Fuel is any substance capable of chemical combustion with oxygen producing heat and light.
Calorific Value: number of heat units produced by complete combustion of unit quantity of fuel.
COMPARATIVE STUDY OF DIFFERENT FUELS:
WOOD: Good domestic fuel. In industry may be used for Boiler furnace. Contain large amount of moisture, has low thermal value. Calorific value around 4,700 Kcal/kg.
Coal: most extensively used solid fuel, used for both industrial and domestic purposes. Average Calorific value is 7,750Kcal/kg.
Coke: Mainly used for domestic purpose. Has higher calorific value.
LIQUID FUELS: are petrol, kerosene, diesel oil etc.
Points in their favour are:
1. Combustion control easily.
2. Require less storage space.
3. Relative cleanliness.
Used to great extent for I.C. Engineers but to lesser extent for steam raising purpose.
GASEOUS FUELS: may be natural or manufactured.
- can be easily transported
- combustion control effective
- smoke and ash eliminated
- Coal gas – 5,000 Kcal/m3
- Cake Oven – 4,000 Kcal/m3
- Producer Gas – 1,400 Kcal/m3
- L.P.G. – 722 Kcal/m3
L.P.G.: liquid petroleum Gas contains methane, propane, butane etc. gases as constituents. On applying pressure to this mixture of natural gas, a liquid mixture of gas obtained and this liquid is known as L.P.G. Calorific value of this is higher than that of natural gas obtained from oil walls. Therefore, it is a better gaseous fuel.
Calculation of fuel amount and its cost:
In hotels, various fuels may be required. Amount of solid fuels are measured by their weight and Liquid fuels, gaseous fuels and electric energy through meter.
By knowing amount of fuels used during a period, say a month and then by knowing the unit cost of fuels the fuel cost for a month may be found and thus average expenditure on fuels in hotel can be calculated.
Let us take simple example regarding cost of fuel in the catering section of a hotel.
Say in a hotel 120-gas cylinders used average per year in catering section. Cost per cylinder is Rs. 200/-.
To determine average cost of gas fuel per month for said catering section-
Cost of gas fuel for one year = 120 x200 = Rs. 24,000
Per month 24000/12 = Rs. 2000/-
Fuel cost economy:
To keep the cost at economic level in catering industry the kitchen energy saving will play very important role. Few tips given below in this regard.
- For food disposer it is better to use cold water instead of hot water. That saves fuel required for hot water. Greased solidify in cold water, can be ground and washed easily.
- Kitchen sink faucet may be fitted with aerator to reduce hot water flow and save fuel for hot water.
- Gas burner needs burn with blue flame. Has to be cleaned time to time.
- Water to be boiled in kettle or covered pans in place of open ones.
- Matching the size of pan to heating element will reduce heat lost to surrounding air.
- In case of oven-cooked meals, it is better to cook as many dishes as can be managed at a time.
- In case of cooking food with electricity, the burners are to be turned off several minutes before necessary cooking time as heating element will stay hot long enough of finish up cooking and that will save electricity.
- Not to open oven doors often to check food inside.
- To use small pans or ovens for small meals.
- Use of pressure cooker and microwave oven can save fuel.
Heat terms and units, method of transfer:
Heat: is a form of energy. Can be converted to other forms of energy i.e. steam, mechanical etc.
Temperature: indicates “hotness”. Is a measure of intensity of heat.
Heat units: B.T.U. (British thermal unit)
C.H.U. (centesimal heat unit)
Cal (Calorie) etc.
1 Kcal = 2.21 CHU = 3.97 BTU.
1BTU = 0.556CHU = 0.252 Kcal
Heat transfer: can be transferred by Convection, Conduction and Radiation.
Principles of Bunsen burner:
It was Robert Bunsen, a German chemist who introduced the burner. It works on the principle on which gas is now used in stoves and lights. By arranging more supply of air to the gas fuel perfect combustion resulted inside the burner. The non-luminous flame of burner is the outside edge of the outer cone.
High and low, pressure burners: Burners may be of high and low pressure gas supply type. Maximum pressure is 14 inches water column pressure. Heat output depends on pressure.
Low pressure: 4-inch water column. Equivalent to 18,000 BTU/ hr.
High pressure: 10 inch water column. Equivalent to 16,000 BTU/hr.
Therefore, low-pressure burners out put more than high-pressure ones.
Precautions to be taken while handling gas:
Obviously one has to be careful in handling gas fuel. The valves fitted in pipes and tank must be operated in rational manner. When fuel not in use these valves must be kept closed. Leakage of gas in any manner is dangerous. Flame and fire to be kept at safe distance. Abnormal odour to be verified as soon as possible. Pressure regulator function to be observed, tested, and replaced when necessary.
Fuel tanks, location, manifold types:
Oil fuel tanks may be inside or outside the building. Outside tanks are located underground.
Normally following procedure of installation to be maintained for fuel oil tanks-
- Tanks installed as close as possible to the inside wall, either at front of building or at the side adjacent to drive way for allowing easy access for filling of fuel.
- Tank to be located to provide for shortest possible pipe connection, from tank to burner, but at the same time it must not be less than minimum distance required from burners or source of any other fire or flame.
- Tank to be provided for shortest fill connection as far as practicable.
Manifold: firing end of burner consists of gas manifold assembly (for gas burners) that includes the mounting flange for the whole burner. The assembly can be rotated 120O to provide for right or left hand entrance.
It is to be noted that if gas tank installed outside then these to be underground installations talking all safety measures against fire and undesirable explosion danger. Water spray arrangements should be provided to prevent excessive heat of summer, which may cause explosion.