U.S. patent application number 11/439300 was filed with the patent office on 2007-01-18 for radiant heat pump device and method.
Invention is credited to Gordon D. Latos.
Application Number | 20070012433 11/439300 |
Document ID | / |
Family ID | 29584505 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070012433 |
Kind Code |
A1 |
Latos; Gordon D. |
January 18, 2007 |
Radiant heat pump device and method
Abstract
The present method and device is for configuring the geometry of
a surface to emit highly non-diffuse radiant energy. When a target
surface is placed in a region where it is targeted by the emitting
surface, there can be a net heat flow from the surface emitting the
radiant energy to the target surface, notwithstanding the target
surface may be at higher temperature than the emitting surface.
This method is employed in a radiant heat pump whereby the surface
for emitting energy radiation surrounds a target. The temperature
of the target, which is originally at a higher temperature than the
temperature of the surface, can have further temperature increases
as a result of the net heat flow thereby resulting in a useful
temperature increase in the target's temperature. The target may
then use the temperature increase to upgrade heat flowing through
the target for use in industrial processes.
Inventors: |
Latos; Gordon D.; (Calgary,
CA) |
Correspondence
Address: |
MACPHERSON KWOK CHEN & HEID LLP
2033 GATEWAY PLACE
SUITE 400
SAN JOSE
CA
95110
US
|
Family ID: |
29584505 |
Appl. No.: |
11/439300 |
Filed: |
May 22, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10447679 |
May 28, 2003 |
|
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11439300 |
May 22, 2006 |
|
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60383115 |
May 28, 2002 |
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Current U.S.
Class: |
165/185 ;
165/904 |
Current CPC
Class: |
F24V 99/00 20180501;
F28F 13/18 20130101 |
Class at
Publication: |
165/185 ;
165/904 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Claims
1. A method for exaggerating the nondiffuse emission pattern
radiating from a surface comprising the steps of: configuring the
composition, condition and geometry of the surface; and configuring
the density of the atmospheric environment in which the surface is
immersed.
2. A method as in claim 1 wherein the radiant heat flux flowing in
specific directions from the surface is more concentrated or less
concentrated than for an ordinary surface having the same
composition and temperature.
3. A method as in claim 2 wherein the apparent temperature of the
surface as perceived from specific directions is higher than or
lower than the actual temperature of the surface.
4. A method as in claim 3 wherein radiant heat is exchanged between
the surface, which is the emitting surface and a target surface,
the target surface located in a region where the apparent
temperature of the emitting surface is higher than the actual
temperature of the emitting surface.
5. A method as in claim 4 wherein there is a net flow of radiant
heat from the emitting surface to the target surface.
6. A method as in claim 4 further comprising the step of minimizing
the convective and conductive heat flow between the emitting
surface and the target surface.
7. A method as in claim 6 further comprising the step of minimizing
the convective and conductive heat flow between the emitting
surface and the target surface such that the combined heat flow by
conduction and convection between the surface and the target
surface is a small fraction of the net heat flow by radiation
between the emitting surface and the target surface.
8. A method as in claim 7 further comprising the step of entirely
surrounding or nearly entirely surrounding the target surface by at
least one emitting surface.
9. A method as in claim 5 further comprising the steps of supplying
heat to the emitting surface and removing heat from the target
surface.
10. A method for exaggerating the nondiffuse emission pattern
radiating. from a surface comprising the steps of configuring the
geometry of the surface to a V shape.
11. A method for conveying the apparent temperature of a surface to
a target surface where the actual temperature of the surface is
lower than the apparent temperature of the surface for ensuring a
net flow of radiant heat from the surface to the target surface,
comprising the steps of: configuring the geometry of the surface to
project nondiffuse radiant emission patterns into the region of the
target surface; and providing the material of the surface with a
highly reflective surface for improving the projection of
nondiffuse radiant emission patterns.
12. A method as in claim 11 wherein the geometry of the surface is
a V shape with the open end of the V toward the target surface.
13. A method as in claim 11 wherein the method further includes the
step of minimizing convective and conductive energy between the
surface and the target surface.
14. A method as in claim 11 wherein the method further includes the
step of introducing a partial vacuum between the surface and the
target surface for reducing convection.
15. A method for emitting radiant heat from a surface to a target
surface, the target surface having an actual temperature which is
higher than the actual temperature of the surface but lower than
the apparent temperature of the surface for achieving a net flow of
radiant heat to the target surface comprising the steps of:
configuring the geometry of the emitter's surface to project
nondiffuse radiant emission patterns; providing the emitter surface
with a highly reflective surface for improving the projection of
nondiffuse radiant emission patterns; and minimizing convective and
conductive energy between the surface and the target surface.
16. A method as in claim 15 further including the step of using a
non-reflective target surface for maximizing the radiant heat
absorbed by the target surface.
17. A method for transferring radiant heat from outside an
enclosure to a target within the enclosure where the temperature of
the target is higher than the temperature outside the enclosure,
comprising the steps of: providing a surface in the enclosure in
communication with heat energy outside of the enclosure for
radiating heat to the target, the surface having a highly
reflective surface for improving the projection of nondiffuse
radiant emission patterns; configuring the geometry of the surface
to project nondiffuse radiant emission patterns toward the target;
and minimizing convective and conductive energy flow between the
surface and the target surface.
18. A method as in claim 17 further including the step of
surrounding the target with surfaces.
19. A method as in claim 18 where the outside of the enclosure
forms the outside surface of the target of a larger similar
enclosure with otherwise the same features.
20. A method for recycling waste heat in a generation plant
comprising the steps of installing at least one radiant heat pump
in the generation plant for absorbing heat outside the radiant heat
pump to transmit heat to a target within the heat pump where the
target is at a higher temperature than the temperature outside the
heat pump.
