Closed type cooling tower is the deformation and development of traditional closed type cooling tower. The water in the reservoir at the bottom of the tower is pumped by the circulating pump and sent to the outside of the pipe for uniform spraying. It is not in contact with the process fluid hot water or refrigerant and the air outside the pipe. It becomes a closed type cooling tower, which enhances the effect of heat and mass transfer through spraying water.
Closed type cooling towers are classified according to flowing water, including cross flow, counter flow and mixed flow. Mixed flow and cross flow are generally referred to as the same inflow.
1. Counter flow closed type cooling tower
(1) Water is in the filling material of the closed type cooling tower. Water flows from top to bottom and gas flows from top to bottom into the opposite closed type cooling tower.
(2) The countercurrent closed type cooling tower has good thermal characteristics and is divided into three refrigeration sections:
① The temperature of the indoor space from the rotating nozzle to the top of the filler is high, so the calorific value can still be transmitted to the gas.
② Heat exchanger section filled with feed water and gas.
③ The cooling circulating water from the filling material of the closed type cooling tower to the water spraying section of the indoor space of the water collecting reservoir is called tail effect. The temperature in the north can be reduced by 1-2 ℃. In general, the filling volume of countercurrent closed industrial cooling tower is 20% smaller than that of cross flow closed type cooling tower. The whole heat transfer process of countercurrent tower is more effective and the cooling efficiency is higher.
(3) The water distribution system is not easy to be blocked, the watering filler is kept clean and not easy to aging, the return of moisture is small, and the anti freezing and ice melting measures are easier. Multiple units can be designed in combination. In winter, a single unit can be combined with the required water temperature and water volume, or all fans can be stopped.
(4) The construction, installation and maintenance of the project is very easy and low-cost. It is common in central air conditioning and large, medium and small refrigeration and cooling circulating water of industrial production.
2. Cross flow closed type cooling tower
(1) The water is in the filling material in the closed type cooling tower, the water flows from top to bottom, and the gas flows into the tower body from the level outside the tower. Common in residential areas with strict noise regulations, it is a refrigeration cycle system tower widely used in the household appliance industry.
Advantages: energy saving, low water pressure, small wind resistance, also equipped with low-speed motor, no dripping noise and wind noise, and convenient maintenance of filler and water distribution system.
(2) It is often used in residential areas with strict noise requirements. It is a cooling circulating tower widely used in the air conditioning industry. It should be noted that when the closed type cooling tower is more than 40% of the conventional heat exchange, there should be more filler volume, the filler is easier to age, the water distribution hole is easier to be blocked, the anti icing is worse, and the moisture reflux is larger.
Closed type cooling tower is suitable for various cooling systems with high requirements for circulating water quality. It has application prospects in power engineering, chemical plant, steel, food and many industrial departments.
The initial investment cost of closed type cooling tower is high, and the cost is three times that of open cooling tower. (but the recovery value of closed type cooling tower is 80000-100000 ten years later, and the open type cooling tower is almost worthless.) we should take a long-term view and consider the pros and cons of things from all aspects. From the perspective of the industry prospect of cooling tower, closed type cooling tower has become the mainstream.
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