Kitchen-Hood Designing

                                                Kitchen-Hood Designing

·       Ventilation is required in both the kitchen and the adjoining areas because :

a.       considerable convective and radiant heat is given off by the cooking   equipment

b.      air becomes laden with odours, grease, fumes and products of     combustion

c.       during meal preparation and washing up, humidity is increased over  a wide area

d.      air replacement and consistency of temperature are required in   adjoining areas

e.      air is required to dilute and replace products of combustion from gas fired appliances

f.        supply air is required to ensure complete combustion of the fuel

l  Kitchens will have good indoor climate and comfortable working temperature with the following factors taken into account :

1.       Impurities and heat are immediately removed with efficient exhaust  hoods.

        

2.       Fresh air is brought in to the working place in such away that it first refreshes staff and then   replaces convection flows

                  

3.       In cases where workers are subjected to large heat radiation ( stoves, broiling units, grills etc. ) supply air is brought directly to the  working place ( local cooling ).

4.       The permitted velocity of supply air varies in different parts of the kitchen areas    :

                                                 

0.30 to 0.50 m/sec near kitchen equipment and

0.10 to 0.20 m/sec in colder areas ( temperature of supply air 17°C )

5.       In addition to exhaust hoods, general exhaust terminals are also   required. General exhaust should be at least 10% of the airflow of the hoods.

·       DESIGN CRITERIA

ü  An internal ambient temperature of 28°C maximum

ü  A maximum humidity level of 70%

ü  Internal noise level should be between

                                               NR40 to 50/NC40 to 50 (Kitchens)

                                               NR35 to 45/NC35 to 45 (Restaurants, bars and cafeterias)

ü  Dedicated supply make-up air system which should supply approximately 85% of the extract flow rate

ü  Humidity is hard to control. The HVAC system should be designed to provide a good ventilation rate to maximise comfort.

ü  Dishwashing machines should be provided with dedicated extract ventilation to control vapour being discharged into the kitchen environment and to avoid potential health hazards caused by cluster flies that thrive in steamy conditions.

ü  The release of carbon monoxide is to be considered when designing the system.

·       TYPES OF HOODS:

a.       WALL TYPE HOOD

b.      ISLAND TYPE HOOD

«  Exhaust/makeup air 1500-2200 /fpm duct velocity

«  Duct to be terminated 40” above the roof.

«  Cleanouts to be provided at the Base of Riser and every 20feet.

«  Duct sheet metal gauge (a) 16ga. Galvanized Steel (b) 18ga. 304 S.S

«  Hood construction 18ga.minimum.

«  Black steel Duct is used for all kitchen ducts (Hoods)

«   S.Steel Duct is used for laundry Exhaust.

«  Stainless Steel

                430 à cheap & catches Rust Easily

                      304 à This type is used for hood.

                     316,317Là Special & Pure Stainless Steel for operation theater in Hospitals.

·       FORMULAS FOR KITCHEN HOOD CALCULATION:                                           

• P = 2L+W for Wall Type Hood  

                                                     

• P = 2L+2W for island type Hood

•          CFM=200xP à Heavy cooking

•          CFM=150xPà Medium cooking

•          CFM=100xPà Light cooking

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