Patent Description:
The accompanying drawings illustrate various examples of the principles described below. The examples and drawings are illustrative rather than limiting.

In the past, closed loop cooling systems may have been designed without water treatment programs because of a common misconception that water treatment is applicable solely to open water cooling systems. However, cooling water used in a closed loop system should be properly treated to prevent system corrosion, deterioration of components, and loss of heat transfer efficiency. Filtered and de-mineralized water that comes in contact with wetted surfaces of the loop that carries the cooling water should be used, such as reverse osmosis water or deionized water. In addition, chemicals may be added to the water, such as corrosion inhibitors, for example, sodium silicate, sodium hexametaphosphate, and/or a molybdate-based corrosion inhibitor. Further, chemicals may be added to prevent and slow bacterial growth, such as isothiazalone, DBNPA (<NUM>,<NUM>-dibromo-<NUM>-nitrilopropionamide) biocide, and/or hydrogen peroxide silver biocide. Other chemicals may also be used in the cooling water for other purposes, such as adjusting the pH of the cooling water.

With previous systems, concentrations of various chemicals added to the water was measured manually by a technician who sampled the water and either performed on-site measurements or sent samples of the water to a testing laboratory. After chemical analysis results were received from the testing laboratory, if any of the chemicals were not within a predetermined range, the technician manually added the appropriate chemicals to re-balance the system. This type of monitoring and adjustment system is expensive and time consuming. Moreover, if poor system heat transfer performance is detected by system operators between intervals of water sampling testing, irreversible damage may occur to the system.

As described below, an electrochemical sensor may be used to automatically measure the electrical response of the cooling water in real-time to an applied AC voltage, where the electrical response is correlated to the concentration levels of chemicals in the water. Further, if any of the chemicals are not within a predetermined range, appropriate chemicals may be automatically added to the cooling water to re-balance the chemistry. The solution described below eliminates manual testing of the water chemistry, increases the accuracy of water chemistry maintenance, and reduces the cost of the water chemistry maintenance.

The system according to the present invention is defined in claim <NUM>, a corresponding method in claim <NUM>.

<FIG> depicts a diagram of an example electrochemical sensing device 100A capable of performing electrochemical impedance spectroscopy (EIS). The electrochemical sensing device 100A includes a sensor having a first electrode <NUM> and a second electrode <NUM>; and a potentiostat <NUM>. The first electrode <NUM> and the second electrode <NUM> are coupled to the potentiostat <NUM>. A spacing between the first electrode <NUM> and the second electrode <NUM> may be adjustable by a controller <NUM>. For example, in some implementations, one or both of the first and second electrodes <NUM>, <NUM> may be coupled to a translation stage <NUM> controlled by the controller <NUM> that adjusts the spacing. Additionally, a depth at which the first electrode <NUM> and the second electrode <NUM> are inserted into a fluid <NUM> to be tested is also adjustable by the controller <NUM>. For example, in some implementations, the first and second electrodes <NUM>, <NUM> may be coupled to a translation stage <NUM> that adjusts a depth that the first and second electrodes <NUM>, <NUM> are inserted into an enclosure <NUM> holding the fluid <NUM>.

An alternating current (AC) voltage is applied across the electrodes <NUM>, <NUM> by the potentiostat <NUM>, and the resultant electrical response across the first and second electrodes via the fluid is measured, such as complex impedance. The potentiostat <NUM> may apply the AC voltage at various different frequencies, and the response across the electrodes <NUM>, <NUM> at the different frequencies is measured. The electrical response may be determined by measuring a magnitude of a resultant current, and the phase difference between the current and voltage waveforms may be used to determine the real and imaginary components of the impedance across the fluid. By taking measurements at different electrical frequencies, a spectrum vector of frequency-impedance pairs may be obtained. Alternatively, differentiation between components in the fluid may be performed by selecting the appropriate frequency ranges for analysis. The electrical response corresponds to any one or more of the pH and concentration of a single or multiple chemicals in the fluid. In some implementations, the chemicals may include an acidic or alkaline solution, a biocide and/or a corrosion inhibitor.

<FIG> depicts a diagram of another example electrochemical sensing device 100B. The electrochemical sensing device 100B is similar to sensing device 100A depicted in <FIG> but also includes a frequency response analyzer <NUM>. The frequency response analyzer <NUM> is coupled to the potentiostat <NUM> and analyzes the electrical response across the first and second electrodes <NUM>, <NUM> via the fluid at multiple electrical frequencies.

