Liquid detection system

The present disclosure relates to a sensor disposed in a conduit on a suction side of a compressor, wherein the conduit is configured to convey a fluid and a controller communicatively coupled to the sensor. The controller includes a processor and a memory, the memory is configured to store instructions to be performed by the processor, and the controller is configured to receive one or more indications from the sensor of an amount of power consumed by an active sensor component, determine a presence of liquid in the fluid based at least on the one or more indications, and control a device based on the presence of liquid in the fluid.

BACKGROUND

The present disclosure relates generally to a liquid detection system. Specifically, the present disclosure relates to a liquid detection system for a refrigeration system.

Refrigerants are used to transfer heat between fluids and may be employed in a variety of applications, such as heating, ventilating, air conditioning, and refrigeration (HVAC&R) systems, heat pumps, or power generation in Organic Rankine Cycles (ORC). The refrigerant is typically transported within a refrigerant piping system, which includes pipes, pipe fittings, valves, and the like. The refrigerant piping system transports the refrigerant between various vessels and equipment within the HVAC&R system, such as compressors, turbines, pumps, evaporators, condensers, and the like. The refrigerant may undergo one or more phase changes within the refrigerant piping system, and thus, liquid refrigerant and vaporous refrigerant may be present in the HVAC&R system simultaneously (e.g., either in the same location or in different locations). In some cases, it may be desirable for the refrigerant to be substantially saturated (e.g., substantially all liquid or substantially all vapor) at certain locations in the system.

DETAILED DESCRIPTION

The present disclosure is directed to an improved liquid detection system that may be configured to determine a presence of liquid in a conduit (e.g., a quantitative value or a qualitative indication of the presence of liquid), such that operating parameters of a process may be adjusted based on the detected liquid. In certain applications, it may not be desirable for liquid to be present in certain locations of a system that include a vaporous working fluid. Thus, detecting liquid (e.g., a quantitative value or a qualitative indication of the presence of liquid) in such locations of the system may enable an operator and/or a control system to adjust one or more operating parameters to reduce the presence of liquid at a given location. As a non-limiting example, refrigeration systems may include a cycle that causes a refrigerant to undergo one or more phase changes (e.g., from liquid to gas and/or from gas to liquid). Some components of a refrigeration system (e.g., a compressor) may operate with a higher efficiency (e.g., at a higher capacity) when the refrigerant is in a substantially saturated phase (e.g., at least 99% liquid or at least 99% vapor). Therefore, it may be desirable to detect the presence of liquid in conduits that may be designed to carry substantially saturated vapor.

For example, a refrigeration system may include a vapor compression refrigeration cycle (e.g., a chiller). Traditionally, a vapor compression refrigeration cycle (e.g., a chiller) may include a compressor that circulates refrigerant through the cycle, an evaporator to vaporize (e.g., transfer heat toward) the refrigerant prior to entering the compressor, a condenser to liquefy (e.g., condense and/or transfer heat away from) the refrigerant upon exiting the compressor, and/or an expansion valve to further cool the refrigerant before entering the evaporator. Because liquids are generally incompressible, it may be desirable for the refrigerant to be substantially saturated vapor when the refrigerant enters the compressor. For example, liquid that enters the compressor through a suction side of the compressor may cause components to wear (e.g., erode), wash oil away from bearings in the compressor, and/or add load to the compressor, thereby causing the system and/or the compressor to operate at a reduced efficiency.

