Note: Descriptions are shown in the official language in which they were submitted.
1
THERMAL SUPERCONDUCTOR REFRIGERATION SYSTEM
TECHNICAL FIELD
The present invention relates generally to refrigeration systems, and more
particularly to a refrigeration heat exchanger having an efficient
superconducting heat
transfer element.
BACKGROUND OF THE INVENTION
Limitations of current art
Commercial refrigeration systems typically use a phase-change refrigerant
to absorb heat from an interior space and move it to an exterior space where
it can be
rejected. The refrigerant in these typical systems is circulated in a
refrigerant loop
connecting a refrigerating heat exchanger (or "evaporator") which absorbs heat
from a
space to be cooled, a compressor which intensifies this heat, and a heat
dissipating
heat exchanger (or "condenser") which dissipates the heat either into the
outside
environment or into a building mechanical system that requires heat, such as a
domestic hot water system.
In a typical application such as a walk-in freezer with a roof-top heat
dissipating heat exchanger, the refrigeration process works in the following
manner.
Liquid refrigerant flows through the refrigerant loop and into the evaporator
where it
rapidly drops in temperature as it expands to fill the larger volume of the
evaporator,
becoming a supercooled partial liquid. As the droplets in the partial liquid
contact the
inner surfaces of the evaporator coil they absorb heat and rapidly evaporate,
cooling the
surfaces of the evaporator to a temperature lower than the air in the freezer.
The
cooled surfaces then absorb heat from the air as it is drawn across the
surfaces by a
fan. The cooled air then returns to the space, cooling the space. The
evaporated
refrigerant then flows out of the evaporator, through the refrigerant loop,
and into the
compressor where it is compressed, causing the heat contained in the vapor to
be
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intensified. The hot vapor then flows through the loop to the roof-top
condenser which
becomes hot. Air drawn across the outer surfaces of the condenser absorbs this
heat
and carries it off into the atmosphere. This loss of heat causes the
refrigerant vapor to
condense into a liquid. The liquid refrigerant then flows back to the
evaporator to begin
the heat removal process again.
Many variants of this process have been developed to serve different
refrigeration requirements, but the process remains essentially the same. In
some
systems, the roof-top heat dissipating heat exchanger is replaced with a heat
exchanger
inside the building, with air ducts coming into and going out of the building
for the
purpose of rejecting heat into the outside atmosphere. In other systems, the
roof-top
heat exchanger is replaced with a refrigerant-to-water heat exchanger inside
the
building, which transfers heat from the refrigerant loop to a water loop, such
that heat
can be rejected into an outdoor evaporation pond or used by a building
mechanical
system to provide hot water for space heating or domestic hot water purposes.
Similarly, the refrigerating heat exchanger can absorb heat from a liquid such
as water
in an ice making machine instead of from the air in a space. In these
variations, the
method of heat exchange at the refrigerating and dissipating heat exchangers
varies,
but the refrigeration circuit remains the same. Typically, the characteristic
rating of the
refrigerant is matched to the application.
In large refrigeration systems, this process has a number of inherent
problems and inefficiencies:
Commercial refrigerators are often large and far away from the
refrigeration plants that serve them, so the loops are often very long and
have large
volumes of refrigerant and large numbers of connections and valves, which
makes them
vulnerable to leaks and causes them to require frequent maintenance of
components.
The complexity of large circulating refrigerant systems makes it difficult for
the heat absorbed in one refrigerator to be used to defrost the heat exchanger
in
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another or to supplement other building mechanical systems requiring heat.
This
results in low energy efficiency.
The movement of refrigerant over long distances requires significant
pumping energy, which decreases system energy efficiency.
In the refrigeration cycle, cold refrigerant passes through loops in the
evaporator, absorbing heat from the evaporator as it passes through. As a
result, each
loop naturally has a temperature gradient - colder at the refrigerant inlet
and warmer at
the refrigerant outlet. This means that parts of the evaporator are warmer
than others,
making them less able to absorb heat from the air, resulting in lower
evaporator
efficiency, and requiring an increase in heat exchanger size to compensate.
In air-to-refrigerant heat exchangers used in the refrigeration mode, the
cooling process causes moisture from the air to condense and freeze on the
surfaces of
the closely packed fins and tubes that make up the evaporator. Eventually this
ice build-
up blocks air-flow through the evaporator, reducing efficiency.. When
efficiency drops
below an acceptable level, the ice must be removed through a defrost cycle,
most
commonly achieved by reversing the refrigeration system to provide heating
instead of
cooling to the refrigerating heat exchanger.
Defrosting results in three problems. First, the reversing valves used to
reverse the flow of refrigerant in the system are inefficient and prone to
failure. Second,
the reversal of the system from refrigeration to defrost causes refrigerant to
behave
differently from it's prior phase at a location in the loop, condensing where
it previously
evaporated, evaporating where it previously condensed; compensating for these
changes in behavior requires additional system complexity, cost and
maintenance.
Second, frequent cycling from cold to hot causes stress on connections which
causes
leaks. Third, the defrost cycle requires the whole refrigeration system to be
stopped,
gradually reversed to minimize heat stress, operated in reverse long enough to
defrost
the refrigerating heat exchanger, stopped, and then gradually reversed to
minimize heat
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stress before returning to the refrigerating mode; this creates a transition
time, and
during this time the space is not being refrigerated, leading to a rise in
space
temperature that must be compensated for with high levels of refrigeration
energy when
the refrigeration mode becomes operational again, causing the whole
refrigeration
system to require higher refrigerating capacity than would be necessary with
shorter
defrost times. Other systems have been developed to achieve shorter defrost
times
but each has inherent problems. Electrical resistance strip heaters for
example, have
been mounted to the face of evaporator coils, allowing the primary
refrigeration system
to simply stop while the secondary electrical system provides defrost energy.
These
strip heaters are prone to burning out, requiring frequent replacement which
can only be
efficiently done if the strips are mounted to the accessible face of the
evaporator unit.
This causes them to be inefficient because they are far away from the ice
mass, which
at the core of the evaporator.
There is a need for an efficient refrigeration system that operates without a
refrigerant transfer loop, utilizes much less power than conventional
refrigerators, has
smaller heat exchangers, has an extended lifetime due to fewer parts, uses
less
refrigerant, has a shorter and more efficient defrost cycle and provides
enhanced
refrigeration efficiency compared to power used. There is further a need for a
non-
refrigerant based defrosting element used in combination with a conventional
refrigeration system.
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SUMMARY OF THE INVENTION
According to one aspect of the present invention, a superconductor
refrigeration system having thermal superconducting heat transfer is provided.
The
system includes;
a) an intensifying heat exchanger, having a refrigerant coil which receives
refrigerant in the heating and cooling cycle, further including;
i. a condenser heat exchange segment of the coil
ii. an evaporator heat exchange segment of the coil
iii. means to expand liquid refrigerant to partial liquid and located
between the exchange segments
iv. compressor for compressing and circulating a refrigerant in the
refrigerant coil;
b) a refrigerating heat exchange coil formed from thermal superconductor
material, having a transfer segment terminating at opposing ends at,
a refrigerating heat exchange segment,
a refrigeration switch segment;
c) a dissipating heat exchange coil formed from thermal superconductor
material,
having a transfer segment terminating at opposing ends at,
a dissipating heat exchange segment,
a dissipating switch segment;
d) a 2-way thermal switch connected to condenser and evaporator heat
exchange segments, the refrigeration switch segment and the dissipating switch
segment such that in a first switch position the dissipating switch segment is
thermally
coupled to the condenser heat exchange segment and the refrigeration switch
segment
is thermally coupled to the evaporator heat exchange segment to provide a
refrigerating
mode, and in a second switch position the dissipating switch segment is
thermally
coupled to the evaporator heat exchange segment and the refrigeration switch
segment
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is thermally coupled to the condenser heat exchange segment to provide a
defrost
mode.
