U.S. patent application number 12/653689 was filed with the patent office on 2010-06-17 for thermal energy storage apparatus.
Invention is credited to Jan Vetrovec.
Application Number | 20100147486 12/653689 |
Document ID | / |
Family ID | 42239135 |
Filed Date | 2010-06-17 |
United States Patent
Application |
20100147486 |
Kind Code |
A1 |
Vetrovec; Jan |
June 17, 2010 |
Thermal energy storage apparatus
Abstract
The present invention provides a thermal energy storage (TES)
apparatus having a fast response to heat, which is also simple,
lightweight, compact, and inexpensive to fabricate. In one
preferred embodiment of the present invention, phase change
material (PCM) is enclosed in a tubular container. A brush-like
heat spreading element having radial bristles is installed in the
tube within the PCM. The bristles are made of wires or fibers
having good thermal conductivity and their ends are in a good
thermal contact with the interior wall of the tube. Heat from
external source is deposited into the tube exterior and conducted
through the wall, transferred to the bristles, and conducted
through the bristles in a generally radial direction substantially
through out the PCM volume. The TES may be used in buildings to
stabilize temperature and thus reduce the cost of building climate
control such as heating and air conditioning.
Inventors: |
Vetrovec; Jan; (Larkspur,
CO) |
Correspondence
Address: |
Aqwest LLC
P.O. BOX 468
Larkspur
CO
80118
US
|
Family ID: |
42239135 |
Appl. No.: |
12/653689 |
Filed: |
December 16, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61201885 |
Dec 16, 2008 |
|
|
|
Current U.S.
Class: |
165/10 ;
165/104.17; 165/104.21 |
Current CPC
Class: |
Y02E 60/14 20130101;
Y02E 60/145 20130101; F28D 20/02 20130101 |
Class at
Publication: |
165/10 ;
165/104.17; 165/104.21 |
International
Class: |
F28D 17/00 20060101
F28D017/00; F28D 15/00 20060101 F28D015/00 |
Goverment Interests
GOVERNMENT RIGHTS IN THIS INVENTION
[0002] This invention was made with U.S. government support under
contract number FA8650-08-M-5026. The U.S. government may have
certain rights in this invention.
Claims
1. A thermal energy storage (TES) apparatus comprising: a) a
tubular container having an external surface, an internal surface,
and internal volume; b) a phase change material (PCM) substantially
filling said interior volume; and c) a heat spreading element (HES)
inside said interior volume; said HES having radially extending
bristles; said bristles being substantially immersed in said PCM;
said bristles having end tips; said end tips being in a good
thermal contact with said interior surface of said tubular
container.
2. The TES of claim 1 further comprising groves on said interior
surface.
3. The TES of claim 1 further comprising surface extensions on said
interior surface.
4. The TES of claim 1 wherein said external surface is
substantially immersed in a medium selected from the family
consisting of liquid, gas, solid, and environment.
5. The TES of claim 1 wherein said external surface is
substantially immersed in a medium selected from the family
consisting of liquid, gas, solid, and environment.
6. The TES of claim 1 wherein said bristles are made of material
selected from the family consisting copper, copper alloys,
aluminum, aluminum alloys, graphite fiber, carbon fiber, and
Thornel K-1100 graphite fiber.
7. The TES of claim 1 wherein said bristles are configured as
wires.
8. The TES of claim 1 wherein said tubular container is made of
material selected from the family consisting copper, copper alloys,
aluminum, and aluminum alloys.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from the U.S. provisional
patent application U.S. Ser. No. 61/201,885, filed on Dec. 16,
2008, entitled "THERMAL ENERGY STORAGE APPARATUS."
FIELD OF THE INVENTION
[0003] This invention relates generally to apparatus and methods
for conduction of heat and more specifically to to apparatus and
methods for storage of thermal energy.
BACKGROUND OF THE INVENTION
[0004] The invention is for a thermal energy storage (TES)
apparatus and method. TES is often used in devices and systems to
temporarily store heat. For example, a TES apparatus may be used to
average out a temperature in a heating system in a building or a
vehicle with the objective of reducing the cost of energy expended
in heating. In particular, TES can reduce the cost of heating a
building during winter season by absorbing heat (possibly with the
air of a solar panel) during warm daytime hours and releasing
stored heat during colder nighttime hours. Similarly, a TES
apparatus may be used to average out a temperature in an air
conditioning system in a building or a vehicle with the objective
of reducing the cost of energy expended in heating or air
conditioning. Another application of TES is for averaging out of
waste heat load in an automotive engine as disclosed by the
Applicant in U.S. Pat. No. 7,464,672, entitled "Engine cooling
system with overload handling capability," issued to the Applicant
on Dec. 16, 2008, which is hereby incorporated by reference in its
entirety. A TES apparatus may use a phase change material
(PCM).
