Heat transfer apparatus with moisture detection

Abstract

In one aspect, a heat transfer apparatus including a heat transfer medium, a liquid distribution system, a fan, and a liquid sensor of the heat transfer medium. The liquid sensor includes a sensing zone configured to detect an electrical transport property that is indicative of a wetness of the heat transfer medium. The sensing zone includes a first plurality of electrode extensions and a second plurality of electrode extensions that mesh with and are spaced apart from the first plurality of electrode extensions. A controller is operably connected to the liquid distribution system and the liquid sensor, the controller configured to operate the liquid distribution system based at least in part on the electrical transport property to achieve a target wetness level of the heat transfer medium.

Description

Docket No. 21067-163053 (BAC236-US)HEAT TRANSFER APPARATUS WITH MOISTURE DETECTIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 736,974, filed December 20, 2024, which is hereby incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] This disclosure relates generally to heat transfer apparatuses and, more specifically, relates to moisture detection systems for heat transfer apparatuses.BACKGROUND

[0003] Heat transfer apparatuses, such as cooling towers, may include a liquid distribution system that distributes liquid during operation of the cooling tower. For example, the cooling tower may include adiabatic pads. The liquid distribution system distributes liquid to the adiabatic pads to soak the adiabatic pads and cool the air entering the cooling tower through the adiabatic pads. As another example, the liquid distribution system may distribute liquid onto a heat exchanger, such as fill or a serpentine coil heat exchanger. Distributing the liquid evenly over the adiabatic pads and / or heat exchanger generally improves the efficiency of the cooling tower during operation. However, oversaturation of the adiabatic pads can result in excess liquid consumption because more liquid is being distributed to the adiabatic pads than is needed for efficient adiabatic cooling of the air flowing through the adiabatic pads.

[0004] Further, the dispensing openings of the liquid distribution system (e.g., nozzles) may become clogged overtime (e.g., due to dirt accumulation or scaling) such that the dispensing openings do not distribute the liquid evenly. Further, the adiabatic pads may develop localized airflow obstructions over time due to clogging of the openings of the adiabatic pads, pad cell damage, or debris accumulation on the exterior of the adiabatic pads as some examples. The localized airflow obstructions result in some regions of the adiabatic pads becoming oversaturated while other regions remain dry. The uneven wetness of the adiabatic pads reduces the efficiency of the adiabatic pads.Docket No. 21067-163053 (BAC236-US)BRIEF DESCRIPTION OF DRAWINGS

[0005] FIG. 1 is a schematic view of a cooling tower having liquid sensors at adiabatic pads;

[0006] FIG. 2 is a side view of the cooling tower of FIG. 1;

[0007] FIG. 3 is a perspective view of an adiabatic pad of the cooling tower of FIG. 1 with a liquid sensor at a side of the adiabatic pad;

[0008] FIG. 4 is a schematic view of the liquid sensor of FIG. 3 having multiple sensing zones;

[0009] FIG. 5A is a schematic view of a sensing zone of the liquid sensor of FIG. 4 according to a first embodiment, FIG. 5A showing the electrodes in the sensing zone extending along the length of the liquid sensor;

[0010] FIG. 5B is a schematic view of a sensing zone of the liquid sensor of FIG. 4 according to a second embodiment, FIG. 5B showing the sensing zone with a smaller gap between the electrodes;

[0011] FIG. 5C is a schematic view of a sensing zone of the liquid sensor of FIG. 4 according to a third embodiment, FIG. 5C showing the electrodes in the sensing zone extending across a width the water sensor;

[0012] FIG. 6 is a flow diagram of a method of operating the cooling tower of FIG. 1 using the liquid sensor to achieve a target air saturation efficiency;

[0013] FIG. 7A is a perspective view of an adiabatic pad having a liquid sensor extending along a length of the adiabatic pad;

[0014] FIG. 7B is an example graph of test data illustrating a correlation between adiabatic pad saturation efficiency and wetness data of the liquid sensor of FIG. 7A;

[0015] FIG. 8 is a perspective view of an adiabatic pad having liquid sensors extending across a width of the adiabatic pad;

[0016] FIG. 9 is a perspective view of an adiabatic pad with liquid sensors extending around edges of the adiabatic pad;

[0017] FIG. 10 is a perspective view of an adiabatic pad with a liquid sensor covering an end surface of the adiabatic pad;

[0018] FIG. 11 is a perspective view of an adiabatic pad with a liquid sensor extending in the adiabatic pad;Docket No. 21067-163053 (BAC236-US)

[0019] FIG. 12 is a perspective view of an adiabatic pad having electrodes of liquid sensors printed on surfaces of the adiabatic pad;

[0020] FIG. 13 is a perspective view of a liquid distribution system and adiabatic pad, FIG. 13 showing a liquid sensor below the liquid distribution system;

[0021] FIG. 14 is a flow diagram of a method of operating the cooling tower of FIG. 1 based on detection of moisture distribution in an adiabatic pad according to an embodiment;

[0022] FIG. 15 is a flow diagram of a method of operating the cooling tower of FIG. 1 based on detection of moisture distribution in an adiabatic pad according to another embodiment;

[0023] FIG. 16 is a flow diagram of a method of operating the cooling tower of FIG. 1 based on detected changes of liquid distributed in the cooling tower according to an embodiment;

[0024] FIG. 17 is a flow diagram of a method of operating the cooling tower of FIG. 1 based on detected changes of liquid distributed in the cooling tower according to another embodiment;

[0025] FIG. 18 is a perspective view of a liquid sensor on a drain surface of adiabatic pads of the cooling tower of FIG. 1;

[0026] FIG. 19 is an elevational view of a pair of adiabatic pads with portions of the pads removed to show a liquid sensor on a fin-and-tube heat exchanger behind the adiabatic pads;

[0027] FIG. 20A is a perspective view of a serpentine coil heat exchanger having liquid sensors on the serpentine coils;

[0028] FIG. 20B is a perspective view of a portion of one of the serpentine coils of the heat exchanger of FIG. 20A showing a liquid sensor on the coil;

[0029] FIG. 21 is a perspective view of a plate heat exchanger having a liquid sensor on a surface of the plate heat exchanger;

[0030] FIG. 22 is a perspective view a fill sheet having a liquid sensor with electrodes extending along a surface of the fill sheet;

[0031] FIG. 23 is a schematic view of a drift eliminator having liquid sensors;

[0032] FIG. 24 is a flow diagram of a method of detecting drift using the liquid sensors of the cooling tower of FIG. 1;Docket No. 21067-163053 (BAC236-US)

[0033] FIG. 25 is a perspective view illustrating a basin of the cooling tower of FIG. 1 having a liquid sensor in the basin;

[0034] FIG. 26 is a flow diagram of a method of controlling a fluid level in the basin of the cooling tower of FIG. 1 using liquid sensors; and

[0035] FIG. 27 is a flow diagram of a method of detecting moisture at moisture sensitive components of the cooling tower of FIG. 1 using liquid sensors.DETAILED DESCRIPTION

[0036] In one aspect of the present disclosure, a heat rejection apparatus is provided that includes a heat exchanger, a liquid distribution system, a heat transfer medium such as an adiabatic medium, a liquid sensor, an airflow generator, and a controller operatively connected to the liquid sensor and the liquid distribution system. The liquid distribution system is operable to distribute liquid to the adiabatic medium to wet the adiabatic medium including a portion of the adiabatic medium. The airflow generator is operable to cause air to flow through the adiabatic medium to the heat exchanger. The liquid sensor is capable of detecting a wetness level of a portion of the wetted portion of the adiabatic medium, the wetness level being one of a plurality of wetness levels capable of being detected by the liquid sensor. The wetness levels correspond to a range of liquid amounts that may be present in the wetted portion of the adiabatic medium.

[0037] The controller is configured to operate the heat rejection apparatus based at least in part on the wetness level of the portion of the adiabatic medium detected by the liquid sensor. In one aspect, the controller operates the liquid distribution system to achieve a desired adiabatic medium saturation efficiency (e.g., the efficiency of the adiabatic medium in saturating the air flowing through the adiabatic medium). For example, the controller turns the liquid distribution on (e.g., operates in a wet mode) or off (e.g. operates in a dry mode) based on the measured wetness level of the adiabatic medium to increase or decrease the wetness level of the adiabatic medium to achieve the desired adiabatic medium saturation efficiency. The wetness level of the portion of the adiabatic medium detected by the liquid sensor may correlate to the adiabatic medium saturation efficiency.

[0038] For example, the liquid sensor may include a first electrode and a second electrode and be configured to measure a resistance between the first electrode andDocket No. 21067-163053 (BAC236-US) second electrode. The resistance between the first electrode and second electrode varies based on the wetness of the portion of the adiabatic medium between the first electrode and second electrode. In one embodiment, the liquid sensor is capable of outputting data comprising an integerfrom 0 (indicating perfect conductance) to 1023 (indicating a lack of contact with a conductive substrate). In this manner, the liquid sensor outputs an integer of 1023 when the adiabatic medium location monitored by the sensor is dry and an integer in the range of about 600 to 800 when the adiabatic medium location is initially wetted. As the adiabatic medium portion monitored by the sensor becomes wetter, the resistance between the first and second electrodes decreases and the sensor outputs progressively lower integers until the adiabatic medium portion monitored by the sensor is saturated. The adiabatic medium may be saturated when the adiabatic medium provides a desired adiabatic medium saturation efficiency. The liquid sensor may monitor a portion of the adiabatic medium where the wetness data is indicative of the overall saturation efficiency of the adiabatic medium. When the adiabatic medium location is saturated, the sensor may output an integer in the range of about 300 to 400.

[0039] In another aspect, the liquid sensor detects the wetness level for a plurality of different portions of the adiabatic medium. In one embodiment, the liquid sensor has a plurality of sensing zones with each sensing zone associated with a different portion of the adiabatic medium. For example, each sensing zone has a first electrode and a second electrode and is configured to measure an electrical resistance between the first electrode and second electrode. The controller determines a wetness level for each sensing zone based upon the electrical resistance between the first and second electrodes of the sensing zone.

[0040] The controller compares the wetness levels for the plurality of different portions of the adiabatic medium to determine whether there is an even distribution of liquid in the adiabatic medium, for example, that liquid is being distributed evenly to the adiabatic medium from the liquid distribution system and / or that liquid is flowing uniformly through the adiabatic medium. Uneven distribution of liquid may indicate, for example, that the liquid distribution system is not distributing liquid evenly or that a portion of the adiabatic medium is clogged or broken. Where uneven distribution of liquid is detected, the controller outputs an alert for maintenanceDocket No. 21067-163053 (BAC236-US) and / or adjusts the distribution of liquid to the adiabatic medium (e.g., to cause more liquid to be distributed to the drier portion of the adiabatic medium).

[0041] In another approach, the controller compares the wetness level detected by the liquid sensor to historical data of the wetness levels at similar operating conditions. Upon determining that the wetness levels deviate from the historical data (e.g., by more than a threshold) the controller may determine that an abnormal condition is present. For example, the wetness levels may change due to gradual accumulation of dirt and / or scale that restricts the flow in the adiabatic medium and / or from a dispensing opening of the liquid distribution system. The sensor data may also change when the adiabatic medium or liquid distribution breaks, for example, when the pump of the liquid distribution system malfunctions. Where an abnormal condition is detected, the controller outputs an alert for maintenance and / or enters a self-cleaning mode to clear the liquid distribution system and / or adiabatic mediums from debris.

[0042] In another aspect, the heat rejection apparatus uses a liquid sensor to detect drift or plume of the cooling tower. For example, the heat rejection apparatus may include a liquid sensor mounted to a drift eliminator or a location downstream of a heat exchanger (e.g., in the plenum, at airflow generator) that detects wetness. The controller of the heat rejection apparatus may receive the sensor data of the liquid sensor and determine the presence and degree of drift and / or plume of the heat exchanger apparatus based on the detected wetness. The controller may adjust operation of the cooling tower to limit or reduce the drift or plume based on the wetness detected by the liquid sensor.

