DOE OSTI2018
Cooling towers are an integral component of many refrigeration systems, providing comfort or process cooling across a broad range of applications. They are the point in the system where heat is dissipated to the atmosphere through the evaporative cooling process. Cooling towers are commonly found in industrial applications and are also commonly applied to water cooled chilled water plants in medium to large commercial buildings. Cooling towers used in medium to large commercial buildings are the focus of this paper. Cooling towers consume a large amount of water. Cooling tower related water consumption is one of largest potable water loads within buildings in the United States, with over 26% of water use associated with heating and cooling. Reducing water consumption is a priority for the General Services Administration (GSA) due to Executive Order 13514, Energy Policy Act of 1992, and regional water shortage concerns. These factors have brought about the investigation of cost effective opportunities to reduce water use, such as alternative water treatment (AWT) technologies for cooling towers. Traditional water treatment approaches rely on chemicals to extend the ability of the water to hold scaling minerals in suspension, minimize corrosion, and prevent biological growth. This treatment protects the chillers and cooling tower equipment, however even when chemicals are used regularly, a certain percentage of condenser water must be blown down and made up with fresh water to maintain system water quality parameters. In addition, the use of chemicals sometimes creates a waste issue and can cause building owners to incur additional fees such as disposal or sewer charges. The current state of water treatment in GSA buildings is to contract for a fixed fee with a company specializing in a conventional chemical maintenance. There are many vendors of AWT systems. This project assesses the effectiveness of one technology provided by Dynamic Water Technologies (DWT). This project assesses the effectiveness of DWT for lowering GSA operating costs while maintaining proper water treatment. The application of the DWT technology in place of traditional chemical water treatment has the anticipated benefits of: - Saving water and water/sewer costs by reducing the amount of blowdown required due to being able to remove scale causing minerals that allows the system to operate at a higher cycles of concentration - Eliminating the need for water treatment chemicals for scale, corrosion, and biological growth - Increasing chiller efficiency by preventing scaling and removing some of the existing scale, which improves heat transfer - Maintaining very low corrosion rates. The technology was installed at the Juliette Gordon Low Federal Building located in Savannah, Georgia. The building has two cooling towers utilizing traditional chemical water treatment for the cooling water circulating through the two chiller condensers. Measurement at the site includes the flow of makeup water to the cooling towers and the blowdown flow rate from the cooling tower basins. Additionally, energy measurements include the electrical energy from the chillers, chiller water pumps, condenser water pumps, cooling tower fans and the energy used by the DWT skid and slip stream pump.