Patent Description:
As worldwide environmental regulations or global warming gases evolve, new restrictions aim to reduce the amount of charge contained in refrigerant systems and to force substitution of mildly flammable and flammable refrigerants over traditional refrigerants for their greener properties (e.g., lower global warming potential (GWP)). With the entry of mildly flammable and flammable refrigerants into the consumer air conditioning and refrigeration markets there can be concern over the safety of these devices. Consequently, regulations aim to mandate safety measures to ensure product safety, such as inclusion of sensors capable to warning users in the event or a refrigerant leakage. Accordingly, there remains a need in the art to develop robust, low cost methods of leak detection for these systems to ensure product safety.

<CIT> discloses a refrigeration cycle device.

<CIT> discloses an air-conditioning apparatus.

The present invention provides a method as claimed in claim <NUM>.

Optionally, the method further comprises locating the gas sensing core and the condition sensor at or below a substantial portion of a heat exchanger of an HVAC/R device.

Optionally, the recording the parameter output minimum value further comprises recording the parameter output minimum value from the condition sensor over a timespan of <NUM> minutes.

Optionally, the gas sensing core comprises a combustibility sensor, and wherein the target gas measurement threshold value is equal to <NUM> % of the lower flammability limit of R-454B.

Optionally, the gas sensing core comprises a R-454B gas sensor, and wherein the target gas measurement threshold value is equal to <NUM> volume % R-454B.

Optionally, the condition sensor comprises a humidity sensor, and wherein the parameter difference threshold value is <NUM>% relative humidity.

Optionally, the condition sensor comprises a temperature sensor, and wherein the rate threshold value is <NUM>/minute.

The present invention provides a heating, ventilation, air conditioning, or refrigeration (HVAC/R) system as claimed in claim <NUM>.

<FIG> is a schematic illustration of a front view of a vertically arranged heating, ventilation, air conditioning, or refrigeration (HVAC/R) device <NUM> having an indoor heat exchanger section <NUM>, a fan section <NUM>, a gas sensing module <NUM>, and a control unit <NUM>. The vertically arranged HVAC/R device <NUM> can be configured as an indoor unit for a residential HVAC system (e.g., air conditioner, heat pump, and the like). Although depicted vertically in <FIG>, a horizontally arranged HVAC/R device <NUM>, such as for installation in an attic space, are within the scope of this disclosure.

<FIG> is a schematic illustration of a top view of a horizontally arranged HVAC/R device <NUM> having an indoor heat exchanger section <NUM>, an outdoor heat exchanger section <NUM>, a fan section <NUM>, a gas sensing module <NUM>, and a control unit <NUM>. A divider can separate the indoor and the outdoor heat exchanger sections. The horizontally arranged HVAC/R device can be configured as a commercial HVAC device (e.g., such as a rooftop air conditioner, heat pump, and the like).

<FIG> is a schematic illustration of a side view of a HVAC/R device <NUM> having an indoor heat exchanger section <NUM> (e.g., evaporator section), a fan section <NUM>, a gas sensing module <NUM>, a control unit <NUM>, and product shelves <NUM>. The HVAC/R device <NUM> can be configured as a refrigerated display case (e.g., for refrigerating self-service retail products). The order of the indoor heat exchanger section <NUM> and the fan section <NUM> along an air flow pathway <NUM> can be reversed.

The indoor heat exchanger section <NUM> can include a heat exchanger of any suitable heat exchanger technology, configuration, orientation, or design. For example, the indoor heat exchanger section <NUM> can include a finned tube heat exchanger (e.g., round tube plate fin (RTPF), spike fin, and the like), or a flat tube heat exchanger (e.g., microchannel heat exchanger), or the like. A heat exchanger of the indoor heat exchanger section <NUM> can be configured in any suitable shape and orientation, such as a flat configuration, a flat inclined configuration, a folded and/or bent configuration (e.g., such as having a C, J, L, M, N, U, V, W, or Z shaped configuration, or the like), or the like. The heat exchanger of the indoor heat exchanger section <NUM> can be configured for single-pass or multi-pass configuration (e.g., where refrigerant contained within the heat exchanger crosses through, and is in thermal communication with, an air stream external the heat exchanger more than one time per loop through a vapor compression cycle).

The fan section <NUM> can include any suitable fan technology, including axial flow, centrifugal flow, and mixed flow fans, to move air through the HVAC/R device <NUM>. The fan section <NUM> can further include flow guides, louvers, and the like for directing flow into, through, and/or from the fan section <NUM>. Although the fan section <NUM> can be located downstream of the indoor heat exchanger section <NUM> as in <FIG>, as noted above the opposite configuration where the indoor heat exchanger section <NUM> is located above the fan section <NUM> can also be used.