[0043] In another aspect, the heat rejection apparatus uses liquid sensors to detect the presence of moisture at moisture sensitive components. For example, the liquid sensor may be mounted at a moisture sensitive component (e.g., a control box of the heat rejection apparatus, a motor of the airflow generator, a coil of a heat exchanger). The controller may detect the presence of moisture at the moisture sensitive component by the liquid sensor detecting a wetness level. Where the wetness level at the moisture sensitive component exceeds a threshold, the controller may output an alert for maintenance and / or adjust operation of the heat rejection apparatus to limit or reduce the moisture reaching the moisture sensitive component.Docket No. 21067-163053 (BAC236-US)

[0044] In one aspect of the present disclosure, a heat rejection apparatus is provided that includes a direct heat exchanger such as fill, a process liquid distribution system, one or more liquid sensors, an airflow generator, and a controller. The process liquid distribution system is operable to distribute liquid to the fill. The airflow generator is operable to cause air to contact the process liquid distributed to the fill. The one or more liquid sensors are configured to detect a wetness level at one or more locations of the fill. The controller determines whether there is an abnormal flow condition in the fill based upon the wetness level at the one or more locations of the fill. For example, the controller may determine there is an abnormal flow condition of liquid in the fill when there is an uneven distribution of process liquid in the fill, for example, that process liquid is being distributed unevenly to the fill from the process liquid distribution system and / or that process liquid is flowing unevenly through the fill. In response to the controller determining there is an abnormal flow condition of liquid in the fill, the controller outputs an alert for maintenance and / or adjusts the distribution of liquid to the fill (e.g., to cause more liquid to be distributed to the drier portion of the fill).

[0045] Regarding FIG. 1, a heat rejection apparatus, such as a cooling tower 100, is provided. The cooling tower 100 has an outer structure 101 with an interior 103 housing components of the cooling tower 100. The cooling tower 100 has a process fluid inlet 105 to receive a process fluid, such as water or a glycol / water mixture, from a heat generating apparatus such as a chiller of a building, a computer datacenter, or another industrial process. The cooling tower 100 removes heat from the process fluid and returns cooled process fluid via a process fluid outlet 107. The cooling tower 100 is a closed-circuit cooling tower in FIG. 1 but may be an open cooling tower in another embodiment. The closed-circuit cooling tower may be operable in various modes such as dry, wet, hybrid (e.g., one side of the cooling tower 100 operating wet and the other side operating dry), and / or adiabatic modes.

[0046] The cooling tower 100 includes an airflow generator such as one or more fans 102 each including blades 104 and a motor 106. The fans 102 may be operated to cause air to flow through the cooling tower 100. The cooling tower 100 includes heat exchangers 110 through which process fluid may flow to exchange heat with the air flowing relative to the heat exchanger 110. The heat exchanger 110 may be an indirectDocket No. 21067-163053 (BAC236-US) heat exchanger such as a coil 112 (e.g., a fin-and-tube coil) that receives a process fluid (e.g., water or a combination of water and water vapor). The cooling tower 100, or the cooling system of which the cooling tower 100 is a part, may include a pump 109 that operates to cause process fluid to flow through the coil 112 from an inlet 128 to an outlet 130. The cooling tower 100 may include an evaporative liquid distribution system 122 to distribute an evaporative liquid (e.g., water) onto the coil 112 to exchange heat with the process fluid in the coil 112. The liquid distribution system 122 may include, for example, nozzles above the coil 112, piping, and a pump to direct the evaporative liquid from a sump or other receptacle of the cooling tower through the piping and to the nozzles.

[0047] The process fluid inside the coil 112 is separated from the air and / or evaporative liquid flowing about the coil 112. In other forms, the heat exchanger 110 is a plate heat exchanger (e.g., the plate heat exchanger of FIG. 21). In another embodiment, the heat exchanger 110 is a direct heat exchanger (e.g., the fill of FIG. 22) along which the process fluid (e.g., water) flows to exchange heat with air flowing relative to the fill.

[0048] With reference to FIG. 2, the cooling tower 100 includes an adiabatic medium, such as adiabatic pads 132, through which air travels before contacting the heat exchanger 110. The cooling tower 100 includes a liquid distribution system 108 to distribute liquid to the adiabatic pads 132. The liquid distribution system 108 includes a header 116 with one or more outlets, such as dispensing openings 118, through which liquid (e.g., water) is distributed onto the adiabatic pads 132, for example, to wet the adiabatic pads 132. The wetted adiabatic pads 132 cool the air flowing therethrough upstream of the heat exchanger 110 which permits the air to exchange (e.g., receive) more heat from the heat exchanger 110. Liquid flowing off of the adiabatic pads 132 is collected in receptacles such as trays 172 (e.g., when liquid is distributed onto wetted adiabatic pads 132 at a rate that exceeds the evaporation rate of the liquid from the adiabatic pads 132). In some embodiments, the liquid is recirculated from the trays 172 to the headers 116 and liquid is added to compensate for evaporated liquid. In other embodiments, the liquid is drained from the trays 172 and not reused.Docket No. 21067-163053 (BAC236-US)

[0049] As the process liquid flows through the heat exchanger 110, the fans 102 operate to cause airflow in the cooling tower 100 to contact the heat exchanger 110. Operation of the fans 102 moves airthrough the cooling tower 100 along airflow paths 120. The fans 102 draw air in through air inlets 124, through the adiabatic pads 132, across the heat exchanger 110, and outward from the cooling tower 100 via an air outlet 125. In the embodiment of FIG. 1, the air generally flows in a crossflow direction to the falling liquid distributed from the evaporative liquid distribution system 122. In other embodiments, the cooling tower 100 may have a counter-flow or parallel flow configuration as some examples.

[0050] The air flows relative to the heat exchanger 110 to remove heat from the heat exchanger 110 and thereby cool the process fluid in the heat exchanger 110. The cooled process fluid is directed back to the heat generating apparatus via the process fluid outlet 107. In one embodiment, motors 106 of the fans 102 are variable speed motors capable of rotating the blades 104 at varying speeds.

[0051] The cooling tower 100 includes one or more liquid sensors 134 of the adiabatic pads 132. The liquid sensors 134 are configured to measure a wetness level of the adiabatic pads 132. For example, the liquid sensor 134 may be configured to detect a degree of wetness of the adiabatic pad 132, e.g., an amount of liquid at the portion of the adiabatic pad 132 sensed by the liquid sensor 134. The wetness level may indicate an amount of moisture on the adiabatic pad 132 and / or a saturation level of the adiabatic pad 132. For instance, as discussed in further detail below, in one embodiment the liquid sensor 134 measures electrical conductivity at one or more portions of the adiabatic pad 132. The electrical conductivity increases as the moisture content of the adiabatic pad 132 increases and the electrical conductivity decreases as the moisture content of the adiabatic pad 132 decreases.

[0052] In one embodiment, the controller 136 utilizes the wetness level detected by the liquid sensors 134 to estimate a saturation efficiency of the adiabatic pads 132 in saturating the air flowing therethrough. The saturation efficiency indicates how effectively the adiabatic pad 132 is saturating the air passing through the adiabatic pad 132 by evaporating water into the air. The saturation efficiency may be calculated as the difference in the dry bulb temperature of the air entering the adiabatic pad 132 and the dry bulb temperature of the air exiting the adiabatic pad 132, the differenceDocket No. 21067-163053 (BAC236-US) divided by the wet bulb depression of the air entering the adiabatic pad 132. The entering wet bulb depression is the difference between the entering dry bulb air temperature and the entering wet bulb temperature. The liquid sensors 134 may be at various locations of the adiabatic pads 132 to measure a wetness at different locations of the adiabatic pads 132. The liquid sensors 134 may be at various locations of the adiabatic pads 132 to measure a wetness at different locations of the adiabatic pads 132. For example, the wetness level at different portions of an adiabatic pad 132 may be compared to determine whetherthe liquid is being distributed evenly overthe adiabatic pad 132 and / or whether the adiabatic pad 132 is wetted evenly.

[0053] The cooling tower 100 optionally includes one or more drift eliminators 126 in the section of the cooling tower 100 housing the heat exchanger 110 and / or upstream of the fans 102 (e.g., in the plenum 762). The drift eliminator(s) 126 inhibit drift from leaving the cooling tower 100.

[0054] The cooling tower 100 includes or is in communication with a controller 136 to control operation of the cooling tower 100. The controller 136 includes a processor 138 in communication with a memory 140. The processor 138 may execute programs and functions stored in the memory 140 to control operations of the cooling tower 100. The processor 138 may also execute programs and functions stored in the memory 140 to control other operations of the cooling tower 100 or another system, such as an HVAC system. The processor 138 may include, as examples, a microprocessor, an application-specific integrated circuit (ASIC), or a field programmable gate array (FPGA). The memory 140 may include, as examples, an electrical charge-based storage media such as EEPROM or RAM, ROM, or other non- transitory computer readable media such as a flash memory device or magnetic or optical storage medium. In some embodiments, the controller 136 is a controller of the cooling tower 100 configured to control the components of the cooling tower 100 such as e.g., the fan 102 and liquid distribution system 108. In some embodiments, the controller 136 is configured to communicate with a master controller of the HVAC system. In some embodiments, the controller 136 is the master controller of the building HVAC system and is configured to communicate with one or more cooling towers 100 to control operation of the cooling towers 100.Docket No. 21067-163053 (BAC236-US)

[0055] Regarding FIG. 3, an adiabatic pad 132 of the cooling tower 100 is shown having an adiabatic pad body 131 and a liquid sensor 134 associated with the adiabatic pad body 131. The adiabatic pad body 131 includes an inlet side 142 through which air enters and flows through the adiabatic pad 132 in direction 145. Liquid from the liquid distribution system 108 enters the adiabatic pad body 131 at an upper end portion 146 of the adiabatic pad body 131, travels through the adiabatic pad body 131 in direction 143, and exits the adiabatic pad body 131 at a lower end portion 147 of the adiabatic pad body 131.

[0056] The liquid sensor 134 is mounted to a side surface 144 of the adiabatic pad body 131. For example, the liquid sensor 134 may be secured to the adiabatic pad body 131with an adhesive. As another example, the liquid sensor 134 may be secured to the adiabatic pad body 131 with fasteners (e.g., bolts). As yet another example, the liquid sensor 134 may be integrated with, or mounted to, a frame supporting the adiabatic pad body 131.

[0057] The side surface 144 of the adiabatic pad body 131 may face a side surface of an adjacent adiabatic pad 132 when the adiabatic pads 132 are installed in the cooling tower 100. The liquid sensor 134 extends along a length 151 of the adiabatic pad body 131, for example, from the upper end portion 146 toward the lower end portion 147 of the adiabatic pad body 131. In other words, the liquid sensor 134 extends along the adiabatic pad body 131 in the direction 143 that the liquid flows through the adiabatic pad body 131 from the liquid distribution system 108.

[0058] Regarding FIG. 4, the liquid sensor 134 includes a control board 148 and an elongate sensor body 150 extending from the control board 148. The control board 148 may include a processor configured to receive measured wetness data from the sensor body 150. For example, the processor may measure a conductivity of an electrode circuit of the sensor body 150, interpret the measured conductivity, and reports conductivity changes to another device (e.g., controller 136) as serial data.

