U.S. patent application number 13/113965 was filed with the patent office on 2011-11-24 for reusable high temperature thermal protection system.
Invention is credited to Sumon K. SINHA, Sumontro SINHA.
Application Number | 20110284189 13/113965 |
Document ID | / |
Family ID | 44971477 |
Filed Date | 2011-11-24 |
United States Patent
Application |
20110284189 |
Kind Code |
A1 |
SINHA; Sumontro ; et
al. |
November 24, 2011 |
REUSABLE HIGH TEMPERATURE THERMAL PROTECTION SYSTEM
Abstract
A reusable phase change material (PCM) heat shield is disclosed.
The heat shield comprises: a thermally conductive casing, PCM,
thermally conductive open cell foam, and heat pipes. The heat flows
through the casing and open cell foam into the PCM, heating it up.
The PCM changes phase twice, from solid to liquid. During the solid
liquid phase change, heat pipes begin to draw heat away from the
PCM to a secondary location that re-radiates the heat away. The
open cell foam serves to help channel hear into the PCM. In one
embodiment, the PCM heat shield can be used for thermal protection
of an atmospheric entry vehicle (ARV). In another, the PCM heat
shield may be applied to an aircraft engine to transfer extracted
heat to preheat incoming air. In another, the PCM heat shield is
integrated into the structure of a spacecraft, and used to both
carry loads and protect against high temperatures.
Inventors: |
SINHA; Sumontro; (Oxford,
MS) ; SINHA; Sumon K.; (Oxford, MS) |
Family ID: |
44971477 |
Appl. No.: |
13/113965 |
Filed: |
May 23, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61347759 |
May 24, 2010 |
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Current U.S.
Class: |
165/104.26 |
Current CPC
Class: |
Y02T 50/60 20130101;
Y02E 60/145 20130101; F02C 7/24 20130101; Y02T 50/671 20130101;
F28D 15/02 20130101; F28F 13/003 20130101; F28D 20/02 20130101;
Y02T 50/675 20130101; F05D 2300/612 20130101; Y02E 60/14 20130101;
F23M 5/08 20130101; F23R 3/005 20130101 |
Class at
Publication: |
165/104.26 |
International
Class: |
F28D 15/04 20060101
F28D015/04 |
Claims
1. A heat shield comprises: a thermally conductive casing; a phase
change material (PCM) coupled to the casing; thermally conductive
open cell foam coupled to the PCM; and a plurality of heat pipes
coupled to the foam, wherein the heat flows through the casing and
open cell foam into the PCM, wherein the PCM changes phase twice,
from solid to liquid, during the solid liquid phase change the heat
pipes begin to draw heat away from the PCM to a secondary location
that re-radiates the heat.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Under 35 USC 119(e), this application claims the benefit of
U.S. Patent Application Ser. No. 61/347,759, entitled "REUSABLE
HIGH TEMPERATURE THERMAL PROTECTION SYSTEM," filed on May 24, 2010,
which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to heat shields and
more particularly relates to a thermal protection method and system
for heat shields.
BACKGROUND OF THE INVENTION
[0003] Heat shields are used in the aerospace industry for vehicles
and engines that operate in high temperature environments. The
state of the art in aerospace heat shields is radiative protection.
Utilizing a material that has extreme high temperature resistance,
high thermal conductivity, and high emissivity, this material is
applied to the leading edge or nosecone of a vehicle. The heat that
is generated there gets transferred into the material, and then
conducted up the vehicle, before being radiated out at a cooler
section of the vehicle. The state of the art has three main
problems that have prevented its use on all vehicles and engines:
weight, brittleness, and manufacturability. The materials that have
the high temperature resistance, usually some compound of hafnium
or zirconium, are all very dense. Radiative heat shields require
acreage coverage, having a continuous shield from the bottom to top
of a vehicle to work properly. Large coverage with a dense material
forces the heat shield to be very heavy. These materials are also
very brittle, meaning that they cannot be used to help support the
loads generated by the vehicle or engine. Last, also due to the
material brittleness, manufacturing smooth shapes out of the
material is difficult. Accordingly what is desired is a system and
method that addresses the above identified issues. The system and
method should be easy to implement, cost effective, and adaptable
to existing environments. The present invention addresses such a
need.
[0004] Accordingly, what is desired is to provide a system and
method that overcomes the above issues. The present invention
addresses such a need.
SUMMARY OF THE INVENTION
[0005] A reusable phase change material (PCM) heat shield is
disclosed. The heat shield comprises: a thermally conductive
casing, PCM, thermally conductive open cell foam, and heat pipes.
The heat flows through the casing and open cell foam into the PCM,
heating it up. The PCM changes phase twice, from solid to liquid.
During the solid liquid phase change, heat pipes begin to draw heat
away from the PCM to a secondary location that re-radiates the heat
away. The open cell foam serves to help channel heat into the
PCM.
[0006] In one embodiment, the PCM heat shield can be used for
thermal protection of an atmospheric entry vehicle (ARV). In
another, the PCM heat shield may be applied to an aircraft engine
to transfer extracted heat to preheat incoming air. In another, the
PCM heat shield is integrated into the structure of a spacecraft,
and used to both carry loads and protect against high
temperatures.