Traditionally, baffles and/or mesh screens may be positioned in a vessel or a conduit to block liquid from entering into the compressor. However, baffles and/or mesh screens may still allow liquid to reach the compressor when operating the system at high capacities (e.g., increased flow rates through the components of the system). Operating a vapor compression refrigeration cycle at relatively high capacities may increase a risk of introducing liquid into the compressor because an evaporator may not be sized to manage the refrigerant at high flow rates (e.g., the evaporator spaces may not be sized to maintain proper velocities of the refrigerant, such that liquid may remain in the vapor stream). Traditional systems may measure a temperature and a pressure of refrigerant entering and/or exiting the compressor to determine a phase composition (e.g., an amount of liquid and/or vapor) of the refrigerant. For example, a temperature and a pressure measurement may be utilized to determine a phase composition of the refrigerant utilizing a phase diagram. However, such measurements and calculations may be inaccurate as a result of engineering tolerances (e.g., transition time) associated with temperature sensors and/or pressure sensors. Accordingly, it is now recognized that utilizing a thermal flow sensor to determine a presence of liquid in predetermined locations of a system is desired. In accordance with embodiments of the present disclosure, operating parameters of the system may be adjusted to reduce a presence of liquid at the predetermined location based on the liquid detected by the thermal flow sensor (e.g., a quantitative value of the liquid present or a qualitative indication of the presence of liquid).

Turning now to the figures,FIG. 1depicts an application for a refrigeration system. Such systems, in general, may be applied in a range of settings, both within the heating, ventilating, air conditioning, and refrigeration (HVAC&R) field and outside of that field. The refrigeration systems may provide cooling to data centers, electrical devices, freezers, coolers, or other environments through vapor-compression refrigeration, absorption refrigeration, and/or thermoelectric cooling. In presently contemplated applications, however, refrigeration systems may also be used in residential, commercial, light industrial, industrial, and in any other application for heating or cooling a volume or enclosure, such as a residence, building, structure, and so forth. Moreover, the refrigeration systems may be used in industrial applications, where appropriate, for basic refrigeration and heating of various fluids.

FIG. 1illustrates one application, in this case a heating, ventilating, air conditioning, and refrigeration system (HVAC&R) for building environmental management that may employ one or more heat exchangers. For example, a building10is cooled by a system that includes a refrigeration system12and a boiler14. As shown, the refrigeration system12is disposed on the roof of the building10and the boiler14is located in the basement; however, the refrigeration system12and the boiler14may be located in other equipment rooms or areas of the building10. The refrigeration system12is an air cooled device and/or a mechanical cooling system (e.g., a vapor compression refrigeration cycle or chiller) that implements a refrigeration cycle to cool water (or another cooling fluid, such as glycol). The refrigeration system12is housed within a single structure that may include a mechanical cooling circuit, a free cooling system, and associated equipment such as pumps, valves, and piping. For example, the refrigeration system12may be single package rooftop unit that incorporates a free cooling system and a mechanical cooling system. The boiler14is a closed vessel that includes a furnace to heat water. The water (or another cooling fluid) from the refrigeration system12and the boiler14is circulated through the building10by water conduits16. The water conduits16are routed to air handlers18, located on individual floors and within sections of building10.

The air handlers18are coupled to ductwork20that is adapted to distribute air between the air handlers18and may receive air from an outside intake (not shown). The air handlers18include heat exchangers that circulate cold water from the refrigeration system12and hot water from the boiler14to provide heated or cooled air. Fans, within the air handlers18, draw air across coils of the heat exchangers and direct the conditioned air to environments within the building10, such as rooms, apartments, or offices, to maintain the environments at a designated temperature. A control device, shown here as including a thermostat22, may be used to designate the temperature of the conditioned air. The control device22may also be used to control the flow of air through and from the air handlers18. Other devices may, of course, be included in the system, such as control valves that regulate the flow of water and pressure and/or temperature transducers or switches that sense the temperatures and pressures of the water, the air, and so forth. Moreover, the control devices may include computer systems that are integrated with and/or separate from other building control or monitoring systems, including systems that are remote from the building10. It should be noted that while water is discussed as a cooling fluid, any suitable cooling fluid may be utilized in the refrigeration system12.

