Fuel Testing – What Calorific Value Does a Bomb Calorimeter Measure? A bomb calorimeter determines the higher (gross) calorific value of solid and liquid fuels, since combustion occurs at constant volume with water formed condensed to liquid.

Introduction / Context:
Calorific value indicates energy released during complete combustion. Laboratory calorimeters come in different types, with the bomb calorimeter being the standard for solids and liquids. Knowing whether it yields higher (gross) or lower (net) values is essential for comparing fuels and designing boilers or engines.

Given Data / Assumptions:

• Bomb calorimeter operates at constant volume in a sealed “bomb”.
• Products, including water from hydrogen combustion, are cooled back to initial temperature and water is condensed.
• Complete combustion with sufficient oxygen is ensured.

Concept / Approach:

The higher (gross) calorific value includes the latent heat of condensation of the water produced. Because the bomb calorimeter cools the products to the initial temperature and water is liquid at the end, the measured heat releases include this latent heat, yielding the higher value. The lower (net) value subtracts the latent heat associated with water remaining as vapor, typical of gas-turbine or internal-combustion contexts.

Step-by-Step Solution:

Verification / Alternative check:

Standards (e.g., ASTM) define bomb calorimetry procedures that return gross heating value, with formulas to convert to lower value by subtracting latent heat of water and minor corrections.

Why Other Options Are Wrong:

“Lower” applies to processes where water leaves as vapor. “Net only at constant pressure” and “neither” misunderstand the apparatus. “Apparent without correction” ignores standard correction steps but still yields higher value fundamentally.

Common Pitfalls:

Confusing constant-volume vs. constant-pressure calorimetry; neglecting nitric/sulfuric acid corrections for fuels containing N/S.

Final Answer:

higher