Patent Description:
In accordance with the invention, there is provided: a hybrid evaporative cooler system as recited by claim <NUM>; and a method of controlling a hybrid evaporative cooler system as recited by claim <NUM>.

Some evaporative coolers, such as hybrid evaporative coolers, are able to cool process fluid in either a dry mode or a wet mode. A controller can be used to determine when to switch modes. Switching from dry mode to wet mode can be relatively simple. During operation of an evaporative cooler in dry mode, the fan speed will eventually reach a maximum speed as outdoor air temperature increases. When the supply process water temperature is not met (when the supply process water temperature is above the set point) and the maximum fan speed is reached, a maximum available sensible cooling is reached and the wet mode can be enabled to further cool the process water or other fluid to meet the set point.

However, optimally switching from wet mode to dry mode can be relatively more difficult. This is in part because many variables affect the performance of the evaporative cooler such as the ambient dry bulb and wet bulb temperatures, the entering water temperature, the condition of the cooling coil, the flowrate and/or other properties of the working water. Two approaches are discussed below that are used in the HVAC industry to control the switching from wet to dry mode in hybrid evaporative cooling units.

A first approach uses a fixed outdoor air dry bulb temperature as a set point to switch from wet mode to dry mode. When the outdoor air dry bulb temperature is below the set point, a controller disables the working fluid or recirculation pump to operate the cooler in the dry mode. A second approach uses a fan speed signal to control switching to dry mode. When the fan reaches its minimum speed in wet mode, the controller can change to dry mode. A drawback of these approaches is that in both cases the evaporative cooler may continue operating under wet mode for more time than is actually required, which can cause more water to be used in wet mode than is required.

This disclosure provides a control method and a hybrid evaporative cooler system according to the claims that determines when to switch from wet to dry mode. The hybrid evaporative cooler system includes a controller configured to determine a minimum water temperature that can be produced by the evaporative cooler in dry mode while the evaporative cooler is still in wet mode. The controller determines the minimum process water temperature that can be produced by the cooling coil using a model of the coil of the evaporative cooler. The model may be a theoretical model or an empirical model. In some examples, the controller can use inputs from sensors of the evaporative cooler to determine the minimum water temperature with the model. The inputs can be, for example, process water inlet and outlet temperatures, a process water flow rate, an air inlet temperature, and an air outlet temperature.

Such a system and control method can increase the water efficiency of evaporative coolers, increase the lifetime of wet media, and other mechanical equipment associated with them (e.g. pumps, filters, strainers), decrease water treatment requirements due to the associated reduction in water usage, increase shutdown time for wet media and all mechanical equipment associated with them, which enables more accessibility to conduct preventative and corrective maintenance, and can reduce the total cost of ownership for hybrid evaporative coolers.

In some examples, the system control can be adjusted to account for heat exchanger degradation over time, such as due to scaling, to help ensure that the change from wet to dry mode occurs at an optimal outdoor air temperature through a life of the equipment.

<FIG> illustrates a schematic view of an evaporative cooler system, in accordance with at least one example of this disclosure. The system <NUM> includes an evaporative cooler <NUM>, a controller <NUM>, a cooling coil <NUM>, and a fan <NUM>. The system <NUM> can further include a recirculation pump <NUM>, a process fluid pump <NUM>, a process fluid source <NUM>, an inlet air temperature sensor <NUM>, an outlet air temperature sensor <NUM>, a process fluid flow sensor <NUM>, a process fluid inlet temperature sensor <NUM>, and a process fluid outlet temperature sensor <NUM>. Also shown in <FIG> is process inlet fluid <NUM>, process fluid <NUM>, process outlet fluid <NUM>, inlet air <NUM>, conditioned air <NUM>, outlet air <NUM>, working fluid (recirculated fluid) <NUM>, and an air flow sensor <NUM>.

The evaporative cooler <NUM> can be an evaporative cooler configured to cool process fluid using one or more of working air and working water or fluid. The evaporative cooler <NUM> can be a hybrid evaporative cooler located upstream of the cooling coil <NUM>, such as in examples that includes a wet media. The wet media of the evaporative cooler <NUM> can be of any design such as a membrane air-to-liquid exchanger, falling film exchanger, packed media exchanger, or other wet media design that cools the air stream using evaporative cooling. In some examples, the evaporative cooler <NUM> and the cooling coil <NUM> can be combined in a single heat exchanger.

