Bomb Calorimeter – Description, Working | New Topic [2024]

In this note, we are going to learn about Bomb Calorimeter, and about its Working, Procedure, and Calculations. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.

Author: Arun Paul.

What is Bomb Calorimeter?

The bomb calorimeter is used to determine the calorific value of solid and liquid fuels, while the gas calorimeter is used for gaseous fuels.

bomb calorimeter diagram - poly notes hub

Working Principle

A measured quantity of fuel is burned in the calorimeter, and the heat released is used to heat water within the apparatus. The amount of heat absorbed by the water corresponds to the heat released by the fuel. This relationship is used to calculate the calorific value of the fuel.

Description of the Calorimeter

  • The bomb calorimeter consists of a stainless steel bomb, where fuel combustion takes place.
  • The bomb is sealed with an airtight lid equipped with:
    • A valve for oxygen inlet.
    • A valve to apply pressure.
    • A valve to release excess pressure.
  • Two platinum electrodes are embedded in the lid to facilitate ignition. A small ring is attached to one electrode to hold the fuel sample, which is placed in a silica crucible inside the bomb.
  • The bomb is submerged in a copper calorimeter containing a known mass of water. This setup is surrounded by an air jacket and a water jacket to minimize heat loss through radiation.
  • Additional components include an electrically operated stirrer and a Beckmann thermometer to accurately measure temperature changes.

Procedure of Bomb Calorimeter

  • A known mass of the given fuel is placed in a silica crucible inside the bomb.
  • Oxygen is introduced into the bomb under 25–30 atmospheric pressure.
  • The calorimeter water is stirred thoroughly, and the initial temperature is recorded.
  • An electric current is passed through the fuel in the crucible, which ignites it, initiating combustion.
  • The combustion releases heat, raising the water temperature. The final temperature is recorded after thorough stirring.
  • The observed temperature rise corresponds to the heat absorbed by the water and calorimeter, which represents the fuel’s energy content.

Applications of Bomb Calorimeter

Here we have listed some bomb calorimeter uses –
  • To determine the calorific value of both liquid and solid fuels including coal, petroleum, diesel, and gasoline.
  • Food energy content is calculated by estimating the calorific value of food samples, helping in nutritional analysis.
  • To determine the calorific value of biomass, such as wood and agricultural waste, as a potential energy source.
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