According to another aspect of the present invention, a superconductor
refrigeration
system having thermal superconducting heat transfer is provided with a
plurality of
thermal switches. The system includes;
a) an intensifying heat exchanger, having
i. a refrigerant coil which receives refrigerant in the heating and cooling
cycle
ii. a condenser heat exchange segment of the coil
iii. a evaporator heat exchange segment of the coil
iv. evaporating means to expand liquid refrigerant to partial liquid and
located between the exchange segments,
v. compressor means for compressing and circulating a refrigerant in the
refrigerant coil;
b) a-refrigerating heat exchange coil formed from thermal superconductor
material, having a transfer segment terminating at opposing ends at;
a refrigerating heat exchange segment,
a refrigeration switch segment
c) a dissipating heat exchange coil formed from thermal superconductor
material,
having a transfer segment terminating at opposing ends at,
a dissipating heat exchange segment,
a dissipating switch segment
d) a dissipating thermal switch-connected to condenser and evaporator heat
exchange segments and the dissipating switch segment, such that in a first
switch position the dissipating switch segment is thermally coupled to the
condenser heat exchange segment to operate in a refrigerating mode, and in a
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second switch position the dissipating switch segment is thermally coupled to
the
evaporator heat exchange segment to operate in a defrosting mode;
e) a heat exchange thermal switch connected to condenser and evaporator heat
exchange segments and the refrigerating switch segment, such that in a first
switch position the refrigeration switch segment is thermally coupled to the
evaporator heat exchange segment to operate in a refrigerating mode, and in a
second switch position the refrigeration switch segment is thermally coupled
to
the condenser heat exchange segment to operate in a defrost mode;
and the dissipating thermal switch and the heat exchange thermal switch are
switched
to provide corresponding refrigerating or defrosting modes of the
superconductor
refrigeration system .
According to another aspect of the present invention, a superconductor
refrigeration
system having thermal superconducting heat transfer is provided using a
reversing
valve. The system includes;
a) a reversible intensifying heat exchanger, having
i. a compressor;
ii. a first heat exchanger and a second heat exchanger, each of the
heat exchangers adapted to function interchangeably as an
evaporator and a condenser, such that the first heat exchanger is
operable as an evaporator and the second heat exchanger is
operable as a condenser when the system is operating in cooling
mode, and such that the first heat exchanger is operable as a
condenser and the second heat exchanger is operable as an
evaporator when the system is operating in heating mode;
iii. at least one first conduit in communication with the compressor and
each of the heat exchangers and adapted for carrying refrigerant
through the system to each of the heat exchangers, the at least one
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conduit including a return conduit for carrying refrigerant gas back
to the compressor,
iv. a reversing valve in communication with the at least one conduit
and configured to reverse the flow of refrigerant from the
compressor to the heat exchangers depending upon whether the
system is operating in the cooling mode or the heating mode;
such that when the intensifier heat exchanger is operating in heating mode,
the valve is
activated to direct refrigerant pumped from the compressor through the at
least one
conduit to the first heat exchanger where the refrigerant gas is condensed
into liquid,
through the return conduit to the second heat exchanger where the liquid is
vaporized
into gas and heat is efficiently transferred from earth source through the
thermal
superconductor, and back to the compressor via the return conduit;
and such that when the intensifier heat exchanger is operating in cooling
mode, the
valve is activated to direct refrigerant pumped from the compressor through
the at least
one conduit to the second heat exchanger where the refrigerant gas is
condensed into
liquid and heat is efficiently transferred to earth source through the thermal
superconductor, through the return conduit to the first heat exchanger such
that the
liquid is vaporized into gas, and back to the compressor via the return
conduit;
b) a_refrigerating heat exchange coil formed from thermal superconductor
material, having a transfer segment terminating at opposing ends at;
i. a refrigerating heat exchange segment,
ii. a refrigerating heat exchange segment coupled to one of the first or
second heat exchangers, and
c) a dissipating heat exchange coil formed from thermal superconductor
material,
having a transfer segment terminating at opposing ends at,
i. a dissipating heat exchange segment,
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ii. a dissipating heat exchange segment coupled to the other one of the
first or second heat exchangers,
such that the reversing valve can be configured to provide corresponding
refrigerating
or defrosting modes of the superconductor refrigeration system, and the
configurations
being selected by the control means for the purpose of operating in a
refrigerating or
defrosting mode to refrigerate a space.
According to another aspect of the present invention, a superconductor
defrosting
system having thermal superconducting heat transfer. The system including;
a) an intensifying heat exchanger, having
vi. a refrigerant coil which receives refrigerant in the heating and cooling
cycle
vii. a condenser heat exchange segment of the coil
viii. a evaporator heat exchange segment of the coil
ix. evaporating means to expand liquid refrigerant to partial liquid and
located between the exchange segments,
X. compressor means for compressing and circulating a refrigerant in the
refrigerant coil;
b) a defrosting heat exchange coil formed from thermal superconductor
material,
having a transfer segment terminating at opposing ends at,
a defrosting heat exchange segment,
a condenser heat exchange segment
c) an absorbing heat exchange coil formed from thermal superconductor
material, having a transfer segment terminating at opposing ends at,
an absorbing heat exchange segment,
a evaporator heat exchange segment
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d) a controller programmable to a desired set point and further having control
means connected to the thermal switch and compressor means;
According to another aspect of the present invention, a superconductor
defrosting
system having thermal superconducting heat transfer and a heat transfer fluid,
including;
a) a defrost heat exchange coil formed from thermal superconductor material,
having a transfer segment terminating at opposing ends at,
a defrosting heat exchange segment,
a thermal switch segment
b) an absorbing heat exchange coil formed from thermal superconductor
material, having a transfer segment terminating at opposing ends at,
an absorbing heat exchange segment
a thermal switch segment
c) a thermal switch connected to the defrosting heat exchange coil and the
absorbing heat exchange coil, such that in a first switch position the
defrosting
heat exchange coil is thermally coupled to the absorbing heat exchange coil
and
in a second switch position the defrosting heat exchange coil is thermally
isolated
from the absorbing heat exchange coil
d) an absorbing heat exchanger providing transfer means for heat to be
exchanged between the absorbing heat exchange segment and the circulating
fluid of a separate heat-providing system
e) a controller programmable to a desired set point and connected to the
thermal
switch
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such that the control means operate the compressor in response to a control
signal for
the purpose of transferring heat from the absorbing heat exchange coil to the
defrosting
heat exchange coil to melt ice build-up on an evaporator component of a
refrigeration
system.
According to another aspect of the present invention, a superconductor
refrigeration
exchange element for use in an air flow path is provided, including;
a) a plurality of evaporator refrigerant conduits suitable for receiving
refrigerant,
b) An evaporator coupled to ends of each of the plurality of refrigerant
coils,
c) A condenser conduit coupled to opposing ends of each of the plurality of
refrigerant coils,
d) a plurality of cooling plates formed of a thermally conductive material
arranged in
a substantially co-planar stack, and having
i. at least one conduit opening through each of the plates corresponding
to each refrigerant conduits such that the conduits are seated in
thermal contact within the cooling plate stack for the purpose of
exchanging heat with air,
ii. at least one secondary opening through each of the plates spaced
apart from the conduit opening
e) a thermal superconductor heat transfer pipe arranged such that a coupling
portion is seated within the at least one secondary opening such that thermal
contact is created between the cooling plates and the heat transfer pipe, and
a
transfer portion extends away from the stack of plates,
f) insulation surrounding at least part of the extended portion to reduce heat
transfer loss;
such that heat is efficiently transferred from the cooling plates by the
refrigerant
conduits for the purposes of cooling the air flow and heat is transferred to
cooling plates
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by the thermal superconductor heat transfer pipe for defrosting ice build up
on the
cooling plates such that the air flow is substantially maintained.
