Calorific value (CV) of a fuel is a characteristic of fuel which is defined as the energy liberated per kg of fuel burnt. Fuels are found in three phase viz. solid, liquid and gaseous. Junker's calorimeter is used to measure the CV of gaseous fuels.
Bomb Calorimeter experiment to measure calorific value of fuel:
- It is used to measure the calorific value (CV) of solid as well as liquid fuel. But to determine the CV of gas, one need to choose Junker's calorimeter.
- A calorimeter contains thick walled cylindrical vessel and it consists of the lid which supports two electrodes which are in contact with fuse and fuel sample of known weight.
- The lid also contains oxygen inlet valve through which high-pressure oxygen gas (at about 25 to 30 atm) is supplied.
- Entire lid with fuel sample is now held in a copper calorimeter containing known weight of water. A mechanical stirrer is provided to stirred well for uniform heating of water.
- A thermometer is also provided to measure the change in temperature of water due to combustion of fuel in Lid.
Procedure of bomb calorimeter experiment
- A known quantity of fuel sample is added in the crucible.
- Start the stirrer and note down the initial temperature of water.
- Start current through the crucible and let fuel sample to burn in presence of oxygen.
- Heat released during combustion of fuel is taken by water and hence temperature of water rises.
- Note final steady state temperature of water.
Higher Calorific Value of fuel = (m1+m2) x (Tc + T1 - T2 ) x Cw / mf
m1 and m2 are the mass of water in the copper calorimeter and water equivalent of bomb calorimeter respectively.
mf is the mass of fuel sample whose calorific value is to be determined.
T1 and T2 are the final and initial temperature of the water sample. Tc is temperature correction for radiation losses.
Cw is specific heat of water
Water equivalent of bomb calorimeter can be found out for particular bomb calorimeter by first by doing an experiment based on known fuel sample whose calorific value is already known. It depends on the manufacturer of the Bomb calorimeter.
Practical applications of Bomb Calorimeter:
Bomb Calorimeter is used for the measurement of the calorific value of fuel oils, gasoline or petrol, coke, coal, combustion waste, foodstuffs and building materials etc.
A bomb calorimeter is also used for energy balance study in ecology and study of Nano-material, ceramics, zeolite. The bomb calorimeter is helpful to study the thermodynamics of common combustible materials.