<FIG> is a schematic illustration of a side view of a building <NUM> having levels <NUM>, <NUM>, walls <NUM>, floors <NUM>, and ceilings <NUM>. The building <NUM> can include one or more hazard detection devices <NUM>. For example, the hazard detection device <NUM> can include a sensor of a gas phase hazard such as a smoke detector, a carbon monoxide (CO) detector, a flammable gas detector, radon detector, oxygen sensor, carbon dioxide (CO<NUM>) monitor, pollutant gas detector (e.g., volatile organic compound (VOC) gas detector, particulate matter (PM) detector (e.g., PM <NUM>, PM <NUM>, or PM <NUM> corresponding to detectors capable of detecting particles having average particle diameters of less than or equal to about <NUM> micrometers (µm), <NUM>, and <NUM> respectively), formaldehyde (CH<NUM>O) detector, lead (Pb) detector, pesticide detector, nitrogen dioxide (NO<NUM>) detector, or the like), or the like. The hazard detection device <NUM> can include a gas sensing module <NUM>, such as described herein.

<FIG> is a schematic illustration of a side view of an oil rig <NUM> having levels <NUM>, <NUM>, <NUM>, walls <NUM>, floors <NUM>, and ceilings <NUM>. The oil rig <NUM> can include one or more hazard detection devices <NUM> for monitoring for the presence of hazards to workers on the oil rig <NUM>. For example, the hazard detection device <NUM> can include a sensor of a gas phase hazard such as a petroleum gases, hydrogen sulfide (H<NUM>S), engine exhaust (e.g., diesel exhaust), natural gas or constituents thereof, including other flammable or combustible gases (e.g., butane, butene, propane, propene, methane, ethane, ethene, or mixtures thereof). The hazard detection device <NUM> can include a gas sensing module <NUM>, such as described herein.

The gas sensing module <NUM> can include a gas sensing core <NUM> and a condition sensor <NUM> (e.g. an environmental condition sensor such as a temperature, humidity, pressure sensor, a combination including at least one of the foregoing, or the like). The gas sensing core <NUM> and/or the condition sensor <NUM> can be mounted on a circuit board <NUM>. For example, as in <FIG>, electrically conductive traces <NUM> of the circuit board <NUM> can act to electrically link the electrical outputs of the gas sensing core <NUM> and the condition sensor <NUM> to one or more output terminals <NUM> of the gas sensing module <NUM>. As used herein, output terminals can refer to any means of providing an electrically conductive interface to the electrical output signal of the referenced element, e.g., including terminal blocks, pins, blades, conductors, conductive traces, and the like. Optionally, the condition sensor <NUM> can be mounted in direct contact with a surface of the gas sensing core <NUM> or can be an internal sensor configured to sense a condition internal to the gas sensing core <NUM> (e.g., configure to measure internal core temperature, humidity, or the like). For example, the condition sensor <NUM> can be mounted on top of the gas sensor core <NUM>. In another example, the condition sensor <NUM> can be mounted on the circuit board <NUM> directly contacting a side of the gas sensing core <NUM>.

The gas sensing core <NUM> can include any suitable technology of gas phase monitoring. For example, the gas sensing core <NUM> can rely on nondispersive infrared (NDIR), ultrasonic, or electrochemical measurement technology. The methods disclosed herein can improve the accuracy of the gas sensing module <NUM> by dismissing erroneous alarms whose conditions mimic that of water condensation on the gas sensing core <NUM>.

The control unit <NUM> can include a controller <NUM>, such as a field programmable gate array (FPGA), central processing unit (CPU), application specific integrated circuits (ASIC), or the like. The control unit <NUM> can be disposed remote of the gas sensor <NUM>. Electrical conductors can extend between the controller <NUM> and the gas sensing module <NUM> for interfacing one or more output terminals of the gas sensing module <NUM> to one or more input terminals of the controller <NUM>. Alternatively, the controller <NUM> can include a wireless receiver and one or more outputs of the gas sensing module <NUM> can be wirelessly transmit to the controller <NUM> (e.g., via a wireless transmitter, such as a Bluetooth transmitter, low energy Bluetooth (BLE) transmitter, NFC transmitter, or the like) using a transmitter disposed in electrical communication with the gas sensing module <NUM>.

