Patent Application
20240240819
The present disclosure relates generally to heating, ventilation, and air conditioning (HVAC) system control, and more specifically to refrigerant detection for a cooling system.
Heating, ventilation, and air conditioning (HVAC) systems are used to regulate environmental conditions within an enclosed space. Air is cooled or heated via heat transfer with refrigerant flowing through the system and returned to the enclosed space as conditioned air. During operation, refrigerant may leak from the working-fluid conduit subsystem or from one or more components.
Regulations in the HVAC industry are pushing manufacturers to transition away from traditional refrigerants towards low global warming potential (GWP) refrigerants, particularly mildly flammable (A2L) refrigerants and flammable (A3) refrigerants. Currently, there is a need to develop HVAC systems that are optimized for low GWP refrigerants. Notably, in the case of flammable refrigerants, such as A2L and A3 refrigerants, there is a need to develop mitigation systems and methods that can detect the presence of leaked refrigerant and implement strategies for mitigating the leak. This disclosure addresses the aforementioned problems by providing an HVAC system that can detect the presence of a leak and discharge at least a portion or all of the refrigerant out from the HVAC system.
In one embodiment, the system comprises an evaporator coil configured to receive an airflow and to transfer heat from the received airflow to a flow of refrigerant. The system further comprises a compressor configured to receive the flow of refrigerant from the evaporator coil and to discharge the flow of refrigerant at a higher pressure. The system further comprises a refrigerant detection sensor disposed upstream of the evaporator coil and configured to detect a concentration of refrigerant in a volume. The system further comprises a controller operably coupled to the refrigerant detection sensor, comprising a memory and a processor. The memory is configured to store a threshold value associated with a lower flammability limit of the refrigerant, wherein the lower flammability limit corresponds to the concentration of the refrigerant. The processor is operably coupled to the memory and configured to operate the HVAC system in a first mode of operation, wherein the HVAC system is turned on and energized during the first mode of operation. The processor is further configured to receive a plurality of concentration measurements from the refrigerant detection sensor. The processor is further configured to determine if the concentration of refrigerant in the volume exceeds the stored threshold value based at least in part on the received plurality of concentration measurements. In response to determining that the concentration of refrigerant in the volume does exceed the stored threshold value, the processor is configured to operate the HVAC system in a second mode of operation. During the second mode of operation, the compressor is turned off and a blower disposed downstream of the evaporator coil is actuated to discharge the airflow.
Certain embodiments of the present disclosure may include some, all, or none of these advantages. These advantages and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.
For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.
Cooling systems cycle refrigerant to cool various spaces. For example, a heating, ventilation, and air conditioning (HVAC) system cycles refrigerant to cool spaces near or around air conditioner loads. Refrigerant may leak from the working- fluid conduit subsystem or from one or more components at certain locations throughout the HVAC system. Depending on the refrigerant used, there is a risk that the concentration of leaked refrigerant accumulates to a threshold value indicative of flammability.
This disclosure contemplates an unconventional cooling system capable of detecting leaked refrigerant and discharging the refrigerant out of the HVAC system to reduce the accumulated concentration. This disclosure contemplates using a refrigerant detection sensor disposed within a housing near the drain pan underneath the evaporator coils. The cooling system will be described using
The HVAC system 100 may comprise a working-fluid conduit subsystem 102 for moving a working fluid, or refrigerant, through a cooling cycle. The working fluid may be any acceptable working fluid, or refrigerant, including, but not limited to, fluorocarbons (e.g. chlorofluorocarbons), ammonia, non-halogenated hydrocarbons (e.g. propane), hydrofluorocarbons (e.g. R-410A), A2L refrigerants, or any other suitable type of refrigerant. Without limitations, A2L refrigerants may include R-454b, R-32, R-1234yf, and R-1234ze.
The HVAC system 100 may comprise one or more condensing units 104. In one embodiment, the condensing unit 104 comprises a compressor 106, a condenser coil 108, and a fan 110. The compressor 106 is coupled to the working-fluid conduit subsystem 102 that compresses the working fluid. The condensing unit 104 may be configured with a single-stage or multi-stage compressor 106 or with multiple compressors. In the configuration of one or more compressors, the one or more compressors can be turned on or off to adjust the cooling capacity of the HVAC system 100. In some embodiments, a compressor 106 may be configured to operate at multiple speeds or as a variable speed compressor. For example, the compressor 106 may be configured to operate at multiple predetermined speeds.
The condenser 108 is configured to assist with moving the working fluid through the working-fluid conduit subsystem 102. The condenser 108 is located downstream of the compressor 106 for rejecting heat. The fan 110 is configured to move air 112 across the condenser 108. For example, the fan 110 may be configured to blow outside air through the heat exchanger to help cool the working fluid. The fan 110 may be coupled to a motor, wherein the motor may be configured to actuate the fan 110.