According to another aspect of the present invention, a superconductor
refrigeration
exchange element for use in an air flow path is provided, including;
a) a plurality of evaporator refrigerant conduits suitable for receiving
refrigerant,
b) an evaporator coupled to ends of each of the plurality of refrigerant
coils,
c) a condenser conduit coupled to opposing ends of each of the plurality of
refrigerant coils,
d) a plurality of cooling plates formed of a thermally conductive material
arranged in
a substantially co-planar stack, and having at least one conduit opening
through
each of the plates corresponding to each refrigerant conduits such that the
conduits are seated in thermal contact within the cooling plate stack for the
purpose of exchanging heat with air,
e) a thermal superconductor heat transfer pipe arranged such that a coupling
portion is coupled on at least one side of the cooling plates stacks such that
thermal contact is created between the cooling plates and the heat transfer
pipe,
the location of the coupling portion relative to the seated conduits is
arranged to
substantially maximize available air flow through the plates, and a transfer
portion extends away from the stack of plates,
f) insulation surrounding at least part of the extended portion to reduce heat
transfer loss;
such that heat is efficiently transferred from the cooling plates by the
refrigerant
conduits for the purposes of cooling the air flow and heat is transferred to
cooling plates
by the thermal superconductor heat transfer pipe for defrosting ice build up
on the
cooling plates such that the air flow is substantially maintained.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1: A THERMALLY SUPERCONDUCTING REFRIGERATION
SYSTEM. This figure shows a) a schematic of an efficient refrigeration system
with
thermal superconductor heat exchangers and a reversible superconductor
transfer
switch enabling the system to switch from refrigeration to defrost and b) an
enlarged
view of the intensifier heat circuit.
FIGURE 2: A SWITCHABLE THERMALLY SUPERCONDUCTING
REFRIGERATION SYSTEM. This figure shows a schematic of an efficient
refrigeration
and defrost system with thermal superconductor transfer segments coupled to a
heat
intensification circuit by independent thermal transfer switches.
FIGURE 3: A THERMALLY SUPERCONDUCTING REFRIGERATION
SYSTEM WITH MULTIPLE EXCHANGERS. This figure shows a schematic of an
efficient refrigeration / defrost system with multiple thermal superconductor
heat
exchangers coupled with independent thermal transfer switches to a single heat
intensification circuit.
FIGURE 4: A THERMALLY SUPERCONDUCTING REFRIGERATION
SYSTEM WITH ADDITIIONAL LIQUID HEAT EXCHANGER. This figure shows a
schematic of an efficient refrigeration and defrost system using a liquid heat
exchanger
as a heat source or heat sink.
FIGURE 5: A THERMALLY SUPERCONDUCTING REFRIGERATION
SYSTEM WITH REVERSING VALVE. This figure shows a schematic of refrigeration /
defrost system using superconductor heat exchangers with blowers and a
reversing
valve to switch the system from refrigeration to defrost.
FIGURE 6: A THERMALLY SUPERCONDUCTING REFRIGERATION
SYSTEM WITH MULTIPLE EXCHANGERS AND A REVERSING VALVE. This figure
shows a schematic of refrigeration / defrost system using multiple
superconductor heat
exchangers with blowers and a reversing valve to switch the system from
refrigeration
to defrost.
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FIGURE 7: A THERMALLY SUPERCONDUCTING DEFROST SYSTEM.
This figure shows a schematic of a defrost system using superconductor heat
exchangers
FIGURE 8: A THERMALLY SUPERCONDUCTING DEFROST SYSTEM
USING WASTE HEAT. This figure shows a schematic of a defrost system using a
heat
intensification circuit and a superconductor heat exchanger to draw waste heat
from the
hot vapor line of a conventional refrigeration system.
FIGURE 9: A THERMALLY SUPERCONDUCTING DEFROST SYSTEM
USING WASTE HEAT. This figure shows an alternate defrost system using waste
heat
indirectly from the hot vapor line of a conventional refrigeration system
through a liquid
heat exchange fluid.
FIGURE 10: A THERMALLY SUPERCONDUCTING DEFROST SYSTEM
USING WASTE HEAT. This figure shows an alternate defrost system using waste
heat
from a circulating fluid from another heat generating system.
FIGURE 11: A THERMALLY SUPERCONDUCTING DEFROST SYSTEM
USING WASTE HEAT DIRECTLY. This figure shows a schematic of a defrost system
using a superconductor heat exchanger to draw waste heat directly from the hot
refrigerant line of a conventional refrigeration system without the assistance
of a heat
intensification circuit.
FIGURE 12: A THERMALLY SUPERCONDUCTING DEFROST SYSTEM
WITH MULTIPLE HEAT EXCHANGERS USING WASTE HEAT DIRECTLY. This figure
shows a schematic of a defrost system using a superconductor heat exchanger to
draw
waste heat directly from the hot refrigerant line of a conventional
refrigeration system
without the assistance of a heat intensification circuit.
FIGURE 13: A SUPERCONDUCTOR HEAT EXCHANGER. This figures
shows a heat exchanger with superconductor heat exchange segments.
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FIGURE 14: A SUPERCONDUCTOR DEFROST ELEMENT
INTEGRATED INTO A CONVENTIONAL PHASE-CHANGE FLUID HEAT
EXCHANGER. This figures shows a) a cut-away view of a conventional
refrigerating
heat exchanger showing the fluid flow path, b) a modifiedrefrigerating heat
exchanger
with couplable superconductor defrost heat exchange elements, and c) a
modified
refrigerating heat exchanger with integrated superconductor defrost heat
exchange
elements.
FIGURE 15: A SUPERCONDUCTOR DEFROST ELEMENT APPLIED
TO THE FACE OF A CONVENTIONAL PHASE-CHANGE FLUID HEAT EXCHANGER.
This figure shows superconductor defrost heat exchange elements applied to the
face
of a conventional heat exchanger.
FIGURE 16: A SUPERCONDUCTOR REFRIGERATION SYSTEM IN A
TYPICAL REFRIGERATING BUILDING APPLICATION. This figure shows an elevation
of a preferred embodiment of a refrigeration and defrost system installed in a
building
where the refrigerated space, the refrigeration plant and the dissipating heat
exchangers are separated from each other.
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DETAILED DESCRIPTION OF THE INVENTION
Description of the invention
With reference to the drawings, new devices and systems for improved
refrigeration and defrosting will be described, embodying the principles and
concepts of
the present invention.
Recent advances in thermal superconducting materials can now be
considered for use in novel energy transfer applications. For example, US
patents
6132823, 6916430 and 6911231 and continuations thereof, disclose a examples of
a
heat transfer medium with extremely high thermal conductivity and methods of
manufacture, and are included herein by reference. Specifically the following
disclosure
indicates the orders of magnitude improvement in thermal conduction;
"Experimentation
has shown that a steel conduit 4 with medium 6 properly disposed therein has a
thermal
conductivity that is generally 20,000 times higher than the thermal
conductivity of silver,
and can reach under laboratory conditions a thermal conductivity that is
30,000 times
higher that the thermal conductivity of silver." Such a medium is thermally
superconducting, and when suitably configured for refrigeration, its
application results in
many significant advantages. The available product sold by Qu Energy
International
Corporation is an inorganic heat transfer medium provided in a vacuum sealed
heat
conducting tube. Throughout the disclosure, the term superconductor shall
interchangeably mean thermal superconductor. For illustrative purposes, this
superconductor may be in the form of a sealed metal tube as currently
available from
Qu Corporation and will be considered to be in tube form. Alternatively, other
available
thermal superconductors could be similarly substituted that may have various
forms and
cross sections such as flexible conduits, thin laminate, thinfilm coated metal
etc.
Optionally, the superconducting transfer segments maybe formed from
discontinuous
discrete sections of superconducting material separated by small gaps of a non-
superconducting material.
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An embodiment of the invention is a refrigeration system comprised of two
subsystems. The first subsystem is a refrigeration loop which serves to
intensify heat
energy so it can be moved efficiently. The second subsystem is a heat
distribution
system that uses thermal superconductor elements to absorb and dissipate heat
and to
move heat through the system without moving parts. These subsystems may
include:
a) two heat exchangers, one hot and one cold, which can be for
example, located in the refrigeration plant area, to transfer heat
energy between the phase change refrigeration subsystem and the
superconductor distribution subsystem;
b) two or more blowers to draw air across the heat exchangers to
achieve the transfer of heat energy to or from the heat exchangers;
c) one or more thermal superconductor switches to allow heat to be
directed to or from any individual heat exchange component or to
allow individual heat exchange components to be isolated from the
system;
d) superconductor distribution components to transfer heating and
cooling energy between the switches and the individual heat
exchange components;
e) superconductor heat exchangers to absorb heat from spaces to be
cooled
f) superconductor heat exchangers to dissipate excess heat into the
atmosphere or transfer excess heat to other building systems which
can use this heat; and
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g) thermostats and programmable controllers to enable the system to
sense and respond to conditions throughout the refrigeration
system.
