Patent Description:
Buildings, such as commercial buildings including university buildings, office buildings, hospitals, restaurants and residential buildings such as single family, multiple family and high rise residential, and the like, include refrigeration systems which are operable to control the climate inside the building. A typical refrigeration system includes an evaporator, and indoor circulation fan, one or more compressors, a condenser, an expansion valve and a control system. This system and components utilize circulating refrigerant to maintain an indoor temperature of the building at a desired level.

Traditionally, refrigeration systems have used A1 refrigerants, which are non-flammable. However, global warming and other environmental concerns have caused the heating, ventilation, and air conditioning (HVAC) industry to explore alternative low Global Warming Potential (GWP) refrigerants, such as A2L refrigerants, in place of existing A1 refrigerants in HVAC systems. Many low GWP refrigerants are mixtures. Although these alternative refrigerants have a lower GWP, they are often are mildly flammable. <CIT> discloses a method for a refrigeration system and a refrigeration system according to the preamble of claim <NUM> and claim <NUM>, respectively.

According to a first aspect of the present invention, there is provided a method for a refrigeration system as defined in claim <NUM> and comprises measuring a pressure of fluid in a refrigerant line of a heat exchanger of a refrigeration system, and measuring a value of at least one of a dewpoint temperature and a bubble point temperature of the fluid at the measured temperature. The method also includes determining an expected value associated with said at least one of the dewpoint temperature and the bubble point temperature of the fluid at the measured pressure, and determining whether the fluid includes a correct refrigerant composition based on a comparison of the measured and expected values. The refrigeration system includes an indoor heat exchanger and an outdoor heat exchanger, and the method includes determining an ambient temperature of each of the indoor heat exchanger and the outdoor heat exchanger, and selecting whichever of the indoor heat exchanger and outdoor heat exchanger has a lower ambient temperature as the heat exchanger.

In a further embodiment of any of the foregoing embodiments, the measuring steps are performed while a compressor of the refrigeration system is turned off.

In a further embodiment of any of the foregoing embodiments, prior to the measuring steps and while the compressor is turned off, a fan is operated, for a predefined time period, to pass air through the heat exchanger having the lower ambient temperature.

In a further embodiment of any of the foregoing embodiments, determining whether the fluid has a correct refrigerant composition includes determining a difference between the measured value of and expected value associated with each of at least one of the dewpoint temperature and the bubble point temperature. The method also includes determining that the fluid represents a correct refrigerant composition based on each difference being within a predefined error threshold, and determining that the fluid does not represent the correct refrigerant composition based on at least one of the differences being greater than the predefined error threshold.

In a further embodiment of any of the foregoing embodiments, determining that the fluid does not represent the correct refrigerant includes determining that the fluid has an incorrect refrigerant or contaminated refrigerant.

In a further embodiment of any of the foregoing embodiments, the at least one of the dewpoint temperature and the bubble point temperature includes a single one of the dewpoint temperature and the bubble point temperature, and each difference includes a single difference.

In a further embodiment of any of the foregoing embodiments, the at least one of the dewpoint temperature and the bubble point temperature includes each of the dewpoint temperature and the bubble point temperature, and each difference includes a dewpoint difference and a bubble point difference.

In a further embodiment of any of the foregoing embodiments, determining an expected value includes determining an expected glide of the fluid at the measured pressure based on a difference between the expected dewpoint and bubble point temperatures. The determination of whether the fluid has a correct refrigerant composition includes determining an actual glide of the fluid based on a difference between the measured dewpoint and bubble point temperatures, determining that the fluid represents a correct refrigerant composition based on a glide difference between the expected glide and actual glide being within a predefined error threshold, and determining that the fluid does not represent the correct refrigerant composition based on the glide difference being greater than the predefined error threshold.

In a further embodiment of any of the foregoing embodiments, the correct refrigerant composition includes a correct mixture of multiple constituent fluids.

