Industrial Coils: Common Terms
Fin length – length of finned area measured in the same direction as the tubes
Fin height – height of finned area measured in the same direction as the header (90o to tubes, or “tubes high” direction)
Case height – height of the coil measured from outer case flange to outer case flange, in the same direction as the header
Case length – length of the coil measured from outer case flange to outer case flange, in the same direction as the tubes
Case depth – length of the coil case measured in the direction of airflow
Airflow – Flow rate of process air that is passing over fins of coil, expressed either volumetrically (see ACFM) or in terms of mass flow (SCFM (see below), lb/hr, kg/hr, etc)
SCFM – standard cubic feet per minute. Although it is expressed in volumetric terms, this is actually a mass flow rate of standard air which has a density of 0.075 pounds per cubic foot (sea level and 70oF)
ACFM – actual cubic feet per minute. Volumetric flow rate of air. To calculate the mass flow rate, you must know the air density, which depends on temperature, humidity content, elevation, among other factors.
Face velocity – volumetric flow rate of air divided by coil face area (fin height x fin length). Typically reported in ft/min.
Fluid flow – tubeside stream flow rate. Steam is typically reported in lb/hr, or volumetric flow rate at a given pressure. Liquids are typically reported either in mass flow (lb/hr) or volumetric flow rate (gal/min or GPM).
Glycol – refers to either ethylene or propylene glycol, both common components of tubeside stream in fluid coils. Specified as either a % mass or volume of solution in water.
MAWP – maximum allowable working pressure. The highest pressure that a coil’s construction is designed to withstand, always specified with a maximum temperature.
FPI – fins per inch. Most common units of fin spacing, commonly in the range of 2-14 FPI. Fin spacing is sometimes reported in fins per foot.
Standard steam coil – Steam coil designed in which steam is delivered directly to the tubes where it condenses and then drains from the tubes.Visit our Steam Coils page for more information.
Steam distributing coil – Freeze-resistant (not freeze-proof) coil designed with tube-within-a-tube steam delivery. Visit our Steam Coils page for more information.
Corrosion – chemical degradation of the tube or fin material due to the presence of corrosive agents in either the airstream or tube-side stream
Erosion – physical degradation of the interior of the tube walls due to high tube-side stream velocities or a fluid stream contaminated with particulate
Single circuited – used to describe a fluid coil that has a single, full row of tubes joined to each header
Double circuited – used to describe a fluid coil that has two full rows of tubes joined to each header
Partial circuited – used to describe a fluid coil that has less than a full row of tubes joined to each header
Saturated steam – steam that is 100% vapor and exactly at water’s boiling temperature at a given pressure
Superheated steam – steam that is heated above water’s boiling temperature at a given pressure