Note: Descriptions are shown in the official language in which they were submitted.
TIGHT TEMPERATURE CONTROL AT A THERMAL LOAD WITH A TWO PHASE
PUMPED LOOP, OPTIONALLY AUGMENTED WITH A VAPOR COMPRESSION
CYCLE
TECHNICAL FIELD
[0001] This disclosure relates generally to cooling systems.
BACKGROUND
[0002] The statements in this section merely provide background information
related
to the present disclosure and may not constitute prior art.
[0003] Conventional two-phase pump loops have been in existence since the
1980's
as two-phase evaporative cooling units. One example of a conventional two-
phase
pump loop is provided in U.S. Patent No. 6,948,556. However, the primary
difference
between the commercially available units and the two-phase pump loop (TPPL) of
the
present disclosure is the cooling temperature at the evaporator. An apparatus,
such as
a high-energy laser (HEL), needs to be maintained at a constant temperature
regardless of ambient temperature. However, the commercially available units
allow the
evaporator temperature to change with ambient temperature.
SUMMARY
[0004] According to a broad aspect, the invention provides a two-phase pump
loop
(TPPL) for dissipating a thermal load during operation of an apparatus; the
TPPL
comprising: a vapor/liquid receiver configured to store a coolant; a pump
configured to
force the coolant to flow through the TPPL; an evaporator configured to absorb
heat
(QABSORBED) from the apparatus, the evaporator having an inlet and an outlet;
a
condenser configured to release heat (QREJETED) in order to remove the heat
(QREJECTED) from the TPPL; a valve (V1) configured to regulate a pressure or
temperature of the coolant exiting the evaporator; the V1 having a control set
point set
at a first pressure (P1set) to achieve an evaporator exit pressure that is a
saturation
pressure (PH) for the coolant at a predetermined exit temperature from the
evaporator;
a valve (V2) having a control set point set at a second pressure (P2set) to
prevent the
vapor/liquid receiver pressure from going to a pressure/temperature that is
lower than a
predetermined value (PL); and a controller configured to control the set
points of V1 and
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V2; wherein the controller is configured to set P1set so as to provide a
predetermined
temperature at the outlet of the evaporator and the controller is configured
to vary P2set
so as to maintain the pressure in the vapor/liquid receiver at or above PL;
wherein the
TPPL is configured to cool the thermal load with tight control of the
temperature of the
coolant that is cooling the apparatus.
[0005] The control set point of V2 is varied to balance the heat
(QREJECTED)
removed from the condenser with the heat (QABSORBED) absorbed at the
evaporator
along with any other heat additions or losses encountered.
[0006] The two-phase pump loop (TPPL) further comprises a liquid return
valve; and
a liquid separator in fluid communication with the outlet of the evaporator;
the liquid
separator configured to return a substantial portion of the liquid portion of
the coolant
through the liquid return valve to the vapor/liquid receiver.
[0007] The two-phase pump loop (TPPL) further comprises a sensor configured
to
measure the level of liquid in the liquid separator in order to control the
flow through the
liquid return valve.
[0008] The TPPL is integrated with a vapor cycle system (VCS); the VCS is
configured to remove heat from the TPPL when the temperature of the coolant
flowing
through the inlet of the evaporator is about ambient temperature or less than
ambient
temperature.
[0009] The V1 and V2 are independently selected to be an expansion valve, a
pressure reducing valve, or a back pressure regulator.
[0010] A thermal management system for dissipating a thermal load during
operation
of an apparatus; the thermal management system comprising a two-phase pump
loop
(TPPL) and a primary vapor cycle system (p-VCS) that are configured to use the
same
coolant and to be in fluid communication through a vapor/liquid receiver;
wherein the
TPPL comprises: the vapor/liquid receiver configured to store the coolant; a
pump
configured to force the coolant to flow throughout the TPPL; an evaporator
configured to
absorb heat (QABSORBED) from the apparatus, the evaporator having an inlet and
an
outlet; a valve (V1) having a control set point set at a first pressure
(P1set) measured
downstream of the evaporator, the P1set set to achieve an evaporator exit
pressure that
is the saturation pressure (PH) of the coolant at a predetermined target exit
temperature
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from the evaporator; a valve (V2) having a control set point set at a second
pressure
(P2set) to prevent the vapor/liquid receiver pressure from going to a
pressure/temperature that is lower than a predetermined value (PL); and a
controller
configured to control the set points of V1 and V2; wherein the controller is
configured to
set P1set so as to provide a predetermined temperature at the outlet of the
evaporator
and the controller is configured to vary P2set so as to maintain the pressure
in the
vapor/liquid receiver at or above PL; wherein the p-VCS comprises: the
vapor/liquid
receiver configured to store the coolant; a condenser configured so that the
coolant
releases heat (QREJECTED) in order to remove heat (QREJECTED) from the thermal
management system; a first compressor; a valve (V3) configured to act as an
expansion
valve; the V3 having a control set point set to maintain a predetermined
pressure at an
outlet of the compressor; and one or more recuperators configured with a
condenser
exit flow or hot gas bypass flow to prevent any coolant in liquid form from
entering the
compressor; wherein V2 is configured to allow a portion of the coolant exiting
the
compressor to flow back into the vapor/liquid receiver in order to prevent
overcooling of
the vapor/liquid receiver while allowing the compressor to continue to run.
[0011] The control set points of V2 and V3 are variable in order to balance
the heat
(QREJECTED) removed from the condenser with the heat (QABSORBED) absorbed at
the evaporator along with any other heat additions or losses encountered.
[0012] The p-VCS comprises a second compressor located parallel to the
compressor in order to minimize power draw.
[0013] The V1, V2, and V3 are independently selected to be an expansion
valve, a
pressure reducing valve, or a back pressure regulator.
[0014] The thermal management system further comprises a secondary vapor cycle
system (s-VCS) configured to operate at a lower temperature than the p-VCS and
is
able to operate at a smaller thermal load or to operate when the p-VSC is not
operational; wherein the s-VCS comprises: a phase change material (PCM)
located in
an evaporator/condenser (PCM/Ev/Cnd), the PCM providing thermal energy storage
by
absorbing heat until the p-VCS, the s-VCS, or both the p-VCS and s-VCS are
operational; an accumulator; an expansion valve; a third compressor configured
to force
a the coolant to flow to the vapor/liquid receiver or to the condenser; a
controller
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configured to control the expansion valve such that only vapor enters the
third
compressor; and a plurality of valves configured to allow the s-VCS to use the
condenser located in the p-VCS when the p-VCS is turned off or to allow the
coolant to
flow to the vapor/liquid receiver when the p-VCS is operational.
[0015] One or more of the compressors are run using a battery power source.