[0005] Phase Change Materials: For the purposes of this invention,
a material that changes in heat content upon undergoing a
reversible solid-liquid phase transformation is defined as a phase
change material (PCM). PCMs, synonymously known as latent thermal
energy storage materials, are used for thermal energy storage. The
absorption of the necessary quantity of energy by the solid PCM
results in melting. The energy absorbed by the PCM to change phase
at its characteristic melting temperature is known as the latent
heat of fusion. The latent heat of fusion stored in the liquid
state is released upon resolidification. Thus the PCM may absorb
thermal energy from a body at a higher temperature than the PCM,
until the PCM undergoes a reversible melt. A molten PCM may
transfer thermal energy to a body at a lower temperature than the
PCM and it may thereby undergo a reversible solidification
(freeze).
[0006] Efficient PCMs have several desirable thermo-chemical
properties including high latent heat of fusion, high thermal
conductivity, low supercooling, and the ability to cycle thermally
from solid to liquid and back to solid many times without
degradation. The term "supercooling" refers to a discrepancy
between the temperature at which solidification (freezing)
initiates and the melting temperature of a given PCM when cooled
and heated under quiescent conditions. A significant amount of PCM
research is devoted to finding nucleating agents additives that
will suppress supercooling. The term "additives" includes, in
addition to nucleating agents, precursors of such additives which
are non-detrimental to the function of the phase change materials.
Considerations for selection of suitable PCMs may also include
melting temperature, density, packaging, toxicity and cost. Many
suitable PCM have a very low density, generally less than 2 grams
per cubic centimeter and, in many cases, less than 1 gram per cubic
centimeter.
[0007] Many PCM capable of storing significant amount of heat are
also very poor thermal conductors. This makes it very challenging
to transport heat into and out of the PCM, and limits the
usefulness of such PCM in a TES. Heat spreading elements may be
used to transport heat through out PCM volume, thereby improving
the volumetric (bulk) thermal conductivity of PCM. Use of such heat
spreading elements can significantly increase the rates at which
heat is transported to or from the TES. As a result, TES has a
faster temporal response to applied heat, see, for example, U.S.
Pat. No. 7,106,777 granted to A. Delgado, Jr et al. on Sep. 12,
2006, which is hereby expressly incorporated by reference in its
entirety. Such heat spreading elements disclosed in prior art may
be formed as foams or structures. However, heat spreading elements
of prior art are heavy, bulky, expensive to construct, and
expensive to install into the TES. In view of the limitations of
the prior art, there is a need for an improved TES apparatus
capable of rapidly absorbing applied heat, and capable of rapidly
releasing absorbed heat.
[0008] In summary, prior art does not teach a TES capable of fast
response to applied heat that is also simple, lightweight, compact,
and inexpensive to fabricate. It is against this background that
the significant improvements and advancements of the present
invention have taken place.
SUMMARY OF THE INVENTION
[0009] The present invention provides a TES apparatus having a fast
response to heat, which is also simple, lightweight, compact, and
inexpensive to fabricate.
[0010] In one preferred embodiment of the present invention, TES is
configured as a tubular container (tube) substantially filled with
PCM. A heat spreading element (HSE) having radial bristles is
installed in the tube within the PCM. The HSE may be formed as a
brush, having bristles extending radially from a central core.
Brushes having bristles made of appropriate material and extending
radially from a central core have been known in prior art as "pipe
brushes", see FIG. 1. Pipe brushes are typically used for cleaning
of pipes, types, bottles, and laboratory test tubes. In the HSE of
the subject invention, the bristles are made of wires or fibers
having good thermal conductivity. Ends of the bristles are arranged
to be in a good thermal contact with the interior wall of the
tubular container. Heat from an external medium, which may be
liquid, gas, solid, or environment is deposited into the exterior
surface of the tubular container, conducted through the container
wall, transferred to the bristles, and conducted through the
bristles in a generally radial direction, and substantially
transferred into the PCM. Conversely, heat may be released by the
PCM, deposited substantially into the HSE bristles, conducted
through the bristles and into the interior wall of the tubular
container, conducted through the the container wall, and
transferred from the exterior surface of the tubular container into
a liquid, gas, solid, or environment. In either case, conduction of
heat in radial directly inside the TES tubular contained takes
place substantially in the radial bristles, thereby greatly
enhancing the speed at which heat can be transferred to and from
the volume of the PCM.
[0011] Accordingly, it is an object of the present invention to
provide a TES apparatus having the capability to rapidly absorb
large amounts of heat, which is also simple, lightweight, compact,
and inexpensive to fabricate.
[0012] It is another object of the invention to provide a TES
apparatus having the capability to rapidly release large amounts of
heat, which is also simple, lightweight, compact, and inexpensive
to fabricate.
[0013] It is yet another object of the invention to provide a heat
spreading element which is also simple, lightweight, compact, and
inexpensive to fabricate.
[0014] It is still another object of the invention to enhance
radial conduction of heat in a PCM.
[0015] These and other objects of the present invention will become
apparent upon a reading of the following specification and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a pipe brush for cleaning of tubes, pipes, and
bottles (Prior Art).
[0017] FIG. 2 shows a cross-sectional view through the inventive
TES apparatus in a plane parallel to the longitudinal axis.