[0059] The control board 148 may be in communication with a computing device of the cooling tower 100, for example, the controller 136. In some embodiments, the control board 148 is configured to send sensor data to the controller 136 for processing. The control board 148 may receive a signal from the controller 136 that initiates data collection by the liquid sensor 134. The sensor body 150 has sensingDocket No. 21067-163053 (BAC236-US) zones 152 along the length of the sensor body 150. Each sensing zone 152 may be used to measure the wetness at the sensing zone 152. The control board 148 is configured to receive wetness data for each sensing zone 152 of the liquid sensor 134. The control board 148 may determine a resistance or conductivity value for each sensing zone and send the resistance or conductivity value to the controller 136. The liquid sensor 134 may thus be used to measure the wetness of the adiabatic pad body 131 at various locations along the adiabatic pad body 131, for example, along the length 151 of the adiabatic pad body 131.

[0060] Returning to FIG. 3, the liquid sensor 134 may include an adhesive between the sensor body 150 and the adiabatic pad body 131 to secure the liquid sensor 134 to the adiabatic pad body 131. In one embodiment, the sensing zones 152 are on the same side of the sensor body 150 as the adhesive to hold the sensing zones 152 against the adiabatic pad body 131 to measure the wetness of the adiabatic pad body 131. In another embodiment, the sensing zones 152 are on the side of the sensor body 150 opposite the adhesive. The liquid sensor 134 may be mounted to the side surface 144 of the adiabatic pad body 131 with the sensing zones 152 positioned to be in contact with the adjacent adiabatic pad 132 to measure the wetness of the adjacent adiabatic pad 132.

[0061] Regarding FIG. 5A, an enlarged, schematic view of a first embodiment of a sensing zone 152 of the liquid sensor 134 is provided. The liquid sensor 134 includes a first conductor such as first electrode 154 and a second conductor such as second electrode 156. In the first embodiment, the liquid sensor 134 is an interdigitated sensor where the first electrode 154 includes a plurality of electrode extensions 158 that mesh with and are spaced apart from a corresponding plurality of electrode extensions 160 of the second electrode 156. The first electrode 154 has a comb arrangement with a first bus 162 from which the plurality of electrode extensions 158 extend and the second electrode 156 has an opposing comb arrangement with a second bus 164 from which the plurality of electrode extensions 160 extend between the electrode extensions 158 of the first electrode 154. In the embodiment of FIG. 5A, the first bus 162 and second bus 164 extend substantially perpendicular (e.g., within 10 degrees) to a length 153 (see FIG. 4) of the sensor body 150 with the electrode extensions 158, 160 extending generally parallel to the length 153 of the sensor bodyDocket No. 21067-163053 (BAC236-US)150. In the embodiment of FIG. 5A, the first electrode 154 includes three electrode extensions 158 and the second electrode includes two electrode extensions 160. In other embodiments, the sensing zone 152 may include more or fewer first electrode extensions 158 and / or second electrode extensions 160. In each sensing zone 152, the first bus 162 of the first electrode 154 connects the electrode extensions 158 to a return conductor 155 that extends to the control board 148. The second bus 164 of the second electrode 156 connects the electrode extensions 160 to a signal conductor 157 that extends from the control board 148. The signal conductor 157 may be common to one or more of the sensing zones 152, for example, providing a voltage signal to multiple (e.g., all) of the sensing zones 152 of the liquid sensor 134.

[0062] In operation, the control board 148 outputs a voltage signal to the second electrode 156 at a known amperage and monitors the voltage of the first electrode 154. The voltage of the first electrode 154 varies based on the resistance between the first electrode 154 and second electrode 156, for example, between the electrode extensions 158 of the first electrode 154 and the electrode extensions 160 of the second electrode 156. The resistance between the first electrode 154 and second electrode 156 varies based on the wetness (e.g., the amount of liquid, such as water) between the first electrode 154 and second electrode 156. The wetness detected by the liquid sensor 134 corresponds to the amount of contact the electrodes 154, 156 have with the liquid between the electrodes 154, 156. Generally, the greater the amount of liquid between the electrodes 154, 156, the more contact between the electrodes 154, 156 and the liquid and the lower electrical resistance between the electrodes 154, 156. Conversely, the less liquid between the electrodes 154, 156, the less contact between the electrodes 154, 156 and the liquid and the higher the electrical resistance between the electrodes 154, 156. However, dirt or scaling in the adiabatic pad 132 can inhibit the amount of contact between the electrodes 154, 156 and the liquid between the electrodes 154, 156.

[0063] For example, the liquid includes ions of dissolved salts and metals that provide a conductive pathway through which electrical current is able to flow between the first electrode 154 and second electrode 156. The greater the amount of such liquid between the first electrode 154 and second electrode 156, the lower the resistance (and higher the electrical conductivity) is between the first electrode 154 and secondDocket No. 21067-163053 (BAC236-US) electrode 156. The lower the resistance (and higher the electrical conductivity) between the first electrode 154 and second electrode 156, the higher the voltage at the first electrode 154. Conversely, the higher the resistance (and lower electrical conductivity) is between the first electrode 154 and second electrode 156, the lower the voltage at the first electrode 154.

[0064] The voltage of the first electrode 154 thereby correlates to the wetness at the sensing zone 152. The control board 148 measures the voltage at the first electrode 154and calculates the electrical conductivity and / or electrical resistance between the first electrode 154 and second electrode 156 which indicates the wetness level of the material (e.g., a portion of the adiabatic pad body 131) between the first electrode 154 and second electrode 156. The control board 148 (or a processor in communication with the control board 148 such as processor 138) thereby uses the data of the sensing zone 152 to determine a wetness characteristic at the sensing zone 152, for example, a wetness level of the adiabatic pad body 131 adjacent the sensing zone 152. The liquid sensor 134 outputs sensor data (e.g., values such as values of 0- 1023) for each sensing zone 152 that indicates the measured conductivity at the sensing zone 152 and provides a scaled measurement of the wetness level at the measured portion of the adiabatic pad body 131. For instance, an output of 0 indicates no electrical resistance and an output of 1023 indicates infinite electrical resistance. The wetter the sensing zone 152, the lower the measured electrical resistance and thus the lower the value output by the liquid sensor 134 for the sensing zone 152. Conversely, the drier the sensing zone 152, the higher the measured electrical resistance and thus the higher the value output by the liquid sensor 134 for the sensing zone 152.

[0065] Regarding FIG. 5B, an enlarged, schematic view of a sensing zone 166 that may be used in the liquid sensor 134 is shown. The sensing zone 166 is similar to the sensing zone 152 such that similar reference numerals will be utilized for similar components. Specifically, the first electrode 154 of the sensing zone 166 has nine electrode extensions 158 extending from the first bus 162 and the second electrode 156 has eight electrode extensions 160 extending from the second bus 164. Additionally, in the sensing zone 166, the space 168 between the opposing electrode extensions 158, 160 of the first electrode 154 and second electrode 156 is smaller than in the sensingDocket No. 21067-163053 (BAC236-US) zone 152. Reducing the space 168 between the first electrode 154 and second electrode 156 may make the liquid sensor 134 more sensitive to lower levels of wetness.

[0066] Regarding FIG. 50, an enlarged, schematic view of a sensing zone 170 that may be used in the liquid sensor 134 is shown. The sensing zone 170 is similarto the sensing zones 152, 166 such that similar reference numerals will be used for similar components. In the sensing zone 170, the first bus 162 and second bus 164 extend generally parallel to the length of the sensor body 150 with the electrode extensions 158, 160 extending substantially perpendicular (e.g., within 10 degrees) to the length of the sensor body 150. The orientation of the electrode extensions 158, 160 of the first and second electrodes 154, 156 relative to the length of the sensor body 150 may be selected based on the orientation of the sensor body 150 on the adiabatic pad body 131. For example, where the sensor body 150 extends vertically along a height of the adiabatic pad body 131, having the electrode extensions 158, 160 extend horizontally and generally perpendicular to the length of the sensor body 150 may provide a different sensor output in response to a wetness that varies along a height of the adiabatic pad body 131 than in sensing zones 152, 166. For example, the sensor data for a sensing zone 170 oriented so that the electrode extensions 158, 160 extend horizontally on an adiabatic pad body 131 will change incrementally as liquid flows vertically downward along the sensing zone 170 and the liquid sequentially reduces resistance between a first pair of electrode extensions 158, 160, then a lower, a second pair of electrode extensions 158, 160, and then a lower, third pair of electrode extensions 158, 160, and so on.

[0067] With respect to FIG. 6, the controller 136 may operate the cooling tower 100 using method 200. The controller 136 starts method 200 at step 202 and begins a timer at step 204. The timer may start at zero seconds and begin counting upward to track how long the cooling tower 100 has been operating in a particular mode, for example, in a wet mode or a dry mode. In the wet mode, the controller 136 causes the liquid distribution system 108 to distribute liquid onto the adiabatic pads 132 to saturate the adiabatic pads 132 and cool the air entering the cooling tower 100 through the adiabatic pads 132. In the dry mode, the controller 136 operates the liquid distribution system 108 so that liquid is not being distributed to the adiabatic padsDocket No. 21067-163053 (BAC236-US)132, such as by turning off a pump of the liquid distribution system 108. The controller 136 determines 206 whether the cooling tower 100 is operating in the wet mode or not (e.g., the cooling tower 100 is operating in the dry mode).

[0068] Where the controller 136 at step 206 determines that the cooling tower 100 is not operating in the wet mode, the controller 136 determines 208 one or more target values for the liquid sensors 134 of the adiabatic pads 132 that indicate whether the adiabatic pads 132 are sufficiently saturated to provide adequate cooling of the air passing therethrough. The target values may include, for example, a voltage detected at one or more sensing zones 152 of the liquid sensor or an integer value output for one or more sensing zones 152 that corresponds to a wetness level of the associated portion of the adiabatic pad 132. The target values may correspond to a saturation efficiency of the adiabatic pad 132 in cooling the air, for example, a saturation efficiency of at least 92%.

[0069] The controller 136 may may account for airflow conditions at the cooling tower 100 (e.g., temperature, relative humidity, fan speed, etc.) when determining the target values for the sensors 134. The target values may also account for the conductivity of the liquid distributed by the liquid distribution system 108. For example, the controller 136 may receive data indicating the conductivity of the liquid distributed to the adiabatic pads (e.g., from a conductivity sensor) and determine target values for the one or more sensing zones 152 based in part on the conductivity of the liquid. The target values may be different for each liquid sensor 134 and for each sensing zone 152 based on the location of the liquid sensor 134 and sensing zone 152. For example, the target values for sensing zones 152 proximate the lower end portion 147 of the adiabatic pad 132 may be lower than the target values for sensing zones 152 proximate the upper end portion 146 of the adiabatic pad 132 due to liquid evaporating into the airflow as the liquid travels down along the adiabatic pad body 131. The controller 136 may determine the target values for the liquid sensor 134 by referencing a data structure indicating target values for the sensors 134 at various ambient conditions and / or various liquid conductivity levels. The controller 136 may select the target values based on the ambient conditions and / or liquid conductivity level, e.g., measured by other sensors of the cooling tower 100 such as a temperature sensor, humidity sensor, and / or conductivity sensor. The data structure may be, asDocket No. 21067-163053 (BAC236-US) examples, a lookup table, a graph, a formula. The target values for the liquid sensor 134 may be based on historical data, for example, data collected during a calibration process.

[0070] The controller 136 determines 210 whether the sensor reading of the liquid sensor 134 of the adiabatic pad 132 is below the determined target value (e.g., the adiabatic pads 132 are too dry). In some approaches, the controller 136 may calculate an average sensor reading based on the sensor readings of a plurality of sensing zones 152 of the liquid sensor 134 to compare to the target value. In another approach, the controller 136 may compare the sensor reading of each sensing zone 152 to the target value. The controller 136 may determine the sensor reading is below the target when some or all of the sensor readings are below the target value. Where the cooling tower 100 includes multiple sensors 134, the controller 136 may similarly compare the sensor readings of each liquid sensor 134 to the target value(s), for example, by taking an average of each sensing zone 152 (or one or more sensing zones 152 in a certain area) and / or comparing the sensor readings of each zone 152 to the target values. In some approaches, the controller 136 may determine a target value for each liquid sensor 134 and / or sensing zone 152 of the liquid sensor 134. For instance, the target value may be based at least in part on the location of the liquid sensor 134 and / or sensing zone 152 in the cooling tower 100. Where the controller 136 determines 210 that the sensor reading of the liquid sensor 134 is not below the target value, the controller 136 returns to step 206.

