Editor's note: The following is an adaptation of "Design Considerations for Cooling Tower Systems with Critical Demands," presented at the 2010 Cooling Technology Institute Annual Conference, held Feb. 7-11 in Houston. To purchase the full paper, go to http://bit.ly/clPzdL.

Several factors need to be addressed prior to determining the appropriate cooling-tower system for a facility with critical demands. Locations, such as data centers, medical centers, airports, and electronic-chip manufacturers, require special considerations in addition to the requirements of an average cooling-tower system.

This article reviews the normal design considerations encountered in designing custom-built cooling-tower systems with critical demands and includes special design considerations necessary for mission-critical cooling facilities. Such considerations include building codes, customer requirements, environmental constraints, operational components, fire resistance, safety compliance, minimum maintenance, and a long service life that are mandatory for these critical-cooling applications.

Design Considerations
There are numerous factors to contemplate when designing any custom-built cooling-tower system. Designing a cooling-tower system with critical demands just intensifies the design process. Not only do the normal considerations for all cooling-tower systems apply, but the special demands that make the cooling system "critical" must be addressed as well.

Building Codes
Building codes are the foundation on which all cooling-tower systems are designed. Examples of building codes include:

• The International Building Code, which is developed and maintained by the International Code Council independent of the jurisdiction responsible for enacting the building code.
• State and local building codes.
• Hospital building codes.

Building codes dictate the basic design of the cooling-tower system. Once basic requirements are established, a cooling-tower-system design must be evaluated to determine if it meets/exceeds the critical demands of the system. For example, let's say a building code requires a cooling-tower system to meet 90-mph wind loads. Because this is a cooling-tower system that has critical demands, the wind load might need to be increased to 120 mph to ensure a stronger cooling-tower system.

Customer Requirements
A cooling-tower system's location influences several of the issues that must be addressed during design. Therefore, much thought should be given to a system’s placement. The requirements for a "grass-root tower" built in a clear field are different than those for a tower constructed to fit in or around existing buildings and equipment. In the current market, real-estate limitations result in cooling-tower systems being constructed not only at grade, but on rooftops. Basins may need to be elevated to meet location requirements.

Often, a customer will request a cooling tower be built to replace an existing tower. A new tower with increased thermal capacity is designed to fit within the old cooling tower's water basin. Additionally, the new tower design may be restricted by the old cooling tower's horsepower and pump head. Because the new cooling tower is replacing an existing cooling tower, the demolition of the old cooling tower and the installation of the new cooling tower usually are scheduled with limited downtime for the entire project.

Some of the more common customer requirements include:

• An access platform around the basin or piping/valves.
• A parapet wall to hide mechanical equipment.
• An inlet screen.
• A ladder and cage.
• A stairway.
• Conduit support.
• Colored walls to improve aesthetics.
• Internal walkway inspection.