A problem with the systems, such as described above, is that they can erroneously indicate the presence of a target gas when condensation occurs on the gas sensing core <NUM>. Condensation on the gas sensing core <NUM> can be particularly pronounced in HVAC/R devices <NUM> due to the relatively cold surface temperatures of some of the components during operation (e.g., evaporator and connected piping and equipment). A method of overcoming condensation induced false positive indications from the gas sensing core <NUM> can include providing a heater for heating areas of the gas sensor module <NUM> susceptible to condensation (e.g., the gas sensing core <NUM> and adjacent areas). However, such methods can be electrically inefficient, place additional limitation on system design, e.g. power storage, distribution, and control associated with one or more heaters, and/or raise other concerns, e.g., such as safety concerns associated with co-locating an electric heater with a sensor used to detect combustible gases. Accordingly, the disclosed method can dismiss false positive indications from the gas sensing core <NUM> in a safe and robust way by analyzing changes in the output signals of gas sensing core <NUM> and condition sensor <NUM> over time.

<FIG> is a schematic illustration of a method <NUM> of sensing the presence of a target gas in a gas volume. A first step <NUM> of method <NUM> can include providing a gas sensor module <NUM>, having a gas sensing core <NUM> configured for sensing a target gas and a condition sensor <NUM>, within the gas volume. The gas volume can be a volume within a housing of the HVAC/R device <NUM>, e.g., a volume adjacent and/or encompassing refrigerant bearing components of the HVAC/R device <NUM>. For example, the gas volume can include at least a portion of the indoor heat exchanger section <NUM>. The gas volume can encompass an evaporator of the HVAC/R device <NUM>. The gas volume can extend under an evaporator along a floor of the HVAC/R device <NUM>. Locating the gas sensor module <NUM> near to the floor of the HVAC/R device <NUM> can speed detection of the refrigerant gases because the refrigerant can be denser than air and can tend to drop towards and accumulate near the floor first during a leakage scenario. The gas volume can be disposed within a room <NUM>, <NUM> or other area of a building <NUM>, oil rig <NUM>, or other site where occupants or proximate workers may be exposed to hazardous gases (e.g., radon, hydrogen sulfide, and the like).

A second step <NUM> of method <NUM> can include providing the controller <NUM> configured in electrical communication with the gas sensing core <NUM> and the condition sensor <NUM>. The controller <NUM> can read the parameter output from the condition sensor <NUM> and target gas measurement output from the gas sensing core <NUM> to decide whether an indication of positive gas detection by the gas sensing core <NUM> is representative of actual gas detection, or of a false positive. For example, the controller <NUM> can compare changes in data output from condition sensor <NUM> with stored information (e.g., stored in memory of the control unit <NUM>, such as random access memory (RAM), non-volatile memory, semi-volatile memory, or the like) describing how the condition sensor <NUM> parameter output changes during condensation conditions. If the target gas detection by the gas sensing core <NUM> is a true positive gas detection, then the controller <NUM> can initiate a notification, mitigation, and/or abatement process. For example, issuing an alarm, commencing a ventilation process, transitioning to a refrigerant conservation mode (e.g., including steps to isolate refrigerant in portions of the system), or other mitigation processes.

As used herein flammable refrigerant can refer to any refrigerant that is, or can be, classified under the A2L or A3 classification within the guidelines set forth by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Standard <NUM> Safety Classification in force as of the filing of the present application. For example, flammable refrigerants can include R-1234yf (<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene), R-<NUM> (propene), R-143a (<NUM>,<NUM>,<NUM>-trifluoroethan), R-152a (<NUM>,<NUM>-difluoroethane), R-<NUM> (trifluoromethane), R-<NUM> (difluoromethane), R-<NUM> (ethane), R-<NUM> (propane), and the like, and combinations comprising one or more of the foregoing, including blends thereof, such as for further example R-411A or R-411B (each a blend of R-<NUM>, R-<NUM> (chlorodifluoromethane), and R-152a), R-415A or R-415B (each a blend of R-<NUM> and R-152a), or R-454A, R454B, or R-454C (each a blend of R-<NUM> and R-1234yf (<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene)), and the like.

A third step <NUM>, of method <NUM> can include allowing at least a portion of fluid within the gas volume to fluidly interact with the gas sensing core <NUM>. For example, fluid in the gas volume can be pushed, or pulled, past the gas sensing core <NUM> by a fan within the fan section <NUM>. In another example, the gas sensing core <NUM> can be strategically positioned near likely target gas locations (e.g., such as ceilings for smoke detectors, end turns of an evaporator coils for refrigerant gas detectors, and the like). Such placement can allow the gas sensing core <NUM> to fluidly interact with a portion of fluid within the gas volume more likely to contain target gases of the gas sensing core <NUM>.

