Reference

Sprinklers and spray nozzles are designed to produce certain spray characteristics, most notable of which is the relationship between fluid flow rate and inlet pressure. In attempting to gain some commonality between various manufacturers, styles and capacities, it became readily accepted by the fire protection community to use the nozzle discharge coefficient (or K-factor) for system design. Unfortunately, many types of real commercial nozzles tend to exhibit unusual flow behavior when closely scrutinized. Though most hydraulic nozzles and nearly all sprinklers follow a normal hydraulic curve, highly engineered sprays, as opposed to standard deflection type sprinklers, often contain complex internal and external geometries used to form the distinctive spray patterns.

In order to properly characterize these nozzles for use in fire protection systems, one needs a K-factor that is constant over the entire flow range. In order to properly account for the inconsistent hydraulic friction of the internal flow geometry, it probably makes more sense to consider the pressure exponent as a variable rather than a constant.

Through repeated laboratory testing over the course of many years, we have found that the lumped pressure exponents serve quite well in providing a consistent discharge coefficient for each type spray nozzle in many cases.
 

Spray Nozzle Types

Pressure Exponent (n)
Sprinklers
0.50
Swirl Type Atomizer
0.50
Cluster Swirl Type Atomizer
0.50
Spiral nozzle
0.50
Full Cone
0.47
Wide Angle Full Cone
0.44

Download the full paper here.

Literature

"Spray Characterization of Typical Fire Suppression Nozzles," Geoff Tanner/Keith Knasiak, 3rd International Water Mist Conference, September, 2003

"Water Mist Simplification Effects on Fire Suppression Modeling: A Challenge to the Industry," Geoff Tanner/Keith Knasiak, ILASS Americas 20th Annual Conference on Liquid Atomization and Spray Systems, May 2007

Data Sheets

Water Mist Fire Protection for Machinery Spaces

Water Curtain Fire Protection for Gas Storage Tanks

Restaurant Range Hood Fire Protection System

Refuse Disposal Area Fire Protection

Gasoline Truck Loading Dock Fire Protection System

Materials by Application

Brass - for use in non-corrosive environments
Phosphor Bronze - for use in salt water marine applications
316 Stainless Steel - for use in corrosive environments

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Pollution Control Using Spray Technology, Bulletin 615

Fire Protection Spray Products and Applications Support Services, Bulletin 618A

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References

Literature

  • Fire Protection Spray Products and Applications Support Services, Bulletin 618A  · View   · Request
  • Full-line catalog including spray nozzles and accessories, technical data and problem-solving ideas, Catalog 70   · View  · Request
  • Full-line catalog including spray nozzles and accessories, technical data and problem-solving ideas,
    Catalog 70-M - Metric   · View  · Request

Resources

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