure vapor to be pumped out of the
suction and pumping assembly, the high pressure vapor being pumped
out due to the oscillatory motion of the liquid metal; and iv. a
plurality of valves in the inlet and outlet conduits for
controlling the inlet and outlet flow of the vapor; d. a condenser
connected to the first conduit for liquefying the high pressure
vapor; e. a second conduit connected to condenser for transfer of
the high pressure refrigerant formed as a result of liquefying the
vapor; f. a valve connected to the second conduit for converting
the high pressure refrigerant to a low pressure refrigerant; and g.
a third conduit connected to the valve to enable the circulation of
the refrigerant.
Description
BACKGROUND
[0001] The present invention relates to applications of
magnetohydrodynamic (MHD) pumps. More particularly, it relates to
the use of MHD pumps for pumping of non-conductive (dielectric)
fluids.
[0002] Electronic devices such as central processing units,
graphic-processing units and laser diodes as well as electrical
devices, such as transformers, generate a lot of heat during
operation. If generated heat is not dissipated properly from high
power density devices, this may lead to temperature buildup in
these devices. The buildup of temperature can adversely affect the
performance of these devices. For example, excessive temperature
buildup may lead to malfunctioning or breakdown of the devices. So,
it is important to remove the generated heat in order to maintain
normal operating temperatures of these devices. A number of cooling
systems have been proposed for the removal of the generated
heat.
[0003] Some proposed cooling systems, including the one referred
previously, involve single phase cooling using liquid metal. These
cooling systems use MHD pumps for controlling the flow of the
coolant, i.e. liquid metal. A number of MHD pump configurations
exist in prior art.
[0004] MHD pumps, such as the one referred to previously, can
attain high mass flow rates (.about.50 g/s in miniature pumps) at
sub-1W power dissipation levels. The excellent fluid flow
characteristics combined with high thermal conductivities of liquid
metals result in better extraction of heat from the source and
better rejection in the ambient heat exchanger.
[0005] However, in some applications, the advantages offered by
using liquid metal are offset by other considerations such as the
high volume, high weight and high electrical conductivity of the
liquid metal. For example, in portable systems such as laptops and
notebooks, the high volume and weight of liquid metals is a
restriction on their use as coolants. Moreover, in case of cooling
of high voltage power supplies and transformers, the use of
electrically conductive liquid metals is not recommended. For such
applications, non-conductive fluids such as water may be used.
Further, two-phase cooling may be employed so as to benefit from
the high latent heat of vaporization of the coolants. One such
two-phase cooling system is illustrated in FIG. 1. The two-phase
cooling system is used for cooling a hot source 102. Hot source 102
may be a microelectronic chip, an optoelectronic chip, a laser
diode, a light emitting diode (LED), a high voltage power supply, a
central processing unit of a computer etc. A coolant 104 present in
evaporator 106 is vaporized on the surface of hot source 102,
resulting in the extraction of heat from hot source 102. The vapor
so formed is transferred to a condenser 108 that rejects heat to
the ambient atmosphere and liquefies the vapor. The coolant so
formed is re-circulated over hot source 102 with the help of a pump
110.
[0006] Pump 110 may be a conventional pump. However, MHD pumps are
more reliable and safe compared to other pumps, as MHD pumps do not
have any mobile parts (with the exception of the conductive fluid
itself). Therefore, an MHD pump may be used so as to benefit from
the advantages offered by an MHD pump over a conventional pump.
However, an MHD pump needs to be adapted for the purpose of pumping
a non-conductive fluid.
[0007] One such adaptation of an MHD pump for fluid pumping is
discussed in U.S. Pat. No. 6,241,480, titled
"Micro-Magnetohydrodynamic Pump And Method For Operation Of The
Same". The patent discloses a system in which a valving liquid
metal piston and a pumping liquid metal piston are used for pumping
fluids. The valving piston regulates the flow the fluid in and out
of the system, while the pumping liquid metal piston pumps enables
the suction and pumping of the fluid. Both the liquid metal pistons
are driven magnetohydrodynamically in an oscillatory manner (the
direction of motion of the pistons is varied periodically).
However, this system suffers from certain disadvantages. Firstly,
the movement of the two liquid metal pistons has to be synchronized
for proper functioning. Secondly, the system produces discontinuous
outflow of the fluid since the outflow is restricted to half the
oscillatory cycle of the pistons (in one particular embodiment,
fluid is pumped out only when the valving piston moves to the left
and the pumping piston moves up, and not in the reverse movement).
