Method to Mitigate Catastrophic Failure of HVACR Equipment Charged with A3 Refrigerants

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to 63/635,818 filed on Apr. 18, 2024, entitled “METHOD TO MITIGATE CATASTROPHIC FAILURE OF HVACR EQUIPMENT CHARGED WITH A3 REFRIGERANTS”, the entire disclosure of which incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

The technologies described herein were developed with government support under Contract No. DE-AC05-00OR22725 awarded by the U.S. Department of Energy. The government has certain rights in the described technologies.

FIELD OF THE INVENTION

The present invention is directed to HVACR devices, and particularly to HVACR devices with flammable low Greenhouse Warming Potential (GWP) refrigerants.

BACKGROUND OF THE INVENTION

Historically, heating, ventilation, air conditioning, and refrigeration (HVACR) systems utilized either a chlorofluorocarbon (CFC) refrigerant, which was phased out in the mid-1990s due to its impact on the ozone layer, or a hydrofluorocarbon (HFC) refrigerant, which is currently subject to a global phase-down due to its high global warming potential. Since a decade ago, new hydrofluoroolefin (HFO) refrigerants have begun to replace HFCs. However, the A3 class of refrigerants, which are highly flammable, are being actively pursued as alternatives to HFOs due to various environmental concerns.

Industrial safety standards and general guidelines for the storage and handling of flammable refrigerants and gases in HVACR systems is slowly emerging. In addition, diffusion, and dispersion modeling to determine the hazardous zones created by the release of flammable gases is unique to individual equipment and installation.

OEMs of HVACR systems must eliminate risks associated with the system as far as reasonably practicable. This includes risks to people who install, maintain, construct, dispose of or use the system, and those in the vicinity of the system at a workplace. Proposed engineering solutions to minimize the risk involves leak sensing to trigger a system or subsystem shutdown and upgrading the system to use hazardous environment rated instrumentation. However, the diffusion of leak is highly subjective to the installation and operational environment where it is possible for the flammable gas to leak out of the system and create a potentially risky hazardous zone outside the installed equipment. It is hence very important that any leak incidents are contained within the installed equipment.

SUMMARY OF THE INVENTION

A heating, ventilation, air conditioning, and refrigeration (HVACR) system chargeable with a refrigerant in a closed refrigeration cycle includes an HVACR enclosure, a vent outlet fluidly coupled with the HVACR enclosure for discharging air from the HVACR enclosure, and a refrigerant retention device. The refrigerant retention device is positioned to contact air and escaped refrigerant that has been emitted from the closed refrigeration cycle prior to discharge of the air from the vent outlet. The refrigerant retention device comprises a porous refrigerant retention material which passes air to the vent outlet and retains the escaped refrigerant. The air discharged from the HVACR system can have a concentration of refrigerant below the critical combustion concentration for the refrigerant in air.

The HVACR system can further include a gas pump operable to move air and escaped refrigerant from the HVACR enclosure through the vent outlet and a sensor for detecting the presence of the refrigerant in the HVACR enclosure. The sensor upon detection of escaped refrigerant operates the gas pump to move the air and escaped refrigerant into contact with the refrigerant retention material, and the refrigerant retention material will retain the escaped refrigerant gas.

The vent can include a valve. The valve can include a motor. The motor is operable upon receipt of a signal from the sensor. The HVACR system can further include a processor for operating the sensor and the gas pump. The gas pump can comprise at least one selected from the group consisting of a vacuum pump and a blower fan.

The refrigerant retention material retains at least one refrigerant selected from the group of propane, butane, pentane, R32, R1234ze, R448A, R407F, and R1234yf. The porous material of the refrigerant retention material can comprise pores having a diameter of from 4°A to 5° A. The refrigerant retention material can be at least one selected from the group consisting of zeolites, activated alumina and activated carbon.

The refrigerant retention device can be provided as a cartridge. The HVACR enclosure can include structure for removably retaining the cartridge. The HVACR enclosure can include walls, and the cartridge can be removably connectable to at least one of the walls. The vent inlet can be positioned in at least one of the walls to draw air and escaped refrigerant through the cartridge. The vent can comprise a vent tube. The refrigerant retention material can be provided in the vent tube. The vent tube can include a vent lid at a discharge end of the vent tube and a valve at an inlet end of the vent tube.