The embodiment of the refrigeration system operates in the following
general manner. The phase-change refrigerant subsystem operates as a local
heat
intensification circuit, with a "cold" heat exchanger or "evaporator" which
absorbs heat
from the heat distribution subsystem, a compressor which intensifies this
heat, and a
"hot" heat exchanger or "condenser" which transfers this heat back into the
distribution
subsystem. In a refrigeration mode, the "cold" heat exchanger is connected by
a
superconducting heat transfer element to a superconducting heat exchanger in a
space
selected to be cooled (the "refrigeration space"), while the "hot" heat
exchanger is
connected by superconducting heat transfer elements to a superconducting heat
exchanger located or coupled for external heat transfer such as outside a
building, by
thermal routing using a superconducting thermal switch in a refrigeration mode
setting.
Air from the refrigeration space is drawn by a blower across the
superconducting heat
exchanger where heat from the air is absorbed by the heat exchanger's cold
surfaces.
The air returns to the space colder, cooling the space. The heat absorbed from
the air
is transferred by the superconducting transfer elements to the "cold" heat
exchanger,
then transferred to the refrigerant loop, intensified and transferred to the
"hot" heat
exchanger and back to the thermal switch. The heat is then transferred by
superconducting thermal transfer elements to the dissipating superconducting
heat
exchanger. A fan blows air across the heated surfaces of the superconducting
heat
exchanger, causing the heat to be absorbed by the air and dissipated into the
atmosphere.
In a defrost mode, the thermal switch is reversed, connecting the "hot"
heat exchanger to the superconducting heat exchanger in the refrigeration
space, and
the "cold" heat exchanger to the external superconducting heat exchanger
outside the
refrigeration space. Heat is absorbed from the external or outside air by the
outside
heat exchanger, transferred to the "cold" heat exchanger, absorbed by the
refrigerant
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loop, intensified, transferred to the "hot" heat exchanger and then
transferred to the
superconducting heat exchanger in the cooled space, heating it up and melting
the ice
that has built up on its surfaces.
Replacing the circulating fluid components of conventional heat
distribution systems with thermal superconductor components has a number of
advantages that overcome the limitations described in the background. First,
thermal
superconductors as described herein have no moving parts, except as configured
as
thermal switches for routing heat efficiently. Second, thermal superconductors
have the
capacity to transfer heat over relatively long distances with minimal energy
loss and
without the assistance of mechanical pumping. Third, the superconductors
transfer heat
bi-directionally so the system can be changed quickly from refrigeration to
defrost with
minimal stress on system components and without changing the direction of the
circulation of the conventional refrigeration loop. Fourth, they can be
arranged to allow
heat to be transferred more uniformly across heat exchangers, making these
heat
exchangers more efficient and therefore potentially smaller than conventional
circulating
phase change heat exchangers.
Limiting the function of the conventional phase change refrigeration loop
to the intensification of heat has several advantages. First, it allows the
phase change
refrigeration subsystem to be contained within the refrigeration plant area of
a building,
making it smaller and less complicated than in a conventional refrigeration
system
because large volumes of refrigerant are not required to be circulated over
long
distances. Second, in the preferred embodiment, it allows the phase change
refrigeration subsystem to operate in the same direction in both refrigeration
and defrost
cycles, eliminating all reversing valves, all but one of the thermostatic
expansion
metering valves, most of the circulating refrigerant in the system and most of
the
reservoirs required in a reversing system to handle excess liquid refrigerant.
Third, it
eliminates refrigerant leaks outside the central refrigeration plant area and
makes the
system easier to service. Fourth, the elimination of unreliable components,
extends
system lifetime and reduces system maintenance.
CA 02530621 2006-01-03
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In addition to the foregoing technical advantages, this refrigeration system
(in its various embodiments) shows significant operational advantages over
conventional refrigeration systems. First, it allows heat energy to be moved
efficiently
from one heat exchanger to any other in the system so that waste heat produced
by any
refrigeration unit can be used to defrost the heat exchanger in any other
refrigeration
unit. Second, it allows waste heat to be moved efficiently to and from other
building
mechanical systems such as air heat, floor heat, snow melt, domestic hot water
and
grey water. And third, with correct switching, this system allows
refrigeration units to
provide space cooling without the use of mechanical compression whenever
outdoor
temperatures are low enough to be practicable.
Figure 1 a illustrates an embodiment of refrigeration system 110 in which
heat is transferred bi-directionally using a thermal superconducting medium in
the
manner described generally above.
Specifically, an intensifier heat circuit forms a refrigerant transfer path
which includes a compressor 24 having outlet connected by refrigerant conduit
19 to a
condenser heat exchanger 21 connected to an evaporator conduit 23 connected to
a
expander 26 connected to an evaporator heat exchanger 28 connected to a return
conduit 29 and an optional accumulator 30 connected by a return conduit 31 to
the inlet
of the compressor 24. As is well known in the art, the condenser heat
exchanger gives
up heat and the evaporator heat exchanger absorbs heat, referred to,
respectively, as
hot and cold intensifier exchangers, for the purpose of delivering higher
grade heat. The
compressor 24 compresses a gaseous refrigerant to intensify its heat content,
circulates
it through conduit 19 to the condenser heat exchanger 21 where it gives up
heat and
condenses to a liquid or partial liquid, and then passes through conduit 23 to
expander
26 which rapidly expands the liquid in a pressure drop causing the refrigerant
to
become a supercooled partial liquid which absorbs heat and evaporates in the
evaporator heat exchanger 28 before passing through return conduit 29 to
optional
CA 02530621 2006-01-03
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accumulator 30 (where excess remaining liquid is trapped and evaporated) and
remaining refrigerant passes through conduit 31 to complete the loop at the
compressor
inlet. This heat intensifier circuit is for the purpose of converting low
grade heat to high
quality heat such that heat is transferred at a faster rate. Any apparatus for
intensifying
heat can equivalently substitute for the refrigerant based heat intensifier
circuit
illustrated. When the refrigerant loop as described is filled with a suitable
amount of
refrigerant, the intensifier circuit is operated by turning the compressor on.
This creates
a temperature differential between condenser heat exchanger 21 and evaporator
heat
exchanger 28. In the preferred case, the intensifier heat exchangers are
isolated by
insulation 25. Superconductor segment 32 is coupled to condenser heat
exchanger 21
and superconductor segment 34 is coupled to evaporator heat exchanger 28, and
both
superconductor segments terminate on an input side of 2 x 2 thermal switch 36.
The thermal switch functions to selectively couple the intensifier heat
exchangers to refrigeration space heat exchanger 42 (associated with a
partially or fully
closed space to be refrigerated) and external heat exchanger 42a (in an
environment
external to the refrigerated space.) A high efficiency thermal switch design
is described
in a related application "Thermally superconducting heat transfer switches",
incorporated herein for reference. Alternately, the thermal switch may be made
of other
thermally conductive material such as copper or silver alloys with resulting
higher
losses. For short transfer distances, segments 32 and 34 can equivalently be a
non-
superconducting heat transfer medium with a resulting small loss in overall
efficiency .
In the preferred embodiment the thermal superconductor pipes 32 and 34 are
efficiently
coupled to heat exchangers 21 and 28 respectively by direct contact including
spot
welding the two components side by side along a suitable "transfer length" or
forming
both such that a substantial contact areas of the two components can be
clamped or
joined. The heat intensifier circuit is for the purpose of converting low
grade heat to high
quality heat such that heat is transferred at a faster rate. Any apparatus for
intensifying
heat can equivalently substitute for the refrigerant based heat intensifier
circuit
illustrated.
CA 02530621 2006-01-03
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The first of two remaining inputs of the thermal switch 36 is connected to
thermal superconductor transfer segment 38, which is connected to
refrigeration space
heat exchange coil 42 within a space to be cooled. A thermal sensor 18 is
associated
with the air to be conditioned by refrigeration space heat exchange coil 42. A
controller
16 is powered by power line 14 and provides power to compressor 24 and thermal
switch 36, as well as control data to and from thermal switch 36, blowers 55
and 55a
and thermal sensors 18 and 18a. As will be appreciated, variations of this
example may
include independently connected compressor or blower power or multiple control
systems without changing functionality. Refrigerating heat exchange coil 42
can be
configured in any geometric arrangement to optimize heat transfer to a
specific medium.
