Ventilation of Restaurant-Type Cooking Equipment (CFPS)

 

Exhaust systems for restaurant equipment require careful design, because grease condenses in the interior of the ducts. Grease accumulations may be ignited by sparks from the cooking appliance or by a small fire on the cooking appliance caused by overheated cooking oil or fat in a deep-fat fryer or on a grill.
If the duct did not have a grease accumulation, cooking appliance fires could often be extinguished before causing appreciable damage.

Fire risk is especially high in frying because cooking oils and fats are heated nearly to their flashpoints

Ducts. The following should be considered when designing a duct system for commercial cooking equipment:

1. The system should be designed to minimize grease accumulations, with a minimum air velocity of 1500 ft/min (458 m/min) through any duct.
2. Ducts should be arranged with ample clearance from combustible materials to minimize the danger of ignition, incase of fire in the duct.
   
3. Ducts of substantial construction (not lighter than No. 16
   Manufacturers Standard Gauge steel or No. 18 Manufacturers Standard Gauge stainless steel) should be used with all seams and joints having a liquid-tight, continuous weld.
   
4. Systems should be separated to ensure there is no connection with any other ventilating or exhaust system.
   
5. Ducts should be led directly outside the building, without dips or traps, unless automatic grease removers are employed at the dips and traps.
   
6. Openings should be provided for inspection and cleaning. Dampers should not be installed in any duct system, unless required as part of a grease extractor or extinguishing system.
   

Convective Heat Flow in Fires (Sprinkler operation )

Convective Heat Flow in Fires

Heat is released from a fire in several forms: radiation, conduction, and convection. It has been determined that convective heat transfer is most important in activating sprinklers.

Convective heat transfer involves heat transfer through a circulating medium, which, in the case of fire sprinklers, is the room air .The air heated by the fire rises in a plume entraining other room air as it rises When the plume hits the ceiling, it generally splits to produce a ceiling gas jet The thickness  of this ceiling jet flow is approximately 5 to 12 percent of the height of the ceiling above the fire source, with the maximum temperature and velocity occurring 1 percent of the distance from the ceiling to the fire source. The heat-sensing elements of sprinklers within this ceiling jet are then heated by conduction of the heat from the air.