According to a second aspect of the present invention, there is provided a refrigeration system as defined in claim <NUM> and includes a heat exchanger configured to exchange heat with fluid in a refrigerant line, a pressure sensor configured to measure a pressure of the fluid, at least one temperature sensor configured to measure a temperature of the fluid. A controller is configured to utilize the at least one temperature sensor to measure a value of at least one of a dewpoint temperature and a bubble point temperature of the fluid at the measured pressure, determine an expected value associated with said at least one of the dewpoint temperature and the bubble point temperature of the fluid at the measured pressure, and determine whether the fluid includes a correct refrigerant composition based on a comparison of the measured and expected values. The refrigeration system includes an indoor heat exchanger and an outdoor heat exchanger each operable to exchange heat with the fluid in the refrigerant line. The controller is configured to determine an ambient temperature of each of the indoor heat exchanger and the outdoor heat exchanger, and select whichever of the indoor heat exchanger and outdoor heat exchanger has a lower ambient temperature as the heat exchanger.

In a further embodiment of any of the foregoing embodiments, a compressor is configured to compress the fluid in the refrigerant line, and the controller is configured to perform the comparison based on readings from the pressure sensor and at least one temperature sensor taken when the compressor is turned off.

In a further embodiment of any of the foregoing embodiments, the controller is configured to operate a fan to pass air through the heat exchanger for a predefined time period prior to obtaining the readings from the pressure sensor and at least one temperature sensor.

In a further embodiment of any of the foregoing embodiments, to determine whether the fluid has a correct refrigerant composition, the controller is configured to determine a difference between the measured value of and expected value associated with each of at least one of the dewpoint temperature and the bubble point temperature, determine that the fluid represents a correct refrigerant composition based on each difference being within a predefined error threshold, and determine that the fluid does not represent the correct refrigerant composition based on at least one of the differences being greater than the predefined error threshold.

In a further embodiment of any of the foregoing embodiments, to determine that the fluid does not represent the correct refrigerant, the controller is configured to determine that the fluid includes an incorrect refrigerant or contaminated refrigerant.

In a further embodiment of any of the foregoing embodiments, the at least one of the dewpoint temperature and the bubble point temperature includes each of the dewpoint temperature and the bubble point temperature, and a single difference includes a dewpoint difference and a bubble point difference.

In a further embodiment of any of the foregoing embodiments, to determine the expected value, the controller is configured to determine an expected glide of the fluid at the measured pressure based on a difference between the expected dewpoint and bubble point temperatures. To determine whether the fluid includes a correct refrigerant composition, the controller is configured to determine an actual glide of the fluid based on a difference between the measured dewpoint and bubble point temperatures, determine that the fluid represents a correct refrigerant composition based on a glide difference between the actual and expected glide being within a predefined error threshold, and determine that the fluid does not represent the correct refrigerant composition based on the glide difference being greater than the predefined error threshold.

The embodiments, examples, and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

<FIG> is a schematic view of an example refrigeration system 20A that includes a compressor 22A, a first heat exchanger 24A, an expansion device 26A, and a second heat exchanger 28A. Refrigerant in a suction line <NUM> is compressed in the compressor 22A, and exits the compressor 22A at a high pressure, high temperature, and a high enthalpy, and flows to the first heat exchanger 24A. Although only a single compressor 22A is shown, it is understood that multiple compressors could be used.

In a cooling operation, the first heat exchanger 24A operates as a condenser that rejects heat. In the first heat exchanger 24A, refrigerant flows through one or more coil tubes 30A and rejects heat to air that is drawn over the coil tube(s) 30A by a blower fan 32A. In the first heat exchanger 24A, refrigerant is condensed into a liquid that exits the first heat exchanger 24A at a low enthalpy and a high pressure. The heat rejection medium could be water in a shell and tube arrangement, for example.

