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Selection, production method and principle of closed cooling tower 2019-07-30

Selection, production method and principle of closed cooling tower

Cooling tower selection instructions:

1. Please indicate the specific model selected for the cooling tower or the flow rate processed per hour.

2. The cooling tower into the tower temperature and the tower water temperature.

3. Please explain to what equipment to cool down, whether there is a circulating pool at the site, and how to install the site.

4. If you need spare parts and other accessories, please have any other requirements, please specify.

5.Very conditions of use, please specify the use of the environment and the specific circumstances, in order to choose the appropriate cooling tower model.

6. Please specify when ordering special cases and models, and design according to the contract and technical agreement of both parties.

 


Cooling tower detailed selection:

1. First, determine the inlet water temperature of the cooling tower to choose a standard cooling tower, a medium temperature cooling tower or a high temperature cooling tower.

2. Determine the use of equipment or the noise requirements of the site. You can choose a cross-flow cooling tower or a counter-flow cooling tower.

3. Select the cooling tower flow according to the cooling water volume of the chiller or the chiller. Generally speaking, the flow rate of the cooling tower is greater than the cooling water of the chiller. (Generally take 1.2-1.25 times).

4. When multiple units are connected in parallel, try to select the same type of cooling tower.

 


Secondly, pay attention to the selection of cooling towers:

1. The tower structure material of the cooling tower should be stable, durable, corrosion-resistant and accurate in assembly.

2. The water distribution is uniform, the wall flow is less, the splashing device is selected reasonably, and it is not easy to block.

3. The type of cooling tower water filling material meets the requirements of water quality and water temperature.

4. The fan is matched to ensure long-term normal operation, no vibration and abnormal noise, and the blade is resistant to water erosion and has sufficient strength. The installation angle of the fan blades is adjustable, but the angle is consistent and the current of the motor does not exceed the rated current of the motor.

5, low power consumption, low cost, small and medium-sized steel skeleton glass cooling tower also requires light weight.

6. The cooling tower should be avoided as far as possible in the heat source, exhaust gas and flue gas occurrence point, chemical stacking place and coal pile.

7. The distance between the cooling towers or between the tower and other buildings, in addition to considering the ventilation requirements of the tower, the tower and the building interact with each other, the safety distance of the building fire prevention and explosion protection and the construction and maintenance requirements of the cooling tower should also be considered.

8. The direction of the inlet pipe of the cooling tower can be rotated by 90°, 180° and 270°.

9, the material of the cooling tower can withstand low temperatures of -50 ° C, but for the coldest month, the average temperature is lower than -10 ° C

The area should be specified when ordering in order to take anti-icing measures. Cooling tower construction costs increased by about 3%. 10. The turbidity of circulating water is not more than 50mg/l, and the short-term is not more than 100mg/l. It should not contain oil and mechanical impurities. If necessary, measures to eliminate algae and water quality should be taken.

11. The water distribution system is designed according to the nominal water quantity. If the actual water quantity differs from the nominal water quantity by more than ±15%, it should be stated when ordering, in order to modify the design.

12. During the storage and transportation of the cooling tower components, no heavy objects should be pressed on them, and they should not be exposed to the sun, and attention should be paid to fire prevention. During the installation, transportation and maintenance of the cooling tower, no open flames such as electricity or gas welding shall be used, and fireworks shall be fired nearby.

13. Round tower multi-tower design, the net distance between the tower and the tower should be maintained at not less than 0.5 times the diameter of the tower body. The cross flow tower and the counter current square tower can be arranged side by side.

14. The pump should be matched with the cooling tower to ensure the flow, lift and other process requirements.

15. When selecting multiple cooling towers, use the same model as much as possible.

 


In addition, measuring the effectiveness of a cooling tower usually uses three indicators:

(1) The difference Δt between the inlet water temperature t1 of the cooling tower and the outlet water temperature t2. Δt is called the cooling water temperature difference. Generally speaking, the larger the temperature difference, the better the cooling effect. For production, the larger the Δt, the smaller the flow rate of cooling water required for the production equipment. However, if the inlet water temperature t1 is high, even if the temperature difference Δt is large, the temperature of the water after cooling does not necessarily fall to meet the requirements, so such an indicator is required, but the problem is not comprehensive enough.