Insulation 25 preferably covers superconductor transfer segments outside of
coupling
connections and heat exchange sections, to reduce thermal transfer losses. The
last
remaining input of the thermal switch 36 is connected to thermal
superconductor
transfer segment 40 which is connected to external heat exchanger 42a. A
thermal
sensor 18a is associated with the air to which external heat exchanger 42a
transfers
heat. Controller 16 provides control data to and from thermal sensor 18.
External heat
exchange coil 42a can be configured in any geometric arrangement to optimize
heat
transfer to the air.
The refrigeration heat exchange system 110 is operated in either a
refrigeration or a defrost mode. The refrigeration mode operation can be
determined in
proportion to the difference between a refrigeration setpoint and the measured
temperature from sensor 18. Defrost mode may be programmed for periodic
maintenance based on empirical understanding of ice buildup, or an additional
ice
buildup sensor (not shown) may be added with a setpoint that triggers defrost
mode, for
example an optical displacement sensor or air pressure sensor common in the
industry.
In refrigeration mode, thermal switch 36 is controlled to couple
superconductor 38 to
cool segment 34 and to couple superconductor 40 to hot segment 32. Controller
16
operates compressor 24 which comprises part of a heat intensification circuit.
Blower 55
draws air across the cold surfaces of refrigeration space exchanger 42 causing
heat to
be absorbed from the air. Thermal superconductor transfer segment 38 then
transfers
CA 02530621 2006-01-03
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this heat efficiently to the intensifier circuit where it is intensified and
then transferred by
superconductor transfer segment 40 to external superconductor heat exchange
coil
42a. Blower 55a then draws air across the heated surfaces of heat exchange
coil 42a
causing heat to be absorbed into the air and dissipated into the atmosphere
outside the
space to be cooled. The blower may be local and dedicated to the refrigeration
system
shown, or may alternatively be shared or provided as a separate room
circulating
system having the refrigeration space heat exchanger positioned suitably in
the flow
path, for example fans embedded in a wall pushing air past suspended heat
exchangers.
In defrost mode, thermal switch 36 is controlled to reverse the thermal
couplings and heat transfer such that refrigeration space heat exchanger
becomes
heated and external heat exchanger absorbs heat, i.e. they reverse functions
compared
to refrigeration mode. Superconductor 38 is coupled to hot segment 32 and
superconductor 40 is coupled to cold segment 34, and controller 16 operates
compressor 24,which comprises part of a heat intensification circuit. Heat is
then
efficiently absorbed from air drawn by blower 55a across the cooled surfaces
of external
heat exchange coil 42a and then transferred through superconductor transfer
segment
40 to the intensifier circuit and intensified, then efficiently transferred
through
superconductor transfer segment 38 to refrigeration space exchange coil 42,
causing it
to heat up and melt any ice that has built up on its surfaces. Melted water is
then
collected in drip tray 56 and drained away through condensate drain line 58 to
a suitable
location. Sensor 18 may be located for effective monitoring of degree of
melted ice on
the heat exchanger, or an additional defrost sensor (not shown) may be
included and
connected to controller 16. The modes may simply switch on/off or
alternatively oscillate
between refrigerating and defrosting based on programming of controller 16,
however
as is evident from Figure 1, the modes are mutually exclusive as relates to a
system
with a single refrigeration space heat exchanger and a single external heat
exchanger.
The intensifier circuit may have additional components as required to
scale for larger energy applications, for example where the refrigeration
space is very
CA 02530621 2006-01-03
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large and partially open for storage access. As shown in figure lb for an
expanded
alternate arrangement of a large scale intensifier circuit , such larger
systems may have
receivers 33, suction accumulators 30, bulb sensors 17, thermostatic expansion
metering valves 15 and the like to manage refrigerant flow through the heat
intensification circuit, as known in the art of conventional heat pump
systems.
Using the preferred thermal superconducting tubes, it is preferred to have
insulation 25 along the length of all superconductor segments except heat
exchanger
coil segments or thermal transfer couplings to other components, to limit heat
loss and
condensation buildup. However alternate thermal superconductor embodiments may
have integrated insulating layers or have acceptable transfer loss such that
the
refrigerating heat exchange system 110 is operable with less or no external
insulation.
The refrigerating heat exchange system 110 can be enclosed a number of
ways, depending on application. All components can be housed inside one
enclosure to
comprise a unit refrigerator. Alternatively, as shown in Figure 1, the heat
intensifier
circuit, switch and controller can be housed in a housing 12 (such as a room
in a
building), and superconductor heat exchange coils 42 and 42a can be housed in
separate enclosures 60 and 60a respectively, as would typically be found in a
large
industrial refrigeration application where the refrigeration plant, the space
to be cooled
and the outdoor location for the dissipation of heat are at a significant
distance from
each other. In another alternative embodiment, the heat intensifier circuit
can be
enclosed in either enclosure 60 or 60a with superconductor heat exchange coils
42 or
42a respectively, such as is found in conventional "split" systems. As is well
known in
the art of controlling mechanical systems, controller 16 and sensors 18 and
18a can be
equally enclosed within enclosures 12, 60 or 60a, or located outside these
enclosures
and connected either wirelessly or by wires to other associated components in
refrigerating heat exchange system 110. Similarly controller 16 can be
remotely
programmed through wired or wireless communications.
CA 02530621 2006-01-03
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Figure 2 illustrates an embodiment of the invention in which discrete two
state superconducting thermal switches 64 and 64a replace the function of
reversing
switch 36 of Figure 1, to operate as refrigeration system 120. Each thermal
switch 64
and 64a can couple to both of the hot or cold intensifier heat exchangers 21
and 28. In
refrigerating mode, thermal switch 64 is set so that cold superconductor
transfer
segment 34 is coupled with superconductor transfer segment 38 such that heat
absorbed from a space by refrigeration space exchanger 42 is efficiently
transferred to
cold heat exchanger 28, and thermal switch 64a is set so that hot
superconductor
transfer segment 32 is coupled with superconductor transfer segment 40 such
that heat
absorbed from hot heat exchanger 21 by superconductor transfer segment can be
efficiently transferred to external heat exchanger 42a and dissipated into the
atmosphere. In defrost mode, thermal switches 64 and 64a are set in reverse
position
such that heat absorbed by dissipating heat exchanger 42a can efficiently be
transferred through the system to refrigeration space exchanger 42 for the
purpose of
melting built-up ice. For system 120 to operate, switches 64 and 64a must be
set
oppositely, so that one couples to hot heat exchanger 21 and one couples to
cold heat
exchanger 28, as controlled by controller 16. Refrigeration system 120 can be
similarly
housed and programmed for response to the associated thermal sensors, as
system
110, with the minor exception of the switching arrangement.
Typical industrial refrigeration applications require distributed cooling and
shared dissipation configurations, which are easily enabled by the teachings
of the
superconductor refrigeration system 130 shown in Figure 3. Figure 3
illustrates an
embodiment of the invention in which a plurality of refrigeration space
exchangers 42,
42a, are coupled to a plurality of thermal switches 64, 64a respectively, and
external
heat exchanger 90 is coupled to thermal switch 64b. In this embodiment,
switches 64,
64a and 64b can be independently set so that each of heat exchangers 42, 42a
and 90
operate as either heat absorbing or heat dissipating, subject to at least one
of the heat
exchangers being coupled to hot heat exchanger 21 and at least one being
coupled to
cold heat exchanger 28 to provide a minimum thermal balance. In this
embodiment for
CA 02530621 2006-01-03
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a refrigerating mode, refrigeration system 130 can be set so that heat
exchangers 42
and 42a operate as refrigeration space exchangers and heat exchanger 90
operates as
a external heat exchanger. Alternatively, heat exchanger 42 can be set to
operate as a
refrigeration space exchanger with heat exchangers 42a and 90 set to operate
as
dissipating heat exchangers such that heat exchanger 42 refrigerates while
heat
exchanger 42a defrosts. Note that in this previous case the terminology
external has
dropped and the term dissipating heat exchanger used, since within this
context heat
may be exchanged with another refrigeration space heat exchanger operating in
defrost
mode rather than an external heat dissipation, In this mode of operation, heat
absorbed
by heat exchanger 42 is transferred to the heat intensification circuit and
then to heat
exchanger 42a for the purpose of defrosting any build up of ice. This enables
refrigeration system 130 to efficiently reuse waste heat produced by at least
one
refrigeration space exchanger. In another mode of operation, one of heat
exchangers
42, 42a can be disconnected from the heat intensification circuit by
positioning
corresponding switch 64 or 64a in an off position, allowing the disconnected
heat
exchanger to be serviced or inoperable while the connected heat exchanger
continues
to refrigerate or defrost. The modes of operation can as before be programmed
to
respond to periodic timing, or in response to environmental temperature
changes in the
associated thermal sensors, or by external controls or stimulus as required to
optimize
the refrigeration and defrost cycles, and overall system efficiency. The
flexibility of this
system configuration represents a significant advance over conventional
systems, by
reducing mode switching response times through elimination of refrigerant
reversal and
efficiently reusing transferred energy not recovered otherwise, and permitting
simultaneous concurrent defrost and refrigeration using the same intensifier
circuit.