[0071] Where the controller 136 determines 210 that the sensor reading of the liquid sensor 134 is below the target value, the controller 136 determines 212 whether the timer set at step 204 has exceeded a minimum delay time period. The minimum delay time period may be, as examples, one minute, two minutes, or five minutes. Where the timer has not exceeded the minimum delay time period at step 212, the controller returns to step 210. The minimum delay time period is used to ensure that the cooling tower 100 operates in the dry mode for a minimum period of time before permitting the cooling tower 100 to switch modes (e.g., to the wet mode). Operating in the dry mode for a minimum period of time aids in stabilizing the performance of the cooling tower 100, for example, permitting the cooling tower 100 to reach a steady state upon entering the dry mode.Docket No. 21067-163053 (BAC236-US)

[0072] Where the timer exceeds the minimum delay time period, the controller 136 causes the cooling tower 100 to switch 214 to the wet mode, for example, by causing the liquid distribution system 108 to distribute liquid to the adiabatic pads 132. The controller 136 then returns to step 204 to reset the timer to track the time the cooling tower 100 operates in the wet mode.

[0073] Where the controller 136 determines 206 that the cooling tower 100 is operating in the wet mode, the controller 136 determines 216 one or more target values for the sensors 134 of the adiabatic pads 132 that indicate the adiabatic pads 132 are not oversaturated. The target values may correspond to a saturation efficiency of the adiabatic pad 132 in cooling the air, for example, a saturation efficiency that does not exceed 98%. Where the adiabatic pads 132 are oversaturated, liquid may flow through the adiabatic pad 132 to the tray 172. Oversaturation of the adiabatic pads 132 can result in consuming excess amounts of liquid, particularly in embodiments where the liquid is not recirculated from the tray 172 to the headers 116 of the liquid distribution system 108. The target values of the sensors 134 may be values that achieve sufficient saturation of the adiabatic pad 132 while minimizing the amount of liquid leaving (e.g., dripping off) the adiabatic pad 132 to minimize water consumption. For example, the target values may achieve a saturation level that permits all liquid distributed to the adiabatic pad 132 to be evaporated into the air flowing through the adiabatic pads 132. The cooling tower 100 may account for ambient conditions at the cooling tower 100 (e.g., temperature, relative humidity, etc.) when determining the one or more target values for the sensors 134. The target values may also account for the conductivity of the liquid distributed by the liquid distribution system 108. The target values may be different for each liquid sensor 134 and for each sensing zone 152 based on the location of the liquid sensor 134 and sensing zone 152. For example, the target values for sensing zones 152 proximate the lower end portion 147 of the adiabatic pad 132 may be lower than the target values for sensing zones 152 proximate the upper end portion 146 of the adiabatic pad 132 due to liquid evaporating into the airflow as the liquid travels down the adiabatic pad 132. The controller 136 may determine the target values by referencing a data structure indicating target values for the sensors 134 at various ambient conditions. The controller 136 may select the target values based on the ambient conditions, e.g.,Docket No. 21067-163053 (BAC236-US) measured by other sensors of the cooling tower 100 such as a temperature sensor and / or humidity sensor. The data structure may be, as examples, a lookup table, a graph, a formula. The target values for the liquid sensor 134 may be based on historical data, for example, data collected during a calibration process.

[0074] The controller 136 determines 218 whether the sensor reading of the liquid sensor 134 of the adiabatic pad 132 is above the determined target value (e.g., the adiabatic pads 132 are too wet). In some approaches, the controller 136 may calculate an average sensor reading based on the sensor readings of each sensing zone 152 of the liquid sensor 134 to compare to the target value. In some approaches, the controller 136 may compare the sensor reading of each sensing zone 152 to the target value. The controller 136 may determine the sensor reading is above the target value when some or all of the sensor readings of the liquid sensor 134 are above the target value. Where the cooling tower 100 includes multiple sensors 134, the controller 136 may similarly compare the sensor readings of each liquid sensor 134 to the target values, for example, by taking an average of the sensing zones 152 of the liquid sensor 134 and / or comparing the sensor reading of each sensing zone 152 to the target values. In some approaches, the controller 136 may determine a target value for each liquid sensor 134 and / or sensing zone 152 of the liquid sensor 134. For instance, the target value may be based at least in part on the location of the liquid sensor 134 and / or sensing zone 152 in the cooling tower 100. Where the controller 136 determines 218 that the sensor reading of the liquid sensor 134 is not above the target value, the controller 136 returns to step 206.

[0075] Where the controller 136 determines 218 that the sensor reading of the liquid sensor 134 is above the target value, the controller 136 determines 220 whether the timer set at step 204 has exceeded a minimum delay time period. The minimum delay time period may be, as examples, one minute, two minutes, or five minutes. Where the timer has not exceeded the minimum stage delay time period, the controller 136 returns to step 218. The minimum delay time period is used to ensure that the cooling tower 100 operates in the wet mode for a minimum period of time before permitting the cooling tower 100 to switch modes (e.g., to the dry mode). Operating in the wet mode for a minimum period of time aids in stabilizing the performance of the cooling tower 100, for example, permitting the cooling tower 100 to reach a steady state uponDocket No. 21067-163053 (BAC236-US) entering the wet mode. For example, permitting the adiabatic pads 132 to become saturated by absorbing the liquid distributed over the adiabatic pads 132.

[0076] Where the timer exceeds the minimum delay time period, the controller 136 causes the cooling tower 100 to switch 224 to the dry mode, for example, by causing the liquid distribution system 108 to cease distribution of liquid to the adiabatic pads 132. The controller 136 then returns to step 204 to reset the timer to track the time the cooling tower 100 operates in the dry mode.

[0077] With respect to FIG. 7A, an adiabatic pad 230 is provided according to another embodiment where the liquid sensor 134 is at an inlet side 231 of an adiabatic pad body 233. As one example, the liquid sensor 134 may be secured to the adiabatic pad body 233 with an adhesive. As another example, the liquid sensor 134 may be secured to the adiabatic pad body 233 with fasteners such as nuts and bolts that extend through the adiabatic pad body 233. The nuts and bolts may be tightened to adjust the pressure with which the sensing zones 152 are pressed against the adiabatic pad body 233. The liquid sensor 134 extends along at least a portion of the length (or height) of the adiabatic pad body 233 to measure the wetness of the adiabatic pad body 233 at different locations along the length of the adiabatic pad body 233. For instance, each sensing zone 152 of the liquid sensor 134 may provide data corresponding to a different portion of the adiabatic pad body 233 along the height of the adiabatic pad body 233. Additionally or alternatively, the liquid sensor 134 may extend along the other sides of the adiabatic pad body 233, for example, the outlet side of the adiabatic pad body 233 opposite the inlet side 231. The controller 136 may compare the wetness data of the liquid sensor 134 to determine whetherthe adiabatic pad body 233 is sufficiently soaked (e.g., having a wetness level to achieve the desired saturation efficiency) along the length of the adiabatic pad body 233. In some embodiments, the adiabatic pad 230 includes multiple sensors 134 that extend along the length of the adiabatic pad body 233 and which are spaced apart from one another along the width of the adiabatic pad body 233 and / or along different sides of the adiabatic pad body 233. Employing multiple liquid sensors 134 further enables monitoring the wetness of the adiabatic pad body 233 at various, different locations on the adiabatic pad body 233 (e.g., at opposite ends of the adiabatic pad body 233).Docket No. 21067-163053 (BAC236-US)

[0078] With respect to FIG. 7B, a graph 220 is provided showing test data that illustrates the correlation of the saturation efficiency of the adiabatic pad body 233 to the wetness of the adiabatic pad body 233 as measured by a liquid sensor on the inlet side 231 of the adiabatic pad body 233 (e.g., as shown in FIG. 7A). The data from two tests are shown in the graph 220. In one test, the fans 102 were operated at 100% fan speed for the duration of the test. In the other test, the fans 102 were operated at 50% fan speed for the duration of the test. In both tests, the liquid distribution system 108 was operated in the wet mode to distribute liquid to the adiabatic pad body 233 from about 14 minutes to about 72 minutes. The liquid distribution system 108 was then shut off to cease distributing liquid to the adiabatic pad body 233 for the remainder of the test.

[0079] Regarding the first test, the data points 222 indicate the measured saturation efficiency of the adiabatic pad body 233 during the test where the fans 102 were operated at 100% fan speed. The data points 224 indicate the measured wetness data of the liquid sensor 134 during this test which, as shown, generally correspond to the measured saturation efficiency data points 222 of the adiabatic pad body 233. For example, the WetVal of a data point 224 at 115 minutes after the start of the test is correlated with, or indicates, a saturation efficiency of about 75%.

[0080] Regarding the second test, the data points 226 indicate the saturation efficiency of the adiabatic pad body 233 during the test where the fans were operated at 50% fan speed. The data points 228 indicate the measured wetness data of the liquid sensor 134 which, as shown, generally correspond to the measured saturation efficiency data points 226 of the adiabatic pad body 233. Thus, the wetness data of the liquid sensor 134 may be used to estimate the saturation efficiency of the adiabatic pad body 233. For example, the WetVal of a data point 228 at 115 minutes after the start of the test is correlated with, or indicates, a saturation efficiency of about 85%. The wetness data and / or estimated saturation efficiency of the adiabatic pad body 233 may, for example, be used to make changes to the operation of the cooling tower 100 (e.g., as in method 200 discussed above).

[0081] With respect to FIG. 8, an adiabatic pad 232 is provided according to another embodiment that includes two sensors 134 extending laterally across an inlet side 237 of an adiabatic pad body 235. One liquid sensor 134 is at an upper end portion 239 ofDocket No. 21067-163053 (BAC236-US) the adiabatic pad body 235 to measure wetness across the width of the upper end portion 239 of the adiabatic pad body 235. The other liquid sensor 134 is at a lower end portion 241 of the adiabatic pad body 235 to measure wetness across the width of the lower end portion 241 of the adiabatic pad body 235. The controller 136 may compare the wetness data of the sensors 134 to determine if liquid is distributed evenly across the width of the adiabatic pad body 235 and whether the liquid is flowing evenly to the lower end portion 241 of the adiabatic pad body 235.

[0082] With respect to FIG. 9, an adiabatic pad 234 is provided according to another embodiment that includes liquid sensors 134 that wrap around edges of an adiabatic pad body 243 to extend along multiple sides of the adiabatic pad 234. For example, one liquid sensor 134 has a first portion 134A that extends along an inlet side 245 of the adiabatic pad body 243 and a second portion 134B that extends along a bottom side 252 of the adiabatic pad body 243. The other liquid sensor 134 has a first portion 134C that extends along a side surface 247 and a second portion 134D that extends along an outlet side 254 of the adiabatic pad body 243. The liquid sensors 134 may be wrapped about the edges to position the sensing zones 152 of one liquid sensor 134 on multiple sides of the adiabatic pad 234. Wrapping a liquid sensor 134 around an edge of the adiabatic pad body 243 may permit the liquid sensor 134 to provide wetness data at multiple sides of the adiabatic pad body 243 without having to increase the number of sensors 134 of the adiabatic pad 234.