[0016] A thermal management system for dissipating a thermal load during
operation
of an apparatus; the thermal management system comprising a two-phase pump
loop
(TPPL) and a vapor cycle system (VCS) configured to use the same coolant; the
TPPL
comprising: a vapor/liquid receiver configured to store a coolant; a pump
configured to
force the coolant to flow throughout the TPPL; the flow of coolant being a
flow of a
liquid or a two-phase flow that includes a vapor and a liquid; an evaporator
configured to
absorb heat (QABSORBED) from the apparatus, the evaporator comprising an inlet
and
an outlet; a valve (V1) configured to regulate a pressure at or after an
outlet of the
evaporator, the V1 having a control set point set at a first pressure (P1set)
to achieve an
evaporator exit pressure that is the saturation pressure (PH) of the coolant
at a
predetermined exit temperature from the evaporator; and wherein the TPPL is
configured to cool the thermal load with tight control of the temperature of
the coolant
that is cooling the apparatus.
[0017] The VCS is configured to operate at a temperature equal to or lower
than the
temperature of the evaporator in the TPPL.
[0018] The VCS comprises: a low pressure receiver (LPR) configured to store
the
coolant; a condenser configured to release heat (QREJECTED) in order to remove
the
heat (QREJECTED) from the thermal management system and to cool the coolant; a
compressor to force the coolant in vapor form to the condenser; a valve (V2)
having a
control set point set at a second pressure (P2set) to prevent the vapor/liquid
receiver
having a pressure that is higher than a predetermined pressure/temperature
limit (PL)
while also enabling a pressure greater than or equal to the pressure in the
LPR; a
controller configured to control the set points of V1 and V2; wherein the
controller is
configured to set P1set so as to provide a predetermined temperature at the
outlet of
the evaporator and the controller is configured to vary P2set so as to
maintain the
pressure in the vapor/liquid receiver at PL; a recuperator configured to
prevent the
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coolant in liquid form from entering the compressor; an expansion valve
configured to
control the exit pressure of the compressor and to reduce the coolant's
pressure in
order to lower the coolant's temperature; a pump configured to force the
cooled liquid
coolant to flow from the LPR of the VCS to the coolant lines exiting the
evaporator of the
TPPL; wherein the cooled liquid coolant from the VCS is injected into and
combined
with the two-phase flow of coolant in the TPPL to aid in the condensation of
the coolant
in vapor form that is present in the two-phase flow; and a variable speed
pump, or a
variable area nozzle, or both to control the injection flow rate of cold
coolant in order to
keep the vapor/liquid receiver pressure nominally at PL and to replenish
coolant mass in
the vapor/liquid receiver.
[0019] The V1 and V2 are independently selected to be an expansion valve or
a
back pressure regulator.
[0020] The vapor/liquid receiver further comprises a foam or porous
structure
configured to assist in condensing the coolant from a vapor to a liquid.
[0021] The VCS further comprises a second pump; the second pump configured to
remove a portion of the coolant from the LPR, to flow said portion of the
coolant near a
secondary thermal load in order to absorb heat therefrom, and to return the
heated
portion of the coolant to the LPR.
[0022] The LPR further comprises a segmented region wherein a portion of
the
coolant is sequestered.
[0023] The portion of the coolant that is not in the segmented region
(Volume 1) is
first cooled and used in support of steady-state operation of the VCS, while
the
sequestered portion of the coolant (Volume 2) is subsequently cooled after
Volume 1,
and optionally, the coolant is then further chilled to a lower temperature to
provide
thermal energy storage for later use in the VCS.
DRAWINGS
[0024] In order that the disclosure may be well understood, there will now
be
described various forms thereof, given by way of example, reference being made
to the
accompanying drawings, in which:
[0025] Figure 1 is a schematic representation of a conventional two-phase
pump
loop;
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[0026]
Figure 2A is a schematic representation of a two-phase pump loop (TPPL)
formed according to the teachings of the present disclosure;
[0027]
Figure 2B is a plot of a control scheme for the set points (P v lset, P2set)
set for
valves (Vi, V2) in the TPPL of Figure 2A;
[0028]
Figure 3 is a schematic representation of another two-phase pump loop
(TPPL) formed according to the teachings of the present disclosure;
[0029]
Figure 4 is a schematic representation of the TPPL of Figure 3 integrated with
a refrigeration system according to the teachings of the present disclosure;
[0030]
Figure 5A is a schematic representation of a thermal management system
comprising a TPPL and a VCS that utilize the same coolant;
[0031]
Figure 5B is a schematic representation of another thermal management
system comprising a TPPL and VCS that provides additional low temperature
cooling;
and
[0032]
Figure 6 is yet another schematic representation of a thermal management
system configured to utilize the same coolant according to the teachings of
the present
disclosure.
[0033] The
drawings described herein are for illustration purposes only and are not
intended to limit the scope of the present disclosure in any way.
DETAILED DESCRIPTION
[0034]
Variants, examples and preferred embodiments of the invention are described
hereinbelow. The present disclosure generally provides a two-phase pump loop
(TPPL)
for dissipating a thermal load during operation of an apparatus. One benefit
of this
TPPL is that the coolant passing through the device to be cooled remains
essentially
isothermal, because the coolant passes through the device as a two (2)-phase
fluid (i.e.,
a vapor and liquid mixture). The temperature being the saturation temperature
of the
fluid based on the pressure of the fluid. In
most cases, if the coolant
pressure/temperature varies, this doesn't pose a problem. However, in some
situations,
the device to be cooled requires that the coolant temperature be held within a
very tight
tolerance, therefore precise control of the pressure is required for the two-
phase fluid In
some situations two independent heat loads operating at different temperatures
is
required and therefore would traditionally require two independent TPPL's to
establish
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the different coolant temperatures and/or pressures. This approach requires a
large
amount of space and weight for the existence of redundant systems.
[0035] The following description is merely exemplary in nature and is in no
way
intended to limit the present disclosure or its application or uses. For
example, the
TPPL made and used according to the teachings contained herein is described
throughout the present disclosure in conjunction with cooling a high-energy
laser (HEL)
in order to more fully illustrate the composition and the use thereof. The
incorporation
and use of such a TPPL in other industrial and military applications that may
include any
apparatus, device, or combination of apparatuses or devices that consume
electricity
and may benefit from cooling and/or heating are contemplated to be within the
scope of
the present disclosure. Several examples of such an apparatus or device
includes,
without limitation, solid state electronics, a light-emitting diode (LED), an
analog circuit,
a digital circuit, a computer, a server, a server farm, a data center, a
hoteling circuit
such as vehicle electronics, a vehicle, an aircraft, a directed-energy weapon,
a laser, a
plasma weapon, a railgun, a microwave generator, a pulse-powered device, a
satellite
uplink, an electric motor generator, an electric device, or the like.
[0036] For the purpose of this disclosure, the terms "valve", "expansion
valve",
"pressure reducing valve", and "back pressure regulator" or "BPR" may be used
interchangeably in the description of a component in the two-phase pump loop
(TPPL)
and are intended to provide substantially similar or the same performance. The
term
"valves" is intended to indicate a plurality of valves in which each valve is
independently
selected to be an expansion valve, pressure reducing valve, or a back pressure
regulator.
[0037] For the purpose of this disclosure, the terms "about" and
"substantially" are
used herein with respect to measurable values and ranges due to expected
variations
known to those skilled in the art (e.g., limitations and variability in
measurements).
