Calorific values – relationship between higher and lower heating values Is the following statement correct? “The lower calorific value (LCV) of a fuel may be obtained by adding the latent heat of the steam formed during combustion to the higher calorific value (HCV).”

Introduction / Context:Higher and lower calorific values differ in whether the water formed during combustion is condensed and its latent heat recovered. Many exam questions probe this sign convention.

Given Data / Assumptions:

• HCV assumes products are cooled to condense water and recover latent heat.
• LCV assumes water remains as vapour and latent heat is not recovered.
• Fuels containing hydrogen produce water upon combustion.

Concept / Approach:The relationship is: HCV = LCV + latent heat of water formed (per unit fuel). Equivalently, LCV = HCV − latent heat associated with product water. Therefore, adding latent heat to HCV to “obtain LCV” is incorrect; you subtract that heat to go from HCV to LCV.

Step-by-Step Solution:Define LH_vap = latent heat of vaporisation of water in products.State identity: LCV = HCV − LH_vap (per unit fuel considering water formed).Interpret the prompt: it says “adding” LH_vap to HCV → would give a value larger than HCV, contradicting LCV < HCV.Thus the statement is false.

Verification / Alternative check:Numerical examples: Natural gas HCV ≈ LCV + 10%–11% (due to water condensation). LCV is lower because latent heat is not recovered in typical exhaust conditions.

Why Other Options Are Wrong:

• Any “Yes” option reverses the sign convention.
• “LCV is always greater than HCV” is the opposite of reality; HCV ≥ LCV.

Common Pitfalls:Confusing which value includes condensation. Remember: HCV counts the latent heat; LCV does not.

Final Answer:No