Q1: The difference between gross & net calorific values of fuel is due to the

ANS:D - heat carried away by steam from the combustion of hydrogen in the fuel.

The difference between gross and net calorific values of fuel is primarily due to the heat carried away by steam from the combustion of hydrogen in the fuel. When a fuel containing hydrogen is burned, the hydrogen reacts with oxygen to form water vapor (steam) as a combustion product. This process releases a significant amount of heat energy, which contributes to the calorific value of the fuel. In the gross calorific value (GCV), this heat energy is included in the measurement, representing the total heat released by the combustion process. However, in practical applications such as power generation, some of this heat energy carried away by the steam may not be fully utilized and may be lost in the form of latent heat in the exhaust gases or in the cooling systems of the equipment. Therefore, the net calorific value (NCV) of the fuel accounts for this loss of heat energy carried away by the steam, providing a more accurate measure of the heat available for useful work. Sensible heat carried away by flue gases, heat lost by radiation, and heat carried away by steam from the moisture content of the fuel may also contribute to differences between gross and net calorific values, but the most significant factor is typically the heat carried away by steam from the combustion of hydrogen in the fuel.