[0038] For the purpose of this disclosure, the terms "at least one" and
"one or more
of' an element are used interchangeably and may have the same meaning. These
terms, which refer to the inclusion of a single element or a plurality of the
elements, may
also be represented by the suffix "(s)"at the end of the element. For example,
"at least
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one source", "one or more sources", and "source(s)" may be used
interchangeably and
are intended to have the same meaning.
[0039] For the purpose of this disclosure, the term "tight" temperature
control
describes controlling a temperature condition with minimal variation, such as
5 C;
alternatively, 3 C; alternatively, 1 C; alternatively, 0.5 C. When
desirable, this
control over the variation in temperature may also be expressed as a
percentage of the
measured temperature. For example, as the measured temperature is controlled
to be
within 10%; alternatively, 5%; alternatively, 3%; alternatively, 1%.
[0040] For purposes of promoting an understanding of the principles of the
present
disclosure, reference will now be made to various embodiments illustrated in
the
drawings, and specific language will be used to describe the same. It should
be
understood that throughout the description, corresponding reference numerals
indicate
like or corresponding parts and features. One skilled in the art will further
understand
that any properties reported herein represent properties that are routinely
measured and
may be obtained by multiple different methods. The methods described herein
represent one such method and other methods may be utilized without exceeding
the
scope of the present disclosure.
[0041] No limitation of the scope of the present disclosure is intended by
the
illustration and description of certain embodiments herein. In addition, any
alterations
and/or modifications of the illustrated and/or described embodiment(s) are
contemplated
as being within the scope of the present disclosure. Further, any other
applications of
the principles of the present disclosure, as illustrated and/or described
herein, as would
normally occur to one skilled in the art to which the disclosure pertains, are
contemplated as being within the scope thereof.
[0042] Referring to Figure 1, the challenge for maintaining the
temperature/pressure
in a closed two-phase pump loop system. The system receives heat in the
evaporator
on the left and rejects the heat from a condenser on the right. In this
conventional two-
phase pump loop, the pressure of the system will vary depending on heat loads.
One
can choose to design the system to have the proper coolant mass/charge, such
that at
peak heat load and steady state operation, the fluid entering the heat load is
at the
proper pressure and temperature. However, if the heat load were to be suddenly
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reduced, the condenser will for a while reject more heat than the evaporator
is receiving
from the heat load. In this condition, the overall system temperature/pressure
will begin
to fall. This will result in the liquid in the receiver getting colder. If the
heat added and
removed aren't balanced, the temperature and pressure in the loop will change
and
therefore, the temperature of the coolant entering the evaporator will not
meet the
narrow temperature requirement. A heat load imbalance is expected to occur due
to
heat loads that are highly transient. One could vary the amount of heat
removed from
the condenser; however, most control schemes are expected to be relatively
slow in
responding relative to the rate of change in the load in the evaporator.
[0043] The
features associated with the concept of the present disclosure lie in the
controls used to maintain the temperature of the coolant entering the load
evaporator to
a tight temperature window, by controlling the vapor/liquid receiver pressure
and
evaporator exit pressure. An additional feature is the optional integration of
one or more
Vapor Cycle Systems (VCS) with the TPPL. A primary VCS has control features to
quickly restore high cooling capacity after the VCS has been placed in a low
power
consumption status. A secondary VCS has the ability to provide cooling at a
different
temperature/pressure and manage low power loads. In addition, concepts are
provided
within the present disclosure that minimize the electrical power consumption
required to
run the system.
[0044]
Referring now to Figure 2A, one proposed embodiment for a TPPL 1
designed according to the teachings of the present disclosure is provided.
This concept
assumes that there is some heat sink for the condenser 20a to reject heat that
is
sufficiently cold and the fluid in the evaporator 5 doesn't become too hot.
This concept
uses two valves (Vi, V2) 25, 30, e.g., electronic expansion valves or back
pressure
regulators, to manage temperature to the load evaporator 5. The Vi 25 is
designed to
limit the maximum pressure at the upstream side of the device. If the pressure
is below
the set point 1 set, (P
pressure, the Vi 25 blocks flow. As the pressure rises above the set
x.
point, the Vi 25 begins to pass flow so that the pressure does not rise above
the set
point.
[0045] One
skilled in the art will understand that Vi 25 may be located after the
condenser 20a as shown in Figure 2A, or if enhanced temperature control is
desired,
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the Vi 25 may be located prior to the condenser 20a without exceeding the
scope of the
present disclosure. In addition, although back pressure regulators are
described
throughout the present disclosure, one skilled in the art will understand that
the
substitution of the back pressure regulators with other types of pressure
reducing valves
are contemplated to be within the scope of the present disclosure.
[0046] In
this disclosure, when a thermal storage material is not present (i.e., a
phase change material or a highly chilled coolant), it is assumed that the
maximum heat
(QREJECTED) rejection capacity at the condenser 20a is always greater than or
equal to
the heat (QABsoRBED) being absorbed in the evaporator 5, when averaged over a
short
time period. One skilled in the art will understand that if a large heat load
is absorbed in
the evaporator at a specific time, then QABSORBED may be temporarily greater
than
QREJECTED at that specific time. In this design, the Vi 25 has a pressure set
point (P 1set)
such that the pressure at or after the exit of the load evaporator 5 is the
saturation
pressure (PH) that is required to give the proper coolant temperature in the
load
evaporator 5. In other words, P1set is set to achieve an evaporator exit
pressure that is
the saturation pressure (PH) of the coolant 3 at a predetermined or desired
target exit
temperature from the evaporator 5. The set point pressure (P i
expected to be
µ. 1set, .s
slightly lower than the saturation pressure (PH) due to expected pressure
losses in the
line from the load evaporator to the Vi 25 device. However, Vi 25 will not
prevent the
coolant 3 in the vapor/liquid receiver 15 from getting colder than the
temperature that is
required at the inlet to the load evaporator 5. As a result, a second valve
(V2) 30 is also
added to the TPPL 1 described herein.
[0047] The V2 30 manages how much heat QREJECTED is actually pulled from the
TPPL system 1. A flow restriction 35 may be present at or near the outlet of
V2 30,
upstream of V2 30, or anywhere along the flow pathway associated with V2 30.
Reducing the coolant 3 flow to the condenser 20a reduces QREJECTED and returns
heat
to the vapor/liquid receiver 15. This will prevent the vapor/liquid receiver
15 from
becoming excessively cold and thus keeps the fluid going to the load
evaporator 5 at an
acceptable temperature. When desirable, the condenser 20a may be cooled with a
cold
water-fluid mixture (e.g., water-polypropylene glycol mixture, etc.) from a
previously
chilled tank of liquid or it could be cooled with a cold air stream.
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[0048]
Still referring to Figure 2A, the two-phase pump loop (TPPL) 1 generally
comprises, consists of, or consists essentially of a vapor/liquid receiver 15
configured to
store a coolant 3; a pump 10 configured to force the coolant 3 to flow through
lines or
tubes throughout the TPPL 1; an evaporator 5 configured to absorb heat
(QABsoRBED)
from the apparatus, the evaporator 5 comprising an inlet 7 and an outlet 9; a
condenser
20a configured to release heat (QREJECTED) in order to remove the heat
(QREJECTED) from
the TPPL 1; and a valve (Vi) 25 configured to regulate a pressure at an outlet
of the
condenser 20a, the Vi 25 having a control set point at a first pressure (P ) a
valve
µ.