21. A radiant heat pump for transferring heat comprising: a surface
for emitting energy radiation; a target surface in communication
with the surface for receiving energy from the surface, the target
surface having a higher temperature than the surface; and the
surface having a geometrically modified surface for projecting
nondiffuse radiant emission patterns towards the target
surface.
22. An apparatus for transfer of radiant energy between the
emitting surface and a target surface where the net transfer of
energy is more favourably in the direction of emitter-to-target
than expected based upon the mere differential between the
emitter's temperature and the target's temperature, comprising: a
surface for emitting energy radiation; a target surface in
communication with the surface for receiving energy from the
surface, the target surface having a higher temperature than the
surface; and the surface having a geometrically modified surface
for projecting nondiffuse radiant emission patterns towards the
target surface.
23. The heat pump of claim 21 with the following added elements:
means to deliver external heat to the emitting surface; and means
to remove heat from the target surface to outside of the
device.
24. A radiant heat pump as in claim 21 wherein the surface has a
polished metallic surface for improving the projection of
nondiffuse radiant emission patterns.
25. A radiant heat pump as in claim 21 wherein the convective and
conductive transfer of energy between the surface and the target
surface is minimized.
26. A radiant heat pump as in claim 21 wherein the geometry of the
surface is a V shape.
27. A radiant heat pump as in claim 21 wherein the surface
surrounds the target surface.
28. A radiant heat pump as in claim 21 wherein a second emitting
surface surrounds the surface for projecting nondiffuse radiant
emission patterns towards the surface.
29. A radiant heat pump comprising: a hollow emitter assembly
defining a vacuum sealed enclosure; a hollow cylindrical target
disposed through the hollow emitter assembly for collecting
radiation and for transporting the associated energy to the
exterior of the emitter assembly; and the emitter assembly having a
plurality of emitting plates on the emitter assembly's inner
surface, the emitter plates facing the hollow cylindrical target
and the emitter plates having a smooth surface for reflecting
radiation emitted from the emitter assembly to the emitter plates
to the hollow cylindrical target as a nondiffuse radiant
emission.
30. A radiant heat pump as in claim 28 wherein adjacent emitter
plates form a V shape.
31. A radiant heat pump as in claim 28 wherein a second emitter
assembly having internal emitting surfaces surrounds the hollow
emitter assembly for projecting nondiffuse radiant emission
patterns towards the emitter assembly.
32. A radiant heat pump comprising: an inner hollow emitter
assembly defining a vacuum sealed enclosure; an outer hollow
emitter assembly in communication with a heat source, the outer
hollow emitter assembly concentrically enclosing the inner emitter
assembly for transferring heat to the inner emitter assembly; a
hollow cylindrical target disposed through the inner emitter
assembly for absorbing heat from the inner emitter assembly and for
transporting the absorbed heat outside of both emitter assemblies;
each emitter assembly having a plurality of emitting plates on each
emitter assembly's inner surface, the emitter plates on the inner
surface of the inner emitter assembly facing the hollow cylindrical
target and having a smooth surface for reflecting heat emitted from
the inner emitter assembly to the emitter plates to the hollow
cylindrical target; and the emitter plates on the inner surface of
the outer emitter assembly facing the inner emitter assembly and
having a smooth surface for reflecting heat emitted from the outer
emitter assembly to the emitter plates of the inner emitter
assembly for increasing heat flow to the inner emitter assembly
thereby increasing heat flow by radiation to the hollow cylindrical
target.
33. A radiant heat pump comprising: an outer element with an inner
surface and an outer surface, a first end and a second end; an
inner element within said outer element; a plurality of V-shaped
emitting units disposed about the inner surface of said outer
element, said emitting units being capable of emitting radiant heat
towards said inner element; an end cap disposed at each end of said
outer element, and connecting said outer element and said inner
element; a fluid within said inner element, capable of transmitting
heat away from said inner element; a vacuum disposed between said
outer element and said inner element, and a fluid disposed about
said outer element.
34. A radiant heat pump as in claim 32 wherein said outer element
is an elongated cylinder and said inner element is an elongated
cylinder concentric with said outer element.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of U.S.
application Ser. No. 10/447,679 filed May 28, 2003, claiming
priority from U.S. application Ser. No. 60/383,115 filed May 28,
2002, the contents of which are incorporated herein by reference in
their entireties.
FIELD OF THE INVENTION
[0002] The invention relates to the field of radiant energy
devices, heat transfer devices and methods and more particularly
heat pumps.
BACKGROUND OF THE INVENTION
[0003] In industrialized countries, energy consumption is a
fundamental aspect of commerce and personal daily life. Global
energy use is rising rapidly as other nations advance toward
economic parity with the industrialized world.
[0004] Until recently, the significant, observable negative
consequences of fossil fuel consumption were limited to relatively
localized effects such as smog and acid rain. Now the majority of
scientists believe that even current consumption levels are
contributing to changes in global climate which pose a high risk
for the future stability of the biosphere. This situation will
worsen as consumption continues to grow.
[0005] The Kyoto Accord is the first international agreement
intended to minimize the climate change impact of fossil fuel
consumption by reducing the net emissions of carbon dioxide and
other greenhouse gases (GHGs). To succeed, such initiatives must be
supported by technologies which eliminate or significantly reduce
the GHG emissions associated with fossil fuels. Alternative energy
technologies, such as wind, solar and nuclear have made and
continue to make energy supply contributions at or near zero
emissions. However, it will be decades before such alternative
energy technologies displace fossil fuels sufficiently to tip the
GHG balance. In the interim, measures to increase the efficiency of
energy use and fossil fuel conversion can help reduce GHG
emissions.
