SYSTEMS AND METHODS FOR MITIGATING LEAKING FLAMMABLE REFRIGERANTS

A leakage protection system for a heating, ventilation, and air condition (HVAC) system can comprise: a power source; a louvered assembly including a frame, slats spaced apart vertically within the frame and extending from a first side to a second side of the frame, an actuator rod operably coupled to the slats, and a spring; a solenoid operably coupled to the actuator rod; and a first pressure switch disposed electrically between the power source and the solenoid.

FIELD

The present disclosure relates to heating, ventilation, and air condition (“HVAC”) systems, and more specifically to systems and methods for mitigating leaking flammable refrigerants in HVAC systems.

BACKGROUND

With increased fluorinated gas restrictions for using current refrigerants with high global warming potential (“GWP”) on aircraft, there is very significant interest in using alternative, low GWP refrigerants such as hydrofluoroolefin (“UFOs”) onboard aircraft HVAC systems such as air chillers or small refrigerators. However, low GWP refrigerants can be flammable, which could be potentially harmful if a leak were to occur during operation.

SUMMARY

A leakage protection system for a heating, ventilation, and air condition (HVAC) system is disclosed herein. In various embodiments, the leakage protection system comprises: a power source; a louvered assembly including a frame, slats spaced apart vertically within the frame and extending from a first side to a second side of the frame, an actuator rod operably coupled to the slats, and a spring; a solenoid operably coupled to the actuator rod; and a first pressure switch disposed electrically between the power source and the solenoid.

In various embodiments, the first pressure switch is configured to open in response to an operating pressure in a fluid conduit of the HVAC system falling below a pressure threshold. The solenoid can be de-energized in response to the first pressure switch opening. The louvered assembly can be configured to transition from an open configuration to a closed configuration in response to the solenoid being de-energized. The spring can transition the louvered assembly from the open configuration to the closed configuration in response to the solenoid being de-energized. The actuator rod can be configured to bias the slats into the open configuration during operation of the HVAC system, and wherein the spring is compressed in response to the actuator rod biasing the slats into the open configuration.

In various embodiments, the leakage protection system further comprising a second pressure switch disposed electrically between the first pressure switch and the power source of the solenoid. The first pressure switch can be configured to open in response to an operating pressure falling below a first pressure threshold, and the second pressure switch can be configured to open in response to the operating pressure exceeding a second pressure threshold. The solenoid can be de-energized in response to the first pressure switch opening or the second pressure switch opening.

A heating, ventilation, and air condition (HVAC) system is disclosed herein. The HVAC system can comprise: a housing defining an inlet port; a power source; a plumbing system disposed in the housing, the plumbing system including a fluid conduit configured to flow a refrigerant therethrough during operation, the plumbing system including a condenser disposed proximate the inlet port; a first pressure switch operably coupled to the plumbing system; a first louvered assembly disposed proximate the inlet port; and a first solenoid operably coupled to the first louvered assembly, the first pressure switch disposed electrically between the power source and the first solenoid.

In various embodiments, the HVAC system further comprises a second louvered assembly, wherein the housing further defines an outlet port, and wherein the second louvered assembly is disposed proximate the outlet port. The HVAC system can further comprise a second solenoid operably coupled to the second louvered assembly, wherein the first pressure switch is disposed electrically between the second solenoid and the power source. The first louvered assembly and the second louvered assembly can both be configured to transition from an open configuration to a closed configuration in response to the first pressure switch opening. The first solenoid and the second solenoid can be de-energized in response to the first pressure switch opening. The first pressure switch can be configured to open in response to an operating pressure exceeding a pressure threshold.

The HVAC system can further comprise a second pressure switch disposed electrically between the first pressure switch and the first solenoid and between the first pressure switch and the second solenoid. The first pressure switch can be configured to open in response to an operating pressure falling below a first pressure threshold, and the second pressure switch can be configured to open in response to the operating pressure exceeding a second pressure threshold.

In various embodiments, the HVAC system further comprises a compressor coupled to the fluid conduit, the condenser disposed upstream of the compressor, a heat exchanger disposed downstream of the compressor, and an expansion device disposed fluidly between the condenser and the heat exchanger, wherein a pressure relief device is coupled to the compressor.

A method of operating a leakage protection system is disclosed herein. In various embodiments, the method comprises: biasing, via the leakage protection system, a louvered assembly into an open configuration in response to an operating pressure of a fluid conduit in a heating, ventilation, and air condition (HVAC) system being between a first pressure threshold and a second pressure threshold; closing, via the leakage protection system, the louvered assembly in response to the operating pressure of the fluid conduit falling below the first pressure threshold; and closing, via the leakage protection system, the louvered assembly in response to the operating pressure of the fluid conduit exceeding the second pressure threshold.

