Effect of Kitchen Air Distribution System Equation 4

By admin on November 21st, 2007

Effect of Kitchen Air Distribution System

Equation 4 assumes that a mixing air distribution
system is being utilised and that the exhaust/return air
temperature is equal to the kitchen air temperature
(assuming fully mixed conditions). Conversely, a
displacement ventilation system can supply low
velocity air directly into the lower part of the kitchen
and allow the air naturally to stratify. This will result in
a higher temperature in the upper part of the kitchen
while maintaining a lower air temperature in the
occupied zone. This allows for improvement of the
kitchen indoor air quality without increasing the capital
costs of the air conditioning system.
Picture 35 demonstrates a CFD simulation of two
kitchens with mixing and displacement ventilation
systems. In both simulations the kitchens have the
same appliances contributing the same heat load to
the space. The supply air flow and temperatures, and
the exhaust air flow through the hoods are the same
in both cases. The air is supplied through the typical
ceiling diffusers in the mixing system. In the case of
the displacement system, air is supplied through
specially designed kitchen diffusers located on the
walls. As one can see, the displacement system
provides temperatures in the kitchen occupied zone
from 22 to 26 C while the mixing system, consuming
the same amount of energy as displacement, results
in 27 32 C temperatures. This 2 C temperature
increase in the kitchen with the mixing air distribution
system will result in approximately 10% reduction in
productivity (see picture 6. page 9).
Halton HELP
TM
program allows kitchen ventilation
systems for both mixing and displacement ventilation
systems to be designed.