The refrigerant flows from the first heat exchanger 24A to the expansion device 26A, such as a thermostatic expansion valve or electronic expansion valve. The expansion valve <NUM> reduces the refrigerant to a low pressure and temperature. After expansion, the refrigerant flows through the second heat exchanger 28A, which operates as an evaporator that accepts heat. A blower fan 34A (which may be a centrifugal fan) draws air through the second heat exchanger 28A and over a coil 36A. The refrigerant flowing through the coil 36A accepts heat from air, exiting the second heat exchanger 28A at a high enthalpy and a low pressure. The refrigerant then flows to the compressor 22A, completing its refrigeration cycle. The cooling medium could be air or could be water in a shell and tube arrangement, for example.

A controller 38A controls operation of each of the compressor 22A, fan 32A, and fan 34A and operates each of these components during a heat exchange mode when the refrigeration system 20A is running. In the heat exchange mode, the refrigeration system 20A is operated to cool and dehumidify air. In embodiments utilizing an electronic expansion valve for the expansion device 26A, the controller 38A could also control the expansion device 26A, and operate the expansion device 26A in the heat exchange mode.

Each heat exchanger 24A, 28A has an associated pressure sensor <NUM>, first temperature sensor <NUM>, and second temperature sensor <NUM>, that are in communication with the controller 38A, and will be discussed in greater detail below.

<FIG> illustrates another type of refrigeration system, which is a heat pump 20B, capable of operating in both cooling and heating modes. The heat pump 20B includes a compressor 22B that delivers refrigerant through a discharge port <NUM> that is returned back to the compressor 22B through a suction port <NUM>. Although only a single compressor 22B is shown, it is understood that multiple compressors could be used.

Refrigerant moves through a four-way valve <NUM> that can be switched between heating and cooling positions to direct the refrigerant flow in a desired manner (indicated by the arrows associated with valve <NUM> in <FIG>) depending upon the requested mode of operation, as is well known in the art. When the valve <NUM> is positioned in the cooling position, refrigerant flows from the discharge port <NUM> through the valve <NUM> to an outdoor heat exchanger 24B, which includes a coil 30B, and where heat from the compressed refrigerant is rejected to a secondary fluid, such as ambient air. A fan 32B is used to provide airflow through the outdoor heat exchanger 24B.

The refrigerant flows from the outdoor heat exchanger 24B through a first fluid passage <NUM> into an expansion device 26B, which can be a thermostatic expansion valve or electronic expansion valve, for example. The refrigerant when flowing in this forward direction expands as it moves from the first fluid passage <NUM> to a second fluid passage <NUM> thereby reducing its pressure and temperature. The expanded refrigerant flows through an indoor heat exchanger 28B, which includes a coil 36B, to accept heat from another secondary fluid and supply cold air indoors. A fan 34B (which may be a centrifugal fan) provides air flow through the heat exchanger 28B. The refrigerant returns from the indoor exchanger 28B to the suction port <NUM> through the valve <NUM>.

When the valve <NUM> is in the heating position, refrigerant flows from the discharge port <NUM> through the valve <NUM> to the indoor heat exchanger 28B where heat is rejected to the indoors. The refrigerant flows from the indoor heat exchanger 28B through second fluid passage <NUM> to the expansion device 26B. As the refrigerant flows in this reverse direction from the second fluid passage <NUM> through the expansion device 26B to the first fluid passage <NUM>, the refrigerant flow is more restricted in this direction as compared to the forward direction. The refrigerant flows from the first fluid passage <NUM> through the outdoor heat exchanger 24B, four-way valve <NUM> and back to the suction port <NUM> through the valve <NUM>.

A controller 38B controls operation of each of the compressor 22B, fan <NUM>, fan 34B, and valve <NUM> when the heat pump 20B is operating in a heating or cooling mode. In embodiments utilizing an electronic expansion valve for the expansion device 26B, the controller 38B would also control the expansion device 26B while the heat pump 20B is operating in a heating or cooling mode.

Although not shown in <FIG>, it is understood that each heat exchanger 24B, 28B could also include the pressure sensor <NUM> and temperature sensors <NUM>, <NUM> of <FIG>.

