Selecting a Liquid Chiller
Chiller system sizing, location, fluid selection and chiller maintenance procedures all affect a chiller’s
cooling performance. Overlook one of these variables, and your plant likely will waste thousands
of dollars on excess energy consumption and equipment repair.
By following some basic guidelines before, during and after installation of your liquid chiller, you can avoid these problems and ensure that your chiller system will provide the required cooling capacity at a
maximum level of efficiency and reliability.
Proper Sizing and Location of Chillers
Selecting the appropriate chiller size is crucial to ensuring efficient operation. Sizing parameters should be determined by performing a thorough calculation of the maximum cooling and process load demands. It is important to understand that cooling loads fluctuate over time, and the size or capacity of a chilled water system must be designed to accommodate these load changes. Load requirements, as well as leaving water temperature (LWT), pump size, pump type, and pump pressure abilities should also be evaluated. Also various temperature control schemes are employed in chiller temperature control. Those systems that cycle the compressor are apt to wear out sooner than one that operates continuously and has hot gas bypass as a way to solve varying load conditions. Opti Temp’s cooling systems use “Advanced Refrigeration Capacity Control” (ARCC) circuitry. This patented industry leading circuitry allows the unit to operate from “zero load to full load” (without cycling the compressor) while providing excellent temperature stability. Location also is an important consideration. The chiller system should be installed as close as possible to the process for the following reasons
• To reduce the amount of piping required and thus minimize the amount of ambient heat
absorbed by the heat transfer fluid through the piping.
• To reduce the volume of fluid required to fill the circuit, and thereby speed the system’s
temperature response during startup and operation.
• To improve heat transfer characteristics in the refrigeration circuit by decreasing system
pressure drops and increasing fluid flow rates.
Both air- and water-cooled chillers should be located away from any equipment that might restrict or impede the chiller’s operation. Placement near walls and external heat sources also should be avoided to ensure that airflow and component accessibility remains unobstructed for proper operation and maintenance.
Fluid Selection for Chiller Systems
Fluid type, quality and treatment should be considered when selecting a fluid for use in a chiller system. Industrial non-automotive glycols with corrosion inhibitors suitable for chiller systems should be used for most applications such as Opti Temp’s OptiShield corrosion inhibitor product, available in several convenient packaging sizes.
When attempting to operate below normal operating temperatures (45°F/7°C), a premixed solution of water and glycol should be used to provide freeze protection. In closed-loop cooling systems and installations where ambient air temperatures are higher than normal, algaecide and biocide additives might be required to ensure that the water loop remains clean.