Note: Descriptions are shown in the official language in which they were submitted.
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COLD STORAGE RACK SYSTEM WITH OVERHEAD PCM SUPPORT
BACKGROUND OF THE INVENTION
1. Technical Field:
[0001] The present invention relates in general to refrigeration systems,
which can used, for
example, for the cold storage of perishables.
/. Description of the Related Art:
[0002] The storage and transportation of food perishables is a necessity in
this age of mass
commerce. Many goods and foodstuffs require refrigeration systems to prevent
spoilage or
degradation. If such foodstuffs are not properly maintained at their
appropriate temperature
range, the spoilage or degradation of foodstuffs leads to a reduction in
profits, or worse, the
spread of food borne illnesses. According to a food waste study published in
1997 and
conducted by the USDA's Economic Research Service (ERS), it was estimated that
in 1995
alone, 96 billion pounds of food were lost by retailers, foodservice, and
consumers. Moreover,
dairy products and fresh fruits and vegetables accounted for half of all
retail losses. In the case
of retailers and foodservice outlets, current economies of scale necessitate
the use of large
temperature-controlled storage facilities to preserve the freshness of a large
volume of perishable
goods, usually at a considerably high energy consumption cost. For this
reason, taking measures
to improve the energy efficiency and quality of existing and future
refrigeration systems is
critical.
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SUMMARY OF THE INVENTION
[0003] In one or more embodiments, a cold storage system includes an enclosed
structure having
an opening sealed by a door. A mechanical refrigeration unit maintains an
interior of the
enclosed structure within a selected temperature range. The cold storage
system may further
include within the enclosed structure a rack system having one or more shelves
for supporting
refrigerated goods. The rack system additionally support endothermic phase
change material
(PCM) providing a capacitive cooling effect within the enclosed structure. In
at least some
embodiments, the PCM is contained in a plurality of overhead PCM containers
supported by one
or more support members of the rack system.
[0004] According to one aspect of the above embodiment(s), the plurality of
overhead PCM
containers includes endothermic PCM tubes that are disposed on one or more
horizontal support
members that securely attach to a plurality of vertical supports. The vertical
supports may be
reinforced by a horizontal cross beam bracket. According to another aspect of
the above
embodiment(s), the plurality of adjustable height vertical supports adjusts a
height placement of
the plurality of overhead PCM containers. According to another aspect of the
above
embodiment, additional PCM containers may be supported by the one or more
shelves. For
example, these additional PCM containers can be modularly reconfigurable to
accommodate
various storage shelf configurations. Further, the additional PCM container
may be disposed in a
plurality of under-shelf support brackets attached to the undersides of
adjustable storage shelves
of the cold storage rack. According to another aspect of the above
embodiment(s), the cold
storage system may includes a temperature monitor for controlling the
mechanical refrigeration
unit to maintain ambient temperature in the enclosed structure based upon at
least a temperature
of the endothermic PCM and an ambient temperature. In at least some
implementations, the
temperature monitor includes an outer temperature sensor for measuring a
temperature of
endothermic PCM adjacent to an inner surface of the PCM container, and an
inner temperature
sensor for measuring a temperature of endothermic PCM located at a farthest
distance away from
the inner surface of the PCM container.
[0005] According to one or more other embodiments, a cold storage rack
includes one or more
shelves for supporting refrigerated goods. The cold storage rack includes one
or more support
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members supporting a plurality of overhead PCM containers containing
endothermic PCM that
provides a capacitive cooling effect with a mechanical refrigeration unit
within a cold storage
structure. The rack system may also include additional PCM containers
supported by the one or
more shelves. For example, these additional PCM containers can be disposed in
a plurality of
under-shelf support brackets attached to the undersides of adjustable storage
shelves of the cold
storage rack and may be modularly reconfigurable to accommodate various
storage shelf
configurations.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Figure 1 is a perspective view of an exemplary cold storage system in
accordance with
one embodiment;
[0007] Figure 2A is a partial perspective view of an exemplary cold storage
rack in accordance
with one embodiment;
[0008] Figures 2B-2C depict multiple configurations of PCM containers in
accordance with one
embodiment;
[0009] Figure 3 is a top plan view of several cold storage racks in a modular
configuration;
[0010] Figure 4 is a side elevation view of an exemplary cold storage rack in
accordance with
one embodiment;
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DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENT
[0011] In one or more embodiments, a cold storage system employs endothermic
phase change
material (PCM) within an enclosed, refrigerated chamber in a manner that
leverages the features
of conventional mechanical refrigeration units employing forced-air chilling.
