Leak detection method for zeotropic refrigerants

Abstract

A leak detection system and method are provided. The system includes: a heater configured to receive a refrigerant from a refrigeration circuit, to heat the refrigerant and to thereby output a first constituent component of the refrigerant in a vapor state and output a second constituent component of the zeotropic refrigerant in a liquid state. Relative mass flows of the first constituent component and the second constituent component may be determined directly or may be inferred from a change in pressure of the refrigerant prior to and after heating or from a liquid level change of the second constituent component in a tank. One or more of the relative mass flows, the change in pressure, and the liquid level change may be compared to a predetermined value, and a refrigeration leak alert may be output based on the comparison.

Description

LEAK DETECTION METHOD FOR ZEOTROPIC REFRIGERANTS

[0001] This Application claims priority from U.S. Provisional Application 63 / 634699, filed April 16, 2024 in the United States Patent Office.BACKGROUND1. Field

[0002] Apparatuses and methods consistent with example embodiments relate to leak detection systems and methods, and more particularly to detection of a leak of refrigerant from a refrigeration circuit.2. Description of Related Art

[0003] Broadly, a zeotropic mixture is a mixture with liquid components that have different boiling points. More specifically, a zeotropic refrigerant includes two or more components whose equilibrium vapor phase and liquid phase compositions are different. Thus, the temperature of a zeotropic refrigerant changes as it evaporates or condenses at a constant pressure.

[0004] Zeotropic mixtures are used in refrigeration, and have been proposed as substitutes to halogenated refrigerants due to the harmful effects that hydrochlorofluorocarbons (HCFC) and chlorofluorocarbons (CFC) have on the ozone layer and global warming. Zeotropic mixtures that are used in refrigeration are assigned a number in the 400 series to help identify their components and their proportions as a part of nomenclature. According to the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), refrigerants names start with 'R' followed by a series of numbers — 400 series if it is zeotropic or 500 if it is azeotropic — followed by uppercase letters that denote the composition. R454B is a particular mixture used as a refrigerant.

[0005] There are some technical difficulties, however, including leakages, associated with using zeotropic mixtures. When a refrigerant leaks out of a refrigeration circuit, the cooling capacity of the refrigeration circuit is diminished, and there is an increased fire hazard. With respect to flammability, there are three ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) classifications and one subclass. The three classes are: class 1, for refrigerants that do not propagate a flame when tested; class 2 for refrigerants of lower flammability; and class 3, for highly flammable refrigerants such as hydrocarbons. The subclass is 2L for flammability class 2 refrigerants that bum very slowly. Among newer zeotropic refrigerants, for example, R436C, R441 A, and R443A are all in class 3 for flammability.

[0006] Current leak detection systems work by detecting a leaked refrigerant in the air surrounding a refrigeration circuit. This requires very sensitive detection devices, commonly referred to as “sniffers,” that are positioned near enough to the refrigeration circuit, and hopefully near enough to the leak, to be exposed to a critical concentration of leaked gas that will then be detected. Although systems are engineered to create robust sensing systems that meet safety standards and regulatory codes, such systems are not perfect and could miss small leaks over time, allowing the leakage of mildly flammable or environmentally damaging refrigerant into the air. Sniffing sensors have particular trouble with high velocity moving air, limiting their effectiveness when evaporator fans, or other fans or blowers used with heat exchangers, are running.SUMMARY OF EXAMPLE EMBODIMENTS

[0007] Example embodiments may address at least the above problems and / or disadvantages and other disadvantages not described above. Also, example embodiments arenot required to overcome the disadvantages described above, and may not overcome any of the problems described above.

[0008] According to an aspect of an example embodiment, a leak detection system comprises: a heater configured to receive a refrigerant from an input line and to heat the refrigerant and thereby output a first constituent component of the refrigerant in a vapor state and output a second constituent component of the refrigerant in a liquid state; a tank which receives the first constituent component and the second constituent component output from the heater and holds therein the first constituent component in the vapor state and the second constituent component in the liquid state; a first valve which controls passage of the first constituent component in the vapor state from the tank to an output line; a second valve which controls passage of the second constituent component in the liquid state from the tank to the output line; a liquid level monitor which senses a liquid level in the tank and outputs data; a controller, coupled to the liquid level monitor, which receives the data from the liquid level monitor, determines whether a sensed change in the liquid level is greater than a predetermined level change, and outputs information indicating a potential refrigerant leak if the sensed change in the liquid level is greater than the predetermined level change.

[0009] The leak detection system may further comprise: a pump which taps the refrigerant from a line in a refrigeration circuit and directs the refrigerant to the input line.

[0010] The leak detection system may further comprise: at least one heat sensor, disposed within the heater, which outputs temperature data; wherein the controller is further coupled to the at least one heat sensor and to the heater, receives the temperature data from the at least one heat sensor, and controls the heater to heat the refrigerant to a temperature between a boiling point of the first constituent component and a boiling point of the second constituent component.

[0011] According to an aspect of another example embodiment a leak detection system comprises: a heater configured to heat a refrigerant provided from an input line and thereby output, on an output line, a first constituent component of the refrigerant in a vapor state and a second constituent component of the refrigerant in a liquid state; a first pressure tap, disposed on the input line, which senses a pressure of the refrigerant and outputs first pressure data; a second pressure tap, disposed on the output line, which senses a pressure of the refrigerant and outputs second pressure data; a controller, coupled to the first pressure tap and to the second pressure tap, which receives the first pressure data and the second pressure data, determines whether a sensed change in pressure between the first pressure and the second pressure is greater than a predetermined pressure change, and outputs information indicating a potential refrigerant leak if the sensed change in the pressure is greater than the predetermined pressure change.

