Question

could you give me a basic introduction about the cooling tower( the approach to wet bulb concept), plz.

Answer 1

The simplest function of a cooling tower is to cool water to a desired temperature. In the cooling tower industry, this desired temperature is referred to as the cold water temperature due to the fact that it is cooler than water entering the tower. For evaporative processes, the difference between the cold water temperature and entering wet bulb temperatures is the approach. However, there is a lot more to understand about approach than simply the difference between two temperatures.

In the HVAC industry, the term “Approach” is used to describe the difference between the tower outlet temperature (TO) and the outside air wet bulb temperature (TWB). So let’s define Approach as:

Approach = TO – TWB

Types of cooling towers

Not all towers are suitable for all applications. Cooling towers are designed and manufactured in several types, with numerous sizes available. Understanding the various types, along with their advantages and limitations, is important when determining the right tower for a project.

Crossflow cooling towers:

In crossflow towers the water flows vertically through the fill while the air flows horizontally, across the flow of the falling water. Because of this, air does not have to pass through the distribution system, permitting the use of gravity flow hot water distribution basins mounted at the top of the unit above the fill. These basins are universally applied on all crossflow tower

Counterflow cooling towers:

Counterflow towers are designed so that air flows vertically upward, counter to the flow of falling water in the fill. Because of this vertical airflow, it is not possible to use the open, gravity-flow basins typical in crossflow designs. Instead, counterflow towers use pressurized, pipe-type spray systems to spray water onto the top of the fill. Since air must be able to pass through the spray system, the pipes and nozzles must be farther apart so as not to restrict airflow.

Forced Draft & Induced Draft Cooling Towers Process:

Cooling tower fans are used on induced draft cooling towers to pull air up through the fill media. On forced draft cooling towers, the air is pushed/forced by blowers at the bottom of the air inlet louver.

Natural Draft & Fan Assisted Natural Draft Cooling Towers:

The fan assisted natural draft cooling tower (FAND) combines the advantages of the natural draft cooling tower and the mechanical draft cooling tower.