FAQ

FAQ

The fundamental difference between cross-flow air cooling tower and counter-flow air cooling tower is how the air being pulled into tower is interacting with the process water being cool.

 

In a cross flow tower, water will start at the top of the fill and work its way down the fill, while air travels horizontally across the direction of the falling water.

 

The way across flow cooling tower is designed allows for a really large plenum. The large plenum area allows for, in some cases, full-sized access doors. It allows us to inspect the cold water basin, looks at the drift eliminators, and even room for mechanical access platforms so that we can check out and service the motor and gearbox and fan at the top of the cooling tower.

 

Another fundamental difference between cross flow and counter flow air cooling tower is the water distribution system. On a cross fill of cooling tower,  The process water or condenser water is piped up to the top of cooling tower, going through HC valve or a flow control valve and then distributing into water distribution basin. The hot water distribution based on a cross flow tower is gravity-fed. One of the the benefits of a gravity fed distribution basin is the ability for it handle variable flow or low flow applications. We can go down to as 30% of design flow and still be able to predict the performance of the cooling tower.

 

While, In the counter flow tower, water enter the side of the cooling tower through inlet pipe and been spread by water distribution system, then drip into the film. Due to gravity, it gonna to pass through the fill and drop out the base of the film and fall into the water basin. Once the water is fall into the base of the cooling tower, it will be discharge by the pipe and go back to the process. While the air enters around the base of the cooling tower through louvers, the it gonna be drawn up through the fill, flowing upward and away from the tower. The water goes down and air goes up. They are in opposite directions, 180 degree. That is why we called counter flow cooling tower.

1.The introductionof closed cooling tower.

Closed cooling tower, also called evaporative air cooler, the tube heat exchanger is placed in the tower to ensures the cooling effect through the heat exchange of circulation air, spray water and circulating water. Because the process is a closed cycle, it can make sure the water is not polluted, which effectively protects the efficient operation of the main equipment and improves the service life. When the outside temperature is low, you can stop the sprinkler system to achieve water saving effect.

 

2.Principal of closed cooling tower

Closed circuit cooling towers or fluid coolers operate just like the open type, but dissipate the process fluid heat load into the ambient air via a heat exchange coil. This isolates the process fluid from the outside air, keeping it clean and free of contamination in a closed loop and creating 2 separate fluid circuits:

  • An external circuit, in which spray water circulates over the coil and mixes with the outside air.
  • An internal circuit, in which the process fluid circulates inside the coil.

3.Closed cooling towers Advantages

1.No scaling, no pipe blockage

2.Small floor area

3.Water saving and energy saving

4.High cooling efficiency

5.Not affected by the environment,environment-friendly

The advantages of evaporative condenser are as following:

  • Save investment cost. Theevaporative condenser integrates the condenser, circulating water tank, circulating water pump and water pipe, which reduces the equipment such as cooling tower, circulating water pump and water pipe, and also reduces the cost of processing and installing individual components in the condenser system. Because of the efficient use of evaporative cooling and heat exchange, the evaporative condenser can effectively reduce the heat exchange area, the number of fans and fan motor power consumption.
  • Energy saving. 10%~20% electrical energy can be saved due to low pressure condensation of refrigerantcompared with shell &tube condensers.
  • Water saving. The evaporative condenser water consumption is only 1‰-3‰ of the heat exhausted, making the actual operation of the evaporative condenser water consumption is 5%~15% of the cooling tower system, saving water resources .
  • Good heat exchange performance. Due to the large latent heat of vaporization of water, the amount of heat absorbed by a unit of water is large. Inside and outside the heat exchanger, water, air, and a cooling medium alternately flow, making the heat transfer faster and the heat transfer efficiency increase, thereby achieving efficient heat exchange.

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Cooling tower can be widely used in many industries, such as power industry, coal chemical industry, petroleum and petrochemical industry, refrigeration industry, metallurgical industry.

  • Waste heat recovery power generation technology.

Waste heat power generation in accordance with the working fluid can be divided into steam turbine power generation technology with traditional waste as the working fluid and with low boiling point as working fluid organitic power technology. Above 350℃ heat mainly use steam turbine or expander power generation system. For most of abandoned waste heat below 350℃ is more suitable to use economically viable organic Rankine cycle cogeneration technology.

Waste heat power generation is a technology that uses excess heat energy in the production process to convert it into electrical energy. Waste heat power generation is not only energy-saving, but also environmental protection. The waste heat used for power generation mainly includes high temperature flue gas waste heat, chemical reaction waste heat, waste gas, waste liquid waste heat and so on.