[0006] Fossil fuels (primarily coal) are burned to generate a large
fraction of the total electricity used worldwide. Consumption rates
vary widely, but in North America, the monthly CO.sub.2 emissions
associated with domestic electricity use averages roughly three
tonnes per household. Some geographic regions have coal reserves
which are expected to last more than a century. Consequently, there
is great incentive to continue burning coal despite its
contribution to GHG emissions. Unfortunately, the steam cycles on
which conventional coal-fired generating plants are based run at
net efficiencies below 40%. Most of the energy is released as waste
heat into the environment when the steam is condensed.
[0007] As a result of trying to address these concerns and as a
result of rising energy costs, consumers at the industrial,
commercial and residential levels are seeking ways to reduce the
quantities of energy they purchase and consume. One method that has
been exploited with some success in the last decade is the recovery
and reuse of waste heat. Systems which harvest "free" renewable
energy from the atmosphere, ground and large bodies of surface
water have also become more common. Using the example above, such a
system could recover energy from the effluent of a coal burning
generation plant to reduce waste heat.
[0008] The prior art teaches the recovery of waste heat using
passive heat exchange, chemical heat pumps, and vapour compression
heat pumps (open or closed cycle heat pumps).
[0009] A brief discussion of each of these prior art systems and
their deficiencies is as follows:
[0010] When the temperature of a waste heat source is high enough
to be reused directly, passive heat exchange is almost always the
most economic method of recovery. However, most waste heat sources
are well below the temperature at which a need for energy exists
elsewhere. Consequently, the scope for application of passive heat
recovery is extremely limited. Industrially, most of these sources
have already been exploited.
[0011] Chemical heat pumps are limited to applications involving
temperature ranges at which certain chemical reactions proceed at
favourable rates. This limits both the number of installations for
which the technology is economic, and the flexibility of each
installation to economically accommodate variations in operating
conditions. Because of the nature of the chemicals used, chemical
heat pumps are also undesirable for some applications. Perhaps the
only advantage that chemical heat pumps enjoy over their vapour
compression counterparts is the fact that their requirement for
motive (electrical) energy input is a very small fraction of the
total energy input.
[0012] By far the largest number of operating heat pumps in the
world are vapour compression heat pumps. Almost all vapour
compression heat pumps are closed cycle units which recirculate a
refrigerant continuously around a closed loop. The most common
example of a vapour compression heat pump is the refrigerator.
[0013] The major problems with vapour compression heat pumps lie in
compressor technology (which is the heart of the vapour compression
pump) and the availability of suitable refrigerants.
[0014] More specifically, vapour compression heat pumps have
historically been considered unreliable and are complex thereby
requiring maintenance. Many manufacturing companies are preoccupied
with production-related equipment and therefore do not readily
accept peripheral equipment that might not work or cause
operational problems to other operating industrial systems.
Further, manufacturing companies do not want peripheral equipment
which requires specialized maintenance skills.
[0015] Another problem specifically with closed cycle vapour
compression heat pumps is the necessity of handling, maintaining
and using suitable working fluids (refrigerants). Working fluids
may be chemically unstable at temperatures high enough to be of
interest, uneconomical or even hazardous (explosive or toxic or
both).
[0016] Open cycle heat pumps avoid the refrigerant problem
associated with closed cycle units because they use the industrial
process fluid as the refrigerant. This eliminates the need for heat
exchange with a captive working fluid. However, there are several
factors which severely limit the range of applicability for open
cycle units. For example, process liquids are sometimes corrosive
or otherwise difficult to handle, maintain and use which adds to
the compressor cost. Further, process liquids are frequently
mixtures of liquids which evaporate at different temperatures and
complicate the cycle. Still further, process liquids frequently
contain dissolved or suspended solids, which complicates some
installations or makes them unworkable. Finally, open systems are
not well suited to heat recovery from waste liquids as
contamination of the working vapour with air is difficult to avoid
and thereby limits cycle efficiency and economic
attractiveness.
[0017] Open cycle heat pumps at high temperatures are subject to
the same compressor problems as their closed cycle counterparts.
Both open and closed cycle systems are subject to the limitation
that a substantial amount of high cost electrical energy is
required for vapour compression. For economic closed cycle systems,
the electrical energy input can constitute up to one half of the
total high temperature energy that the unit delivers. For well
designed open cycle systems, the electrical energy input can be as
little as 7 or 8% of the delivered heat. The cost of electricity
relative to the costs of other energy sources is a major factor in
determining the economic viability of a vapour compression
installation.
[0018] There is consequently a need for a method of conserving
energy which improves the current art of heat transfer devices by
providing a simple device and method for heat transfer which does
not require vapour compression or chemical reactions to recover
energy from waste heat sources, and which achieves meaningful and
useful temperature rises.
SUMMARY OF THE INVENTION
[0019] It is an object of the present invention to provide a method
and device for increasing energy efficiencies by recovering heat
which would otherwise be lost, and by raising the temperature of
the heat sufficiently to permit use of recovered energy.
[0020] The present invention provides a method for exaggerating the
nondiffuse emission pattern radiating from a surface by configuring
the geometry of the surface. This method can result in radiant heat
flux flowing in specific directions from the surface in a more
concentrated or less concentrated pattern than for an ordinary
surface having the same composition and temperature. Another result
of the method is that the apparent temperature of the surface as
perceived from specific directions is higher than or lower than the
actual temperature of the surface. Accordingly, if a receiving
surface or target surface is placed in a region where the apparent
temperature of the surface is higher than the actual temperature of
the surface then the result is a net flow of radiant heat from the
surface (or emitting surface) to the target surface.
[0021] The net flow of radiant heat transfer can be further
realized by minimizing the convective and conductive heat flow
between the surface and the target surface (such that the combined
heat flow by conduction and convection between the surface and the
target surface is a small fraction of the net heat flow by
radiation between the surface and the target surface).