In conjunction
with the "active" heat exchange mode provided by the forced-air mechanical
refrigeration unit, a
bimodal cold storage system as disclosed herein advantageously employs a
"passive" heat
exchange mode in the form of an endothermic PCM container compatibly deployed
within a
refrigerated structure. As utilized herein, a "bimodal" cold storage system
refers to a heat
extraction/absorption system employing passive heat exchange mechanism in the
form of an
endothellnic PCM in conjunction with an active heat exchange mechanism in the
form of a
forced-air mechanical refrigeration unit. The bimodal cold storage system
efficiently addresses
problems and costs associated with conventional refrigerated cold storage
structures, including
uneven cooling of temperature sensitive goods and ice buildup resulting from
excessive
condensation within the cold storage structure. Furtheimore, the bimodal cold
storage system's
cooling mechanism reduces the required active operating time and excessive
cycling of the
mechanical refrigeration unit. Such reduction of active operating time and
cycling of the
mechanical refrigeration unit consequently reduces the overall power (kW) and
energy (kWh)
demands of the cold storage system, reduces repair and maintenance costs of
the mechanical
refrigeration unit, and extends the life the mechanical refrigeration unit.
[0012] As explained in further detail with reference to the figures, the cold
storage system can be
implemented within a refrigerated fixed structure (e.g., a cold storage
cooler, cold storage
freezer, cold storage room or cold storage warehouse) or portable cargo
container or trailer
having a conventional forced-air mechanical refrigeration unit that produces
and directs chilled
air into the interior of the refrigerated structure as required to lower and
then maintain the
temperature within the refrigerated structure at or below a predeteimined
temperature. To
leverage the "active" heat exchange mode provided by the forced-air mechanical
refrigeration
unit, the cold storage system advantageously employs a "passive" heat exchange
mode enabled
by a rack system. The rack system is installed and compatibly deployed inside
the cold storage
structure to support endothermic PCM in various installation configurations.
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[0013] When in active mode, the chilled airflow from the mechanical
refrigeration unit is used to
bring the endothermic PCM to the required phase change or stasis temperature.
In passive mode,
enabled when the endothermic storage material has reached its stasis
temperature, the
mechanical refrigeration unit deactivates, and the activated (i.e.,
capacitively charged)
endotheimic PCM serves as a suspended, non-mechanically driven heat sink for a
passive
theithal convection mechanism wherein a passive convective air current
resulting from natural
thermal circulation is circulated throughout the interior of the refrigerated
structure. The
presence of this passive, endothermic PCM and natural convective air flow
maintains the
reduced internal temperature of the refrigerated structure for an extended
period of time. The
predictability of the passive mode periods enables thel _______________ nal
recharge cycling of the mechanical
refrigeration unit to be synchronized with "off-peak" hours when the cost of
electricity is lower
than during peak demand hours.
[0014] The system as described is also useful in reducing or precluding
excessive moisture
within the refrigerated structure, which can be a significant problem. In
systems relying solely
on mechanical refrigeration units, excess moisture results in the buildup of
ice on the cooling
coils, requiring the unit to be reversed in a defrost cycle wherein the coils
are defrosted. In many
conventional installations, defrosting may be required several times per day
and may in
aggregate take multiple hours per day, resulting in a thermally inefficient
and energy inefficient
process.
[0015] In a preferred embodiment, the refrigerated structure is provided with
additional
insulating elements to reduce outside heat infiltration into the interior of
the cold storage
room/container from UV and radiant heat and convection. In addition, an
exterior of the
structure can be coated with a thermal reflective coating to reduce heat
absorption from UV
radiation. Moreover, panels with high insulation values can be disposed within
or on the walls,
ceiling or floor of the cold storage structure to achieve optimum thermal
storage efficiency.
