U.S. patent application number 10/684718 was filed with the patent office on 2005-04-14 for readying cooling circuits for use in fuel cells.
Invention is credited to Garg, Vijay, Huang, Chendong, Kim, Byung, Kumar, Mukesh, Mueller, Sherry, Schwartz, William, Shih, George.
Application Number | 20050077252 10/684718 |
Document ID | / |
Family ID | 34423010 |
Filed Date | 2005-04-14 |
United States Patent
Application |
20050077252 |
Kind Code |
A1 |
Shih, George ; et
al. |
April 14, 2005 |
Readying cooling circuits for use in fuel cells
Abstract
A flush and fill process is used to ready a fuel cell cooling
circuit for initial use. An external flushing system relasably
connected to the cooling circuit circulates flushing coolant
through the cooling circuit to remove contaminants from the wetted
surfaces of the cooling circuit before the fuel cell is put into
use. The flushing system includes a pump for circulating the
flushing coolant through the cooling circuit, filters for removing
contaminants from the coolant and a heater for elevating the
temperature of the coolant. Following the flushing process to
remove contaminants, the flushing system is disconnected from the
cooling circuit and the cooling circuit is filled with fresh
coolant.
Inventors: |
Shih, George; (Dearborn,
MI) ; Schwartz, William; (Pleasant Ridge, MI)
; Huang, Chendong; (Ann Arbor, MI) ; Kumar,
Mukesh; (Canton, MI) ; Kim, Byung; (West
Bloomfield, MI) ; Mueller, Sherry; (Ann Arbor,
MI) ; Garg, Vijay; (Canton, MI) |
Correspondence
Address: |
TUNG & ASSOCIATES
838 WEST LONG LAKE, SUITE 120
BLOOMFIELD HILLS
MI
48302
US
|
Family ID: |
34423010 |
Appl. No.: |
10/684718 |
Filed: |
October 14, 2003 |
Current U.S.
Class: |
210/767 |
Current CPC
Class: |
Y02E 60/50 20130101;
H01M 8/04044 20130101; H01M 8/04029 20130101 |
Class at
Publication: |
210/767 |
International
Class: |
B01D 036/00 |
Claims
1. A method of readying a fuel cell cooling circuit for use,
comprising: (A) flushing the cooling circuit to remove contaminants
from the cooling circuit; and, (B) filling the cooling circuit with
a volume of fresh coolant after step (A) has been completed.
2. The method of claim 1, wherein step (A) is performed by
circulating a volume of coolant between the cooling circuit and a
supply of the coolant external to said cooling circuit.
3. The method of claim 2, wherein step (A) includes filtering the
circulating coolant at a location external to the cooling
circuit.
4. The method of claim 3, wherein the filtering includes passing
the coolant through a particulate filter and a de-ionization
filter.
5. The method of claim 1, including the step of heating the coolant
circulated to the cooling circuit.
6. The method of claim 2, including the step of controlling the
pressure of the coolant circulated to the cooling circuit to
maintain the pressure within a desired pressure range.
7. The method of claim 2, including the step of blocking the flow
of coolant to a filter in the cooling system until step (A) is
complete.
8. The method of claim 2, wherein step (A) includes removing the
coolant from the cooling circuit after step (A) has been
completed.
9. A method of readying a fuel cell cooling circuit for use,
comprising: (A) connecting the cooling circuit to an external
coolant flushing system for flushing the cooling circuit; (B)
circulating a volume of coolant between the flushing system and the
cooling circuit, the flow of coolant through the cooling circuit
resulting in the removal of contaminants from component parts of
the cooling circuit; (C) removing contaminants from the coolant as
the coolant circulates through the flushing system; and, (D)
disconnecting the cooling circuit from the flushing system after
the cooling circuit has been flushed.
10. The method of claim 9, including the step of removing the
coolant from the cooling circuit before the cooling circuit is
disconnected from the flushing system.