As discussed above, it may be desirable to detect a presence of liquid at predetermined locations of a system, such as the refrigeration system12(e.g., a chiller). Some components of the refrigeration system12may operate at reduced efficiency when liquid is present in a stream of fluid that enters such components. For example, a compressor40of a vapor compression refrigeration cycle42(e.g., at least a portion of the refrigeration system12) may operate at a reduced efficiency when liquid droplets are present within a suction side44of the compressor40, as shown inFIG. 2.FIG. 2is a schematic of the vapor compression refrigeration42that includes an improved liquid detection system46. While the present discussion focuses on utilizing the liquid detection system46in refrigeration systems, it should be noted that the liquid detection system46may be utilized in any system where detection of liquid at a predetermined location is desired.

As shown in the illustrated embodiment ofFIG. 2, the vapor compression refrigeration cycle42includes the compressor40, an evaporator48, a condenser50, and/or an expansion valve52. Refrigerant54may flow through the vapor compression refrigeration cycle42and undergo one or more phase transitions (e.g., from vapor to liquid or vice versa). For example, substantially vaporous refrigerant54(e.g., at least 90% of the refrigerant54is in the vapor phase) from the compressor40may be cooled and condensed into substantially liquid refrigerant54(e.g., at least 90% of the refrigerant54is in the liquid phase) in the condenser50. In certain embodiments, the condenser50may be configured to transfer heat away from the refrigerant54and toward a cooling fluid92(e.g., a heat transfer fluid, water and/or air). Accordingly, a temperature of the refrigerant54may decrease, thereby causing at least a portion of the refrigerant54to transition from the vapor phase to the liquid phase. The substantially liquid refrigerant54may be further cooled in the expansion valve52. For example, a pressure of the refrigerant54flowing through the expansion valve52may rapidly decrease as a result of a pressure drop through the expansion valve52. As the pressure of the refrigerant54decreases, the temperature of the refrigerant54may also decrease. Accordingly, substantially liquid refrigerant54may flow toward the evaporator48.

The refrigerant54may be substantially vaporized (e.g., at least 90% of the refrigerant54is in the vapor phase) in the evaporator48. In certain embodiments, heat may be transferred to the refrigerant54(e.g., from a heat transfer medium90or heat transfer fluid) in the evaporator48, thereby causing the refrigerant54to transition from a liquid phase to the vapor phase. The substantially vaporized refrigerant54may flow towards the suction side44(e.g., a low pressure side) of the compressor40from the evaporator48. The compressor40may increase a pressure of the substantially vaporized refrigerant54, which in some cases, may cause a temperature of the substantially vaporized refrigerant54to increase. The substantially vaporized refrigerant54may exit the compressor40on a discharge side58(e.g., a high pressure side) and be directed toward the condenser50where the cycle may continue (e.g., repeat). As discussed above, liquid present in the suction side44of the compressor40may reduce an operating efficiency of the compressor40. Accordingly, the liquid detection system46may be disposed in a conduit60on the suction side44of the compressor40, such that an operator and/or a control system62may detect a presence of liquid entering the compressor40.

In certain embodiments, the liquid detection system46may include a sensor64and the control system62. For example, the sensor64may be disposed within the conduit60and configured to contact the refrigerant54flowing from the evaporator48and toward the compressor40. In some embodiments, the sensor64may extend between approximately 0.1 inches and 1.5 inches, between approximately 0.5 inches and 1.4 inches, or between approximately 0.75 inches and 1.25 inches into the conduit60. In other embodiments, the sensor64may extend any suitable distance into the conduit60, such that the sensor64contacts the refrigerant54flowing through the conduit60. In some embodiments, the sensor64may be disposed in the conduit60via an opening65. The opening65may include a threaded fitting such that the sensor64may be fastened to the opening65, thereby blocking the refrigerant54from leaking out of the conduit60through the opening65. In other embodiments, the sensor64may be disposed in the conduit60using any suitable technique that enables the sensor64to contact the refrigerant54flowing through the conduit60and to block the refrigerant54from inadvertently exiting the conduit60.