[0016] With reference now to the figures, wherein like reference numerals
refer to like and
corresponding parts throughout, and in particular with reference to FIG. 1,
there is depicted a
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perspective view showing a bimodal cold storage system 100 in accordance with
a preferred
embodiment. Specifically, FIG. 1 illustrates that bimodal cold storage system
100 includes an
enclosed refrigerated structure 101, which is a generally rectangular
structure having an opening
sealed by a door 102, and a mechanical refrigeration unit 103 mounted to
refrigerated structure
101. To minimize thermal ingress from warmer outside temperatures,
refrigerated structure 101
preferably includes insulated walls and ceilings, and optionally, an insulated
floor. In various
implementations, refrigerated structure 100 can be, for example, a restaurant
walk-in cooler or
freezer, a cold storage warehouse, a cold storage shipping container, a
refrigerated trailer
(reefer), etc.
[0017] The bimodal cold storage system 100 illustrated in FIG. 1 includes, as
one of its thermal
control modalities, a thermostatically controlled mechanical refrigeration
unit 103 that monitors
and regulates the temperature within an interior 104 of refrigerated structure
101 and the
refrigerated contents and endothermic PCM disposed therein. To this end,
mechanical
refrigeration unit 103 employs a conventional evaporator/condenser system that
produces chilled
air and furthermore includes blowers or fans to forcefully discharge chilled,
forced-air current(s)
112 into interior 104 to achieve rapid temperature control or recovery. Such
mechanical
refrigeration systems are well known and widely utilized to store and maintain
goods within
refrigerated structure 101 at reduced temperatures.
The other thermal control modality employed by refrigerated structure 101 is
achieved by
compatibly deploying an endothermic PCM, such as an endothermic phase change
material, in
conjunction with the cycling, forced-air heat extraction mechanism to achieve
substantially
increased thermal extraction and absorption capacity, a more even thermal
gradient distribution,
and a reduced cycling of mechanical refrigeration unit 103. The endothermic
PCM can be
advantageously deployed within various PCM containers (e.g., overhead PCM
tubes 105 and
under-shelf PCM containers 106) supported by a rack system 110 within
refrigerated structure
101. The particular endotheimic PCM chosen is dependent on the desired
temperature to be
maintained within refrigerated structure 101. For example, an endothermic PCM
that reaches
stasis at approximately -10 F (-23 C) is suitable for use in circumstances
where the goods are
to be maintained at or below freezing (i.e., 32 F or 0 C). For goods that
must be chilled but not
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frozen, endothermic PCMs having a higher stasis temperature can be utilized.
Temperature
ranges employed for common perishable goods include, for example, a
temperature range
between 32 F to 55 F (0 C to 13 C) for fruit, vegetables, beer, dairy
products,
pharmaceuticals, and the like, or between -32 F and -20 F (-36 C to -29 C)
for frozen meat,
ice cream, and the like. For food storage applications, the endothermic PCM is
preferably
implemented utilizing a material, such as a water-based or organic-based PCM,
that is non-
hazardous and environmentally friendly.
[0018] Still referring to FIG. 1 and with additional reference to FIG. 2A,
rack system
110,shown in a partial perspective view in FIG. 2A, will now be described.
Rack system 110,
which may be retrofitted within an existing refrigerated structure 101 without
modification of the
existing structure or originally installed in a new refrigerated structure
101, includes at least one
(and possibly multiple) storage shelves 201 for supporting refrigerated goods.
Storage shelf 201
is supported by adjustable height vertical supports 202, which may use, for
example, perforated
nested angled corner vertical supports secured by fasteners (e.g., nuts and
bolts) to permit
configuration (or reconfiguration) to a desired overall rack height. Overhead
endothermic PCM
tubes 105 are disposed on one or more horizontal support members 203, which
are attached
securely to height-adjustable vertical supports 202, for example, by welding,
fasteners, etc.