[0022] While this method is effective for a surface emitting to a
target surface, one skilled in the art will appreciate that a
plurality of surfaces can be used to emit radiant heat to the
target surface. A worker skilled in the art will further appreciate
that the geometry of the surface or emitting surface can be
configured in various ways. In one method the geometry of the
surface is configured to a V shape with the opening of the V facing
the target surface. Still further, the surface can be made of
various materials. In one method the material is highly reflective
and in a more specific embodiment the surface is a highly polished
metallic surface.
[0023] In one embodiment, entirely surrounding or nearly entirely
surrounding the target surface by a continuous surface or a
plurality of surfaces further increases the effect of this method.
In this embodiment, by supplying heat to the emitting surface and
removing heat from the target surface, the present invention
provides a method for producing a useful radiant heat pump.
[0024] The concept of the radiant heat pump is based on the fact
that radiant heat exchange between two bodies involves an
independent and quantifiable flow of energy in each direction. This
distinguishes radiant heat transfer from both conduction and
convection, since at least on a macroscopic scale, conductive and
convective heat transfer are unidirectional along a gradient. By
producing an artificial environment in which the flow of radiant
energy from an emitting surface at one temperature to a receiving
surface at higher temperature is favoured over the reverse and
normally dominant flow, the invention proposes to establish a net
flow of radiant heat against a temperature differential.
[0025] One method of producing the artificial environment is to
modify the geometry of the emitting surface such that its apparent
temperature, from the perspective of the receiving surface, is
higher than its actual temperature. This may be achieved by
modifying the geometry of the emitting surface such that its
emissions are more focused and less diffuse, and by orienting the
emitting surface to emit a greater concentration of heat in the
direction of the receiving surface. The artificial environment can
be further enhanced by eliminating conductive and convective heat
transfer by introducing a vacuum, for instance, which will also
have the benefit of reducing scattering of the emissions and
interference with the radiant energy flow.
[0026] Radiant heat pumps overcome many of the major problems
associated with other prior art systems since radiant heat pumps
require no compressor or other complex machines, require no
chemicals or refrigerants, can operate well over a wide temperature
range, and can be assembled from a large number of identical
components which can be mass produced at low cost.
[0027] Another advantage of radiant heat pumps is that they require
electrical energy input only for pumping of the heat transport
fluids, and not for operation (as in thermoelectric devices) or
compression. Pumping of ordinary liquids is a very mature
technology that industry will have little difficulty implementing
efficiently.
[0028] The radiant heat pump involves no refrigerants or other
complex chemicals. Therefore, the practical and economic operating
temperature ranges are not limited by chemical properties. The
performance of each pump is determined by its geometry, the
characteristics of the emitter surfaces, and the quality of emitter
surface preparation. It appears that a radiant heat pump will
operate well over a far broader temperature range than prior art
heat pumps.
[0029] Perhaps the most important advantage of radiant heat pumps
is the fact that radiant heat transfer is enhanced by increasing
temperature. Since the rate of emission is proportional to the
fourth power of absolute temperature, the attractiveness of the
radiant heat pump over existing technologies will typically
increase with increasing source temperature.
[0030] In accordance with the methods describe above, the present
invention provides a radiant heat pump device for transferring heat
from a surface to a receiving or target surface where the target
surface has a higher temperature than the emitting surface. The
surface emits energy radiation towards the target surface. Further,
the surface is geometrically configured to project nondiffuse
radiant emission patterns towards the target surface. The result,
as apparent from the methods described above, is a net heat flow
from the emitting surface to the target surface against a
temperature differential.
[0031] In another embodiment of the radiant heat pump device, a
hollow emitter assembly defines a vacuum-sealed enclosure. Passing
through the hollow emitter assembly is a hollow cylindrical target
for collecting radiation and for transporting the radiation to the
exterior of the emitter assembly. The emitter assembly includes a
plurality of emitting plates on the emitter assembly's inner
surface, the emitter plates facing the hollow cylindrical target
and the emitter plates having a smooth surface for reflecting
radiation emitted from the emitter assembly to the emitter plates
to the hollow cylindrical target.
[0032] Other aspects and features of the present invention will
become apparent to those ordinarily skilled in the art upon review
of the following description of specific embodiments of the
invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Embodiments of the present invention will now be described,
by way of example only, with reference to the attached Figures,
wherein:
[0034] FIG. 1 is an emitter assembly including two emitter plates
each having an emitting surface in accordance with the
invention;
[0035] FIG. 2 is a top view of the emitter assembly in FIG. 1 which
demonstrates the reflection of emissions between two adjacent
plate-emitting surfaces in accordance with the invention;
[0036] FIG. 3 is a perspective view of an emitter assembly in
relation to a target in accordance with the invention;
[0037] FIG. 4 is a graph which demonstrates the ratio of focused
flux from an emitting surface compared to a theoretical blackbody
flux in accordance with the invention;
[0038] FIG. 5 is an emitter assembly in relation to a cylindrical
target in accordance with the invention;
[0039] FIG. 6a is a side view of one embodiment of the radiant heat
pump in accordance with the invention;
[0040] FIG. 6b is a cross sectional view of the radiant heat pump
in FIG. 6a taken at line A-A in accordance with the invention;
[0041] FIG. 6c is a cross sectional view of the radiant heat pump
in FIG. 6b taken at line B-B in accordance with the invention;
[0042] FIG. 6d is a cross sectional view of the radiant heat pump
in FIG. 6c taken at line C-C in accordance with the invention;
[0043] FIG. 7 is a cross sectional view of one embodiment of a
radiant heat pump in accordance with the invention; and
[0044] FIG. 8 is a system of radiant heat pumps in accordance with
the invention.
DETAILED DESCRIPTION
[0045] Those skilled in the art will know that unlike heat
conduction and convection, radiant heat transfer between two bodies
involves an independent, quantifiable flow in each direction.