11. The method of claim 9, wherein the volume of coolant is a fixed
volume, and the coolant is circulated between the cooling circuit
and the flushing system for a preselected time period.
12. The method of claim 9, including the step of blocking the flow
of coolant to a coolant filter in the cooling circuit while step
(B) is being performed, whereby contaminants are prevented from
accumulating in the coolant filter until the cooling circuit has
been readied for use.
13. The method of claim 9, wherein step (C) is performed by passing
the coolant through at least one contaminant filter in the flushing
system.
14. The method of claim 9, including the step of heating the
coolant in the flushing system to a temperature sufficient to
promote the removal of the contaminants from the component parts of
the cooling circuit.
15. The method of claim 9, including regulating the pressure of the
coolant circulating from the flushing system to the cooling
circuit.
16. The method of claim 9, including the step of filling the
cooling circuit with fresh coolant after step (D) has been
completed.
17. Apparatus for cleansing a fuel cell cooling circuit,
comprising: a flushing system connected to the cooling circuit for
flushing the cooling circuit of contaminants, the flushing system
including a supply of coolant, a filtering system for removing
contaminants from the coolant flowing through the flushing system,
and a pump for circulating a volume of the coolant between the
cooling circuit and the flushing system.
18. The apparatus of claim 17, wherein the filtering system
includes a particulate filter and a de-ionization filter.
19. The apparatus of claim 17, wherein the flushing system includes
a pressure regulator for regulating the pressure of the coolant
circulated from the flushing system to the cooling circuit.
20. The apparatus of claim 19, wherein the pressure regulator
includes a flow control valve connected between the pump and the
cooling circuit for controlling the flow of coolant flowing from
the flushing system to the cooling circuit.
21. The apparatus of claim 17, including a valve system for
controlling the flow of the coolant between the coolant supply, the
cooling circuit and the flushing system.
22. The apparatus of claim 17, wherein the flushing system includes
a heater for heating the coolant circulated from the flushing
system to the cooling circuit to a temperature sufficient to
promote the removal of contaminants from component parts of the
cooling circuit.
23. The apparatus of claim 17, wherein the cooling circuit is of
the type including a filter for removing contaminants from coolant
flowing to the fuel cell, and wherein the apparatus further
includes: a bypass system for causing the flow of coolant to bypass
cooling circuit filter when the flushing system is flushing the
cooling circuit of contaminants.
24. The apparatus of claim 17, including a controller for
controlling the operation of the pump and the valve system.
25. The apparatus of claim 17, wherein the flushing circuit is
releasably connected to the cooling circuit.
Description
FIELD OF THE INVENTION
[0001] The present invention broadly relates to cooling circuits
used in fuel cells, and deals more particularly with a method and
apparatus for cleansing and filling the cooling circuit for initial
use.
BACKGROUND OF THE INVENTION
[0002] Fuel cells are electro-chemical energy conversion devices
that generate electricity and heat by converting the chemical
energy of fuels, such as hydrogen and oxygen. A single fuel cell
normally consists of an electrolyte sandwiched between two thin
electrodes, a porous anode and a cathode. While a variety of
differing fuel cell types have been developed, all operate on
essentially the same principles. The fuel cell reaction produces
heat which must be extracted from the fuel cell in order to
maintain optimum operating efficiency. Sophisticated cooling and
temperature control circuits have been developed for fuel cells
which closely control operating temperatures. These cooling
circuits typically include channelized plates or passageways within
the fuel cell through which a coolant such as de-ionized water may
flow to carry heat away from the fuel cell to a heat exchanger or
other device for dissipating the heat.
[0003] In the case of fuel cells used to power vehicles such as an
automobile, the cooling circuit is located on-board the vehicle and
may include a variety of subsystems such as filters and temperature
controllers for conditioning the coolant. The condition of the
coolant, and particularly its purity, affect the efficiency of the
coolant to conduct heat away from the fuel cell. Ideally, the
coolant should not contain particulate contaminants greater than a
very small size and should have near zero electrical conductivity.