(2) The closeness Δt' of the water temperature t2 after cooling and the air wet bulb temperature ξ. Δt' = t2 - ξ (°C) Δt' is called the cooling width. The smaller the value of Δt', the better the cooling effect. In fact Δt' cannot be equal to zero.

(3) Consider the watering density in the calculation of the cooling tower. The water spray density refers to the amount of water that can be cooled per hour on an effective area of 1 m2. It is represented by the symbol q. q=Q/Fm3/m2.h (Q-cooling tower flow, m3/h; F-cooling tower effective watering area, m2).

 

A common formula for determining the amount of circulating water in a cooling tower is known:

a. Cooling water volume = main engine cooling capacity (KW) × 1.2 × 1.25 × 861 / 5000 (m3 / h)

b. Cooling water = main condenser heat load (kcal / h) × 1.2 / 5000 (m3 / h)

c. Cooling water volume = main condenser heat load (m3/h) × 1.2 (m3 / h)

d. Cooling water volume = main engine cooling capacity (cold ton) × 0.8 (m3 / h)

e. Cooling water volume = main evaporator heat load (kcal / h) × 1.5 × 1.25 / 5000 (m3 / h)

f. Cooling water volume = main evaporator heat load (m3/h) × 1.2 × 1.25 (m3 / h)

g. Cooling water volume = main evaporator heat load (cold ton) × 1.2 × 1.25 × 3024 / 5000 (m3 / h) Note: Above: 1.2 is the selection margin 1.25 is the condenser load factor.

h. The cooling capacity of the vast lithium bromide host per 1 million kcal is:

Working condition 1: 37.5/32/28, (cooling water flow: 300~330m3/h) with 350-400 tower;

Working condition 2: 37/30/28, (cooling water flow: 248 m3/h) with 450 tower.

 


Closed cooling tower (also called evaporative air cooler or closed cooling tower)

The tubular heat exchanger is placed in the tower, and the cooling effect is ensured by the heat exchange between the circulating air, the spray water and the circulating water. Because it is a closed cycle, it can ensure the water quality is not polluted, which protects the efficient operation of the main equipment and improves the service life. When the outside temperature is low, the spray water system can be stopped to save water. With the implementation of national energy conservation and emission reduction policies and the increasing shortage of water resources, closed cooling towers have been widely used in steel metallurgy, power electronics, mechanical processing, air conditioning systems and other industries in recent years.

 


Method / step

The cooling capacity of the cooling tower should be cumbersome thermal calculation according to the parameters such as the wet bulb temperature, relative humidity, air flow speed, spray water volume, viscosity coefficient of the cooling medium, and heat resistance of the heat exchange tube. In general selection, the user can perform the following simple method, and select the corresponding cooling capacity cooling tower according to the calculated cooling capacity (Kcal/h).

 

☆According to the flow rate and temperature difference of the cooling medium Qs=cm△t

Qs-cooling medium heat dissipation, unit Kcal/h;

C-cooling medium specific heat capacity, unit Kcal (kg · ° C), water specific heat capacity is 1Kcal / kg · ° C; m - cooling medium quality, that is, flow, the unit is kg / h;

Δt-The temperature difference between the inlet and outlet of the cooling medium, the unit is k or °C.

☆According to equipment invalid power calculation Qs=Rated power (Kw)*Proportion*860 (Kcal/(h·kw))

☆According to the quenching part production Qs=Quenching part production (kg/h)* quenching part specific heat capacity* quenching part temperature difference.

 


The main components of the cooling tower:

1. Fan: Vertical axis fan, running in the suction system, through the air flow cooling tower. The efficiency of the fan can be adjusted by changing the angle of the blade.

