After years of working in fuel testing, I have found that many people who are new to calorimeters are curious about the name "oxygen bomb" - why is it called "bomb"? Why do we need to fill it with oxygen? How is the increase in water temperature and calorific value converted? Explain this chain clearly, and you won't feel like the instrument is a black box when operating.

Why do we need high-pressure oxygen

The oxygen content in ordinary air is only 21%, and solid fuels such as coal often burn insufficiently under these conditions, releasing low heat and inaccurate measurement values. The oxygen bomb is filled with pure oxygen of 2.8-3.2MPa, which is equivalent to increasing the oxygen concentration to nearly 100% and the pressure to about 30 times atmospheric pressure. In this oxygen rich high-pressure environment, the sample can achieve complete combustion, ensuring that all chemical energy is converted into heat, and the measurement results are close to the theoretical value.

The word 'bullet' describes its pressure resistant structure - the water pressure resistance of oxygen bombs reaches 20MPa, which is about 7 times the working pressure and has sufficient safety margin.

How does heat become a temperature reading

The oxygen bomb is placed in an inner cylinder containing a certain amount of distilled water. The heat released by the combustion of the sample is first transferred to the oxygen bomb body, and then to the distilled water in the inner cylinder, causing the water temperature to rise.

Calorimetry calculation is based on a basic formula: Q=E × Δ T

Q: Total heat released by the sample (joules)

E: Calorimetric system heat capacity (J/K), HZ-384A is approximately 10500 J/K - this value represents the amount of heat required to raise the temperature of the entire system (oxygen bomb+inner cylinder+water+agitator, etc.) by 1 ℃

Δ T: Actual increase in inner cylinder water temperature (℃)

The calorific value per unit mass=Q/sample mass.

Why is it necessary to calibrate E (heat capacity)

E is a comprehensive parameter that includes the heat capacity of water, oxygen bomb, inner cylinder, stirring blade, and various heat losses... These factors vary with the instrument state (water volume, temperature, etc.) and cannot be accurately obtained from theoretical calculations. It is necessary to use a standard substance (benzoic acid) with known heat generation to actually burn and deduce the current E value, which is the meaning of "calibration".

The temperature sensor of HZ-384A has a resolution of 0.0001 ℃, ensuring the accuracy of Δ T measurement, which is the core source of accuracy in the entire measurement chain.