(V2) 30 having a control set point set at a second pressure (P2set); and a
controller
configured to control the set points of Vi and V2.
[0049] The
controller 23 is configured to set P . lset so as to provide a predetermined
pressure at the outlet of the evaporator 5 that is the saturation pressure at
the desired
operating temperature of evaporator 5 and the controller 23 is configured to
vary
P2set
so as to maintain the pressure in the vapor/liquid receiver 15 at PL. The
P2set is set to
prevent the vapor/liquid receiver pressure from going to a
pressure/temperature that is
lower than a predetermined value. The lset .S P i
less than saturation pressure (PH) of the
.
coolant 3 at the outlet 9 of the evaporator 5; while the P2set is used to keep
low pressure
(PL) within an acceptable pressure range. In other words, the controller 23
defines
values for P . lset and P2set, such that the PH and PL are achievable within
an established
or predetermined tolerance.
[0050] The
controller 23 may be any device that performs logic operations. The
controller 23 may be in communication with a memory (not shown). Alternatively
or in
addition, the controller 23 may be in communication with multiple components
within the
TPPL 1. The controller 23 may include a general processor, a central
processing unit, a
server device, an application specific integrated circuit (ASIC), a digital
signal
processor, a field programmable gate array (FPGA), a digital circuit, an
analog circuit, a
microcontroller, any other type of processor, or any combination thereof. The
controller
23 may include one or more elements operable to execute computer executable
instructions or computer code embodied in the memory.
[0051] The
memory may be any device for storing and retrieving data or any
combination thereof. The memory may include non-volatile and/or volatile
memory,
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such as a random access memory (RAM), a read-only memory (ROM), an erasable
programmable read-only memory (EPROM), or flash memory. Alternatively or in
addition, the memory may include an optical, magnetic (hard-drive) or any
other form of
data storage device.
[0052] In general, the TPPL 1 is configured to cool the thermal load with
tight control
of the temperature of the coolant 3 that is cooling the apparatus. The control
set point
of V2 25 is varied to balance the heat (QREJECTED) removed from coolant 3 at
the
condenser 20a with the heat (QABsoRBED) absorbed by the coolant 3 at the
evaporator 5.
For the purpose of this disclosure, the phrase "to balance the heat
(QREJECTED) with the
heat (QABsoRBED)" refers to the heat (QREJECTED) being equal to the SUM of the
heat
(QABsoRBED) plus any other heat additions or losses encountered during the
operation of
the system. These other heat additions or losses may occur, without
limitation, through
the operation of compressors, pumps, and other system components. This balance
is
achieved by reducing the amount of coolant 3 that gets passed through the
condenser
20a. The QREJECTED released from the coolant 3 at the condenser 20a is at
least equal to
the QABSORBED absorbed by the coolant 3 at the evaporator 5. In other words,
Vi 25 is
used to set the exit pressure of the load 5. V2 30 is used to control the
pressure in the
vapour/liquid receiver 15. It is assumed that the maximum cooling capacity of
the
condenser 20a is always greater than the heat entering the evaporator 5 over a
short
period of time. However, the condenser 20a should not remove more heat than is
being
put into the system at the load evaporator 5. Therefore, when desirable or
necessary
the cooling performed at the condenser 20a may be reduced. This reduction is
achieved by not sending all of the coolant 3 to the condenser 20a by lowering
the P . 2set
so that some of the coolant 3 is passed through V2 30. In the extreme, if no
heat is
being added to the evaporator 5, almost all of the coolant 3 would be passed
through V2
30. In this way, the pressure and/or temperature in the vapor/liquid receiver
15 is
managed so that the receiver 15 is not overcooled. This will assure that the
temperature of the coolant 3 entering load evaporator 5 doesn't get too cold
[0053] The coolant 3 in the TPPL 5 may be any substance suitable for use in
a two-
phase pump loop (TPPL) 5. In other words, the coolant 3 may be any substance
suitable for use in a refrigeration system or that experiences a phase change.
Several
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examples of a coolant 3 may include, without limitation, a chlorofluorocarbon
(CFC), a
hydrochlorofluorocarbon (HCFC), a hydrofluorocarbon (HFC), difluoromethane,
difluoroethane, ammonia, water/ammonia mixture, or a combination thereof.
[0054] The outlet of the vapor-liquid receiver 15 includes a means of
creating a
pressure rise. More specifically, a pump 10 is located approximate to the exit
of the
vapor/liquid receiver 15 in order to create flow of the coolant 3 to the load
evaporator 5.
The pump 10 should draw liquid coolant 3 from the vapor/liquid receiver 15.
[0055] The vapor-liquid receiver 15 may include any device configured to
separate a
vapor-liquid mixture into vapor and liquid portions. The vapor-liquid receiver
15 may be
a vessel in which gravity causes the liquid portion to settle to a bottom
portion of the
vessel and the vapor portion to rise to a top portion of the vessel.
[0056] One skilled in the art will understand that the evaporator 5 used in
conjunction
with the TPPL 1 may be made smaller by selecting appropriate heat exchanger
core
designs for its construction without exceeding the scope of the present
disclosure.
More specifically, the important features of this evaporator 5 include the
ability to
transfer heat, the evacuation of any evaporated liquid, and the containment of
pressure.
A diffusion-bonded structure, such as applied to the design and construction
of turbine
airfoils may be used to form the evaporator 5. A diffusion-bonded structure
includes
complex heat transfer and fluid flow passages. The rules, tools, and
manufacturing
techniques employed in designing actively cooled turbines directly applies to
the
problem of providing for the cooling of an apparatus ¨ with the addition of
two-phase
heat transfer and pressure drop calculations.
[0057] Referring now to Figures 2A and 2B, in the case when the heat load
at the
evaporator 5 suddenly decreases, the fluid exiting Vi 25 will be over-cooled.
This will
result in the receiver becoming colder, but also in the pressure in the
vapor/liquid
receiver 15 beginning to fall. As the pressure begins to fall, the V2 30 will
have its set
point (P2set) reduced to begin to allow two-phase flow to pass through it. As
a result, the
flow rate through the condenser 20a will be reduced and the amount of heat
(QREJECTED)
being removed from the condenser 20a will decrease. Furthermore, the fluid
passing
through V2 30 will have some of the heat from the evaporator 5 and as a
result, will
13
CA 3045263 2019-06-05
begin to increase the temperature of the vapor/liquid receiver 15 and begin to
restore
the temperature closer to the target temperature of coolant 3.
[0058] The TPPL 1 as shown in Figures 2A and 2B may be built with existing
commercial off-the-shelf valves, e.g., back pressure regulators. The valves
are very
good at maintaining an upstream pressure, even as the fluid passing through it
can vary
in quality (e.g., ratio of vapor flow to total mass flow). Furthermore, the
design can have
the pressure set point P2set changed very quickly, i.e., on the order of about
100
milliseconds. Therefore, a controller 23 can determine the proper pressure set
point for
V2 25 as a function of the pressure in the vapor/liquid receiver 15. As the
pressure in
the vapor/liquid receiver 15 falls, the V2 30 set point can be lowered below
Vi 25 to
begin to pass more of the fluid through V2 30. A small downstream or upstream
flow
restriction 35 may be necessary to help with stability of the system.