[0012] The leak detection system may further comprise: a pump which taps the refrigerant from a line in the refrigeration circuit and directs the refrigerant to the input line.

[0013] The leak detection system may further comprise: at least one heat sensor, disposed within the heater, which outputs temperature data; wherein the controller is further coupled to the at least one heat sensor and to the heater, receives the temperature data from the at least one heat sensor, and controls the heater to heat the refrigerant to a temperature between a boiling point of the first constituent component and a boiling point of the second constituent component.

[0014] According to an aspect of another example embodiment, a refrigeration circuit may comprise: a condenser; an expansion valve; an evaporator; a line transmitting refrigerant through the circuit; a leak detection system as described above; and a pump, which taps the refrigerant from the line of the refrigeration circuit and directs the refrigerant to the input line.

[0015] According to an aspect of another example embodiment, a leak detection method may comprise: tapping a refrigerant from a line in a refrigeration circuit; heating the refrigerant to a temperature between a boiling point of a first constituent component of the refrigerant and a boiling point of a second constituent component of the refrigerant; holding, in a tank, the first constituent component in a vapor state and the second constituent component in a liquid state; controlling output of the first constituent component in the vapor state and the second constituent component in the liquid state from the tank; sensing a liquid level within the tank; determining whether a sensed change in the liquid level is greater than a predetermined level change; and outputting information indicating a potential refrigerant leak if the sensed change in the liquid level is greater than the predetermined level change.

[0016] According to an aspect of another example embodiment, a leak detection method may comprise: tapping a refrigerant from a line in a refrigeration circuit; heating the refrigerant to a temperature between a boiling point of a first constituent component of the refrigerant and a boiling point of a second constituent component of the refrigerant; sensing a first pressure of the refrigerant before the heating; sensing a second pressure of the refrigerant after the heating; determining whether a sensed pressure change between the first pressure and the second pressure is greater than a predetermined pressure change; and outputting information indicating a potential refrigerant leak if the sensed pressure change is greater than the predetermined pressure change.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or other example aspects will become apparent and more readily appreciated from the following description of example embodiments, taken in conjunction with the accompanying drawings, in which:

[0018] FIG. 1 illustrates an example refrigeration circuit according to the related art;

[0019] FIG. 2 illustrates a leak detection system according to an example embodiment;

[0020] FIG. 3 is a block diagram of a computer according to an example embodiment;

[0021] FIG. 4 is a flow diagram of a first example function of a leak detection system according to an example embodiment;

[0022] FIG. 5 is a flow diagram of a second example function of a leak detection system according to an example embodiment;

[0023] FIG. 6 illustrates a start-up method of a leak detection system according to an example embodiment;

[0024] FIG. 7 illustrates a leak detection system according to another example embodiment; and

[0025] FIG. 8 illustrates a second example function of a leak detection system according to another example embodiment.DETAILED DESCRIPTION

[0026] Reference will now be made in detail to example embodiments which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the example embodiments may have different forms and may not be construed as being limited to the descriptions set forth herein.

[0027] It will be understood that the terms “include,” “including,” “comprise,” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0028] It will be further understood that, although the terms “first,” “second,” “third,” etc., may be used herein to describe various elements, components, regions, layers and / or sections,these elements, components, regions, layers and / or sections may not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section.

[0029] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

[0030] Various terms are used to refer to particular system components. Different companies may refer to a component by different names - this document does not intend to distinguish between components that differ in name but not function.

[0031] Matters of these example embodiments that are obvious to those of ordinary skill in the technical field to which these example embodiments pertain may not be described herein in detail.

[0032] One or more example embodiments described herein are designed to function differently from sniffers - rather that detecting leaked gas, to instead analyze the refrigerant remaining in a refrigeration circuit and infer, based on a change of properties of the remaining refrigerant, if there is a leak in the circuit. The monitoring may be continuous or intermittent, depending on circumstances. In this way, a system may allow monitoring of any potential leak point rather than only those leak points with sniffing sensors nearby. A system or method according to one or more example embodiments, including such analysis and monitoring of properties of refrigerant in a refrigeration circuit, may improve upon related art leak detection systems allowing a potentially problematic leak to be detected at an earlier stage, and / or to be detected independent of the location of the leak in the refrigeration circuit.

[0033] Additionally, a system according to one or more example embodiments may also improve upon related art leak detection systems due to leak detection based on analysis andmonitoring of properties of refrigerant within a refrigeration circuit being independent of factors such as indoor airflow patterns and sensor malfunction or fouling, and potentially catching leaks on an outdoor side of the circuit (where sensors are not typically used). These example capabilities could enable a system according to one or more example embodiments to alert a user of a leak and allow servicing before a critical amount of refrigerant is lost causing cooling to be disabled. Such a system according to one or more example embodiments could also reduce an overall amount of environmentally harmful refrigerant that is released into the atmosphere, thus making the system “greener.”

[0034] According to one or more example embodiments a leak detection system may include a controller running an algorithm and controlling one or more other elements of the system to identify the location of a leak by varying system pressure and monitoring the leak response.