[0083] With respect to FIG. 10, an adiabatic pad 236 is provided according to another embodiment that includes a liquid sensor 253 covering a side surface 255 of an adiabatic pad body 257. The liquid sensor 253 has a sensor body 253A with a width that corresponds to the thickness of the adiabatic pad body 257 such that the sensor body 253A substantially covers the side surface 255. So configured, the liquid sensor 253 is able to detect whether the entire side surface 255 is wet and / or sufficiently saturated. And, because the liquid sensor 253 is on the side surface 255, the liquid sensor 253 is out of the way of the air flow through the adiabatic pad 236 and has a negligible effect on air flow rate through the adiabatic pad.

[0084] With respect to FIG. 11, an adiabatic pad 238 is provided according to another embodiment that includes a liquid sensor 259 extending inside an adiabatic pad body 261. The liquid sensor 259 has a sensor body 263 extending in an interior of theDocket No. 21067-163053 (BAC236-US) adiabatic pad body 261, for example, between two layers of material forming the adiabatic pad body 261 or in an opening cut into or otherwise formed in the material of the adiabatic pad body 261. In the adiabatic pad 238, the sensor body 263 of the liquid sensor 259 is wrapped about a rod 240 and the rod 240 extends into the adiabatic pad 132 to position the sensor body 263 to measure a wetness of the adiabatic pad 132 at various positions inside the adiabatic pad body 261 along a length of the adiabatic pad body 261. In some forms, the rod 240 may be inserted further into the adiabatic pad body 261 such that all or most of sensing zones 265 of the sensor 259 are in the adiabatic pad body 261. In the example shown, the rod 240 and sensor body 263 extend along the length of the adiabatic pad body 261. In other embodiments, the rod 240 and sensor body 263 may extend along a width, depth, or diagonally in the adiabatic pad body 261.

[0085] With respect to FIG. 12, an adiabatic pad 242 is provided according to another embodiment including an adiabatic pad body 271 and liquid sensors 244. The liquid sensors 244 include a first electrode 246 and second electrode 248 disposed on surfaces of the adiabatic pad body 271, for example, without a sensor body supporting the first and second electrodes 246, 248. For example, the first electrode 246 and second electrode 248 are disposed directly on the adiabatic pad body 271, for example, printed on or adhered to the surfaces of the adiabatic pad body 271. In one approach, the first electrode 246 and second electrode 248 are formed of conductive ink printed on surfaces of the adiabatic pad body 271, for example, external surfaces and / or internal surfaces of the layers of material forming the adiabatic pad body 271. In another form, the first electrode 246 and second electrode 248 include conductors such as wires associated with the surfaces of the adiabatic pad body 271, for example, with an adhesive.

[0086] With respect to FIG. 13, the cooling tower 100 may include a liquid sensor 134 positioned below the dispensing openings 118 of the liquid distribution system 108 to detect the liquid dispensed from the liquid distribution system 108. For example, the sensor body 150 of the liquid sensor 134 may be above an upper end portion 146 of the adiabatic pad 132 and extend along at least a portion of a width of the adiabatic pad 132 to sense the liquid distributed by the liquid distribution system 108 to the adiabatic pad 132. For instance, the sensor body 150 may extend along length of aDocket No. 21067-163053 (BAC236-US) pipe 250 of the header 116 of the liquid distribution system 108 having the dispensing openings 118 to detect liquid emitted from the dispensing openings 118. The controller 136 may process the sensor data for the various sensor zones 152 of the liquid sensor 134 to determine whether the liquid distribution system 108 is distributing liquid evenly to the adiabatic pad 132. For instance, the liquid sensor 134 may be used to detect whether all of the dispensing openings 118 are dispensing liquid and / or are dispensing liquid at substantially the same rate. Uneven liquid distribution may occur, for example, when a dispensing opening 118 is clogged.

[0087] Regarding FIG. 14, the controller 136 may use one or more liquid sensors, such as liquid sensors 134, to operate the cooling tower 100 according to a method 300. The controller 136 starts the method 300 at step 302 and receives 304 sensor data from one or more sensors 134 of one or more of the adiabatic pads 132 of the cooling tower 100. For example, each adiabatic pad 132 may include multiple sensors 134 at different locations on the adiabatic pads 132 to monitor the wetness at various locations of the adiabatic pad 132. As another example, the sensing zones 152 of a liquid sensor 134 may be at different locations of the adiabatic pad 132 to monitor the wetness at such locations and the controller 136 receives sensor data for each sensing zone 152 of the sensors 134.

[0088] The controller 136 determines 306 whether moisture is evenly distributed across the adiabatic pad 132 based on the sensor data collected at the different locations of the adiabatic pad 132 by the one or more sensors 134. For example, the controller 136 may compare the sensor data collected at multiple different portions of the adiabatic pad 132 and determine the moisture is not evenly distributed based on differences in the sensor data. For example, the controller 136 may determine moisture is not evenly distributed where the sensor data indicates some regions of the adiabatic pad 132 are significantly drier or wetter than other regions of the adiabatic pad 132. For instance, the controller 136 may compare the sensor data at multiple locations across the width of the adiabatic pad 132 and determine there is uneven moisture distribution upon detecting more than a threshold wetness variability across the locations. The controller 136 may additionally or alternatively compare the sensor data at multiple locations across the height of the adiabatic pad 132. The controller 136 may detect there is uneven moisture distribution when theDocket No. 21067-163053 (BAC236-US) moisture detected at each height is outside of an expected range based on the moisture at the other heights measured. For instance, as liquid flows downward through the adiabatic pad 132, the liquid may evaporate into the air flowing through the adiabatic pad 132 and thus the controller 136 may be configured to expect the adiabatic pad 132 to be wetter near the top and drier near the bottom (e.g., progressively drier downward along the height of the adiabatic pad 132).

[0089] Where the controller 136 determines 306 there is uneven moisture distribution, the controller 136 outputs 308 an alert. The alert may notify maintenance personnel that the cooling tower 100 is in need of maintenance. The controller 136 may be configured to send a notification to another computing device of the alert, for example, the master controller of the HVAC system. The alert may cause an indicator (e.g., a light of a control panel or a siren) to activate to indicate that maintenance is needed. As another example, the controller 136 may communicate an email or a SMS message to a portable electronic device of a maintenance worker.

[0090] Uneven moisture distribution may indicate an abnormality in the liquid distribution system 108 and / or adiabatic pad 132. For example, a dispensing opening 118 of the liquid distribution system 108 may be clogged inhibiting even distribution of liquid over the adiabatic pad 132. As another example, the adiabatic pad 132 may be damaged or clogged inhibiting the liquid from flowing uniformly through the adiabatic pad 132. Upon outputting the alert, the controller 136 returns to step 304 to continue monitoring the adiabatic pads 132.

[0091] Where the controller 136 determines 306 there is even moisture distribution, the controller 136 may conclude 310 that no abnormalities are detected and return to step 304 to continue monitoring the moisture distribution of the adiabatic pad 132.

[0092] Regarding FIG. 15, the controller 136 may use one or more liquid sensors 134 to operate the cooling tower 100 according to method 400. The controller 136 starts the method 400 at step 402 and receives 404 sensor data from multiple locations of one or more of the adiabatic pads 132 of the cooling tower 100 similar to step 304 discussed above. For example, the controller 136 may receive sensor readings from one or more sensors 134 corresponding to different locations of one of the adiabatic pads 132 to monitor the wetness levels at various locations of the adiabatic pad 132.Docket No. 21067-163053 (BAC236-US)

[0093] The controller 136 determines 406 whether moisture is evenly distributed across the adiabatic pad 132 based on the sensor data collected at the different locations of the adiabatic pad 132 by the one or more sensors 134 similar to step 306 discussed above.

[0094] Where the controller 136 determines 406 there is uneven moisture distribution, the controller 136 adjusts 408 the distribution of liquid from the liquid distribution system 108 to the adiabatic pads 132. For example, the controller 136 may adjust the flow of liquid from the liquid distribution system 108 to achieve an even distribution of moisture across the adiabatic pad 132. In some forms, the liquid distribution system 108 is configured to control the flow of liquid to various portions along the width of the adiabatic pad 132. For example, the liquid distribution system 108 may include a plurality of headers 116 positioned along the width of the adiabatic pad 132 to enable control of the flow of liquid to each portion of the adiabatic pad 132. The liquid distribution system 108 may include multiple pumps each operable to pump liquid to an associated header 116. The pumps may be controlled individually to control the flow rate of liquid to each header 116 and thus from the headers 116 to the associated portion of the adiabatic pad 132. In another approach, the liquid distribution system 108 may include a proportional valve associated with each header 116 to control the amount of liquid flowing to each header 116 and thus the flow rate of the liquid to the associated portion of the adiabatic pad 132. In yet another approach, the dispensing openings 118 of the headers 116 are adjustable to control the flow rate therethrough, for example, a size of the dispensing openings 118 can be increased or decreased to increase or decrease a flow rate therethrough. Upon adjusting the distribution of liquid from the liquid distribution system 108, the controller 136 returns to step 304 to continue monitoring the adiabatic pads 132.

[0095] Where the controller 136 determines 406 there is even moisture distribution, the controller 136 may conclude 410 that no abnormalities are detected and return to step 404 to continue monitoring the moisture distribution of the adiabatic pad 132.

[0096] Regarding FIG. 16, the controller 136 may use one or more liquid sensors 134 to operate the cooling tower 100 according to method 500 to detect changes to the wetting ability of the liquid distribution system 108 and / or adiabatic pad 132 over time. The controller 136 starts the method 500 at step 502 and compares 504 sensorDocket No. 21067-163053 (BAC236-US) data from the one or more liquid sensors 134 of the adiabatic pads 132 with historical sensor data of the cooling tower 100 at the same operating conditions. For example, the controller 136 may store historical sensor data of the sensors 134 in memory 140. The controller 136 may record the sensor data of the liquid sensors 134 over time in association with the operating conditions of the cooling tower 100, such as an operation mode of the cooling tower 100 (e.g., wet, dry, adiabatic), a speed of the fan 102, whether the liquid distribution system 108 is distributing liquid to the adiabatic pads 132, and / or ambient conditions (e.g. air temperature and / or humidity).

[0097] The controller 136 determines 506 whether the sensor data of the liquid sensors 134 has changed over time. For example, the controller 136 may determine if the current sensor data deviates substantially (e.g., more than a threshold) from previously recorded sensor data at similar operating settings and / or under similar ambient conditions based on the comparison of the current sensor data of the sensors 134 with the stored sensor data. The sensor data may gradually change over time due to gradual wear or accumulation of dirt and / or scale in the liquid distribution system 108 and / or adiabatic pad 132. For example, the accumulation of dirt or scale in the adiabatic pad 132 may reduce contact between the water in the pad and the electrodes of the sensors 134 such that the sensor 134 detects a higher electrical resistance than it should for a given wetness of the adiabatic pad 132. The sensor data may also change abruptly, for example, when the adiabatic pad 132 or liquid distribution system 108 malfunctions (e.g. the pump 109 fails).

[0098] Where the controller 136 determines that the sensor data is abnormal (e.g., the sensor data deviates from the historical sensor data), the controller 136 may determine that the liquid flow conditions of the liquid distribution system 108 and / or adiabatic pad 132 are irregular and output 508 an alert. The controller 136 may determine an irregularity is present and issue the alert where the sensor data indicates that flow at one or more regions of the adiabatic pads 132 are abnormal (e.g., different than historical sensor data under normal conditions). The abnormal flow conditions may be indicative of a malfunction in the liquid distribution system 108 and / or adiabatic pad 132, for example, a clogged dispensing opening 118, dirty adiabatic pad 132, etc.Docket No. 21067-163053 (BAC236-US)

[0099] The alert may notify maintenance personnel that the cooling tower 100 is in need of maintenance. The controller 136 may be configured to send a notification to another computing device of the alert, for example, the master controller of the HVAC system. The alert may cause an indicator (e.g., a light of a control panel or a siren) to indicate maintenance is needed. Upon outputting the alert, the controller 136 returns to step 504 to continue monitoring the sensor data of the liquid sensors 134.

