Thursday, September 19, 2013

KETCHEN DESIGN GUIDE



        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 pressurisation 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 odours 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 considerations should be given to washing-up, food preparation and serving areas.


 

Initial Design Considerations

The modes of heat gain in a space may include solar radiation and heat transfer through the construction together with heat generated by occupants, lights and appliances and miscellaneous heat gains as air infiltration should also be considered. Sensible heat (or dry heat) is directly added to the conditioned space by conduction, convection and radiation. Latent heat gain occurs when moisture is added to the space (e.g., from vapour emitted by the cooking process, equipment and occupants). Space heat gain by radiation is not immediate. Radiant energy must first be absorbed by the surfaces that enclose the space (walls, floor, and ceiling) and by the objects in the space (furniture, people, etc.). As soon as these surfaces and objects become warmer than the space air, some of the heat is transferred to the air

in the space by convection (see picture 2). To calculate a space cooling load, detailed building design information and weather data at selected design conditions are required. Generally, the following information is required:

• building characteristics

• configuration (e.g, building location)

• outdoor design conditions

• indoor design conditions

• operating schedules

• date and time of day

Heat Gain and Emissions Inside

the Kitchen

Cooking can be described as a process that adds heat to food. As heat is applied to the food, effluent (1) is released into the surrounding environment. This effluent release includes water vapour, organic material released from the food itself, and heat that was not absorbed by the food being cooked. Often, when pre-cooked food is reheated, a reduced amount of effluent is released, but water vapour is still emitted into the to the surrounding space. The hot cooking surface (or fluid, such as oil) and products create thermal air currents (called a thermal plume) that are received or captured by the hood and then exhausted. If this thermal plume is not totally

captured and contained by the hood, they become a heat load to the space. There are numerous secondary sources of heat in the kitchen (such as lighting, people, and hot meals) that contribute to the cooling load as presented in table 1.  

Load
W
Lighting
21 - 54/ m2
People
130/person
Hot meal
15/meal
Cooking eq.
Varies
Refrigeration
Varies

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Reference to HVAC SYSTEM 
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