Thirdly, the valve action is based on the surface tension
properties of liquid metals resulting in poor pressure heads and
poor mean time between failures (MTBF).
[0008] Hence, there is a need for an improved pump for fluid
pumping applications.
SUMMARY
[0009] The present invention is directed to an improved pump for
pumping of fluids, specifically non-conductive (dielectric)
fluids.
[0010] An object of the present invention is to provide an improved
fluid pump that combines the advantages of liquid metal MHD pumps
with the advantages of high reliability fluid flow valves.
[0011] Another object of the present invention is to provide a
non-bulky fluid pump that is suitable for use for two-phase cooling
using non-conductive fluids in portable systems such as
laptops.
[0012] Another object of the present invention is to provide a
safer fluid pump that has a lesser number of movable parts as
compared to conventional pump.
[0013] Another object of the present invention is to provide an
improved fluid pump that is suitable for use for two-phase cooling
using non-conductive fluids in high voltage systems such as
transformers.
[0014] A further object of the present invention is to provide an
improved fluid pump that is suitable for use as a vapor compressor
in a vapor compression system.
[0015] To achieve the foregoing objectives, and in accordance with
the purpose of the present invention as broadly described herein,
the present invention provides an improved fluid pump. The pump
combines a liquid metal MHD pump with a plurality of fluid flow
valves for enabling good pumping performance. The pump provided by
the present invention comprises a suction and pumping assembly, the
suction and pumping assembly in turn comprising a first vertical
chamber and a second vertical chamber connected using an
intermediate horizontal chamber. Liquid metal partially fills the
first vertical chamber and the second vertical chamber of the
suction and pumping assembly. An AC-powered reciprocating MHD pump
is provided for driving the liquid metal in the chambers of the
suction and pumping assembly in an oscillatory manner. The pump
further comprises at least one inlet conduit connected to the
suction and pumping assembly, at least one outlet conduit connected
to the suction and pumping assembly and a plurality of valves in
the inlet and outlet conduits. The inlet conduits enable the
suction of a working fluid into the suction and pumping assembly.
The outlet conduits enable the pumping of the working fluid out of
the suction and pumping assembly The valves in the inlet conduits
and the outlet conduits control the flow of the working fluid in
and out of the pump. The suction and the pumping of the working
fluid are caused by the oscillatory motion of the liquid metal in
the suction and pumping assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The preferred embodiments of the invention will hereinafter
be described in conjunction with the appended drawings provided to
illustrate and not to limit the invention, wherein like
designations denote like elements, and in which:
[0017] FIG. 1 is a block diagram of a two-phase cooling system;
[0018] FIG. 2 illustrates a fluid pump in accordance with a first
embodiment of the present invention;
[0019] FIG. 3 illustrates a fluid pump in accordance with a second
embodiment of the present invention;
[0020] FIG. 4 illustrates a fluid pump in accordance with a third
embodiment of the present invention;
[0021] FIG. 5 illustrates a fluid pump in accordance with a fourth
embodiment of the present invention; and
[0022] FIG. 6 is a block diagram of a vapor compression system, of
which the present invention forms a part.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0023] The present invention provides a pump for pumping of working
fluids. More particularly, the invention provides pump for pumping
of non-conductive fluids.
[0024] The pump combines fluid flow valves with liquid metal and an
AC-powered reciprocating MHD pump. The valves are used to provide
direction to the flow of the working fluid. The AC-powered MHD pump
is used to drive the liquid metal in an oscillatory manner, the
motion of the liquid metal enabling the suction and pumping of the
working fluid.
[0025] Referring now primarily to FIG. 2, the structure of the pump
in accordance with a first embodiment of the present invention will
hereinafter be described. The pump in accordance with the first
embodiment comprises a suction and pumping assembly 200 for sucking
and pumping the working fluid, an inlet conduit 202 for allowing
inflow of the working fluid, an outlet conduit 204 for allowing
outflow of the working fluid and a valve 206 in inlet conduit 202
and a valve 207 in outlet conduit 204.
[0026] Suction and pumping assembly 200 comprises three hollow
chambers--a first (left) vertical chamber 208, a second (right)
vertical chamber 210 and an intermediate horizontal chamber 212.
First vertical chamber 208 and second vertical chamber 210 are both
partially filled with a liquid metal 214. Intermediate horizontal
chamber 212 is completely filled with liquid metal 214. Liquid
metal 214 is driven in an oscillatory manner by an AC-powered
reciprocating MHD pump 216 connected to intermediate horizontal
chamber 212.