A fourth step <NUM> of the method <NUM> can include monitoring with the controller <NUM> a target gas measurement output from the gas sensing core <NUM> (e.g., an electrical output signal). The target gas measurement output can be any suitable electrical output signal that can communicate a change in conditions at the core (e.g., a change in target gas concentration). For example the target gas measurement output from the gas sensing core <NUM> can be discrete (e.g., digital, on/off, true/false, and the like) or continuous (e.g., analog, having a signal strength, or output value, corresponding to concentration of gases interacting with the gas sensing core <NUM>). The fourth step <NUM> can further include not annunciating, signaling, or indicating the presence of a target gas when the gas sensing core <NUM> output value is below a target gas measurement threshold value. The method <NUM> can include transitioning from the fourth step <NUM> to a fifth step <NUM> when the gas sensing core <NUM> output value exceeds a target gas measurement threshold value.

The target gas measurement threshold value can be configured based on the type of gas being monitored and the application of the gas sensor. In an HVAC/R application the target gas threshold value can be a function of the type of refrigerant used in the HVAC/R device <NUM>, the type of target gas sensing technology deployed, and/or the type of electrical output signal supplied by the gas sensing core <NUM>. For example, the gas sensing core <NUM> can be configured as a combustible gas sensor where the target gas measurement threshold value can be set based on the combustibility of the target gas in air. Such target gas measurement threshold value can be equal to from about <NUM>% to about <NUM>% of the lower flammability limit (LFL) concentration of the target gas. For example, the target gas measurement threshold value can be set to about <NUM> % of the LFL of R-454B (e.g. a blend of <NUM> weight % R-<NUM> and <NUM> weight % R-1234yf). In another example, in an HVAC/R device <NUM> having a gas sensing core <NUM> with a discrete electrical output signal, the target gas measurement threshold value can be set to <NUM> (e.g., "on", or "true", or the like).

The fifth step <NUM> of the method <NUM> can include monitoring with the controller <NUM> a parameter output from the condition sensor <NUM>. In addition to electrically interfacing with the electrical output of the gas sensing core <NUM>, the controller <NUM> can be configured in electrical communication with the condition sensor <NUM> and can simultaneously, or nearly simultaneously, monitor its electrical output signal.

A sixth step <NUM> of the method <NUM> can include recording a minimum parameter output value from the condition sensor <NUM> to a data storage device in electrical communication with the controller <NUM> (e.g., storing in volatile memory such as random access memory (RAM), non-volatile memory, semi-volatile memory, or the like). Recording the minimum parameter output value from the condition sensor <NUM> can include setting a timespan (e.g., timeframe and/or number of prior signals from the condition sensor <NUM>) over which the minimum parameter output is determined. That timespan can be chosen based on the dynamics of the condensation phenomena that occur on the gas sensing core <NUM>. For example, the timespan can be set to <NUM> minutes of prior readings from the temperature sensor <NUM>, or <NUM> minutes, or <NUM> minutes, or <NUM> minutes, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds, or <NUM> seconds of prior readings from the condition sensor <NUM>. The sixth step <NUM> can include recording a timestamp (e.g., representative of actual time) to the data storage device for each cycle that the controller <NUM> collects data.

The timespan over which the minimum parameter output is established can depend on the data collection cycle time (e.g., related to refresh rate) of the controller <NUM> rather than on a set time interval. The sixth step <NUM> can include recording the target gas measurement output signal from the gas sensing core <NUM> throughout the timespan. For example, the minimum parameter output from the condition sensor <NUM> can be decided based on a static or dynamic number of previously collected data points, e.g., the minimum value of the past <NUM> or less data points, e.g., the past <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> data points, or the like. The data refresh rate of the controller <NUM> can be less than or equal to about <NUM> Hertz (Hz), e.g., less than or equal to about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM> or about <NUM>, or the like. The controller <NUM> can be configured to update the minimum parameter output value stored in the data storage device with every data collection cycle of the controller <NUM>. For example, the minimum parameter output of condition sensor <NUM> stored in the memory can be updated at the same data refresh rate as the controller <NUM>.

A seventh step <NUM> of the method <NUM> can include calculating (e.g., with the controller <NUM>) a parameter difference between the stored minimum parameter output value and the instant parameter output from the condition sensor <NUM>. Further, the seventh step <NUM> can include comparing the calculated parameter difference to a parameter difference threshold value. The parameter difference threshold value can be configured based on empirical results showing that condensation has occurred on the gas sensing core <NUM>. For example, the condition sensor <NUM> can be configured as a temperature sensor where the parameter output is a temperature measured by the condition sensor <NUM> and the parameter difference threshold value is a temperature difference threshold set to less than or equal to about <NUM>, e.g., about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>, or about <NUM>. In another example, the condition sensor <NUM> can be configured as a humidity sensor where the parameter output is a humidity value (e.g., relative humidity) measured by the condition sensor <NUM> and the parameter difference threshold value is a humidity difference threshold set to less than or equal to about <NUM>%, e.g., about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%, or about <NUM>%.

