BOMB CALORIMETER &JUNKERS CALORIMETER

What’s calorific value?

The calorific value of a fuel may be defined as the amount of heat generated by burning one kg of fuel completely.

The unit of C.V incase of Solid and Liquid Fuels is kJ/kg The unit of C.V incase of Gaseous Fuels is kJ/m3

What’s a CALORIMETER?

A calorimeter (from Latin calor, meaning heat) is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity.

In short it is a device used to calculate the Calorific Value of Solid , Liquid & Gaseous Fuels.

Bomb Calorimeter : A bomb calorimeter is a type of constant-volume calorimeter used in

measuring the heat of combustion of a particular reaction. The fuel is kept on a crucible supported by ignition rods and fuse

wires made up of platinum or nichrome. Electrical energy is used to ignite the fuel; as the fuel is burning, it

will heat up the Stainless Steel Container. Thus the heat is transferred to the water outside the container. The

temperature of the water allows for calculating calorie content of the fuel.

Overview :

Basically, a bomb calorimeter consists of a a. Small cup to contain the sample,b. Oxygen, c. A stainless steel bomb, d. Water,e. A stirrer, f. A thermometer,g. The dewar (to prevent heat flow from the calorimeter to the

surroundings) and ignition circuit connected to the bomb.

Calculations: mf = Mass of fuel sample burnt in the bomb in kg

H.C.V = Higher Calorific Value of the fuel sample in kJ/kg

mw =Mass of water filled in calorimeter in kg

me = Water equivalent of apparatus in kg

t1 = Initial temperature of water and apparatus in C

t2 =Final temperature of water and apparatus in C

We know that heat liberated by fuel = mf x H.C.V

Heat Absorbed by water and apparatus = (mw + me) cw (t2 - t1)

Since the heat liberated is equal to the heat absorbed … tc = cooling correction

Junkers calorimeter :

Similar Principle to that of the Bomb calorimeter

Junkers Calorimeter used to determine the calorific value of GASEOUS fuels while the Bomb Calorimeter is used to determine the calorific value of SOLID AND LIQUID fuels.

Working: Gas of particular amount is supplied through the inlet through the

GAS METER Burnt in the combustion chamber The heat is then transferred to the water tubes called the flue tubes Cold water is supplied through the bottom and Hot water leaves at

the top. The difference in temperatures of the water at two ends is used to

find the higher calorific value of the gas. Calculations are similar to that of the Bomb calorimeter.