The HVACR system can comprise at least one selected from the group consisting of a refrigerator, a freezer, a combination refrigerator and freezer, a central air conditioner, a room air conditioner, a heat pump air conditioning and heating systems, a heat pump water heater, a walk-in freezer, a walk-in cooler, a cold/frozen food display case, an ice-cream machine, frozen food vending machines, cold beverage vending machines. The HVACR enclosure can be part of a refrigerator and encloses the compressor and the condenser of the closed refrigeration cycle.

A method for operating an HVACR system can include the step of providing an HVACR enclosure; a sensor for detecting the presence of the refrigerant in the HVACR enclosure; a vent having a vent outlet fluidly coupled with the HVACR enclosure for discharging air from the HVACR enclosure; a gas pump operable to move air and escaped refrigerant from the HVACR enclosure through the vent outlet; and a refrigerant retention device positioned to contact air and escaped refrigerant that has been emitted from the closed refrigeration cycle prior to discharge of the air from the vent outlet, wherein the refrigerant retention device comprises a porous refrigerant retention material which passes air to the vent outlet and retains the escaped refrigerant. Escaped refrigerant is detected with the sensor. The gas pump is operated in response to the detected escaped refrigerant. The gas pump is used to direct air and escaped refrigerant to contact the refrigerant retention material in the refrigerant retention device, whereby the escaped refrigerant will be retained by the refrigerant retention material.

The method can include the step of removing and replacing the refrigerant retention material. The method can further comprise the step of regenerating the refrigerant retention material. The method provides air discharged from the vent having a concentration of refrigerant that is below the critical combustion concentration for the refrigerant in air

BRIEF DESCRIPTION OF THE DRAWINGS

There are shown in the drawings embodiments that are presently preferred it being understood that the invention is not limited to the arrangements and instrumentalities shown, wherein:

FIG. 1 is a perspective view of an HVACR system according to the invention, in a first mode of operation.

FIG. 2 is a perspective view of the HVACR system in a second mode of operation, and with refrigerant retention devices partially removed for ease of viewing and understanding.

FIG. 3 is a perspective view, partially in phantom, of an alternative HVACR system embodiment in a first mode of operation.

FIG. 4 is a perspective view, partially in phantom, of the alternative HVACR system embodiment in a second mode of operation.

FIG. 5 is a perspective view, partially in phantom, of the alternative HVACR system embodiment in a third mode of operation.

FIG. 6 is a partial cross section of the alternative HVACR system in the third mode of operation.

FIG. 7 is a cross section of a refrigerant retention material in operation.

FIG. 8 is an exploded schematic perspective of an HVACR system with a refrigerant retention vent pipe system.

FIG. 9 is a schematic diagram of a building having an HVACR system according to the invention.

FIG. 10 is schematic perspective view of a walk-in cooler HVACR system according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

A heating, ventilation, air conditioning, and refrigeration (HVACR) system that is chargeable with a refrigerant in a closed refrigeration cycle comprises an HVACR enclosure. A vent outlet is fluidly coupled with the HVACR enclosure for discharging air and leaked refrigerant from the HVACR enclosure. A refrigerant retention device is positioned to contact air and escaped refrigerant that has been emitted from the closed refrigeration cycle prior to discharge of the air from the vent outlet. The refrigerant retention device comprises a porous refrigerant retention material which allows air to pass through the vent outlet and retains the escaped refrigerant.

A gas pump can be provided and is operable to move air and escaped refrigerant from the HVACR enclosure through the vent outlet. A sensor can be provided for detecting the presence of the refrigerant in the HVACR enclosure. The sensor upon detection of escaped refrigerant can operate the gas pump to move the air and escaped refrigerant into contact with the refrigerant retention material, and the refrigerant retention material will retain the escaped refrigerant gas.