[0035] Zeotropic refrigerant blends, such as R454B, have two or more constituent refrigerant gasses that boil at different temperatures and have different viscosities. In the event of a system leak, the differences in boiling temperatures and viscosities may cause the constituent refrigerants gasses to leak at uneven rates. For example, R454B is comprised of 68.9% R32 (difluoromethane) and 31.1% R1234yf (2,3,3,3-Tetrafluoropropylene), and has a temperature glide of 1.5K. As the ratio of R32 to R1234yf changes, the ratio of mass flow rates for each fluid will change slightly, even with a consistent total mass flow rate of R454B. A device according to one or more example embodiments may identify the two constituent components separately and estimate their relative mass flow rates, and infer thereby that there is a leak if drift is observed in a difference between the relative mass flow rates. As a leak increases, a larger and larger gap (difference) may be observed in the relative mass flow rates of the fluids. The mass flow rates may be sensed directly using one or more mass flow meters. According to another example, discussed further below, a liquid level monitor,discussed below, may control an amount of liquid and vapor of the respective constituent components to be constant such that when the liquid and vapor amounts change, this results in a change in a liquid level allowing for an accurate determination of the mass flow rates. According to yet another example discussed further below, a pressure drop of a refrigerant blend across a heater or other evaporator coil may be sensed to determine the mass flow rates of separate components of the refrigerant blend.

[0036] In the event of a leak of R454B or of another zeotropic refrigerant, the different components will leak at uneven rates, and thus, the composition of the refrigerant remaining in the circuit will change accordingly. According to one or more example embodiments, the presence of a leak may be determined based on a change in the composition of the refrigerant remaining in the system. As noted with respect to the examples described above, the constituent components of a refrigerant have different characteristics, will behave at least somewhat differently. Thus, a leak will cause a differential in behavior resulting from a change in the concentrations of each component in the refrigerant due, and this differential will be an indicator of the leak.

[0037] According to a first example embodiment, a zeotropic refrigerant is heated to boil off one of the constituent components of the refrigerant, and then the mass flow of one of the components relative to the other is measured. If the mass flow rates of the constituent components are drifting from each other, the presence of a leak can be inferred. In the case of this first example embodiment, the relative mass flow rates may be determined based on a change in a liquid level in a tank where the tank holds a first component in a liquid state and a second component in a vapor state. As a leak increases, there will be a greater difference in the behavior of the constituent components.

[0038] FIG. 1 illustrates an example refrigeration circuit 10 including a condenser 30, an evaporator 50, a compressor 20, an expansion valve 40, and lines 60 connecting the otherelements. This example circuit 10 constitutes a theoretical Linde circuit, as would be understood by those of skill in the art, in which the condenser 30 expels heat from the system 10 while the evaporator 50 draws a cooling effect into the system 10. The compressor 20 increases the pressure, temperature, and energy of a vapor refrigerant, slightly decreasing its energy and specific volume as the refrigerant transitions from a saturated vapor to a saturated liquid. High pressure refrigerant from the compressor 20 is directed to the condenser 30 in which the saturated vapor refrigerant from the compressor 20 is transitioned to a saturated liquid refrigerant under constant pressure and temperature conditions. The refrigerant from the condenser 30 passes through the expansion valve 40 which lowers the pressure, such that the refrigerant exits the expansion valve 40 as a liquid-vapor mixture. The expansion valve 40 may be, for example, an electronic expansion valve (EEV). The refrigerant is directed to the evaporator 50 where it absorbs heat, reaches its boiling point, and evaporates, such that low-pressure vapor refrigerant is directed from the evaporator 50 back to the compressor 20. Operations of any one or more of the compressor 20, condenser 30, expansion valve 40, and evaporator 50 may be controlled by a controller (not illustrated) operatively coupled to one or more components of the circuit 10.

[0039] FIG. 2 illustrates a leak detection system 100 according to an example embodiment. The system 100 is attached to a refrigeration circuit, such as the example refrigeration circuit 10 illustrated in FIG. 1, and may be connected on a line 60 of the refrigeration circuit 10 between the condenser 30 and the expansion valve 40. The refrigeration circuit to which the system 100 is applied may be any refrigeration circuit including, but not limited to a system for use in comfort cooling, commercial refrigeration, and information technology (IT) cooling.

[0040] In this example, the refrigerant is a zeotropic refrigerant including a first component A with a boiling point a’ and a second component B with a boiling point b’, where the boilingpoint a’ is lower than the boiling point b’. The refrigerant may be, for example R454B, where R32 is component A and R1234yf is component B, but this example embodiment is not limited to this specific refrigerant or these specific components.