The sensor64may send one or more signals to the control system62, which may adjust one or more operating parameters of the vapor compression refrigeration cycle42to reduce a presence of liquid in the conduit60. The control system62may include memory circuitry66(e.g., memory) and a processor68. For example, the control system62may include non-transitory code or instructions stored in a machine-readable medium (e.g., the memory66) that is used by a processor (e.g., the processor68) to implement the techniques disclosed herein. The memory66may store computer instructions that may be executed by the processor68. Additionally, the memory66may store experimental data and/or other values (e.g., threshold values) relating to operating conditions of the vapor compression refrigeration cycle42.

In accordance with embodiments of the present disclosure, the sensor64may include a thermal flow sensor. Thermal flow sensors are traditionally utilized to determine a flow rate of fluid through a conduit. Thermal flow sensors may include a temperature sensor and/or a tip portion70(e.g., a distal end) that includes a heating element configured to sense changes in a heat transfer coefficient of fluid within a conduit. For example, power may be consumed by the tip portion70(e.g., the heating element), such that the heating element reaches a predetermined temperature (e.g., a set point). The thermal flow sensor may monitor an amount of power consumed by the heating element to maintain the temperature at the predetermined temperature (e.g., via an internal voltage meter or another suitable device). Thus, as flow changes in the conduit60, the amount of power consumed by the heating element may also change (e.g., as flow increases, more power may be consumed, and as flow decreases, less power may be consumed), thereby enabling the thermal flow sensor (or a control device) to determine the flow rate of fluid within the conduit60. In other words, the amount of power consumed by the heating element (of the tip portion70) may be indicative of the flow rate of fluid through the conduit60. In other embodiments, the sensor64may determine a difference in temperature between a location near the heating element and a location remote from the heating element in the tip portion70. As heat transfer to the fluid increases, the sensor64may detect a temperature differential proportional to the flow rate of fluid through the conduit60.

Moreover, it is now recognized that thermal flow sensors may be utilized to detect liquid and/or measure an amount of liquid present in a conduit (e.g., conduit60) of a potential two-phase refrigerant. For example, the tip portion70(e.g., the heating element) of the thermal flow sensor may incur a large power demand (and thus consumes more power) and/or an internal temperature differential in the tip portion70may increase when liquid refrigerant54contacts the sensor64because liquid cools the heating element more than vapor (e.g., a latent heat capacity for converting saturated liquid refrigerant54to vapor is substantially greater than a sensible heat capacity of the vaporous refrigerant). Accordingly, the sensor64may send one or more indications to the control system62related to an amount of power consumed by the tip portion70(e.g., the heating element) of the sensor64(e.g., determined by an internal voltage meter or another suitable device) or a temperature differential in the tip portion70. Accordingly, the control system62may detect a presence of liquid in the conduit60(or the fluid) based at least on the amount of power consumed by the tip portion70(e.g., the heating element) and/or the internal temperature differential in the tip portion70(e.g., a location near the heat element versus a location remote from the heating element along the tip portion) received as proportional outputs from the sensor64. Accordingly, the control system62may adjust operating parameters of the vapor compression refrigeration cycle42in response to the detection of liquid in the conduit60(or fluid).