In various embodiments, closing the louvered assembly further comprises: de-energizing a solenoid operably coupled to an actuator rod of the louvered assembly; and closing the louvered assembly via a spring in response to the solenoid being de-energized.

DETAILED DESCRIPTION

Disclosed herein are systems and methods for containing (and/or mitigating) accidental leaks of refrigerants (e.g., flammable refrigerants, such as HFOs) in HVAC systems. In various embodiments, the HVAC system can be for an aircraft. However, the present disclosure is not limited in this regard.

In various embodiments, the system comprises a louvered containment device and a charge isolation valve and/or an emergency pressure relief venting. In various embodiments, the system is configured to prevent refrigerant leakage forming potentially flammable concentrations outside the system when not in operation. In various embodiments, a blow off valve and a shutter system (or systems) at the condenser heat exchanger and/or exhaust ports could be closed. In this regard, refrigerant can be contained in case of a potential failure. During regular operation, installed blowers can readily dilute any potential leaks below flammability limits, in accordance with various embodiments.

In various embodiments, the system disclosed herein can be retrofitted into typical HVAC systems. In this regard, a refrigerant that is flammable can replace typical refrigerants, and the system disclosed herein can easily be retrofitted onto the current system providing leak mitigation protection, in accordance with various embodiments. In various embodiments, the system disclosed herein is passive (i.e., no sensors or electrical control components have to instruct the system to active). In various embodiments, the system disclosed herein does not utilize components that have to be replaced, maintained, and/or are life limited components. In various embodiments, the system disclosed herein does not utilize an auxiliary power source. In various embodiments, the system disclosed herein relies on leakage protection and dilution to below flammable limits in air using existing blowers during start-up/normal operation. The system disclosed herein provides leakage mitigation in response to the system being powered down (or not being in operation).

Referring now toFIG.1, an aircraft10having an HVAC system100disposed therein is illustrated in accordance with various embodiments. The aircraft comprises a fuselage20, wings22,24, each wing22,24extending from a root12,14disposed at the fuselage to a tip32,34disposed distal to the fuselage. In various embodiments, the HVAC system100is disposed at least partially within the fuselage20. In this regard, the HVAC system100is configured to provide cooling air into a cabin of the fuselage20during operation of the aircraft10as described further herein. Although described as being in an aircraft10, the HVAC system100is not limited in this regard. For example, the HVAC system100can be disposed in a building, a house, a commercial residence, a private residence, or the like and still be within the scope of this disclosure.

Referring now toFIG.2, a schematic view of the HVAC system100is illustrated, in accordance with various embodiments. The HVAC system100comprises a housing110, a plumbing system120, a leakage protection system130, and fans142,144. In various embodiments, the plumbing system120is disposed within the housing110. The housing110defines inlet ports112,114and outlet ports116,118. The plumbing system120comprises an expansion device122, fluid conduits124, a compressor126, a condenser127and a heat exchanger128. In various embodiments, the condenser127is disposed proximate the inlet port112and the heat exchanger128is disposed proximate the inlet port114. The fan142is disposed within the outlet port116and the fan144is disposed within the outlet port118.

In various embodiments, during operation of the HVAC system100, air flows through the inlet port112(i.e., pulled in via the fan142). In response to flowing through the inlet port112, the refrigerant flows through the condenser127, which adds heat to the airflow and thus heating the airflow. The heated airflow is then released out the outlet port116back to a cabin in the fuselage20of the aircraft10fromFIG.1. Similarly, chilled air from a galley of the aircraft10fromFIG.1can be pulled through the inlet port114into a cavity115via the fan144, and then released back into the galley through outlet port118. In this regard, the air traveling through the inlet port114is cooled in a reverse manner to the airflow travelling through the inlet port112.

In various embodiments, during operation, a refrigerant travels through plumbing system120. In this regard, the refrigerant travels through the expansion device122. The expansion device122controls an amount of refrigerant and rapidly reduces the refrigerant pressure and temperature released to an evaporator section of the plumbing system120, in accordance with various embodiments. After going through the expansion device122, the refrigerant travels through the heat exchanger128which transitions the refrigerant from a liquid state to a gas state in response to heat being absorbed from the chilled air coming from the galley of the aircraft10fromFIG.1. After traveling through the heat exchanger128, the refrigerant, in the gas state, travels through the compressor126then upstream to the condenser127. The compressor performs work on the refrigerant raising its pressure and temperature. Then the refrigerant travels through the condenser127where heat is removed from the refrigerant to condense it, and heat is transferred to the air entering the inlet port112by the refrigerant, which transitions back from the gas state into the liquid state.