The HVACR enclosure can be a part of an existing HVACR system design or can be an enclosure specifically designed for the invention. The HVACR refrigeration cycle commonly includes a compressor, a condenser, an expansion valve, and an evaporator, all connected by a refrigerant conduit circuit. Refrigerant leaks can occur in any part of the refrigerant circuit. Other refrigeration cycle designs are possible for use with the invention. Typically, one or more of these components is provided in an enclosure of some kind, which has at least one outlet opening to the allow ambient air to circulate across the compressor and condenser and remove heat from these components. It is also possible to fashion a separate enclosure to facilitate the capture of escaped refrigerant before it is released to the surrounding atmosphere.

A valve can be associated with the vent outlet. The valve can comprise a motor, and the motor can be operable upon receipt of a signal from the sensor. The vent outlet can be provided by a vent tube, and the refrigerant retention material can be provided in the vent tube. The vent tube can comprise a vent lid at a discharge end of the vent tube and a valve at an inlet end of the vent tube.

A processor can be provided for operating the sensor and the gas pump, as well as other system components. The processor can communicate with these components by wired or wireless communications. The processor can also communicate with remote wireless devices such as cell phones, tablets or computers to provide alarms or signals to a home-owner or operator of leak detection, or generally system status.

The refrigerant retention material retains at least one refrigerant selected from the group of propane, butane, pentane, R32, R1234ze, R448A, R407F, and R1234yf. Other refrigerants are possible. The invention is particularly useful to capture escaped flammable low Global Warming Potential (GWP) refrigerants. The invention can also be used to capture currently used higher GLP refrigerants which may or may not be flammable or otherwise harmful, but the escape of which would contribute to global warming. The invention can also be used to reduce the emissions of such higher GWP refrigerants.

The porous refrigerant retention material can be any suitable material or filter for the particular refrigerant that is to be captured. The refrigerant retention material can comprise pores greater than 4° A and less than the critical diameter of the target molecule, typically 4-5° A, and capable of binding to or otherwise retaining the refrigerant being used in the HVACR system. The critical diameter of oxygen and nitrogen is around 3°A compared to ˜5° A for most of the refrigerants. In this regard, a pore diameter of 4°A and above (up to 5° A) will be clogged with refrigerant while the air molecules will be permitted to pass through the refrigerant retention material. In a non-functionalized sorbent the mechanism is driven by the shape and diameter of the molecule in question. The pore diameter of the refrigerant retention material can be 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5 oA, and can be within a range of any high value and low value selected from these values. Other pore sizes are possible.

The refrigerant retention material can comprise, but is not limited to, at least one selected from the group consisting of zeolites, activated alumina and activated carbon.

The refrigerant retention device can be a cartridge. The cartridge contains the refrigerant retention material and has suitable construction and/or openings such that air and refrigerant gas can pass through and contact the refrigerant retention material, wherein the refrigerant gas will be retained by the refrigerant retention material and air will be permitted to pass thought the cartridge to at least one cartridge outlet opening and leave the cartridge and the HVACR system. The provision of a cartridge allows for the replacement of the refrigerant retention device, and the HVACR enclosure comprises structure for removably retaining the cartridge. The HVACR enclosure can comprises walls. The cartridge is removably connectable to at least one of the walls. The vent inlet is positioned in or adjacent to at least one of the walls so as to draw air and escaped refrigerant through the cartridge.

The removal of all of the escaped refrigerant is desirable but some escape of small amounts of refrigerants is possible. Such escape though less desirable is not necessarily dangerous. Flammable gases have a critical concentration in air above which an explosion is possible with a suitable ignition source such as a spark. The HVACR system of the invention can provide that air discharged from the vent has a concentration of flammable refrigerant below the critical combustion concentration for the refrigerant in air.

The gas pump can be any suitable device for moving air and leaked refrigerants, such as fans, blowers and reciprocating pumps. Due to the flammable nature of some of the refrigerants the gas pump can be designed to minimize the creation of sparks or undue heat. The gas pump can comprise at least one selected from the group consisting of a vacuum pump and a blower fan.

The HVACR enclosure can be part of a refrigerator and encloses one or more of the compressor and the condenser of the closed refrigeration cycle, and/or other refrigeration components. Such spaces already exist on many HVACR devices and are comprised of walls which can be of many shapes and construction, and one or more outlet openings which allow for air to circulate and cool these components.