In some implementations, the frequency response analyzer <NUM> may store data, including a baseline spectrum of an electrical response measured by the potentiostat <NUM> when the electrodes <NUM>, <NUM> are inserted in reverse osmosis (RO) water or deionized (DI) water, as RO water and DI water are used in cooling facility water loops. The cooling facility water loop is distinct from the IT water loop, where water in the IT water loop flows directly into the racks and servers. The frequency response analyzer <NUM> may also store a baseline spectrum of the electrical response when the electrodes <NUM>, <NUM> are inserted in RO or DI water with appropriate amounts of each individual chemical used to adjust the chemistry of the fluid used in the cooling system. Additionally, the frequency response analyzer <NUM> may store a baseline spectrum of the electrical response when the electrodes <NUM>, <NUM> are inserted in the fluid when appropriate amounts of all the chemicals to be added to the RO or DI water to obtain the desired final chemistry for the fluid.

Alternatively, the data may be stored in a memory (not shown) that is accessible by the frequency response analyzer <NUM>.

The frequency response analyzer <NUM> determines from the stored baseline spectra and the measured electrical response whether the electrical response is outside a predetermined range. For example, if it is determined that the complex impedance is below a threshold level at a particular frequency or group of frequencies, a first chemical or diluting RO water or DI water may be added. If it is determined that the complex impedance is above a maximum level at the particular frequency or group of frequencies, a different chemical or RO water or DI water may be added.

In some implementations, the fluid to be tested is used in a closed loop cooling system, such as used in cooling computer room air handlers or computer room air conditioners in a data center.

<FIG> depicts a diagram of an example system 200A that determines whether a chemistry of a fluid is to be adjusted. The system includes an electrochemical sensing device 100B as described in <FIG> that is used to test cooling fluid <NUM> in a cooling loop <NUM>. While a single electrochemical sensor is shown in <FIG>, any number of electrochemical sensors may be used. In some implementations, one of the sensors may be placed in a coolant distribution unit where additives are mixed-in to the fluid of the cooling loop <NUM>. In some implementations, multiple sensors may be coupled to a single potentiostat <NUM> or a single frequency response analyzer <NUM>.

The two electrodes <NUM>, <NUM> of the sensor <NUM> are inserted in a fluid <NUM> to be tested in a closed loop system <NUM>. In some implementations, the closed loop cooling system <NUM> may be used, for example, to cool computer room air handlers or computer room air conditioners in a secondary loop in a data center.

<FIG> depicts a graph of example complex impedance measurements as a function of frequency for different cooling fluid chemistries. In the example of <FIG>, a baseline impedance spectrum for a cooling fluid with a desired chemistry is indicated by the line with square data points. The pH level of the cooling fluid was intentionally changed by injecting a dilute acid into the fluid, resulting in the impedance spectrum having data points identified by an 'x,' also shown in <FIG>. Subsequently, the pH level of the cooling fluid was restored to the desired level by injecting a dilute alkaline solution into the cooling fluid. The resulting impedance spectra is shown in <FIG> by the line with the circular data points, which is nearly the same as the baseline spectra, within measurement error. Thus, the measured complex impedance spectrum of the cooling fluid may be used as an indicator of whether the pH level of a fluid is within a desired range. Experiments have also shown that the measured complex impedance spectrum may also be used as an indicator of whether a corrosion inhibitor or biocide level in the cooling fluid are each within their respective desired ranges.

<FIG> depicts a graph of example phase angle difference measurements between a measured current waveform and an applied voltage waveform as a function of frequency for different cooling fluid chemistries. In the example of <FIG>, a baseline spectrum for the phase angle difference for RO water with no added chemicals is shown by the line with square-shaped data points. When <NUM> parts per million (ppm) of a biocide is added to the RO water, the resulting phase angle difference spectrum is indicated by the line with the 'x'-shaped data points. Also, when <NUM> ppm of a corrosion inhibitor is added to the RO water, the resulting phase angle difference spectrum is shown by the line with the circle-shaped data points.

By using these spectra, it is possible to determine how much of which particular additives is outside a predetermined desired range for each additive. For example, in <FIG>, at an applied electrical frequency of <NUM>, the phase angle difference between a measured current waveform and an applied voltage for RO water is approximately -<NUM> degrees, while the phase angle difference for RO water with added biocide is approximately -<NUM> degrees, and the phase angle difference for RO water with added corrosion inhibitor is approximately <NUM> degrees. By using the phase angle difference at multiple frequencies, the contribution of biocide and corrosion inhibitor can be determined for a particular state of the chemistry. Further, an appropriate amount of chemical additives to be added to restore the cooling fluid to the proper concentration levels of the additives may be determined in advance for different states and stored in the frequency response analyzer <NUM> or another memory accessible by the frequency response analyzer <NUM>. This information may be stored as a lookup table, in some other type of database, or as a parametric relationship.

The system according to the invention is able to automatically add the corrective additives to correct the chemistry of the fluid and return it to the appropriate state without manual intervention. <FIG> depicts a diagram of such an example system 200B that determines whether a chemistry of a fluid is to be adjusted. The system 200B includes the elements of system 200A described above and also includes a first reservoir <NUM> containing a first chemical, RO water, or DI water; a first injector <NUM>; a second reservoir <NUM> containing a second chemical, RO water, or DI water; and a second injector <NUM>. The first injector may be controlled by the frequency response analyzer <NUM> or another processor to automatically inject a first amount of the contents of the first reservoir <NUM> into the fluid <NUM> if the electrical response at particular frequencies is above a predetermined range. The second injector is controlled by the frequency response analyzer <NUM> or another processor to automatically inject a second amount of the contents of the second reservoir <NUM> into the fluid if the electrical response at particular frequencies is below the predetermined range. While two reservoirs are shown in the example of <FIG>, any number of different reservoirs having different contents may be used, along with corresponding injectors to enable correction of concentration levels of different chemicals and/or the pH of the fluid.

<FIG> depicts a flow diagram illustrating an example process <NUM> of determining whether a chemistry of the fluid is to be adjusted.

The process begins at block <NUM>, where an alternating current (AC) voltage may be applied across electrodes of an electrochemical sensor by a potentiostat. The AC voltage is applied over multiple electrical frequencies.

At block <NUM>, an electrical response of a fluid in which the electrodes are inserted may be measured by the potentiostat. The measurements are performed over the multiple electrical frequencies at which the AC voltage is applied.

At block <NUM>, based on the measured frequency response, it may be determined by a frequency response analyzer or other processor whether a chemistry of the fluid is to be adjusted. In some implementations, the electrical response may include at least one of a complex impedance and a phase angle difference between a current waveform and a voltage waveform. For example, if the electrical response of the fluid is measured to have a greater complex impedance than expected, a predetermined chemical may be added to the fluid. The amount of chemical may be dependent upon the difference between the measured complex impedance and the expected complex impedance at a given electrical frequency. In some implementations, the fluid may be used in a closed loop cooling system.

<FIG> depicts a flow diagram illustrating another example process <NUM> of determining whether a chemistry of the fluid is to be adjusted.

The process begins at block <NUM> which may be similar to block <NUM> described with respect to process <NUM> of <FIG>. At block <NUM>, a baseline electrical response of the fluid is measured. The baseline may be taken of fluid that has ideal chemistry for comparison to the fluid having a state of unknown chemistry.

At block <NUM>, at least one of a spacing between the electrodes of the sensor and a depth at which the electrodes of the sensor are inserted into the fluid is adjusted to enhance a measurement signal of the electrical response. For example, if the measurement signal of the electrical response is noisy or not as strong as expected, the spacing between the electrodes may be adjusted to be further apart or closer together to obtain a better signal. Alternatively or additionally, the depth at which the electrodes are inserted into the fluid may be adjusted to be deeper or shallower to obtain a better signal.

<FIG> depicts a flow diagram illustrating an example process <NUM> of determining whether a chemistry of the fluid is to be adjusted. In particular, block <NUM> of <FIG> may involve process <NUM>.

The process begins at block <NUM>, where based on a previously recorded baseline electrical response, upon determining that the measured electrical response of the fluid is below a predetermined range at a particular frequency, a portion of a first chemical or diluting water is automatically added into the fluid. The amount of the first chemical or diluting water to be added may be predetermined.

At block <NUM>, based on the baseline frequency response, upon determining that the chemistry of the fluid is above a predetermined range at the particular frequency, a portion of a second chemical or diluting water is automatically injected into the fluid. The amount of the second chemical or diluting water to be added may be predetermined.

Not all of the steps or features presented above are used in each implementation of the presented techniques. Steps may be performed in a different order than presented. The scope of the invention, however, is defined purely by the attached claims.

Claim 1:
A system (200B) comprising:
an electrochemical sensor having two electrodes (<NUM>, <NUM>) insertable in a fluid to be tested, wherein an alternating current (AC) voltage is applied across the two electrodes (<NUM>, <NUM>);
a potentiostat (<NUM>) configured to determine an electrical response across the two electrodes (<NUM>, <NUM>);
a frequency response analyzer (<NUM>) configured to analyze the measured electrical response across multiple frequencies, store a baseline of the electrical response across multiple frequencies, and determine from the stored baseline and the measured electrical response whether the electrical response is outside a predetermined range;
a controller (<NUM>) configured to adjust at least one of a spacing between the electrodes (<NUM>, <NUM>) and a depth to which the electrodes (<NUM>, <NUM>) are inserted into the fluid to enhance a measurement signal of the electrical response;
a first reservoir (<NUM>) containing a first chemical or diluting water, and a first injector (<NUM>), wherein the first injector (<NUM>) is controlled to automatically inject a first amount of the first chemical or diluting water into the fluid if the electrical response is above the predetermined range; and
a second reservoir (<NUM>) containing a second chemical or diluting water, and a second injector (<NUM>), wherein the second injector (<NUM>) is controlled to automatically inject a second amount of the second chemical or diluting water into the fluid if the electrical response is below the predetermined range.