Conventional theory on radiant heat transfer is based on an ideal
surface, known as the blackbody. The blackbody has a total emissive
power which is proportional to the fourth power of its absolute
temperature, emits uniformly (diffusely) in all directions, emits
with a characteristic, predictable wavelength distribution and
absorbs all radiant energy which is incident upon it.
[0046] A less idealized theoretical surface than a blackbody is
termed a graybody which also emits diffusely and with a
characteristic wavelength distribution. However, a graybody only
emits a fraction of the power of a blackbody; that fraction
(uniform for all wavelengths) is termed its emissivity. Conversely,
a graybody also absorbs only a fraction of the incident radiant
energy; that fraction (uniform for all wavelengths) is defined as
absorptivity (any incident energy not absorbed is reflected
diffusely). Further, for a graybody, absorptivity is generally
equal to emissivity.
[0047] Any two blackbodies or graybodies placed in line of sight
contact with each other will exchange radiant energy such that
their temperatures tend to converge. That is, if one body has a
higher temperature than the other body, then the amount of radiant
energy from the higher temperature body which is transmitted to the
lower temperature body will be greater than the amount of radiant
energy from the lower temperature body which is transmitted to the
higher temperature body.
[0048] In contrast with blackbodies and graybodies, real surfaces
have emissivities and absorptivities which vary with wavelength,
emit with distribution patterns that deviate to varying degrees
from truly diffuse, and have reflections that are partly specular
and partially diffuse. Accordingly, real surfaces will emit
different amounts, generally less, radiant energy than blackbody or
graybody surfaces.
[0049] The present invention provides a method and a device for
exaggerating the nondiffuse emission patterns of real surfaces by
making radiant emissions from the surfaces less diffuse than the
surfaces' normal emissions. As a consequence, the nondiffuse
emission patterns can be concentrated onto a receiving surface.
Further, there can be a net flow of radiant heat energy from a
lower temperature (emitting) surface to a higher temperature target
or receiving surface. As described below, this method, which is
contrary to the "normal" pattern considering that the vast majority
of surfaces radiate heat diffusely, facilitates the net transfer of
radiant heat energy to the receiving surface against a temperature
gradient, which has very valuable commercial uses.
[0050] In one embodiment of the method of exaggerating nondiffuse
emission patterns shown in FIG. 1, two emitter plates 16, which
each have the same dimensions and emitting surfaces 18, are placed
in contact along edges of equal length. Viewed in cross section
(FIG. 2), the line of contact forms the apex for a narrow,
elongated "V" shape. In this formation, the emissions from either
plate 16 flowing in the general direction of the opening at the top
of the V are confined and reflected by the opposing emitting
surface 18 of the plate 16 and are reflected back toward the
opening of the V.
[0051] The nature of the reflections of the emissions is of
particular interest. As shown in FIG. 2, the angle between a ray
and the axis of symmetry 30 is smaller after the reflection than it
is before the reflection, by an amount equal to the angle
separating the plates 16. In other words, each reflection is a sort
of focusing event. Depending on the geometry of the system and an
emission's location of origin, an emission may undergo several more
reflections before emerging from the opening of the V. If the
plates 16 are sufficiently smooth, only a trivial amount of
scattering takes place at each reflection. Consequently, a high
percentage of the original emission is reflected.
[0052] The cumulative effect of multiple reflections to numerous
emissions from the emitting surfaces 18 of this formation is a
roughly concentrated beam of radiant heat energy whose component
emissions approach with varying degrees of accuracy towards a
direction parallel to the axis of symmetry 30.
[0053] Due to the unique emissivity characteristics of metals, a
metal surface is preferable for the emitting surfaces 18. More
specifically, metals exhibit inverted emissivity characteristics
(which increase at low angles) and are far from diffuse. A highly
polished metal surface will result in even less diffusion upon
reflection of radiant heat energy.
[0054] The combination of polished metal emitting surfaces 18 into
certain geometries causes the combined emitting surfaces 18 to
project nondiffuse radiant emission patterns. When compared with
the radiant emission patterns produced by an ideal blackbody
emitter, the total emission of radiant energy from the emitting
surfaces 18 will naturally be equal to or less than the
corresponding total for the ideal blackbody with the same projected
area. However, the emitting surface 18 projects relatively higher
concentrations of radiant heat energy to specific regions and lower
concentrations to other regions. That is, the radiant flux density
projected along the axis of symmetry 30 for each emitting plate 16
pair is significantly higher than it would be in the case of
diffuse emission but the flux densities at large angles from the
axis of symmetry 30 are correspondingly lower. Accordingly, the
emitting surface 18 may achieve up to several times the equivalent
blackbody emission level for a target region and even greater
emissions when compared to a diffuse emitter.
[0055] Using the method described above and adding a target plane
20 which is perpendicular to the axis of symmetry 30 as shown in
FIG. 3, it is possible to concentrate a beam of radiant heat energy
from the emitting surface 18 on the target plane 20 (or a more
specific target 31 as shown in FIG. 5) which transmits more radiant
energy towards the target plane 20 than if the emitting surface 18
was a normal diffuse emitting surface (or an ideal blackbody
emitting surface).
[0056] The emitter assembly 14 is constructed so that the maximum
relative flux density from the emitter plates 16 is incident on or
near the target 31. Consequently, from the target's perspective,
the high radiant flux density makes the "apparent" temperature of
the emitter plates 16 higher than the emitter plates' actual
temperature. Since heat flow to the target 31 is based on the
apparent temperature of the emitting surface as perceived by the
target surface, the target 31 will absorb more heat emitted from
the emitter plates 16 than if the target 31 was able to perceive
the emitter plates' actual temperature. Accordingly, there will be
a net flow of heat to the target 31, notwithstanding that the
target 31 may be at a higher surface temperature than the surface
temperature of the emitter plates 16.