[0059] The controller 23 sets Vi 25 at a set point (P lset) to provide the
desired
temperature at the exit of the evaporator 5. The P . lset may not match the
evaporator 5
exit pressure (PH) due to pressure losses. The pressure (PL) in the
vapor/liquid receiver
15 is monitored to determine if the receiver 15 is getting too cold. The P2set
is varied to
maintain PL. As PL decreases due to excess cooling at QREJECTED, more flow
passes
through V2 30 and therefore, QREJECTED is lowered. Thus, the two valves, Vi 25
and V2
30, balance the heat QREJECTED removed from the coolant 3 at the condenser 20a
with
the heat QABSORBED absorbed by the coolant 3 at the evaporator 5 plus any
other heat
additions or losses encountered during the operation of the system.
[0060] An alternative design may be to use a pressure reducing valve in
place of a
back pressure regulator at V2 30. In this case, the pressure reducing valve
will remain
closed until the pressure in the vapor/liquid receiver 15 falls below a set
value, which
may reduce the need to actively control the set point pressure in the V2 30
location.
Other types of valves could also be considered based on their ability to
control flow
rates in order to control pressure of the vapor/liquid receiver 15 and
evaporator exit 9.
[0061] Referring now to Figure 3, the TPPL 1 may be modified to minimize
challenges associated with two-phase flow. In this TPPL 1 design, the fluid
that exits
from the load evaporator has the liquid and vapor separated. A liquid
separator 40 is
placed downstream of the load evaporator 5 and is in fluid communication with
the
14
CA 3045263 2019-06-05
outlet of evaporator 5. This will provide a more uniform quality to the flow
of coolant 3 to
V2 30. This flow of coolant 3 to V2 30 need not be pure vapor, but a very high
quality of
flow will enable a more consistent mass flow rate through V2 30 for a given
valve
opening and pressure difference across the valve. This would enable the use of
a wider
variety of valves to replace V2 30. It is not critical that all the liquid be
separated, but
only a significant portion.
[0062] Still referring to Figure 3, the liquid separator 40 is configured
to return all or a
portion of the separated liquid coolant 3 through a liquid return valve 45 to
the
vapor/liquid receiver 15. Alternatively, about 99% to 100% of the liquid
coolant 3 is
returned. The pressure difference between the tanks will drive the liquid
flow. A sensor
could be used to measure the level of liquid in the separator in order to
control the flow
through the liquid return valve and then use the liquid control valve 45 to
manage the
height of that liquid. When desirable, V2 30 could be replaced with a pressure-
reducing
valve without exceeding the scope of the present disclosure when the flow of
the
coolant 3 to V2 30 is nearly all vapor and the pressure-reducing valve doesn't
exhibit too
large of a variation in pressure drop versus flow rate.
[0063] When desirable, the liquid separator 40 may use centrifugal force to
drive the
liquid portion towards an outer edge of the vessel for removal and the vapor
portion may
migrate towards a center region of the vessel. In some examples, the liquid
separator
40 may include a level sensor mechanism that monitors a level of the liquid in
the
vessel.
[0064] Referring now to Figure 4, an embodiment is presented that includes
the use
of a refrigeration system that provides cooling in the condenser 20a of the
TPPL 1 to
ensure a sufficiently cold heat sink on days when ambient conditions are
higher than the
required temperature that is entering the load evaporator 5. For example, the
TPPL 1
may be integrated with a vapor cycle system (VCS) 50 in which the VCS 50 is
configured to remove heat from the TPPL 1 when the temperature of the coolant
3
flowing through the inlet of the evaporator 5 is about ambient temperature or
substantially less than ambient temperature. In this case, the term "about"
ambient
temperature includes an evaporator inlet temperature that is slightly greater
than
CA 3045263 2019-06-05
ambient temperature; alternatively, 5 C of ambient temperature;
alternatively, 2.5 C;
alternatively, 1 C; alternatively, 0.5 C.
[0065] In this embodiment, the TPPL 1 behaves the same as the prior
embodiment
shown in Figures 2A and 3. A challenge in this system is how to manage the
condition
when the heat load in the load evaporator becomes very low. In this case, when
the
heat load on the VCS 50 becomes very low, it may be difficult to have the VCS
50 at
low cooling capacities and to then to rapidly provide high levels of cooling.
Options for
quickly recovering high cooling capacity after operating at lower heat loads
include the
incorporation of one of a hot gas bypass loop or reducing the pressure drop
across an
expansion valve into the VCS 50.
[0066] Referring now to Figure 5A, the TPPL 1 may be incorporated into a
thermal
management system 53 in order to dissipate a thermal load during operation of
an
apparatus. The thermal management system 53 may comprise the two-phase pump
loop (TPPL) 1 as previously described and further defined herein, and a
primary vapor
cycle system (p-VCS) 50a that are configured to use the same coolant 3 and to
be in
fluid communication through a vapor/liquid receiver 15.
[0067] This design eliminates the need for the condenser/evaporator
component in
Figure 4, addresses low load operational concerns, and reduces the overall
system
weight and size. In this configuration, a third valve V3 70 is added to
function as an
expansion valve in the VCS 50A. The set point (P3set) of V3 70 is set to
maintain a
predetermined pressure at an exit of the compressor 60a. The V3 70 set point
(P3set)
pressure is increased in order to allow the compressor 60a to increase the
coolant 3
pressure and therefore temperature, to be able to reject heat from the
condenser 20b to
the available heat sink (e.g. air) and therefore to provide cooling to the
coolant 3.
[0068] Again, it is important to maintain the vapor/liquid receiver 15
pressure and
temperature to satisfy the inlet temperature requirement to the load
evaporator 5. In
this case, a line passes from the compressor 60a exit to the vapor/liquid
receiver 15. If
the pressure begins to fall in the vapor/liquid receiver 15, the V2 30 set
point pressure
may be reduced to be less than the V3 70 set point pressure. In so doing, less
coolant 3
is passed through condenser 20b and overcooling of the vapor/liquid receiver
15 is
16
CA 3045263 2019-06-05
avoided. It is possible that V370 and V2 30 could also use conventional
electronically
controlled expansion valves.
[0069]
Typically, a coarse cooling capacity adjustment may be achieved by slowing
the compressor 20b and the fans for condenser air heat sink. However, using
these
approaches may prevent the VCS 50a from rapidly ramping up to provide
sufficient
cooling capacity in the event of a sudden load increase. In the architecture
shown in
Figure 5A, the pressure set points for V2 30 and V3 70 may be varied to manage
cooling
capacity. Assuming initially that P . 2set P3set, the set point pressure on V3
70 may be
reduced to lower the power consumption in the compressor 20b and the cooling
provided from the VCS 50a. If the volume between the compressor 60a and the
valves
V3, V2 is sufficiently small, the cooling capacity of the VCS 50a can be
rapidly restored
by increasing the V3 set point pressure (P3set).