As shown in refrigeration system 140 in Figure 4, the integrated multiple
heat exchangers illustrated in system 130 can have extended functionality by
adding a
thermal storage or ballast with heat exchange functionality. A plurality of
air-to-
superconductor heat exchangers are independently coupled through thermal
switches
64, 64a and 64b to a heat intensification circuit, and fluid-to-superconductor
heat
exchanger 104 is also coupled to the circuit by thermal switch 64c such that
any of the
CA 02530621 2006-01-03
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heat exchangers can independently operate to absorb or dissipate heat, subject
to at
least two of the heat exchangers being coupled to the heat intensification
circuit at any
time, and at least one of the coupled heat exchangers being set in heat
absorption
mode and at least one of the coupled heat exchangers being set in heat
dissipation
mode. Fluid to superconductor heat exchanger 104 is configured within a liquid
storage
tank 98 filled with liquid 94 such as water or a solution with high heat
capacity, and
having associated temperature sensor 96 connected to controller 16 for
feedback on the
temperature of the stored liquid. In the preferred embodiment, one of the heat
exchangers, for example heat exchanger 90, is external to the refrigeration
space. In a
heat storage mode selected by controller 16 in response to programming and/or
temperature measurements, excess heat absorbed by any one or combination of
air-to-
superconductor heat exchangers 42, 42a and 90 can be efficiently transferred
to fluid-
to-superconductor heat exchanger 104 for transfer to fluid 94, either for
storage in tank
98 or for use by a separate mechanical system (not shown) which circulates
fluid 94 into
tank 98 through fluid inlet 100 and out of tank 98 through fluid outlet 102.
In a heat
recovery mode, thermal switches of refrigeration system 140 can be set so that
heat in
fluid 94 can be absorbed by fluid-to-superconductor heat exchanger 104 and
transferred
efficiently to the heat intensification circuit and then transferred to any
one or
combination of the air-to-superconductor heat exchangers for the purpose of
defrosting
or alternatively for space heating. The refrigeration system with heat storage
functionality is well-suited for time varying non-uniform utilization of one
or more
refrigeration spaces, and is enabled by bi-directional efficient heat transfer
using
thermal superconductors.
The embodiments shown in Figures 1 to 4 are preferred implementations
for systems that both refrigerate and defrost. However, there is a key
substitution that
could be made that would still be improved over existing refrigeration systems
but have
fewer operating modes with the tradeoff of using a less reliable component - a
reversing
valve. The refrigeration systems in Figures 1 to 4 may be modified by adding
reversing
valve 77 in the intensifier circuit and eliminating all thermal switches as
shown in the
CA 02530621 2006-01-03
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refrigerating heat exchange system 150 of Figure 5, to create a reversible
heat
intensifying loop as is well known in the art. In this embodiment, refrigerant
vapor is
compressed by compressor 24 and then flows through conduit 19 to reversing
valve 77.
The reversing valve, controlled by controller 16 through control line 20, then
directs this
vapor to either of heat exchanger 70 or 74, according to whether heating or
cooling is
required.
If refrigeration is required for refrigerating heat exchanger 42, controller
16
sends an instruction to reversing valve 77 to actuate to a position such that
heated
refrigerant vapor is transferred from conduit 19 to conduit 75. The
refrigerant then flows
to heat exchanger 74, which functions as a condensing heat exchanger. Heat
exchanger 74 gives up heat to superconducting heat transfer segment 40 which
transfers it to external heat exchanger 42a in heat dissipating mode, located
outside the
space to be cooled. The refrigerant gas flowing through heat exchanger 74
condenses
in the process of giving up heat, forming a liquid or partial liquid which is
transferred
through conduit 73 to bi-directional expansion element 72 which causes liquid
refrigerant to become a supercooled partial liquid before flowing through
conduit 71 to
heat exchanger 70, where it absorbs heat from superconducting transfer segment
38
which transfers heat from refrigeration space heat exchanger 42. The design of
expansion element 72 for use in both circulation directions is well-known. The
warmed
refrigerant gas then passes through conduit 76 and then through reversing
valve 77
which, in the selected position for this mode, transfers it through conduit 29
to optional
accumulator 30 which traps and then allows to evaporate excess remaining
liquid
refrigerant before the refrigerant vapor returns through conduit 31 to
compressor 24 to
begin the heat intensification cycle again. As described previously controller
16,
controls operation of refrigeration mode through feedback from temperature
sensor 18
and/or 18a, or associated external stimulus, by operating the compressor and
reversing
valve.
If defrost is required, controller 16 sends an instruction to reversing valve
77 to actuate to a position such that heated refrigerant vapor is transferred
from conduit
CA 02530621 2006-01-03
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19 to conduit 76. The refrigerant is then transferred to heat exchanger 70
which then
functions as the condensing heat exchanger. Heat exchanger 70 gives up heat to
superconductor heat transfer segment 38 which transfers heat to refrigeration
space
heat exchanger 42 where this heat melts ice built up on the surfaces of the
heat
exchanger. The refrigerant gas flowing through heat exchanger 70 condenses in
the
process of giving up heat, forming a liquid or partial liquid which is
transferred through
conduit 71 to bi-directional expansion element 72 which causes liquid
refrigerant to
become a supercooled partial liquid before flowing through conduit 73 to heat
exchanger 74, where it absorbs heat from superconducting transfer segment 40
connected to external heat exchanger 42a which absorbs heat from the air drawn
across it by blower 55a. The heated refrigerant vapor then passes through
conduit 75
and then through reversing valve 77 which, in the selected position for this
mode,
transfers it through conduit 29 to optional accumulator 30 which traps and
then allows to
vaporize excess remaining liquid refrigerant before the refrigerant vapor
returns through
conduit 31 to compressor 24 to begin the heat intensification cycle again.
This system
has the advantages of using well known components for switching modes in the
intensification circuit; however it is noted that for larger intensification
circuits designed
for large scale heat capactity, the volume of refrigerant inhibits reversal
and creates a
delay time during which the system is inoperable or inefficient. While this
effect is
reduced relative to a full conventional circulation, it is not as preferred as
the thermally
switched embodiments.
Refrigeration system 160 in Figure 6 expands system 150 to include a
plurality of refrigeration space heat exchangers 42 and 42a. In this
embodiment,
superconductor transfer segment 38 becomes a thermal bus which, in the
refrigerating
mode, transfers heat from refrigerating heat exchangers 42 and 42a to heat
exchanger
70, and in the defrost mode transfers heat from heat exchanger 70 to
refrigeration
space heat exchangers 42 and 42a for the purpose of melting any build up of
ice.
Superconductor external heat exchanger 90 is directly connected to intensifier
heat
CA 02530621 2006-01-03
30
exchanger 74 by superconductor thermal transfer pipe 40 and operates in
dissipating or
absorbing modes depending on direction of the intensifier circuit.
This embodiment provides the basic operational modes of refrigeration
and defrost such that the bussed refrigeration space heat exchangers 42 and
42a are
fixed in identical modes. Therefore, because refrigerating heat exchanger 42
and heat
dissipating heat exchanger 42a are not separately switched as shown in Figures
1 to 4,
no other operating modes described for Figures 1 to 4 are enabled.