With reference back to the flow of the working fluid, the compressed, cooled working fluid flows downstream from the condenser 108 to an expansion device 114, or a metering device. The expansion device 114 is configured to remove pressure from the working fluid. The expansion device 114 is coupled to the working-fluid conduit subsystem 102 downstream of the condenser 108 for removing pressure from the working fluid prior to flowing to an evaporator 116. The expansion device 114 may be closely associated with the evaporator 116. In this way, the working fluid is delivered to the evaporator 116 and receives heat from airflow 118 to produce a treated airflow 120 that is delivered by a duct subsystem 122 to the desired space, for example, a room in the building.
In embodiments, refrigerant, such as an A2L refrigerant, flowing through the working-fluid conduit subsystem 102 may have an increased probability of leaking in an area proximate to the evaporator 116. To maintain compliance standards, the HVAC system 100 may be configured to detect a concentration of leaking refrigerant and reduce the concentration within pre-determined periods of time. As illustrated, the HVAC system 100 may further comprise a refrigerant detection sensor 117 disposed in proximity to the evaporator 116 configured to detect a concentration of refrigerant in a volume. The refrigerant detection sensor 117 may be disposed upstream or downstream of the evaporator 116. The refrigerant detection sensor 117 may be any suitable sensor and/or collection of equipment operable to detect a concentration of refrigerant. Without limitations, the refrigerant detection sensor 117 may be a gas sensor, speed of sound sensor, thermal conductivity sensor, heated diode leak detector, or any combination thereof.
In an embodiment, the refrigerant detection sensor 117 may be in signal communication with a controller 124 using a wired or wireless connection. The controller 124 may be configured to provide commands or signals to control the operation of the HVAC system 100. An example of the controller 124 in operation is described further below in
As an example, the controller 124 may comprise a processor 128, a memory 130, and a network interface 132. In embodiments, the controller 124 may further comprise a graphical user interface, a display, a touch screen, buttons, knobs, or any other suitable combination of components. The controller 124 may be configured as shown or in any other suitable configuration.
The processor 128 comprises one or more processors operably coupled to the memory 130. The processor 128 is any electronic circuitry including, but not limited to, state machines, one or more central processing unit (CPU) chips, logic units, cores (e.g. a multi-core processor), field-programmable gate array (FPGAs), application- specific integrated circuits (ASICs), or digital signal processors (DSPs). The processor 128 may be a programmable logic device, a microcontroller, a microprocessor, or any suitable combination of the preceding. The processor 128 is communicatively coupled to and in signal communication with the memory 130 and the network interface 132. The one or more processors may be configured to process data and may be implemented in hardware or software. For example, the processor 128 may be 8-bit, 16-bit, 32-bit, 64-bit, or of any other suitable architecture. The processor 128 may include an arithmetic logic unit (ALU) for performing arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memory and executes them by directing the coordinated operations of the ALU, registers and other components. The one or more processors are configured to implement and execute various instructions. The instructions may comprise any suitable set of instructions, logic, rules, or code operable to be executed. In this way, processor 128 may be a special-purpose computer designed to implement the functions disclosed herein.
The memory 130 is operable to store any of the information described with respect to
The network interface 132 is configured to enable wired and/or wireless communications. The network interface 132 is configured to communicate data between the controller 124 and other devices (e.g. sensors and the HVAC system 100), systems, or domains. For example, the network interface 132 may comprise an NFC interface, a Bluetooth interface, a Zigbee interface, a Z-wave interface, an RFID interface, a WIFI interface, a LAN interface, a WAN interface, a PAN interface, a modem, a switch, or a router. The processor 128 may be configured to send and receive data using the network interface 132. The network interface 132 may be configured to use any suitable type of communication protocol as would be appreciated by one of ordinary skill in the art.
In further embodiments, controller 124 may include a display that is a graphical user interface configured to present visual information to a user using graphical objects. Examples of a display include, but are not limited to, a liquid crystal display (LCD), a liquid crystal on silicon (LCOS) display, a light-emitting diode (LED) display, an active-matrix OLED (AMOLED), an organic LED (OLED) display, a projector display, or any other suitable type of display as would be appreciated by one of ordinary skill in the art.
A portion of the HVAC system 100 may be configured to move air across the evaporator 116 and out of the duct sub-system 122. Return air 134, which may be air returning from the building, fresh air from outside, or some combination, is pulled into a return duct 136. A variable-speed blower, such as blower 126, may pull the return air 134 into the return duct 136 where the airflow 118 crosses the evaporator 116 or heating elements (not shown) to produce the treated airflow 120. In these embodiments, the return air 134 may be the same airflow as airflow 118 or may be discharged as airflow 118 by blower 126.
