What is a cooling tower or cooling tower?
In a short sentence, the cooling tower should be considered as the source of producing cool water needed in every industry. The cold water produced by this refrigeration source again absorbs the excess energy of the equipment and transfers it to the air. This exchange process is a repetitive cycle that keeps the working temperature of industrial machinery constantly constant. This cooling and refrigeration device can take the heat of chillers, boilers or induction furnaces by constantly providing cold water. Constantly reducing the temperature of machines and absorbing their heat is a big concern in ensuring the stability of the system.
The lack of frequent circulation of cool water causes the temperature of industrial machines to increase and will cause them to not work properly. Therefore, using a cooling tower will fix the efficiency of a cycle. These systems may sometimes be a residential, office and commercial building air conditioning cycle. Or these important equipments may be responsible for the production process of one or more products.
Why do we use a cooling tower??
Maybe the question arises why we use cooling towers. As we know, most industrial and non-industrial equipment heat up after a while in their work cycle. A small percentage of these machines or equipment dissipates the heat generated by the ambient air. Most of these equipments also use circulating water to dispose of their excess heat. The water that has absorbed the heat of these machines will increase in temperature and will be directed to the heat exchangers. On the other hand, the cold water produced from the cooling tower in the converter completely removes this heat energy.
What is a cooling tower or cooling tower?
In a short sentence, the cooling tower should be considered as the source of producing cool water needed in every industry. The cold water produced by this refrigeration source again absorbs the excess energy of the equipment and transfers it to the air. This exchange process is a repetitive cycle that keeps the working temperature of industrial machinery constantly constant. This cooling and refrigeration device can take the heat of chillers, boilers or induction furnaces by constantly providing cold water. Constantly reducing the temperature of machines and absorbing their heat is a big concern in ensuring the stability of the system.
The lack of frequent circulation of cool water causes the temperature of industrial machines to increase and will cause them to not work properly. Therefore, using a cooling tower will fix the efficiency of a cycle. These systems may sometimes be a residential, office and commercial building air conditioning cycle. Or these important equipments may be responsible for the production process of one or more products.
Types of use of cooling towers in industry and air conditioning
First use: to remove heat from various industrial devices in all seasons
Most industrial machines such as induction and arc furnaces, boilers and turbines, etc., generate a large amount of heat in their working cycle. By completing this industrial cycle, the cooling tower performs the process of absorbing this thermal energy and disposing it to the desired environment. Gas turbines in refineries, air compressors in power plants and steam boilers in various industries are among the most important applied industries of this product.
In this user model, the task of extracting heating energy is the responsibility of air without ambient humidity. The air coming out of the throat part causes the air coming out of the tower to become saturated by increasing the humidity ratio. It is interesting to know that these vapors in the air will mainly cause the formation of clouds and fog in the upper part of the cooling tower.
Second use: to cool the air conditioning
The majority of residential buildings and large and small apartments, offices, banks and shopping centers have a central ventilation system. In central cooling systems, compression or absorption chillers are usually used to cool the indoor air. The heat absorbed from a building area by the chiller will increase the temperature of the refrigerant (compressor gas).
The cold water produced from the tower in the condenser part of the chiller compensates for the increase in the temperature of the refrigerant. It should be noted that only chillers with water condensers use a cooling tower in their condenser circuit. It is better to note that most compression and absorption chillers have a water condenser.
chillers of the buildings in the summer
Classification of cooling towers based on the type of incoming air flow
A) Counterflow cooling tower: Counterflow cooling tower has air intake from all sides of the device in the upper part of the pan and the lower part of the packings. The direction of the incoming air flow to the cooling tower is opposite to the flow of water spraying from the nozzle. In this model, the air enters from the lower louvers and exits from the upper part of the fan oven. The efficiency of this cooling tower model is very suitable for hot and dry environments. They are widely used in cities such as Yazd, Shiraz, Mashhad, Tehran, Arak and Isfahan where the relative humidity is low. Counterflow systems are more efficient than cross systems. Of course, the use of these systems in wet and humid areas has little efficiency.
b) Cross-flow cooling tower: Cross-flow cooling tower has two main air inlets on both sides. When the air enters this part perpendicularly to the falling water flow, it cools this fluid. The cross-flow cooling tower has good performance in hot areas due to the contact of fresh air throughout the packing area. In the northern and southern regions of our beloved country, due to the proximity to the sea, the humidity of the environment where the cooling tower is installed is high.In such climatic regions, cross flow cooling towers or EBARA are used. Cities like Ahvaz, Mahshahr, Bushehr, Rasht, Gorgan, etc. are very suitable for using this device. This model was first conceptualized by the Japanese Ibara company. For this reason, such refrigeration systems are also called Abara cooling towers.
Classification of cooling towers with different body materials
1- Fiberglass cooling tower: Nowadays, most of the industrial products are focused on fiberglass. The use of composite industry in the production of fiberglass parts is FRP (fiber reinforce polymer). Fiberglass means glass fibers reinforced with plastic, which consists of two elements, fibers and resin. In simpler terms, the composite structure of the body consists of fibers reinforced with polyester resins. The fiberglass parts of the body are first covered with fiber, resin, erosil and titanium in the desired mold. After gel time and baking, they are separated from the original mold. In order to cook and final processing, the parts of the body are placed in contact with direct sunlight.
Cooling tower with circular or cylindrical structure: The circular or round cooling tower is one of the oldest production designs of many manufacturing companies. One of its main characteristics is the rotating water sprinkler system with a sprinkler. The large cylindrical dimensions and low height compared to the cubic model are among their other prominent features. The most common use of this type is in high-rise buildings for heat balance in the chiller condenser.
Advantages of cylindrical or circular cooling tower
Easy installation at the project site
Less fan or propeller noise and easier and optimal air circulation
The price is lower and more economical than the cubic type
Air suction due to larger louvres
Classification of cooling towers with different body materials
1- Fiberglass cooling tower: Nowadays, most of the industrial products are focused on fiberglass. The use of composite industry in the production of fiberglass parts is FRP (fiber reinforce polymer). Fiberglass means glass fibers reinforced with plastic, which consists of two elements, fibers and resin. In simpler terms, the composite structure of the body consists of fibers reinforced with polyester resins. The fiberglass parts of the body are first covered with fiber, resin, erosil and titanium in the desired mold. After gel time and baking, they are separated from the original mold. In order to cook and final processing, the parts of the body are placed in contact with direct sunlight.
pay attention !! The type of fibers and resin used in the manufacture of fiberglass parts has the greatest impact on the final quality of the body.
Compressed fiberglass fibers are used in the cooling tower in two general types: wicker and needle in the body parts. The combination of these two fibers in the production of body parts increases the final strength of the composite structure. Of course, the powder fibers as fillers in the last layers make the body waterproof. The production of fiberglass body parts must be done according to the required standards in order to have the expected quality. Nowadays, fiberglass cooling tower is mainly produced and supplied in two types, cubic and circular. This device is an excellent alternative to all types of concrete and metal cooling towers in the industry. Different parts of the fiberglass body of this type include fan stack, panel, louvre, column and pan.
Classification of cooling towers based on the type of incoming air flow
A) Counterflow cooling tower: Counterflow cooling tower has air intake from all sides of the device in the upper part of the pan and the lower part of the packings. The direction of the incoming air flow to the cooling tower is opposite to the flow of water spraying from the nozzle. In this model, the air enters from the lower louvers and exits from the upper part of the fan oven. The efficiency of this cooling tower model is very suitable for hot and dry environments. They are widely used in cities such as Yazd, Shiraz, Mashhad, Tehran, Arak and Isfahan where the relative humidity is low. Counterflow systems are more efficient than cross systems. Of course, the use of these systems in wet and humid areas has little efficiency.
b) Cross-flow cooling tower: Cross-flow cooling tower has two main air inlets on both sides. When the air enters this part perpendicularly to the falling water flow, it cools this fluid. The cross-flow cooling tower has good performance in hot areas due to the contact of fresh air throughout the packing area. In the northern and southern regions of our beloved country, due to the proximity to the sea, the humidity of the environment where the cooling tower is installed is high.
In such climatic regions, cross flow cooling towers or EBARA are used. Cities like Ahvaz, Mahshahr, Bushehr, Rasht, Gorgan, etc. are very suitable for using this device. This model was first conceptualized by the Japanese Ibara company. For this reason, such refrigeration systems are also called Abara cooling towers.
Low vibration and low vibration frequency due to excellent damping of vibrations by glass fibers
Easy access to internal parts such as packing, dripper, nozzle and water dispenser
No decay against water flow inside and dust outside
Lack of thermal permeability and heat absorption by the solar radiation
Lack of sedimentation against water evaporation and increase of soluble substances
Ability to acid wash body and descale internal equipment
Lightweight and easy to carry and moveAdvantages of fiberglass cooling tower
Concrete or cement cooling tower: concrete cooling tower (concert cooling tower) has an all-cement structure in a cubic or hyperbolic shape. The aeration system in this equipment is generally an axial blowing or induction suction system. The aeration system of these refrigeration systems includes a large blower axial fan or several small suction axial fans. This type is mostly seen in large power plants and refineries, and for this reason, it is also called a power plant cooling tower. Today, concrete type, mainly towers, are widely used for industries that have high water flow.
Reasons for rejecting the concrete cooling tower system
Very high weight and excessive weight of the main body and structure
Inability to transport and move and change the place of installation
Very high cost of concrete civil structure
Low construction speed of cement structure
Excessive water consumption due to poor heat exchange performance
The growth of algae and micro-organisms and bacteria inside the concrete pan
– Galvanized or steel metal cooling tower: using a metal body seems to be a smart option to avoid wasting time in the production of the device. The used metal body can have sufficient resistance against sedimentation and corrosion by creating appropriate coatings. The cooling tower with a metal body is produced and supplied in the form of galvanized steel or stainless steel material. The metal cooling tower generally has a metal frame and skeleton in the form of several fabrics. The main structure and frame of the device is assembled by screws. Metal cooling towers were mostly produced and supplied by Baltimore and Sarafrin companies in the past. Today, due to many design disadvantages, this model of refrigeration systems is not used much.
Reasons for rejecting the metal or galvanized cooling tower system in the industry
Deposition and corrosion of metal body against water flow
Very high weight and being too heavy
Not easy to carry and move due to excessive weight of metal parts
Lack of easy access to internal components due to corroded fittings
The growth of algae, sludge and microorganisms and the reduction of the quality of outgoing cold water
Easy absorption and penetration of radiant heat energy from sunlight
Creating a lot of noise due to the vibration of the body and the type of poor ventilation systems
How to calculate the power or capacity of the cooling tower
The cooling tower’s ability to remove heat energy from the water fluid and transfer it to the air is called cooling power or cooling capacity. The higher the cooling power, the better the potential of the device in reducing the water temperature. The cooling fluid, the amount of liquid in circulation and the temperature difference between inlet and outlet are considered as the primary factors for determining the refrigeration capacity. The volume rate of circulating water is called water flow rate. Of course, the humid temperature of the environment, the relative humidity and the height above the sea level are also secondary factors in the working conditions. The difference in fluid inlet and outlet temperature is called delta or range
Characteristics determining the capacity of the cooling tower
Mass flow rate of circulating fluid (nominal fluid flow)
Type of cooling fluid and determination of specific heating capacity at constant pressure
Fluid inlet and outlet temperature (outlet temperature limited to bubble temperature)
Design effect factor in calculating nominal capacity and separating it from real power
Common and conventional methods for calculating cooling tower capacity
Thermodynamic equations governing design conditions (q=m*c*delta T)
Using online and offline software such as Demagaster computing software
Calculation based on the capacity and nature of the chiller
What is meant by tons of cooling in the cooling tower?
You must have heard many times that the chiller capacity is equal to 100 tons or 200 tons. In most cooling systems, the word “refrigerating ton” is defined as equivalent to cooling power in water cooling. In this engineering term, the word ton is shortened to the word cooling ton or cold ton, which is considered one of the units of heat transfer. In the principles of thermodynamics, the cold ton is considered as a measure of the power of refrigeration devices. The unit of energy transfer in time, i.e. ton of refrigeration (RT), is equivalent to units such as KW and BTU/H. Each ton of refrigeration is equal to 3.51 kilowatts and equal to 12 thousand pounds of energy per hour.
Law of conservation of energy and mass in cooling tower system
energy balance
The cooling tower is a device for transferring QC heat (condenser heat of an industrial machine) to the surrounding environment. In the cycle of every thermodynamic process, the law of conservation of energy is established. The operation of energy transfer in the cooling tower is also considered a thermodynamic process. The energy consumption of the cooling device represents the power consumption (in the form of electric energy) in the consuming parts of the tower. The main consumers of electrical energy are the electric motor of the aeration section and the water circulator pump. The produced heat is also a sign of the amount of energy that is transferred to the water in the condenser section. Finally, the complement of these two items is the removal of the heat absorbed from the water in this device. The rewriting of the energy conservation law in the working cycle of the cooling tower is done as follows.
mass balance
The process of energy exchange in the form of cooling towers is a combined process of mass and heat transfer simultaneously. The cooling tower causes a percentage of water to evaporate by creating a very large heat exchange surface. The evaporation done in the introduction itself absorbs the heat in the main stream of water. The heat required to vaporize water and break the molecular bonds of water is absorbed from the rest of the water flow. The main stream of water fluid will lose its temperature and become cold.
In addition to evaporation, two other factors cause water wastage in the cooling tower. Bloudan, or the discharge and throwing of water drops from the axial fan, is another factor of water consumption. In order to establish the law of constancy of mass, we must permanently enter a certain amount of water into the device. This flow of water that enters the cooling tower permanently is also called make-up flow. The following formula is established in order to maintain the fluid flow in the above system.
Compensatory flow = evaporated water + discharge of thick material flow (blow down) + ejection of drops from the fan part
How to exchange heating energy in a cooling tower
In heat transfer science, evaporative heat exchangers are a type of heat energy transmitters. This cooling equipment performs the action of transferring the excess heat of a thermodynamic cycle to the surrounding environment. Energy transferred from water to air can sometimes take place in an open system. In this case, the water at the outlet of the nozzles sprays on the packing media and comes in contact with the induced air of the fan.
In this contact flow, the heat of the water is transferred to the air in two ways. In the first case, the heat is transferred from water to air due to the temperature difference between the two fluids in the packings or cellulose pads. In the second case, energy in the form of sensible heat causes the evaporation of a small percentage of water and cooling of this fluid. The use of two energy exchange methods has caused this system to have the highest cooling efficiency in all types of cooling towers.
In some types of cooling towers, the heat exchange surfaces are in the form of coils or a network of narrow pipes. The fluid flow is cooled by passing through the network of narrow pipes in contact with the dry air of the open environment. Sensible heat in this process is zero and evaporation does not take place in the main flow of the fluid. The temperature drop in this method will be less, but the great advantage of this method is the non-evaporation of the water flow. The lack of evaporation in the closed cycle in the cooling towers causes the reduction of deposits and corrosion in the converter and other equipment. The use of closed cycle in the cooling flow of other fluids is also used. In addition to the above two advantages, the lack of evaporation in the closed cycle causes the water consumption of this equipment to be very low. The water consumption of combined cooling towers is even 25% of water consumption in open systems.
Cooling tower technical specifications catalog
The cooling tower of Demagostar company with fiberglass body can be supplied and produced in various types of open circuit and closed circuit. The cooling tower catalog has been collected in three different categories by the technical experts of Demagaster company. The catalog or brochure contains useful information about the dimensions and other technical specifications of the types. The catalog of this product actually contains all kinds of information and technical specifications of the materials and equipment used
These specifications can be changed according to the type and model of the device, the material of the side parts. For example, the thickness of the fiberglass body varies according to the weight of water and the capacity of the device. Also, the ventilation system parameter in each model has a fan or propeller with a specific diameter. The power of the electric motor is specified in the catalog according to the torque required to rotate the propeller and only for a certain ventilation direction.
The main and basic information available in the technical specifications catalog
Cooling power in reducing water temperature
The maximum inlet temperature to the cooling tower and the minimum outlet temperature
The allowable flow volume of circulating water fluid at the entrance to the device
Water consumption in hot and cold seasons according to standard working conditions
Dimensions and final dimensions of each of the different production capacities
Working weight and dry weight of the main structure
Input and output connections and side connections
Electric motor power consumption and amperage consumption or type of electricity consumption (three-phase or single-phase)
The diameter of the propeller or fan as the air suction center
The volume of produced air based on the CFM unit
The number of fan or propeller blades according to the amount of ventilation required
How to choose the right cooling tower
The design and selection of refrigeration systems should not be done by ordinary people, but this matter should be done by the relevant expert. The technical consultant of the project with engineering knowledge makes the correct and principled selection of this equipment. The expert should suggest the desired cooling tower considering the design principles. At the stage of choosing a cooling tower, different quantitative and qualitative aspects should be considered. The main principles in the process of choosing and designing a cooling tower are to calculate the capacity and determine the amount of water consumed. Calculation of design parameters such as efficiency, cooling capacity and estimation of providing water consumption is one of the most important parts of selection.
At the stage of buying any product, it is not recommended to use only the technical specifications catalog.The choice of any industrial machine from the catalog should not be made only according to its capacity. In addition to the cooling capacity of the cooling tower, other factors also affect the selection and design parameters of this equipment. Side factors such as the climate of the place of installation and quality conditions of the water standard will have a significant impact on the purchase and correct choice. Therefore, it is better to avoid choosing unprofessionally from the catalog of technical specifications. The best option in choosing an industrial facility is to simultaneously use all available design parameters. The most important design tool is the use of online software in engineering calculations and the use of the catalog of manufacturers of refrigeration systems.
Clogging in the cooling tower
Sedimentation and clogging of equipment and internal parts is one of the major unavoidable issues in equipment in contact with water. This issue may cause continuous problems during the working life of this device. In most types of cooling towers, whether open circuit, counter flow or cross flow, most of the deposits are formed due to water evaporation. The main reason for this issue is the increase in the concentration of soluble substances in circulating water. The formed sediments are generally made of lime and are white and light brown in color between packing grooves and other side parts. Calcareous sediments formed in the inner parts are mostly formed due to heavy water solutes such as calcium, magnesium and metal and salt cations.
The main and basic solutions to reduce sedimentation
Use of media packing or antibacterial and anti-fouling cooling cloth like net splash packing
Application of cooling tower water spray nozzle with anti-clog property
The use of nano powder and nano fiber fibers in the main texture of the body parts
Make up water injection with high quality or hardened
Accurate adjustment of the flush or the draining of thick water from the pan or basin
Choosing a cooling tower with a hybrid cooling system and reducing the amount of water evaporation
Not using metal equipment and reducing the amount of rust and not integrating heavy sediments caused by pipes or metal connections
The use of metal or non-metal filters in the air intake section, which prevents the entry of dust in the air.
Maintenance and protection of the cooling tower
The maintenance phase of a refrigeration device such as a cooling tower is the most important step after installation and commissioning. If this operation is done correctly, it will have very beneficial effects on the system. Maintaining and protecting the tower increases the life of its internal and external parts. If the maintenance principles of this device are not followed properly, it will cause many problems.
Different and important parts in each turn of the cooling tower service
Washing with a jet or car wash in drip catchers, water dispensers and water distribution systems, louvres and other components in contact with polluted air
Washing with suitable acids in parts that are in constant contact with water, such as nozzles and packings
Adjusting the sprinkler outlet pipes and the correct rotation of the water spreader, and the descaling of the outlet holes from the side pipes
Adjusting the angle of the fan blades and its balance, which increases the lifespan of the bearings or gearbox, and also reduces the amperage consumed by the motor.
Overhaul or overhaul of the cooling tower
Repair or overhaul in the cooling tower is inevitable due to constant and frequent contact with water and exposure to the outside environment. Basic repair includes processes such as replacing packings or covers, replacing and repairing the fan or propeller in terms of reducing vibration and balancing the blades, replacing the internal drips or drippers, replacing nozzles or sprinkler heads. Depending on the quality of the material used inside the device, the repair period may be between 2 and 10 years. The higher the grade and quality of the secondary and main cooling tower equipment, the longer the life of the device and the longer the repair operation will be.
Basic solutions to extend the cooling tower repair period
Use of high-quality polymer material such as first-class PP or PVC (white color) in the production of internal packing
Choosing the right cooling tower and designing the water cooling system based on the best type of cooling tower
The combination of anti-UV materials in the body and parts that are in contact with the sun’s rays.
Using the new generation of propellers with super blades in the structure of the fan blades and reducing the amount of fan vibration
Using a fan or propeller with a suitable material for the design environment (for example: humid and acidic environments = fiberglass fan)
The use of protective equipment such as intelligent antifreeze heating system, compensatory water filtration system, air filters, etc.
Regular servicing and washing of internal parts in order to prevent future damage to other peripheral parts
The price and cost of the cooling tower
The price has the final say in any matter, and this is also true for the cooling tower. The price of each device that is produced can be influenced by various factors. The price of this equipment is constantly subject to many changes due to the comprehensiveness of the internal parts and dealing with different parts of raw material procurement. Due to the effort of cooling tower manufacturers and builders, all the manufacturing companies have tried to announce their prices with the lowest coefficient of variation.
The main factors affecting the price of the cooling tower
Device type (cubic or circular, open circuit or closed circuit)
Cooling capacity (from 10 tons of refrigeration to 4500 tons of refrigeration)
The price of fiberglass raw materials such as fiber and resin
The type of fiber and resin used in production and construction
The number of fiber and resin layers and the final thickness of the body
The type of packing media used and the grade of materials used in the packing
Thermal insulation grade and motor protection class and motor brand type
The type of propeller with a fan, the type of blades used and the number of suction fan blades