All refrigerating systems shown in Figures 1 to 6 operate in both
refrigeration and defrost modes, and in some cases mixed modes. In some
applications
it will not be necessary for a system to have both refrigerating and defrost
modes. One
such application is in the retrofitting of existing conventional phase-change
refrigerant
systems, where complete replacement would be economically inefficient. In such
an
application, some of the most difficult problems of reversing phase change
systems
could be eliminated by the addition of a separate system to handle defrost
only. Figure
7 illustrates such a defrost only system 170. Defrost heat exchanger 42a is
permanently
coupled by superconducting heat transfer segment 32 to hot heat exchanger 21,
and
heat absorbing heat exchanger 42 is permanently coupled by superconducting
heat
transfer segment 34 to cold heat exchanger 28. The coupling of the defrost
heat
exchanger to the evaporator is further described in Figures 11-13.
When controller 16 receives a signal from defrost sensor 18a that ice has
built up on an associated evaporator coil (not shown) of a separate
refrigerating system
(not shown) or determines that a programmed periodic defrost cycle is due ,
controller
16 operates compressor 24 to activate a heat intensification circuit. Heat is
absorbed
from the atmosphere by external heat exchanger 42 and transfers it by
superconductor
heat transfer segment 34 to the heat intensification circuit, which
intensifies it and
transfers heat by superconducting heat transfer element 32 to defrost heat
exchanger
42a for the purpose of melting ice that has built up on the associated
evaporator coil. As
CA 02530621 2006-01-03
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will be obvious to one skilled in the art of conventional refrigeration
systems, sensor 18a
can be alternatively an infrared sensor, a sensor that detects changes in
static pressure
of the air being drawn across the the evaporator coil by its associated blower
(not
shown), or any other kind of ice sensor, Alternatively, the defrost cycle can
be initiated
by timer means or other programmed control sequence or by manual switching.
The
superconductor defrost exchanger system 170 represents an advance by enabling
a
conventional refrigerant system to remain in one operating mode instead of
reversing
valve position, eliminating reversing the trouble prone reversing valve and
increasing
reliability and overall operating efficiency.
Figures 8-10 illustrates several alternate embodiments showing
superconductor defrost system 180. In these embodiments, the defrost heat
source
substitutes a fluid loop 80 connected to a remote thermal system for the
external heat
exchanger using air exchange. In the preferred embodiment Figure 8, the fluid
loop is
the hot refrigerant loop of a conventional refrigeration system. In this
embodiment, the
remote conventional refrigeration system (not shown) operates to remove heat
from at
least one refrigerating heat exchanger (not shown. This heat is then
transferred through
heat exchanger 77 to the defrost intensifier subsystem by thermal
superconductor pipe
78 which is coupled with low thermal losses. Heat is then intensified and
transferred to
defrost heat exchange segment 42 where it is then transferred to the
associated
evaporator coil (not shown) of a conventional refrigerating heat exchanger for
the
purpose of melting any build up of ice. As will be obvious to one skilled in
the art of
conventional refrigeration systems, the evaporator coil (not shown) receiving
the heat
from superconductor defrost system 180 can equally be part of the remote
conventional
refrigeration system providing the heat, or part of a second, separate
conventional
refrigeration system. In this process, hot refrigerant gas flows into heat
exchanger 77
through refrigerant inlet 81, gives up heat to superconductor heat exchange
element 78
as the refrigerant passes through condenser coil 80, condensing in the
process, and
then flows out of heat exchanger 77 through refrigerant outlet 83. The heat
absorbed
by superconductor heat exchange element 78 is transferred by superconductor
transfer
CA 02530621 2006-01-03
32
segment 34 to the heat intensification circuit where it is intensified and
transferred by
superconductor transfer segment 32 to defrost heat exchanger 42. Controller 16
initiates the operation of the defrost cycle in response to defrost sensor 18,
or as
programmed by periodic timing, and operates the compressor until programmed
desired
sensor setting is reached, or programmed defrost duration is reached. For the
case of
large industrial refrigeration plants with many dissipating heat exchangers in
proximity to
refrigeration spaces, this defrost embodiment solves the problem of
efficiently reusing
dissipated heat near it's source without increasing ambient temperatures,
rather than
inefficiently transporting it and wasting it. This is of particular value
where high external
or internal ambient temperatures make heat dissipation inefficient
Also included in Figure 8 is an optional thermal transfer bypass route,
comprised of superconductor thermal transfer segments 44, 46 and thermal
switch 35,
which enables superconductor transfer segments 32 and 34 to be directly
thermally
coupled as shown, such that heat is not required to pass through the heat
intensification
circuit to transfer between the superconductor transfer segments. When
controller 16
determines by way of heat flow sensor 84 that the heat content of fluid 94 is
sufficient
without intensification for the purpose of melting ice at greater than a
programmed
threshold de-icing rate determined by the approximate volume of ice,
evaporator
configuration and refrigeration space temperature, at the refrigerating heat
exchanger
(not shown) associated with superconductor defrost segment 42, the controller
causes
compressor 24 to be stopped if operating, and switch 35 to be set in an "on"
position,
causing superconductor transfer segments 32 and 34 to be thermally coupled,
transferring heat directly from superconductor heat exchange segment 107 to
defrost
heat exchange segment 42.
Figure 9 shows a variant of the defrost system 180 in which a fluid 94
stores and transfers heat but remains contained within tank 98. In a preferred
embodiment, a separate system (not shown) causes a heated refrigerant to flow
through refrigerant inlet 81 into tank 98, passing through condenser coil 80,
giving up
CA 02530621 2006-01-03
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heat to fluid 94 before condensing and flowing out of the tank through
refrigerant outlet
83. Similar to Figure 4, heat is absorbed by superconductor heat exchange
segment
104 positioned in storage tank 98 and transferred to the heat intensification
circuit.
Alternatively, the separate system (not shown) can equally be any circulating
fluid heat
transfer system and condenser coil 80 can equally be any heat exchange coil
suited to
the purpose of transferring heat from one fluid to another. A temperature
sensor 84 can
provide an optional feedback to controller 16 for information on the heating
state and
cycle of the fluid 94. A bypass switch 35 is optionally provided as described
previously.
Figure 10 illustrates an alternative embodiment of the defrost system 180
which
uses a directly exchanged fluid such as grey water, sea water, pond water or
the like as
the heat source. In this embodiment, a fluid 94 from a separate system (not
shown)
flows into tank 98 through fluid inlet 101 and flows out through fluid outlet
102.
Superconductor heat exchange segment 104 is located in the storage tank 98 and
absorbs heat from the fluid 94 and transfers it by way of superconductor
transfer
segment 34 to the heat intensification circuit, where the heat is intensified
before being
transferred to defrost heat exchange element 42. A temperature sensor 96 can
provide
an optional feedback to controller 16 for information on the heating state and
cycle of
the fluid 94. A bypass switch 35 is optionally provided as described
previously.
The rapid defrost cycle enabled by the defrost systems shown in Figures 1-10,
allows
for more frequent defrost cycles for shorter durations which leads to an
increased
average air flow path over the evaporator fins, resulting in improved
effective cooling
rates over existing conventional systems which must tradeoff air flow
restriction versus
longer defrost downtime.
Figure 11 illustrates a simplified alternative embodiment of the defrost
system illustrated in Figures 8-10, which is operable when the heat content of
the
remote hot refrigerant gas flowing through condenser coil 80 is sufficient,
without
intensification, for the purpose of melting ice at the refrigerating heat
exchanger (not
CA 02530621 2006-01-03
34
shown) associated with superconductor defrost segment 42. In this embodiment,
heat is
absorbed from condenser coil 80 by superconductor heat exchange segment 78 and
transferred by superconductor transfer segment through thermal switch 35 to
superconductor transfer segment 38 which transfers it to superconductor
defrost
segment 42. In operation, controller 16 determines (by timer program or
through a
signal from ice sensor 18) that defrost heat is required by superconductor
defrost
segment 42, and closes thermal switch 35, causing heat to flow from heat
exchanger 77
to defrost segment 42. In this embodiment, controller 16 can be located on its
own or
can be integrated into the controller of the refrigeration system (not shown)
as a
separate function of the refrigeration controller. In an alternate version,
enclosure 12
can be modified to enclose also thermal switch 35, and have optional fastening
features
to be mounted to or in the remote heat exchange module housing 77a. The
simplified
superconductor defrost system represents an advance in retrofitting existing
refrigeration systems with minimal additional electrical power required,
through
operation of an efficient heat exchange system to reuse available heat, and
through
very compact installation. Alternate embodiments of system 190 could of course
use
any of the liquid exchange configurations described in Figures 8-10.