2. Demisters: The water distribution system above the eliminator to greatly reduce the driving force outside the droplets of the cooling tower. The elimination should be characterized by high defogging efficiency and minimal air flow resistance.

3. Connecting pipe: The connecting pipe functions to connect the cooling tower and the cooling water channel that supply hot water.

4. Water distributor: The system it consists of includes a nozzle. The water distribution system is designed to be evenly distributed with water sprinkled on the surface of the packing.

5, the cooling tower shell of the support structure: is made of glass steel. It is made of glass polyester composite material. Use a corrosion-resistant material to keep the tower for a long time.

The purpose of the viewing window above the enclosure is to monitor the operation of the cooling tower.

6. Filler: It is placed on a stainless steel frame. The aim is to obtain as much as possible the contact surface of the cooling water with the air.

7. Blinds: Installed in the air inlet to facilitate the air intake cooling system fan and protect it from inhaling foreign objects.

8. Chassis: It is made of glass polyester composite material, which is designed to collect water flowing up from the packing to prevent unnecessary waste of water resources.

Principle

The generic term "cooling tower" is used to describe direct (open circuit) and indirect (closed circuit) heat sinks. While most have come up with a "cooling tower as an open direct contact heat sink", an indirect cooling tower, sometimes referred to as a "closed circuit cooling tower", is also a cooling tower.

A direct, or open-circuit cooling tower is a means of sealing the interior of the structure by spraying the circulating water onto the glass fiber packing by spraying. The packing provides a larger contact surface and achieves heat transfer through contact of water and air. Then, the fan drives the air circulation in the tower to bring out the hot air flow after the heat exchange with the water, thereby achieving cooling. Filling may include multiple, mainly vertical, wet-surfaced water (filled) or laterally splashing elements that create many layers of thin film (splash) with large surface area droplets cascaded.

Indirect or closed circuit cooling towers are not involved in direct contact with air and liquid, usually water or glycol mixtures. The difference is the open cooling tower, which indirectly has two separate fluid circuits. One is that the water in the external circuit is on the second track, which is the outer loop of the tube bundle (non-public coil) connected to the hot fluid process is cooled and returned in closed loop. The air is drawn through a loop of water circulated throughout the heat pipe, providing a similar evaporative cooling tower to open. The heat flow in operation from the internal fluid circuit, through the coil tube wall, to the external circuit, and then by some evaporation of air and water to the atmosphere. The action of the indirect cooling tower is therefore very similar, with one exception to the opening of the cooling tower. This process is carried out by a coolant in a "closed" circuit that is not directly exposed to circulating water in the atmosphere or outside.

When the air in the counterflow cooling tower passes upward through the fill or tube bundle, the opposite water moves downward. As the cross-flow cooling tower air moves horizontally through the fill, the water moves downward.

 


1. Heat exchanger - perfect performance.

The series of cooling towers all use improved high efficiency heat exchangers. The heat exchange coil is optimized on the traditional basis, and the elliptical section or stainless steel corrugated tube can effectively reduce the air side resistance and adapt to the larger spray water volume; The number of tubes increases the heat exchange area and the heat exchange efficiency is significantly improved. The downwardly flowing inner working fluid and the upward flowing outer air have the best heat transfer effect. The entire heat exchanger consists of one or more coiled tubing, surrounded by steel frame boxes, and is durable. The material of the coil group is excellent grade steel pipe. All the steel pipes are inclined properly in the flow direction of the working fluid in the pipe, which is convenient for the working fluid to flow out. It is made well and must pass the pressure test of 2.5MPa before being allowed to leave the factory. Each coil is standardized. Hot-dip galvanizing for corrosion protection.

2, tower structure - stable and durable.

The structure of the cooling tower is simple, reasonable, stable and durable. The water collecting tank and the tower body are made of hot-dip galvanized steel

The board has excellent anti-corrosion performance and can be used normally for more than 15 years. It can also be made in part or all of 304 or 316L stainless steel according to user needs.