The HVAC system 100 may comprise one or more sensors 138 in signal communication with the controller 124. The sensors 138 may comprise any suitable type of sensor for measuring the air temperature. The sensors 138 may be positioned anywhere within a conditioned space (e.g. a room or building) and/or the HVAC system 100. For example, the HVAC system 100 may comprise a sensor 138 positioned and configured to measure an outdoor air temperature. As another example, the HVAC system 100 may comprise a sensor 138 positioned and configured to measure a supply or treated air temperature and/or a return air temperature. In other examples, the HVAC system 100 may comprise sensors 138 positioned and configured to measure any other suitable type of air temperature, pressure, humidity, or any other suitable parameter.
The HVAC system 100 may comprise one or more thermostats, for example, located within a conditioned space (e.g. a room or building). The thermostat may be a single-stage thermostat, a multi-stage thermostat, or any suitable type of thermostat as would be appreciated by one of ordinary skill in the art. The thermostat may be configured to allow a user to input a desired temperature or temperature set point for a designated space or zone such as the room.
The return air 134 may engage with the evaporator 116 as the return air 134 flows through the RTU. For example, during a refrigeration cycle, heat may transfer from the return air 134 to the refrigerant flowing through the evaporator 116 as the return air 134 flows through and/or around evaporator 116. The removal of heat from return air 134 may reduce the temperature of the return air 134, thereby treating the return air 134 and producing treated airflow 120. Before flowing through the evaporator 116, the return air 134 may engage with an air filter 206 disposed upstream of the evaporator 116. The air filter 206 may be any suitable filter configured to remove at least a portion of particles or particulate matter present within an airflow. The air filter 206 may be configured to remove particles from the return air 134 prior to the HVAC system 100 discharging the return air 134 after treatment (i.e., as treated airflow 120).
The HVAC system 100 may further comprise a drain pan 208 disposed underneath the evaporator 116. The drain pan 208 may be configured to collect condensation or any fluids that may be produced and find their way to the drain pan.
For example, operation of evaporator 116 may produce water condensate from return air 134 as heat is removed from the return air 134. In another example, ice and/or frost build-up present on the coils of the evaporator 116 may melt and produce water condensate during a defrost cycle. The drain pan 208 may comprise any suitable size, height, shape, and any combinations thereof. Further, the drain pan 208 may comprise any suitable materials, such as metals, nonmetals, polymers, composites, and any combinations thereof. The drain pan 208 may be flat and/or angled to help direct liquids to a drain aperture, or drain, and an associated drain line to discharge the collected condensate out of the RTU. As illustrated, the drain pan 208 may be disposed under the evaporator 116 and between the air filter 206 and the blower stand 206.
The blower stand 206 may comprise at least one side 210 that is angled with respect to a vertical axis, wherein the angle of the at least one side 210 provides for the blower stand 206 to direct a fluid down and towards the drain pan 208. For example, if refrigerant is leaking from evaporator 116 during operations, gravity may pull the refrigerant in a downward direction toward the drain pan 208 as the refrigerant may weigh more than the surrounding air. However, air may be flowing through the RTU and may force the falling refrigerant in a lateral direction vertically offset from the drain pan 208. In this example, the refrigerant may encounter the at least one side 210 of the blower stand 206 and may be directed to flow back towards the drain pan 208.
The HVAC system 100 may comprise a flange 308 disposed adjacent to the drain pan 208 and at the bottom of the HVAC system 100. The flange 308 may be configured to section off a portion of HVAC system 100 and prevent condensate or fluids overflowing from the drain pan 208 to spread upstream from the evaporator 116.
The flange 308 may be disposed between the air filter 206 and the drain pan 208. In embodiments, the flange 308 may have approximately an equivalent length as the RTU (i.e., the HVAC system 100). The flange 308 may have a length equal to or greater than the drain pan 208. The flange 308 may comprise any suitable size, height, shape, and any combinations thereof. Further, the flange 308 may comprise any suitable materials, such as metals, nonmetals, polymers, composites, and any combinations thereof. The flange 308 may comprise a main support 310 and a lateral side 312. The main support 310 may extend vertically upwards from the bottom of the HVAC system 100. The lateral side 312 may be disposed perpendicular to the main support 310 and may extend towards the drain pan 208. The lateral side 312 may extend to an area at least partially below the evaporator 116. As illustrated, the lateral side 312 may be disposed at a height greater than the first side 302 of drain pan 208, wherein there may be a clearance of any suitable distance between the lateral side 312 and first side 302.
