Note: Descriptions are shown in the official language in which they were submitted.
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FLUID STORAGE CONTAINERS WITH BAFFLES
Cross-Reference to Related Applications:
This application claims the benefit of U.S. Provisional Patent Application
Ser. No.
60/934,635, filed June 15, 2007 and entitled FLUID STORAGE CONTAINERS WITH
BAFFLES; which is hereby incorporated herein by reference in its entirety for
all purposes.
Field of the Invention:
The present invention relates to the field of fluid containers. More
specifically, the
present invention relates to the field of fluid containers containing a baffle
for controlling heat
absorption.
Background of the Invention:
The demand for energy in general, and natural gas in particular, has been
steadily
rising over the past decades. Furthermore, the price of energy, has been
rapidly increasing
over the past few years. With these trends in mind, products which utilize
less energy are
always welcomed by consumers.
Natural gas-fired water heaters are simple units that store part of the energy
released
by burning of the fuel inside an insulated tank that is filled with water. A
superior water
heater is able to absorb a greater percentage of the thermal energy liberated
by the burning of
natural gas, and at the same time, exhibit low heat losses to the environment.
Lowering heat
losses through insulating the storage tank is widely practiced and promoted.
Attempts to
increase the heat absorption by the storage tank have been pursued through
introducing
helical swirl tapes to promote convective and radiative modes of heat
exchange. Ways of
improving heat absorption and preventing heat loss are continuously sought
after objectives.
Summary of the Invention:
A fluid storage container with a baffle controls the heat absorption
percentage of the
container. Fluid that is heated adjacent to the surface of a container rises
replacing colder
fluid which sinks downward, regardless of the baffle. This behavior is able to
lead to onset of
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oscillations in the temperature and flow fields. Due to blockage effect of a
thin baffle, multi-
cell recirculating vortex structures are observed. The number and strength of
these vortices
depend on the position and length of the baffle. For certain placements and
lengths of the
baffle, the time rate of the rise of the bulk temperature is increased or
decreased.
In one aspect, a system comprises a container for storing a fluid and a baffle
within
the container, the baffle configured for controlling heat absorption in the
fluid. Controlling
heat absorption in the fluid includes increasing heat absorption in the fluid.
Alternatively,
controlling heat absorption in the fluid includes decreasing heat absorption
in the fluid. The
container comprises one of a cylindrical and a spherical shape. The container
and the baffle
comprise a conductive material. The container and the baffle comprise steel.
The baffle
comprises one of a ring shape and an extension of a wall of the container. In
some
embodiments, the baffle comprises a length of approximately 0.25 of the
diameter of the
container. In some embodiments, the baffle is positioned with one of an angle
of 30 , 60 ,
90 , 120 and 150 . The baffle is positioned proximate to the bottom of the
container. The
baffle is movable. The baffle is foldable, thus allowing the appropriate
degree of control of
heat transfer that may depend on the liquid level maintained in the container.
In another aspect, a method of providing heated water comprises filling a
storage
container with water, the storage container including an internal baffle and
heating the storage
container and the baffle to heat the water. The container comprises one of a
cylindrical and a
spherical shape. The container and the baffle comprise a conductive material.
The container
and the baffle comprise steel. The baffle comprises one of a ring shape and an
extension of a
wall of the container. In some embodiments, the baffle comprises a length of
approximately
0.25 of the diameter of the container. In some embodiments, the baffle is
positioned with one
of an angle of 30 , 60 , 90 , 120 and 150 . The baffle is positioned
proximate to the bottom
of the container.
In another aspect, an apparatus comprises a cylindrical storage container for
storing a
fluid and a ring-shaped baffle coupled within the container, the baffle
configured for
increasing heat absorption in the fluid, wherein the container and the baffle
comprise a
conductive material. In some embodiments, the baffle comprises a length of
approximately
0.25 of the diameter of the container. The conductive material comprises
steel. In some
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embodiments, the baffle is positioned with one of an angle of 30 , 60 , 90 ,
120 and 150 .
The baffle is positioned proximate to the bottom of the container.
In another aspect, a water heater comprises a container for storing a fluid, a
heating
element positioned below the container for heating the fluid within the
container and a baffle
within the container, the baffle configured for increasing heat absorption in
the fluid. The
water heater further comprises a cold water inlet and a hot water outlet
coupled to the
container, the cold water inlet for receiving cold water into the container
and the hot water
outlet for releasing hot water from the container. The container and the
baffle comprise a
conductive material. The container and the baffle comprise steel. The baffle
comprises one
of a ring shape and an extension of a wall of the container. In some
embodiments, the baffle
comprises a length of approximately 0.25 of the diameter of the container. In
some
embodiments, the baffle is positioned with one of an angle of 30 , 60 , 90 ,
120 and 150 .