Vertical supports 202, and thus horizontal support members 203 and PCM tubes
105, are
advantageously height-adjustable to allow optimal height placement of overhead
endothermic
PCM tubes 105. Optimal height placement of overhead endothermic PCM tubes 105
can depend
on a number of factors, such as the maximum height clearance of the interior
volume of
refrigerated structure 101 (FIG. 1), the location of the forced-air flow
ingress of mechanical
refrigeration unit 103 (FIG. 1), the modular arrangement of rack system 110
(FIG. 1), the
loading configuration of the cold storage goods, etc. In addition, it should
be appreciated that
PCM tubes 105 can be arranged with their long axes parallel to, orthogonal to,
or in some other
desired orientation to the forced-air flow path generated by mechanical
refrigeration unit 103.
Achieving the desired orientation of PCM tubes 105 to the forced-air flow path
may also entail
installation of PCM tubes 105 orthogonal to the long axis of rack systems 110
and bridging
multiple rack systems 110.
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[0019] It should be noted that storage shelf 201 and horizontal support member
203 are depicted
as being constructed using heavy duty wire mesh material. However, it should
be appreciated
that the selected material can vary between implementations. For example,
solid surface and/or
perforated surface may alternatively or additionally be employed. Moreover,
other types of
height-adjustable vertical shelf support systems such as telescopic vertical
members or additional
vertical support members can be employed without limiting the spirit and scope
of the invention.
[0020] In addition to supporting perishable goods, storage shelf 201 is
configured to support
under-shelf PCM containers 106 by attachment (e.g., during initial
construction or by
retrofitting) of one or more under-shelf support brackets 205 to an underside
of adjustable,
storage shelf 201. With under-shelf support brackets 205 attached, additional
under-shelf PCM
containers 106 can be slidably installed under storage shelf 201. Although
embodiments having
various materials and dimensions are contemplated, in one example PCM
containers 106 are
formed of high-density polyethylene (HDPE) and have dimensions of 500 mm x 250
mm x 45
mm. PCM containers 106 are preferably sized to be modularly reconfigurable to
accommodate
various storage shelf configurations. For example, FIGs. 2B-2C illustrate that
PCM containers
106 can be arranged in a first orientation as shown in FIG. 2B to fit a narrow
storage shelf 201
(e.g., 18" x 48") or alternatively arranged in a second orientation as shown
in FIG. 2C to fit a
deeper storage shelf 201 (e.g., 24" x 48").
[0021] With reference now to FIG. 3, there is illustrated a top plan view of
an exemplary
embodiment of a cold storage rack arrangement including four cold storage
racks 110 in a 2 x2
split configuration. The depicted arrangement may be suitable, for example,
for a restaurant' s
walk-in cooler or freezer. In the depicted embodiment, overhead PCM tubes 105
are
longitudinally disposed in alignment with the long axis of each cold storage
rack 110 upon
horizontal support members 203 (e.g., wire mesh) attached to adjustable height
vertical supports
202. The quantity and arrangement of PCM tubes 105 disposed on horizontal
support members
203 may vary depending upon the optimal volume and/or velocity of air flow
passing between
PCM tubes 105.
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[0022] In the embodiment of FIG. 3, the stability and rigidity of cold storage
racks 110 is
enhanced by one or more horizontal cross beams 204 coupled between cold
storage racks 110.
Horizontal cross beam(s) 204 preferably link cold storage racks 110 at their
tops in order to
preserve adequate headroom in a walk space 301 between cold storage racks 110.
The width of
walk space 301., which is defined by the length of horizontal cross beam(s)
204, is preferably of
sufficient width to permit convenient access to goods stored on the various
storage shelves 201
on either side of walk space 301. It should be appreciated that a variety of
cold storage rack
arrangements and horizontal cross beam lengths fall within the spirit and
scope of the invention.