In various embodiments, the refrigerant disposed in the plumbing system120comprises a low GWP refrigerant, such as hydrofluoroolefin (“HFOs”). In this regard, the refrigerant can be flammable. Accordingly, the leakage protection system130is configured to impede refrigerant leakage from the HVAC system100, significantly reducing the refrigerant leakage rate to prevent or reduce leakage of the refrigerant from the housing110of the HVAC system while the HVAC system100is not in operation, or in response to the HVAC system100malfunctioning, as described further herein.

In various embodiments, the leakage protection system130comprises a high-pressure switch132, a low-pressure switch134, and a louvered assembly136. In various embodiments, the louvered assembly136is coupled to the housing110. With brief reference toFIGS.4A and4B, the louvered assembly136in an “open configuration” is illustrated, in accordance with various embodiments. In an open configuration, the slats402of the louvered assembly136are angled in a manner to fluidly couple an internal cavity113of the housing110to an external environment (e.g., a fluid conduit in fluid communication with the inlet port112). In this regard, in the open configuration, the air from the aircraft can flow through the inlet port112into the cavity113and out the outlet port116as described previously herein. In various embodiments, as described further herein, the louvered assembly136is configured to be in an open state (i.e., the open configuration), during operation of the HVAC system100. In this regard, the HVAC system100can operate normally.

In various embodiments, the high-pressure switch132and the low-pressure switch134are operably coupled to the fluid conduit124of the plumbing system. In various embodiments, the pressure switches132,134are configured to be in a closed position during normal operation, as described further herein.

Referring now toFIG.3, a schematic view of the leakage protection system130is illustrated, in accordance with various embodiments. In various embodiments, the leakage protection system130further comprises a power source131and a solenoid135. In various embodiments, during typical operation of the HVAC system100fromFIG.2, the high-pressure switch132and the low-pressure switch134are in a closed position. In this regard, during typical operation of the HVAC system100, the solenoid is electrically coupled to the power source131. In response to the solenoid135being energized (i.e., in response to receiving a current from the power source131), the solenoid actuates an actuator rod (e.g., actuator rod406fromFIG.4B), which compresses a spring (e.g., spring404fromFIG.4B). In response to the actuator rod406translating linearly, the slats402of the louvered assembly136(as shown inFIG.4A) transition from a closed configuration into the open configuration.

In various embodiments, in response to the power source131being electrically de-coupled from the solenoid135, the solenoid135becomes de-energized, and the spring404fromFIG.4Breturns the slats402of the louvered assembly136to a closed configuration. A “closed configuration” as referred to herein is a configuration where each slat in the slats402of the louvered assembly136fromFIG.4Aoverlaps an adjacent slat in the slats402of the louvered assembly136. In this regard, with reference back toFIG.2, the cavity113within the housing110becomes fluidly obstructed from the fluid conduit providing the air through the inlet112. In this regard, if refrigerant is leaking within the cavity113within the housing110, the refrigerant vapor flow rate is impeded reducing the amount of refrigerant which can escape through the inlet port112and housing110, in accordance with various embodiments.

With continued reference toFIG.2, in accordance with various embodiments, the leakage protection system130can further comprise a second louvered assembly156disposed proximate the outlet port116. In this regard, the second louvered assembly156can be configured to fluidly impede or isolate an external environment proximate the outlet port116from the internal cavity113in a similar manner to the louvered assembly136, in accordance with various embodiments. In various embodiments, although illustrated as being at a lower side of the HVAC system100, the outlet port116can be aligned in an upward direction. In this regard, leakage from the outlet port116can potentially be prevented without a second louvered assembly156via gravity as opposed to a second louvered assembly156, in accordance with various embodiments. The present disclosure is not limited in this regard.

In various embodiments, the louvered assembly156is in accordance with the louvered assembly136. In various embodiments, the louvered assembly156is coupled to the housing110. In various embodiments, the louvered assembly156is operably coupled to the power source131, the high-pressure switch132, the low-pressure switch134, and a solenoid155as shown inFIG.3. In this regard, in a dual louvered assembly embodiment, both louvered assemblies136,156can be operably coupled to the power source131, the high-pressure switch132, and the low-pressure switch134, in accordance with various embodiments.

In various embodiments, the leakage protection system130further comprises a pressure relief device138coupled to the compressor126. In various embodiments, the pressure relief device138is configured to release pressure from the plumbing system120in response to a pressure exceeding a pressure threshold in the plumbing system120. For example, in response to the pressure in the fluid conduits124exceeding 350 pounds per square inch (psi), the pressure relief device138can begin to release the pressure from the plumbing system120. In various embodiments, the pressure relief device138comprises a burst disk. A “burst disk” as disclosed herein is a disk that covers a fluid outlet and is configured to burst in response to a pressure experienced by the burst disk exceeding a pressure threshold.

