PROCESS COOLING

When considering which type of process fluid cooling system is best for your application it is important to determine the process fluid medium, desired temperature, and the significance of operating cost versus initial investment. There are often times multiple solutions to a process cooling application and the following is intended to provide a basic outline of the types of systems available and where they are best used.

Process cooling is moving heat from where it is not wanted (the process) and ultimately results in putting it into the air outside the manufacturing facility. Heat transfer usually involves the use of some sort of heat transfer media, usually a fluid like water or a glycol solution, to transport the heat from the process equipment to the cooling system.

The first step is to understand the temperature the process cooling fluid needs to be in order to properly remove heat from the process. This is typically specified by the process machine manufacturer and is based on the flow of fluid and the required temperatures of their heat exchangers. There are three basic types of process cooling systems to consider.

Fluid Coolers

Fluid Cooler systems are commonly used for applications with warmer temperatures. They consist of copper tubes with aluminum fins and fans that act like a radiator to cool the process fluid using ambient air. The coolest practical leaving fluid temperature is about 10°F warmer than the air entering the fluid cooler. Compared to cooling towers, fluid coolers are not as energy efficient, have a higher initial cost, and have a larger footprint; however, they have much lower maintenance requirements and use less water than cooling towers. Of the three type of process cooling systems, the operating cost of fluid cooler systems typically falls somewhere between that of a cooling tower and chiller system.

Cooling Towers

Cooling tower systems are used for applications where a fluid cooler is not able to get cold enough. A cooling tower system can provide a reliable source of cool water year round in the 70°F to 100°F temperature range. Cooling towers work through the process of evaporation. Water is sprayed over plastic cooling tower fill, which creates a large surface for water to evaporate. A fan moves air through the tower to induce evaporation which in turn cools the water. The coolest practical leaving water temperature in summer is about 80°F due to air temperature and humidity. Cooling tower systems are typically the least expensive of the three types of systems to operate; however, the maintenance requirements for filtration and water treatment is the highest of the three.

Chillers

Chiller systems are used in applications where neither a fluid cooler nor cooling tower system can get cool enough to meet the requirements for the process. In a chiller, refrigerant is used to pull heat from the process fluid and transfer it to ambient air or cooling tower water. Typical applications are for 50°F water, but most chillers have a practical process fluid set point range of 20°F to 80°F. Of the three types of cooling systems, chiller systems are the most expensive to purchase and operate. Chillers require some form of cooling to their condensers, which is where the refrigerant gas that was boiled using the process heat is condensed back to a liquid. The three types of chiller condensers are shown below.