[0018] FIG. 3 shows a a cross-sectional view through the inventive
TES apparatus in a plane perpendicular to the longitudinal
axis.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Selected embodiments of the present invention will now be
explained with reference to drawings. In the drawings, identical
components are provided with identical reference symbols. It will
be apparent to those skilled in the art from this disclosure that
the following descriptions of the embodiments of the present
invention are merely exemplary in nature and are in no way intended
to limit the invention, its application, or uses.
[0020] Referring now to FIG. 2, there is shown a cross-sectional
view through the TES apparatus 100. The TES apparatus 100 comprises
a tubular container 102, heat spreading element (HSE) 104, and PCM
106. The tubular container 102 is preferably made of material
having good thermal conductivity, such as, but not limited to
copper, copper alloys, aluminum, and aluminum alloys. The tubular
container 102 has an external surface 110 adapted for communicating
heat to and from a medium 112, such as gas, air, liquid, solid, or
an environment. In some variants of the subject invention, the
tubular element 102 may be substantially immersed in the medium
112. In addition, the tubular container 102 has an internal surface
114. The interior volume of the tubular container 102 is
substantially filled with PCM 106. The internal surface 114 may be
adapted for communicating heat to and from PCM 106. For example,
the internal surface 114 may be equipped with groves and ridges, or
other forms of surface extensions. The HSE 104 has radially
extending bristles 108 in a good thermal contact with the internal
surface 114. The bristles 108 are formed as wires, fiber, or
filament, and are made of material having good thermal
conductivity. For example, the bristles 108 may be made of metal
such as copper, copper alloys, aluminum, or aluminum alloys. As
another example, the bristles 108 may be made from carbon fiber or
from graphite fiber. In particular, the bristles 108 may be made
from Thornel K-1100 graphite fiber available from Cytec Industries
Inc., Woodland Park, N.J. The Thornel K-1100 graphite fiber has a
reported longitudinal thermal conductivity around 1,000 W/m-degree
K, which greatly exceeds the thermal conductivity of known metals.
In one variant of the invention, the HSE 104 may be generally
formed as a pipe brush having bristles 108 that radiate from a
central core 116. The central core 116 may be formed by twisting
together two (or more) lengths of wire 118a and 118b. In
particular, the of wires 118a and 118b are twisted so that the
bristles 108 are trapped between them, thereby forming a pipe
brush-like structure. As already noted, pipe brushes equipped with
bristles of appropriate material are used for cleaning bottles,
tubes, and pipes. It is important to make the brush diameter
slightly larger than the diameter of the internal surface 114, so
that upon insertion, the bristle ends are forced into a good
thermal contact with the internal surface 114, see FIG. 3.
Preferably, the HSE 104 is installed into the tubular container 102
first, and the PCM in a molten form is poured in afterwards.
[0021] While the tubular container 102 shown in FIG. 3 has a
circular cross-section, the invention may be practiced with tubular
containers having elliptical, square, rectangular, hexagonal,
polygonal, and other suitable cross-sections. The HSE 104 also may
be formed to have other than round cross-section. The internal wall
114 may be equipped with groves to designed to receive the ends of
bristles 108 and thus enhance heat transfer between the tubular
container 102 and the bristles 108. Suitable groves may be radial
or longitudinal with respect to the tubular container 102. The
external surface 110 may also include suitable surface extensions
such as groves, ridges or fins. The PCM 106 may be a wax, paraffin,
or other suitable material.
[0022] In operation, heat is transferred from medium 112 to the
external surface 110 of the tubular container 102, conducted
through the wall to the internal surface 114, transferred to the
bristles 108, conducted through the bristles 108, and transferred
to the PCM 106. As a result of received heat, the PCM 106 may
substantially melt, thereby temporarily storing the heat.
Conversely, the PCM 106 may substantially solidify and release
heat. Released heat is conducted to the bristles 108, and through
the bristles 108 to the internal surface 114 of the tubular
container 102, conducted through the wall to the external surface
110, and transferred therefrom to the medium 112.
[0023] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," and "includes"
and/or "including" when used in this specification, specify the
presence of stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
components, and/or groups thereof.
[0024] The terms of degree such as "substantially", "about" and
"approximately" as used herein mean a reasonable amount of
deviation of the modified term such that the end result is not
significantly changed. For example, these terms can be construed as
including a deviation of at least .+-.5% of the modified term if
this deviation would not negate the meaning of the word it
modifies.
[0025] Moreover, terms that are expressed as "means-plus function"
in the claims should include any structure that can be utilized to
carry out the function of that part of the present invention. In
addition, the term "configured" as used herein to describe a
component, section or part of a device includes hardware and/or
software that is constructed and/or programmed to carry out the
desired function.
[0026] While only selected embodiments have been chosen to
illustrate the present invention, it will be apparent to those
skilled in the art from this disclosure that various changes and
modifications can be made herein without departing from the scope
of the present invention as defined in the appended claims.
Furthermore, the foregoing description of the embodiments according
to the present invention are provided for illustration only, and
not for the purpose of limiting the present invention as defined by
the appended claims and their equivalents. Thus, the scope of the
present invention is not limited to the disclosed embodiments.
* * * * *