As a practical matter however, the coolant picks up small
particulates contaminants and conductive ions as it flows through
the cooling circuit. Various types of on-board particulate filters
and de-ionization filters have been devised to remove these
contaminants, however these devices are often limited in their
ability to remove contaminants, and in any event must be
periodically serviced or replaced due to contaminate buildup. Part
of the inefficiency of prior filters and rapid contaminate buildup
is due to the fact that a certain amount of the contaminants is
present on the wetted surfaces of the component parts of the
cooling system at the time of their installation and assembly.
Consequently, on initial start-up of the fuel cell, the coolant
flowing through the cooling circuit carries these initial
contaminants away, resulting in an immediate buildup of
contaminates in the filters, in turn reducing the overall
efficiency of the cooling circuit.
[0004] It would therefore be desirable to reduce the level of
contaminants present in the cooling circuit before it is filled
with coolant and put into use. The present invention is directed
towards satisfying this need.
SUMMARY OF THE INVENTION
[0005] A method is provided for readying a fuel cell cooling
circuit for use, comprising flushing the cooling circuit to remove
contaminants from the wetted surfaces of the cooling circuit, and
then filling the cooling circuit with a volume of fresh coolant.
The cooling circuit is flushed using an external flushing system
which is removal removably connected to the cooling circuit at the
time the fuel cell is being readied for its initial use. The
flushing system includes a supply of coolant, filters for removing
contaminants from the coolant and a series of valves for
controlling the flow of coolant between the flushing system and the
cooling circuit. Particulate contaminants and conductivity
increasing ions present within the component parts of the cooling
circuit are carried away by the flushing coolant to filters forming
part of the flushing system where they are filtered out of the
flushing coolant. The temperature and pressure of the flushing
coolant is regulated to enhance contaminant removal and protect
fuel cell components against excessive pressure. The cooling
circuit is flushed for a pre-selected time period, following which
all coolant is removed from the cooling circuit and the flushing
system is disconnected from the cooling circuit. After the flushing
coolant is removed from the cooling circuit, fresh coolant is
introduced into the cooling circuit to ready the fuel cell for
use.
[0006] Apparatus is provided for cleansing a fuel cell cooling
circuit, comprising a flushing system removably connected to the
cooling circuit for flushing the cooling circuit of contaminants.
The flushing system includes a supply of flushing coolant, a
filtering system for removing contaminants from the flushing
coolant, and a pump for circulating a volume of coolant between the
cooling circuit and the flushing system. The filtering system
desirably includes both particulate filters and a de-ionization
filter. The flushing system further includes a pressure regulator
for regulating the pressure of the coolant circulated from the
flushing system to the cooling circuit, and optionally also
includes a heater for heating the coolant to a temperature that is
sufficient to promote the removal of contaminants from component
parts of the cooling circuit. The flushing system also includes a
series of shut-off valves which may be controlled manually or
automatically to control the flow of flushing coolant between the
flushing system and the cooling circuit.
[0007] The invention advantageously reduces the level of
contaminants present in the cooling circuit when the fuel cell is
initially put into service, thereby increasing fuel cell efficiency
and fuel cell temperature control.
[0008] Another advantage of the invention is that the contaminant
filters forming part of the cooling circuit are not used to filter
out contaminants that are present in the coolant upon start-up of
the fuel cell, consequently, the filters are capable of operating
with greater efficiency and longer service life.
[0009] A further advantage of the invention is that larger
contaminating particles present in the coolant circuit at the time
of manufacture are flushed from the cooling circuit before the
start-up of the fuel cell.