[0057] One method of maximizing heat transfer to a cylindrical
target is to increase the number of pairs of emitter plates 16
oriented to project focused emissions on the cylindrical target.
This method can be embodied in the radiant heat pump device
discussed below.
[0058] Another method to maximize the advantageous radiant transfer
from the emitting surface 18 to the target 31 is to minimize the
conductive and convective "back flows" that occur as a result of
the Zeroth Law. Conduction is minimized by limiting the
cross-sectional area available for transfer back from the target 31
to the emitter plates 16. Convection is minimized by maintaining a
vacuum between the emitting and target surfaces.
[0059] If undesirable heat losses by conduction and convection from
the target 31 are minimized then the following equations describe
the relationships between the temperatures of the target and
emitting surfaces and the rates of heat flow between the target and
emitting surfaces. RAD t = RAD e - CONV ( i ) Where .times. :
.times. .times. RAD t .times. .times. is .times. .times. the
.times. .times. rate .times. .times. of .times. .times. radiant
.times. .times. emission .times. .times. from .times. .times. the
.times. .times. target , .times. RAD e .times. .times. is .times.
.times. the .times. .times. rate .times. .times. of .times. .times.
radiant .times. .times. heat .times. .times. gain .times. .times.
by .times. .times. the .times. .times. target , .times. and .times.
CONV .times. .times. is .times. .times. the .times. .times. rate
.times. .times. of .times. .times. convective .times. .times. heat
.times. .times. removal RAD t + A t .times. E t .times. ST t 4 ;
.times. T t = ( RAD t / A t .times. E t .times. S ) 1 / 4 .times.
.times. Where .times. : .times. .times. E t .times. .times. is
.times. .times. the .times. .times. emissivly .times. .times. (
absorptivity ) .times. .times. of .times. .times. the .times.
.times. target , .times. S .times. .times. is .times. .times. the
.times. .times. Stefan .times. - .times. Boltzmann .times. .times.
constant , .times. A t .times. .times. is .times. .times. the
.times. .times. surface .times. .times. area .times. .times. of
.times. .times. the .times. .times. target , .times. and .times. T
t .times. .times. is .times. .times. the .times. .times. absolute
.times. .times. temperature .times. .times. of .times. .times. the
.times. .times. target . ( ii ) RAD e = RA t .times. SE t .times. T
e 4 .times. .times. Where .times. : .times. .times. R .times.
.times. is .times. .times. the .times. .times. ratio .times.
.times. of .times. .times. incident .times. .times. emissions
.times. .times. to .times. .times. blackbody .times. .times.
emissions , .times. and .times. .times. T e .times. .times. is
.times. .times. the .times. .times. temperature .times. .times. of
.times. .times. the .times. .times. emitter .times. .times. plates
.times. .times. Combining .times. .times. equations .times. .times.
i , ii , and .times. .times. iii , .times. and .times. .times.
setting .times. .times. E t = 1 .times. : .times. .times. T t = (
RA t .times. SE t .times. T e 4 - CONV A t .times. S ) 1 / 4 ( iii
) ##EQU1##
[0060] In the ideal case where: (1) the emitter assemblies 14 emit
with the power of blackbodies and (2) all emissions are incident on
the target 31, the maximum concentration ratio that could be
achieved would be fixed by the geometry of the emitter assemblies
14.
[0061] The particular shape and arrangement of the emitting
surfaces are variable. For instance, the V shape shown in the
figures may have various alternate configurations. More
specifically, the angle of the opening of the V shape (shown as
approximately 300 in FIG. 1) may be narrower or wider, the emitter
plates 16 may have varying widths and the emitter plates 16 may not
be planar. More generally, a V shape is not essential as other
geometric configurations (having a plurality of surfaces where some
surfaces may even emit diffusely) may achieve the same purpose of
exaggerating nondiffuse emission patterns to produce concentrations
of emitted energy toward a region or regions.
[0062] Using the above methods, it is possible to design a radiant
heat pump 10.
[0063] In one embodiment shown in FIGS. 6a, 6b, 6c and 6d, the
present invention provides a radiant heat pump 10 having a hollow
shell assembly 14 defining a vacuum sealed recess 15 and a hollow
cylindrical target 12 disposed through the emitter assembly 14 for
collecting energy by radiation and for transporting the collected
energy to the exterior of the shell assembly. In this embodiment
the shell assembly 14 includes a plurality of emitting plates 16 on
the shell assembly's inner surface 17, the emitter plates 16 facing
the hollow cylindrical target 12 and the emitter plates 16 having a
smooth active radiant surface or emitting surface 18 for reflecting
radiation transferred from the shell assembly 14 to the emitter
plates 16 and then by radiation to the hollow cylindrical target
12. The radiant heat pump 10 is designed to enclose a vacuum such
that conductive and convective heat transfer effects are
insignificant when compared to radiant heat transfer although any
means of minimizing conductive and convective heat transfer will be
effective.
[0064] Although this embodiment is shown in two dimensions for the
sake of simplicity, a 3-D symmetry may also be used. For example,
in another embodiment, the emitter assembly 14 may be spherical and
the emitter plates 16 may define conical recesses for radiating
focused emissions on a target 12 which, in such an embodiment, may
also be spherical. A worker skilled in the art will appreciate that
other two-dimensional and three-dimensional shapes will be
effective.
[0065] In another or further embodiment, one skilled in the art
will appreciate that the shell assembly 14 may be nested as shown
in FIG. 7. That is, concentric shell assemblies (such that the
outer surface of one shell assembly forms the collector in another
shell assembly, and so forth) may be provided around the hollow
cylindrical (or spherical) target 12. Since emissive power is
proportional to the fourth power of absolute temperature, higher
source temperatures provided to the inner emitter assembly from the
outer emitter assembly would make a radiant heat pump 10 more
effective in terms of temperature lift to the target 12.
