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Portable Chiller Systems Glossary: F

Flash Point

Flash Point is the temperature at which the vapors produced from Heat Transfer Fluid (HTF) will ignite (flash off) with the presence of an ignition source; the fluid itself will not burn at this temperature. Flash point is important from the viewpoint of safety, however, it is quite common for heat transfer systems to be operated at temperatures above the flash point of the fluid, as sufficient oxygen and an ignition source are not present in a closed HTF system. The danger lies in leakage, and emphasizes the inportance of regualr checks for leaks in a Chilling System, as external 'weeping' leaks from fixtures can oxidize and produce smoke (though not ignite), and internal leaking of HTF into the porous insulation of the chiller can actually cause the HTF to ignite, as the heat generated by oxidation is trapped in the insulation and can exceed the fluid's auto-ignition temperature.

Flow Rate

In fluid dynamics, the Volumetric Flow Rate, (usually referred to in Chiller systems as the Flow Rate) is the volume of fluid which passes a point per unit of time. The Flow Rate of the Heat Transfer Fluid is one of the parameters (along with Fluid Pressure) that regulates the speed and extent of transfer of heat from the load.

Fluid Bypass Circuit

A Fluid Bypass Circuit is a safety device similar to a Pressure Relief Valve, used in Fluid Systems to control or limit pressure in the system which could otherwise exceed the indicated or set level and result in the interruption of a process, damage to equipment, or a catastrophic event (fire, explosion, etc.). In the case of the Bypass Circuit, however, pressure is relieved as the pressurized fluid is allowed to recirculate in the system rather than continue its normal path until the condition is relieved. The Fluid Bypass Circuit is set or pre-designed to open at a predetermined pressure.

Fluid Chillers

The term Fluid Chiller refers to chillers which use Fluid Heat Transfer Mediums such as Ethylene and Propylene Glycol/Water mixture to carry heat away from the process, to be rejected in the refrigeration cycle of the chiller.

Freezing Point

Freezing point is the temperature below which a liquid turns into a solid. It is necessary to choose fluids, and design and program Chiller Systems, such that the fluids in the sytem do not reach the freezing point.