[0010] These, and other advantages of the invention will be made
clear or will become apparent during the course of the following
description of a preferred embodiment of the present invention. In
the course of this description, reference will frequently be made
to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a combined schematic and diagrammatic view of a
flushing system connected to a cooling circuit for a fuel cell,
according to the preferred embodiment of the invention;
[0012] FIG. 2 is a block diagram of a control system for the
flushing system shown in FIG. 1; and
[0013] FIGS. 3a and 3b taken together, form a flow chart of the
steps used to carry out the method for readying a fuel cell
according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0014] Referring first to FIG. 1, a vehicle 10 includes an on-board
fuel cell system 12, including a fuel cell 14 which generates
electrical power used to drive the vehicle 10 or operate auxiliary
electrical systems on-board the vehicle 10. The fuel cell 14 may be
of any of various types which convert fuels such as hydrogen and
oxygen into electricity through electro-chemical conversion. A
by-product of the conversion process is heat generated within the
fuel cell 14 which must be dissipated or carried away from the fuel
cell 14. Accordingly, the fuel cell system 12 includes a cooling
circuit which typically will include heat exchangers (not shown),
coolant carrying lines, valves and other control devices for
controlling the flow of a coolant, such as de-ionized water through
the cooling circuit in order to carry heat away from the fuel cell
14. Such on-board circuits typically include a particulate filter
16 for filtering contaminants from a coolant, and a de-ionization
filter 18 for removing conductivity increasing ions from the
coolant.
[0015] In accordance with the present invention a flushing system
is provided external to the vehicle 10 which is removably connected
to the cooling circuit by releasable coolant line connections (not
shown) located at points on the vehicle 10, designated by the
letters "A" and "B".
[0016] The flushing system broadly includes a coolant storage tank
30, pump 46, particle filter tank 40, de-ionization filter 26,
coolant heater 28 and a series of later discussed valves which
control flow of coolant between the flushing system and the
on-board cooling circuit. The fluid connections coupling the
flushing system to the cooling circuit at points "A" and "B" are of
preferably of the quick-release type which is well known in the
art.
[0017] The coolant storage tank 30 is filled with a fixed volume of
a suitable coolant such as de-ionized water. Pump 46 draws the
coolant from the tank 30 into the particle filter tank 40. The flow
rate into the filter tank 40 is controlled by a shut-off valve 44.
The filter tank 40 is pressurized, and a pressure gage 42 is
provided to indicate the pressure of the coolant in the tank 40,
and therefore the flushing system lines. The filter tank 40 is
connected to the coolant storage tank 30 through a shut-off valve
48 which, when in the open position, allows any remaining coolant
in filter tank 40 to flow back into storage tank 30. The pump 46
together with the filter tank 40 and shut-off valve 44, 48 form a
flushing machine 24.
[0018] Coolant present in filter tank 40 is delivered under
pressure through line 56 through a shut-off valve 38 to both a
by-pass line 50 and another shut-off valve 36 immediately upstream
of the de-ionization filter 26. The by-pass line 50 allows a
desired amount of the coolant to by-pass the de-ionization filter,
as determined by the opening position of shut-off valves 36 and 38.
Valve 36 specifically limits the flow through the filter 26 so that
the capacity of this filter to remove and process the coolant is
not exceeded. Coolant exiting the filter 26 is delivered by line 58
through a three-way valve 34 to an optional coolant heater 28. As
will become apparent later, the three-way valve may be actuated at
the end of the flushing cycle to allow coolant present in line 58
to flow back into the storage tank 30. During the flushing cycle,
however, valve 34 is switched to a position that forces all flow of
coolant in line 58 to be delivered to the coolant heater 28.
[0019] Although satisfactory results may be realized when the
flushing coolant is at ambient temperature, it has been found that
superior results may be achieved if the coolant is heated to a
temperature sufficient to promote the removal of contaminants from
the wetted surfaces of the components that make up the cooling
circuit. Superior contaminant removal has been achieved when the
coolant is heated to a temperature of approximately 80.degree. C. A
temperature gage 32 and related temperature sensor (not shown) are
provided at the exit of the coolant heater in order to sense and
indicate the temperature of the coolant exiting the heater 28. The
heated coolant is delivered by flushing line 60 to a connection at
"A" which feeds into an on-board particulate filter 16. Although
some contaminants may be filtered out by the filter 16, most of the
particulates have been previously filtered in the filter tank 40.