The HVACR system can be part of many different kinds of HVACR systems. The HVACR system can comprise at least one selected from the group consisting of refrigerators, freezers, combination refrigerators and freezers, central air conditioners, room air conditioners, heat pump air conditioning and heating systems, heat pump water heaters, walk-in freezers, walk-in coolers, cold/frozen food display cases, ice-cream machines, frozen food vending machines, and cold beverage vending machines.

A method for operating an HVACR system includes the step of: providing an HVACR enclosure, a sensor, a vent outlet, a gas pump, and a refrigerant retention device. The sensor detects the presence of the refrigerant in the HVACR enclosure. The vent has a vent inlet fluidly coupled with the HVACR enclosure, and a vent outlet for discharging air from the HVACR enclosure. The gas pump is operable to move air and escaped refrigerant from the HVACR enclosure through the vent outlet. The refrigerant retention device is positioned to contact air and escaped refrigerant that has been emitted from the closed refrigeration cycle prior to discharge of the air from the vent outlet. The refrigerant retention device comprises a porous refrigerant retention material which passes air through the vent outlet and retains the escaped refrigerant.

The sensor can be to detect escaped refrigerant. The pump is operated in response to the detected escaped refrigerant. The gas pump directs air and escaped refrigerant to contact the refrigerant retention material in the refrigerant retention device. The escaped refrigerant is retained by the refrigerant retention material.

The method can further include the step of removing and replacing the refrigerant retention material. This replacement can be the replacement of a cartridge containing the refrigerant retention material. The method can include a step of regenerating the refrigerant retention material. The air discharged from the vent has a concentration of refrigerant below the critical combustion concentration for the refrigerant in air

The invention can mitigate the explosion risk in a vacuum swing adsorption system loaded with hydrocarbon selective active materials as the refrigerant retention material to trap the hydrocarbon in the porous structure of the high surface area refrigerant retention material dispersed in the encasement walls in a modular honeycomb filter architecture.

A leak detection event will trigger a gas pump such as a vent fan to draw the fluid present inside the HVACR enclosure towards the walls and through the refrigerant retention device. The hydrocarbon/air mixture passes through the refrigerant retention material where the flammable gas molecules are trapped, partially or completely, within the constraints of the porous body of the refrigerant retention material via physisorption, or chemisorption or catalytically enhanced chemisorption.

The air stream exiting the system will be depleted with hydrocarbons, avoiding the risk of a potential explosion. The controls for such a solution can be integrated with a master controller or processor where an output signal from a leak detector is configured to trigger the gas pump. The method can also be used for mitigating leakage of nonflammable refrigerants where high global-warming potential (GWP) values and their release into atmosphere can be mitigated significantly.

Solid-gas interactions enabled by shape-selective structures, molecular attractive forces, polarization, and catalytic activation can be used for the refrigerant retention material. Activated carbons, zeolites, and various metal oxides can be tailored to target a molecule of interest, such as propane, isobutane, pentane, etc., by engineering the microporous structure as well as chemically functionalizing the surface to attract and hold on to the chemical compound being removed from the gas stream.

Additionally, depending on the physicochemical properties of the refrigerant molecule, one can use acoustic resonance excitation, electrostatic and magnetic fields, ionization to further enhance the dispersion of the leaked gas uniformly throughout the HVACR cabinet/enclosure in guiding the molecules towards the disclosed active filter/trap.

There is shown in FIGS. 1-2 an HVACR system 10 which includes a compressor 24, a condenser 30, and an evaporator 36 (shown in phantom). The refrigeration cycle and components can be selected from known components. As is known, refrigerant can be conveyed from the compressor 24 to the condenser 30 by a suitable refrigerant conduit 28. Refrigerant can be conveyed from the condenser 30 to the evaporator 36 by a refrigerant conduit 32. Refrigerant can be conveyed from the evaporator to the compressor 24 by a refrigerant conduit 38. Other connections or additional connections are possible.

All or some of the refrigeration cycle components such as the condenser 24 and compressor 30 can be contained within an HCACR enclosure 14 which can have side walls 40 and 42, top 44, bottom 46, rear 48, and can have an access panel or door 50. Many different designs, sizes and variations of the HVACR enclosure 14 are possible. The HVACR enclosure 14 can be part of a larger HVACR system that includes a refrigeration compartment such as for a freezer or a fresh foods storage compartment, a condenser unit and an air handler unit, or a walk-in cooler, or can be a stand-alone HVACR unit. The HVACR enclosure 14 can have a number of vent outlet openings 54 to the surroundings for purposes of cooling the compressor 24 and/or the condenser 30.