[0041] The system 100, of this example embodiment, includes a pump 110, a heater 120, a tank 130, two pilot valves 140, 150, and a controller 160, as well as various sensors and monitors, as discussed below. The tank 130 may be taller than it is wide, as would be understood by one of skill in the art, to enable a sensitive change in liquid level therein, as discussed below. However, the tank 130 is not limited thereto, and may have any shape and volume as determined by one of skill in the art. The heater 120 may be, for example, a simple resistance element with a low thermal mass and a variable, low voltage direct current (DC) power supply, but is not limited thereto. The pump 110 draws a small amount of zeotropic refrigerant from the liquid line 60 in a sub-cooled state (at a temperature below the saturation temperatures of the constituent components), and controls the pressure thereof. The pump may be, for example, a pump with a power of 100 watts (W) or less, but is not limited thereto. The controller 160, communicatively and operatively coupled to the pump 110, controls the pump 110. When drawn by the pump 110, the components of the refrigerant in the sub-cooled state are directed into a heater 120. The heater 120 raises the temperature of the refrigerant to between a boiling point of component A and a boiling point of component B. The temperature of the components within the heater 120 may be monitored by one or more temperature sensors (not shown). Thus, as the refrigerant travels through the heater 120, in a first zone 120A, the refrigerant is in a homogeneous subcooled state; in a second zone 120B, the refrigerant has been heated and includes component A in a subcooled phase and component B in a liquid phase; and in a third zone 120C, the refrigerant has been further heated such that component A has been boiled off and the refrigerant includes a superheated vapor of component A and a sub-cooled component B liquid. The controller 160 may also becommunicatively and operatively coupled to the heater 120 and may thereby control the heater 120. One or more thermocouples (not shown) may be positioned at any of various locations within the heater and communicatively and operatively coupled to the controller 160 to monitor temperature within the heater and ensure that the temperature is precisely controlled such that only one of the constituent components of the refrigerant is boiled off.

[0042] The superheated vapor of component A and the subcooled component B are directed from the heater 120 to the tank 130 via a gas line 170a and a liquid line 170b. Thus, in an example in which the refrigerant is R454B, component A is heated to pure R32 gas within the heater 120 and is transported to the tank 130 in the gas line 170a, and component B, pure R1234yf, is transported from the heater 120 to the tank 130 in the liquid line 170b.

[0043] The gas A and the liquid B remain separated in the tank 130. First and second pilot valves 140 and 150 are coupled to the tank 130, respectively corresponding to the two constituent components A and B in their gas and liquid states. The pilot valves 140, 150 and maintain constant pressure for the liquid and gas outlets from the tank 130 and maintain constant volumetric and mass flow out of the tank 130. The pilot valves 140, 150 may be simple mechanical valves or may be electronic valves communicatively and operatively coupled to and controlled by, for example, the controller 160. Thus, the volume and mass flow out of the tank 130 is maintained constant such that if there is a change in the volume and mass flow into the tank 130 due to a change in the relative concentrations of the components A and B, the liquid level in the tank will change correspondingly.

[0044] A liquid level monitor 136 is attached to the tank 130 and to a float 135 within the tank 130. Via its connection to the float 135, the liquid level monitor 136 determines a column height of the liquid B in the tank 130, on which the float 135 is floating, and information related to the column height of the liquid B in the tank 130 is transmitted to the controller 160. The liquid level monitor 136 may be, for example, a magnetostrictive leveltransmitter, but is not limited thereto. The controller 160 is communicatively coupled to the pump 110, the heater 120, and the digital liquid level monitor 136. Based on data received from the liquid level monitor 136, the heater 120, and the pump 110, the controller analyzes the liquid column height over time, i.e. a trend of the liquid level height, and can output information, in the form of an alert, for example, which may indicate a potential leak. The controller 160 also uses the received data to adjust the pump 110 to thereby control the system pressure.

[0045] The vapor and liquid of the constituent components A and B, respectively, exit the tank 130 via the valves 140, 150, and are directed to a line 180 in which they are re-mixed. The line 180 directs the refrigerant that transited the system 100 back to the liquid line 60 of the refrigeration circuit 10 to be directed to the expansion valve 40.

[0046] One or more additional sensors, including, but not limited to pressure sensors, may be positioned within the tank 130 and / or within any of the gas and liquid lines and / or within the heater 120 and may be communicatively and operatively coupled to the controller 160.

[0047] The controller 160 may be a part of an existing controller of a refrigeration circuit to which the leak detection system 10 is attached, may be a part of another existing controller operatively connected to a refrigeration circuit, such as, for example, a building controller, or may be a controller specific to the leak detection system 100 and either operatively independent of any existing controller or coupled to and cooperative with an existing controller.

[0048] The controller 160 may be a computer 300, as shown in FIG. 3 including a processing unit 301, a system memory 302, and a system bus 303. The system bus 303 couples system components including, but not limited to, the system memory 302 to the processing unit 301. The processing unit 301 can be any of various available processors. Dualmicroprocessors and other multiprocessor architectures also can be employed as the processing unit 301.

[0049] The system bus 303 can be any of several types of bus structures including a memory bus or memory controller, a peripheral bus or external bus, and / or a local bus using any of a variety of available bus architectures including, but not limited to, Industrial Standard Architecture (ISA), Micro-Channel Architecture (MSA), Extended ISA (EISA), Intelligent Drive Electronics (IDE), VESA Local Bus (VLB), Peripheral Component Interconnect (PCI), Card Bus, Universal Serial Bus (USB), Advanced Graphics Port (AGP), Personal Computer Memory Card International Association bus (PCMCIA), Firewire (IEEE 1394), and Small Computer Systems Interface (SCSI).

[0050] The system memory 302 may include volatile memory and nonvolatile memory.