The baffle is positioned proximate to the bottom of the container.
In another aspect, a method of controlling heat absorption in a fluid
comprises
inputting fluid into a storage container, the storage container including an
internal baffle and
controlling heat absorption of the fluid with the baffle. The container
comprises one of a
cylindrical and a spherical shape. The container and the baffle comprise a
conductive
material. The container and the baffle comprise steel. The baffle comprises
one of a ring
shape and an extension of a wall of the container. In some embodiments, the
baffle
comprises a length of approximately 0.25 of the diameter of the container. In
some
embodiments, the baffle is positioned with one of an angle of 30 , 60 , 90 ,
120 and 150 .
The baffle is positioned proximate to the bottom of the container.
In another aspect, a system for storing and transporting liquid natural gas
comprises a
container for storing the liquid natural gas and a baffle within the
container, the baffle
configured for reducing heat absorption in the liquid natural gas. In some
embodiments, the
container comprises one of a spherical shape, a polygonal cross section shape,
a membrane
design and a MossTM design. The container and the baffle comprise a conductive
material.
The container and the baffle comprise steel. The baffle comprises an extension
of a wall of
the container. In some embodiments, the baffle is positioned with one of an
angle of 30 ,
60 , 90 , 120 and 150 .
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Brief Description of the Drawings:
FIG. 1 illustrates a schematic drawing of a baffle placed on the inner wall of
a
spherical container.
FIG. 2 illustrates pseudosteady-state streamline patterns and temperature
contours
with an isothermal baffle placed at various locations for varying Rayleigh
(Ra) numbers.
FIG. 3 illustrates a graph of the dependence of the Nusselt number on the
location of
the baffle, 4.
FIG. 4 illustrates a cross section view of a water heater with a baffle of an
embodiment in accordance with the present invention.
FIG. 5 illustrates a top view of the baffle of an embodiment in accordance
with the
present invention.
FIG. 6 illustrates a flowchart of a method of utilizing a storage container
with a baffle
to efficiently provide heated water of an embodiment in accordance with the
present
invention.
FIG. 7 illustrates a spherical liquid natural gas container for storing and
transporting
liquid natural gas.
FIG. 8 illustrates a flowchart of a method of utilizing a storage container
with a baffle
to efficiently control the heat absorption of a fluid of an embodiment in
accordance with the
present invention.
Detailed Description of the Preferred Embodiment:
A storage tank with a baffle is able to control heat absorption into a fluid.
For
example, heat absorption is able to be increased so that less energy is
required to heat water,
or heat absorption is lessened so that a cooled fluid such as liquid natural
gas is able to
remain at the appropriate temperature for a longer period of time. The flow of
the fluid is
modified such as generating vortices by the baffle so that heat is more or
less efficiently
transferred into the fluid.
Figure 1 illustrates a schematic drawing of a thin baffle 102 placed on the
inner wall
of a spherical container 100 with a diameter D. In some embodiments, the
baffle 102 is an
extended surface of the wall of the container 100. The baffle 102 and the wall
of the
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spherical container 100 have high thermal conductivity. In effect, the
temperature of the
baffle 102 is the same as that of the wall of the spherical container 100,
thus termed
isothermal. The baffle 102 with a length 1 makes a right angle with the inner
surface of the
spherical container 100 and is positioned at polar angle Bb. In some
embodiments, the baffle
102 is part of a cone with its apex coinciding with the center of the
spherical container 100.
The flow and thermal fields are dictated by the Rayleigh (Ra) number, Prandtl
(Pr) number,
length of the baffle and its polar angle position. It has been found that the
Pr number has
little effect on the results. The Ra number, dimensionless length of the
baffle (L = l/ D) and
polar angle position, Bb, have been varied to determine the best results.
Figure 2 illustrates pseudosteady-state streamline patterns and temperature
contours
with an isothermal baffle (L = 0.25) placed at various locations for varying
Rayleigh (Ra)
numbers. The Ra number variations include: 104, 105, 106 and 107 , and the
baffle's position
variations include: Bb = 30 , 90 and 150 . With the baffle positioned near
the top at 6b = 30
(left column), the increase of the Ra number brings about stronger convection
and fluid flow
within the clockwise rotating vortex as indicated by the denser packing of the
streamlines
next to the surface. This is accompanied by lifting of the eye of the vortex
and its migration
outward. For the highest Ra number used, two vortices occupy the top
hemisphere. For this
case, the top hemisphere is partially stratified with stable constant-
temperature layers
occupying it, whereas the thermal field within the bottom hemisphere is
heavily affected by
the stronger rotating vortex that occupies it. The flow fields for the cases
with the longest
baffle positioned near the bottom at Bb = 150 (right column) exhibit many of
the features
with the baffle located at Bb = 30 , but in reverse in addition to the
appearance of another
counter clockwise rotating vortex for a wide range of Ra numbers. It should be
understood
that the angle of the baffle can be any appropriate angle and is not limited
to any specific
angle described herein for illustrative purposes. The appearance of this
counter clockwise
rotating vortex is directly linked to the isothermal surface of the baffle and
the resultant extra
heat released into the fluid from this surface. A recirculating vortex that
occupies the small
space between the baffle and the symmetry line of the sphere is generally
confined to the
lower hemisphere for all the Ra numbers and more dramatically in the vicinity
of the
symmetry axis for the higher Ra numbers. Extremely pronounced modifications of
the
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temperature fields are observed for the high Ra number cases showing that the
stratifications
are generally eliminated, and the extra heat added to the sphere is
transported inside by a
counter clockwise rotating vortex that is positioned next to the top surface
of the baffle.