Interior walls 56, 57 can be provided and can have interior openings 58 to permit the passage of leaked refrigerant gas can be connected to top 61 and bottom 63 to form an interior shell within the HVACR enclosure 14 in which the compressor 24 and condenser 30 are contained. Refrigerant retention devices such as cartridges 60 and 62 containing a refrigerant retention material 66 are positioned between the interior wall 56 and exterior wall 42, in between the interior wall 57 and exterior wall 40.

As shown in FIG. 2, whenever a leak exists in some part of the refrigeration system components such as for example the compressor 24 as shown, refrigerant 70 will be emitted and can pose a fire and/or explosion risk. The leaked refrigerant 70 will be drawn through the interior openings 58 and will contact the refrigerant retention material 66, where the refrigerant 70 will be retained as immobilized refrigerant 72.

There is shown in FIGS. 3-6 an embodiment 100 which includes a housing 110 having side walls 116 and 112, top 114, bottom 118, and rear wall 130. An interior shell or cabinet 120 forms an interior space and has side walls 122 and 126 and top wall 124 and bottom wall 128. Interior vent openings 132 in the side walls 122 and 126 allow for the passage of air and leaked refrigerant gas. Within the interior shell 120 are refrigeration components such as compressor 140 and condenser 148. The compressor 140 pass refrigerant to the condenser 148 through the refrigerant conduit 142. The condenser 148 can pass refrigerant to an evaporator (not shown) through a refrigerant conduit 150, and the compressor 140 can receive refrigerant from the evaporator through a refrigerant conduit 154. A refrigerant retention device such as cartridge 160 can be positioned between the wall 122 and the exterior wall 112, and a refrigerant retention device such as cartridge 164 can be provided between interior wall 126 and exterior wall 116. Each refrigerant retention device is provided with refrigerant retention material 166. A flow space 168 is provided between the cartridges 160, 164 and the outer walls 112, 116,

A vent outlet opening 170 can be provided in the top 114 of the housing 110. The vent outlet opening 170 can communicate with a vent conduit 172. A gas pump such as fan 174 can be provided in or can communicate with the vent conduit 172 and vent outlet opening 170. A gas sensor 176 can be provided within the interior of the housing 110 and the interior shell 120 so as to detect the escape of refrigerant gas. The gas sensor 176 can communicate with the gas pump 174 by a direct communication line 178 or can communicate with the gas pump 174 through a processor 190 which can send wired or wireless signals 192.

As shown in FIG. 4, refrigerant gas 180 can sometimes leak such as from the compressor 140 or other refrigeration cycle components. The leaked refrigerant gas 180 contacts the sensor 176 which then causes a signal to be sent through communication line 178 or processor 190 to the gas pump 174. As shown in FIG. 5, the leaked refrigerant gas 180 will be drawn by the suction created by the gas pump 174 towards the openings 132 and through the refrigerant retention material 166 as indicated by arrows 182. The refrigerant gas will further be drawn as shown by arrows 184 in FIGS. 5-6 to the vent outlet opening 170 and vent conduit 172 by the action of the fan 174. The air and any remaining refrigerant gas below the critical combustion concentration will flow to the vent outlet opening 170 as shown by arrows 185 and 186. Refrigerant gas 180 will be retained on the refrigerant retention device 160 as immobilized refrigerant gas particles 183. Gas that is free of refrigerant or contains refrigerant below the flame point or explosion point of the particular refrigerant will safely escape the vent conduit 172 as shown by arrows 188.

There is shown in FIG. 7 an example of a refrigerant retention material 200. The refrigerant retention material 200 includes a main body 204 into which a plurality of pores 210 are formed defining pore openings 214. Gas including air molecules 216 and leaked refrigerant molecules 220 flow into the pores 210. The refrigerant molecules 220 are adhered to the refrigerant retention material 200 at the walls of the pores 210. Air molecules 216 are not retained by the refrigerant retention material and therefore flow through pore openings 214. Gas leaving the refrigerant retention material 200 has a greatly reduced concentration of volatile refrigerant gas molecules 220 that is below the flame point for the particular refrigerant.