Figure 12 illustrates an alternative embodiment of the defrost system,
having multiple discrete defrost exchangers. Defrost system 200 shows two
defrost
exchangers 42 and 42a coupled through discrete thermal switches 35 and 35a, to
the
common superconductor heat exchange pipe 40/40a which terminates in coupling
78 to
the remote heat exchanger 77. In defrost operation, heat absorbed by
superconductor
heat exchange segment 78 is transferred by way of superconductors 40 and 40a
to a
plurality of thermal switches 35, 35a and then to a plurality of
superconductor transfer
segments 38, 38a, and finally to a plurality of superconductor defrost
segments 42, 42a
for the purpose of defrosting ice from evaporator coils associated with each
defrost
exchange (not shown). When controller 16 determines by way of heat flow sensor
84
that the heat content of fluid 94 is sufficient without intensification for
the purpose of
melting ice at greater than a programmed threshold de-icing rate determined by
the
approximate volume of ice, evaporator configuration and refrigeration space
CA 02530621 2006-01-03
35
temperature, at the refrigerating heat exchanger (not shown) associated with
superconductor defrost segment 42. There could be two thresholds, one suitable
for a
single defrost mode operation, and a second higher heat flow threshold to
allow
simultaneous heat flow to multiple defrost exchangers. In an alternate
version,
enclosure 12 can be modified to enclose also both thermal switches 35 and pies
40 and
40a, and have optional fastening features to be mounted to or in the remote
heat
exchange module housing 77a. In this embodiment, controller 16 operates
switches 35
and 35a independently so that the defrost segments can at any time be
independently
coupled to or decoupled from heat exchanger 77, and the rate and quality of
heat
exchanged at heat exchanger is preferably above a threshold for simultaneous
defrosting.
Figure 13 illustrates one embodiment of the superconducting heat
exchanger in Figures 1 to 7. In this embodiment, superconducting defrost heat
exchange segment 42 is configured as a superconductor array coupled to
optional heat
transfer fins 68 to distribute heat across a larger surface area in order to
efficiently
transfer heat to the air being drawn across the heat exchanger by blower 55.
In an
alternative embodiment, superconductor defrost segment 42 can be configured
with
sufficient surface area such that it can transfer heat as required without the
addition of
heat transfer fins. An optional drip tray 56 and drip line 58 is illustrated,
including an
optional superconductor branch positioned in the drip tray to defrost the drip
tray if
necessary. It will be appreciated that the superconductor heat exchanger can
be
configured differently from the illustration for specific installations
without changing the
functionality.
Figure 14 a-c, illustrate a conventional phase change refrigeration
evaporator with the addition of a superconducting defrost component, as
described
above for figures 8 to 12. The evaporator operates in the conventional manner
as part
of a refrigeration system. Liquid refrigerant supply subsystem 66 causes
liquid
refrigerant to expand and become a super-cooled partial liquid as it flows
into
CA 02530621 2006-01-03
36
evaporator loops 69, absorbing heat from heat transfer fins 67 before flowing
out of
evaporator loops 69 into refrigerant vapor return subsystem 65 and then back
to the
remainder of the refrigeration system (not shown). The heat transfer fins 67
have
additional sleeves 63 enabling superconductor defrost segment 42 to be
inserted for the
purpose of delivering heat to melt ice that has built up on surfaces of the
evaporator
assembly. Water produced by the melting of ice is collected in drip tray 56
(which is
also heated by superconductor defrost segment 42) and is drained away to a
suitable
location through drain line 58. Figure 14a illustrates the conventional
evaporator
assembly with other components removed for clarity. Figure 14b illustrates an
evaporator unit with superconducting defrost array 42 permanently installed,
or
alternatively, with removable superconducting defrost array 42 inserted for
operation.
Figure 14c illustrates a superconducting defrost array 42 ready for insertion
into sleeves
63 to complete the refrigerating / defrosting heat exchange unit. As will be
obvious to
one skilled in the art, there are various coupling methods to couple the metal
superconductor pipe to the typically metal fins. The defrost transfer element
42
represents an advance in that the heat transfer efficiency is so dramatically
great that a
wide range of couplings and tolerances with various retrofitted evaporator
designs still
allows the defrost system to be enabled, specifically the thermal
superconductor may
not require bonding, welding or other processes but can simply be press-fit.
Figure 15 illustrates an alternative embodiment of the superconductor
defrost evaporator system 230. In this embodiment, superconducting defrost
segment
42 is mounted to one side of the evaporator assembly such that heat from
superconducting defrost segment 42 is transferred to heat transfer fins 67 for
the
purpose of melting ice that has built up on the surface of heat transfer fins
67 and
evaporator loops 69. Superconducting defrost segment 42 can alternatively be
mounted
to both sides of the evaporator assembly for additional defrost capacity.
Superconducting defrost segment 42 can alternatively be configured to be
removable
from the face of the evaporator assembly so as to decrease the wind resistance
to air
being blown through the assembly. This example allows for convenient in-situ
CA 02530621 2006-01-03
37
installation within the refrigeration space, without alteration of the
conventional
refrigeration heat exchanger.
Figure 16 illustrates a typical configuration of refrigeration system 130 in a
building 116. A space to be refrigerated is enclosed by room 118, having
access door
117 such that materials can be transported in and out. The internal average
temperature is shown as T1. Also within building 130 is a refrigeration plant
enclosed in
housing 12, of the type described herein, the internal temperature outside
room 118 is
T2. Suspended in refrigerated room 118 are refrigerating heat exchanger
housings 60
and 60a which house refrigerating heat exchange segments, blowers, sensors and
other associated equipment (all not shown) of the superconductor refrigeration
systems.
Superconducting heat transfer segments 38 and 38a thermally couple the
refrigerating
heat exchange segments with thermal switches 64a and 64b in refrigeration room
12.
Thermal switches are in turn coupled to both condensing heat exchanger 21 and
evaporating heat exchanger 28, which are part of a heat intensification
circuit with a
phase change refrigerant fluid (not shown) circulated by compressor 24, which
receives
control signals from thermostat controller 16. Heat absorbed by the
refrigerating heat
exchange segments (not shown) is transferred to evaporator heat exchanger 28,
intensified by the heat intensification circuit, transferred by condensing
heat exchanger
21 to thermal switch 64b and then by superconducting thermal transfer segment
40 to
external heat exchanger in housing 86 outside building 116, where this heat is
then
dissipated into the atmosphere, having temperature T3. Not shown are
additional
refrigeration plants or remote heat exchangers that the illustrated
refrigeration plant may
couple to. As previously described, refrigeration system operates in a
refrigerating
mode when T1 is above a programmed thermostat setpoint. The higher external
temperature T3 is, the blower (not shown) speed can be increased by controller
16 to
adjust the corresponding heat transfer rate to external air. The external
dissipation of
heat, maintains internal temperature T2 at acceptable limits.
Further, in all described embodiments of a refrigerating or defrosting
system, the blower associated with the refrigerating heat exchanger can be a
variable
CA 02530621 2006-01-03
38
speed controller with speed controlled by the thermostat controller in
response to the
difference between a desired temperature setpoint and measured temperature of
the
refrigeration space. Additionally for all cases, the variable speed blower can
be
connected to the thermostat controller to enable this control.
Throughout these examples and embodiments described, insulation has
been shown on superconductor segments designed for low thermal loss transfer
(i.e.
not the ends of the superconductor segments), and is the preferred example,
whether or
not explicitly stated in figure descriptions or numbered on drawings. However,
as noted
previously, the superconductor geothermal exchange systems described will
operate
with no insulation or with some transfer lines insulated or any combination of
insulated
or un-insulated portions of the superconductors thereof.
CA 02530621 2006-01-03