In some examples, the evaporative cooler <NUM> can be a liquid to air membrane energy exchanger (LAMEE) to transfer heat and moisture between a liquid desiccant and an air stream to condition the temperature and humidity of the air flowing through the LAMEE. The membrane in the LAMEE can be a non-porous film having selective permeability for water, but not for other constituents that form the liquid desiccant. Many different types of liquid desiccants can be used in combination with the non-porous membrane, including, for example, glycols. The non-porous membrane can make it feasible to use desiccants, such as glycols, that had been previously determined to be unacceptable or undesirable in these types of applications. In an example, the membrane in the LAMEE can be semi-permeable or vapor permeable, and generally anything in a gas phase can pass through the membrane and generally anything in a liquid phase cannot pass through the membrane. In an example, the membrane in the LAMEE can be micro-porous such that one or more gases can pass through the membrane. In an example, the membrane can be a selectively-permeable membrane such that some constituents, but not others, can pass through the membrane. It is recognized that the LAMEEs included in the conditioning units disclosed herein can use any type of membrane suitable for use with an evaporative cooler LAMEE.

In an example, the LAMEE or exchanger can use a flexible polymer membrane, which is vapor permeable, to separate air and water. The water flow rate through the LAMEE may not be limited by concerns of carryover of water droplets in the air stream, compared to other conditioning systems. The LAMEE can operate with water entering the LAMEE at high temperatures and high flow rates, and can therefore be used to reject large amounts of heat from the water flow using latent heat release (evaporation).

The cooling fluid circulating through the LAMEE or exchanger can include water, liquid desiccant, glycol, other hygroscopic fluids, other evaporative liquids, and/or combinations thereof. In an example, the cooling fluid is a liquid desiccant that is a low concentration salt solution. The presence of salt can sanitize the cooling fluid to prevent microbial growth. In addition, the desiccant salt can affect the vapor pressure of the solution and allow the cooling fluid to either release or absorb moisture from the air. The concentration of the liquid desiccant can be adjusted for control purposes to control the amount of cooling of the scavenger air or cooling fluid within the LAMEE or exchanger.

Membrane exchangers may have some advantages over other types of evaporative coolers. For example, the LAMEE may eliminate or mitigate maintenance requirements and concerns of conventional cooling towers or other systems including direct-contact evaporation devices, where the water is in direct contact with the air stream that is saturated by the evaporated water. For example, the membrane barriers of the LAMEE inhibit or prohibit the transfer of contaminants and micro-organisms between the air and the liquid stream, as well as inhibiting or prohibiting the transfer of solids between the water and air. The use of LAMEEs along with an upstream or downstream cooling coil can result in a lower temperature of the water leaving the LAMEE and a higher cooling potential. Various configurations of cooling systems having a LAMEE can boost performance in many climates. Higher cooling potential and performance can result in lower air flow and fan power consumption in the cooling system, which is the main source of energy consumption in liquid-cooling systems. In an example in which the heat load is from a data center, this can increase the overall data center cooling system efficiency.

The cooling coil <NUM> can be a heat exchanger configured to exchange heat between the process fluid (<NUM>), the air (<NUM>, <NUM>, <NUM>), and the working fluid <NUM>. In some examples, the cooling coil <NUM> can include tubes and/or fins for transfer of heat between the fluids and can include an evaporative media configured to receive the working fluid <NUM> thereon and to evaporate the working fluid <NUM> into the air (<NUM>, <NUM>) to transfer heat from the process fluid (<NUM>, <NUM>) to the air (<NUM>, <NUM>) through latent heat of vaporization of the working fluid <NUM>.

The controller <NUM> can be a programmable controller, such as a single or multi-board computer, a direct digital controller (DDC), or a programmable logic controller (PLC). In other examples the controller <NUM> can be any computing device, such as a handheld computer, for example, a smart phone, a tablet, a laptop, a desktop computer, or any other computing device including a processor and wireless or wired communication capabilities. Though the connections to the controller are shown as being a single direction, communication can occur in both directions between the controller <NUM> and components connected thereto. The various components can be connected via wire, optical cable, and/or wirelessly. Though the controller <NUM> is discussed as being an electronic controller, the controller <NUM> can be other types of controllers, such as a pneumatic controller.

The fan <NUM> can be one or more fans or pumps configured to motivate air to flow. The fan <NUM> can be an axial, centrifugal (plug), or the like. The fan <NUM> is located in or connected to an air tunnel or chamber either upstream or downstream of the cooling coil <NUM>.

The recirculation pump <NUM> can be a fluid pump (such as a water or glycol pump) configured to pump fluid to the evaporative cooler <NUM> for wetting of the evaporative media of the evaporative cooler <NUM>. In some examples, the pump <NUM> can be connected to a basin, drain pan, tank, or sump where run-off from the coil can be collected. In some examples, the evaporative cooler <NUM> can receive fluid from a tank in a gravity-fed arrangement. In some examples, the recirculation pump <NUM> can be a positive displacement or rotary pump, such as a centrifugal pump configured to pump fluid to a top portion of evaporative cooler <NUM> for distribution across and down the evaporative cooler <NUM>. In other examples, the fluid can be pumped to other portions of the evaporative cooler <NUM> for distribution. In some examples, the recirculation pump <NUM> can be electrically connected to the controller <NUM> such that the controller can control operation of the recirculation pump <NUM>, such as whether the recirculation pump <NUM> is on or off and at what speed the recirculation pump <NUM> operates.

