Cooling Towers: Explaining Their Roles and Types
Cooling towers are devices designed to extract waste heat to the atmosphere in systems that generate too much heat which, if not extracted, may hinder the functionality of the system. Majorly, cooling towers are of two classes depending on whether they rely on vapour or air to attain their cooling function (Cooling Technology Institute). Those that rely on air to attain their function of cooling usually are installed in closed circuit systems and they rely on air in order to cool the working fluid to dry bulb air temperature. Those that rely on vapour rely on water which when it evaporates, it removes excessive heat to an extent that the working fluid nears the wet bulb air temperature. Cooling towers must at all the time work effectively so that the structures that use them maintain their proper functionality.
Different structures have been associated with the use of cooling towers. Structures like oil refineries, thermal power stations and chemical processing plants have to use cooling towers in order to extract the excessive heat they generate to the atmosphere. The history of cooling towers goes back to the 19th century with advent of the condensers that were used with steam engines. The condensers were mainly used to cool the steam that was ejected out of the turbines that helped run the steam engines.
This cooling was effective in reducing pressure which could otherwise have led to a situation in which there could be high steam consumption, which could directly translate to high energy consumption. These same principles were applied to early cooling towers. With the heat generated leading to inefficiencies in machine or system operation, there was a need to cool down the systems so that they could run normally.
Early cooling towers were just simple structures that relied on air to be pumped through them in order to work as cooling towers. Efforts to make better cooling towers however began as there came up the need to develop complex machines (Spxcooling.com). Through the early 20th century, no effective cooling tower had been produced but designs on how the existing towers could be improved had surfaced. It is not until 1918 that the first modern cooling tower was built.
This was patented to two Dutch citizens who built the cooling tower in Heerlen. This first cooling tower was hyperboloid structure that stood several metres high from the ground. Ever since, the cooling towers have developed in terms of shape and functionality to an extent that they are of ultra-high effectiveness in these modern times. Given the different needs for these cooling towers, there has arisen a need to effectively classify them in order to ensure easy identification in order to guarantee maximum efficiency from the use they may be put in (Office of Energy Efficiency & Renewable Energy).
Cooling towers can be categorized and placed into their effective types depending on the following parameters. Cooling towers can be categorized by use, categorized as per to how are built, they can be categorized as per to their heat transfer methods, they can also be categorized by the air flow methods they employ, and they can also be categorized as per to their air to water flow methods. The upcoming section will give a summary of the types of cooling towers that can be found in each of the following categories. Each of that type will be described regarding its functionality and efficiency as per to the needs at hand.
1. Cooling towers as per use:
Cooling towers are usually defined by their use. When cooling towers perform a specific task, they tend to be associated with that use during the quest to name them. For instance, there are two main uses of cooling towers:
a. Ventilation and air conditioning cooling towers
b. Industrial cooling towers
Industrial cooling towers, as the name suggests, are used in the scope of industrial purposes. The cooling towers in oil refineries, chemical processing plants and other industrial plants all use the industrial type of cooling towers. These types of cooling towers have a unique set of demands that cannot allow them to be used anywhere else apart from home.
2. Cooling towers as per to how they are build:
Cooling towers can be classified as per to their build. This type of classification includes the following types:
a. Package type
As the name suggests, this type of cooling towers are packaged for use in the sense that they can be loaded onto trucks and used in the field in which they are needed. They are majorly used in firms that do not require huge demands for cooling due to their limited ability to handle high temperatures.
b. Field erected
These are the type coolers that demand that they be build while on the field as they are usually very large to be transported. They may include huge pipes and other structures whose transportation once joined may be a huge challenge. These are mostly used in organizations that demand high levels of heat extraction like the refineries and the chemical processing plants.
3. Cooling towers as per to heat transfer methods
The main types of cooling towers as per to their heat transfer methods include:
a. Fluid coolers
Fluid coolers cooling towers use the technique of cooling the working fluid in such a way that it is passed through a pipe which is in turn sprayed with another cooling liquid which in most cases is water.
b. Dry cooling towers
This use a technique of convective heat transfer in which the cooling of the working fluid occurs by its being passed through surfaces that will see it cooled without using other substances except air.
c. Wet cooling towers
Wet cooling towers usually involve the usage of water in such a way that they excessive heat from the working fluid is used to heat up the water which significantly helps it to cool to its desired temperatures.
4. Cooling towers by air flow methods
The main types of cooling towers as per to the air flow methods include:
a. Natural draft cooling towers
This type of cooling tower uses natural means to see heated air escapes to the atmosphere. This naturalness is attained from the buoyancy principles in which it is explained that naturally, warm air will have its way up than cold air due to their differences in density.
b. Mechanical draft cooling towers
These types of cooling towers use fans to drive heated air out of the system. The fans are powered by some source of power. These cooling towers are further classified into induced draft and forced draft cooling towers.
c. Fan assisted natural draft
This combines the two techniques thereby making it even more effective in its functioning as a cooling tower.
5. Cooling towers by air to water flow methods
There are two types under this categorization. These are:
a. Cross flow cooling systems
In this type of cooling tower, air flow is directed perpendicularly to water flow. The major benefit of this type of cooling tower is that the water distribution is maintained due to the gravitational action which allows smaller pumps hence reduced energy consumption.
b. Counter flow cooling towers
This cooling tower, water and air flow in opposite direction. The major benefit of this is that the cooling is more effective as action of water in the spray breakup which is as a result of the techniques used to develop it makes the heat exchanges even more effective.
The current levels of innovation may see to it that new types of cooling towers are created. But to date, the level of development that has been attained in the cooling tower systems has seen an increase in the efficiency of such towers thereby bringing in instances of reduced consumption of energy. This has been majorly cited as the force behind the profitability behind the processing firms that have to erect cooling towers in order to effectively operate.
Cooling Technology Institute. ‘What Is Cooling Tower? Detail’. N.p., 2015. Web. 2 Mar. 2015.
Office of Energy Efficiency & Renewable Energy. ‘Best Management Practice #10: Cooling Tower Management | Department Of Energy’. N.p., 2015. Web. 2 Mar. 2015.
Spxcooling.com,. ‘Cooling Tower Library Â Corporate Publications Â» Cooling Tower Fundamentals’. N.p., 2015. Web. 2 Mar. 2015.