(The good news is that there is no need to do Bernoulli’s calculations yourself: All of the necessary information is readily available from all cooling tower manufacturers.)įIGURE 3. This is derived from Bernoulli’s equation and the relationship of pressure and flow. Equalization - the process whereby multiple cooling tower basins are mechanically connected through a piping system to allow for correction in the water-basin level - occurs during operation.įor proper equalization piping, assuming a 1” head differential, the equalizer lines are sized for a 15 percent flow imbalance between cells. When two or more cooling towers are integrated into a common condenser water system, equalization of all the cooling towers is required for a properly operating system. Concerns and Caveats in Piping Multiple-Cell Cooling Towers It provides better hydraulic control as you sequence on and off additional machines, and it is typically inconsequential to the overall project cost.
However, this design approach is easily justified.
This additional layer of automated control typically spurs the most dialogue within the engineering community as compared to the more commonly used manual isolation valve. Modern multiple-cell cooling tower configurations utilize common headers for both the supply and return lines.Īdditionally, it is a better engineering practice (and the recommendation of this author) to provide automatic control valves at the outlet of each tower’s equalizing line. In these systems, the use of automatic control valves for proper operation is imperative at the inlet (CR) and outlet (CS) of each cooling tower.įIGURE 2. Today, multi-cell cooling tower configurations have common headers for both the supply and return lines (figure 2). This seems backward from what might be expected, but it reflects the fact that the chiller is the central component in the system design. The condenser supply piping (CS) is the piping leaving the cooling tower and supplying the chiller. The condenser return piping (CR) is the piping supplying the cooling tower but returning from the chiller. One note about condenser piping nomenclature: It is counterintuitive. Multi-cell cooling tower configurations that have 100 percent independent systems have limited redundancy. Condenser piping systems are designed to be streamlined to keep capital costs low while yielding the most energy-efficient solution.įIGURE 1. The evolution of a more sophisticated system is due in part to the advent of advanced controls and the operational flexibility of modern chillers, cooling towers and other mechanical equipment. Piping Scenarios for Multiple-Cell Cooling TowersĬooling tower piping systems have evolved over the years from simplistic, dedicated hydraulic loops that lacked complexity to large-volume, multiplexed systems that offer peak operational efficiencies (figure 1).
Additionally, these multiplexed condenser water systems incorporate sufficient redundancies such that critical operations are never in jeopardy of being nonoperational. It also affords facility managers the opportunity to operate their plants at peak efficiencies. This configuration allows for the correct staging of equipment as the process or facility loads vary. Most larger cooling tower systems use a multiple-cell configuration. It seems simple, but how effectively a cooling tower piping system is designed and installed can have a critical impact on system efficiency, functionality and even safety. The essential element for a cooling tower to function is water, and water needs to be delivered through a piping system. This is the basic premise behind evaporatively cooled equipment. When you get out of the water and are still damp, what happens when a breeze blows? You feel cool as the breeze evaporates the water on your skin. Cooling towers are used in water-cooled refrigeration, industrial process systems and commercial HVAC air-conditioning.Ī simple way to appreciate how a cooling tower works is to consider the “beach effect.” On a 95☏ (35☌) day with 95 percent humidity, a dip in the water is incredibly refreshing.
The towers themselves are enclosed, steady-flow devices for cooling water by evaporation through direct contact with air. Cooling towers work on the principle of heat rejection: They extract heat to the atmosphere through evaporative cooling. For most industrial manufacturing, electric power generation and even air-conditioning needs, cooling towers are a critical element of the design.