Similarly, the process fluid pump <NUM> can be a fluid pump (such as a water or glycol pump) configured to pump the process fluid <NUM> from the source <NUM> to the cooling coil <NUM> and back to the source. The circuit including the source <NUM>, the cooling coil <NUM>, and the process fluid pump <NUM> can include various other components, such as valves, strainers, air separators, expansion tanks, other heat exchanges, or the like. The process fluid pump <NUM> can be a positive displacement or rotary pump, such as a centrifugal pump configured to pump water through the process fluid circuit. In some examples, the process fluid pump <NUM> can be electrically connected to the controller <NUM> such that the controller can control operation of the process fluid pump <NUM>, such as whether the process fluid pump <NUM> is on or off and at what speed the process fluid pump <NUM> operates.

The process fluid source <NUM> can be a piece of equipment configured to use the process fluid <NUM>. For example, the process fluid source <NUM> can be a cooling coil of an air tunnel, computer room air conditioning (CRAC) unit, chilled beam, fan coil, or the like. The process fluid source <NUM> can receive chilled or cooled fluid from the process fluid outlet <NUM>, transfer heat to the process fluid <NUM> and discharge the process fluid <NUM> to the process fluid pump <NUM>.

The inlet air temperature sensor <NUM> can be located in the inlet air stream <NUM> and can be configured to produce an inlet temperature signal based on a dry bulb and/or a wet bulb temperature of the inlet air stream <NUM>. In some examples, the air temperature sensor <NUM> can measure (or can effectively measure) an ambient air temperature. The inlet air temperature sensor <NUM> can be electrically connected to controller <NUM> and configured to transmit the inlet temperature signal thereto. Each of the inlet air temperature sensor <NUM> and the outlet air temperature sensor <NUM> can be any type of temperature sensor, such as a thermistor, thermocouple, resistance temperature detector, a wetted wick, a chilled mirror sensor, a capacitive humidity sensor, a resistive humidity sensor, or the like.

Similarly, the outlet air temperature sensor <NUM> can be located in the outlet air stream <NUM> and can be configured to produce an outlet temperature signal based on a dry bulb and/or a wet bulb temperature of the outlet air stream <NUM>. The outlet air temperature sensor <NUM> can be electrically connected to controller <NUM> and configured to transmit the outlet temperature signal thereto.

The process fluid flow sensor <NUM> can be connected to the process fluid circuit, such as upstream of the cooling coil <NUM> near the process fluid inlet <NUM>. The process fluid flow sensor <NUM> can be any type of flow or pressure sensor, such as a differential pressure sensor, a Coriolis sensor, a paddle sensor, a paddle wheel sensor, or the like. The process fluid flow sensor <NUM> can be configured to produce a flow signal based on a flow rate of the process fluid <NUM> through the cooling coil <NUM>. The process fluid flow sensor <NUM> can be connected to the controller <NUM> to transmit the process fluid flow signal thereto.

The process fluid inlet temperature sensor <NUM> can be connected to the process fluid circuit, such as upstream of the cooling coil <NUM> in the process fluid inlet <NUM>. The process fluid inlet temperature sensor <NUM> can be configured to produce a process fluid inlet temperature signal based on a temperature of the process fluid <NUM> at the process fluid inlet <NUM> to the cooling coil <NUM>. The process fluid inlet temperature sensor <NUM> can be connected to the controller <NUM> to transmit the process fluid inlet temperature signals thereto. The process fluid inlet temperature sensor <NUM> and the process fluid outlet temperature sensor <NUM> can be any type of fluid temperature sensor, either in a thermowell, coupled to a pipe of the process fluid circuit, or in direct contact with the process fluid, such as a thermistor, thermocouple, resistance temperature detector, or the like.

The process fluid outlet temperature sensor <NUM> can be connected to the process fluid circuit, such as downstream of the cooling coil <NUM> in the process fluid outlet <NUM>. The process fluid outlet temperature sensor <NUM> can be configured to produce a process fluid outlet temperature signal based on a temperature of the process fluid <NUM> at the process fluid outlet <NUM> of the cooling coil <NUM>. The process fluid outlet temperature sensor <NUM> can be connected to the controller <NUM> to transmit the process fluid outlet temperature signal thereto.

In operation of the evaporative cooler in a first wet mode, which can be referred to as an adiabatic mode, the process fluid pump <NUM> can be on and pumping fluid through the cooling coil <NUM> in a cooling coil closed circuit. The recirculation pump <NUM> can be on and pumping fluid to evaporative media of the evaporative cooler <NUM> in an evaporative cooler closed circuit. The fan <NUM> can be on and delivering an air stream to the evaporative cooler <NUM>, which can follow to the cooling coil <NUM>. The working fluid <NUM> can be evaporated into the inlet air <NUM> to condition the inlet air <NUM> adiabatically to create conditioned air <NUM>. The conditioned air <NUM> can have a reduced dry-bulb temperature with a higher humidity level, while the overall enthalpy can remain constant where the conditioned air <NUM> can have a larger sensible cooling capacity than the inlet air <NUM>.