3, exhaust device - reliable operation.

The high-efficiency airfoil type FRP material or aluminum alloy fan used in the fan has low noise, large air volume and stable operation. It is balanced by the factory to ensure its stability.

4, air duct device - beautiful and durable.

Made of high-quality polyester resin and gel coat or hot-dip galvanized steel plate, excellent grade non-alkali fiberglass cloth and auxiliary materials. Each product is guaranteed to be of good quality and use for more than 20 years through first-class molds, advanced equipment, qualified personnel, standardized operation and rigorous inspection of final output.

 

5, sprinkler device - ideal for cloth water.

The spray pipe is made of UPVC pipe, which is light in weight, low in water flow resistance and corrosion resistant. It can be used for more than 20 years. High-quality ABS nozzle, uniform spray, high flow coefficient, no blockage, easy to replace. It adopts high-flow low-lift pump, F-class insulation for outdoor motor, and protection class IP55. The stainless steel filter mesh can effectively isolate debris, and the low water pump suction port ensures smooth water absorption. The entire pump unit runs smoothly and reliably, and is easy to maintain.

6, water collection device - drifting water is minimal.

The water collecting device adopts a PVC high-efficiency water collector, and the floating water is so low that people cannot perceive it, which is negligible. Light weight, non-corrosive, oxygen index greater than 40, good flame retardant performance. It can also be made of stainless steel according to user needs.

7, maintenance management - simple and easy.

The whole tower has advanced design, reasonable structure, excellent material and exquisite workmanship. The long-term continuous operation is stable and reliable, and the cooling tower failure rate is extremely low, which can reduce the maintenance to a minimum. In order to facilitate the necessary maintenance, the maintenance ladder and the inspection port are provided. All the louvers with anti-sunlight and splash-proof function can be disassembled and assembled at will, and it is convenient to enter the tower from the upper part and the lower part of the tower.

 

Maintenance tips and specific maintenance methods for cooling towers

(1) Make a record of the operation of each component and workflow

When the cooling tower is built or installed and put into operation, the design unit or manufacturer shall provide all the characteristic data of the cooling tower: including thermal characteristics, resistance characteristics, water load, heat load, ambient temperature (dry and wet bulb temperature), and cooling range. , air flow rate, power consumption, wind blow loss, evaporation water volume, supplementary water volume, concentration ratio, fan power consumption, water pressure into the tower, etc., the relevant branch of the use unit should provide cooling according to the above design unit or manufacturer All the characteristic data and contents of the tower are well recorded.

(2) In order to check the operation effect of the cooling tower and the cooling capacity, an indoor test or an identification test of the running cooling tower at the production site is required. In order to ensure the normal operation of the glass fiber cooling tower, not only must the technicians of the cooling tower test research, but also have a whole

A complete and compliant test method, and must be equipped with a set of test instruments and instruments, such as thermometers, micro pressure gauges, pressure gauges, sound level meters, etc.

(3) Cooling tower cold water collecting pool should maintain the water depth of the pool to prevent cavitation. The freeboard height of the collecting pool is 15~30cm. The following is the effective volume of the pool. The water level of the cold water collecting pond should be maintained at a fixed level. , need to adjust the supplementary water valve as needed. For cross-flow cooling towers, if the operating water level is lower than the design requirements, air baffles should be installed below the original water surface to prevent air bypass. The cold water pool should be cleaned occasionally to remove the sludge and adherents deposited on the bottom of the pool, remove the debris dropped by the packing and its support, keep the grille of the water pump suction port clean, and occasionally check the leak of the collecting pool. Pay attention to whether the acid and water quality stable drug dispensing device is operating normally. The amount of supplemented water and the amount of sludge discharged are closely related to the water quality control of the circulating water. The dosage should be adjusted in time according to the requirements of the system to maintain normal operation.

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