The refrigeration system <NUM> can be used in a number of applications, such as a split system residential or commercial unit or a packaged residential or commercial rooftop. When used with a split system, the heat exchanger <NUM> is located inside a residence or building and the fan <NUM> draws air through the heat exchanger <NUM>. Also, when used in the split system, the heat exchanger <NUM> is located outside the residence or building.

When used with a packaged unit the refrigeration system <NUM> is located on a rooftop or an exterior of a building. In this configuration, the refrigeration system <NUM> includes an evaporator section that draws air from inside the building and conditions it with the heat exchanger <NUM> and directs the air back into the building. Additionally, the refrigeration system <NUM> for the rooftop application would include an outdoor section with the fan <NUM> drawing ambient air through the heat exchanger <NUM> to remove heat from the heat exchanger <NUM> as described above.

<FIG> is a schematic view of an example heat exchanger <NUM> which may be used as either of the heat exchangers <NUM> or <NUM>. The heat exchanger <NUM> includes a coil <NUM> that provides a flow of refrigerant from an inlet <NUM> to an outlet <NUM>. A fan <NUM> is configured to provide airflow across the coil <NUM>, and facilitate a heat exchange with the coil <NUM>. A plurality of fins <NUM> increase a surface area of the heat exchange <NUM> for maximizing heat exchange.

The pressure sensor <NUM> (e.g., a pressure transducer) is operable to measure a pressure of refrigerant entering the coil <NUM>. Although depicted within the inlet <NUM>, it is understood that other locations could be utilized (e.g., outside but in proximity to the inlet <NUM>). The first temperature sensor <NUM> is configured to measure a dewpoint temperature of the refrigerant at or near the top of the coil. Dewpoint temperature refers to a temperature below which refrigerant droplets begin to condense.

The second temperature sensor <NUM> is configured to measure a bubble point temperature of the refrigerant at or near the bottom of the coil and where liquid refrigerant has condensed. Bubble point temperature refers to a temperature at which all or substantially all refrigerant has condensed to liquid. The sensors <NUM> and <NUM> are at or proximate to a top of the coil <NUM>, and the sensor <NUM> is at or proximate to a bottom of the coil <NUM>.

<FIG> illustrates an example temperature vs. enthalpy diagram for a refrigerant mixture. A liquid line <NUM> is depicted on the left hand side of the curve <NUM>, and a vapor line <NUM> is depicted on a right hand side of the curve <NUM>. Line segment A-B indicates a decreased temperature as refrigerant flows though the heat exchanger <NUM> which serves as the condenser. Line segment B-C represents a change in enthalpy as refrigerant passes through the expansion device <NUM>. Line segment C-D represents refrigerant passing through the heat exchanger <NUM> which operates as an evaporator.

Point A represents a dewpoint of the heat exchanger <NUM>, and point B represents a bubble point of the heat exchanger <NUM>. Similarly, point D represents a dewpoint of the heat exchanger <NUM>, and point C represents a bubble point of the heat exchanger <NUM>. As shown in <FIG>, the line segments A-B and C-D have non-zero slopes, which indicate that the refrigerant is a refrigerant mixture having a "glide" in each of the heat exchangers <NUM>, <NUM>. The glide of each heat exchanger <NUM>, <NUM> can be calculated based on a difference between its dewpoint temperature and bubble point temperature, using equation <NUM> below. <MAT> where:.

For refrigerants that utilize a single constituent fluid type (i.e., a non-mixture refrigerant), the glide is expected to be zero, within a margin of error. However, for refrigerant mixtures, the glide is often expected to be non-zero as the constituent fluids likely have different condensation properties as well as boil points.