The flushing coolant passes from the particulate filter 16 through
the heat exchanging passageways in the fuel cell 14 and are carried
away from the fuel cell by cooling circuit line 62.
[0020] Normally, the coolant exiting the fuel cell 14 in line 62 is
delivered to the on-board de-ionization filter 18. However, in
accordance with the present invention, a pair of shut off valves
20, 22 are provided which block the flow of coolant to the filter
18, and instead, re-route the flow so as to by-pass the filter 18
and deliver the coolant back through the flushing system line 65 to
the storage tank 30.
[0021] When the flushing system is initially connected to the
on-board cooling circuit at points "A" and "B", the cooling circuit
is empty of coolant and is ready for a flushing cycle. A fixed
quantity of the flushing coolant is stored in tank 30. The shuttle
valve 44 is adjusted between its fully open and fully closed
positions to regulate the pressure in the system to keep it below
the safe limits that can be tolerated by the fuel cell 14.
Initially, shut-off valve 38 is closed to allow the filter tank 44
to be filled with coolant drawn from the storage tank 30. Once
filled, shut-off valve 38 is opened and coolant flows both through
shut-off valve 36 to the filter 26 and through the by-pass line 50.
Shut-off valve 36 regulates the amount of coolant which flows
through the filter 26. The on-board particulate filter 16 removes
any particles that may have entered the coolant between the time it
flows from the filter tank 40 to the vehicle 10.
[0022] Although the flushing system described above may be operated
manually, it may be desirable in some applications to use a
partially or fully automated control system. In this respect,
attention is now directed also to FIG. 2 which shows a controller
64 for operating the flushing system. The controller 64 may be a
conventional, programmable logic controller (PLC) operating under
programmed instructions to carry out the various control functions
in accordance with real-time information supplied to the controller
64. The controller 64 delivers output control signals to operate
the coolant heater 28, pump 46 and the various, previously
described shut-off valves which, for sake of simplicity, are
collectively shown in FIG. 2 as a valve system 72. The controller
64 receives real time data from a pressure sensor 66, storage tank
level sensor 68, flow sensor 69, coolant quality sensor 71 and
temperature sensor 70.
[0023] The pressure sensor 66, as previously mentioned, senses the
pressure within the filter tank 40 which is also displayed on the
pressure gauge 42. A conventional level sensor 68 may be provided
in the storage tank 32 to verify that the correct amount of coolant
is present in the tank 30 before the flushing cycle commences and
to verify that the proper flow rates are being achieved, as
determined by the rate of coolant returned to the tank 30 and via
line 65. Although not shown in FIG. 1, one or more flow sensors 69
may be incorporated into various flushing system and cooling
circuit lines to measure flow rates. One or more coolant quality
sensors 71 may be provided to determine certain characteristics of
the coolant indicating its purity or quality. One such device would
be a conductivity sensor for determining the level of conductivity
increasing ions present in the coolant. The various components
forming the control system shown in FIG. 2 are conventional,
commercially available items, consequently their details need not
be described here.
[0024] Reference is also now made to FIGS. 3a and 3b which, taken
together, depict success steps used in carrying out the inventive
method by which the fuel cell coolant circuit 12 is readied for
use. The method starts at step 74 with a fixed volume of flushing
coolant present in the storage tank 30. The flushing system is
connected to the cooling circuit at step 76. This involves
connecting the cooling carrying lines of the flushing system to
quick release couplings on-board the vehicle, at points "A" and
"B", as previously described. Next, shut-off valves 20 and 22 are
closed at step 78, thereby causing the flushing coolant flowing out
of the fuel cell 14 on line 62 to bypass the filter 18. Next, at
step 80, shut-off valve 38 is closed and shut off valve 44 is
partially opened. Then, at step 82, pump 46 is activated, causing
coolant in tank 32 to flow through lines 52 and 54 into the filter
tank. This filling procedure is continued until the tank is full at
step 84, following which shut off valve 38 is opened at step
86.
