Cooling Towers: Operating Principles and Systems

Cooling towers are found in a wide range of sizes
and configurations

The huge, perfectly shaped cylindrical towers stand tall amidst a landscape, with vapor billowing from their spherical, open tops into the blue sky. Such an image usually provokes a thought related to nuclear power or a mysterious energy inaccessible to the millions of people who drive by power plants every day. In reality, cooling towers – the hyperboloid structures most often associated with the aforementioned nuclear power plants – are essential, process oriented tools that serve as the final step in removing heat from a process or facility. The cooling towers at power plants serve as both an adjuster of a control variable essential to the process and also as a fascinating component of the process behind power creation. The importance and applicability of cooling towers is extensive, making them fundamentally useful for industrial operations in power generation, oil refining, petrochemical plants, commercial/industrial HVAC, and process cooling.

In principle, a cooling tower involves the movement of water through a series of different parts or sections to eventually result in the reduction of its heat content and temperature. Water heated by the process operation is pumped through pipes to reach the tower, and then gets sprayed through nozzles or other distribution means onto the ‘fill’ of the tower, reducing the flow of water to appropriate levels; this maximizes the amount of surface area for contact between water and air. Electric motor driven fans pull air into the tower, and when the air meets the water, a percentage of the water evaporates, carrying heat from the water to the air and resulting in the water being cooled. The cooled water then gets transferred back to the process-related equipment, and absorbs heat again, allowing for the cycle to repeat. The process and associated dispersion of heat allows for the cooling tower to be classified as a heat rejection device, resulting in waste heat being rejected to the atmosphere. Towers depend on either evaporation to remove the process heat (open loop) or solely on air (closed loop), without evaporation, to reduce the water temperature.

Thanks to their range of applications, cooling towers vary in size from the monolithic structures utilized by power plants to small rooftop units. Removing the heat from the water used in cooling systems allows for the recycling of the heat transfer fluid back to the process or equipment that is generating heat. This cycle of heat transfer enables heat generating processes to remain stable and secure. The cooling provided by an evaporative tower allows for the amount of supply water to be vastly lower than the amount which would be otherwise needed. No matter whether the cooling tower is small or large, the components of the tower must function as an integrated system to ensure both excellent performance and longevity of use. Additionally, understanding elements which drive performance - variable flow capability, potential HVAC ‘free cooling’, the splash type fill versus film type fill, drift eliminators, nozzles, fans, and driveshaft characteristics - is essential to the success of the cooling tower and its use in both industrial and commercial settings.

So, the next time an imposing tower cracks the horizon underneath a pillar of drifting vapor, imagine all the components inside working together in a beautifully aligned system towards a common industrial goal. Such is the ingenuity of technology.

Analynk Wireless manufactures wireless communications equipment that can be used to establish radio connections between remote located cooling tower monitoring equipment and central control stations. Fan motor current, air or fluid flow and temperature characteristics, and outdoor air conditions are just some of the cooling tower performance parameters that can be monitored.

Attaining Close Temperature Control of Flowing Process Liquids

Selection and placement of temperature sensors is a
critical element of achieving close temperature control.

Temperature control is a common operation in the industrial arena. Its application can range across solids, liquids, and gases. The dynamics of a particular operation will influence the selection of instruments and equipment to meet the project requirements. In addition to general performance requirements, safety should always be a consideration in the design of a temperature control system involving enough energy to damage the system or create a hazardous condition.

Let's narrow the application range to non-flammable flowing fluids that require elevated temperatures. In the interest of clarity, this illustration is presented without any complicating factors that may be encountered in actual practice. Much of what is presented here, however, will apply universally to other scenarios.

What are the considerations for specifying the right equipment?

KNOW YOUR FLOW

First and foremost, you must have complete understanding of certain characteristics of the fluid.

• Specific Heat - The amount of heat input required to increase the temperature of a mass unit of the media by one degree.
• Minimum Inlet Temperature - The lowest media temperature entering the process and requiring heating to a setpoint. Use the worst (coldest) case anticipated.
• Mass Flow Rate - An element in the calculation for total heat requirement. If the flow rate will vary, use the maximum anticipated flow.Maximum Required Outlet Temperature - Used with minimum inlet temperature in the calculation of the maximum heat input required.

MATCH SYSTEM COMPONENT PERFORMANCE WITH APPLICATION

Heat Source - If temperature control with little deviation from a setpoint is your goal, electric heat will likely be your heating source of choice. It responds quickly to changes in a control signal and the output can be adjusted in very small increments to achieve a close balance between process heat requirement and actual heat input.

Sensor - Sensor selection is critical to attaining close temperature control. There are many factors to consider, well beyond the scope of this article, but the ability of the sensor to rapidly detect small changes in media temperature is a key element of a successful project. Attention should be given to the sensor containment, or sheath, the mass of the materials surrounding the sensor that are part of the assembly, along with the accuracy of the sensor.

Sensor Location - The location of the temperature sensor will be a key factor in control system performance. The sensing element should be placed where it will be exposed to the genuine process condition, avoiding effects of recently heated fluid that may have not completely mixed with the balance of the media. Locate too close to the heater and there may be anomalies caused by the heater. A sensor installed too distant from the heater may respond too slowly. Remember that the heating assembly, in whatever form it may take, is a source of disturbance to the process. It is important to detect the impact of the disturbance as early and accurately as possible.

Controller - The controller should provide an output that is compatible with the heater power controller and have the capability to provide a continuously varying signal or one that can be very rapidly cycled. There are many other features that can be incorporated into the controller for alarms, display, and other useful functions. These have little bearing on the actual control of the process, but can provide useful information to the operator.

Power Controller - A great advantage of electric heaters is their compatibility with very rapid cycling or other adjustments to their input power. A power controller that varies the total power to the heater in very small increments will allow for fine tuning the heat input to the process.

Performance Monitoring - Depending upon the critical nature of the heating activity to overall process performance, it may be useful to monitor not only the media temperature, but aspects of heater or controller performance that indicate the devices are working. Knowing something is not working sooner, rather than later, is generally beneficial. Controllers usually have some sort of sensor failure notification built in. Heater operation can be monitored my measurement of the circuit current.

SAFETY CONSIDERATIONS

Any industrial heater assembly is capable of producing surface temperatures hot enough to cause trouble. Monitoring process and heater performance and operation, providing backup safety controls, is necessary to reduce the probability of damage or catastrophe.

High Fluid Temperature - An independent sensor can monitor process fluid temperature, with instrumentation providing an alert and limit controllers taking action if unexpected limits are reached.

Heater Temperature - Monitoring the heater sheath temperature can provide warning of a number of failure conditions, such as low fluid flow, no fluid present, or power controller failure. A proper response activity should be automatically executed when unsafe or unanticipated conditions occur.

Media Present - There are a number of ways to directly or indirectly determine whether media is present. The media, whether gaseous or liquid, is necessary to maintain an operational connection between the heater assembly and the sensor.

Flow Present - Whether gaseous or liquid media, flow is necessary to keep most industrial heaters from burning out. Understand the limitations and operating requirements of the heating assembly employed and make sure those conditions are maintained.

Heater Immersion - Heaters intended for immersion in liquid may have watt density ratings that will produce excessive or damaging element temperatures if operated in air. Strategic location of a temperature sensor may be sufficient to detect whether a portion of the heater assembly is operating in air. An automatic protective response should be provided in the control scheme for this condition.

Each of the items mentioned above is due careful consideration for an industrial fluid heating application. Your particular process will present its own set of specific temperature sensing challenges with respect to performance and safety. Share your requirements with temperature measurement and control experts, combining your process knowledge with their expertise to develop safe and effective solutions.

Product Options Round Out Fulfillment of Application Requirements

Analynk Wireless, in addition to their standard products, can provide an extensive range of value added services to help customers quickly and effectively fulfill project requirements involving wireless communications and process control. Share your challenges with the wireless and process control experts at Analynk, combining your process knowledge with their wireless and control expertise to develop effective solutions.

Refractometry Applications in Industry

In-line refractometer for industrial processing
Courtesy Electron Machine

Refractometry, a combination of physics, materials, and chemistry, is the process which measures the composition of known substances by means of calculating their respective refractive indexes (RI). RIs are evaluated via a refractometer, a device which measures the curve, or refraction, resulting when the wavelength of light moves from the air into and through a tested substance. The unitless number given by the refractometer, usually between 1.3000 and 1.7000, is the RI. The composition of substances is then determined when the RI is compared to a standard curve specific to the material of the substance. There are also four separate types of refractometers: digital, analog, lab, and inline process. Although refractometry can measure a variety of substances, including gases and solids, the most common category of known substances to calculate are liquids; the inline process refractometer is used to quantify the makeup of liquids.

The ultimate focus of industrial refractometry is to describe what is in a final product or output of a process step. A field which relies directly on the results of refractometry is gemology. Gemological refractometry is crucial for accurately identifying the gemstones being classified, whether the gemstones are opaque, transparent, or translucent.

Other common examples of industrial refractometry uses are measuring the salinity of water to determine drinkability; figuring beverages’ ratios of sugar content versus other sweeteners or water; setting eye-glass prescriptions; understanding the hydrocarbon content of motor fuels; totaling plasma protein in blood samples; and quantifying the concentration of maple syrup. Regarding fuels, refractometry scrutinizes the possible output of energy and conductivity, and for drug-testing purposes, refractometry measures the specific gravity, or the density, of human urine. Regarding food, refractometry has the ability to measure the glucose in fruit during the fermentation process. Because of this, those in food services know when fruit is at peak ripeness and, in turn, also understand the most advantageous point in the fruit’s “lifetime” to put it on the market.

The determination of the substance composition of the product examples listed above all speak to the purpose of quality control and the upholding of standardized guidelines; consumers rely on manufacturers not only to produce these products but also to produce these products consistently and identically every single time. Therefore, the success of commercialism, etc. is dependent on maintaining the standards for the composition of substances, i.e. industrial refractometry.

Equipment manufacturers have developed numerous refractometer configurations tailored to specific use and application. Each has a set of features making it the advantageous choice for its intended application. Product specialists can be invaluable sources of information and assistance to potential refractometer users seeking to match the best equipment to their application or process.

Analynk manufactures wireless communications equipment to connect process measurement instruments with remotely located process monitors and controllers. Their products enable customers to make connections across the room, across the plant, across the highway, and around the globe.

Defending Industrial Control Systems From Cyber Threats

Industrial control system data cannot be protected by
a fence around the plant site.

Industrial control system owners, operators, and other stakeholders should be aware of their exposure to malicious intrusion and attack by individuals or organizations intent on inflicting physical damage, stealing information, or generally wreaking havoc throughout an industrial operation. The risk of intrusion, regardless of the size or type of facility, is real and deserves the focused attention everyone involved in the design and operation of industrial control systems.

The National Cybersecurity and Communications Integration Center, part of the US Department of Homeland Security, ...

serves as a central location where a diverse set of partners involved in cybersecurity and communications protection coordinate and synchronize their efforts. NCCIC's partners include other government agencies, the private sector, and international entities. Working closely with its partners, NCCIC analyzes cybersecurity and communications information, shares timely and actionable information, and coordinates response, mitigation and recovery efforts. (from www.us-cert.gov/nccic)

The Industrial Control Systems Cyber Emergency Response Team (ICS-CERT) is a division under NCCIC. It has published a set of seven basic steps toward establishing a more secure industrial control system. I have included the publication below, and it is interesting and useful reading for all involved in industrial process control.

Having a fence around an industrial site, with a guarded entry gate, no longer provides the level of security needed for any industrial operation. Read the seven steps. Take other actions to build your knowledge and understanding of the risks and vulnerabilities. Cybersecurity is now another layer of design tenets and procedures that must be added to every control system. It will be a part of your company's best practices and success, now and in the future.

There are uncountable legacy controllers and communications devices throughout industrial America. All need to be reassessed for their vulnerability in the current and upcoming security environment. When reviewing your processes and equipment, do not hesitate to contact Analynk Wireless for assistance in your evaluation of our products.

Defending industrial control systems from cyber attack from Analynk Wireless, LLC

Solar Powered Wireless Communications for Industrial Process Measurement and Control

Analynk Model A650 Solar Power Supply

Wireless connections of process measurement and control equipment sometimes are accomplished in remote locations without readily available electric power. Analynk, as part of its full line of industrial wireless connectivity products, provides their model A650 Solar Power Supply for locations that require a small amount of DC power to operate instrumentation and an Analynk transmitter.

The power supply unit comes complete with solar panel, battery, charge controller, and NEMA 4 enclosure. Options are available to accommodate specific installation requirements. Custom units can be designed for larger power requirements and other special applications.

The data sheet below provides more detail. Share your wireless process measurement and control connectivity challenges with Analynk for effective solutions.

Solar power supply for industrial wireless transmitters from Analynk Wireless, LLC

Process Connections - Wireless is Simple Solution to Many Challenges

Wireless connections for industrial process signals

The operating personnel at almost every facility have something to which they would like to connect. Remotely located equipment, activities that require a human to be present to monitor operation, and other scenarios are all candidates for a wireless connection. Have you ever thought that it would be helpful to know more about the current status of a remotely located piece of gear, for example, the back-up generator located across the parking lot? Budgets, time constraints, cabling difficulties, and other factors seem to continually outweigh the benefits of making the connection and gathering the data. Those days are gone. In fact, they have been gone for some time.

Industrial wireless transmitters, receivers, and repeaters can be applied in place of wires, cables, conduit, trenches, overhead supports, and all the other hardware associated with a wired installation. Data is gathered using whatever process measurement hardware you prefer, just specify commonly used output signals like 4-20 mA, or a host of others. Connect the measuring device output to the transmitter input. Locate a receiver where you want the sensor information delivered. The transmitter converts the sensor analog signal to digital and the receiver converts back to analog. The connection can be accomplished in a very short amount of time without disturbance to the real estate between the two points.

How can I tell if the wireless connection can be accomplished without interference?

The transmission is accomplished in either the 900 MHz or 2.4 GHz band, delivering adequate range and power for most facility-wide applications. Obstructions can be overcome with the use of a strategically located repeater.

What about power needed to operate the sensors and wireless equipment?

Most process sensors have very small power requirements, as do the Analynk transmission units. Power, if line voltage is not available at the location, can be provided by batteries, or combination of battery and photovoltaic. Little power needs to be provided for operation.

There may be simple and effective wireless solutions to many of your remote monitoring challenges. Don't assume it is difficult, it is not. Don't assume it is expensive, it is not. Share your ideas and challenges with the experts at Analynk. Combining your facility and process knowledge with their technology and product expertise will lead to effective solutions.