Still further, the seventh step <NUM> can include indicating the presence of a target gas when a parameter difference is less than or equal to the parameter difference threshold value and the target gas measurement output from the gas sensing core <NUM> exceeds the target gas measurement threshold value. The method <NUM> can include advancing from the seventh step <NUM> to an eighth step <NUM> when the calculated parameter difference exceeds the parameter difference threshold value.

The eighth step <NUM> of the method <NUM> can include calculating (e.g., with the controller <NUM>) a rate of change of the parameter output of the condition sensor <NUM> with respect to time. For example, the rate of change of the parameter output of the condition sensor <NUM> can be calculated based on the difference between the instant parameter output value (e.g., the value from last data collection cycle of the controller <NUM>) and the recorded minimum parameter output value (e.g., such as the minimum value stored in memory in the sixth step <NUM>). In another example, the rate of change of the condition sensor <NUM> parameter output can be calculated based on the difference between one or more parameter output values (e.g., instant values and/values stored in memory of the data storage device) divided by the temporal difference of the recordings (e.g., as determined from the time elapsed between timestamps of the recordings). The eighth step <NUM> can include indicating the presence of the target gas when the calculated rate of change of the parameter with respect to time is less than or equal to a rate threshold value, the parameter difference exceeds the parameter difference threshold, and the target gas measurement output from the gas sensing core <NUM> exceeds the target gas measurement threshold value. The eighth step <NUM> can include not indicating the presence of a combustible gas mixture, and/or indicating a false positive, when the calculated rate of change of the parameter with respect to time exceeds the rate threshold value, the parameter difference exceeds the parameter difference threshold, and the target gas measurement output from the gas sensing core <NUM> exceeds the target gas measurement threshold value.

The rate threshold value can be configured based on empirical results showing that condensation has occurred on the gas sensing core <NUM>. For example, the condition sensor <NUM> can be configured as a temperature sensor where the parameter output is a temperature measured by the condition sensor <NUM>, the calculated rate of the parameter with respect to time is a rate of temperature change, and the rate threshold value can be set to about <NUM>/minute, e.g., about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute, or about <NUM>/minute.

In another example, the condition sensor <NUM> can be configured as a humidity sensor where the parameter output is a humidity value (e.g., relative humidity) measured by the condition sensor <NUM>, the calculated rate of change of the parameter with respect to time is a rate of percent humidity change, and the rate threshold value can be set to about <NUM> %/second, e.g., about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second, or about <NUM> %/second.

Although laid out in numerical order, any two or more steps of the method <NUM> can be performed sequentially or simultaneously. For example, monitoring the target gas measurement output from the gas sensing core <NUM> as in step four <NUM>, monitoring the parameter output of the condition sensor <NUM> as in the fifth step <NUM>, recording a minimum parameter output value from the condition sensor <NUM> to a data storage device as in the sixth step <NUM>, calculating a parameter difference between the stored minimum parameter output value and the instant parameter output from the condition sensor <NUM> as in the seventh step <NUM>, and calculating a rate of change of the parameter output of the condition sensor <NUM> with respect to time as in the eighth step <NUM>, can be performed simultaneously with all other steps of the method <NUM>.

Claim 1:
A method (<NUM>) of indicating the presence of a target gas in a gas volume comprising:
providing (<NUM>) a gas sensing core (<NUM>), configured for detection of the target gas, and a condition sensor (<NUM>) within the gas volume,
providing (<NUM>) a controller (<NUM>) disposed in electrical communication with the gas sensing core and the condition sensor,
allowing (<NUM>) gas within the gas volume to fluidly interact with the gas sensing core,
monitoring (<NUM>) with the controller a target gas measurement output from the gas sensing core,
monitoring (<NUM>) with the controller a parameter output from the condition sensor,
recording (<NUM>) a parameter output minimum value in a memory of the controller,
calculating (<NUM>) with the controller a parameter difference, wherein the parameter difference is the difference between the minimum value of the parameter and an instant value of the parameter,
calculating (<NUM>) with the controller a rate of change of the parameter with respect to time, and
indicating the presence of a target gas is detected in the gas volume when the target gas measurement exceeds a target gas measurement threshold value and the parameter difference is less than a parameter difference threshold value.