The overall effects of the complex flow and thermal fields shown in Figure 2
on the
heat absorption ability of the system described provide evidence that the
baffle within the
storage container significantly affects the efficiency of heat absorption. The
heat absorption
rate is measured by the Nusselt number and its dependence on the position of
the baffle (6b)
with a thin isothermal baffle of different lengths (L = 0.05, 0.10 and 0.25)
for Ra = 10' is
presented in Figure 3. The reference case (the dashed line) is that of a
sphere without a
baffle. The short baffles tended to degrade the heat absorption by the fluid
in the sphere. The
0.25 baffle when placed near the bottom of the sphere increased the amount of
heat absorbed
by the fluid by 103 percent. It should be understood that the length of the
baffle can be any
appropriate length and is not limited to any specific length described herein
for illustrative
purposes.
Figure 4 illustrates a cross section view of a water heater 400 with a baffle
430 of an
embodiment in accordance with the present invention. For the most part, the
water heater
400 is a standard water heater with the addition of the baffle 430. In some
embodiments, the
water heater 400 is cylindrically shaped and in some embodiments, the water
heater 400 is
spherically shaped. The water heater includes a cold water inlet 402 where
cold water is
received. In some embodiments, a water meter 404 is used to measure the water
received.
The water goes to a storage tank 424 of the water heater 400 to be heated. To
heat the cold
water, a burner 412 is included in the water heater 400. The burner 412 is
positioned below
where the water is stored so that the burner 412 heats the water from beneath.
Hot air from
the burner 412 travels up a heating pipe 428 which also heats the water. The
burner 412
receives gas through a natural gas inlet 406. In some embodiments, a gas flow
meter 408
monitors the flow of the gas into the burner 412. An air inlet 414 is included
in the water
heater 400 to provide the burner oxygen to properly burn the gas. In some
embodiments, a
drain valve 416 is included in case the water heater 400 needs to be drained.
In some
embodiments, a relief valve 418 is also included in the water heater 400. A
thermostat 410
measures the water temperature, and in conjunction with the gas inlet 406
provides the burner
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412 with the appropriate amount of gas to achieve the desired temperature. The
water heater
400 also includes an exhaust pipe 420 coupled to the heating pipe 428 for
allowing the
exhaust of the burner 412 to escape. A hot water outlet 422 is where the hot
water exits the
water heater 400 (e.g. to sinks, showers and bathtubs through pipes in a
person's house).
The baffle 430 is coupled inside the storage tank 424 of the water heater 400,
and in
some embodiments, to the heating pipe 428 to help conduct heat to the water in
the storage
tank 424. In some embodiments, the baffle 430 is circular, a thin piece of
material or another
shape. In some embodiments, more than one baffle is contained within the
storage container.
The baffle 430 comprises a conductive material such as steel. In some
embodiments, the
thickness of the baffle 430 is as thin as possible while still maintaining
structural soundness.
In some embodiments, the baffle is positioned at an angle such as 30 , 60 , 90
, 120 or 150 .
The location of the baffle is able to be located near the bottom of the
container, near the
middle of the container or near the top of the container.
Figure 5 illustrates a top view of the baffle 430 of an embodiment in
accordance with
the present invention. As described above, the baffle 430 is ring-shaped in
some
embodiments. In some embodiments, the ring-shaped baffle 430 is configured to
fit around
the heating pipe 428 (Figure 4). Thus, the inner diameter of the baffle 430 is
sized
accordingly. The outer diameter is sized such that the length between the
inner diameter and
the outer diameter maximizes the heat absorption of the water.
Figure 6 illustrates a flowchart of a method of utilizing a storage container
with a
baffle to efficiently provide heated water of an embodiment in accordance with
the present
invention. In the step 600, the storage container with the baffle is at least
partially filled with
a fluid such as water to be heated. In the step 602, the storage container and
baffle are heated.
In some embodiments, heating occurs by burning gas at the bottom of the
storage container
where the flames of the burning gas directly contact the storage container.