For example, the control system62may be configured to send a signal to the evaporator48to adjust an amount of heat transfer medium90(e.g., heat transfer fluid) supplied to the evaporator48based on the presence of liquid in the conduit60. In certain embodiments, when the sensor64detects a presence of liquid above a threshold (e.g., a threshold value or a predetermined sensor response stored in the memory66of the control system62), the control system62may send a signal to the evaporator48to increase a flow of the heat transfer medium90, thereby increasing an amount of vaporization in the evaporator48(e.g., increasing heat transfer). In other embodiments, the control system62may send a signal to the evaporator48when the control system62receives a predetermined response from the thermal flow sensor64(e.g., significant power fluctuations or spikes). Additionally, the control system62may send a signal to the condenser50to decrease a flow of cooling fluid92(e.g., a flow of heat transfer fluid) to the condenser50, such that a temperature of the refrigerant54exiting the condenser50is increased. The control system62may also send a signal to the compressor40to decrease a speed of the compressor40(e.g., adjust an amount of power supplied to a prime mover of the compressor40), thereby decreasing a flow rate of the refrigerant54through the vapor compression refrigeration cycle42. In still further embodiments, the control system62may be configured to send a signal to the expansion device52to adjust a flow rate of the refrigerant54through the expansion device52. For example, when the presence of liquid in the conduit60exceeds the threshold, the control system62may reduce the flow rate of the refrigerant54through the expansion device52, thereby reducing a volume of the refrigerant54in the evaporator48.

In some embodiments, the suction side44of the compressor40may include additional components, as shown inFIG. 3. For example,FIG. 3is an expanded schematic of the suction side44of the vapor compression refrigeration cycle42ofFIG. 2. As shown in the illustrated embodiment ofFIG. 3, the suction side44may include a capacity control device80(e.g., an inlet guide vane) located upstream of the compressor40. However, in other embodiments, the capacity control device80may be downstream of the compressor40. The capacity control device80may include an actuator82that adjusts a position of the capacity control device80(e.g., inlet guide vanes) to control an amount of refrigerant54that flows through the compressor40. In some embodiments, the capacity control device80and/or the actuator82may be coupled to the control system62. Accordingly, when the sensor64sends a signal to the control system62related to a presence of liquid in the conduit60, the control system62may send a resultant signal to the capacity control device80and/or the actuator82. For example, when the sensor64detects a presence of liquid in the conduit60above a threshold (e.g., a quantitative value or a predetermined response of the sensor64), the control system62may direct the capacity control device80to limit a flow of the refrigerant54toward the compressor40(e.g., instruct the capacity control device80to close). Accordingly, the flow rate of the refrigerant54through the vapor compression refrigeration cycle42may decrease, which may ultimately lead to a reduction in liquid in the conduit60(e.g., the velocity of the refrigerant through the evaporator48is below a threshold velocity, thereby blocking liquid entrainment in the vaporous refrigerant54).

Additionally, the compressor40may be coupled to the control system62. For example, the compressor40may include a prime mover84(e.g., a motor) configured to adjust a speed of the compressor40, and thus, a pressure of the refrigerant54on the discharge side58of the compressor40. In some embodiments, the control system62may send one or more signals to the prime mover84to adjust a speed of the compressor40based on a presence of liquid in the conduit60. For example, when the presence of liquid in the conduit60exceeds the threshold (e.g., a threshold value and/or a predetermined response from the sensor64), the control system62may instruct the prime mover84to decrease a speed of the compressor40, thereby reducing a flow rate of the refrigerant54through the vapor compression refrigeration cycle42. Accordingly, the presence of liquid in the conduit60may be reduced because a velocity of the refrigerant54through the evaporator48is below a threshold velocity, thereby blocking liquid entrainment in the vaporous refrigerant54. Adjustments to the speed of the compressor40(e.g., via the prime mover84) may be made simultaneously with, or in lieu of, adjustments made to the capacity control device80.

In certain embodiments, the control system62may be coupled to an indicator86(e.g., a display, a light emitting diode (LED), a light bulb, a speaker, or another suitable indicator) that alerts an operator when the liquid in the conduit60exceeds a threshold. In response, the operator may take action to adjust one or more operating parameters of the vapor compression refrigeration cycle42to reduce the presence of liquid in the conduit60. For example, the vapor compression refrigeration cycle42may include one or more valves and/or controls that may be manually adjusted (e.g., the one or more valves and/or controls may also be adjusted by the control system62). Accordingly, the operator may manually adjust operating parameters of the vapor compression refrigeration cycle42when the indicator86notifies the operator that the liquid present in the conduit60exceeds the threshold.