Waste heat power generation can be divided into traditional steam turbine power generation technology with water as working medium and organic working medium power generation technology with low boiling point working medium according to working medium. The waste heat above 350℃ mainly uses the power generation system composed of steam turbine or expansion unit. For a large amount of discarded low-temperature waste heat below 350℃, it is more suitable for economically feasible organic Rankine cycle waste heat power generation technology.

Winter antifreeze solution of closed cooling tower and evaporative condenser

The evaporative condenser( closed cooling tower) is widely used in metallurgy, electric power, petroleum, chemical and other industries, it has the advantages of water-saving, energy-saving, high heat exchange efficiency and so on.

The temperature is usually below zero in winter, and the problem of frost prevention in the operation of closed cooling tower has become increasingly prominent. If it is not solved well, the heat exchange tubes or other parts of the cooling tower may be damaged by freezing. So, it is necessary to consider the issue of winter  antifreeze solution of closed cooling tower. There are several solution for different operation condition.

  1. )The closed cooling tower is barely used in winter

 If the closed cooling tower does not need to be operated in winter, the spray water and circulating water inside the heat exchange tube must be drained when it is shut down.

  Specific operation sequence:

       ① Turn off the power of the axial flow fan and spray water pump successively;

       ② Close the equipment inlet valve, open the tube bundle vent and drain sealing cover, connect the DN32 water pipe to the tube bundle drain pipe to introduce the water in the tube bundle into the water tank, then close the water tank replenishment valve, open the drain valve to empty the water tank, and turn on the spray water pump The drain outlet drains the water in the pump body;

       ③ Open the bottom line plug of each pipe pass, and use high-pressure air to drain the residual water in the pipe;

       ④ Install the wire plug to the equipment, and cover the tube bundle to vent and drain.

       (For a closed cooling tower with a flexible coil structure, when it is out of service, open the inlet and outlet valves of the equipment to drain the medium in the pipe)

 

  1. )The closed cooling is occasionally used in winter

In winter, the evaporative cooling equipment has a large heat dissipation capacity. For a system with multiple equipment running in parallel, some spraying water and fans can be stopped to reduce the heat dissipation of the equipment to achieve the purpose of antifreeze. For equipment with water tanks, it should be installed as far as the water storage tank or underground drainage pool. When the spray water temperature is lower than 10℃, the water in the water collection tank should be emptied.

For the antifreeze of a small circulating water system, consider adding glycol and then air-cooling operation; adding antifreeze can solve the problem at one time. Ethylene glycol solution is the main component of most antifreeze liquids. The disadvantage is that the price is higher (≈$1400/ton).

Ethylene glycol solution is the main component of most antifreeze liquids. Refer to the following table for antifreeze formula:

Ethylene glycol(wt%)

0

10

20

30

40

50

58

80

90

100

Freezing point(℃)

-0.0

-3.5

-8

-15

-24

-36

-48

-47

-59

-63

 

  1. )The closed cooling toweryear-round operation  

When the ambient temperature is 0°C ~ -5°C, anti-freezing measures must be taken when the machine stops for more than 10 hours;

When the ambient temperature is  -5°C ~ -10°C, anti-freezing measures must be taken when the machine stops for more than 5 hours;

When the ambient temperature is lower than -10°C, anti-freezing measures must be taken when the machine stops for more than 1 hour.

  1. What is air-inlet grille?

The inlet grille is made of PVC material by molding and bonding. The outer frame can choose hot-dip galvanized steel plate, glass steel plate, stainless steel plate. This product has a good air intake effect and has the effect of blocking the water splashing out of the cooling tower. It can be used at the air inlet of the closed cooling tower or other occasions where the air intake blocks the floating water.

And The height and width of the inlet grille can be customized.

 

  1. What is the advantages of using PVC inlet grille compared with inlet louvers?

The PVC inlet grille is mainly applied to the air inlet of a closed cooling tower. Compared with ordinary inlet louvers, this inlet grille has at least the following three advantages:

(1). The appearance is beautiful. Many foreign closed cooling towers use this kind of air inlet grille.

(2). Do not splash water outside the cooling tower. This kind of inlet grille needs to turn three times to reach the outside of the cooling tower, so there will be no splashing of water droplets outside the tower.

(3). Prevent direct sunlight from entering the cooling tower water tray. The cooling tower water tray exposed to direct sunlight is easy to breed bacteria and algae, and the use of this type of PVC inlet grille will not cause sunlight to enter the water tray. Therefore, the cooling tower circulating water or spray water will not grow moss.

(4). Maintenance is convenient. This kind of air inlet window can be customized. The size of the air inlet window can be specified according to the actual cooling tower. During installation, you only need to gently push into the cooling tower and clamp it tightly. Maintenance is very convenient.