[0066] In general operation, the radiant heat pump 10 is installed
in an environment such as a generating plant or other energy
facility where heated liquid or steam is in contact with the
outside of the radiant heat pump. Typically the liquid or steam is
not at a high enough temperature for further use in the generating
plant without upgrading the temperature (that is, the heat is waste
heat). As the heat or heated water comes into contact with the
radiant heat pump 10, the exterior of the shell assembly 14 absorbs
the heat and transmits the heat to the interior surface 17 which
includes emitter plates 16. Simultaneously, water or other heat
energy removal means flows through the hollow cylindrical target
12. As a result of using the methods described above to modify the
emitting surface 18 of the emitter plates 16 and to modify the
geometries of the emitter plates 16 to exaggerate the nondiffuse
emission patterns of the emitter plates 16, the apparent
temperature of the emitter plates 16 from the perspective of the
cylindrical target 12 is greater than the actual temperature of the
emitter plates 16, resulting in the cylindrical target 12 absorbing
more heat than if cylindrical target 12 perceived the actual
(lower) temperature of the emitter plates 16. Accordingly, there is
a net flow of energy by radiation to the cylindrical target 12
which can raise the temperature of the cylindrical target 12 to a
useful temperature, notwithstanding that the cylindrical target 12
is at a higher temperature than emitter plates 16.
[0067] The emitter plates 16 may be long thin components formed,
for example, by machining, forging, stamping, die casting or
investment casting. The material used is preferably strong, rigid,
and economical, with a high thermal conductivity. In descending
order of thermal conductivity, copper, aluminum and steel are among
the best common options currently available. If plastics, or
composites with sufficient strength and rigidity at high
temperature exist in combination with adequate thermal
conductivity, durability and very low gas permeability, they can
also be used to construct the emitter plates 16. These composites
may have a strength to weight advantage over metals. Suitable
plastic forming techniques for forming the emitter plates include
rotomolding, thermoforming, and if components are small enough,
possibly also injection molding.
[0068] The emitter plates 16 are preferably solid and designed to
direct a substantial portion of emitted heat to the hollow
cylindrical target 12. A worker skilled in the art will appreciate
that the emitter plates 16 may be machined in one continuous piece
thereby forming one continuous surface around the hollow
cylindrical target 12.
[0069] The active radiant surface or emitting surface 18 is
preferably very smooth. Due to the advantageous properties of
polished metal with respect to reflectivity described above, the
emitter plates 16 are preferably comprised of or coated with a
polished metal surface 18.
[0070] Numerous design changes to the emitter plates 16 are
conceivable. For instance, the emitter plates 16 may be curved and
the emitter plates 16 may include combinations of diffuse emitting
materials and polished metals or other highly reflective materials.
As stated above, the particular shape and arrangement of emitting
surfaces generally (and specifically the emitter plates 16 in this
case) is variable.
[0071] In addition to the emitter plates, the radiant heat pump 10
may include reflecting surfaces at each end of the cylindrical or
spherical or other emitting surface 18 made of either flat or
curved highly reflective material. Alternatively, each end of the
emitter assembly 14 may include emitting surfaces 18 made of either
flat or curved surfaces that emit diffusely. Still further, the end
caps 22 may be composed of combinations of materials which emit
diffusely and are highly reflective.
[0072] In the embodiments described above, it is also possible to
achieve refractive enhancement with materials that transmit the
wavelengths of interest, if the effect of the materials used and
the geometries designed is to concentrate radiated energy from an
emitter to a region including a collector.
[0073] The hollow cylindrical target 12 is used to transfer heat
absorbed by the target outside of the shell assembly 14 and on to a
heat delivery system (usually through fluid flowing through the
hollow cylindrical element which is heated to a useful temperature
by absorption from the collector's surface). This upgraded energy
can then be reused in a system (such as in FIG. 8) to achieve the
objective of conserving energy, recovering waste energy and
reducing costs.
[0074] The hollow cylindrical target 12 is preferably not
reflective (that is, the surface of the hollow cylindrical target
12 should be highly absorptive to maximize the net heat flow to the
hollow cylindrical target 12). To achieve useful results, the
surface area of the hollow cylindrical target 12 should be smaller
than the apparent or effective surface area of the emitter plates
16.
[0075] The artificial environment between the emitter assembly 14
and the hollow cylindrical target 12 can help maximize the net flow
of heat to the hollow cylindrical target 12 through the
minimization of any back flow (from target to emitter) by
conduction or convection. This may be done, for instance, by vacuum
sealing the emitter assembly 14 and minimizing contact of emitter
and target by (for instance) providing heat insulation between
those elements where they necessarily contact each other or
intermediate mounting means.
[0076] General immediate uses for the present invention are:
[0077] 1. waste energy recovery and upgrading, and process heat
transfer in industrial and large commercial applications, and
[0078] 2. condensing heat recovery from thermal power stations.
[0079] In addition to those areas in which the radiant heat pump
will out-perform competitive technologies, the present invention
can be used in thermal-electric generating stations which currently
waste approximately 40% of the total energy input by rejecting the
energy input as low temperature heat, usually to a nearby body of
water. This waste is the result of a thermodynamic limitation of
the cycle used to convert heat into mechanical energy. Steam is
condensed at the outlet of each turbine and pumped back up to high
pressure as water. To maximize the efficiency of the generating
cycle, this heat is rejected at as low a temperature as possible
and is not worth recovering. Radiant heat pumps could be used to
recover some of this rejected waste heat for re-injection into the
process to greatly increase the overall efficiency of the plant. To
optimize the recovery system, the discharge temperature from the
steam turbines would be increased from the normal ambient
temperature to perhaps 300 degrees C. The resulting small loss in
efficiency of the existing cycle would be more than offset by the
recovered heat. As already discussed, none of the existing heat
exchange technologies are capable of effectively dealing with a
source at this high temperature.