[0023] Cold storage racks 110 enable the enclosing refrigerated structure in
which they are
disposed to benefit from the passive cooling provided by PCM tubes 105 (and
optionally under-
shelf PCM containers 106) without requiring any modification of the
refrigerated structure or
penetration of, or attachment to any of its interior surfaces. In some
embodiments, the passive
cooling capacity of the refrigerated structure may optionally be further
augmented by the
attachment of additional PCM containers to one or more of the interior
surfaces of the
refrigerated structure.
[0024] FIG. 4 is a side elevation view of exemplary embodiment of a cold
storage rack 110. In
particular, FIG. 4 shows, via a cutaway view, overhead PCM tubes 105 disposed
on horizontal
support member 203, which is in turn attached securely to adjustable height
vertical supports 202
for optimal height placement of overhead PCM tubes 105. Moreover, ends of
horizontal cross
beam bracket 204 attach to adjustable height vertical supports 202, providing
additional
structural support.
[0025] Structural members of cold storage racks 110, including vertical
supports 202, shelf
supports 400 and lateral braces 402, and may be implemented with bar, angle,
channel, beam,
square tube, round tube, etc. Although other materials may be employed, steel
is presently
preferred for the structural members of cold storage racks 110 due to steel's
relatively low cost
and high strength-to-weight ratio. In at least some embodiments, cold storage
rack 110 may
optionally further incorporate PCM containers (e.g., PCM tubes 404) along or
within one or
more of its structural members to provide additional capacitive cooling
capacity. For structural
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members that do not have a substantially enclosed configuration, PCM
containers may be
secured to the structural members by ties, clamps, brackets or the like. For
structural members
such as tubes and channel having substantially enclosed configurations,
additional attachment of
the PCM containers to the structural members can be omitted.
[0026] With reference now to FIGs. 5A-5B, there is illustrated an exemplary
management and
control system for cold storage system 100 in accordance with one embodiment.
As shown in
FIG. 5A, the exemplary management and control system preferably includes an
electronic
controller 520 communicatively coupled to multiple sensors within refrigerated
structure 101.
These sensors preferably include one or more PCM temperature sensors 502 that
sense a PCM
temperature in one or more PCM containers (e.g., overhead PCM tubes 105 or
under-shelf PCM
containers 106). In one embodiment shown in FIG. 5B, PCM temperature sensors
502 have a
first probe 504 at or near a core region of a PCM tube 105 (or PCM container
106), and a second
probe 506 at or near an outer region of a (possibly different) PCM tube 105
(or PCM container
106). Typically, the PCM temperature detected by probe 504 at the innermost
point of overhead
PCM tube 1.05 (or PCM container 106) lags behind the PCM temperature sensed by
probe 506
near the inner surface of overhead PCM tube 105 (or PCM container 106) as the
PCM changes
phase from latent heat mode to sensible heat mode. Sensing temperature at
multiple locations
within the PCM can thus provide controller 520 a more accurate indication of
the state of the
PCM along its latent-to-sensible phase change curve (and sensible-to-latent
phase change curve),
where the goal of the controller 520 is to prevent complete conversion of the
PCM from its latent
heat mode to its sensible heat mode.
[0027] The exemplary management and control system for cold storage system 100
preferably
additionally includes one or more ambient condition sensors 510 within or
associated with
refrigerated structure 101. For example, ambient condition sensors 510 may
include an ambient
temperature sensor providing temperature data indicative of the temperature of
a representative
location within the interior volume of refrigerated structure 101, as well as
relative humidity and
dew point sensors. In addition, ambient condition sensors may include a door
sensor to sense the
openings and closings of door 102. The ambient temperature will typically vary
dynamically
according to the heat transfer to and from the environment by numerous
factors, the primary
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ones being operation of mechanical refrigeration unit 103, external ambient
temperatures, and
the number and duration of intrusions into refrigerated structure 101 by
people and/or goods via
door 102.
[0028] The management and control system preferably further includes one or
more goods
sensors 512 that sense the temperature and/or other parameter of the goods
within refrigerated
structure 101. As will be appreciated, depending upon the type of goods in
question and the
parameter to be sensed, goods sensor(s) 512 may be placed on an exterior of
one of the goods in
refrigerated structure 101 or embedded within the goods.