[0025] At step 88, the shuttle valve 44 is opened slightly further
to increase the flow of coolant entering the tank 40, until coolant
within the tank 40 is within desired pressure levels indicated at
90. If the pressure is above or below the desired limits, shut-off
valve 44 is adjusted as required, at step 92. Once the desired
pressure within the tank is achieved, shut-off valve 36 is adjusted
to achieve a desired flow rate through the deionization filter 26.
Because the de-ionization filter 26 represents a flow constriction
that creates fluid back pressure, there is a limit to the amount of
coolant that may be passed through the filter 26. In step 96, the
level of coolant in the storage tank 30 is assessed, and when it is
determined that sufficient coolant is returning to the tank 30 (via
line 65) as evidenced by the fluid level in the tank, the coolant
heater 28 is activated at step 102. In the event that insufficient
coolant is being returned to the tank 30, the shut-off valve 36 is
adjusted to increase the flow, at step 100.
[0026] At step 104, a previously described temperature sensor 70
determines whether the temperature of the coolant has been elevated
to a desired level, for example 80.degree. C. If the temperature is
out of range, the heater 28 is adjusted at step 106, otherwise a
determination is made at 108 of whether the flow of flushing
coolant through the flushing system and the coolant circuit has
stabilized, i.e. proper coolant temperature, pressure and flow
rates. If the flushing system does not stabilize, steps are taken
to adjust the control parameters at step 110. Otherwise, at step
112, the flushing coolant is allowed to circulate from the flushing
system to the coolant circuit for a period of time necessary to
remove coolant contaminants at a specified level. In one
application, it was found that a circulation period of
approximately 40 minutes was appropriate, however the exact
duration will depend on a variety of factors unique to each
specific fuel cell application. The circulation period may be
adjusted upwardly of downwardly depending upon real time
information gathered by sensors measuring the purity and quality of
the coolant, such as the previously mentioned conductivity
sensor.
[0027] At the end of the circulation period, the pump 46 is turned
off at step 114, following which the flushing system may be
disconnected from the coolant circuit in step 116. With the
flushing system disconnected from the vehicle 10, all of the
flushing coolant present within the flushing system must be
removed. Consequently, first, shut-off valve 48 is opened at step
118, and at step 120 the three-way valve 34 is switched to a
position which drains coolant in lines 58 and 60 back into the
storage tank 30. Shut-off valves, 20, 22 on-board vehicle 10 are
opened, at step 122, thereby re-connecting filter 18 into the
on-board cooling circuit.
[0028] Next, at step 124, the on-board cooling circuit is filled
with fresh coolant, thereby readying the fuel cell system 12 for
initial use. At step 126, all of the coolant present in storage
tank 30 is removed and may be subjected to reclamation or
re-cycling processes to renew the coolant for future use. A fresh
quantity of flushing coolant is then introduced into the tank 30,
thereby readying the flushing system for flushing the next fuel
cell system 12, and completing the last step in the process, as
indicated at block 128.
[0029] From the foregoing, it may be appreciated that the method
and apparatus for readying a fuel cell cooling circuit described
above not only provide numerous advantages, but do so in a
particularly simple and economic manner. It is recognized, of
course, that those skilled in the art may make various
modifications or additions to the preferred embodiment chosen to
illustrate the invention without departing from the spirit and
scope of the present contribution to the art. Accordingly, it is to
be understood that the protection sought and to be afforded hereby
should be deemed to extend to the subject matter claimed and all
equivalents thereof fairly within the scope of the invention.
* * * * *