The controller <NUM> is operable to detect whether a correct refrigerant composition is being utilized based on the dewpoint temperature, the bubble point temperature, and/or the "glide" of the refrigerant. The controller <NUM> is configured to measure a pressure of fluid in a refrigerant line of a heat exchanger of the refrigeration system <NUM> using pressure sensor <NUM>, and measure a value of at least one of a dewpoint temperature and a bubble point temperature of the fluid at the measured temperature. The controller <NUM> is further configured to determine an expected value associated with the at least one of the dewpoint temperature and the bubble point temperature of the fluid at the measured pressure (e.g., an expected dewpoint temperature, expected bubble point temperature, or expected glide), and determine whether the fluid includes a correct refrigerant composition based on a comparison of the measured and expected values.

If a difference between an expected and measured glide values exceeds a corresponding predefined threshold that is indicative of an incorrect refrigerant mixture which includes an incorrect ratio of refrigerants, possibly due to leakage. If a difference between expected and measured dewpoint values or expected and measured bubble point temperatures exceeds a corresponding predefined threshold, that is indicative of an incorrect refrigerant composition due to an incorrect refrigerant being used and/or due to an otherwise correct refrigerant being contaminated (e.g., by non-condensable air or nitrogen).

The expected dewpoint temperature and expected bubble point temperatures can be determined by utilizing the measured pressure (e.g., with a temperature lookup table stored in the controller <NUM>).

<FIG> is a flowchart illustrating an example method <NUM> for a refrigeration system <NUM> for detecting whether an incorrect refrigerant mixture is present. The controller is configured to compare an indoor ambient temperature T_indoor and an outdoor ambient temperature T_outdoor, and determine which is lower (step <NUM>). Whichever of the indoor heat exchanger (e.g., heat exchanger <NUM>) and outdoor heat exchanger (e.g., heat exchanger <NUM>) has a lower ambient temperature is selected as the heat exchanger for subsequent steps.

Thus, if the outdoor ambient temperature is lower than the indoor ambient temperature (a "yes" to step <NUM>), the outdoor heat exchanger (e.g., heat exchanger <NUM>) is selected for a diagnostic test (step <NUM>). Otherwise, if the indoor ambient temperature is lower than the outdoor ambient temperature (a "no" to step <NUM>), the indoor heat exchanger (e.g., heat exchanger <NUM>) is selected for the diagnostic test (step <NUM>).

The fan associated with the selected heat exchanger is run for a predefined time period while the compressor <NUM> is off (step <NUM>), which helps to migrate refrigerant into the coil of the selected heat exchanger, including both liquid and vapor refrigerant, such that the heat exchanger has liquid at the bottom and vapor at the top of its coil, which enables the measuring the of dew point and bubble point temperatures. The compressor being off enables looking at the conditions of the refrigerant while there is substantially no flow and substantially no heat transfer, which is an advantageous time to measure the liquid bubble point temperature and vapor bubble point temperature at the top and bottom of the coil.

While the compressor <NUM> is off, the controller <NUM> measures the refrigerant pressure using pressure sensor <NUM>, measures the dewpoint and bubble point temperatures using the temperature sensors <NUM>, <NUM> at the measured pressure, and determines a glide based on the difference (step <NUM>).

Based on the measured pressure, the controller <NUM> determines expected values for the dewpoint temperature, bubble point temperature, and glide (e.g., using a repository of stored values in a lookup table) (step <NUM>).

The controller <NUM> calculates an error between the measured and expected glide values (step <NUM>). This may be calculated using equation <NUM> below, for example.

If a magnitude of the error is within an allowable tolerance by being less than a predefined threshold (a "yes" to step <NUM>), the controller <NUM> determines that the refrigerant mixture is correct (step <NUM>). Otherwise, if a magnitude of the error is outside an allowable tolerance by being greater than a predefined threshold (a "no" to step <NUM>), the controller <NUM> determines that the refrigerant mixture is incorrect, and includes an incorrect ratio of constituent refrigerants (step <NUM>).

<FIG> is a flowchart illustrating example method <NUM> for a refrigeration system <NUM> for detecting whether an incorrect refrigerant is present. Steps <NUM>-<NUM> of <FIG> are the same as steps <NUM>-<NUM> of <FIG>.