[0029] Controller 520 processes the sensor data received from sensors 502, 510
and 512 and,
responsive thereto, controls mechanical refrigeration unit 103 in accordance
with one or more
control methodologies implemented alternatively or in combination. For
example, the control
methodologies implemented by controller 520 can be configured to maintain the
interior volume
of refrigerated structure 101 within a desired temperature range while:
= maintaining the PCM within desired region(s) of its phase change curves
as determined
from the ambient, goods, and PCM temperatures,
* minimizing or reducing power and/or energy consumption,
e minimizing or reducing utility costs,
* reducing cost of operation of mechanical refrigeration unit 103;
e increase the useful life of mechanical refrigeration unit 103;
O minimizing or reducing the cycling and/or duration of operation of
mechanical
refrigeration unit 103,
O preferentially operating mechanical refrigeration unit 103 during desired
time periods
(e.g., during off-peak hours),
O maximizing or increasing utility rebates or incentives to the utility
customer,
O reducing the peak or average load of a utility system, and/or
G controlling based upon one or more additional factors.
[0030] As indicated, controller 520 may optionally be further communicatively
coupled to a
communication interface 522, which communicates status information and/or
alarms regarding
cold storage system 100 to one or more remote locations via one or more wired
or wireless
packet switched or circuit switched communication networks. The status
information and/or
alainis can be communicated, for example, to a remote server computer, mobile
phone, or pager
of an operator of cold storage system 100, a service provider or service
technician of the
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operator, or an electrical utility provider. The status information and/or
alarms can be
communicated, for example, in a textual message, numeric message and/or a data
message,
communicated, for example, in an email, short message service (SMS) message,
phone call,
page, HTTP message, or the like.
[0031] Referring back to FIGs. 1-5B, in operation controller 520 preferably
initially activates
mechanical refrigeration system 103 to produce chilled, forced-air current
112, which charges
the endothermic PCM contained in overhead PCM tubes 105 and under-shelf PCM
containers
106 and cools interior 104 of refrigerated structure 101. Controller 520
preferably operates
mechanical refrigeration unit 103 in its active chill mode until the ambient
temperature of
interior 104 sensed by ambient temperature sensor 506 achieves at least a
first threshold
temperature, the endothermic PCM achieves stasis, as indicated by temperature
sensor(s) 502,
and the temperature of the goods indicated by goods sensor(s) 512 reaches a
second threshold
temperature. In response, controller 520 suspends or substantially reduces the
operation of
mechanical refrigeration unit 103.
[0032] Once the PCM in overhead endothermic PCM tubes 105 and under-shelf PCM
containers
106 has been thermally charged to stasis, the endotheimic (i.e., heat
absorbing) characteristics of
the PCM significantly extends the period of time over which the internal
temperature of
refrigerated structure 101 and the goods disposed therein will remain at or
below the
predetermined maximum temperature without having to operate mechanical
refrigeration unit
103. Eventually, the PCM begins to transition from the latent heat mode to the
sensible heat
mode and the capacitive cooling effect of the PCM wanes. Controller 520 senses
this condition
and operates mechanical refrigeration unit 103 in its active chill mode to
recharge the PCM to its
latent heat mode and maintain the goods temperature and ambient temperature of
refrigerated
structure 101 within desired temperature ranges.
[0033] All of the apparatus and methods disclosed and claimed herein can be
made and executed
without undue experimentation in light of the present disclosure. While
various embodiments
have been described, it will be appreciated by those skilled in the art that
variations may be
applied to the described embodiments without departing from the concept,
spirit and scope of the
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invention. More specifically, it will be apparent that certain components may
be added to,
combined with, or substituted for the components described herein while the
same or similar
results would be achieved. All such similar substitutes and modifications
apparent to those
skilled in the art are deemed to be within the spirit, scope and concept of
the invention as defined
by the appended claims. Accordingly, the particular arrangements disclosed are
meant to be
illustrative only and not limiting as to the scope of the invention which is
to be given the full
breadth of the appended claims and any and all equivalents thereof.