The conditioned air <NUM> can be delivered to the cooling coil <NUM> where the conditioned air <NUM> can receive heat from the process fluid <NUM> to cool the process fluid <NUM> via the cooling coil <NUM> to provide the process fluid <NUM> at the process fluid outlet <NUM> with a temperature at the process fluid set point or target. When the controller <NUM> determines that the evaporative cooler <NUM> can be switched from wet mode to dry mode, the controller can send signals to disable the recirculation pump <NUM> and can adjust a speed of the fan <NUM>, as necessary, to maintain the process fluid set point or target.

As shown within the controller <NUM>, the controller <NUM> performs a step <NUM> to determine whether the minimum supply water temperature (SWTmin) is less than the process fluid set point (PCW set point), where the SWTmin is the lowest temperature of process fluid that the cooling coil <NUM> can deliver at a given ambient temperature or a given inlet air temperature while operating in the dry mode. Such a calculation can be performed when a maximum air flow rate that can be received by the cooling coil <NUM> is known. The "process fluid set point" or "Process Conditioned Water (PCW) set point" is also referred to herein as the "leaving process fluid temperature set point. " This temperature set point is the target or desired temperature of the fluid leaving (e.g., at the fluid outlet of) the cooling coil <NUM>. The inlet air temperature can be delivered to the controller via the inlet air temperature sensor <NUM>, as discussed above. In examples, where ambient temperature is used to calculate SWTmin, an additional outdoor or ambient temperature sensor can be used.

When it is true that the SWTmin is less than the process fluid temperature set point, the controller enables dry mode at step <NUM> (in one example by locking out or disabling the evaporative cooler <NUM>), because the controller <NUM> has determined that dry mode should provide the required process water temperature at the set point. When it is not true that the SWTmin is less than the process fluid set point, the controller <NUM> maintains wet mode at step <NUM>. By including an ability to use a dry mode whenever possible, the system <NUM> can help to minimize the fluid usage, helping to save water. The determination of when to switch to dry mode by the controller <NUM> is discussed in further detail below.

In some examples, the controller <NUM> can calculate the SWTmin when the system <NUM> is operating in the dry mode (or when the evaporative cooler <NUM> is not enabled) and when it is not true that the SWTmin is less than the process fluid set point, the controller <NUM> can maintain dry mode at step <NUM> when the process fluid outlet temperature signal from the temperature sensor <NUM> indicates that the temperature of the process fluid <NUM> at the process fluid outlet <NUM> of the cooling coil <NUM> is actually equal or below the PCW set point. In such a circumstance, the controller <NUM> can update the theoretical model for determining the SWTmin.

In some examples, the controller <NUM> can include a theoretical model to predict the SWTmin that can be achieved by the system <NUM> in dry mode for an ambient (outdoor) or inlet air temperature under any available operating condition. For example, the controller <NUM> can predict the SWTmin at a maximum speed of the fan <NUM> and/or at a minimum or maximum air flow rate. In some examples, the controller <NUM> can predict the SWTmin at any flow rate measured by the air flow sensor <NUM>. The theoretical model can be a computational model using heat transfer and fluid mechanics equations to determine performance of the cooling coil <NUM> at certain conditions.

The controller <NUM> can additionally or alternatively include an empirical model. Such a model can be a performance model of the cooling coil <NUM> developed based on measurements taken in a lab and/or during operation of the cooling coil <NUM> or a similar cooling coil of another system. In some examples, the empirical model can be updated during operation of the cooling coil <NUM> in dry mode.

The controller <NUM> can use the empirical model and/or the theoretical model and one or more inputs to determine the SWTmin. For example, the controller <NUM> can use data from the process fluid inlet temperature signal, the process water outlet temperature signal, the inlet air temperature signal, the outlet air temperature signal, an air flow rate signal (discussed below) and/or the process water flow signal input the data into the theoretical model and/or the empirical model and output the SWTmin. Once the controller <NUM> has calculated the SWTmin, the controller <NUM> can determine whether dry mode operation can provide process water with a leaving temperature that meets the set point or target temperature.

The process water inlet temperature signal can be received at the controller <NUM> from the process water inlet temperature sensor <NUM>; the process water outlet temperature signal can be received at the controller <NUM> from the process water outlet temperature sensor <NUM>; the inlet air temperature signal can be received at the controller <NUM> from the inlet air temperature sensor <NUM>; the outlet air temperature signal can be received at the controller <NUM> from the outlet air temperature sensor <NUM>; and, the process water flow signal can be received at the controller <NUM> from the process water flow sensor <NUM>.

