What is a calorimeter?
A calorimeter is an object used for calorimetry or the process of measuring the heat of chemical reactions or physical changes, as well as heat capacity. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters, and accelerated rate calorimeters are among the most common types. A simple calorimeter consists of just a thermometer attached to a water-filled metal container suspended above a combustion chamber. It is one of the measuring devices used in the study of thermodynamics, chemistry and biochemistry.
The different types of calorimeters are presented below:
- Adiabatic Calorimeters
- Reaction calorimeters
- Bomb calorimeters (constant volume calorimeters)
- Constant Pressure Calorimeters
- Differential scanning calorimeters
Definition of Bomb Calorimeters:
The calorific value of solid and liquid fuels is determined in the laboratory by the 'bomb calorimeter'. Its shape resembles that of a bomb. The figure shows the schematic sketch of the bomb calorimeter.
Construction of Bomb Calorimeters:
The calorimeter is made of austenitic steel which offers considerable resistance to corrosion and allows it to withstand high pressures. The calorimeter uses a strong cylindrical bomb in which combustion occurs. The pump has two values at the top. One supplies oxygen to the pump and the other releases exhaust gases. A crucible in which a heavy quantity of fuel sample is burned is arranged between the two electrodes as shown in fig. The calorimeter is equipped with a water jacket that surrounds the bomb. To reduce losses due to radiation, the calorimeter is also equipped with a water and air jacket. A stirrer to maintain uniform water temperature and a thermometer accurate to 0.001 degrees C are placed on the lid of the calorimeter.
Calorimeter Diagram
Bomb calorimeter diagramWorking of bomb calorimeters:
The calorimeter is made of austenitic steel which offers considerable resistance to corrosion and allows it to withstand high pressures. The calorimeter uses a strong cylindrical bomb in which combustion occurs. The pump has two values at the top. One supplies oxygen to the pump and the other releases exhaust gases. A crucible in which a heavy quantity of fuel sample is burned is arranged between the two electrodes as shown in fig. The calorimeter is equipped with a water jacket that surrounds the bomb. To reduce losses due to radiation, the calorimeter is also equipped with a water and air jacket. A stirrer to maintain uniform water temperature and a thermometer accurate to 0.001 degrees C are placed on the lid of the calorimeter. The heat released by the fuel during combustion is absorbed by the surrounding water and the calorimeter. From the above data, the calorific value of the fuel can be found.
Bomb calorimeter formula:
Dulong's formula used to calculate the theoretical calorific value of the fuel if the final analysis is available and the calorific value of elementary fuels is known.
Theoretical calorific value of the fuel = 33800 C + 144500 (H2 – (O2/8)) +9300 kJ/kg
Where C, H2 O2 and S represent the mass of carbon, hydrogen, oxygen and sulfur in kJ/Kg
