Patent Application
20070209380
The present invention relates generally to refrigeration systems, and more particularly to a refrigeration heat exchanger having a superconducting heat transfer element.
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 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 similar. 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 employed 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 employed to defrost the heat exchanger in 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 operated 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 is 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 employed 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 decrease heat stress, operated in reverse long enough to defrost the refrigerating heat exchanger, stopped, and then gradually reversed to decrease heat 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 can 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. 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 be 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 a 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 per unit power. There is further a need for a non-refrigerant based defrosting element for use in combination with a conventional refrigeration system.
A refrigeration system incorporates thermal superconducting heat transfer. The system includes an intensifying heat exchanger, a refrigerating heat exchange coil formed from thermal superconductor material, and a dissipating heat exchange coil formed from thermal superconductor material. The system can include a switch connected to condenser and evaporator heat exchange segments, a refrigeration switch segment and a dissipating switch segment such that in a first switch position a refrigerating mode is provided and in a second switch position a defrost mode is provided. Additional embodiments include thermostat controllers and blowers for enhanced control. Heat exchange and reuse is described for multiple heat exchangers coupled by thermal superconductors. A defrosting element is described for refrigeration heat exchangers.
In one embodiment, a refrigeration system having thermal superconducting heat transfer includes a reversible intensifying heat exchanger, having a compressor, a refrigerating heat exchange coil formed from thermal superconductor material, and a dissipating heat exchange coil formed from thermal superconductor. The refrigeration system also has a reversing valve that can be configured to provide corresponding refrigerating or defrosting modes of the superconductor refrigeration system. The refrigerating or defrosting modes can be selected by a thermostat controller for the purpose of operating in a refrigerating or defrosting mode to refrigerate a space.
In a further embodiment, a defrosting system having thermal superconducting heat transfer includes an intensifying heat exchanger, a defrosting heat exchange coil formed from thermal superconductor material, an absorbing heat exchange coil formed from thermal superconductor material, and a controller programmable to a desired set point and further having a thermostat controller connected to the thermal switch and compressor.
In a further embodiment, a superconductor refrigeration exchange element includes a plurality of evaporator refrigerant conduits suitable for receiving refrigerant; an evaporator coupled to ends of each of the plurality of refrigerant coils, a condenser conduit coupled to opposing ends of each of the plurality of refrigerant coils; a plurality of cooling plates formed of a thermally conductive material arranged in a approximately co-planar stack, and having at least one conduit opening through each of the plates corresponding to each refrigerant conduit such that the conduits are seated in thermal contact within the cooling plate stack for the purpose of exchanging heat with air; a thermal superconductor heat transfer pipe arranged such that a coupling portion is coupled on at least one side of the cooling plate 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 increase available air flow through the plates, and a transfer portion extends away from the stack of plates. In addition, insulation surrounds at least part of the extended transfer portion to reduce heat transfer loss. Heat is 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 approximately maintained.
a is a schematic diagram of a refrigeration system with thermal superconductor heat exchangers and a reversible superconductor transfer switch enabling the system to switch from refrigeration to defrost.
a is a schematic diagram 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.
b is a schematic diagram of a defrost system using waste heat indirectly from the hot vapor line of a conventional refrigeration system through a liquid heat exchange fluid.
c is a schematic diagram of a defrost system using waste heat from a circulating fluid from another heat generating system.
a is a schematic diagram 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.
b is a schematic diagram of a defrost system using waste heat indirectly from the hot vapor line of a conventional refrigeration system through a liquid heat exchange fluid, without the assistance of a heat intensification circuit.
a is a cut-away view of a conventional refrigerating heat exchanger showing the fluid flow path.
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 technology.
Recent advances in thermal superconducting materials can now be considered for use in novel energy transfer applications. For example, U.S. Pat. Nos. 6,132,823, 6,916,430 and 6,911,231 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. The term superconductor can interchangeably mean thermal superconductor. For illustrative purposes, this superconductor can 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 can have various forms and cross sections such as flexible conduits, thin laminate, thin film coated metal etc. Optionally, the superconducting transfer segments can be formed from discontinuous discrete sections of superconducting material separated by small gaps of a non-superconducting material.
An embodiment of the present technology 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. 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 can include:
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 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. Second, thermal superconductors have the capacity to transfer heat over relatively long distances with limited 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 limited 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 reversing valves, many 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.