Having running the fan in step <NUM>, the controller <NUM> measures the refrigerant pressure using pressure sensor <NUM> and also measures one or both of the dewpoint temperature and bubble point temperature while the compressor <NUM> is off (step <NUM>).

Based on the measured pressure, the controller <NUM> determines expected values for the dewpoint temperature and/or the bubble point temperature (e.g., using a repository of stored values in a lookup table) (step <NUM>).

The controller <NUM> calculates an error between the measured and expected dewpoint temperature and/or determines an error between the measured and expected bubble point temperature (step <NUM>). These calculations can be performed using equations <NUM> and <NUM> below, for example. <MAT> where:.

If a magnitude of the error value(s) are within a respective allowable tolerance by being less than a respective predefined threshold (a "yes" to step <NUM>), the controller <NUM> determines that the correct refrigerant is in use (step <NUM>). If a magnitude of either error value is outside a respective allowable tolerance by being greater than a respective predefined threshold (a "no" to step <NUM>), the controller <NUM> determines that the refrigerant is wrong or contaminated (step <NUM>). The refrigerant at issue in step <NUM> could be a single refrigerant (i.e., a non-mixture), or could be a refrigerant mixture.

The controller can make the determination of step <NUM> using only a dew point temperature error, only a bubble point temperature error, or both of the dew point and bubble point temperature errors.

The allowable tolerances used in steps <NUM> and <NUM> would depend on the refrigerant being used.

<FIG> is a schematic view of a controller <NUM> that can be used as either of the controllers 38A-B. The controller <NUM> includes a processor <NUM> that is operatively connected to memory <NUM> and a communication interface <NUM>. The processor <NUM> may include one or more microprocessors, microcontrollers, application specific integrated circuits (ASICs), or the like, for example.

The memory <NUM> can include any one or combination of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, VRAM, etc.)) and/or nonvolatile memory elements (e.g., ROM, hard drive, tape, CD-ROM, etc.). The memory <NUM> can also have a distributed architecture, where various components are situated remotely from one another, but can be accessed by the processor <NUM>. The memory <NUM> could be used to store the expected dewpoint, bubble point, and/or glide values for the refrigeration system <NUM> at a plurality of different pressures.

The communication interface <NUM> is configured to facilitate communication between the controller <NUM> and some or all of the compressor <NUM>, fans <NUM> and/or <NUM>, and expansion device <NUM> (if it is an electronic device), pressure sensor <NUM>, and temperature sensors <NUM>, <NUM>. In one example, multiple controllers <NUM> are included (e.g., one controller for general operation of the refrigeration system <NUM> in the heat exchanging mode, and one controller for performing the methods <NUM> and/or <NUM>). In one example, the communication interface <NUM> includes a wireless interface for wireless communication and/or a wired interface for wired communications.

Claim 1:
A method (<NUM>) for a refrigeration system (<NUM>), comprising:
measuring (<NUM>) a pressure of fluid in a refrigerant line of a heat exchanger (<NUM>; <NUM>) of a refrigeration system;
measuring (<NUM>; <NUM>) a value of at least one of a dewpoint temperature and a bubble point temperature of the fluid at the measured pressure;
determining (<NUM>; <NUM>) an expected value associated with said at least one of the dewpoint temperature and the bubble point temperature of the fluid at the measured pressure; and
determining (<NUM>; <NUM>) whether the fluid includes a correct refrigerant composition based on a comparison of the measured and expected values,
wherein
the refrigeration system includes an indoor heat exchanger (<NUM>) and an outdoor heat exchanger (<NUM>), characterised by
the method comprising:
determining (<NUM>; <NUM>) an ambient temperature of each of the indoor heat exchanger and the outdoor heat exchanger; and
selecting (<NUM>, <NUM>; <NUM>, <NUM>) whichever of the indoor heat exchanger and outdoor heat exchanger has a lower ambient temperature as the heat exchanger.