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

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.

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.

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

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.

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

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 inan HVACR systemwhich includes a compressor, a condenser, and an evaporator(shown in phantom). The refrigeration cycle and components can be selected from known components. As is known, refrigerant can be conveyed from the compressorto the condenserby a suitable refrigerant conduit. Refrigerant can be conveyed from the condenserto the evaporatorby a refrigerant conduit. Refrigerant can be conveyed from the evaporator to the compressorby a refrigerant conduit. Other connections or additional connections are possible.

All or some of the refrigeration cycle components such as the condenserand compressorcan be contained within an HCACR enclosurewhich can have side wallsand, top, bottom, rear, and can have an access panel or door. Many different designs, sizes and variations of the HVACR enclosureare possible. The HVACR enclosurecan 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 enclosurecan have a number of vent outlet openingsto the surroundings for purposes of cooling the compressorand/or the condenser.

Interior walls,can be provided and can have interior openingsto permit the passage of leaked refrigerant gas can be connected to topand bottomto form an interior shell within the HVACR enclosurein which the compressorand condenserare contained. Refrigerant retention devices such as cartridgesandcontaining a refrigerant retention materialare positioned between the interior walland exterior wall, in between the interior walland exterior wall.

As shown in, whenever a leak exists in some part of the refrigeration system components such as for example the compressoras shown, refrigerantwill be emitted and can pose a fire and/or explosion risk. The leaked refrigerantwill be drawn through the interior openingsand will contact the refrigerant retention material, where the refrigerantwill be retained as immobilized refrigerant.

There is shown inan embodimentwhich includes a housinghaving side wallsand, top, bottom, and rear wall. An interior shell or cabinetforms an interior space and has side wallsandand top walland bottom wall. Interior vent openingsin the side wallsandallow for the passage of air and leaked refrigerant gas. Within the interior shellare refrigeration components such as compressorand condenser. The compressorpass refrigerant to the condenserthrough the refrigerant conduit. The condensercan pass refrigerant to an evaporator (not shown) through a refrigerant conduit, and the compressorcan receive refrigerant from the evaporator through a refrigerant conduit. A refrigerant retention device such as cartridgecan be positioned between the walland the exterior wall, and a refrigerant retention device such as cartridgecan be provided between interior walland exterior wall. Each refrigerant retention device is provided with refrigerant retention material. A flow spaceis provided between the cartridges,and the outer walls,,

A vent outlet openingcan be provided in the topof the housing. The vent outlet openingcan communicate with a vent conduit. A gas pump such as fancan be provided in or can communicate with the vent conduitand vent outlet opening. A gas sensorcan be provided within the interior of the housingand the interior shellso as to detect the escape of refrigerant gas. The gas sensorcan communicate with the gas pumpby a direct communication lineor can communicate with the gas pumpthrough a processorwhich can send wired or wireless signals.

As shown in, refrigerant gascan sometimes leak such as from the compressoror other refrigeration cycle components. The leaked refrigerant gascontacts the sensorwhich then causes a signal to be sent through communication lineor processorto the gas pump. As shown in, the leaked refrigerant gaswill be drawn by the suction created by the gas pumptowards the openingsand through the refrigerant retention materialas indicated by arrows. The refrigerant gas will further be drawn as shown by arrowsinto the vent outlet openingand vent conduitby the action of the fan. The air and any remaining refrigerant gas below the critical combustion concentration will flow to the vent outlet openingas shown by arrowsand. Refrigerant gaswill be retained on the refrigerant retention deviceas immobilized refrigerant gas particles. 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 conduitas shown by arrows.

There is shown inan example of a refrigerant retention material. The refrigerant retention materialincludes a main bodyinto which a plurality of poresare formed defining pore openings. Gas including air moleculesand leaked refrigerant moleculesflow into the pores. The refrigerant moleculesare adhered to the refrigerant retention materialat the walls of the pores. Air moleculesare not retained by the refrigerant retention material and therefore flow through pore openings. Gas leaving the refrigerant retention materialhas a greatly reduced concentration of volatile refrigerant gas moleculesthat is below the flame point for the particular refrigerant.

shows an alternative HVACR systemthat includes an HVACR enclosurefor containing components of the refrigeration cycle such as compressor, condenser, and/or evaporator, and related refrigerant conduit. The HVACR enclosureincludes side walls,and top. The HVACR systemincludes a vent stackwhich communicates with a vent outlet (not shown) formed in the topand at the baseof the vent stack. The vent stackcan be modular with a number of components connected to form the vent stack. One such component is a refrigerant retention modulecomprising a tubular housingwith an open interior. A refrigerant retention deviceis mounted in a sleeve holderby which the refrigerant retention device can be moved in and out of the moduleand in and out of the gas flow path in the open interiorof the tubular housing. An electronic damper modulecan include a switchand a motor to close the damperwhen desired, particularly whenever the system is not operating so as to prevent the intrusion of dust, moisture and insects. A vacuum operated damper modulehas a damperwhich pivots to an open position upon exposure to the vacuum created by the operation of a gas pump. A gas pump moduleincludes suitable structure such as a fanprovided in an open interiorof the gas pump module. A top damper modulehas a hinged lidwhich is pivotable and opened by the gas pressure created by the fan. The top damper helps to prevent the intrusion of dust, moisture and insects when the gas pump moduleis not in use.

is a schematic depiction of a buildingsuch as a residential or commercial building having walls, ceiling, and roofdefining attic space. A typical air conditioning unit includes a condenser unitoutside and on the ground level, while an air handleris provided in the attic space. The air handlerhas an outletwhich connects to a distribution conduitleading to air outlets-as shown by arrows-. Air is returned to the air handlerthrough one or more returnsas shown by arrow. A refrigerant retention devicecan be positioned at the outletor within the air distribution conduitsuch that refrigerant retention material in the refrigerant retention devicewill 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 ina cold storage unit such as walk-in cooler. The walk-in coolercan have side walls,, bottom floor, topand rear wall. A doorwayand doorcan be provided to allow access to the interior. HVACR equipment such as compressorand condensercan be provided within the interior space. A vent outletis provided and connects to a vent outlet conduitwithin which is a refrigerant retention device. A gas pump such as fancan be provided in the interiorof the vent conduit. A sensorcan be provided in the interior spacesuch as on top. The sensorcommunicates with a processorthrough a communication line. The processorsends a signal to gas pumpthrough communication lineto operate the gas pump. The processorcan also communicate with the compressorthrough communication line, and with the condenserthrough communication line.

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.