[0070] In
order to control the pressure and/or temperature in the vapor/liquid
receiver 15 and further reduce cooling from condenser 20b, the pressure set
point in V2
30 may be varied to be slightly below the set point of V3 70. This will result
in less
coolant 3 being cooled as it is passing through the condenser 20b. Also shown
in
Figure 5A are recuperators 65a. 65b for superheat management of the flow
entering the
compressor 20b. The fluid exiting the vapor/liquid receiver 15 and flowing to
the
compressor 20b will be at saturated conditions and may also have some
entrained
liquid. The recuperators 65a, 65b would add heat and avoid passing liquid to
the
compressor 20b. On the V2 30 leg, during a turn-down operation, a more
conventional
expansion valve could be used.
[0071]
Still referring to Figure 5A, the TPPL 1 generally comprises: the vapor/liquid
receiver 15 configured to store the coolant 3; a pump 10 configured to force
the coolant
3 to flow through lines or tubes throughout the TPPL 1; an evaporator 5 having
an inlet
7 and an outlet 9 that is configured to absorb heat (QABsoRBED) from the
apparatus; a
valve (Vi) 25 having a control set point set at a first pressure (Plset) .0 t
establish the
proper pressure at PH measured at the outlet 9 of the evaporator 5, the P lset
being less
than a saturation pressure (PH) of the coolant 3
[0072]
Still referring to Figure 5A, the p-VCS 50A generally comprises: the
vapor/liquid receiver 15 configured to store the coolant 3; a condenser 20b
configured
17
CA 3045263 2019-06-05
SO that the coolant 3 releases heat (QREJECTED) in order to remove heat
(QREJECTED) from
the thermal management system 53; a valve (V2) 30 having a control set point
set at a
second pressure (P2set), the P2set being set higher or lower than P3set to
control the
amount of flow through condenser 20b; a compressor 60a; a valve (V3) 70
configured to
act as an expansion valve; the V3 70 having a control set point (P3set) set to
maintain a
predetermined pressure (Pcmp) at the outlet of the compressor 20b; one or more
recuperators 65a, 65b configured with condenser exit flow or hot bypass flow
to prevent
any coolant 3 in liquid form from entering the compressor 60a; and a
controller 23
configured to control the set points of V1, V2, and V3. The controller 23 is
configured to
set Piset in order to provide a predetermined temperature at the outlet of the
evaporator
and the controller 23 is configured to vary
P2set and P3set in order to maintain the
proper amount of cooling in order to maintain the pressure in the vapor/liquid
receiver
at PL. The V2 is configured to allow a portion of the coolant 3 exiting the
compressor
60a to flow back into the vapor/liquid receiver 15 in order to prevent
overcooling of the
vapor/liquid receiver while allowing the compressor to continue to run.
[0073] The control set points of V2 and V3 are variable in order to balance
the heat
(QREJECTED) removed from the coolant 3 at the condenser with the heat
(QABsoRBED)
absorbed by the coolant 3 at the evaporator. More specifically, the heat
(QREJECTED) is
equal to the sum of the heat (QABsoRBED) plus any other heat additions or
losses
encountered during the operation of the system. These other heat additions or
losses
may occur, without limitation, through the operation of compressors, pumps,
and other
system components. One skilled in the art will understand that sensors may be
utilized
to measure and monitor the pressure and/or temperature at or near the outlet
of the
evaporator and in the vapor/liquid receiver without exceeding the scope of the
present
disclosure. Figure 5A provides a system with greater operability, and reduces
the
overall system size and weight since the VCS 50A has the same working fluid as
the
TPPL 1.
[0074] Referring now to Figure 5B another concept is illustrated for
providing
additional cooling for a low power and/or lower temperature heat load 93. In
this case,
the p-VCS 50a may comprise a second compressor 60b located parallel to the
compressor 60a in order to minimize power draw. This lower power, lower
temperature
18
CA 3045263 2019-06-05
cooling may also be achieved by incorporating a secondary vapor cycle system
(s-VCS)
80. The original, high power VCS is called the primary vapor cycle system (p-
VCS)
50a.
[0075] The s-VCS 80 generally comprises a phase change material (PCM)
located in
an evaporator/condenser (PCM/Ev/Cnd) 90, the PCM providing thermal energy
storage
by absorbing heat until the p-VSC 50a is operational; an accumulator 83; a
third
compressor 85 configured to force a portion of the coolant 3 to flow to the
vapor/liquid
receiver 15; and a plurality of valves 99A-99D; wherein at least one valve 99A
is
configured to manage the use of the PCM/Ev/Cnd 90 and the other valves 99B-99D
are
configured to allow the s-VCS 80 to share the use of the condenser 20b located
in the
p-VCS 50a or to allow a portion of the coolant 3 to flow to the vapor/liquid
receiver 15.
[0076] The PCM may be used when the heat load QABSORBED is greater than the
heat
rejection capacity of the system at a given point in time. This could be the
case when
no compressors are running or only the secondary s-VCS 80 is operational. The
plurality of valves 99A-99D are used when the third compressor 85 is operating
to either
send coolant 3 to the vapor/liquid receiver 15 when the p-VCS 50a is
operational or to
send the coolant 3 to the condenser 20b, and then on to the receiver 15 when
the p-
VCS 50a is not operating.
[0077] The s-VCS 80 may also comprise an expansion valve 95 that is in
fluid
communication with the outlet of the vapor/liquid receiver 15. This expansion
valve 95
is to pass liquid coolant 3. A feedback loop established between the outlet of
the
PCM/Ev/Cnd 90 and the expansion valve 95 is configured to maintain a superheat
condition at the inlet of compressor 85. The controller 23 may be used to
control the
expansion valve such that only vapor enters the third compressor.
[0078] The compressors 60a, 60b, 85 may be any mechanical device that
increases
a pressure of a gas by reducing the volume of the gas. The compressors may be
used
in conjunction with an oil receiver when desirable. Examples of a compressor
60a, 60b,
85 may include but not be limited to any gas compressor, such as a positive
displacement compressor, a dynamic compressor, a rotary compressor, a
reciprocating
compressor, a centrifugal compressor, an axial compressor, and/or any
combination
thereof.
19
CA 3045263 2019-06-05
[0079] The thermal management system 53 described in Figure 5B provides
thermal
energy storage and the ability to more quickly bring high cooling capability
on-line. The
secondary VCS 80 expands liquid contained in the vapor/liquid receiver 15. The
expanded coolant 3 cools the low temperature heat load 93 and also provides
cooling to
the load evaporator 5 when that heat load is very small or the primary VCS 50a
is not
operational. When there is a thermal load that requires cooling at a lower
temperature
than QABSORBED, and QABSORBED is sufficiently small, the secondary VCS may be
used.
In this low load condition, valve 99A bypasses the phase change material
(PCM). The
PCM/Ev/Cnd component 90 is cooled to a temperature below the exit temperature
of
the load evaporator 5 (by fluid that is expanded by the expansion valve 95)
and the
phase change material (PCM) is typically operating in the solid state in order
to be
ready to absorb a large heat load from evaporator 5, should it occur. If the
load
evaporator 5 suddenly has a very high heat load, valve 99A routes coolant 3
through
the PCM and the PCM/Ev/Cnd 90 absorbs this heat until the primary VCS system
50a
can come on-line. Once the primary VCS 50a begins to chill, a valve 99a
switches in
order to bypass the PCM/Ev/Cnd 90. This allows any un-melted PCM to remain in
solid
form and to allow the melted PCM to be refrozen by fluid passing through
expansion
valve 95.