In some examples, only the air side inputs (air temperatures) can be used to determine the SWTmin. In some examples, only the water side inputs (process fluid temperatures and/or flowrate) can be used to determine the SWTmin. In some examples, a combination of both air and process fluid signals can be used. In one example, the inlet air temperature signal, the inlet process fluid temperature signal, and/or the outlet process fluid temperature signal can be used with the theoretical model and/or the empirical model to determine the SWTmin.

In some examples where it is desired to use a controller requiring less computing power, a lookup table or a regression correlation can be created based on a theoretical model and/or an empirical model and the table or correlation can be included in the controller <NUM>. The controller <NUM> can then use one or more inputs to lookup the SWTmin for making the determination of when to switch to dry mode.

Because thermal performance of the cooling coil <NUM> can change over time due to operational factors (e.g. fouling, corrosion), the actual performance of the cooling coil <NUM> can deviate from the theoretical and/or empirical model developed for a clean coil. To correct for performance degradation over the lifetime of the cooling coil <NUM>, the thermal performance of the cooling coil <NUM> can be updated. The updates to the theoretical and/or empirical models can be done based on time and/or based on data saved from each of the signals, where the signals can be stored as data and can be used to measure thermal performance of the cooling coil <NUM> in various conditions. The data and thermal performance can be used to update lookup tables, and can be updated based on artificial neural networks and deep learning tools that account for the degradation in thermal performance of the cooling coil <NUM>.

Further, the data can be collected from one or more of the sensors, such as the inlet air temperature sensor <NUM>, the outlet air temperature sensor <NUM>, the process fluid flow sensor <NUM>, the process fluid inlet temperature sensor <NUM>, and/or the process fluid outlet temperature sensor <NUM>, and/or any other sensors discussed above or below. The data from the sensors can be used by artificial neural networks and/or deep learning tools to update the model used to determine the SWTmin.

<FIG> illustrates a schematic view of an evaporative cooler system 100A, in accordance with at least one example of this disclosure. Any of the components of the system 100A can be included in the systems discussed above and below.

The system 100A includes an evaporative cooler <NUM>, a controller <NUM>, a cooling coil <NUM>, and a fan <NUM>. The system 100A can further include a recirculation pump <NUM>, a process fluid pump <NUM>, a process fluid source <NUM>, an inlet air temperature sensor <NUM>, an outlet air temperature sensor <NUM>, a process fluid flow sensor <NUM>, a process fluid inlet temperature sensor <NUM>, and a process fluid outlet temperature sensor <NUM>. Also shown in <FIG> is process inlet fluid <NUM>, process fluid <NUM>, process outlet fluid <NUM>, inlet air <NUM>, conditioned air <NUM>, outlet air <NUM>, working fluid (recirculated fluid) <NUM>, and an air flow sensor <NUM>.

The system 100A can be similar to the system <NUM> of <FIG>, except that circuits of the working fluid <NUM> and the process fluid <NUM> can be connected (as opposed to adiabatic mode where the working fluid <NUM> and the process fluid <NUM> circuits can be isolated) for serial delivery of fluid from the cooling coils <NUM> to the evaporative cooler <NUM>. In some examples, the system 100A can be the same as the system <NUM> where the changes in fluid flow are performed by valves in one or more fluid circuits.

In operation of the system 100A in a second wet mode, which can be referred to as an evaporative mode, the process fluid pump <NUM> can be on and pumping fluid through the cooling coil <NUM>. The process fluid <NUM> can be cooled by the conditioned air <NUM> to create cooled process fluid <NUM>. The cooled process fluid <NUM> can then be delivered to the evaporative cooler <NUM>. The working fluid <NUM> (which can be the same as the process fluid <NUM>) can be delivered to the evaporative cooler <NUM> to be passed over the evaporative cooler <NUM>, such as media of the evaporative cooler <NUM>, where a portion of the process fluid <NUM> can be evaporated into the inlet air <NUM> to cool the inlet air <NUM> to create the conditioned air <NUM> (as described above with respect to system <NUM>) and the process fluid <NUM> can be cooled by the evaporative cooler. The process fluid <NUM> leaving the evaporative cooler <NUM> can be delivered to the process fluid outlet <NUM> to provide the process fluid <NUM> at a temperature meeting the process fluid set point or target so that the process fluid <NUM> can be then delivered to the source <NUM>. In some examples of the evaporation wet mode, depending on operating condition, a portion of the fluid leaving the cooling coil <NUM> can be mixed with fluid leaving the evaporative cooler <NUM> for delivery to the source <NUM> at a temperature at the process fluid set point or target.

On the air side, the fan <NUM> can be on and delivering an air stream to the evaporative cooler <NUM> and the cooling cool <NUM>. The working fluid <NUM> can cool the inlet air <NUM> to create the conditioned air <NUM>, which can be delivered to the cooling coil <NUM> for cooling of the process fluid <NUM>.