There may be a hole 314 defined in the main support 310. The hole 314 may be any suitable size and shape. The hole 314 may be disposed at a height greater than the first side 302 of the drain pan 208. In other embodiments, hole 314 may be disposed at a height less than the first side 302. The hole 314 may be configured to direct refrigerant having leaked from HVAC system 100 into a housing 316 containing the refrigerant detection sensor 117. The housing 316 may comprise any suitable size, height, shape, and any combinations thereof. As shown, the housing 316 may generally be rectangular, but the housing 316 is not limited to such a shape. Further, the housing 316 may comprise any suitable materials, such as metals, nonmetals, polymers, composites, and any combinations thereof. The housing 316 may be defined by a plurality of closed sides disposed against the main support 310 of the flange 308. In embodiments, the housing 316 may be sealed against the main support 310. The housing 316 may define an internal volume 318 used for detecting a concentration of refrigerant by the refrigerant detection sensor 117. The housing 316 may be disposed between the flange 308 and the air filter 206. In embodiments, the housing 316 may be disposed in proximity to an internal access point for the HVAC system 100 (for example, within 30 inches from an access door to an RTU) for ease of maintenance and field servicing.
The housing 316 may be configured to contain the refrigerant detection sensor 117 within the internal volume 318. The housing 316 may be configured to prevent leaked refrigerant from diffusing away from the internal volume 318 and protect the refrigerant detection sensor 117 from an external environment. The refrigerant detection sensor 117 may be disposed at a bottom of the housing 316. In other embodiments, the refrigerant detection sensor 117 may be elevated within the housing 316 as long as the hole 314 maintains a greater height (i.e., the refrigerant detection sensor 117 is not disposed along a parallel plane in-line with the hole 314). In these embodiments, the height difference may prevent fluid from splashing against the refrigerant detection sensor 117 as fluid enters the housing 316 through the hole 314.
During operation of HVAC system 100, refrigerant may leak and be collected in drain pan 208. In embodiments, the collected refrigerant may start to overflow and spill over first side 302 between the first side 302 and the main support 310 of flange 308. The refrigerant may then encounter hole 314 and flow into the housing 316 via the hole 314. As the refrigerant flows into the housing 316, the refrigerant may be contained in the housing 316, and the refrigerant detection sensor 117 may measure a concentration of that refrigerant with respect to the internal volume 318 over a period of time. The refrigerant detection sensor 117 may be configured to transmit a plurality of concentration measurements of the refrigerant to the controller 124 (referring to
Graph 400 depicts a first line 402 illustrating performance of refrigerant detection sensor 117 with the housing 316 and a second line 404 illustrating performance of refrigerant sensor 117 without the housing 316. In these embodiments, performance is measured as % LFL over time. As illustrated at a first point 406, the HVAC system 100 was able to determine that the % LFL of refrigerant present within the internal volume 318 (referring to
At operation 504, the processor 128 of the controller 124 may receive a plurality of concentration measurements of a refrigerant leaking from the working-fluid conduit subsystem 102. For example, during operation of HVAC system 100 in a first mode o operation, refrigerant may leak and be collected in the drain pan 208 (referring to
At operation 506, the processor 128 of the controller 124 may determine whether or not the concentration of refrigerant in the internal volume 318 exceeds a threshold value. For example, the memory 130 (referring to
At operation 508, the processor 128 of the controller 124 may transmit a notification indicating that the HVAC system 100 has detected a leak of refrigerant. Transmission of the notification may occur in conjunction with, before, or after the HVAC system 100 transitions from the first mode of operation to a second mode of operation to reduce the concentration of refrigerant leaking into the HVAC system 100.
At operation 510, the processor 128 of the controller 124 may actuate the HVAC system 100 to transition to the second mode of operation. During the second mode of operation, the processor 128 may transmit an instruction to turn off the compressor 106 and to actuate the blower 126 to discharge an airflow. In these embodiments, the airflow may comprise a concentration of refrigerant exceeding the stored threshold value. Discharging the airflow may reduce the concentration of refrigerant present within the HVAC system 100.
At operation 512, the processor 128 of the controller 124 may terminate operation of the HVAC system 100 for maintenance when the concentration of refrigerant decreases to a value below the stored threshold value in the memory 130 as a result, for example, of discharging the airflow in conjunction with operation 510. For example, after the HVAC system 100 transitions to the second mode of operation, the concentration of refrigerant leaking within the HVAC system 100 decreases due to the discharge of the leaked refrigerant mixed with the air. There may be a certain volume of leaked refrigerant remaining within one or more components in the HVAC system 100, such as in the drain pan 208 and/or housing 316. The HVAC system 100 may terminate operations in order for an operator to access and service the interior of the HVAC system 100, wherein the process 500 may then proceed to end.
While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated with another system or certain features may be omitted, or not implemented.
In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.
To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants note that they do not intend any of the appended claims to invoke 35 U.S.C. § 112(f) as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.