In various embodiments, the leakage protection system130comprises at least one of the pressure relief device138, the louvered assembly136, and the louvered assembly156. In this regard, the pressure relief device138, the louvered assembly136, and the louvered assembly156each comprise various benefits for reducing pressure and preventing leakage or reducing leakage rate to remain below flammable air mixture limits of a refrigerant due to a malfunction or after shutting down of the HVAC system100.

Referring now toFIGS.4A and4B, a perspective view of a louvered assembly136,156in an open position (FIG.4A) and a detail view of a portion of the louvered assembly136,156(FIG.4B) are illustrated, in accordance with various embodiments. In various embodiments, the louvered assembly136,156comprises a frame408at least partially defining a perimeter of the louvered assembly136,156. In various embodiments, the frame408can be coupled to a housing (e.g., housing110) of an HVAC system100by any method known in the art (e.g., fasteners or the like). In various embodiments, slats402are spaced apart in a vertical direction, though not limited to any other orientation, within the frame408and operably coupled to the actuator rod406. In various embodiments, the actuator rod406can be configured to twist or translate. The present disclosure is not limited in this regard. In various embodiments, the actuator rod is configured to transition the slats402from an open position (i.e., where adjacent slats in the slats402have an opening therebetween) to a closed position (i.e., where adjacent slats in the slats402abut each other fluidly de-coupling a first side of the louvered assembly136,156from a second side of the louvered assembly136,156.

In various embodiments, the solenoid135,155is operably coupled to the actuator rod406and coupled to the frame408. The solenoid135,155is configured to be electrically coupled to the pressure switches132,134and the power source131described previously herein during normal operation. In this regard, the solenoid135,155is configured to bias the actuator rod406in a manner that causes the spring404to compress, and the slats402into an open configuration as described previously herein. In response to being de-energized (e.g., in response to a pressure switch132,134transitioning from a closed position to an open position), the actuator rod406is returned to a default position (i.e., where the slats402are closed), in accordance with various embodiments.

Referring now toFIG.5, a method of operating a leakage protection system130for an HVAC system100is illustrated, in accordance with various embodiments. The method500comprises operating an HVAC system100(step502). In response to operating the HVAC system100fromFIG.2, a refrigerant travels through the fluid conduits124of the plumbing system120, supplying an operating pressure within the fluid conduits124. In various embodiments, the method500further comprises biasing, via a leakage protection system, a louvered assembly136,156into an open configuration in response to the operating pressure being within a predetermined range (e.g., between a first pressure threshold and a second pressure threshold) (step504). In various embodiments, the first pressure threshold is meant to trip the leakage activation system in response to refrigerant leaking out of fluid conduits124which reduces the refrigerant pressure sensed within fluid conduit124as an abnormal condition. Refrigerant pressure will always be above the first pressure threshold independent of HVAC system100operating state being ON or OFF under normal conditions. In various embodiments, the second pressure threshold is meant to identify a malfunctioning condition where the pressure in the fluid conduits124exceeds the second pressure threshold. In various embodiments, the first pressure threshold can be approximate 15 pounds per square inch (psig). In various embodiments, the second pressure threshold can be approximately 350 psig. However, the present disclosure is not limited in this regard.

The method500further comprises closing, via the leakage protection system130, an outlet port of the HVAC system100via a louvered assembly in response to a refrigerant operating pressure falling below the first pressure threshold (step506). In various embodiments, the louvered assembly136,156is closed in response to a solenoid coupled to the louvered assembly136,156being de-energized as described previously herein.

The method500further comprises closing, via the leakage protection system, the outlet port of the HVAC system100via the louvered assembly in response to the pressure exceeding the second pressure threshold (step508). In this regard, in response to an operating pressure becoming too high and potentially creating a scenario where the fluid conduits124of the plumbing system120could break, leakage of the refrigerant outside of the housing110of the HVAC system100can be prevented, in accordance with various embodiments. In various embodiments, in response to a high-pressure situation, a pressure relief device of the compressor in the HVAC system100can be activated (e.g., a burst duct could burst) providing relief of pressure in the fluid conduits124, in accordance with various embodiments.

Finally, it should be understood that any of the above-described concepts can be used alone or in combination with any or all of the other above-described concepts. Although various embodiments have been disclosed and described, one of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. Accordingly, the description is not intended to be exhaustive or to limit the principles described or illustrated herein to any precise form. Many modifications and variations are possible in light of the above teaching.