[0007] Other aspects and advantages of the present invention will
become apparent from the following detailed description, taken in
conjunction with the accompanying drawings, illustrating by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 shows the six components of the heat shield.
[0009] FIG. 2 illustrates how the heat shield diffuses incoming
heat.
[0010] FIG. 3 shows how the heat is removed from the system.
[0011] FIG. 4 shows one variation of the system, designed for use
on atmospheric reentry vehicles (ARV's).
[0012] FIG. 5 shows how the nylon layer is created.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] The present invention relates generally to heat shields and
more particularly relates to a thermal protection method and system
for heat shields. The following description is presented to enable
one of ordinary skill in the art to make and use the invention and
is provided in the context of a patent application and its
requirements. Various modifications to the preferred embodiment and
the generic principles and features described herein will be
readily apparent to those skilled in the art. Thus, the present
invention is not intended to be limited to the embodiment shown but
is to be accorded the widest scope consistent with the principles
and features described herein.
[0014] The objective of the present invention is to provide
lighter, more robust, more manufacturable heat protection for use
in high temperature environments solving the problems described
above.
[0015] To achieve the above objective, the invention pertains to
both the heat shield and method of heat shield operation. The
present invention is a heat diffusion and storage device used for
thermal protection. It protects by storing and channeling heat to
other parts of the system. The casing and inlaid foam channels heat
into a phase change material. The phase change material lowers the
system temperature to allow the use of more common materials to
radiate heat out. The following figures further explain how the
device functions.
[0016] FIG. 1 shows the six components of the heat shield: a
metallic casing such as a titanium beta 21S alloy casing 100, nylon
coating on the inside of the casing 101, aluminum open cell metal
foam 104, heat pipes 105, and attachment standoffs 106. The
thermally conductive casing 100 and foam 104 transfer incoming heat
into the nylon 102.
[0017] FIG. 2 illustrates how the heat shield diffuses incoming
heat. The heat is absorbed by the nylon 101, allowing the casing
100 to be exposed to high heat fluxes for limited periods of time.
The nylon 101 absorbs heat by heating up as a solid, then changing
phase. The heat absorbed during the phase change caps the maximum
temperature approximately to the solid-liquid temperature.
[0018] FIG. 3 shows how the heat is removed from the system. Once
the nylon begins to change phase to a liquid, a bank of heat pipes
105 inlaid in the nylon activate to take heat away. The liquid
solidifies as the heat is transferred to a cooler part of the
system for eventual removal to the environment, such as by
radiation into space. This cycle allows the full thermal utility of
the nylon to be used, minimizing dead weight. It also lowers the
system temperature, allowing the metal casing 100 to retain enough
strength to carry structural loads. These two aspects help this
heat shield design be lighter than the state of the art.
[0019] FIG. 4 shows one variation of the system, designed for use
on atmospheric reentry vehicles (ARV's). It utilizes the vehicle
trajectory dynamics to maximize heat transfer. All ARV's undergo
moderate to high accelerations during the entry. In this heat
shield design, the accelerations are used to both to stratify
liquid/solid mixtures. The degree of heating faced by an ATV is
proportional to the magnitude of acceleration experienced. In this
variation of the system, due to the presence of an oxidizing
environment, the system temperature is kept below a specified
limit, to minimize the oxidation rate of the casing. Metal is used
as the casing material 100 to increase both system impact
resistance and manufacturability. Also, in this variation, if the
radiation heat transfer stops, or reverses, the system can mitigate
effects for a time by decomposing all of the nylon 103. As the
nylon 103 decomposes, pressure will be created in the casing, and
after a specified pressure is reached, relief valves 106 located on
the side of the system will evacuate the decomposed nylon, dumping
the heat from the system. This additional safety makes this heat
shield design more robust, allowing it to be put through punishing
environments without needing extensive material checks.
[0020] During assembly of the device, special attention must be
given to the contact resistance. In this design, no gap must be
present between the casing, nylon, water ice, and metal foam.
[0021] FIG. 5 shows how the nylon layer 102 is created. To ensure
there are no gaps, the nylon 102 must be poured into the casing as
a liquid, and then be allowed to solidify. Once solid, the nylon
102 must go through at least three phase change cycles under
applied pressure to ensure there are no voids inside the solid.
Once the nylon 102 is in-place, the heat pipes 105 and aluminum
metal foam 104 is inlaid into the titanium beta 21S metal casing
100.
[0022] Thus, following these steps, contact resistance can be
minimized, ensuring no hot spots form anywhere in the system.
[0023] The size of the aluminum 7075 metal foam 104 pores is also
crucial. The pores must be large enough to allow nylon to flow
through without being blocked by surface tension, and small enough
to ensure the nylon is heated evenly. The pores in the foam 104
must also be open, to allow liquids and gasses to flow through the
foam 104. The foam 104 is shaped to form fit into the casing 100,
to allow easy fitting when the system is cool.
[0024] Although the present invention has been described in
accordance with the embodiments shown, one of ordinary skill in the
art will readily recognize that there could be variations to the
embodiments and those variations would be within the spirit and
scope of the present invention. Accordingly, many modifications may
be made by one of ordinary skill in the art without departing from
the spirit and scope of the appended claims.
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