Cooling tower - what is it? Types, characteristics, device and principle of operation
The operation of industrial facilities is associated with a multitude of technological processes, some of which are carried out by heat and cooling facilities. They are designed to regulate the temperatures of working environments and communication infrastructure in CHP and NPP systems. The most noticeable and productive object of this type is a cooling tower. What it is? In the general sense, it is a tower structure, inside which microclimatic processes of processing various media take place by directing atmospheric air. In practice, there are different types of this design, differing in both technical device and functionality.
Tower cooling tower construction
The most common formation of the cooling tower, which is often performed on a reinforced concrete base in the form of a cone.Inside there are obligatory functional blocks - the water supply system, the sprinkler, the tank and the accompanying valves and fittings. The classical tower cooling tower, the photo of which is presented above, can serve not only water as a working resource of a power unit, but also technical liquids with fuel cells. The active exposure environment is outside air, for the entry of which openings are provided in the lower part (sole) of the structure. Through the ventilation ducts, the air mass rises and cools the target liquids in the tanks due to natural thrusts.
Pros and cons of tower cooling tower
Among the advantages of tower structures can be noted the absence of electricity consumers. That is, functional systems and units do not need a special connection of power sources and operate autonomously. The same is emphasized in the implementation of the air intake device of the cooling tower, the principle of action of which is based on the natural replacement of warm air with cold air. However, the implementation of ventilation and cooling systems may be different.If we talk about the drawbacks of the tower cooling tower, the high cost of construction and the low potential of the cooling effect will come to the fore. And in the winter time, special servicing measures are required to protect communications from hypothermia.
Ejector cooling tower design
The main difference of this kind of cooling tower is the use of steel in the body. And not in part, but as the main material. A high-pressure pipeline with ejectors - distribution pipes is installed inside the structure. During the operation of the functional unit, water is sprayed through the ejector nozzles with the subsequent supply of air flows to the vacuum zone. Contact with cold flows cools fine droplets of liquid droplets, which causes the high efficiency of this system from the point of view of accomplishing the target task. However, the performance of a metal cooling tower with ejectors is not provided by itself through natural physical processes, as is the case with tower structures, but due to the operation of pumps. Thanks to pumping stations, sufficient pressure is maintained in the spraying mechanisms, which ultimately simplifies the cooling process.
The principle of operation of the cooling tower
As you can see, the task of cooling the target liquid media are performed by blowing with streams of cold air. At the same time, additional and intermediate functions like evaporation can be performed. Each time as the condensate is released through the water supply circuits, it is replenished in the working area. Either the capacities of the ejectors are filled, or the liquid is supplied to the walls of the sprinkler surface. It is also important to emphasize the presence of filtration barriers that separate the water channel from the tower of the cooling tower. The principle of operation of the cleaning membranes is determined by the purpose of the serviced liquid - at a minimum, a coarse large-fractional delay of mechanical impurities is realized, but in modern systems complex thin water treatment with elements of biochemical filtration may be present.
What happens to the liquid after cooling? It also depends on the nature of the overall process, in which the cooling tower is indirectly involved. As a rule, hot water is a used product of production, so it is discharged into connected cleaning or drainage channels.Also, a scheme of constant fluid circulation is used, in which the cooled medium returns to the primary process area for temperature regulation of equipment of the CHP and NPP.