In the evaporative wet mode, when the controller <NUM> determines that the evaporative cooler <NUM> can be switched from wet mode to dry mode, the controller can send signals to the process fluid pump <NUM> and valves of the circuits to direct fluid flow through only the cooling coil <NUM> and can adjust a speed of the fan <NUM>, as necessary, to maintain the process fluid set point or target. As shown within the controller <NUM>, the controller <NUM> can perform a step <NUM> to determine whether the SWTmin is less than the PCW set point to determine when the switch to dry mode should be made, as discussed above with respect to <FIG>.

<FIG> illustrates a schematic view of an evaporative cooler system 100B, in accordance with at least one example of this disclosure. Any of the components of the system 100A can be included in the systems discussed above and below.

The system 100B includes an evaporative cooler <NUM>, a controller <NUM>, a cooling coil <NUM>, and a fan <NUM>. The system 100B can further include a recirculation pump <NUM>, a process fluid pump <NUM>, a process fluid source <NUM>, an inlet air temperature sensor <NUM>, an outlet air temperature sensor <NUM>, a process fluid flow sensor <NUM>, a process fluid inlet temperature sensor <NUM>, and a process fluid outlet temperature sensor <NUM>. Also shown in <FIG> are a process inlet fluid <NUM>, process fluid <NUM>, process outlet fluid <NUM>, an inlet air <NUM>, conditioned air <NUM>, outlet air <NUM>, working fluid (recirculated fluid) <NUM>, a pre-cooling coil <NUM>, and an air flow sensor <NUM>.

The system 100B can be similar to the system <NUM> of <FIG>, except that the system can include the pre-cooling coil <NUM>. The pre-cooling coil <NUM> can be a heat exchanger configured to exchange heat between the fluid and air. In some examples, the pre-cooling coil <NUM> can include tubes and/or fins for transfer of heat between the fluids. The pre-cooling coil <NUM> can be configured to receive working fluid <NUM> (and/or process fluid) from the recirculation pump <NUM> (and/or from the process fluid pump <NUM>) for passing through tubes of the pre-cooling coil <NUM> such that the working fluid <NUM> can receive heat sensibly from air delivered from the fan <NUM>. The air can be conditioned (such as cooled) by the pre-cooling coil <NUM> and can be delivered as pre-cooled air to the evaporative cooler <NUM> to increase a total cooling capacity of the system 100B. In some examples, fluids other than the working fluid <NUM> can be delivered to the pre-cooling coil. In some examples, the working fluid <NUM> leaving the pre-cooling coil can be delivered to the evaporative cooler <NUM>.

The system 100B can also include an air flow sensor <NUM>, which can be a sensor configured to measure a volumetric (or mass) flow rate of air through the pre-cooling coil <NUM>, the evaporative cooler <NUM>, and the cooling coil <NUM>. The fan flow sensor can be connected to the controller <NUM> and configured to deliver an air flow rate signal to the controller <NUM> based on a detected flow rate of the air stream (such as at the inlet air <NUM>, the conditioned air <NUM>, and/or the outlet air <NUM>). In some examples, the air flow rate signal can be used by the controller <NUM> to determine the SWTmin. Though the air flow sensor <NUM> is shown as between the pre-cooling coil <NUM> and the evaporative cooler <NUM>, the air flow sensor <NUM> can be positioned anywhere in the air stream (<NUM>, <NUM>, <NUM>). Though not discussed with respect to the systems <NUM> and 100A, either system can include the air flow sensor <NUM>, as shown in <FIG> and <FIG>.

In operation of the evaporative cooler in a third wet mode, which can be referred to as a super-evaporative mode, the process fluid pump <NUM> can be on and pumping fluid through the cooling coil <NUM> where the process fluid <NUM> can be cooled by the conditioned air <NUM> to provide the process fluid <NUM> at the process fluid outlet <NUM> with a temperature at the process fluid set point or target where the process fluid <NUM> can be then delivered to the source <NUM>.

In some examples, a portion of the process fluid from the cooling coil <NUM> can be delivered to the evaporative cooler <NUM> and can be evaporated into the inlet air stream <NUM> to create the conditioned air <NUM>. In some examples, the recirculation pump <NUM> can provide all or some of the flow to the evaporative cooler <NUM>. Some or all of the fluid leaving the evaporative cooler <NUM> can provide the process fluid <NUM> at the process fluid outlet <NUM> (mixed with fluid leaving the cooling coil <NUM> in some examples) with a temperature at the process fluid set point or target, where the process fluid <NUM> can be then delivered to the source <NUM>. In other examples, some or all of the fluid leaving the evaporative cooler <NUM> can be delivered to the pre-cooling coil <NUM>. The pre-cooling coil can use fluid from the evaporative cooler <NUM> and/or the recirculation pump <NUM> to pre-cool the inlet air <NUM>. Fluid leaving the pre-cooling coil <NUM> can be delivered to the process fluid outlet <NUM> (and can be mixed with fluid leaving the cooling coil <NUM> and/or the evaporative cooler <NUM> in some examples) with a temperature at the process fluid set point or target, where the process fluid <NUM> can be then delivered to the source <NUM>. On the air side, the fan <NUM> can be on and delivering an air stream to the pre-cooling coil <NUM>, the evaporative cooler <NUM>, and then to the cooling cool <NUM>.

When the controller <NUM> determines that the evaporative cooler <NUM> can be switched from wet mode to dry mode, the controller can send signals to disable the recirculation pump <NUM> and can adjust a speed of the fan <NUM>, as necessary, to maintain the process fluid set point or target. During such a switch, bypass dampers can be used to divert the airstream to bypass the pre-cooling coil <NUM> to reduce unnecessary air-side pressure drop and therefore save fan motor power. As shown within the controller <NUM>, the controller <NUM> can perform a step <NUM> to determine whether the SWTmin is less than the PCW set point to determine when the switch to dry mode should be made, as discussed above with respect to <FIG>.

<FIG> illustrates a schematic view of an evaporative cooler system <NUM>, in accordance with at least one example of this disclosure. In some examples, any of the components of the evaporative cooler system <NUM> can be included in any of the systems <NUM>, 100A, and 100B discussed above. In some examples, instead of switching entirely between the distinct modes of operation for the adiabatic mode and evaporation mode, the system <NUM> can include a blended mode operation. Such a blended mode operation can include blending the adiabatic and evaporative modes together in differing ratios to control the mode transition and maintain optimal water efficiency. The transition between modes can involve significant changes in the operational state of the unit and can be difficult to control or avoid fluctuations in supply water temperature. The transition from the adiabatic mode to the evaporative mode can involve a sudden mixing of water or a sudden increase in cooling power as the evaporative coolers begin to receive warmer water and the evaporation rate increases significantly. This can result in the fan speed modulating from full speed (at the limit of the adiabatic mode) to a low speed in the evaporative mode to prevent over cooling. In examples where multiple cooling units are used, as the cooling load on the system <NUM> increases (when fewer conditioning units are selected for a given facility heat load), system <NUM> can spend minimal time in the adiabatic mode and switch to the evaporative mode where it can develop sufficient cooling capacity. The evaporative mode can be less efficient in terms of water usage, relative to the adiabatic mode, and water consumption can increase.

Operating in the blended mode can include monitoring and varying the ratio of the return process water from the cooling coil (RC) <NUM> into first and second sections of a water storage tank <NUM>, and the first and second sections can be at least partially separated from one another. The blended mode operation can involve varying distribution of return process water from the cooling coil (RC) <NUM> into two pump suction bays of the tank <NUM> and corresponding pump suction inlets (for example of pumps <NUM> and <NUM> of <FIG>) and consequently varying a mix ratio of warm and cold water into the pumped cold water supply (to the heat load <NUM>) via the pump <NUM> and into the pumped recirculated water (to the evaporative cooler <NUM>) via the pump <NUM>. Valves (such as the <NUM>-way valve <NUM>) can control the proportion of hot return water going into the suction inlets of the pumps <NUM>, <NUM>, respectively (P-<NUM>, P-<NUM>). Though the system <NUM> shows a <NUM>-way valve to control proportioning, two <NUM>-way valves can be used in other examples to control the proportioning of hot return water going into the suction inlets of the pumps <NUM>, <NUM>, respectively (P-<NUM>, P-<NUM>).

The system <NUM> can be controlled to maintain a supply water temperature set point under varying ambient air conditions or varying cooling loads. The system <NUM> accomplishes this by varying the mix ratio of EC discharge water (into a back portion of the tank <NUM>) and RC return water into the pump suction bays. For example, if the system <NUM> enters the wet mode of operation in the equivalent of the adiabatic mode (<NUM>% of RC return water into the first pump suction and <NUM>% evaporative cooler discharge into the second pump suction) and the ambient outdoor air conditions rise (increased temperature or humidity), the supply water temperature delivered by the first pump <NUM> (P-<NUM>) may rise above the set point. In this case, a controller of the system <NUM> can begin to modulate the RC return valves (such as the <NUM>-way valve <NUM>) to divert a portion of the return water into the second pump suction bay, which can cause an equivalent portion of cold EC discharge water to flow into the first pump suction bay, lowering the supply water temperature to the set point. The mix ratio can be continuously modulated by the controller to maintain supply water temperature set point in response to varying ambient conditions and load. At peak ambient conditions or peak cooling loads the system may operate in the equivalent of the evaporative mode (<NUM>% of RC return water into P-<NUM> suction, and P-<NUM> suction being supplied essentially all by EC discharge water).

Such a blended wet mode can be interrupted when the controller (such as the controller <NUM> of <FIG>) determines that the SWTmin is less than the PCW set point of the system <NUM> when operating in the blended mode. In some examples, the controller <NUM> can make this determination by comparing the SWTmin to the PCW set point at each possible operating point of the blended mode at any given ambient temperature of the system <NUM>.

Examples according to the present application can include a method of operating the system <NUM> in a blended mode at particular operating conditions between the adiabatic mode and the evaporative mode, where operating the conditioning system in the blended mode comprises distributing a first cooling fluid exiting the recovery coil between the first and second portions of the tank in a ratio such that a mix of the first and second cooling fluids in the supply water delivered to the heat load is at a temperature at or near a set point temperature for the conditioning system. Operating in the blended mode can include continuously monitoring and varying a ratio of the first cooling fluid distributed to the first and second portions of the tank to maintain the temperature of the supply water at or near the set point temperature.

<FIG> illustrates a schematic view of a method <NUM>, in accordance with at least one example of this disclosure. The steps or operations of the method <NUM> are illustrated in a particular order for convenience and clarity; many of the discussed operations can be performed in a different sequence or in parallel without materially impacting other operations. The method <NUM> as discussed includes operations performed by multiple different actors, devices, and/or systems. It is understood that subsets of the operations discussed in the method <NUM> can be attributable to a single actor, device, or system could be considered a separate standalone process or method.

The method <NUM> can begin at step <NUM>, where the fan can be operated to deliver an airstream. For example, the fan <NUM> can be operated by the controller <NUM> to deliver the inlet air stream <NUM>. At step <NUM>, the recirculation pump can be operated to provide a working fluid. For example, the recirculation pump <NUM> can be operated by the controller <NUM> to provide the working fluid <NUM> to the cooling coil <NUM>.

At step <NUM>, the cooling coil can be located in the airstream and can receive a process fluid from a source. For example, the cooling coil <NUM> can be located in the airstream (<NUM>, <NUM>) and can receive the process fluid <NUM> at the process fluid inlet <NUM> from the source <NUM>. At step <NUM>, the process fluid can be cooled in a wet mode by the evaporative cooler and by the cooling coil using the working fluid from the recirculation pump and the airstream. For example, the airstream <NUM> can be conditioned by the evaporative cooler <NUM> and the working fluid <NUM> from the recirculation pump <NUM>. Then, while the system <NUM> is in a wet mode, the process fluid <NUM> is cooled by the cooling coil <NUM> using the conditioned air <NUM>.

At step <NUM>, a leaving process water temperature set point is received at a controller. For example, a leaving process water temperature set point can be received at the controller <NUM>. At step <NUM>, a minimum supply water temperature deliverable by the cooling coil in the dry mode is determined based on a coil performance model. For example, a minimum supply water temperature deliverable by the cooling coil <NUM> in the dry mode (SWTmin) can be determined based on a coil performance model by the controller <NUM>. Then, at step <NUM>, the system is switched from the wet mode to the dry mode when the leaving process water temperature set point is greater than the minimum supply water temperature. For example, the system <NUM> can be switched from the wet mode to the dry mode when the leaving process water temperature set point (PCW set point) is greater than the minimum supply water temperature (SWTmin).

Claim 1:
A hybrid evaporative cooler system (<NUM>) for cooling a process fluid (<NUM>), the hybrid evaporative cooler system (<NUM>) comprising:
a fan (<NUM>) configured to produce an airstream, the fan being located in or connected to an air tunnel or chamber;
an evaporative cooler (<NUM>) located upstream or downstream of the fan (<NUM>);
a cooling coil (<NUM>) located upstream or downstream of the fan (<NUM>), and located downstream of the evaporative cooler (<NUM>), and configured to receive the process fluid (<NUM>) from a source (<NUM>); and
a controller (<NUM>) configured to operate the hybrid evaporative cooler system (<NUM>) in a wet mode, in which the evaporative cooler (<NUM>) is activated to receive a working fluid (<NUM>) and to condition the airstream and in which the cooling coil (<NUM>) cools the process fluid (<NUM>) using the airstream, and configured to operate the evaporative cooler system (<NUM>) in a dry mode in which the evaporative cooler (<NUM>) is deactivated and in which the cooling coil (<NUM>) cools the process fluid (<NUM>) using the airstream, the controller (<NUM>) further configured to:
receive a temperature set point (<NUM>) for process fluid leaving the cooling coil (<NUM>);
determine a minimum fluid temperature based on a coil performance model (<NUM>), wherein the minimum fluid temperature is the lowest temperature of the process fluid (<NUM>) that the cooling coil (<NUM>) can deliver at a given ambient temperature or a given inlet air temperature while operating in the dry mode, and wherein the coil performance model (<NUM>) is configured to predict the minimum fluid temperature that can be achieved by the hybrid evaporative cooler system in dry mode for any given ambient temperature or any given inlet air temperature under any available operating condition; and
operate the hybrid evaporative cooler system in the dry mode on condition that the temperature set point is greater than the minimum fluid temperature (<NUM>).