[0027] Inlet conduit 202 is connected to first vertical chamber 208
and outlet conduit 204 is connected to second vertical chamber 210.
Moreover, first vertical chamber 208 and second vertical chamber
210 are connected through an intermediate conduit 218 to enable the
transfer of the working fluid. Intermediate conduit 218 has a valve
220 for ensuring the unidirectional transfer of the working fluid
from first vertical chamber 208 to second vertical chamber 210.
[0028] The working fluid is sucked into first vertical chamber 208
through inlet conduit 202, transferred to second vertical chamber
210 through intermediate conduit 218 and pumped out through outlet
conduit 204. The suction, transfer and pumping of the working fluid
is achieved by the oscillatory motion of liquid metal 214. This
oscillatory motion of liquid metal 214 is governed by cycles of the
AC supply that drives AC-powered reciprocating MHD pump 216.
[0029] During one half of the AC cycle, liquid metal 214 in first
vertical chamber 208 is driven down. As a result, the working fluid
is sucked into first vertical chamber 208 through inlet conduit
202. During the same AC cycle, the working fluid already in second
vertical chamber 210 is pumped out through outlet conduit 204.
Valve 220 ensures that the working fluid is not transferred from
second vertical chamber 210 to first vertical chamber 208 during
this cycle.
[0030] During the other half of the AC cycle, liquid metal 214 in
first vertical chamber 208 is driven up. As a result, the working
fluid is transferred from first vertical chamber 208 to second
vertical chamber 210 through intermediate conduit 218. Valve 206
ensures that the working fluid is not pumped out of first vertical
chamber 208 through inlet conduit 202 in this cycle. Valve 207
ensures that the working fluid is not sucked into second vertical
chamber 210 through outlet conduit 204 in this cycle.
[0031] This embodiment results in a half-rectified (discontinuous)
flow of the working fluid, with the outflow and inflow of the
working fluid being synchronized.
[0032] Referring now primarily to FIG. 3, the structure of the pump
in accordance with a second embodiment of the present invention
will hereinafter be described. The pump in accordance with the
second embodiment comprises a suction and pumping assembly 300 for
sucking and pumping the working fluid, an inlet conduit 302 for
allowing the inflow of the working fluid, an outlet conduit 304 for
allowing the outflow of the working fluid and a valve 306 in inlet
conduit 302 and a valve 307 in outlet conduit 304.
[0033] Suction and pumping assembly 300 comprises three hollow
chambers--a first vertical chamber 308, a second vertical chamber
310 and an intermediate horizontal chamber 312. First vertical
chamber 308 is partially filled and second vertical chamber 310 is
completely filled with a liquid metal 314. Intermediate horizontal
chamber 312 is completely filled with liquid metal 314. Liquid
metal 314 is driven in an oscillatory manner by an AC-powered
reciprocating MHD pump 316 connected to intermediate horizontal
chamber 312.
[0034] Inlet conduit 302 and outlet conduit 304 are both connected
to first vertical chamber 308. Second vertical chamber 310 is
connected to a reservoir 318 filled with an inert fluid 320. Inert
fluid 320 may be any fluid that does not react with liquid metal
314 and prevents surface oxidation. Examples of such fluid include
Fluorinert and weakly acidic water with pH between 3 and 4.
[0035] The working fluid is sucked into first vertical chamber 308
through inlet conduit 302 and pumped out through outlet conduit
304. The suction and pumping of the working fluid is achieved by
the oscillatory motion of liquid metal 314. This oscillatory motion
of the liquid metal 314 is governed by cycles of the AC supply that
drives AC-powered reciprocating MHD pump 316.
[0036] During one half of the AC cycle, liquid metal 314 in first
vertical chamber 308 is driven down. As a result, the working fluid
is sucked into first vertical chamber 308 through inlet conduit
302. Valve 307 ensures that the working fluid is not sucked into
first vertical chamber 308 through outlet conduit 304 during this
cycle. During the other half of the AC cycle, liquid metal 314 in
first vertical chamber 308 is driven up. As a result, the working
fluid is pumped out through outlet conduit 304.
[0037] Valve 306 ensures that the working fluid is not pumped out
of first vertical chamber 308 through inlet conduit 302 during this
cycle.
[0038] Hence, this embodiment results in a half-rectified
(discontinuous) flow of the working fluid, with the inflow and
outflow of the working fluid being out of phase.