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 from one heat exchanger to another in the system so that waste heat produced by a refrigeration unit can be employed to defrost the heat exchanger in another refrigeration unit. Second, it allows waste heat to be moved 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.
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 via conduit 27 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. The compressor is controllable through control line 22 connected to controller 16. 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 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. An 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 2×2 thermal switch 36 connected to control line 20.
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 United States Patent Application “Geothermal Exchange System Using a Thermally Superconducting Medium,” filed Sep. 14, 2006, incorporated herein for reference. Alternately, the thermal switch can 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 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. An apparatus for intensifying heat can equivalently substitute for the refrigerant based heat intensifier circuit illustrated.
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 through respective control lines 52 and 52a. As will be appreciated, variations of this example can include independently connected compressor or blower power or multiple control systems without changing functionality. Refrigerating heat exchange coil 42 can be configured in a geometric arrangement to improve 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 a geometric arrangement to improve 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 set point and the measured temperature from sensor 18. Defrost mode can be programmed for periodic maintenance based on empirical understanding of ice buildup, or an additional ice buildup sensor (not shown) can be added with a set point 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 this heat 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 can be local and dedicated to the refrigeration system shown, or can 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 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 transferred through superconductor transfer segment 38 to refrigeration space exchange coil 42, causing it to heat up and melt 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 can be located for effective monitoring of degree of melted ice on the heat exchanger, or an additional defrost sensor (not shown) can be included and connected to controller 16. The modes can simply switch on/off or alternatively oscillate between refrigerating and defrosting based on programming of controller 16, however as is evident from
The intensifier circuit can have additional components as required to scale for larger energy applications, for example where the refrigeration space is very large and partially open for storage access. As shown in
Using the preferred thermal superconducting tubes, it is preferred to have insulation 25 along the length of 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 can 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. The components can be housed inside one enclosure to comprise a unit refrigerator. Alternatively, as shown in
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
As shown in refrigeration system 140 in
The embodiments shown in FIGS. 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 FIGS. 1 to 4 can be modified by adding reversing valve 77 in the intensifier circuit and eliminating thermal switches as shown in the refrigerating heat exchange system 150 of
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 bidirectional 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 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 bidirectional 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 capacity, the volume of refrigerant inhibits reversal and creates a delay time during which the system is inoperable or inefficient. This effect is reduced relative to a full conventional circulation.
Refrigeration system 160 in
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 FIGS. 1 to 4, no other operating modes described for FIGS. 1 to 4 are enabled.
All refrigerating systems shown in FIGS. 1 to 6 operate in both refrigeration and defrost modes, and in some cases mixed modes. In some applications a system will not 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.
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 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 evaporator coil by its associated blower (not shown), or another kind of ice sensor. Alternatively, the defrost cycle can be initiated by a timer 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.
a,b,c 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 in place of the external heat exchanger using air exchange. In a preferred embodiment
Also included in
b 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 heat to fluid 94 before condensing and flowing out of the tank through refrigerant outlet 83. Similar to
c 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
a illustrates a simplified alternative embodiment of the defrost system illustrated in
a-c, illustrate a conventional phase change refrigeration evaporator with the addition of a superconducting defrost component, as described previously for FIGS. 8 to 10, to form refrigerating and defrosting heat exchange unit 220. 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 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.
Further, the blower associated with the refrigerating heat exchanger can be a variable speed controller with speed controlled by the thermostat controller in response to the difference between a desired temperature set point and measured temperature of the refrigeration space. Additionally, the variable speed blower can be connected to the thermostat controller to enable this control.
In 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 a combination of insulated or un-insulated portions of the superconductors thereof.
In these examples housing has been described as split housing in a preferred case, however it will be appreciated that the various embodiments can be integrated into existing structures or enclosed in a single housing.
Although particular embodiments of the present technology have been described by way of example, it will be appreciated that additions, modifications and alternatives thereto can be envisaged. The scope of the present disclosure includes a novel feature or combination of features disclosed therein either explicitly or implicitly or generalization thereof irrespective of whether or not it relates to the claimed invention or mitigates one or more of the problems addressed by the present invention. The applicant hereby gives notice that new claims can be formulated to such features during the prosecution of this application or of such further application derived there from. In particular, with reference to the appended claims, features from dependent claims can be combined with those of the independent claims and features from respective independent claims can be combined in an appropriate manner and not merely in the specific combinations enumerated in the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,530,621 | Jan 2006 | CA | national |