[0051] A basic input / output system (BIOS), containing basic routines to transfer information between elements within the computer, such as during start-up, may be stored in nonvolatile memory. By way of non-limiting example, nonvolatile memory may include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory, or nonvolatile random access memory (RAM) (e.g., ferroelectric RAM (FeRAM). Volatile memory may include random access memory (RAM), which may act as an external cache memory. By way of non-limiting example, RAM is available in many forms such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), direct Rambus RAM (DRRAM), direct Rambus dynamic RAM (DRDRAM), and Rambus dynamic RAM.

[0052] The computer may also include removable and / or non-removable, volatile and / or non-volatile computer storage media, for example, a disk storage. A disk storage may include, but is not limited to, a magnetic disk drive, floppy disk drive, tape drive, Jaz drive, Zip drive, LS-100 drive, flash memory card, and a memory stick. Disk storage also may include storage media separately or in combination with other storage media including, but not limited to, an optical disk drive such as a compact disk ROM device (CD-ROM), CD recordable drive (CD-R Drive), CD rewritable drive (CD-RW Drive) or a digital versatile disk ROM drive (DVD-ROM). To facilitate connection of the disk storage devices to a system bus, a removable or non-removable interface may be used.

[0053] A first example function of the controller 160 is to monitor and / or control various elements of the system 100, including the pump 110, the heater 120, and the valves 140, 150, to ensure that they are functioning properly and that the refrigerant is accurately split by the heater into its constituent parts. A second example function of the controller 160 is to receive information from the liquid level monitor 136, to analyze the liquid level over time (i.e. a trend of the liquid level), and, based on the trend of the liquid level, determine whether there is a leak, and output information.

[0054] FIG. 4 illustrates an example method of the first example function. Regarding this first example function, the controller 160 receives data from the pump 110 and the heater 120 (S101). The data from the pump may include, for example, a current volumetric and mass flow through the pump, pump speed, and differential pressure, but is not limited thereto. Using the data from the pump 110, the controller 160 monitors the pump 110 to ensure that the measured volumetric and mass flow is the same as a desired, predetermined volumetric and mass flow (SI 02). Information of the desired, predetermined volumetric and mass flow may be stored in the controller, for example, in the memory 302. If the measured volumetric and mass flow is not the desired predetermined flow (S103-NO), the controller may controlthe pump 110 to alter the flow and / or may output information, for example in the form of an alert (SI 04). If the measured volumetric and mass flow matches the predetermined flow (S103-YES), the controller continues to receive data from and monitor the pump 110 (S105). Data from the heater 120 may include a current temperature and / or an operating power of the heater 120, as well as data from one or more thermocouples, such as temperature measurements at any of various locations within the heater 120. Using the data from the heater 120, the controller monitors the heater 120 to ensure that the measured temperature(s) are equal to desired temperature(s) predetermined to ensure that the refrigerant is heated to temperature higher than the boiling point of a first component, e.g. component A, of the refrigerant, and lower than the boiling point of a second component , e.g. component B, of the refrigerant (SI 06). Information of the desired temperature(s) may be stored in the controller, for example, in the memory 302. If the measured temperature(s) are not the desired predetermined temperature(s) (S107-NO), the controller 160 may control the heater 120 to alter the temperature and / or may output information, for example in the form of an alert (SI 08). If the measured temperature(s) match the predetermined temperature(s) (SI 07- YES), the controller continues to receive data from and monitor the heater 120 (S105).

[0055] The controller 160 may additionally monitor and control the valves 140, 150 by receiving data from the valves 140, 150, including, for example flow rates through the respective valves, analyze the data and thereby, for example, determine if the valves 140, 150 are operating properly and output a signal to control the valves 140, 150, or output information such as in the form of an alert.

[0056] FIG. 5 illustrates an example method of the second example function of the controller 160. The controller 160 receives data from the liquid level monitor 136 (S201). The data from the liquid level monitor 136 may include, but is not limited to, a height of the liquid in the tank 130, a relative change of the height of the liquid in the tank 130 ascompared to a predetermined height, and a rate of change over time of the height of the liquid in the tank 130. Based on the received data, the controller 160 monitors the liquid level over time (S202). A change of the liquid level over time is indicative of a change in the relative compositions of the components of the refrigerant, and thus, is indicative that there is a refrigerant leak. For example, an increase in the liquid level over time may indicate a leak in which a greater amount of component A (comprising the vapor present in the tank 130) is leaking, while a decrease in the liquid level over time may indicate a leak in which a greater amount of component B (comprising the liquid present in the tank 130) is leaking. If there is no leak, the pressure of the component A gas, PA, and the pressure of the component liquid, PB, should be the same and should remain constant. The monitoring may include comparing a change in the liquid level over time Ameas to a predetermined maximum deviation (S203). Information of the predetermined maximum deviation may be stored in the controller, for example, in the memory 302. If the change in the liquid level over time exceeds the predetermined maximum deviation Amax (S203-YES), this is an indication that there is a refrigerant leak, and the controller 160 outputs information, for example in the form of an alert (S205). If the change in the liquid level over time does not exceed the predetermined maximum deviation (S203-NO), the controller 160 continues to receive data and monitor the liquid level (S204). Measurement of the data by the liquid level monitor and receipt of this data by the controller 160 provides the controller with information not obtained with respect to related art leak detection systems, thus enabling the controller to obtain and monitor the liquid level over time. As noted, a memory of the controller may store information of the predetermined maximum desired deviation of the change of the liquid level over time, which is also information not stored in or provided to related art leak detection systems, thus enabling the controller to compare a change in the liquid level over time to the maximum desired deviation. As discussed above, a change in the liquid level over time that is greaterthan the maximum desired deviation provides an indication of a leak of the zeotropic refrigerant that is not dependent on the location of the leak, the position or sensitivity of external sensors, or external conditions, such as air flow.

[0057] FIG. 6 illustrates an example start-up method of the controller 160 of the system 100 according to an example embodiment. Assuming there is no system leak at start-up, at the initial start-up of the system 100, time will pass before the heater 120 is able to sufficiently heat the refrigerant to enable the liquid level in the tank 130 to reach a steady, substantially constant state. Thus, after initializing the system 100 by controlling the pump 110 to draw refrigerant into the system 100 and controlling the heater 120 to heat the refrigerant (S301), the controller 160 will receive data from one or more of the heater 120, the pump 110, and the liquid level monitor 136 (S302) and will determine whether a predetermined trigger has occurred (S303). The predetermined trigger may be, but is not limited to, one or more of: passage of a predetermined amount of time; an indication that the heater has reached a predetermined temperature or has maintained a predetermined temperature for a predetermined amount of time; and an indication that the liquid level has reached a predetermined level, or has maintained a constant level for a predetermined amount of time. The predetermined trigger may be stored in the controller, for example, in the memory 302. If the predetermined trigger has occurred (S303-YES), the controller 160 enters into a normal operating state (S305) in which is performs the operations, for example, of FIGs. 4 and 5. Until the predetermined trigger has occurred (S303-NO), the controller 160 remains in the start-up method (S304). The operations of the start-up method of FIG. 6 enable the controller to ensure that one or more of the pump, heater, and liquid level monitor reach a normal operating state such that subsequent monitoring and analysis of the liquid level, such as according to the operations of FIG. 5, are sufficiently relevant to a determination of a change in the respective properties of the constituent elements of the refrigerant, to indicate apotential leak, the detection of which is not dependent on the location of the leak, the position or sensitivity of external sensors, or external conditions, such as air flow.

[0058] The information output from the controller 160 in any one or more of operations (SI 04), (SI 08), and (S205) may be output to any of a variety of different apparatuses, including, but not limited to, an existing controller of the refrigeration circuit 10, an existing building or system controller (not shown), and a user interface which may be part of or directly connected to the controller 160, part of or directly connected to an existing controller of the refrigeration circuit 10, part of or directly connected to an existing building or system controller, or a separate user interface. A user interface to which the information is output may include one or more of a display screen, a speaker, and one or more visual outputs including, but not limited to light emitting diodes (LEDs). The information may all be output to a same apparatus or to different apparatuses.

[0059] The outputting may be executed via a hardware wired connection, or wirelessly.

[0060] According to another example embodiment, the leak detection system 100 may operate attached to a refrigeration circuit circulating a zeotropic refrigerant including greater than two constituent components. For example, a zeotropic refrigerant may comprise a first component X having a boiling point x’, a second component Y having a boiling point y’ higher than x’, and a third component Z having a boiling component z’ higher than y’. According to this example, the heater 120 may be controlled by the controller 160 to raise the temperature of the refrigerant to a temperature between the boiling point of component X and the boiling point of component Y, or may be controlled to raise the temperature of the refrigerant to a temperature between the boiling point of component Y and the boiling point of component Z. Thus, according to this example, a change over time of the liquid level in the tank 130 may indicate a leak in which one or two of the constituent components are leaking at a higher rate than the third component. As would be understood by one of skill in the art,the leak detection system 100 could be applied analogously to a refrigeration circuit circulating a zeotropic refrigerant comprising four or more constituent components, and the temperature to which the refrigerant is heated in the heater 120 may be determined based on the respective boiling points or other properties of the constituent components of the zeotropic refrigerant in order to provide the greatest change in the liquid level over time in the case of a leak.

[0061] FIG. 7 illustrates a leak detection system 200 according to another example embodiment. The system 200 is attached to a refrigeration circuit such as the example refrigeration circuit 10 illustrated in FIG. 1, and may be connected on a line 60 between the condenser 30 and the expansion valve 40. As with the previous example embodiments, in this example embodiment, the refrigerant a zeotropic refrigerant including a first component A with a boiling point a’ and a second component B with a boiling point b’, where the boiling point a’ is lower than the boiling point b’. The refrigerant may be, for example R454B, where R32 is component A and R1234yf is component B, but is not limited thereto. As would be understood by one of skill in the art, however, the refrigerant may alternately be a zeotropic refrigerant including three or more constituent components.

[0062] According to this example embodiment, a pressure drop across a heater 220 is monitored. The system 200 includes a pump 210 that draws an amount of refrigerant from the liquid line 60. Similarly to the pump 110, the pump 210 may be, for example, a pump with a power of 100 watts (W) or less, but is not limited thereto. A controller 260, is also communicatively and operatively coupled to the pump 210 and controls the pump 210. The pump 210 directs the refrigerant to a heater 220 which is also communicatively and operatively coupled to the controller 260. The heater 220 may comprise a coil tube through which the refrigerant passes and a heating element configured to heat the coil tube. The heater 220 may, for example, heat the refrigerant to a temperature between the boiling pointof the first constituent component of the refrigerant and the boiling point of the second constituent component of the refrigerant. A first pressure tap 280A and a second pressure tap 280B are coupled to a line 270 before and after the heater 220, respectively, to measure a pressure drop across the heater 220. The pressure taps 280A, 280B are communicatively and operatively coupled to the controller 260 and can thereby output to the controller 260 measurements of the pressures in the line 170 before and after the heater 220 and / or can directly output a pressure change across the heater 220.

[0063] As the composition of the overall refrigerant mixture changes with a leak, more vapor will be produced relative to liquid, which will be evident as an elevated pressure drop across the heater 220. Thus, if more vapor is produced relative to liquid, there will be a greater pressure drop across the heater 220, indicative of a leak. As the pressure drop across the heater 220 is a function of velocity squared, monitoring this pressure drop provides a greater sensitivity in determining whether a leak is present than related art methods including the above-described related art utilizing external sensors.

[0064] The controller 260 according to this example embodiment may be any controller as discussed above with respect to the controller 160.

[0065] A first example function of the controller 260 is to monitor and control the various elements of the system 200, including the pump 210 and the heater 220 to ensure that they are functioning properly and that the refrigerant is accurately drawn into the system 200 and heated by the heater 220. FIG. 4, discussed above, illustrates an example method of this first example function of the controller 260.

[0066] The controller 260 may additionally monitor and control the pressure taps 280A, 280B by receiving data from the pressure taps 280A, 280B, analyzing the received data, and outputting a signal to control the pressure taps 280 A, 280B.

[0067] A second example function of the controller 260 is to use data from the pressure taps 280A, 280B to determine if there is a refrigerant leak. FIG. 8 illustrates an example method of the second example function of the controller 260. The controller 260 receives data from the pressure taps 280A, 280B (S401). The received data may include a first pressure Pi measured on the line before the heater 220 and a second pressure P2 measured on the line after the heater 220. Based on the received data, the controller monitors a pressure drop A across the heater over time (S402). An increase in the pressure drop is indicative of a change in the relative compositions of the components of the refrigerant, and thus, is indicative that there is a refrigerant leak. If there is no leak, the pressure drop should remain constant. The monitoring may include comparing a measured pressure drop across the heater 220 Ameas to a predetermined maximum pressure drop Amax (S403). Information of the predetermined maximum pressure drop Amax may be stored in the controller, for example, in the memory. If the measured pressure drop exceeds the predetermined maximum (S403- YES), the controller 260 outputs information, for example in the form of an alert (S405). If the pressure drop does not exceed the predetermined maximum (S403-NO), the controller 260 continues to receive data and to monitor the pressure (S404). Measurement of the data by the pressure taps and receipt of this data by the controller 260 provides the controller with information not obtained with respect to related art leak detection systems, thus enabling the controller to obtain and monitor the pressure drop across the heater 220 over time. As noted, a memory of the controller may store information of the predetermined maximum pressure drop, which is also information not stored in or provided to related art leak detection systems, thus enabling the controller to compare a change in the pressure drop over time to the maximum desired pressure drop. As discussed above, a change in the pressure drop over time that is greater than the predetermined maximum provides an indication of a leak of thezeotropic refrigerant that is not dependent on the location of the leak, the position or sensitivity of external sensors, or external conditions, such as air flow.

[0068] As with the controller 160 of the previous example embodiment, FIG. 6 also illustrates a start-up method applicable to the controller 260. With respect to the controller 260, the predetermined trigger may be, but is not limited to, one or more of: passage of a predetermined amount of time; an indication that the heater 220 has reached a predetermined temperature or has maintained a predetermined temperature for a predetermined amount of time; an indication that the first pressure has reached a predetermined level, or has maintained a constant level for a predetermined amount of time; and an indication that the pressure drop has reached a predetermined drop, or has remained constant for a predetermined amount of time. After exiting the tank 130 or the heater 220, the refrigerant may have an increased temperature and lower pressure re-entering the refrigeration circuit 10 on the line 60 between the condenser 30 and the expansion valve 40 than it did when tapped from the line 60. However, this effect may be relatively small as compared to an overall capacity and may have only a negligible effect on cooling performance and overall efficiency of the refrigeration circuit 10.

[0069] The information output by the controller 260 in operations (SI 04), (SI 08), and (S405) may be any information as discussed hereinabove.

[0070] According to another example embodiment, the leak detection system 200 may operate attached to a refrigeration circuit circulating a zeotropic refrigerant comprising greater than two constituent components. In such an example, the heater 220 may be controlled to heat the refrigerant to a temperature between the respective boiling points of two constituent components of the refrigerant, in a manner analogous to that discussed hereinabove.

[0071] It is to be appreciated that this disclosure can be implemented with various operating systems or combinations of operating systems. It is also to be appreciated that this disclosure can be implemented as software stored as a program module in system memory or on disk or other removable storage.

[0072] The controller(s) 160, 260 can operate in a networked environment using logical connections to one or more remote computers. The remote computer(s) can includes one or more of a personal computer, a server, a router, a network PC, a workstation, a microprocessor based appliance, a peer device and another other common network node and the like, and typically include many or all of the elements described relative to a computer. Remote computer(s) may be logically connected to the controllers 160, 260 through a network interface and then physically connected via a communication connection, or may be connected via one or more wired connections. A network interface may include wired and / or wireless communication networks such as local-area networks (LAN), wide-area networks (WAN), cellular networks, etc. LAN technologies include Fiber Distributed Data Interface (FDDI) Copper Distributed Data Interface (CDDI), Ethernet, Token Ring and the like. WAN technologies include, but are not limited to, point-to-point links, circuit switching networks like Integrated Services Digital Networks (ISDN) and variations thereon, packet switching networks, and Digital Subscriber Lines (DSL).