[0039] Referring now primarily to FIG. 4, the structure of the pump
in accordance with a third embodiment of the present invention will
hereinafter be described. The apparatus in accordance with the
third embodiment comprises a suction and pumping assembly 400 for
sucking and pumping the working fluid, two inlet conduits 402 and
404 for the inflow of the working fluid, two outlet conduits 406
and 408 for the outflow of the working fluid and four valves 410,
412, 414 and 416, one in each conduit.
[0040] Suction and pumping assembly 400 comprises three hollow
chambers--a first vertical chamber 418, a second vertical chamber
420 and an intermediate horizontal chamber 422. First vertical
chamber 418 and second vertical chamber 420 are both partially
filled with a liquid metal 424. Intermediate horizontal chamber 422
is completely filled with liquid metal 424. Liquid metal 424 is
driven in an oscillatory manner by an AC-powered reciprocating MHD
pump 426 connected to intermediate horizontal chamber 422.
[0041] Inlet conduit 402 and outlet conduit 406 are connected to
first vertical chamber 408. On the other hand, inlet conduit 404
and outlet conduit 408 are connected to second vertical chamber
420.
[0042] The working fluid is sucked into either first vertical
chamber 418 through inlet conduit 402 or into second vertical
chamber 420 through inlet conduit 404. Thereafter, the working
fluid is pumped out of the same chamber it was sucked into, through
either outlet conduit 406 or outlet conduit 408. For example, in
case the working fluid is sucked into first vertical chamber 418,
it will be pumped out of the same chamber through outlet conduit
406. The suction, transfer and pumping of the working fluid is
achieved by the oscillatory motion of liquid metal 424. This
oscillatory motion of liquid metal 424 is governed by cycles of the
AC supply that drives AC-powered reciprocating MHD pump 426.
[0043] During one half of the AC cycle, liquid metal 424 in first
vertical chamber 418 is driven down. As a result, the working fluid
is sucked into first vertical chamber 418 through inlet conduit
402. The downward motion of liquid metal 424 in first vertical
chamber 418 causes an upward motion of liquid metal 424 in second
vertical chamber 420. This causes the working fluid in this chamber
to be pumped out through outlet conduit 408. Valve 412 ensures that
the working fluid is not sucked into first vertical chamber 418
through outlet conduit 406 during this cycle. Moreover, valve 414
ensures that the working fluid is not pumped out of second vertical
chamber 420 through inlet conduit 404 during this cycle.
[0044] During the other half of the AC cycle, liquid metal 424 in
first vertical chamber 418 is driven up. As a result, the working
fluid is pumped out of first vertical chamber 418 through outlet
conduit 406. The upward motion of liquid metal 424 in first
vertical chamber 418 causes a downward motion of liquid metal 424
in second vertical chamber 420. This causes the working fluid to be
sucked in to second vertical chamber 420 through inlet conduit 404.
Valve 410 ensures that the working fluid is not pumped out of first
vertical chamber 418 through inlet conduit 402 during this cycle.
Moreover, valve 416 ensures that the working fluid is not sucked
into second vertical chamber 420 through outlet conduit 408 during
this cycle.
[0045] This embodiment results in a fully rectified (almost
continuous) flow of the working fluid.
[0046] In a fourth embodiment of the present invention, suction and
pumping assemblies, in accordance with any of the previously
discussed embodiments, are combined in parallel. Such a structure
results in an increase in the pumping capacity and pressure head.
This results in an increase in the power of the pump. Referring now
primarily to FIG. 5, an exemplary structure of the pump in
accordance with the fourth embodiment of the present invention will
hereinafter be described. Suction and pumping assemblies 500.sub.1
to 500.sub.M, corresponding to the first embodiment of the pump
(shown in FIG. 2), are combined in parallel. The working fluid
flows into suction and pumping assemblies 500.sub.1 to 500.sub.M
through an inlet conduit 502 and is pumped out through an outlet
conduit 504.
[0047] The operating voltage of the pump provided by this
embodiment is proportional to the number of suction and pumping
assemblies connected in parallel. This provides flexibility for
increasing the operating voltage of the pump. Higher operating
voltage may be desirable in some cases due to the following
reason.
[0048] Conventional pumps operate at a voltage of <20 mV. On the
other hand, voltages provided by typical power supplies are of the
order of 5-100V. This requires the downconversion of the supply
voltage to the low operating voltage of the pump. The efficiency of
downconversion becomes smaller (<90%) for voltage downconversion
ratios >100. The size of the downconverting circuit also becomes
large when the voltage downconversion ratios are large. The
above-mentioned embodiment allows operation at an increased
voltages and lower voltage downconversion ratios.