[0100] Where the controller 136 determines 506 the sensor data is normal (e.g., the sensor data is sufficiently similar to the historical sensor data), the controller 136 may conclude 510 that no abnormalities are detected and return to step 504 to continue monitoring the sensor data of the liquid sensors 134.

[0101] Regarding FIG. 17, the controller 136 may use the one or more liquid sensors 134 to operate the cooling tower 100 according to method 600. The controller 136 starts the method 600 at step 602 and compares 604 sensor data from each of the one or more liquid sensors 134 of the adiabatic pads 132 with historical sensor data of the cooling tower 100 at the same operating settings similar to step 604 discussed above.

[0102] The controller 136 determines 606 whether the sensor data of the sensors 134 has changed over time similar to step 506 discussed above. Where the controller 136 determines that the sensor data is abnormal (e.g., the sensor data deviates from the historical sensor data), the controller 136 determines that the liquid flow conditions of the liquid distribution system 108 and / or adiabatic pad 132 are irregular and causes 608 the cooling tower 100 to enter a self-cleaning mode. In the self-cleaning mode, the fans 102 are run in reverse to cause air to flow through the adiabatic pads 132 in a direction opposite of the normal airflow paths 120, for example, to blow debris out of the adiabatic pads 132. In embodiments where the liquid is recirculated from the trays 172 to the headers 116, the liquid may be drained from the cooling tower 100 and replaced with fresh liquid in the self-cleaning mode. Upon completion of the selfclean cycle, the controller 136 returns to step 604 to continue monitoring the sensor data of the liquid sensors 134.

[0103] Where the controller 136 determines 606 the sensor data is normal (e.g., the sensor data is similar to the historical sensor data), the controller 136 may concludeDocket No. 21067-163053 (BAC236-US)610 that no abnormalities are detected and return to step 604 to continue monitoring the sensor data of the liquid sensors 134.

[0104] With respect to FIG. 18, in one embodiment, the cooling tower 100 includes a liquid sensor 701 on an adiabatic pad drain surface 700 of the cooling tower 100. The liquid sensor 701 is similar to the liquid sensors, such as liquid sensor 134, discussed above. The adiabatic pad drain surface 700 may be a surface of the cooling tower 100 beneath the adiabatic pad 132, for example, a surface of a tray on which the adiabatic pad 132 rests. The liquid sensor 701 may be mounted to the adiabatic pad drain surface 700 with an adhesive. The liquid sensor 701 may be on the adiabatic pad drain surface 700 to measure the amount of liquid exiting the adiabatic pad 132, for example, the liquid that flowed through the adiabatic pad 132. The liquid exiting the adiabatic pad 132 at the drain surface 700 may flow to a sump to be recirculated through the liquid distribution system 108 or to a drain to be removed from the cooling tower 100. The controller 136 may use the sensor data of the liquid sensor 701 at the adiabatic pad drain surface 700 to control operation of the cooling tower 100 similar to the approaches discussed above, for example, to achieve the desired adiabatic pad 132 saturation, to detect even distribution of liquid in the adiabatic pads 132, and to detect abnormalities in the adiabatic pads 132 and / or liquid distribution system 108. For example, the controller 136 may have a target value or sensor reading for the liquid sensor 701 at the adiabatic pad drain surface 700 and operate the liquid distribution system 108 to achieve the target value. For example, the target value may correspond to a range of wetness values that indicate moisture is reaching the lower end of the adiabatic pad 132 but a low amount of liquid is flowing off of the adiabatic pad 132. In other words, the target value may indicate the adiabatic pad 132 is sufficiently saturated to achieve the desired saturation efficiency but not oversaturated. Using a liquid sensor 701 at the adiabatic pad drain surface 700 may be advantageous particularly in cooling towers 100 where the liquid flowing off of the adiabatic pad 132 is not recirculated. In such cooling towers 100, the liquid sensor 701 at the adiabatic pad drain surface 700 may be used to minimize liquid waste.

[0105] With respect to FIG. 19, in one embodiment, the cooling tower 100 includes a liquid sensor 705 mounted on the coil 112 of the heat exchanger 110 between the adiabatic pads 132 and coil 112 downstream of the adiabatic pads 132 in the directionDocket No. 21067-163053 (BAC236-US) of airflow through the cooling tower 100. The liquid sensor 705 is similar to the liquid sensors discussed above. In one embodiment, the coil 112 is a tube-and-fin coil. As one example, the liquid sensor 705 is mounted to the coil 112 with an adhesive. The cooling tower 100 may have multiple liquid sensors 705 on the coil 112 (similar to the adiabatic pads 132 discussed above) to measure the wetness as different locations of the coil 112. The liquid sensors 705 may also include multiple sensing zones 707 to measure the wetness at various locations of the coil 112.

[0106] The liquid sensor 705 may be on the upstream side of the coil 112 to measure moisture collecting on the coil 112 from the adiabatic pads 132, such as droplet peel- off and condensation. The controller 136 may use the sensor data of the liquid sensor 705 at the coil 112 to control operation of the cooling tower 100 similar to the approaches discussed above to achieve the desired adiabatic pad 132 saturation. For example, the controller 136 may have a sensor reading or target value for the liquid sensor 705 at the coil 112 and operate the liquid distribution system 108 to achieve the target value. For example, the target value for the liquid sensor 705 at the coil 112 may correspond to a range of wetness values that indicates the adiabatic pad 132 is sufficiently saturated to achieve the desired saturation efficiency but not oversaturated. The controller 136 may also use the sensor data of the liquid sensor 705 at the coil 112 to detect even distribution of liquid to the adiabatic pad 132 and / or detect abnormalities in the adiabatic pads 132 and / or liquid distribution system 108 using the approaches discussed above. For example, the cooling tower 100 may include multiple sensors 705 on the coil 112 and / or the sensor(s) 705 may have multiple sensing zones 152 to measure the moisture from the air leaving the adiabatic pad 132 at various locations. The sensor data may be compared to detect even or uneven liquid distribution on the adiabatic pad 132. The sensor data at the coil 112 may also be compared with historical sensor data at similar operating conditions to detect abnormalities in the operation of the cooling tower 100. For example, the sensor data may be compared to historical data to detect abnormal liquid distribution on the adiabatic pad 132 and / or abnormal airflow through the adiabatic pad 132 (e.g., due to a clogged or damaged adiabatic pad).

[0107] Regarding FIGS. 20A-20B, another heat exchange medium, a coil 650, of an indirect heat exchanger is shown according to another embodiment for use in aDocket No. 21067-163053 (BAC236-US) closed-circuit cooling tower. The indirect heat exchanger coil 650 may be used as the heat exchanger 110 in the cooling tower 100. The coil 650 includes a plurality of serpentine coils through which the process liquid flows. The serpentine coils each include a series of straight runs 652 and bends 654 connecting the straight runs 652. Air flows over the coil 650 to exchange heat with the process liquid in the coil 650. The coil 650 may include one or more liquid sensors 659 on the coil 650, such as one liquid sensor 659 on one or more straight runs 652 of each serpentine tube, to measure the wetness at various locations of the coil 650. The liquid sensor 659 may be mounted to the coil 650 with an adhesive, for example, between the sensor body 661 and the coil 650. While the liquid sensor 134 shown has one sensing zone 663, in other forms, the liquid sensor 659 may have multiple sensing zones 663 spaced along the coil 650.

[0108] The controller 136 may use the liquid sensors 659 of the coil 650 to detect when moisture is being carried from the adiabatic pad 132 to the coil 650. The controller 136 may adjust operation of the cooling tower 100 to limit the amount of moisture collecting on the coil 650, e.g., to inhibit scale build up on the coil 650. For example, the controller 136 may, for example, shut off the liquid distribution system 108 or reduce a flow rate of the liquid distribution system 108. The controller 136 may also use the liquid sensors 134 similar to the methods discussed above to detect a saturation level of the adiabatic pad 132, even or uneven liquid distribution, and / or abnormalities in operation of the cooling tower (e.g., clogged dispensing opening, damaged adiabatic pad, etc.).

[0109] With respect to FIG. 21, another heat exchange medium, a plate-type indirect heat exchanger 702, is provided that may be used as the heat exchanger 110 in the cooling tower 100. The plate heat exchanger 702 may include one or more liquid sensors 709 mounted to exterior surfaces of the plates 704 of the plate heat exchanger 702. The liquid sensors 709 are similar to the liquid sensors discussed above. For example, every pair of joined plates 704 of the plate heat exchanger 702 may have one of the liquid sensors 709 mounted thereto.

[0110] The liquid sensors 709 may be used to detect the wetness level at various locations of the plate heat exchanger 702. In some forms, the liquid sensor 709 is secured to the exterior of a respective plate 704 with an adhesive. For example, adhesive is disposed between a sensor body 711 of the liquid sensor 709 and the plateDocket No. 21067-163053 (BAC236-US)704. The liquid sensors 709 may include one or more sensing zones 713 to measure the wetness at various locations of the respective plate 704 of the plate heat exchanger 702. The liquid sensors 709 may be disposed on the plates 704 to collect wetness data along a height or width of the plates 704. The controller 136 may use the sensor data of the sensors of the pillow-plate type indirect heat exchanger 702 similar to that described above with the coil 650, for example, to detect moisture collecting on the plates 704, adiabatic pad saturation, uneven liquid distribution, and / or abnormalities with the cooling tower.

[0111] With respect to FIG. 22, another heat exchange medium, a direct heat exchanger such as fill 710, is provided that may be used as a heat exchanger in an open circuit cooling tower. The fill 710 may include a plurality of fill sheets 712. For example the associated cooling tower includes a process liquid distribution system that distributes process liquid over the fill sheet 712 such that the process liquid flows along the surfaces of the fill sheet 712. An airflow generator (e.g., a fan) directs air into contact with the process liquid flowing along the surfaces of the fill sheet 712 to exchange heat with the process liquid. The fill sheets 712 may include patterns of ridges and valleys to form a tortuous flow path for the process liquid and air flowing about the fill sheet 712 to cause mixing of the air and process liquid.

[0112] The fill 710 includes one or more liquid sensors 715 to detect the wetness level at various locations of the fill 710. In one embodiment, the fill sheet 712 includes a fill sheet body 712A and the liquid sensor 715 is secured to the fill sheet body 712A with an adhesive. For example, adhesive is disposed between the liquid sensor 715 and the fill sheet 712. The liquid sensor 715 has first and second electrodes 717, 719 that are secured directly to the fill sheet 712. For example, the first and second electrodes 717, 719 are printed on the surface of the fill sheet body 712A (e.g., with conductive ink). The liquid sensor 715 of the fill sheet 712 may include one or more sensing zones to measure the wetness at various locations of the fill sheet 712. The first and second electrodes 717, 719 may be disposed on the fill sheet 712 when the fill sheet 712 is manufactured and before being assembled together with other fill sheets 712 to form the fill 710. The sensors 715 may be disposed on the fill sheet 712 to collect wetness data along a height and / or width of the fill sheet 712. In some forms, each fill sheetDocket No. 21067-163053 (BAC236-US)712 of the fill 710 includes one or more liquid sensors 715. In other forms, fewer than all of the fill sheets 712 of the fill 710 include liquid sensors 134.

[0113] The controller 136 may use the sensor data of the liquid sensors 715 of the fill 710 to detect whether process liquid is being distributed evenly onto the fill 710 and / or flowing evenly through the fill 710. For example, the controller 136 may use the liquid sensors 715 to detect whether the process liquid is flowing evenly along a height of the fill sheet 712, evenly over a width of the fill sheet 712, and / or evenly across multiple fill sheets 712. Even distribution of liquid over the fill sheet 712 may result in more efficient heat exchange with the air. Uneven distribution of process liquid on the fill 710 may result from a clogged or damaged dispensing opening of the process liquid distribution system and / or dirty or damaged fill 710. In other words, upon detecting an uneven distribution of process liquid in the fill 710, the controller 136 may determine there is an abnormality with the cooling tower and request maintenance or run a self-clean cycle. The sensor data from the fill 710 may also be compared with historical sensor data at the same operating conditions to detect abnormalities in the operation of the cooling tower.

[0114] With respect to FIG. 23, a perspective, schematic view of a portion of the drift eliminator 126 is shown. The drift eliminator 126 includes a plurality of baffles 722. The baffles 722 may include a bend 724 to redirect air flowing through the baffles 722. Drift carried in the air flowing through the baffles 722 may hit the baffles 722 (e.g., at the bends 724) and be removed from the air, for example, because the momentum of the drift particles causes the drift particles to impact against and collect on the surfaces of the bends 724. The drift eliminator 126 may include one or more liquid sensors 721 on the drift eliminator 126 to measure the amount of liquid removed from the air. For example, the liquid sensor 721 may be mounted to the baffle 722 to detect a wetness of the baffle 722. The liquid sensor 721 may be mounted on an upstream surface of the bend 724 of the baffle 722 that the drift contacts to be removed from the air. The amount of moisture on the baffle 722 measured by the liquid sensor 721 may be indicative of the amount of drift removed from the air. The liquid sensor 721 may thus be used to detect when the cooling tower 100 is emitting drift and / or to calculate a drift rate of the cooling tower 100. The controller 136 may adjust operation of the cooling tower 100 (e.g., based on the estimated drift rate) to limit or reduceDocket No. 21067-163053 (BAC236-US) drift. For example, the controller 136 may reduce a speed of the fans 102 and / or operate the liquid distribution system 108 in the dry mode for a period of time.

[0115] Regarding FIG. 24, the controller 136 may use the liquid sensor 721 of the drift eliminator 126 to operate the cooling tower 100 according to method 750. The controller 136 starts the method 750 at step 752 and receives 754 sensor data of one or more liquid sensors 721 at the drift eliminator 126. Additionally or alternatively, the controller 136 may receive sensor data from a liquid sensor 134 in a plenum 762 (see FIG. 1) of the cooling tower 100 (e.g., mounted to walls of the plenum 762), at the fan 102, or at any location downstream of the adiabatic pads 132 and / or heat exchanger 110 of the cooling tower 100. In some forms, the liquid sensor 134 is outside the cooling tower 100 (e.g., on a roof to which the cooling tower 100 is mounted) to measure moisture (e.g., drift or plume) emitted by the cooling tower 100. For conciseness and clarity, the method 750 is primarily described with respect to a liquid sensor 721 at the drift eliminator, although the steps may similarly be applied to sensor data from liquid sensors 134 at the other locations.

[0116] The controller 136 determines 756 whether there is drift or plume based on the sensor data of the liquid sensor 721 at the drift eliminator 126. The liquid sensor 721 is similar to the liquid sensors discussed herein such as liquid sensor 134. In one approach, the controller 136 determines that there is drift or plume upon the liquid sensor 721 detecting more than a threshold wetness level on the baffles 722 of the drift eliminator. For example, where the baffles 722 have more than a threshold wetness level, the controller 136 may determine that drift is being removed from the air by the drift eliminator 126 which indicates that there is drift in the air. The controller 136 may similarly detect the presence of drift or plume using data from sensors in the plenum 762, at the fan 102 or otherwise downstream of the liquid distribution system 108. The controller 136 may store data (e.g., a table in memory 140) indicating a minimum wetness reading of the liquid sensor at the location of the sensor (e.g., at the drift eliminator 126, the plenum 762, fan 102, etc.) that indicates drift or plume.

[0117] Where the controller 136 determines there is drift or plume, the controller 136 moves to step 758 to take action responsive to detecting the presence of drift or plume (e.g., a threshold level of drift or plume). The controller 136 may output an alertDocket No. 21067-163053 (BAC236-US) indicating that drift or plume has been detected. The controller 136 may output an alert similar to the embodiments discussed above, for example, by sending a notification or message to another computing device (e.g., the master controller of the HVAC system) or causing a visual indicator (e.g., a light of a control panel) to illuminate indicating the presence of drift and / or plume. Additionally or alternatively, upon determining there is drift or plume, the controller 136 adjusts operation of the cooling tower 100 to limit or reduce the drift and / or plume. For example, the controller 136 may adjust (e.g., reduce) the speed of the fan 102 and / or adjust the operation of the liquid distribution system 108 (e.g., turn off water flow or reduce the flow rate). Upon outputting the alert and / or adjusting operation of the cooling tower 100, the controller 136 returns to step 754 to continue monitoring the adiabatic pads 132.

[0118] Where the controller 136 determines 756 that no drift or plume is present (or that an acceptable level of drift or plume is present), the controller 136 may conclude 760 that no abnormalities are detected and return to step 754.

[0119] With respect to FIG. 25, the cooling tower 100 may include one or more liquid sensors 751 in a liquid collection basin 764 of the cooling tower 100. The liquid sensors 751 are similar to the liquid sensors discussed above such as liquid sensor 134. The liquid collection basin 764 may be below the adiabatic pads 132 to collect liquid of the liquid distribution system 108 flowing off the adiabatic pads 132. The liquid sensor 751 may be mounted to the liquid collection basin 764 to monitor the level of the liquid in the liquid collection basin 764. For example, the controller 136 may use the liquid sensor 751 in the liquid collection basin 764 to ensure the liquid collection basin 764 does not overflow. The controller 136 may determine the liquid level of the liquid collection basin 764 based on which sensor zones 753 of the liquid sensor 751 indicate they are submersed in liquid.

[0120] One or more sensors 751 may similarly be used in the hot water basin and / or cold water basin of a cooling tower with a direct heat exchanger (e.g., fill 710). For example, a liquid sensor 751 may be mounted in the hot water basin to measure the level of the process liquid in the hot water basin. Similarly, a liquid sensor 751 may be mounted in the cold water basin to measure the level of the process liquid in the cold water basin. The controller 136 may receive the sensor data of the liquid sensors 751Docket No. 21067-163053 (BAC236-US) in the hot water basin and / or cold water basin to determine the amount of process liquid in the system, for example, to determine whether to add more process liquid to the system. The controller 136 may also monitorthe level of the liquid in the hot water basin and / or cold water basin to ensure the liquid does not overflow which, for example, may waste the process liquid. The controller 136 may use the liquid sensors 751 to monitor changes in a liquid level of the hot water basin and / or cold water basin, for example, to detect clogs in dispensing openings and / or in a drain opening restricting liquid flow.

[0121] Regarding FIG. 26, the controller 136 of the cooling tower 100 may use the liquid sensor 751 of the hot water basin and / or cold water basin to operate the cooling tower 100 according to method 800. The controller 136 starts the method 800 at step 802 and receives 804 sensor data of the liquid sensor 751 in the hot water basin and / or cold water basin. The controller 136 determines whether the sensor data indicates that the liquid level in the hot water basin and / or cold water basin is above a low level threshold. The low-level threshold may be a predetermined level (e.g., one inch or a corresponding sensor value) stored in memory 140. Where the controller 136 determines 806 that the liquid level is not above the low-level threshold (e.g., the liquid level is low), the controller 136 causes 808 make-up liquid to be added to the cooling tower 100 to increase the liquid level in the hot water basin and / or cold water basin. For example, the controller 136 opens a liquid make-up valve to add the makeup liquid to the cooling tower 100. The controller 136 then returns to step 804 to monitor the liquid level of the hot water basin and / or cold water basin as makeup water is added. The controller 136 may open the makeup valve for a predetermined length of time (e.g., ten seconds) or may open the makeup valve until the liquid level reaches a predetermined threshold (e.g., three inches) as measured using the liquid sensor 751 of the hot water basin and / or cold-water basin.

[0122] Where the controller 136 determines that the liquid level is above the low- level threshold, the controller 136 determines 810 whether the liquid level is above the high-level threshold. If the liquid level is not above the high-level threshold, the controller returns to step 804 to continue monitoring the liquid level in the hot water basin and / or cold-water basin.Docket No. 21067-163053 (BAC236-US)

[0123] Where the controller determines 810 that the liquid level in the hot water basin or cold-water basin is above the high-level threshold, the controller 136 causes 812 liquid to be drained from the hot water basin and / or cold water basin. For example, the controller 136 opens a drain valve in the basin to drain the liquid from the basin to lower the liquid level in the basin. The high-level threshold may be a predetermined level (e.g., six inches or a corresponding sensor value) stored in memory 140. The controller 136 may open the drain valve for a predetermined length of time (e.g., two minutes) or may open the drain valve until the liquid level reaches a predetermined threshold (e.g., the high-level threshold) as measured using the liquid sensor 751 of the hot water basin or cold water basin. Upon opening the drain valve, the controller 136 returns to step 804 to continue monitoring the liquid level in the hot water basin and / or cold-water basin. This method 800 may similarly be used to monitor and control the liquid level of the tray 172 of the cooling tower 100 that collects the liquid flowing from the adiabatic pads 132.

[0124] With respect to FIG. 27, the controller 136 use one or more liquid sensors, such as liquid sensors 134, to operate the cooling tower 100 according to method 900 to protect moisture sensitive components of the cooling tower 100. The controller 136 starts 902 the method 900 and receives 904 sensor data of one or more liquid sensors 134 at moisture sensitive components of the cooling tower 100. The moisture sensitive components of the cooling tower 100 may be any component prone to damage or degraded performance upon exposure to moisture including, for example, a control box 766 (see FIG. 2), motor 106 of the fan 102, and / or the coil 112 of the heat exchanger 110. The controller 136 determines 906 whether moisture is present at one or more of the moisture sensitive components, for example, whether more than a threshold level of moisture is present. For example, the threshold level of moisture may be a threshold wetness level associated with an electrical resistance between the first electrode 154 and second electrode 156 of a sensing zone 152 of the liquid sensor 134. The threshold level of moisture may be indicative of the density of water droplets at the moisture sensitive component.

[0125] Where the controller 136 determines 906 that moisture is present at one or more of the moisture sensitive components (e.g., more than the threshold level of moisture), the controller 136 proceeds to step 908 to take action responsive toDocket No. 21067-163053 (BAC236-US) detecting the presence of moisture at the one or more of the moisture sensitive components. The controller 136 may output an alert indicating that moisture has been detected at the moisture sensitive component. The controller 136 may output an alert similar to the embodiments discussed above, for example, by sending a notification or message to another computing device (e.g., the master controller of the HVAC system) or causing an indicator (e.g., a light of a control panel or a siren) to operate indicating the presence of moisture at the moisture sensitive component. Additionally or alternatively, the controller 136 adjusts operation of the cooling tower 100 at step 908 to reduce drift in the cooling tower 100 resulting in moisture at the moisture sensitive component to mitigate damage or the potential for damage to the moisture sensitive component. For example, the controller 136 may adjust (e.g., reduce) the fan speed of the fan 102 and / or adjust the operation of the liquid distribution system 108 (e.g., turn off liquid flow or reduce the flow rate) to reduce the moisture content of the air (e.g., drift) traveling to the moisture sensitive components. As another example, the controller 136 may shut down the cooling tower 100, for example, for a period of time and / or until the cooling tower 100 has been serviced. Upon outputting the alert and / or adjusting operation of the cooling tower 100 responsive to the detection of moisture, the controller 136 returns to step 904 to continue monitoring the adiabatic pads 132.

[0126] Where the controller 136 determines 906 that no moisture is present at the moisture sensitive components (or that an acceptable level of moisture is present), the controller 136 may conclude 910 that no abnormalities are detected and return to step 904.

[0127] Uses of singular terms such as "a," "an," are intended to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms. It is intended that the phrase "at least one of" as used herein be interpreted in the disjunctive sense. For example, the phrase "at least one of A and B" is intended to encompass A, B, or both A and B.

[0128] While there have been illustrated and described particular embodiments of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended for the present invention toDocket No. 21067-163053 (BAC236-US) cover all those changes and modifications which fall within the scope of the appended claims.

Claims

Docket No. 21067-163053 (BAC236-US)CLAIMSWhat is claimed is:

1. A heat transfer apparatus comprising: a heat transfer medium; a liquid distribution system configured to distribute liquid to the heat transfer medium; a fan operable to cause air to contact the heat transfer medium; a liquid sensor of the heat transfer medium, the liquid sensor including a sensing zone configured to detect an electrical transport property that is indicative of a wetness of the heat transfer medium, the sensing zone comprising: a first plurality of electrode extensions; and a second plurality of electrode extensions that mesh with and are spaced apart from the first plurality of electrode extensions; a controller operably connected to the liquid distribution system and the liquid sensor, the controller configured to operate the liquid distribution system based at least in part on the electrical transport property to achieve a target wetness level of the heat transfer medium.

2. The heat transfer apparatus of claim 1 wherein the sensing zone comprises a plurality of zones corresponding to different portions of the heat transfer medium.

3. The heat transfer apparatus of claim 2 wherein the liquid sensor comprises including the plurality of sensing zones arranged along a length of the liquid sensor.

4. The heat transfer apparatus of claim 3 wherein the first plurality of electrode extensions and the second plurality of electrode extensions are oriented to extend substantially parallel to or substantially perpendicular to the length of the liquid sensor.Docket No. 21067-163053 (BAC236-US)5. The heat transfer apparatus of claim 1 wherein the liquid sensor comprises a first conductor and a second conductor; and wherein the sensing zone comprises: a first bus connecting the first electrode extensions to the first conductor; and a second bus connecting the second electrode extensions to the second conductor.

6. The heat transfer apparatus of claim 5 wherein the sensing zone comprises a plurality of sensing zones; wherein the first conductor extends between the plurality of sensing zones; and wherein the first bus of each sensing zone is connected to the first conductor.

7. The heat transfer apparatus of claim 6 wherein the liquid sensor includes a control board configured to apply a predetermined voltage signal to all of the sensing zones via the first conductor.

8. The heat transfer apparatus of claim 5 wherein the sensing zone comprises a plurality of sensing zones; wherein the liquid sensor comprises the plurality of sensing zones arranged along a length of the liquid sensor; and wherein the first bus and second bus extend substantially parallel to or substantially perpendicular to the length of the liquid sensor.

9. The heat transfer apparatus of claim 1 wherein the liquid sensor comprises a printed resistive sensor.

10. The heat transfer apparatus of claim 1 wherein the liquid sensor comprises conductive ink electrodes, the conductive ink electrodes comprising the first plurality of electrode extensions and the second plurality of electrode extensions.Docket No. 21067-163053 (BAC236-US)11. The heat transfer apparatus of claim 1 wherein the sensing zone comprises a plurality of sensing zones; and wherein the liquid sensor comprises a processor connected to the plurality of sensing zones, the processor configured to determine a wetness value for each of the sensing zones based upon the electrical transport property detected at each of the sensing zones.

12. The heat transfer apparatus of claim 11 wherein the wetness value comprises an integer for each of the sensing zones; and wherein the controller is configured to operate the liquid distribution system based at least in part upon the integers for the sensing zones.

13. The heat transfer apparatus of claim 1 wherein the electrical transport property includes at least one of electrical conductivity and electrical resistance.

14. The heat transfer apparatus of claim 1 wherein the controller is configured to determine the target wetness level for the heat transfer medium.

15. The heat transfer apparatus of claim 14 wherein the controller is configured to determine whether the wetness level of the heat transfer medium is above or below the target wetness level based at least in part on electrical transport property; and wherein the controller is configured to operate the liquid distribution system to achieve the target wetness level of the heat transfer medium including: reducing a flow rate of liquid from the liquid distribution system to the heat transfer medium upon determining the wetness level of the heat transfer medium is above the target wetness level; and increasing the flow rate of liquid from the liquid distribution system to the heat transfer medium upon determining the wetness level of the heat transfer medium is below the target wetness level.

16. The heat transfer apparatus of claim 1 wherein the controller has a dry mode and a wet mode;Docket No. 21067-163053 (BAC236-US) wherein, in the dry mode, the controller inhibits the liquid distribution system from distributing liquid; wherein, in the wet mode, the controller causes the liquid distribution system to distribute liquid; and wherein the controller is configured to operate the liquid distribution system to achieve the target wetness level of the heat transfer medium including determining to operate in the wet mode or the dry mode to achieve the target wetness level.

17. The heat transfer apparatus of claim 1 wherein the heat transfer medium includes an adiabatic pad; and wherein the target wetness level corresponds to a predetermined saturation efficiency of the adiabatic pad.

18. The heat transfer apparatus of claim 1 wherein the sensing zone includes a first zone corresponding to a first portion of the heat transfer medium and a second zone corresponding to a second portion of the heat transfer medium; wherein the controller is configured to determine the target wetness level for the heat transfer medium including determining a first target wetness level for the first portion of the heat transfer medium and a second target wetness level for the second portion of the heat transfer medium, the second target wetness level being different than the first target wetness level; and wherein the controller is configured to operate the liquid distribution system to achieve the first target wetness level for the first portion of the heat transfer medium and achieve the second target wetness level for the second portion of the heat transfer medium.

19. The heat transfer apparatus of claim 1 wherein the heat transfer medium comprises an adiabatic pad having an upper portion and a lower portion; wherein the liquid distribution system is configured to distribute liquid to the upper portion of the adiabatic pad, the adiabatic pad configured to permit the liquid to travel from the upper portion to the lower portion under the effect of gravity; and wherein the controller is configured to determine the target wetness level for the heat transfer medium including determining a target wetness level to enable wetting of theDocket No. 21067-163053 (BAC236-US) lower portion of the adiabatic pad while inhibiting liquid from flowing off of the lower portion of the adiabatic pad.

20. The heat transfer apparatus of claim 1 wherein the liquid sensor includes a plurality of liquid sensors, each liquid sensor having one or more sensing zones.

21. The heat transfer apparatus of claim 1 wherein the sensing zone comprises a plurality of sensing zones corresponding to different portions of the heat transfer medium; wherein the liquid sensor is configured to detect the electrical transport property at each of the sensing zones that is indicative of a wetness of the corresponding portion of the heat transfer medium; and wherein the controller is configured to determine whether the liquid is evenly distributed on the heat transfer medium based at least in part upon the wetness at each sensing zone.

22. The heat transfer apparatus of claim 21 wherein the controller is configured to operate the liquid distribution system to achieve the target wetness level including adjusting a distribution of liquid from the liquid distribution system to the heat transfer medium in response to determining the liquid is unevenly distributed on the heat transfer medium.

23. The heat transfer apparatus of claim 21 wherein the controller is configured to output an alert for maintenance upon a determination that the liquid is unevenly distributed on the heat transfer medium.

24. The heat transfer apparatus of claim 1 wherein the controller is configured to determine the target wetness level for the heat transfer medium based at least in part upon an airflow parameter.

25. The heat transfer apparatus of claim 1 wherein the controller is configured to receive data indicative of a conductivity of the liquid; and wherein the controller is configured to determine the target wetness level for the heat transfer medium based at least in part on the conductivity of the liquid.Docket No. 21067-163053 (BAC236-US)26. The heat transfer apparatus of claim 1 wherein the heat transfer medium includes: fill; a serpentine tube heat exchanger; or a plate heat exchanger.

27. The heat transfer apparatus of claim 1 wherein the controller is configured to: detect an abnormal flow condition based on the electrical transport property; and initiate a self-cleaning mode upon detecting the abnormal flow condition.

28. A heat transfer medium apparatus comprising: a heat transfer medium; a liquid sensor of the heat transfer medium, the liquid sensor including a sensing zone configured to detect an electrical transport property that is indicative of a wetness of the heat transfer medium, the sensing zone comprising: a first plurality of electrode extensions; and a second plurality of electrode extensions that mesh with and are spaced apart from the first plurality of electrode extensions.

29. The heat transfer medium apparatus of claim 28 wherein the sensing zone comprises a plurality of sensing zones corresponding to different portions of the heat transfer medium.

30. The heat transfer medium apparatus of claim 29 wherein the liquid sensor comprises the plurality of zones arranged along a length of the liquid sensor.

31. The heat transfer apparatus of claim 30 wherein the first plurality of electrode extensions and the second plurality of electrode extensions are oriented to extend substantially parallel to or substantially perpendicular to the length of the liquid sensor.

32. The heat transfer medium apparatus of claim 28 wherein the liquid sensor comprises a first conductor and a second conductor; and wherein the sensing zone comprises:Docket No. 21067-163053 (BAC236-US) a first bus connecting the first electrode extensions to the first conductor; and a second bus connecting the second electrode extensions to the second conductor.

33. The heat transfer medium apparatus of claim 32 wherein the sensing zone comprises a plurality of sensing zones; and wherein the first conductor extends between the plurality of sensing zones; and wherein the first bus of each sensing zone is connected to the first conductor.

34. The heat transfer medium apparatus of claim 33 wherein the liquid sensor includes a control board configured to apply a predetermined voltage signal to all of the sensing zones via the first conductor.

35. The heat transfer medium apparatus of claim 32 wherein the sensing zone comprises a plurality of sensing zones; wherein the liquid sensor comprises the plurality of sensing zones arranged along a length of the liquid sensor; and wherein the first bus and second bus extend substantially parallel to or substantially perpendicular to the length of the liquid sensor.

36. The heat transfer medium apparatus of claim 28 wherein the liquid sensor comprises a printed resistive sensor.

37. The heat transfer medium apparatus of claim 28 wherein the liquid sensor comprises conductive ink electrodes, the conductive ink electrodes comprising the first plurality of electrode extensions and the second plurality of electrode extensions.

38. The heat transfer medium apparatus of claim 28 wherein the sensing zone comprises a plurality of sensing zones; and wherein the liquid sensor comprises a processor connected to the plurality of sensing zones, the processor configured to determine a wetness value for each of theDocket No. 21067-163053 (BAC236-US) sensing zones based upon the electrical transport property detected at each of the sensing zones.

39. The heat transfer medium apparatus of claim 38 wherein the wetness value comprises an integer for each of the sensing zones.

40. The heat transfer medium apparatus of claim 28 wherein the electrical transport property includes at least one of electrical conductivity and electrical resistance.

41. The heat transfer apparatus of claim 28 wherein the heat transfer medium comprises an adiabatic pad.

42. The heat transfer apparatus of claim 28 wherein the heat transfer medium includes: fill; a serpentine tube heat exchanger; or a plate heat exchanger.

43. The heat transfer apparatus of claim 28 wherein the liquid sensor comprises a plurality of liquid sensors, each of the liquid sensors having at least one sensing zone.

44. The heat transfer apparatus of claim 28 wherein the heat transfer medium comprises an adiabatic pad having an air inlet surface, an air outlet surface, and a side surface extending between the air inlet surface and the air outlet surface; and wherein the sensing zone of the liquid sensor is disposed on at least one of the air inlet surface, the air outlet surface, and the side surface of the adiabatic pad.

45. The heat transfer apparatus of claim 28 wherein the heat transfer medium comprises an adiabatic pad; and wherein the sensing zone is in the adiabatic pad.Docket No. 21067-163053 (BAC236-US)46. The heat transfer apparatus of claim 28 wherein the first plurality of electrode extensions and the second plurality of electrode extensions each include a number of electrode extensions in a range of three to nine electrode extensions.

Images