Analyzing the Performance of a Kitchen Exhaust Air Duct with Regards to Recent Standards: A CFD/Thermal Stress Simulation (ST-16-001)

Recent standards have defined a lower minimum air velocity in kitchen exhaust air ducts. While the aim remains in place to maintain an acceptable in duct air velocity and expel exhaust air-borne particles or fluids towards filters/exhaust outlet. Steel ducts are usually specified to a standard steel gauge thickness, capable of handling the extreme load conditions of high temperatures, possible corrosive conditions, and negative pressure levels within exhaust duct. This paper simulates a typical kitchen exhaust air duct performing under extreme temperature conditions and the low air duct velocities. Lower exhaust air velocities should correspond to lower in duct negative pressure values and therefore, possibly a reduction in steel duct wall thickness.
A CFD/thermals tress analysis was carried out under the most extreme load conditions specified under recently issued standards. This analysis has demonstrated that a lower steel duct thickness is more than sufficient than what is specified in recent standards, and therefore, a lower steel thickness gauge can be used. Provided a comprehensive simulation is carried out demonstrating that the reduced exhaust duct sheet thickness is well within the steel duct mechanical material properties as explained in this paper.