In any case, the control system62may be configured to determine a presence of liquid in the conduit60and/or adjust one or more operating parameters to reduce the presence of liquid in the conduit60based on the detection of liquid in the conduit60. For example,FIG. 4is a block diagram of a process100that may be utilized to adjust (e.g., reduce) the presence of liquid in the conduit60. At block102, the control system62may receive one or more indications from the sensor64. As discussed above, the sensor64may be disposed in the conduit60on the suction side44of the compressor40, which is configured to convey the refrigerant54in a substantially vaporous phase (e.g., at least 90% vapor). Accordingly, it is now recognized that it may be desirable to detect the presence of liquid in the conduit60and adjust one or more operating parameters to reduce the presence of liquid in the conduit60, such that the compressor40may operate with enhanced capacity (e.g., reduce wear caused by liquid in the compressor40and/or reduce power consumption by removing liquid that reduces compressor performance).

At block104, the control system62(e.g., the processor68) may utilize the one or more indications received from the sensor64to detect a presence of liquid in the conduit60. For example, the sensor64may provide an indication to the control system62of an amount of power consumed by the tip portion70(e.g., heating element) of the sensor62over time and/or a temperature differential in the tip portion70. Accordingly, the control system62(e.g., the processor68) may utilize such data to determine a presence of liquid (e.g., a quantitative value or a qualitative indication of the presence of liquid) in the conduit60using algorithms stored in the memory66of the control system62.

At block106, the control system62(e.g., the processor68) may be configured to compare the presence of liquid in the conduit60determined using the indications from the sensor64to a predetermined threshold (e.g., a threshold value and/or a predetermined response received from the sensor64) stored in the memory66. For example, the predetermined threshold may be an amount of liquid that may reduce an efficiency of the compressor40beyond a predetermined limit (e.g., a limit specified by an original equipment manufacturer or supplier). In other embodiments, the predetermined threshold may be a qualitative indication of an amount of liquid that may reduce the efficiency of the compressor40beyond a predetermined limit. For example, the predetermined threshold may include a predetermined response (e.g., power supplied to the tip portion70of the sensor64) received from the sensor64indicative of the presence of liquid. The predetermined response may be a spike in the amount of power supplied to the tip portion70(e.g., the heating element) or a significant fluctuation in the amount of power supplied to the tip portion70.

At block108, when the liquid present in the conduit60exceeds the predetermined threshold, the control system62may adjust one or more operating parameters of the vapor compression refrigeration cycle42. For example, the control system62may be configured to send one or more signals to the compressor40, the evaporator48, the condenser50, and/or the capacity control device80to adjust an operating parameter of the compressor40(e.g., a speed of the compressor via the prime mover84), the evaporator48(e.g., a flow rate of the heat transfer medium90or the heat transfer fluid), and/or the condenser50(e.g., a flow rate of the cooling fluid92or heat transfer fluid), such that the liquid present in the conduit60is reduced. Additionally or alternatively, the control system62may be configured to send a signal to the indicator86to signal to an operator that the liquid present in the conduit60exceeds the threshold. Accordingly, the operator may adjust a valve and/or other control device to reduce the liquid present in the conduit60.

One or more of the disclosed embodiments, alone or in combination, may provide one or more technical effects useful in enhancing detection of liquid in a conduit. In general, embodiments of the present disclosure include an enhanced liquid detection system46that may include a sensor64(e.g., a thermal flow sensor) electrically coupled to a control system62. The sensor64may send a signal to the control system62related to a presence of liquid in a conduit60. The control system62may determine a presence of liquid in the conduit60and send one or more signals to components of the system42to adjust one or more operating parameters, such that the liquid present in the conduit60is reduced. The technical effects and technical problems in the specification are exemplary and are not limiting. It should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems.