Patent Description:
A thermal management system in a gas turbine engine may maintain operable temperatures for fuel, oil, and other fluid communicated through the engine. Thermal management systems may employ fuel on board an aircraft as a heat sink to increase operational efficiency of the aircraft. As thermal loads increase due to enhanced electrical architecture in aircraft, a higher thermal load is imposed on the fuel. Conventional methods for accommodating increased thermal loads tend to achieve greater heat transfer by increasing the number heat exchangers or the size of heat exchangers within the system. Increasing the number or size of the heat exchangers can impose additional weight, space, and/or complexity to the airframe.

<CIT> discloses a cooling system for a gas turbine engine, the system comprising a fuel air heat exchanger comprising a fuel passage in thermal contact with an engine cooling air passage.

<CIT> discloses a method of protecting fuel hardware in a gas turbine engine. The method may include determining a current altitude of the aircraft and controlling a temperature of fuel for the gas turbine engine based at least in part on the current altitude.

From a first aspect, a fuel-based thermal management system as claimed in claim <NUM> is provided.

In various embodiments, modulating the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration in the fuel may comprise determining a fuel coking temperature based on the updated dissolved oxygen concentration, comparing the fuel coking temperature to the first fuel temperature, and determining whether a thermal load from the fluid can be deposited into the fuel based on the comparing of the fuel coking temperature to the first fuel temperature.

In various embodiments, modulating the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration in the fuel may further comprise depositing the thermal load from the fluid into the fuel, receiving a second fuel temperature from a second temperature sensor downstream of the heat exchanger, comparing the fuel coking temperature to the second fuel temperature, and determining whether to actuate the valve based on the comparing of the fuel coking temperature to the second fuel temperature.

In various embodiments, depositing the thermal load from the fluid into the fuel may comprise actuating the valve to an open position.

In various embodiments, modulating the flow of the fluid to the heat exchanger based on the dissolved oxygen concentration in the fuel may further comprise actuating the valve to a closed position if the second fuel temperature is greater than the fuel coking temperature.

In various embodiments, a fluid output from the heat exchanger may be directed to a component of the gas turbine engine. In various embodiments, the fluid may comprise oil or air.

In various embodiments, the dissolved oxygen concentration measurement output from the oxygen sensor corresponds to a pre-flight concentration of dissolved oxygen in the fuel.

From a further aspect, a method of fuel-based thermal management for a gas turbine engine as claimed in claim <NUM> is provided. In various embodiments, determining whether the thermal load from the fluid can be deposited into the fuel may comprise determining a fuel coking temperature based on the updated dissolved oxygen concentration, and comparing the fuel coking temperature to the first fuel temperature.

In various embodiments, modulating the flow of the fluid to the heat exchanger may further comprise depositing the thermal load from the fluid into the fuel, receiving a second fuel temperature from a second fuel temperature sensor downstream of the heat exchanger, comparing the fuel coking temperature to the second fuel temperature, and determining whether to adjust a flow rate of the fluid to the heat exchanger based on the comparing of the fuel coking temperature to the second fuel temperature.

In various embodiments, depositing the thermal load from the fluid into the fuel may comprise actuating a valve fluidly coupled between a source of the fluid and the heat exchanger.

In various embodiments, modulating the flow of the fluid to the heat exchanger may further comprise decreasing the flow rate of the fluid if the second fuel temperature is greater than the fuel coking temperature. In various embodiments, decreasing the flow rate of the fluid may comprise actuating a valve fluidly coupled between a source of the fluid and the heat exchanger.

In various embodiments, the fluid may comprise at least one of oil, air, lubricating fluid, fuel, or hydraulic fluid. In various embodiments, the fluid may be output from a component of the gas turbine engine.

A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the following illustrative figures.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosures, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings herein.

The scope of the disclosure is defined by the appended claims rather than by merely the examples described. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option.

Computer-based system program instructions and/or processor instructions may be loaded onto a tangible, non-transitory computer readable medium having instructions stored thereon that, in response to execution by a processor, cause the processor to perform various operations. The term "non-transitory" is to be understood to remove only propagating transitory signals per se from the claim scope and does not relinquish rights to all standard computer-readable media that are not only propagating transitory signals per se.

Disclosed herein is a fuel-based thermal management system which utilizes fuel temperature, flight cycle time, and altitude and/or ambient pressure to determine a threshold fuel temperature for a gas turbine engine and to determine whether a thermal energy load may be deposited into the fuel. The fuel-based thermal management system may increase and/or maximize thermal energy deposited into fuel, while maintaining the fuel below a temperature associated with fuel coking, fuel lacquering, or other deposit formation due to thermal degradation to increase or optimize overall thermodynamic cycle efficiency.

Referring to <FIG>, an exemplary gas turbine engine <NUM> is shown, in accordance with various embodiments. Gas turbine engine <NUM> may generally comprise a compressor section <NUM> where air is pressurized, a combustor <NUM> downstream of the compressor section <NUM> which mixes and ignites the compressed air with fuel and thereby generates hot combustion gases, a turbine section <NUM> downstream of the combustor <NUM> for extracting power from the hot combustion gases. During operation, compressor section <NUM>, combustor <NUM>, and turbine section <NUM> generate heat, which may be carried by fluids communicated throughout gas turbine engine <NUM>. For example, fuel, oil, air, lubricating fluids, hydraulic fluids, and the like may be circulated throughout gas turbine engine <NUM> and may carry a portion of the heat generated during operation. It may be desirable to cool (i.e., remove thermal energy from) these fluids to provide cooling and/or increase thermal efficiency of one or more components of gas turbine engine <NUM>. In various embodiments, and as described in further detail below, fuel injected into combustor <NUM> may be employed as a heat sink to remove (i.e., absorb) thermal loads from one or more fluid(s) communicated through gas turbine engine <NUM>.

Thermal degradation or breakdown (i.e., lacquering, coking, etc.) of fuel can damage fuel system components (e.g., pumps, valves, filters, etc.). Thermal degradation of fuel can be accelerated by an increased concentration of dissolved oxygen (O2) in the fuel. <FIG> illustrates a graph <NUM> comparing fuel-dissolved O2 concentration with fuel coking threshold temperature. Line <NUM> illustrates that as fuel-dissolved O2 concentration decreases the fuel coking threshold temperature (i.e., the temperature at which the fuel degradation occurs) increase.

With reference to <FIG>, an exemplary graphical representation <NUM> of ambient air O2 concentration over a flight profile and altitude over the flight profile is illustrated, according to various embodiments. In graph <NUM>, line <NUM> illustrates ambient air O2 concentration the flight profile and line <NUM> illustrates altitude of the aircraft over the flight profile. As an aircraft climbs to higher altitudes, the temperature, ambient pressure, and partial pressure of O2 in the ambient air are reduced. In various embodiments, the fuel injected into gas turbine engine <NUM> may be stored in a fuel tank that is vented (i.e., opened) such that fuel within the tank is exposed to ambient air. The fuel being exposed to ambient air may allow the ambient air conditions to affect the conditions of fuel in fuel tank. For example, the decreased partial pressure of O2 at higher altitudes may result in less ambient O2 being available to be dissolved into the fuel.

Additionally, as altitude increases and partial pressure of ambient O2 decreases, natural degassing may increase such that a rate of O2 evolution out the fuel increases. In other words, more O2 may be evolved out the liquid fuel and into the ullage space of the fuel tank. Further reduction of ambient air pressure at high-altitude cruise heights (e.g., <NUM>,<NUM> feet (<NUM>,<NUM> meters) or higher) allows for additional increases in the concentration of O2 in the ullage due to the reduced partial pressure of O2 across the surface of the fuel in the fuel tanks. <FIG> illustrates a graph <NUM> comparing fuel-dissolved O2 concentration <NUM> and aircraft altitude <NUM>, as a function of flight time. Line <NUM> illustrates that as flight time (and aircraft altitude <NUM>) increases the fuel-dissolved O2 concentration decreases.

The combined effects of lower ambient air pressure (and, hence lower O2 partial pressure) and the increased degassing of O2 from the liquid fuel may result in a lower O2 content in the liquid fuel. The reduced O2 concentration within the fuel may allow the fuel to absorb more heat before it can reach its thermal degradation limits. Thus, it may be desirable to establish a system and method for determining the amount of oxygen dissolved in the fuel. The amount of oxygen dissolved in the fuel may then be used to determine the amount of thermal energy that can be added to the fuel.

With reference to <FIG>, a schematic block diagram of a fuel-based thermal management system <NUM> is illustrated, in accordance with various embodiments. Fuel-based thermal management system <NUM> may comprise fuel-fluid heat exchange system <NUM>. Fuel-fluid heat exchange system <NUM> receives a fluid <NUM> output from a heat source <NUM>. In various embodiments, heat source <NUM> may comprise one or more components of gas turbine engine <NUM>. Fluid <NUM> may comprise oil, air, lubricating fluid, fuel, hydraulic fluid, or any other aircraft or engine fluid. Fuel-fluid heat exchange system <NUM> further receives fuel <NUM> output from a fuel tank <NUM>. Fuel-fluid heat exchange system <NUM> may be configured to exchange thermal energy (i.e., heat) between fluid <NUM> and fuel <NUM>. In various embodiments, thermal energy is transferred from fluid <NUM> to fuel <NUM> within fuel-fluid heat exchange system <NUM>, such that a temperature of the fluid <NUM> input into fuel-fluid heat exchange system <NUM> is greater than the temperature of the fluid <NUM> output from fuel-fluid heat exchange system <NUM>, and a temperature of the fuel <NUM> input into fuel-fluid heat exchange system <NUM> is less than the temperature of the fuel <NUM> output from fuel-fluid heat exchange system <NUM>. Cooled fluid <NUM> (i.e., the fluid output from fuel-fluid heat exchange system <NUM>) may be directed back to gas turbine engine <NUM>. In various embodiments, cooled fluid <NUM> may be used to cool one or more components of gas turbine engine <NUM>. In various embodiments, cooled fluid <NUM> may directed to, and may cool, an aircraft component other than gas turbine engine <NUM>.

Fuel-fluid heat exchange system <NUM> may be in communication with a controller <NUM>. In various embodiments, controller <NUM> may comprise a full authority digital engine control (FADEC) system. Controller <NUM> may comprise one or more processors configured to implement various logical operations in response to execution of instructions, for example, instructions stored on a non-transitory, tangible, computer-readable medium. The one or more processors can be a general purpose processor, a microprocessor, a microcontroller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof.

Controller <NUM> may include a memory <NUM>. Memory <NUM> may store executable instructions and data to implement control logic of controller <NUM>. Memory <NUM> may comprise a tangible, non-transitory storage medium and may store data used, for example, for trending and prognosis purposes.

Controller <NUM> may be in logical and/or electronic communication with one or more components of fuel-based thermal management system <NUM>. In various embodiments, controller <NUM> may receive data output from fuel-fluid heat exchange system <NUM>, gas turbine engine <NUM>, heat source <NUM>, fuel tank <NUM>, and/or an avionics unit <NUM>. Controller <NUM> may receive data correlating to various engine or aircraft operating conditions, such as, for example, altitude, ambient air temperature, ambient air pressure, dissolved O2 fuel concentration, time in flight cycle, temperature of fuel being input into heat exchanger, temperature of fuel being output from heat exchanger, temperature of the fuel in the fuel tank, speed of the aircraft, Mach number, rotational speed of one or more components of gas turbine engine <NUM>, or any other operating information.

Controller <NUM> may interpret data received from fuel-fluid heat exchange system <NUM>, gas turbine engine <NUM>, heat source <NUM>, fuel tank <NUM>, and/or an avionics unit <NUM> to determine a real-time dissolved O2 concentration within fuel <NUM> and the threshold fuel coking temperature associated with the dissolved O2 concentration.

With reference to <FIG>, additional details of fuel-fluid heat exchange system <NUM> are illustrated according to various embodiments. Fuel-fluid heat exchange system <NUM> may include a heat exchanger <NUM>. Heat exchanger <NUM> is configured to thermally couple the fluid <NUM> output from heat source <NUM> and the fuel <NUM> output from fuel tank <NUM>.

A valve <NUM> (e.g., a flow control valve) may be located upstream of heat exchanger <NUM>. Valve <NUM> may be located between, and fluidly coupled to, heat source <NUM> and heat exchanger <NUM> such that fluid <NUM> flows from an output of heat source <NUM> to an input of valve <NUM>, and from an output of valve <NUM> to an input of heat exchanger <NUM>. Valve <NUM> may be configured to regulate a flow rate of fluid <NUM> to heat exchanger <NUM>. Controller <NUM> may be in operable communication with valve <NUM>. Controller may cause an actuation of valve <NUM> to modulate and/or adjust a flow rate of fluid <NUM> to heat exchanger <NUM>.

A fuel pump <NUM>, located between heat source <NUM> and fuel tank <NUM>, may control the flow of fuel <NUM>. Fuel <NUM> output from heat exchanger <NUM> may flow to a fuel control valve <NUM>. Fuel control valve <NUM> may be configured to regulate the flow of fuel <NUM> to gas turbine engine <NUM>, for example, to combustor <NUM>. In various embodiments, fuel control valve <NUM> may be configured to direct a first portion 230a of the fuel <NUM> output from heat exchanger <NUM> to flow to gas turbine engine <NUM> and to direct a second portion 230b of the fuel back into fuel tank <NUM>.

In various embodiments, the O2-rich ullage of fuel tank <NUM> may be inerted by the a fuel tank inerting system at a determined rate such that fuel tank <NUM> remains inert during flight. During the inerting operation, the O2 is evolved out fuel <NUM> and accepted by the N2-rich environment due to the inerting process. Additional fuel agitation due to operation of fuel pump <NUM> may further enhance the degassing of O2 out of fuel <NUM> within fuel tank <NUM>.

Controller <NUM> receives data output from one or more sensor(s) within fuel-fluid heat exchange system <NUM>, gas turbine engine <NUM>, heat source <NUM>, fuel tank <NUM>, and/or avionics unit <NUM>. Controller <NUM> receives and interprets temperature data from a fluid temperature sensor 260a. The data output from fluid temperature sensor 260a may correspond to the temperature of fluid <NUM> output from heat source <NUM>. Controller receives and interprets temperature data from a fuel temperature sensor 260b upstream of heat exchanger <NUM>. The data output from fuel temperature sensor 260b corresponds to the temperature of fuel <NUM> upstream of heat exchanger <NUM>. Stated differently, the data output from fuel temperature sensor 260b may correspond to the temperature of fuel <NUM> output from fuel tank <NUM> and/or from fuel pump <NUM>.

Controller <NUM> may receive and interpret temperature data from a fuel temperature sensor 260c downstream of heat exchanger <NUM>. The data output from fuel temperature sensor 260c may correspond to the temperature of fuel <NUM> downstream of, and/or output from, heat exchanger <NUM>. Controller <NUM> may receive and interpret altitude data from an altitude sensor <NUM>. In various embodiments, altitude sensor <NUM> may be included in avionics unit <NUM>. Controller <NUM> may receive and interpret ambient pressure data from a pressure sensor <NUM>. In various embodiments, pressure sensor <NUM> may be may be included in avionics unit <NUM>. Controller <NUM> may also receive and interpret flight cycle time (e.g., minutes since take-off) from avionics unit <NUM>.

Controller <NUM> may receive and interpret dissolved O2 concentration data from an O2 sensor <NUM> in communication (e.g., fluid communication) with fuel <NUM>. In various embodiments, O2 sensor <NUM> may be located between fuel tank <NUM> and fuel pump <NUM>. In various embodiments, O2 sensor <NUM> may be located in fuel tank <NUM>. Controller <NUM> may receive data from O2 sensor <NUM> corresponding to the pre-flight concentration of dissolved O2 in fuel <NUM> (e.g., measured when fuel <NUM> is loaded into fuel tank <NUM>). Controller <NUM> may also receive in-flight dissolved O2 concentration data from O2 sensor <NUM> (e.g., continuously during flight).

As described in further detail below, controller <NUM> may use some or all the sensor and/or avionics data to determine a real-time dissolved O2 concentration within fuel <NUM>, the threshold fuel coking temperature associated with the dissolved O2 concentration, and/or the amount of thermal load fuel <NUM> can absorb without exceeding a threshold fuel coking temperature.

With reference to <FIG>, a method <NUM> of fuel-based thermal management of a gas turbine engine is illustrated, in accordance with various embodiments. Method <NUM> may comprise determining a temperature of a fluid output from a heat source (step <NUM>), estimating a real-time dissolved O2 concentration within the fuel (step <NUM>), and modulating a flow of the fluid to a heat exchanger based on the real-time dissolved O2 concentration (step <NUM>).

With combined reference to <FIG> and <FIG>, in various embodiments, step <NUM> may comprise controller <NUM> receiving a fluid <NUM> temperature measurement from, for example, fluid temperature sensor 260a (step <NUM>) and determining whether excess heat is available for deposition into fuel <NUM> (step <NUM>). Stated differently, controller <NUM> may determine whether the temperature of fluid <NUM> is greater than a predetermined temperature threshold. In various embodiments, the predetermined temperature threshold may vary based on flight cycle time. For example, the predetermined temperature threshold may decrease as time since take-off increases. Stated differently, controller <NUM> may compare the temperature of fluid <NUM> to a first predetermined temperature threshold during a flight cycle time of, for example, <NUM> minutes after take-off to <NUM> minutes after take-off, and may compare the temperature of fluid <NUM> to a second predetermined temperature threshold during a flight cycle time of, for example, <NUM> minutes after take-off to <NUM> minutes before landing. If controller <NUM> determines the temperature of fluid <NUM> is not greater than the predetermined temperature threshold, controller <NUM> returns to step <NUM>. If controller <NUM> determines the temperature of fluid <NUM> is greater than or equal to the predetermined temperature threshold, controller estimates the dissolved O2 concentration of fuel <NUM> (step <NUM>).

According to the invention, step <NUM> comprises controller <NUM> receiving a first fuel temperature from, for example, fuel temperature sensor 260b (step <NUM>), a flight cycle time (e.g., minutes since take-off data) from avionics unit <NUM> (step <NUM>), and at least one of an altitude measurement from, for example, altitude sensor <NUM> or an ambient pressure measurement from, for example, pressure sensor <NUM> (step <NUM>). Controller <NUM> estimates the dissolved O2 concentration using the first fuel temperature, flight cycle time, and altitude and/or pressure measurement(s). According to the invention, step <NUM> further includes receiving a dissolved O2 concentration measurement from O2 sensor <NUM> and using the first fuel temperature, flight cycle time, and altitude and/or pressure measurement(s) to update or correct the dissolved O2 concentration measurement received from O2 sensor <NUM>.

A temperature of fuel tank <NUM> can also affect the degassing of O2 from fuel <NUM>. For example, O2 will degas from fuel <NUM> at a faster rate in a hotter fuel environment. In this regard, the O2 dissolved in the fuel in a fuel tank of an aircraft taking off at first temperature will degas faster than O2 in a comparable amount of fuel in a comparable fuel tank of an aircraft taking off at second temperature that is less than first temperature. In this regard, controller <NUM> may receive data related to the ambient air temperature and/or the fuel tank <NUM> temperature at take-off, and may use these data (along with flight cycle time, ambient pressure, etc.) to estimate the real-time O2 concentration in the fuel. After estimating the real-time O2 concentration, controller may modulate the flow of fluid <NUM> to heat exchanger <NUM> based on the real-time O2 concentration (step <NUM>).

In various embodiments, step <NUM> may comprise controller <NUM> determining whether fuel <NUM> can absorb additional heat without exceeding the fuel coking temperature associated with the estimated O2 concentration (step <NUM>). With combined reference to <FIG> and <FIG>, in various embodiments, step <NUM> comprises controller <NUM> determining a fuel coking temperature based on the dissolved O2 concentration of fuel <NUM> (step <NUM>), controller <NUM> comparing the fuel coking temperature to the temperature of fuel <NUM> (e.g., to the first fuel temperature output from fuel temperature sensor 260b) (step <NUM>), and controller <NUM> determining whether a thermal load from fluid <NUM> can be deposited into fuel <NUM> based on the comparison of the fuel coking temperature to the temperature of fuel <NUM> (step <NUM>).

With combined reference to <FIG> and <FIG>, in various embodiments, if controller <NUM> determines fuel <NUM> cannot absorb a thermal load from fluid <NUM> without exceeding the fuel coking temperature, controller <NUM> returns to step <NUM> until controller <NUM> determines fuel <NUM> can absorb additional heat without exceeding the fuel coking temperature. Stated differently, if controller <NUM> determines that the temperature of fuel <NUM> is greater than the fuel coking temperature or is within a predetermined number of degrees from the fuel coking temperature, controller actuates valve <NUM> to prevent or reduce a flow of fluid <NUM> to heat exchanger <NUM>. If controller <NUM> determines fuel <NUM> can absorb heat from fluid <NUM>, controller <NUM> causes heat from fluid <NUM> to be deposited in fuel <NUM> (step <NUM>). In various embodiments, step <NUM> may comprise controller <NUM> actuating valve <NUM>. For example, controller <NUM> may send a signal that causes valve <NUM> to actuate to an open position.

In various embodiments, step <NUM> may further include controller <NUM> receiving a second fuel temperature from, for example, fuel temperature sensor 260c, and comparing the fuel coking temperature to the second fuel temperature (step <NUM>). Controller <NUM> may determine whether to actuate valve <NUM> based on the comparison of the fuel coking temperature to the second fuel temperature. If controller <NUM> determines that the second fuel temperature is greater than the fuel coking temperature, controller <NUM> may actuate valve <NUM> to a closed position that prevents or reduces the flow of fluid <NUM> to heat exchanger <NUM>. (step <NUM>).

Fuel-based thermal management system <NUM> and method <NUM> may provide increased dissolved O2 concentration accuracy by being fully integrated with the aircraft on-board computers for receiving real-time flight data. Increasing the dissolved O2 concentration accuracy may extend the fuel's heat sink capabilities without adding additional heat exchangers or other hardware and/or without increasing the size of the heat exchanger(s). Increasing the accuracy of the real-time detection of dissolved O2 concentration reduces potential unwanted occurrences of damage to fuel system components by reducing their exposure to fuel that is above the fuel's coking temperature for extended periods of time.

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosures. The scope of the disclosures is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more.

In the detailed description herein, references to "various embodiments", "one embodiment", "an embodiment", "an example embodiment", etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic.

Claim 1:
A fuel-based thermal management system (<NUM>) for a gas turbine engine, comprising:
a fuel-fluid heat exchange system (<NUM>) comprising:
a heat exchanger (<NUM>) configured to thermally couple a fluid (<NUM>) received from a heat source (<NUM>) and a fuel (<NUM>) received from a fuel source (<NUM>), and
a valve (<NUM>) configured to regulate a flow of the fluid to the heat exchanger;
a controller (<NUM>) in operable communication with the valve; and
a tangible, non-transitory memory configured to communicate with the controller, the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the controller, cause the controller to perform operations comprising:
determining, by the controller, whether a temperature of the fluid is above a predetermined fluid temperature threshold,
receiving, by the controller, a dissolved oxygen concentration measurement from an oxygen sensor (<NUM>) in communication with the fuel;
receiving, by the controller, a first fuel temperature from a first fuel temperature sensor (260b) upstream of the heat exchanger;
determining, by the controller, an updated dissolved oxygen concentration using the dissolved oxygen concentration measurement received from the oxygen sensor, the first fuel temperature, a flight cycle time, and at least one of an altitude measurement or a ambient pressure measurement; and
modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration.