Classification
-evaporative
-surface (radiator)
EVAPORATORY TYPE OF RECYCLING WATER SUPPLY COOLERS
Evaporative coolers
According to the method of supplying air to them, they are divided into:
- open(cooling reservoirs, spray pools, curtains) - air movement occurs by wind and natural convection.
-tower(tower cooling towers) - air movement due to natural draft created by a high tension tower.
-fan(fan cooling towers) – forced air supply using injection or suction fans.
Reservoirs - coolers
Based on purpose, location and nutritional conditions, the following groups are distinguished:
A) regulating reservoirs on watercourses. Used for cooling circulating water and for long-term flow regulation.
B) Reservoirs on watercourses without flow regulation
C) Reservoirs on natural lakes and ponds
D) Filling reservoirs outside the watercourse with recharge from nearby rivers
Design of the main structures of the cooling reservoir
The design of dams, spillways and canals is carried out according to the standards for the design of hydraulic structures.
The location of the spillway, water intake, jet distribution and jet directing structures is selected based on the conditions for obtaining the required area of the core ( w act), based on technical and economic calculations.
Jet guiding and jet distribution structures performed in the form of spillways, bridges, pipes, cantilever spillways, filter dams made of rock fill.
The most rational water intake structure from a reservoir more than 4-5m deep - called deep water intake, ensuring the intake of water from the bottom layers. Its advantages:
The lowest water intake temperature is achieved.
The uptake of biological contaminants is prevented or significantly reduced
The capture of fish and moths is sharply reduced
The most efficient purging of the reservoir is achieved
Ensures uninterrupted water supply to the consumer during sludge conditions (crushed ice) phenomena without taking measures to heat water intakes.
Splash Pools
The main element of the splash pool is spray device- This is a system of nozzles that spray water supplied to them under pressure. In this case, the total surface of the droplets must be sufficient to cool the water during its evaporation. The ongoing process is quite complex, which makes it difficult to develop theoretical methods for their thermal calculation. To determine the temperature of chilled water, empirical dependencies are used.
Spray devices are located above an artificial pool or above a natural spillway. Sometimes for additional cooling above the cooling reservoir due to its limited size. There are two main types of nozzles used:
-centrifugal- water passes in a spiral, spraying under the influence of centrifugal force. Made from malleable cast iron or plastic.
-slotted- from segments gas pipes at the end of which slots are divided in the form of a slit, the resulting teeth are bent towards the axis to form a cone with a small hole at the top.
The design of the nozzle and the amount of water pressure in front of them determine the cooling surface of the water torch. As the pressure increases, it increases due to the elongation of the flight path of the droplets, reducing their diameter. However, increasing the pressure increases energy costs and increases the wind drift of droplets outside the pool.
The nozzles are located at a height of 1.2-1.5 m above the water level, one at a time or in groups of 3-5 pieces at a certain distance.
Distribution pipelines connected to the manifold.
Pipelines are made of steel and laid above or below the water level. When laid under water, the design of the supports is simplified and the danger of icing in winter is eliminated, but repair and monitoring of them becomes more complicated.
The size and location of the spray devices is determined by the flow of cooled water and the irrigation density, that is, the water flow per 1 m2 of the area of the spray device. Irrigation density is 0.8-1.3 m/h.
For effective wind blowing, the distribution lines of the spray devices are placed parallel to the direction of the prevailing winds. The distance between the outermost nozzles on the same line is less than 45m.
The pool consists of at least two sections, the water depth is about 1.5 m, the excess of the edge is at least 0.3 m. Clothing on the slopes and bottom of the pool should prevent water from filtering through them. For weakly permeable soils, use reinforced concrete slabs or a layer of asphalt concrete. For highly permeable soils, a layer of waterproofing is laid after preparation from concrete, with concrete or reinforced concrete slabs on top. Around the pool there is an asphalt area 3-5m wide, with a slope away from the pool.
Cooling towers
The contact area necessary for cooling water is created using sprinklers. Sprinklers there are:
-drip Such a sprinkler consists of a large number of wooden slats of triangular or rectangular cross-section arranged in tiers. When drops fall from the upper slats to the lower ones, a torch of small splashes is formed, creating a large surface of water with air.
-film consists of panels installed vertically or at a slight angle. Water flows down the surface of the boards, forming a film of 0.3-0.5 mm. The boards are made either from separate boards at some distance from each other or solid from well-wetted materials. To create a continuous film, triangular cutouts (festoons) are made at the lower edge of the shield, which concentrate the flowing water into streams and stretch the film over the surface of the shield. Drip is preferable, but more materials are used to make it.
-combined (or drop-film) When designing a sprinkler, they strive to improve air resistance, since this increases the air flow through the cooling tower and speeds up the water cooling process.
Sometimes high-pressure spray nozzles are used instead of sprinklers, but they are less effective due to the smaller area of contact between water and air.
In a cross-flow sprinkler, air passes horizontally across the downward films or falling drops of water.
In counterflow, the air moves upward towards the flowing water.
Sprinklers made of flat or corrugated asbestos-cement sheets with a frame made of prefabricated reinforced concrete and plastic sprinklers are common.
To avoid icing of the sprinklers in winter, reduce the air flow into the cooling tower or douse warm water sprinkler areas near air inlet windows.
Types of cooling towers
Open cooling towers
There are two types:
Splatter. A small splash pool is fenced on all sides with reinforced concrete gratings, which prevent large splashes of water from being carried outside the cooling tower. Sprinkling nozzles of small capacity are at a height of 4-5 m above the water level in the pool and are directed downwards. Irrigation density: 1.5 – 3m/(h*m2).
Drip sprinklers have sprinklers made of wooden blocks between the louvered walls. The water distribution device consists of a system of pipes with nozzles. Irrigation density is 2-4m/(h*m2).
Cooling towers
They are made in the form of exhaust towers to create natural draft due to the difference in the specific gravity of the outside air entering the cooling tower and the heated humidified air leaving the cooling tower. With counterflow sprinklers, exhaust towers are built above them. Cross-flow sprinklers are located in a ring around the tower.
The cross-sectional area should be at least 30-40% of the sprinkler area. Towers of small and medium-sized cooling towers can be: cylindrical, truncated cone-shaped or truncated polyhedral pyramid-shaped. Towers of large cooling towers in the form of shells of hyperbolic shape, which are the most rational in terms of stability and internal aerodynamics. Frame-sheathing and monolithic towers are used.
In frame-sheathing, the frame is made of steel elements and welding, and the cladding is made of wooden panels, asbestos-cement corrugated sheets or sheet aluminum.
Typically, towers rest on a frame structure called a colonnade, with air passing between the posts. A drainage tank made of monolithic reinforced concrete with waterproofing of the inner surface is installed under the cooling tower sprinklers. Chilled water is supplied through risers to a water distribution device located in the center of the cooling tower.
Fan cooling towers
Two main types:
Tower - equipped with high-performance fans using natural air draft. In tower cooling towers, fans are installed in the neck of the tower.
Sectional – from standard sections served by fans.
To reduce the entrainment of droplets outside the cooling tower, water-collecting louvered grilles are used. Air comes out from one or both sides. Each section is equipped with a suction or injection fan. Suction fans installed above the sprinkler ensure a more uniform distribution of air and do not freeze in the winter since it is located in a zone of warm air. Pressure units are installed at the inlet of the cooling tower at its base.
Fan cooling towers are convenient, but expensive.
Water losses in coolers
When cooling water in evaporative coolers, part of it is lost to evaporation; the amount of loss is determined by the formula as a percentage of the circulation flow:
k – coefficient taking into account the share of heat transfer to evaporation in the overall process of heat transfer in the cooler (see table)
Dt - temperature difference, degrees
In addition to losses due to evaporation, part of the water is carried away with air in the form of drops outside the cooling tower, a process called droplet entrainment.
Entrainment losses as a percentage of circulation flow are:
Splash pools with throughput up to 500m/h: 2-3%,
More than 500m/h: 1.5-2%;
Open and spray cooling towers: 0.5-1.5%,
Cooling towers: 0.5 – 1%,
Fan cooling towers with water traps 0.3-5%.
Cooler type selection
It is made on the basis of technical and economic equations of various types, they take into account:
Performance indicators of water supplied equipment
Technology requirements industrial enterprises to cooling water temperature
Hydrological conditions
Weather conditions
Geological conditions
Topographic conditions
Quality and cost of make-up water
Open cooling towers
Small dimensions, especially at low water flow rates
Used when a constant chilled water temperature is not required
Low cooling effect
Cooling towers
Provides more consistent cooling and lower water temperatures
Compactly placed on the site of an industrial enterprise
Can be used at different water flow rates
High construction cost and complexity of construction
(usually used for large industrial enterprises)
Fan cooling towers
Provide the deepest and most stable water cooling
In summer, cools to lower temperatures than other coolers
It is possible to regulate the water temperature by changing the rotation speed or turning off individual fans
They usually have a lower construction cost and are compactly located on the site of an industrial enterprise
High power consumption
The complexity of operating mechanical and electrical equipment
Humidified air from cooling towers spreads low to the ground, forming fog and causing icing of surrounding buildings
It is advisable to use when the technological processes of the enterprise do not require a low and stable temperature of the cooled water, as well as in areas with a hot and humid climate
The role of water in an enterprise
At the enterprise, water is spent on:
-technological needs. It is usually used for auxiliary purposes and is included in products only in some industries in small quantities. In accordance with the role played by water in industrial water supply systems, they are divided into 4 categories:
1. water for cooling equipment and product in heat exchangers without contact with the product. The water only heats up and is practically not polluted.
2. As a medium that absorbs and transports impurities (without heating): mineral processing, hydrotransportation. Contaminated with mechanical and dissolved impurities.
3. As a transport media cooler and impurity absorber: gas capture and purification, coke slaking, etc. The water heats up and becomes polluted.
4.To dissolve reagents and produce steam. It is mainly included in the technological product and only a part is contaminated.
-household and drinking needs;
-watering the territory and green spaces;
-firefighting.
Water quality requirements
Household drinking water complies with SanPiN. The quality of water for fire fighting is not regulated.
The quality of water for production needs is established in a specific case, depending on the purpose of the water, the requirements of the technological process of raw materials, and the equipment used for finished product production. The main thing in technological standardization of water quality is the conditions for using water in industrial water supply systems, so that the water does not disturb the technological process and the sanitary condition of workplaces. In accordance with this, the following requirements are put forward:
Must be harmless to personnel
Must have good organoleptic properties
Should not degrade product quality
Should not cause corrosion of equipment, pipelines and structures
Should not produce carbonate and other salt deposits
Should not contribute to biological and other types of fouling
Should not reduce the technical and economic indicators of the production process
Should not create emergency situations
Requirements may vary depending on the type of production!
Deferrization of water
Iron occurs in nature in the form of 2+ and 3+ ions in the form of components and suspensions of inorganic and organic origin.
IN groundwater in the absence of dissolved oxygen, it is found in the form of the 2+ ion, in the surface form in the form of colloids and highly dispersed and humate organic components. At a pH of up to 4.5, iron is most often found in the form of ions, at a pH of more than 4.5: Fe 2+ -> Fe 3+ -> Fe(OH) 3 ¯.
The rate of oxidation increases in the presence of catalysts in water. Catalysts can be:
Ions Cu 2+ Mg 2+ PO4 3- ,
When water comes into contact with manganese oxides or already formed Fe(OH)3
With increasing pH.
Methods of iron removal: reagent and non-reagent. (Reagent-free - without the participation of atmospheric oxygen).
The deferrization method is selected by process analysis, trial deferrization, and trial installation directly at the source.
Based on the results of experimental deferrization, taking into account the experience of existing ones, a method is selected that gives the best effect at the lowest cost.
Reagent-free:
1. Simplified aeration - spraying treated water from a certain height above a conventional rapid filter or intermediate tank. Fe 2+ is oxidized to form Fe(OH)3. Using non-pressure and pressure filters.
2. Intensive aeration method - used if the first method does not give the desired effect. Promotes intensive removal carbonic acid. They are used: installations with air bubbling, spray installations, vacuum ejection apparatus.
3. Iron removal in the formation – Viredox. (see lectures) Depending on the rocks, calvation (clogging of rock pores) of the aquitard surface is possible and does not provide the required flow.
Reagent:
1. Treatment with strong oxidizing agents. Used to destroy complex iron compounds. It is necessary to ensure a certain time of contact of water with the oxidizing agent. Use contact cameras
2. Alkalinization (usually using lime - liming) When alkali is introduced, the pH increases (more than 7) and iron is removed faster. Oxidation is carried out by oxygen! It is used to remove highly concentrated stable forms of iron from water, which is achieved after the destruction of iron-organic complexes.
3.Filtering method through modified loading. It is based on the fact that the process of iron oxidation is significantly accelerated in the presence of manganese oxides. A modified load is obtained from conventional (for example, quartz sand) treatment with potassium permanganate. The resulting film acts as a catalyst for iron oxidation.
4.Ion exchange method. The difference from the previous ones is that it is based not on oxidation, but on the replacement of ions. Used for deferrization and water softening - calcium cation exchanger Ca[cat] 2.
COOLING DEVICES. RECYCLING WATER SUPPLY SYSTEM.
Classification
The use of water in cooling for industrial purposes exceeds all other types of consumption. IN circulating system In the water supply of industrial enterprises, more than 80% of all circulating water is heated and must be subsequently cooled to the original temperature before subsequent use. For this purpose, cooling devices are used, which cool to temperatures that meet the optimal technical and economic performance indicators.
The temperature decrease in the cooler occurs due to heat transfer to the air. According to the method of heat transfer, coolers are divided into
-evaporative– cool water by evaporation in direct contact with air, while the evaporation of 1% of water reduces the temperature by 6 degrees.
-surface (radiator)– cooling occurs due to the transfer of heat from the air through the wall of tubes – radiators, inside which it passes without contact with air.
Evaporative ones cool and humidify, radiator ones only cool!
Since the heat and moisture capacity of air is not large, intense air exchange is required for cooling. To reduce 40 degrees to 30 at an air temperature of 25 degrees per 1 m3 of cooled water, 1000 m3 of air must be supplied to the evaporative cooler and 5000 m3 to the radiator cooler.
When circulating water supply to an industrial facility, the cooling device (cooler) must ensure cooling of the circulating water to temperatures that meet the optimal technical and economic performance indicators of the facility.
The temperature of the water in the coolers decreases due to the transfer of its heat to the air. Based on the method of heat transfer, coolers used in circulating water supply systems are divided into evaporative and surface (radiator) coolers.
In evaporative coolers, water is cooled as a result of its evaporation in direct contact with air (evaporation of 1% of water reduces its temperature by 6°). In radiator coolers, the cooled water does not have direct contact with the air. Water passes inside the radiator tubes, through the walls of which its heat is transferred to the air.
Since the heat capacity and moisture capacity of air are relatively small, intense air exchange is required to cool water. For example, to lower the water temperature from 40 to 30 ° C at an air temperature of 25 ° C, about 1000 m3 of air should be supplied to the evaporative cooler per 1 m3 of cooled water, and to the radiator cooler, in which the air is only heated, but not humidified, - about 5000 m3 of air.
Based on the method of supplying air to them, evaporative coolers are divided into open, tower and fan. Open coolers include cooling reservoirs (or cooling ponds), spray ponds, and open cooling towers.
In them, the movement of air relative to the surface of the cooled water is determined by wind and natural convection. In tower coolers - tower coolers - air movement is caused by natural draft created by a high exhaust tower.
In fan coolers - fan cooling towers - a forced air supply is carried out using injection or suction fans.
Radiator coolers, which are also called “dry cooling towers,” can be tower or fan based on the method of supplying air to them.
To cool circulating water to sufficiently low temperatures, a large area of contact with air is required - about 30 m2 per 1 m3/h of cooled water. According to this recommendation, the water surface area of cooling reservoirs should be taken.
In cooling towers, the required contact area is created by distributing water over irrigation devices, through which it flows under the influence of gravity in the form of thin films or drops, breaking up into tiny splashes when hitting the slats.
In spray pools, to create the required area of contact with air, water is sprayed with special nozzles into tiny droplets, the total surface of which must be sufficient for evaporative cooling.
TECHNICAL DESCRIPTION
Recirculated water cooling units (WCOU)
PURPOSE
The circulating water cooling unit (hereinafter referred to as “UOOV”) is intended for cooling process water in circulating water supply systems of energy-consuming equipment (heat exchangers of compressor units, condensers of refrigeration machines, air conditioners, injection molding machines, machine tools, production lines, technological equipment in industry, electronic equipment, etc.).
N and Q – flow of energy and heat from external sources;
Q1 – heat flow transferred to water during the work process;
Q2 is the heat flux dissipated in the atmosphere during cooling of water in the UOOV cooling tower.
Working processes in energy-consuming equipment, as a rule, require the removal and dissipation of heat flows in the environment (Fig. 1). First, the most efficient intermediate coolant, water, is passed through heat exchangers and cooled equipment components. The water in them heats up. In order to reuse the same water repeatedly in a closed water supply loop, it must be cooled. There is only one way to do this - to dissipate the heat flow in the atmospheric air. The use of UOOV allows not only to solve this problem, but also to significantly reduce energy costs and consumption of network water.
2. OPERATING CONDITIONS
2.1 Climatic modification U1 according to GOST 15150-69:
- maximum operating air temperatures from +45 to -50°C; relative air humidity in the warmest and most humid period is 80% at 20°C for six months; dust content in the air is not more than 0.01 g/m3; the presence of sticky and fibrous substances in the air is not allowed; atmosphere type II - industrial (sulfur dioxide content from 20 to 250 mg/m2 day, or 0.025 to 0.31 mg/m3; chlorides less than 0.3 mg/m2 day).
2.2 Contamination of the cooled water must be within the normal values typical for process water in recycling cycles, pH = 6…8.
2.3 Maximum temperature of water supplied for cooling directly to the unit: + 500C. To cool water with a temperature above 500C, agreement with the manufacturer is required. Maximum minimum water temperature at the outlet of the UUOV: + 210C.
Note: The use of UOOV for cooling heavily contaminated (including oils), acidified and alkaline waters must be agreed with the manufacturer.
3. TECHNICAL CHARACTERISTICS
3.1 The main parameters are given in Table 1.
3.2 Power supply for fan motors - from three-phase network voltage 380 V, frequency 50 Hz. Electric motors have climatic modification U2 and degree of protection IP54 according to GOST 14254-96. UUOV are equipped with single-speed and multi-speed electric fan motors. The list of standard electric motors is given in table. 2.
3.3 Type of fans - axial series VO 06-300.
3.4 The installation can have a monoblock or separate assembly.
3.5 The unit’s cooling unit can be made of stainless steel.
Table 1
Basic indicators | Model of circulating water cooling plant |
|||||||||
Cooled water consumption, m3/hour | ||||||||||
Heat flow,* kW | ||||||||||
Nominal water cooling, 0С Single/double circuit | ||||||||||
Number of nozzles, pcs. | ||||||||||
Number of fans, pcs. | ||||||||||
Impeller diameter, mm | ||||||||||
Rotation speed, rpm | ||||||||||
Installed electric motor power, kW |
|
|
|
|
|
|||||
Air consumption, thousand m3/hour | ||||||||||
Weight, kg | ||||||||||
Overall dimensions of the cooling tower body, mm | 2130x 2018x 3370 | 2227x 2938x 3367 | ||||||||
Sound pressure level at a distance of 10m, dB(A) |
* at a wet bulb temperature of 190C, relative humidity of 60% and water cooling by 100C; conversion to other conditions is available upon request.
The choice of CUOV and other system elements must be linked in the design to the cooling object. The project should also include measures to transfer the system to winter operating conditions. If the cooling object belongs to the objects high degree liability or special operating conditions, then the design must provide for backup UOOV and develop special measures to maintain the operability of the system during the winter period.
Responsibility for ensuring the operability of the UUOV in winter conditions lies with the customer.
table 2
Installation model | Electric motor brands, power, kW/rotation speed, rpm |
|
Single speed electric motor | Multi-speed electric motor |
|
AIR63A4 0.25/1500 | ||
AIR80V6 1.1/1000 |
1,25/970 1,0/710 |
|
AIR80V4 1.5/1000 |
1,7/1420 1,0/710 |
|
AIR100L6 2.2/1000 |
1,8/960 1,32/710 |
|
|
3,0/1430 1,2/940 0,71/700 |
||
- Along with the indicated electric motors, electric motors of other models with corresponding values of power and rotation speed, as well as electric motors with frequency control of the rotation speed, can be used.
4. DEVICE AND PRINCIPLE OF OPERATION
The circulating water supply cooling unit (WCS) is a system consisting of the following main blocks:
- block cooler (cooling tower), pump group, control cabinet UOOV, tank for circulating water, water filter with the ability to wash filter elements ( additional option), non-chemical water treatment devices (additional option).
Cooling towers have a rectangular shape with lower side fans.
Cooling towers of models UOOV-4 ... UOOV-16 consist of a one-piece housing, an electric fan, a tank for draining cooled water located in the lower part of the body, a sprinkler, a drop eliminator, a water distribution manifold with nozzles, inlet and outlet (drain) water pipes.
Cooling towers of the UOOV-24 ... UOOV-350 models are composite and consist of a block and a tank, and otherwise are equipped in the same way as the cooling towers of the UOOV-4 ... UOOV-16 models.
In the cooling tower model UOOV-350, the fans are mounted on their own frame and connected to the diffusers via a flexible insert.
On all models, an inclined visor with an upward bend and hydraulic slopes from the middle to the side walls is installed in the tank above the diffuser windows. The canopy serves to protect window openings from splashes and freezing of moisture on the walls of the openings in winter. In the standard version, the cooling tower body is made of stainless steel grade 12Х18Н10Т. The tubular collector, supporting frame, fans with diffusers can be manufactured in two versions: both from stainless steel and from carbon steel with painting.
The sprinkler and drop separator are packages of corrugated PVC sheets with a thickness of 0.3 - 0.4 mm. The sheets have an oblique corrugation. Adjacent sheets are laid with the corrugation in the opposite direction. In cooling towers of models UOOV-4 ... UOOV-16, a sprinkler block with a height of 400 mm is assembled from packages with a height of 200 mm. In cooling towers of the UOOV-24 and UOOV-32 models, a sprinkler with a height of 540 mm is assembled from packages of the same height. In cooling towers of models UOOV-50...UOOOV-350, a sprinkler with a height of 940 mm is assembled from packages with a height of 400 and 540 mm.
The droplet eliminator package has a thickness (in the direction of air flow) of at least 75 mm, the width of the package is 140 mm.
Sprinkler packages are placed on a grid inside the cooling tower above the tank in one or two layers. The droplet eliminator packages are placed on a grid welded to the water distribution manifold between the manifold pipes and the walls of the housing. In models UOOV-50 ... UOOV-350, two layers of droplet eliminator are laid in mutually perpendicular directions.
Cooled water is supplied under pressure through the inlet pipe into the water distribution manifold and sprayed by solid-flare nozzles with a spray angle of 120° onto the upper end of the sprinkler package. Having passed through the sprinkler channels in the form of a film, the water flows into the tank in streams. Air from environment is supplied by a fan directly into the space under the sprinkler, passes through the sprinkler channels towards the water film and leaves the cooling tower through a drop catcher.
Evaporative cooling of water occurs mainly in the sprinkler channels with counterflow of air and water film. Additional cooling takes place in the tank and in the space between the upper section of the sprinkler and the nozzles. In the hot season, with a relative humidity of 50-60%, the minimum temperature of the chilled water after the cooling tower is 4-5°C higher than the “wet” thermometer temperature. To prevent significant droplet entrainment of water, an effective drip eliminator is used. Water consumption for evaporation together with losses through the droplet eliminator (the smallest drops) is about 1% of water consumption. An increase in relative air humidity compared to the usually normalized 50-60% brings the dry-bulb and wet-bulb air temperatures closer together. At a fixed air flow rate per 1 m3 of water, this reduces the share of evaporative cooling and increases the temperature level of the process in the cooling system relative to the ambient temperature.
The water pressure in front of the nozzles must be provided for in the design of the water supply system. The number of nozzles in each model is shown in Table 1.
Cooling tower fans can be equipped with two- and three-speed electric motors (optional). Table 2 shows the brands of one-, two- and three-speed electric motors for all models of cooling towers.
5. SAFETY PRECAUTIONS
5.1. When operating the UUOV, you must follow the rules technical operation consumer electrical installations (PTEEP) and inter-industry rules on labor protection (safety rules) during the operation of electrical installations (POT RM-016-2001).
5.3. Maintenance work on the UUOV must be carried out by specially trained personnel.
5.4. It is prohibited to carry out maintenance work on the UUOV without removing the voltage from the electric motors.
6. INSTRUCTIONS FOR OPERATION, INSTALLATION AND REPAIR
6.1 To ensure normal operation of cooling units, the enterprise must develop appropriate instructions for operating personnel. It is recommended to carry out periodic inspections of installations at least once a month.
6.2 To accommodate the installation in case of separate installation, a metal frame is provided under the cooler block, based on the dimensions of the cooler block.
6.3 When placing installations on the site, take into account the nature of the development of the surrounding area, as well as the direction of the prevailing winds in winter and summer.
6.4 In order to reduce the diameters and length of pipelines, installations are located as close as possible to water consumers.
6.5 Routine repairs of installations must be carried out as necessary, but at least once a year, if possible, in summer period. The scope of current repairs includes work that does not require shutting down the water treatment plant for a long period of time, namely cleaning and repairing the water distribution device, pipeline, sewerage, nozzles, drip eliminator and sprinkler. During a major overhaul, all types of work are performed that require a long shutdown of the installation: eliminating damage to the sprinkler, repairing or replacing a fan or pump group, etc.
6.6 If the installation is inoperative for a long time, it is necessary to check the insulation resistance before starting up. If its value is less than 0.5 MOhm, the electric motors should be dried with current. short circuit at undervoltage or external heating. The drying temperature should not exceed 1000C.
6.7 It is not recommended to regulate the operation of the unit at positive air temperatures by periodically turning off the blower fans. The water supplied by the nozzles ejects air and pushes it out through the fan windows. With a high hydraulic load, typical for UOOV cooling towers (20-30 m3/h/m2), the fan electric motors can be exposed to water jets, while their IP54 protection is protection against water splashes from all sides. Penetration of dripping moisture into the housing or terminal box will lead to motor failure. In addition, a long stay of an idle engine in a stream of saturated humid air creates the effect of “suction” of moisture, i.e. diffusion of water vapor into the housing through the gaps around the shaft. When a certain “critical” mass of moisture accumulates inside, an insulation breakdown may occur.
6.8 When installing UOVV indoors, the following requirements must be observed. Taking air from the room and simultaneously releasing it into the room is unacceptable, since at the outlet of the cooling tower the air humidity is close to 100%. Through a short time the cooling tower will stop cooling water and the room enclosures will become damp. You cannot take air from the room and throw it outside the room, since air will flow in the same amount through gates, windows, and from other rooms. In winter, this will be cold air, which will require energy to heat up. When installing a cooling tower indoors, you will need a thermally insulated duct to supply air from the street and the same duct to take it outside. An additional fan may be required to compensate for the associated pressure loss.
7. OPERATION OF UUOV IN WINTER TIME
In winter, freezing of the sprinkler is extremely dangerous, as this can lead to its deformation and collapse. Freezing usually begins at outside air temperatures below –10°C and occurs in places where the cold air supplied to the installation comes into contact with a relatively small amount of warm water(in places with low irrigation density).
Therefore, in winter, fluctuations in thermal and hydraulic loads should not be allowed, it is necessary to ensure uniform distribution of cooled water over the sprinkler area, and a decrease in irrigation density in individual areas should not be allowed. Due to the relatively high velocities of incoming air, the irrigation density in UOOV fan cooling towers in winter is advisable to maintain at least 10 m3/m2h.
To prevent major freezing of cooling towers, it is necessary to reduce the flow of cold air into the cooling tower. The lower the incoming air temperature or less thermal load to the cooling tower, the lower the air flow should be. The temperature of the chilled water can be used as a criterion for determining the required air flow. If the flow of incoming air is regulated so that the temperature of the cooled water in the cooling tower is not lower than 12°C ... 15°C, then icing of UOOV cooling towers is usually small and does not exceed acceptable limits.
To reduce the supply of cold air to the cooling tower, throttling devices (diaphragms, disk shields, etc.) can be installed on the fan inlets. If there are multiple fans on the same tower, the throttling devices must be the same on all fans. The same effect can be achieved by evenly covering the cross section of the upper cut of the cooling tower. The closure of fan windows or the top of the cooling tower can be made dependent on the temperature of the water leaving the cooling tower.
For water circulation systems that use several cooling towers, in winter it is possible to turn off some of them, transferring water to those left in operation. This helps reduce icing on cooling towers. The cooling tower shutdown must be complete and proceed in the following sequence: the water is turned off, after which the fans are turned off. The manifold with nozzles must be purged with compressed air, fans with electric motors must be dismantled, and the upper section of the cooling tower must be covered with shields.
Blower fans are susceptible to freezing. This may be caused by recirculation of tower exhaust air containing small droplets of water (entrainment) and steam that condenses when mixed with cold outside air. Uneven ice formation on the blades can cause the fan to become unbalanced and vibrate.
It is impossible to regulate operation in winter mode by periodically turning off the supply fans, because in the absence of excess pressure in the cooling tower, the supplied water ejects air and pushes it out through the fan windows. At the same time, the air carries out small drops of water, which freeze on the blades and shells of the fans. In addition, turning off the fans helps draw moisture into the motor.
The installation of a heating pipeline (hose) along the perimeter of the fan shell with the supply of part of the heated water into it helps to prevent freezing of the shell of a working fan during air recirculation and, in some cases, freezing of fans when they are turned off. It is also possible to heat the shell using a flexible electric heater with a power of no more than 1 kW.
8. WARRANTY
7.1 The manufacturer guarantees reliable and uninterrupted operation of the UUOV, subject to compliance with the rules of transportation, installation and operation.
7.2 The warranty period is 24 months from the date of commissioning of the UUOV.
7.3 In the event of failure of the device during the warranty period, the manufacturer accepts claims only upon receipt from the customer of a report with technically justified indications of the nature of the faults. The act requires information on the dates of delivery, installation, commissioning, storage conditions of the water treatment plant before installation (outdoors, under a canopy, in a warehouse), on the temperature and quality of water supplied for cooling, a link to the design of the recycling water supply system indicating the design organizations.
In case of failure of the cooling tower during the winter period, it is necessary to list the measures that were taken to prevent icing of the cooling tower of the cooling tower, the flow rate and temperature of the water at the inlet and outlet.
In recycling water supply systems, part of the water is reused (multiple times). At the same time, the process water heats up. Before reuse, the water temperature must be reduced in accordance with technology requirements. Reducing the temperature of process water is achieved in special cooling devices (coolers).
Based on the method of heat removal, coolers are divided into evaporative and surface (radiator) coolers. In an evaporative cooler, heat removal is achieved as a result of evaporation in direct contact with air; in a surface cooler, water moves in tubes washed with outside air.
The choice of cooler type is made on the basis of a technical and economic comparison based on the minimum costs given, taking into account the performance indicators of the entire plant technical water supply system. When comparing options, hydrological and meteorological conditions are taken into account in relation to the area where the water supply system is being constructed.
Evaporative coolers can be represented by: cooling ponds (cooling reservoirs), spray pools and tower or fan-type cooling towers.
Ponds and cooling reservoirs have a number of undoubted advantages. They provide lower cooling water temperatures throughout the year; are regulators of surface runoff; are easy to operate and can provide water for the circulating water supply of any large plant. However, the creation of cooling reservoirs is associated with significant capital costs for both the main structure and the construction of treatment facilities.
Spray pools require relatively small capital investments and are used with low flow rates of process water (up to 300m 3 /h). They have poor cooling ability and allow big losses water.
Tower cooling towers are used in circulating water supply systems with water flow rates up to 100-10 3 m 3 /h. Thanks to the organized air movement, stable cooling is ensured and the water temperature is lower than in a splash pool. The disadvantages include high capital costs.
Fan cooling towers provide the deepest and most stable cooling of process water. Construction costs are lower than those of towers. High energy consumption and the possibility of fog and icing formation significantly influence the choice of water supply option with fan cooling towers. Their use turns out to be economically justified when a low and stable temperature of cooled water is required (refrigeration and compressor stations, production technologies in areas with hot climates).
Some characteristics of evaporative coolers are given in table. 2.7.
Table 2.7. Characteristics of evaporative coolers
The use of radiator coolers makes it possible to minimize water losses in the circulating water supply system. The water in “dry” cooling towers is not clogged with dust from the surrounding air and salts (water mineralization), as is the case in “wet” type cooling towers. “Dry” cooling towers have a larger volume compared to “wet” ones, since the heat exchange rate in them is lower. Their use can be justified by the impossibility of replenishing water losses in cooling systems.
Cooling water in evaporative coolers is always accompanied by its losses due to evaporation (a decrease in water temperature by 6 °C in evaporative cooling systems is associated with water losses of up to 1%). Water losses are calculated using the formula
DV = DV isp + DV un
where DV isp is the share of evaporated water, DV un is the share of entrainment with air outside the cooler from the circulation flow (Table 2.8).
Table The amount of water entrainment DV un
The DV value is determined by the formula
DV isp = kDT,
where k is a coefficient that takes into account the share of heat transfer by evaporation from the total heat transfer coefficient (evaporation and convection), % (Table 2.9); DT - absolute value of temperature difference, °C.
Table 2.9. k coefficient value
As a result of the evaporation of part of the water in the cooler, the concentration of mineral salts dissolved in the circulating water increases. In this case, temporary hardness salts MgCO 3 and CaCO 3 (mainly CaCO 3) precipitate on the surface of the device, which worsens its performance and sharply reduces the heat transfer coefficient. To prevent this phenomenon, the circulating water supply system is continuously purged, i.e., part of the circulating water is removed from it and replenished with fresh water from a natural water supply source. Blowing is carried out with water from the deep layers of the cooler. Then the salt balance equation has the form
C d (DV use + DV un + DV prod) = C c (DV un + DV prod), (2.3)
where C d, C c - the concentration of hardness salts in the additional and circulating water, respectively, mEq/l; DV isp, DV un - water loss through evaporation and entrainment, %; DV prod - volume fraction of removed water relative to circulating water, %.
If taken for circulation system With c at the maximum permissible level (SNiP II - 31-74), then expression (2.3) can be rewritten as
C d (DV use + DV un + DV prod) = C y max (DV un + DV prod),---------
From equality (2.4) find the value of DV prod, expressed as a percentage. However, it must be remembered that regulation of the salt balance of the circulating water supply system by continuous blowing is effective only in the case when C d<<С ц ma х. Во всех остальных ситуациях применяют способы снижения жесткости воды путем реагентной обработки, табл.2.10.
Table Methods for reagent softening of industrial water
Along with the precipitation of hardness salts, oxygen corrosion products, mechanical suspensions, and biological organisms contained in natural water can be deposited in circulating water supply systems. To combat biological fouling, circulating water is treated with chlorine. Chlorination is carried out periodically for 30 minutes at intervals of 3...12 hours in doses of 1.5...7.5 mg/l (depending on water quality). When the system is overgrown with algae, the water is treated with copper sulfate 2...3 times a month for 1...2 hours in doses of 4...6 mg/l. In case of bacterial fouling, along with treatment with copper sulfate, water is chlorinated in doses of 2 mg/l with a chlorination duration of 30...40 minutes.
COOLING DEVICES FOR RECYCLING WATER SUPPLY SYSTEMS
When circulating water supply to an industrial facility, the cooling device (cooler) must ensure cooling of the circulating water to temperatures that meet the optimal technical and economic performance indicators of the facility.
The temperature of the water in the coolers decreases due to the transfer of its heat to the air. Based on the method of heat transfer, coolers used in circulating water supply systems are divided into evaporative and surface (radiator) coolers. In evaporative coolers, water is cooled as a result of its evaporation in direct contact with air (evaporation of 1% of water reduces its temperature by 6°). In radiator coolers, the cooled water does not have direct contact with the air. Water passes inside the radiator tubes, through the walls of which its heat is transferred to the air.
Since the heat capacity and moisture capacity of air are relatively small, intensive air exchange is required to cool water. For example, to lower the water temperature from 40 to 30 ° C at an air temperature of 25 ° C, about 1000 m3 of air should be supplied to the evaporative cooler per 1 m3 of cooled water, and to the radiator cooler, in which the air is only heated, but not humidified, - about 5000 m3 of air.
Based on the method of supplying air to them, evaporative coolers are divided into open, tower and fan. Open coolers include cooling reservoirs (or cooling ponds), spray ponds, and open cooling towers. In them, the movement of air relative to the surface of the cooled water is determined by wind and natural convection. In tower coolers - tower coolers - air movement is caused by natural draft created by a high exhaust tower. In fan coolers - fan cooling towers - a forced air supply is carried out using injection or suction fans.
Radiator coolers, which are also called “dry cooling towers”, can be tower or fan based on the method of supplying air to them.
To cool circulating water to sufficiently low temperatures, a large area of contact with air is required - about 30 m2 per 1 m3/h of cooled water. According to this recommendation, the water surface area of cooling reservoirs should be taken. In cooling towers, the required contact area is created by distributing water over irrigation devices, through which it flows under the influence of gravity in the form of thin films or drops, breaking up into tiny splashes when hitting the slats. In spray pools, to create the required area of contact with air, water is sprayed with special nozzles into tiny droplets, the total surface of which must be sufficient for evaporative cooling.
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It is believed that heat transfer from the surface of whirlpools occurs with less intensity than from the surface of a transit flow. The area of the actual surface of the reservoir is replaced, according to the proposal of N. M. Vernadsky, by the “area of the active zone,” which takes into account the heat transfer of the transit flow and adjacent eddies. The ratio of the area of the active zone to the area of the actual surface of the reservoir is called the coefficient of utilization of the reservoir area: /C=o)act/o)v. This coefficient, depending on the shape of the reservoir, the layout of the spillway and water intake structures and the spreading conditions of the circulation flow, can have values from 0.5 to 0.95.
More reliable data for design, in particular the coefficient of utilization of the area of the cooling reservoir, can be obtained from the results of hydrothermal modeling on a large-scale model of the reservoir, which is carried out according to the methodology developed by VNIIG. B. E. Vedeneeva in 1971
In order to distribute the transit flow of circulating water over the largest possible part of the surface of the reservoir and create an area of the active zone sufficient to cool the design flow, water heated at an industrial enterprise is discharged at a considerable distance from the water intake structures, and also stream directing and stream distribution structures are used.
Research in recent years has established that in large and deep cooling reservoirs, which are built, for example, for modern powerful thermal power plants, it is possible to create a volumetric circulation of water. To do this, it is necessary to organize the intake of water only from the deep layers of the reservoir, and the heated water is discharged to the surface of the reservoir at low speeds. Then it is possible to locate discharge structures near water intakes and even combine them in one structure. In this case, heated water, which has a lower density than cold water, spreads over the surface of the reservoir and, cooling, passes into the deeper layers, which move to water intake structures. This circulation pattern
makes it possible to eliminate the need for long outlet channels and stream-directing structures with a high utilization rate of the reservoir area.
Some examples of the organization of cooling reservoirs and the layout of structures designed to ensure the fullest use of their surface for cooling water are given in VI 1.5. Presented here:
an elongated reservoir on a watercourse (VII.5, a); circulation is ensured by an outlet channel and a flow-directing dam in front of the water intake structures;
a reservoir of complex shape on a watercourse (VII.5, b); circulation is ensured by a dividing dam and an artificial slot;
wide reservoir on the watercourse (VII.5, b); circulation is ensured by a jet guide dam;
use of a system of natural lakes for cooling water (VII.5, d);
a bulk reservoir, for the construction of which the terrain was successfully used (VII.5, e);
a bulk reservoir with circular water circulation and a water intake structure in the center (VII.5, f);
a deep reservoir on a small watercourse with the release of heated water to the surface and a deep water intake structure located near the outlet (VI 1.5,g); water circulation is volumetric with multidirectional surface and deep flows.
Thermal calculation of the cooling reservoir. Thermal calculation of a cooling reservoir is carried out to determine the temperature of cooled water at the point of its receipt for a given area of the active zone or to determine the required area of the active zone of the reservoir for given thermal and hydraulic loads.
To facilitate practical calculations, you can use the nomogram on VII.6, for which you should calculate the specific area of the active zone yuud per unit flow rate of cooled water, in m2/m3 per day. The nomogram determines the overheating of the circulating water cooled in the reservoir and supplied to the place of its reception, in comparison with the natural water temperature (U-te), depending on the amount of water heating at the power plant (temperature difference D^=^1-^g) -
For approximate calculations, you can take the required area of the cooling reservoir from 30 to 50 m2 to cool 1 m3/h of water by 8-10°.
Main structures of cooling reservoirs. The design of dams, dikes, spillways and canals for cooling reservoirs is carried out in accordance with the relevant standards for the design of hydraulic structures.
The location of spillway and water intake structures, as well as structures that increase the active zone of the reservoir (stream distribution and stream directing structures), is selected based on the conditions for obtaining the required area of the active zone based on technical and economic calculations.
Jet directing and jet distribution structures are made in the form of spillways, trays, pipes, cantilever spillways. It is most advisable to construct jet distribution structures in the form of flooded spillways with a flat profile or in the form of filter dams made of rock fill. Such structures ensure the release of warm water to the surface of the reservoir at low speeds, which prevents the occurrence of deep flow to the spillway.
The most rational type of structure for collecting water from a cooling reservoir with a depth of at least 4-5 m is a deep water intake, which ensures the receipt of water from the bottom layers. This achieves the lowest temperature of the cooling water, prevention or sharp reduction of the capture of biological contaminants (microorganisms, lower aquatic vegetation, mollusk larvae) and the most rational purging of the reservoir. With deep water intake, the capture of fish and, most importantly, fry, which usually live at shallow depths, sharply decreases. Deep water intake also ensures uninterrupted water supply to consumers during sludge conditions without taking measures to heat the water intake.
To avoid suction of water from the upper layers, the inlet windows of the deep water intake must be located at a sufficient depth, and the inlet water velocities must be minimal. Depending on the depth of the upper edge of the water intake window, input velocities are taken from 0.1 to 0.3 m/s.
Deep water intakes were previously carried out in the form of intake walls, submerged to a certain depth and forming inlet openings between the bottom of the reservoir and the lower edge of the wall. In recent years, water intake structures made in the form of an underwater gallery with a slot of variable cross-section in the front wall and a canopy above the slot, the design of which was developed at the Teploelektroproekt Institute (VII.7), have become widely used. Such a water intake structure is not exposed to wave and ice loads and ensures a uniform flow of water along the entire water intake front.