[0080] The availability of the present invention, particularly to
industry, may result in industry-specific applications that do not
currently exist. As an example, in exchanging heat between two
flows it might be advantageous to transfer up in temperature rather
than down as is currently the case with passive heat exchange.
Depending on the cost of production of the present invention, the
present invention may, for example, ultimately find application in
building space heating (using ambient or very low temperature
sources) or refrigeration.
[0081] One method of manufacturing and assembling a radiant heat
pump is as follows:
[0082] After rough forming of the metallic components of the
emitter plates 16, the mating surfaces that permit accurate
relative positioning of adjacent emitter plates 16 are machined to
high accuracy (.about.+0.005'' or better). This precision is
economical and practical with the current generation of computer
numerically controlled (CNC) machining technology. Locating
features such as tabs for position keying and grooves for vacuum
sealing elements between emitter plates 16 may be added during the
machining operation. In the same machining operation, or in a
separate machining or grinding operation, the surfaces of the
emitter plates 16 that participate in the radiant exchange are
finished to a high quality. The quality of surface finishing
required for economical performance of the radiant heat pump, and
the effect of directional surface markings left by machining or
grinding on operation of the heat pump is determined empirically,
and depends upon the material chosen and the method of manufacture.
However, if a higher surface quality of the metal emitter plates 16
is required, it may be produced by secondary operations such as
lapping and/or electropolishing.
[0083] Once each emitter has the correct shape, the emitting
surfaces 18 are coated with a thin film (likely <0.002'') of an
appropriate material. Currently, the preferred materials are
chromium or aluminum, however other materials that later prove to
be more suitable are intended to be included herein. The coating
technique depends upon economics, with a preference for the most
economical coating method that provides acceptable radiant and
reflective properties to the emitting surfaces 18. Electroplating,
which would be used for metals only, and vapour deposition are
among the most likely candidates for coating techniques.
[0084] If plastics or composites are used, the molding processes
may be designed to minimize the amount and cost of work required
after forming the emitter plate 16. In particular, polished molds
used with high performance release agents might deliver active
surface qualities ready for the final coating.
[0085] Prior to assembly into the radiant heat pump 10, the emitter
plates 16 are cleaned thoroughly and taken to an assembly area
which meets clean room standards, not unlike those used for
manufacture of microelectronics. Completed emitter plates 16 are
then stacked into cylindrical assemblies by placing them next to
each other one unit at a time, and engaging the locating features
until groupings spanning 180.degree. of arc are complete.
[0086] The next step in the assembly of the emitter assembly 14 is
to combine two half shells into a full cylindrical array of emitter
plates 16. The final step is to strap the array together with
external hoops of metal or composite material. Vacuum sealing
elements may be placed between emitters individually during
assembly, or pumped through the sealing grooves in the entire array
during a single step after strapping. In the latter case, the
sealing material will harden to a rigid state that provides
additional mechanical stability to the emitter assembly 14, and
helps to bond its components together. After bonding, straps may no
longer be necessary. A sealing agent applied externally on the
emitter assembly 14 may further limit gas diffusion.
[0087] End caps 22 of machined metal or a composite material would
complete each enclosure and its vacuum seals. The end cap 22 inner
surfaces are preferably highly reflective to infrared wavelengths.
The end caps 22 also provide the connection point for vacuum lines
(not shown), and possibly for reducing gases that would be flushed
through each chamber to accelerate the removal of surface oxide
prior to startup. As an additional requirement, each end cap 22
would provide a barrier to minimize thermal conduction between the
shell assembly 14 and the target 12 passing through its central
port. At least one of the two end cap-to-target joints would be
allowed to slip relatively freely so that differential thermal
expansion of the target 12 would not place it in compression. Both
would be thermally isolated such that the target 12 is thermally
insulated (for conduction) from the shell (and thus the
emitters).
[0088] The hollow cylindrical target 12 may be a thin walled tube
with a thickness to diameter ratio <0.1 and with sufficient
strength and rigidity to withstand the internal pressure of a fluid
medium that flows through the target 12 and conducts high
temperature heat away from the radiant heat pump. The target 12
must also be sufficiently rigid to maintain its concentricity in
the assembly to an acceptable accuracy. Highly conductive metals,
such as copper are potential materials from which the target 12 may
be comprised, however other materials are not intended to be
excluded if they function as required in this invention. The
convective performance inside the targets 12 may be enhanced by
providing the interior of the target 12 with turbulence inducing
inserts, or by surface roughening of the interior wall of the
target 12. The outside surface of each target 12 will be coated
with a material having a very high infrared absorbtivity.
[0089] Overall, the geometric parameters of the radiant heat pump
10 of this invention will preferably include:
[0090] 1. an emitter plate 16 separation angle of approximately
3.degree. to 12.degree.;
[0091] 2. an emitter assembly 14 length to diameter ratio in the
range of 2:1 to 6:1; and
[0092] 3. a ratio of shell assembly 14 inner diameter/target 12
outer diameter of between 10:1 and 50:1.
[0093] If the rigidity of a composite or metal emitter assembly 14
assembled according to the above methods proves inadequate, the
emitter assembly 14 may be reinforced with an external metallic
frame (not shown). This approach may prove to be more economical
than the use of metallic emitter plates 16, particularly in the
case of composite emitters.
[0094] The above-described embodiments of the present invention are
intended to be examples only. Alterations, modifications and
variations may be effected to the particular embodiments by those
of skill in the art without departing from the scope of the
invention, which is defined solely by the claims appended
hereto.
* * * * *