[0080] The
PCM/Ev/Cnd 90 can also allow periods for the compressor 60a, 60b, 85
to be shut-off in order to avoid operation under very poor efficiency
conditions. The
PCM/Ev/Cnd 90 can condense the vapor from the load evaporator 5 during this
time
period. If the melt temperature is suitably chosen, it may also extend the
period of time
that the coolant 3 can be expanded for cooling the low temperature heat load
93 while
compressor 85 is turned off and thereby allow a smaller accumulator 83 or
extend the
period of time that compressor 20b can be turned off. During this period, with
the
compressor turned off, the vapor exiting the low temperature heat load 93,
would be
condensed in the PCM/Ev/Cnd 90. For this to work, the lower temperature low
heat
load 93 would need to be able to have its operating temperature rise above the
melting
point of the PCM.
[0081] One
skilled in the art will understand that the temperature requirement for the
low temperature heat load 93 is a range of temperatures. The melt temperature
of the
CA 3045263 2019-06-05
PCM in the PCM/Ev/Cnd 90 could be set between the high and low temperature
limit
93. Thus, when compressor 85 is running, the low temperature load 93 could be
operating to the low end of this temperature tolerance, thus freezing the PCM.
When
the compressor 85 is turned off, the coolant 3 could still be expanded through
the
expansion valve 95. However, as this occurs the pressure in the low
temperature loop
will rise, increasing the operating temperature. However, once the temperature
exceeds
the melt temperature of the PCM in the PCM/Ev/Cnd 90, a significant amount of
heat
can be absorbed by the PCM; and thus, limit the temperature of the vapor in
the low
temperature loop until most or all of the phase change material melts. This
absorption
of heat would condense the vapor to liquid, which is significantly more dense
than the
vapor. This would enable the use of a smaller accumulator 83.
[0082] Still referring to Figure 5B, under standby conditions when
compressor 85 is
operational and compressors 60a, 60b are not operational, valve 99b would be
open
while valves 99c and 99d would be closed in order to use the large condenser
area
available in the primary VCS 50a and thereby reduce compressor pressure ratio
requirements. Under high load conditions, when compressors 60a and possibly
60b are
operational, as well as compressor 85, valve 99b would be closed, while vales
99c and
99d are open. In this case, the third compressor 85 sends coolant to the
vapor/liquid
receiver 15. Under a high load condition, multiple compressors 60a, 60b are
used to
manage cooling capacity. If the heat load is reduced to relatively low, one of
the
compressors (60a or 60b) may be turned off in order to operate closer to peak
efficiency
and to reduce system power requirements.
[0083] In this concept, all compressors 60a, 60b, 85 could be driven by
battery
supplied power so that the compressors can quickly be ramped up to produce
cooling
while waiting for the prime mover generator power supply to come on-line. This
will
minimize the amount of PCM required. Also, multiple primary compressors 60a,
60b
are implemented in order to reduce power requirements for the compressor(s)
when the
heat load to be cooled is much less than the maximum cooling capacity of the
system.
[0084] Referring now to Figure 6, another means to provide cooling of the
TPPL 1
during start-up conditions would be to use a chilled coolant 3. If using
chilled coolant 3,
one could utilize the latent heat of the coolant 3. Using latent heat would
reduce how
21
CA 3045263 2019-06-05
cold the coolant 3 must be cooled in order for it to function as TES (i.e. the
coolant
would not need to be chilled to a very low temperature) This would enable a
lower
pressure ratio on the VCS compressor and therefore enable more efficient
cooling of
the coolant. However, when the liquid coolant 3 is vaporized, there is a very
large
increase in the volume of the vapor, relative to the liquid state of the
coolant 3. In a
space-constrained design, this may not be practical to accommodate.
[0085] An alternative would be to chill the coolant 3 to a temperature that
is colder
than the required steady state operating temperature of the coolant 3 and to
also
include more of the coolant 3 in liquid form than is necessary for steady
state operation
of the VCS 50a. In this way, the heat energy would be absorbed in the liquid
coolant 3
and the temperature of the large quantity of liquid coolant 3 would rise very
slowly.
Therefore, the vapor pressure in the tank would rise much more slowly. This is
expected to provide a smaller tank for the liquid coolant 3.
[0086] In using this approach, the amount of coolant 3 in the VCS 50a would
need to
be larger than the amount required to support steady state operation. This
additional
mass would make it more difficult to perform the initial chill down of the VCS
50a,
because of the large amount thermal energy that must be removed from the
coolant 3.
Therefore, it may be necessary to sequester the additional coolant that is
needed for
TES into a separate tank. This would allow the VCS 50a and TPPL 1 to more
quickly
chill down to the required operating temperatures. Once the steady state
operating
condition is reached, the VCS 50a could continue with the chilling of the
sequestered
coolant to the operating temperature and then to continue chilling the full
coolant charge
to a temperature necessary to provide sufficient thermal storage capacity. For
example,
the portion of the coolant that is not in the segmented region (Volume 1) may
be first
cooled and used in support of steady-state operation of the VCS, while the
sequestered
portion of the coolant (Volume 2) is subsequently cooled after Volume 1, and
then the
coolant is further chilled to a lower temperature to provide thermal energy
storage for
later use in the VCS. This quantity of TES may be related to the amount of
storage
necessary to support the operation of the TPPL 1 before the VCS system 50a is
able to
reach full cooling capacity. To prolong the duration of the chilled fluid, the
system
22
CA 3045263 2019-06-05
should be thermally insulated to prevent heat from entering the TES and
increasing its
temperature.
[0087] Still referring to Figure 6, an additional example of a thermal
management
system 53 is provided for dissipating a thermal load during operation of an
apparatus.
This thermal management system 53 comprises a two-phase pump loop (TPPL) 1 and
a vapor cycle system (VCS) 50 configured to use the same coolant (Figure 6).
As
shown in Figure 4, a temperature difference must exist in the heat exchanger
or
condenser 20a in order to drive heat from the hotter fluid 3 to the colder
fluid in the
VSC. As shown in Figure 6, the TPPL 1 in the thermal management system 53 is
configured to cool the thermal load with tight control of the temperature of
the coolant 3
that is cooling the apparatus. The TPPL 1 generally , includes a coolant 3, a
vapor/liquid receiver 15, a pump 10, an evaporator 5, and a valve (Vi) 25 as
previously
described above and further defined herein.
[0088] Referring again to Figure 6 an alternative concept is presented
wherein the
TPPL 1 and VCS 50 utilize the same coolant 3. In this case, the vapor from the
TPPL 1
is condensed with the chilled coolant 3b that is injected into the 2-phase
stream 3a of
the TPPL 1 at a predetermined location 201, which represents a nozzle. The
colder
coolant 3b will absorb heat from the vapor, resulting in the vapor condensing.