The heat is
conducted through the storage container and into the water as well as the
baffle.
Additionally, hot air travels up a heated air pipe which is in contact with
the baffle further
heating the baffle which provides additional heat to the water. Furthermore,
the baffle
provides the fluid flow described above which further enhances heat absorption
by the water.
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In addition to a baffle within a water heater to improve heat absorption,
there are
many other applications for a container with a baffle. In general, a baffle is
able to assist in
controlling heat absorption. Instead of a baffle being used for heating a
fluid more quickly,
the baffle is also able to be used to prevent a fluid from heating quickly.
Baffles within
containers are able to be used in any industry, including, but not limited to,
water heaters, and
storage and transportation of liquid natural gas and liquid hydrogen.
Figure 7 illustrates a spherical liquid natural gas container 700 for storing
and
transporting liquid natural gas. The container 700 includes one or more
baffles which control
the heat absorption of the liquid natural gas. Specifically, the baffles are
configured to lessen
or minimize the heat absorption by the liquid natural gas to prevent boiloff,
thus allowing
more of the liquid natural gas to remain. The spherical shape illustrated in
Figure 7 is for
illustrative purposes. In some embodiments, the container 700 is able to be a
polygonal cross
section shape, a membrane design or a MossTM design.
Figure 8 illustrates a flowchart of a method of utilizing a storage container
with a
baffle to efficiently control the heat absorption of a fluid. In the step 800,
the storage
container with the baffle is at least partially filled with a fluid. In the
step 802, the baffle
controls the heat absorption of the fluid. In some embodiments, if the fluid
is heated, the
baffle increases the heat absorption as described above. In some embodiments,
if it is desired
that the fluid temperature not rise quickly, the baffle will decrease the heat
absorption of the
fluid.
Furthermore, the shape, size, angle, orientation, material and any other
feature of the
baffle is not limited to those described above. As long as the desired effect
is achieved, the
baffle is able to be configured in any manner. For example, instead of a steel
baffle, the
baffle is able to comprise a low conducting material, such as a hard plastic
which has similar
qualities as steel. Moreover, the qualities of the container are not limited
to those described
above. For example, the shape of the container is able to be cylindrical,
spherical, polygonal
cross section or any other shape.
In some embodiments, the baffle is movable and/or configurable. For example,
the
baffle is able to be made of a material with a specific buoyancy so that the
baffle rises and
falls as desired. In another example, the baffle is foldable so that the
length of the baffle is
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variable, thus allowing the appropriate degree of control of heat transfer
that may depend on
the liquid level maintained in the container. Other implementations such as a
motor-driven
baffle are able to be implemented so that the baffle is configurable. These
implementations
are able to be used to change the position, length, angle, orientation or any
other quality of the
baffle.
For clarity, the baffle within the container is able to be implemented
regardless of the
quantity of fluid in the container. For example, although water heaters are
filled entirely or
almost entirely with water; liquid natural gas containers usually are 75%
filled. The baffle
within either container still controls the heat absorption as desired.
To utilize a storage container such as a water heater with a baffle, a user
need not
perform different actions compared with a storage container without a baffle.
For example, if
a user has a water heater with a baffle within his house, when the user turns
on hot water for
washing dishes or taking a shower, the user simply turns the hot water
handle/lever and hot
water comes out of the faucet. These actions are no different than if the hot
water heater did
not have a baffle.
In operation, a storage container with a baffle is able to control heat
absorption such
as to heat water more quickly and efficiently, thus saving time and energy.
The baffle
transfers additional heat to the water as well as allows the proper flow of
the fluid to increase
heat absorption into the water. If a user chooses to take a long shower, the
hot water heater
with baffle is able to heat the water quickly enough to provide hot water for
a longer period of
time. Additionally, since the water is heated more efficiently, less energy
such as gas is used,
thus decreasing wasted energy and saving the user money. For other
applications such as
liquid natural gas storage and transport, the baffle reduces boiloff by
reducing heat absorption
of the liquid natural gas. Depending on the application, the baffle within the
container is able
to control heat absorption as desired.
The present invention has been described in terms of specific embodiments
incorporating details to facilitate the understanding of principles of
construction and
operation of the invention. Such reference herein to specific embodiments and
details thereof
is not intended to limit the scope of the claims appended hereto. It will be
readily apparent to
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one skilled in the art that other various modifications may be made in the
embodiment chosen
for illustration without departing from the spirit and scope of the invention
as defined by the
claims. Specifically, it should be understood that the angle of the baffle can
be any
appropriate angle and is not limited to any specific angle described herein
for illustrative
purposes. Further, it should also be understood that the length of the baffle
can be any
appropriate length and is not limited to any specific length described herein
for illustrative
purposes.
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