Commercial Kitchen Ventilation Systems
The commercial kitchen is a unique space where many different HVAC applications take place within a single environment. Exhaust, supply, transfer, refrigeration, building pressurization and air conditioning all must be considered in the design of most commercial kitchens.
It is obvious that the main activity in the commercial kitchen is the cooking process. This activity generates heat and effluent that must be captured and exhausted from the space in order to control odour and thermal comfort. The kitchen supply air, whether mechanical or transfer or a combination of both, should be of an amount that creates a small negative pressure in the kitchen space. This will avoid adours and contaminated air escaping into surrounding areas. Therefore the correct exhaust air flow quantity is fundamental to ensure good system operation, thermal comfort and improved IAQ. Similar consideration should be given to washing-up, food preparation and serving areas.
Kitchen ventilation has at least two purposes: 1) to provide a comfortable environment in the kitchen and 2) to ensure the safety of personnel working in the kitchen and of other building occupants.
HVAC system designers are most frequently involved in commercial kitchen applications, in which cooking effluent contains large amounts of grease or water vapor.
The centerpiece of almost any kitchen ventilation system is an exhaust hood(s), used primarily to remove cooking effluent from kitchens. effluent includes gaseous, liquid, and solid contaminants produced by the cooking process, and may also include products of fuel and even food combustion. These contaminants must be removed for both comfort & safety; effluent can be potentially life-threatening and, under certain conditions, flammable. Finally, it should be noted that the arrangement of food service equipment and its coordination with the hood(s) can greatly affect the energy used by these systems, which in turn affects kitchen operating costs. Quite often, the hood selection and appliance layout is determined by a kitchen facility designer. To minimize energy use and ensure a properly designed kitchen ventilation system, the HVAC engineer should reach out to the kitchen designer and share the practices and ideas presented in this chapter.
Kitchens are some of the most intensive users of energy for given area compare to other commercial and institutional occupancies. In addition to energy used during cooking, the kitchen ventilation system must address the large amount of heat emitted or convected into the kitchen from the cooking equipment, and supply and condition the ventilation air needed as part of the cooking effluent exhaust system. Given these factors, it is imperative that the kitchen ventilation system be designated with careful consideration of both first cost and operating costs. An additional factor to be considered is the cooking effluent, and any treatments that may be required before it is discharged into the atmosphere.
Restaurants & commercial kitchens are the largest consumers of energy per unit of floor area when compared to other commercial or institutional occupancies. Primary drivers of commercial kitchen energy use are the cooking appliances and the HVAC systems. The kitchen exhaust ventilation system is often the largest energy-consuming component in a commercial food service facility. Minimizing the exhaust airflow needed for cooking appliances and reducing radiant load from the appliances are primary considerations in optimizing system design.
Types of Canopy:
• Wall- mounted canopy – used for all types of cooking equipment located against a wall.
• Single – Island Canopy – used for all types of cooking equipment in a single-line island configuration.
• Double-Island Canopy – used for all types of cooking equipment mounted back-to-back in an island configuration.
• Back Shelf/ Proximity – used for counted – height equipment typically located against a wall, but possibly freestanding.
Sizing – The size of the exhaust hood relative to cooking appliances is important in determining hood performance. Usually the hood must extend horiztally beyond the cooking appliances to capture expanding thermal currents rising from appliances.
Overhang – Varies the hood style, distance between hood and cooking surface, and characteristics of cooking equipments.
Exhaust Flow Rates – Exhaust flow rate requirements to capture, contain, and remove effluent vary considerably depending on hood style, overhang, distance from cooking surfaces to hood, presence and size of side panels, cooking equipment, food and cooking processes involved. The hot cooking surfaces and product effluent create thermal air currents that are captured by the hood and then exhausted. The velocity of these currents depends largely on surface temperature.