[0049] In the embodiments of the present invention, the suction and
pumping assembly has been shown as a U-shaped structure. It will be
apparent to one skilled in the art that the suction and pumping
assembly can have other similar shapes including but not limited to
a distorted U-shape (where the angles between the horizontal
intermediate chamber and the first and second vertical chambers are
different from 90.degree.).
[0050] In all the above-mentioned embodiments of the present
invention, one-way moving valves such as ball and cage valves and
flapper valves may be used. Alternatively, non-moving valves such
as Tesla valves may be used. U.S. Pat. No. 6,227,801 titled "Method
For Making Micropump" describes the use of non-moving valves in
miniature pumps. The valves used in the abovementioned embodiments,
do not need external control i.e. their operation is only dependent
on the pressure differences across the valve.
[0051] A number of different liquid metals may be used in the
above-mentioned embodiments without departing from the scope of the
invention. For example, liquid metals having high thermal
conductivity, high electrical conductivity and high volumetric heat
capacity can be used. Some examples of liquid metal that can be
used in the above-mentioned embodiments include: sodium potassium
eutectic alloy, gallium-indium alloy, mercury, bismuth, indium and
gallium. Also, a number of working fluids can be used in the
invention. The working fluid should not react with gallium or form
oxides or any compound that result in long term fouling. Typical
examples of such working fluids include slightly acidic water with
pH between 3 and 4, fluorinerts, CFCs, R134a, and Puron. The pumps
can also be used for pumping air if the surface of liquid metal is
covered with inert fluid or nitrogen or any inert gas. The chambers
of the suction and pumping assembly as well as the inlet and outlet
conduits can be constructed of polymer materials such as Teflon or
polyurethane. Tungsten or nickel-coated copper can be used as
electrodes.
[0052] The pump provided by the present invention delivers maximum
power efficiency at an optimal resonant frequency. This optimal
resonant frequency in turn depends on factors such as the volume of
the working fluid transferred between the first and second
chambers, the external pressure head, length of the chambers and
the diodicity (flow to leakage ratio) of the valves. For example,
for a pump with 1-2 cm.sup.3 of working fluid with density of 1-2
g/cc, the optimal resonant frequency is in the range of 1-30 Hz,
the exact value depending on the other factors.
[0053] Referring back to FIG. 1, an application of the present
invention will hereinafter be discussed. As described previously,
FIG. 1 shows a general two-phase cooling system. The pump provided
by the present invention is used in such a two-phase cooling system
as pump 110. In the preferred embodiment of the system provided by
the present invention, Fluorinert is used as the coolant i.e. the
working fluid. Fluorinert is a colorless, fully fluorinated liquid
such as Fluorinert.TM. Electronic Liquid FC-72 provided by 3M.
[0054] The pump provided by the present invention can also be used
as a vapor compressor. Referring now primarily to FIG. 6, an
application of the pump as a vapor compressor will hereinafter be
discussed. FIG. 6 shows a vapor compression system, commonly used
in air-conditioners and refrigerators. A refrigerant fluid such as
R134a is converted from a low pressure vapor state to a high
pressure fluid by a compressor 602. The high pressure fluid is
cooled at a condenser 604 by rejecting the heat to the ambient
atmosphere. The high pressure is next released through an expansion
valve 606 to a cold end chamber or evaporator 608. The expansion
results in cooling of the fluid and subsequent extraction of heat
from the walls of cold end chamber or evaporator 608. This
low-pressure refrigerant is re-circulated into compressor 602. The
present invention can be used in the vapor compression system as
compressor 602.
[0055] The present invention offers several advantages over prior
art. Firstly, the use of high reliability valves such as ball and
cage valves and Tesla valves results in improved fluid flow
performance. Secondly, the present invention is capable of
providing a variety of fluid flow profiles (both continuous and
discontinuous flow). Thirdly, the pump provided by the present
invention has low weight and volume and is thus suitable for use in
portable systems. Fourthly, the pump has less moving parts than
conventional pumps and is thus safer. Finally, the pump is suitable
for use in high-voltage systems due to its ability of pumping
non-conductive fluids.
[0056] While the preferred embodiments of the invention have been
illustrated and described, it will be clear that the invention is
not limited to these embodiments only. Numerous modifications,
changes, variations, substitutions and equivalents will be apparent
to those skilled in the art without departing from the spirit and
scope of the invention as described in the claims.
* * * * *