FIG. 8 shows an alternative HVACR system 300 that includes an HVACR enclosure 310 for containing components of the refrigeration cycle such as compressor, condenser, and/or evaporator, and related refrigerant conduit. The HVACR enclosure 310 includes side walls 314, 318 and top 322. The HVACR system 300 includes a vent stack 330 which communicates with a vent outlet (not shown) formed in the top 322 and at the base 332 of the vent stack 330. The vent stack 330 can be modular with a number of components connected to form the vent stack 330. One such component is a refrigerant retention module 340 comprising a tubular housing 341 with an open interior 346. A refrigerant retention device 342 is mounted in a sleeve holder 344 by which the refrigerant retention device can be moved in and out of the module 340 and in and out of the gas flow path in the open interior 346 of the tubular housing 341. An electronic damper module 350 can include a switch 352 and a motor to close the damper 354 when desired, particularly whenever the system is not operating so as to prevent the intrusion of dust, moisture and insects. A vacuum operated damper module 360 has a damper 362 which pivots to an open position upon exposure to the vacuum created by the operation of a gas pump. A gas pump module 370 includes suitable structure such as a fan 374 provided in an open interior 372 of the gas pump module 370. A top damper module 380 has a hinged lid 382 which is pivotable and opened by the gas pressure created by the fan 374. The top damper helps to prevent the intrusion of dust, moisture and insects when the gas pump module 370 is not in use.

FIG. 9 is a schematic depiction of a building 400 such as a residential or commercial building having walls 402, ceiling 404, and roof 406 defining attic space 408. A typical air conditioning unit includes a condenser unit 410 outside and on the ground level, while an air handler 420 is provided in the attic space 408. The air handler 420 has an outlet 422 which connects to a distribution conduit 424 leading to air outlets 430-432 as shown by arrows 440-442. Air is returned to the air handler 420 through one or more returns 446 as shown by arrow 448. A refrigerant retention device 450 can be positioned at the outlet 422 or within the air distribution conduit 424 such that refrigerant retention material in the refrigerant retention device 450 will capture and retain leaked, where a build-up of such gases would otherwise create an explosive or toxic condition refrigerant and prevent such from reaching the interior spaces of the building.

There is shown in FIG. 10 a cold storage unit such as walk-in cooler 500. The walk-in cooler 500 can have side walls 502, 506, bottom floor 504, top 508 and rear wall 510. A doorway 514 and door 516 can be provided to allow access to the interior 518. HVACR equipment such as compressor 520 and condenser 530 can be provided within the interior space 510. A vent outlet 540 is provided and connects to a vent outlet conduit 544 within which is a refrigerant retention device 542. A gas pump such as fan 546 can be provided in the interior 548 of the vent conduit 544. A sensor 562 can be provided in the interior space 518 such as on top 508. The sensor 562 communicates with a processor 560 through a communication line 564. The processor 560 sends a signal to gas pump 546 through communication line 566 to operate the gas pump 546. The processor 560 can also communicate with the compressor 520 through communication line 570, and with the condenser 530 through communication line 568.

The invention can be flexibly integrated in a wide range of HVACR equipment used in both residential and commercial buildings. The disclosed technologies enable utilization of natural refrigerants with ultralow GWP values in heating and cooling equipment to reduce or eliminate fire and explosion risk.

The disclosed technologies can be used in fields such as energy and utilities or detectors and sensors. More specifically, the disclosed technologies can be used in the commercial/residential/industrial refrigeration and air-conditioning industry.

The invention as shown in the drawings and described in detail herein disclose arrangements of elements of particular construction and configuration for illustrating preferred embodiments of structure and method of operation of the present invention. It is to be understood however, that elements of different construction and configuration and other arrangements thereof, other than those illustrated and described may be employed in accordance with the spirit of the invention, and such changes, alternations and modifications as would occur to those skilled in the art are considered to be within the scope of this invention as broadly defined in the appended claims. In addition, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.