Cooling Tower Features
The main operational parameters include performance and temperature regimes with which a particular station can operate in principle. As for the first value, large cooling towers can cool the resource at a speed of about 200 m3/ h The height of such structures is 150-170 m with a base diameter of about 150 m. Temperature values, as already noted, are directly dependent on the principle of operation of the station. For example, designs with natural air circulation work with a warm liquid at 30-40 ° C. In this state, it enters the tank, and after cooling, its temperature drops to 15-20 ° C. Does not make water ice and ejector complex. Its advantage is more likely to work with incoming temperatures in excess of 60 ° C. The degree of reduction can reach 20 ° C. The efficiency of the ejectors is also influenced by the density of the cooling tower irrigation. What is this indicator? It determines the specific value of the liquid flow rate per 1 m.2irrigated area.The optimal values fall in the range from 6 to 12 m3/ h
Features of "dry" designs
In such systems, heat-exchange structures with radiators are provided, which remove streams of already heated air. Their removal from the working platform through special channels is provided by fan installations. When assembling such constructions, engineers try to minimize or completely eliminate direct contact of the cooling (blowing) processes with heat transfer and hot flow circulation. The advantages of the “dry” cooling tower include the high quality of chilled water (no pollution, volume preservation, etc.), the ability to work with high temperatures and the durability of the construction surfaces. The minimum degree of humidification of the air environment reduces the risk of corrosive damage to the metal elements of the structure, and therefore the operational life of the equipment is prolonged.
Features of a wet cooling tower
Also, such stations are called evaporative, since their principle of operation is based on the transfer of thermal energy from a liquid to air as a result of direct contact of media.How does the "wet" cooling tower function and what is it in terms of technical device? The internal layout of functional units also provides for the presence of fan installations (separate or sectional), which remove the remaining air, but the main function of evaporation is performed by the condensation coil. It is a circuit in which a fluid circulates under the influence of high temperatures. The movement of water is completed by its spraying through small-format nozzles under intensive blowing by fans.
Cooling tower irrigation system
One of the key components of a cooling tower, on which the cooling capacity of a structure depends. Actually, the task of the sprinkler is to ensure the maximum area of the finely dispersed (drip) water distribution for contact with the air flow. This element of the infrastructure can have different structural performance - for example, there are splash, film, drip and other types of devices. Light plastic alloys based on polypropylene and polyethylene are often used as materials for manufacturing.In particular, the film sprinkler cooling tower is made of high-tech polymers, providing efficient cooling with minimal resources. But, these same devices have a number of disadvantages, among which is the clogging of the separating sections with fine suspensions and impurities. Again, it is worth emphasizing the importance of pre-filtering water, not only for the quality of the liquid itself.
Water distribution system
If the sprinkler is directly responsible for spraying, the water distributors perform uniform regulation of the flow through the nozzles and nozzles. Today, pressure distribution units are more commonly used, based on the piping system and injectors connected to them. For the manufacture of such a collector used metal and composite materials, as well as plastic nozzles. At the stage of water distribution, the cooling tower operation can be provided by autonomous torches with a radius of action of the order of 150-200 cm. The intensity of the water supply to the sprinkler will depend on the principle of the nozzle operation - this can be a centrifugal, impact or jet installation.
Fan parameters will be determined by the irrigation area. The standard system involves the use of exhaust and injection systems with different power potentials. For example, if the working area is not more than 15 m2, then the thrust of the injection fan can fully serve the functions of the duct. The design of such units is usually formed by two elements - a diffuser and impeller. Composite materials are used for the manufacture of the hull to integrate stiffeners under the hull. The diffuser can perform the task of regulating the pressure, which occurs with intensive cooling of the cooling towers at the outlet in the direction of the air flow. In turn, the impeller is formed by a combination of blades and hub, and in the process creates a constant cooling flow. The diameter of such a wheel is from 2.5 m to 20 m, depending on the scale of the structure.
With the exception of certain technical and structural solutions inside the station, the construction of a cooling tower as an industrial facility may seem fundamentally outdated.But is there an alternative to such facilities? The problems of cooling various technical liquids in large volumes are also solved with the help of spray pools and cooling ponds. But even in these cases, the same problems are observed in the form of low productivity, which are complemented by the specifics of using natural working environments. In the same pond water regularly blooms, which requires the implementation of special measures for the biological maintenance of the object.
Against this background, the cooling tower is not so bad. What is it from the point of view of the operating enterprises themselves? At a minimum, a cost-effective technological tool to support auxiliary processes for cooling work equipment. Moreover, in some cases, such processing of technical liquid is the only justified way, since the performance in terms of temperature regulation is well within the standards for discharging industrial effluents.