The VCS
50 is configured to operate at a temperature that is equal to or lower than
the
temperature of the evaporator in the TPPL.
[0089] The VCS 50 generally comprises: a low pressure receiver (LPR) 105
configured to store the coolant 3; a condenser 20b configured to release heat
(QREJECTED) in order to remove the heat (QREJECTED) from the thermal
management
system 53 and to cool the coolant 3b below the temperature of coolant 3a; a
pump 110
configured to force the cooled liquid coolant 3b to flow from the LPR 105 of
the VCS 50
to the flow of coolant 3a that is downstream of evaporator 5 of the TPPL 1; a
recuperator 65 configured to prevent the coolant 3 in liquid form from
entering the
compressor 60a; an expansion valve 67 configured to control the exit pressure
of the
compressor 60a and to reduce the coolant's pressure in order to lower the
coolant's
temperature; and a variable speed pump, or a variable area nozzle, or both to
control
the injection flow rate of cold coolant in order to keep the vapor/liquid
receiver pressure
23
CA 3045263 2019-06-05
nominally at PL and to replenish coolant mass in the vapor/liquid receiver; a
valve (V2)
having a control set point set at a second pressure (P2set) to prevent the
vapor/liquid
receiver having a pressure that is higher than a predetermined
pressure/temperature
limit (PL) while also enabling a pressure greater than or equal to the
pressure in the
LPR; and a controller configured to control the set points of Vi and V2;
wherein the
controller is configured to set P . lset SO as to provide a predetermined
temperature at the
outlet of the evaporator and the controller is configured to vary P . 2set so
as to maintain
the pressure in the vapor/liquid receiver at PL.
[0090] The valve (V2) 30, in concert with the mass injection (as described
below),
seeks to keep the pressure in the vapor/liquid receiver 15 at PL. The valve
(V2) 30
maintains this pressure, by restricting flow to the low pressure receiver
(LPR) in the
VCS 50. If the pressure drops below PL, the valve (V2) 30 closes. Dropping
below this
pressure may happen if the cold coolant is injected too quickly. However, the
valve (V2)
30 is generally open and will pass vapor there through when the pressure in
the LPR
goes above PL.
[0091] The cooled liquid coolant 3b from the VCS 50 is injected into and
combined
with the two phase flow of coolant 3 in the TPPL 1 to aid in the condensation
of the
vapor portion of the coolant 3a that is present in the two-phase flow 3. In
addition, a
valve 30 may be located at the outlet of the vapor/liquid receiver 15 to
prevent the
pressure rising above a predetermined pressure limit set for the TPPL 1.
[0092] When desired, the vapor/liquid receiver 15 of the TPPL 1 further
comprises a
foam or porous structure configured to assist in condensing the coolant 3 from
a vapor
to a liquid. The VCS 50 may also comprise a second pump 115 configured to
remove a
portion of the coolant 3 from the LPR 105, to flow said portion of the coolant
3 to a
secondary thermal load 120 in order to absorb heat therefrom, and to return
the heated
portion of the coolant 3 to the LPR 105. In addition, the LPR 105 may further
comprise
a segmented region 106 wherein a portion of the coolant 3 that provides
thermal energy
storage is sequestered.
[0093] Still referring to Figure 6, in order for this concept to work, it
is important to get
good mixing of the 2-phase flow 3a in the TPPL 1 and the cold injected coolant
3b. One
or all of the following options could be used. First, the cold coolant 3b
could be injected
24
CA 3045263 2019-06-05
directly into the two-phase stream 3a. The cold coolant 3b may be pressurized
by the
pump 110 and then injected into the two-phase stream 3a. The goal is to create
fine
droplets in order to increase the droplet surface area/volume ratio to improve
vapor
condensation. Second, the two-phase mixture (vapor and subcooled liquid) could
encounter a foam or porous barrier. This foam or porous barrier could be made
from
foam metal, sintered beads, strips of material, or the like. The goal is that
the
subcooled coolant 3b would spread out on the large surface area of the foam,
in order
to improve the heat transfer from the vapor to the subcooled liquid. Finally,
any
subcooled liquid drops could then fall into a second foam layer in the
vapor/liquid
receiver 15. In this case, the desire would be that any vapor contained in the
vapor/liquid receiver 15 could infiltrate the foam that is coated with
subcooled liquid and
therefore condense the vapor onto the subcooled liquid/foam surface.
[0094] A
benefit of the concept shown in Figure 6 is that no heat exchanger is
needed for condensing the vapor. Second, the subcooled liquid will reach the
temperature of the vapor, and hence the full TES capability of the cold
coolant will be
utilized. The full utilization of the TES will require less chilled coolant
(smaller LPR) or
not require that the coolant to be cooled to as low of temperature (allows a
lower
compressor pressure ratio) or the ability to reduce the time it takes to chill
the coolant in
the LPR.
[0095] In
order to manage the temperature in the vapor/liquid receiver 15, the
second valve (V2) 30 is used that will pass vapor back to the LPR 105. The
second
valve V2 30 will prevent the LPR 105 from reaching too high of pressure and
thus too
high of temperature. This second valve (V2) 30 may also keep the pressure
greater
than (or equal to) the pressure in the LPR 105. The V2 30 is intended to
maintain
pressure in the receiver at PL. The V2 30 may be opened to keep the pressure
from
getting too high. If the pressure goes below PL, then V2 30 will close in
order to allow
the LPR 105 to repressurize.
[0096]
Over extended periods of time, the amount of vapor to be removed from the
vapor/liquid receiver 15 is equal to the amount of mass injected. The rate of
injection
will be a function of at least QABSORBED and the temperature of the injected
stream 3b.
The amount of cold coolant to be injected may be controlled by the speed of
the pump
CA 3045263 2019-06-05
110 or the amount that nozzle 201 is opened. The speed or nozzle area may be
controlled with the controller 23 as shown in Figure 6.
[0097] A
further description of various structures, elements, and the performance
associated with a TPPL and/or VCS is provided in a co-pending application
entitled
"Thermal Management System Including Two-Phased Pump Loop and Thermal Energy
Storage" filed herewith that claims priority to U.S. Provisional Application
No.
62/656,518 filed April 12, 2018, the entire contents of which are hereby
incorporated by
reference.
[0098]
Within this specification, embodiments have been described in a way which
enables a clear and concise specification to be written, but it is intended
and will be
appreciated that embodiments may be variously combined or separated without
parting
from the invention. For example, it will be appreciated that all preferred
features
described herein are applicable to all aspects of the invention described
herein.
[0099] The
foregoing description of various forms of the invention has been
presented for purposes of illustration and description. It is not intended to
be exhaustive
or to limit the invention to the precise forms disclosed. Numerous
modifications or
variations are possible in light of the above teachings. The forms discussed
were
chosen and described to provide the best illustration of the principles of the
invention
and its practical application to thereby enable one of ordinary skill in the
art to utilize the
invention in various forms and with various modifications as are suited to the
particular
use contemplated. All such modifications and variations are within the scope
of the
invention as determined by the appended claims when interpreted in accordance
with
the breadth to which they are fairly, legally, and equitably entitled.
26
CA 3045263 2019-06-05