[0073] Communication connect! on(s) refer to the hardware / software employed to connect the network interface to the controllers 160, 260, for example to a bus therein. While communication connect! on(s) may be inside the controllers 160, 260, they can also be external to the controllers 160, 260. The hardware / software necessary for connection to a network interface may include, for example purposes only, internal and external technologies such as, modems including regular telephone grade modems, cable modems and DSL modems, ISDN adapters, and Ethernet cards.

[0074] It may be understood that the example embodiments described herein may be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each example embodiment may be considered as available for other similar features or aspects in other example embodiments.

[0075] While example embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.

Claims

CLAIMSWhat is claimed is:

1. A leak detection system comprising: a heater configured to receive a refrigerant from an input line and to heat the refrigerant and thereby output a first constituent component of the refrigerant in a vapor state and output a second constituent component of the refrigerant in a liquid state; a tank which receives the first constituent component and the second constituent component output from the heater and holds therein the first constituent component in the vapor state and the second constituent component in the liquid state; a first valve which controls passage of the first constituent component in the vapor state from the tank to an output line; a second valve which controls passage of the second constituent component in the liquid state from the tank to the output line; a liquid level monitor which senses a liquid level in the tank and outputs data; a controller, coupled to the liquid level monitor, which receives the data from the liquid level monitor, determines whether a sensed change in the liquid level is greater than a predetermined level change, and outputs information indicating a potential refrigerant leak if the sensed change in the liquid level is greater than the predetermined level change.

2. The leak detection system of claim 1, further comprising: a pump which taps the refrigerant from a line in a refrigeration circuit and directs the refrigerant to the input line.

3. The leak detection system of claim 1, further comprising: at least one heat sensor, disposed within the heater, which outputs temperature data;wherein the controller is further coupled to the at least one heat sensor and to the heater, receives the temperature data from the at least one heat sensor, and controls the heater to heat the refrigerant to a temperature between a boiling point of the first constituent component and a boiling point of the second constituent component.

4. A leak detection system comprising: a heater configured to heat a refrigerant provided from an input line and thereby output, on an output line, a first constituent component of the refrigerant in a vapor state and a second constituent component of the refrigerant in a liquid state; a first pressure tap, disposed on the input line, which senses a pressure of the refrigerant and outputs first pressure data; a second pressure tap, disposed on the output line, which senses a pressure of the refrigerant and outputs second pressure data; a controller, coupled to the first pressure tap and to the second pressure tap, which receives the first pressure data and the second pressure data, determines whether a sensed change in pressure between the first pressure and the second pressure is greater than a predetermined pressure change, and outputs information indicating a potential refrigerant leak if the sensed change in the pressure is greater than the predetermined pressure change.

5. The leak detection system of claim 4, further comprising: a pump which taps the refrigerant from a line in a refrigeration circuit and directs the refrigerant to the input line.

6. The leak detection system of claim 4, further comprising: at least one heat sensor, disposed within the heater, which outputs temperature data;wherein the controller is further coupled to the at least one heat sensor and to the heater, receives the temperature data from the at least one heat sensor, and controls the heater to heat the refrigerant to a temperature between a boiling point of the first constituent component and a boiling point of the second constituent component.

7. A refrigeration circuit comprising: a compressor, a condenser, an expansion valve, and an evaporator; a line transmitting zeotropic refrigerant through the refrigeration circuit; the leak detection system of claim 1; and a pump, which taps the zeotropic refrigerant from the line of the refrigeration circuit and directs the zeotropic refrigerant to the input line.

8. A refrigeration circuit comprising: a compressor, a condenser, an expansion valve, and an evaporator; a line transmitting zeotropic refrigerant through the refrigeration circuit; the leak detection system of claim 4; and a pump, which taps the zeotropic refrigerant from the line of the refrigeration circuit and directs the zeotropic refrigerant to the input line.

9. A leak detection method comprising: tapping refrigerant from a line in a refrigeration circuit; heating the refrigerant to a temperature between a boiling point of a first constituent component of the refrigerant and a boiling point of a second constituent component of the refrigerant;holding, in a tank, the first constituent component in a vapor state and the second constituent component in a liquid state; controlling output from the tank of the first constituent component in the vapor state and the second constituent component in the liquid state; sensing a liquid level within the tank; determining whether a sensed change in the liquid level is greater than a predetermined level change; and outputting information indicating a potential refrigerant leak if the sensed change in the liquid level is greater than the predetermined level change.

10. A leak detection method comprising: tapping refrigerant from a line in a refrigeration circuit; heating the refrigerant to a temperature between a boiling point of a first constituent component of the refrigerant and a boiling point of a second constituent component of the refrigerant; sensing a first pressure of the refrigerant before the heating; sensing a second pressure of the refrigerant after the heating; determining whether a sensed pressure change between the first pressure and the second pressure is greater than a predetermined pressure change; and outputting information indicating a potential refrigerant leak if the sensed pressure change is greater than the predetermined pressure change.

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