Which expression correctly represents the annual fuel cost FC given the steam load, operating hours, price, and steam rate?

• A. FC = (SL x 24 x 350 x P) / SR
• B. FC = (SR x P) / (SL x 24)
• C. FC = SL x P x SR x 24 x 350
• D. FC = (SL x P) / (SR x 24)

Answer: (A)

The expression tests how to turn a steam demand into annual fuel cost by using the steam rate. Start with the steam load per hour (SL). Multiply by the total operating hours per year to get the total steam produced in a year: SL × (24 × 350). To find how much fuel is needed, divide that annual steam by the steam rate (SR), which tells you how much steam you get per unit of fuel. That gives annual fuel consumption in fuel units: (SL × 24 × 350) / SR. Finally, multiply by the price P per unit of fuel to get the annual cost: FC = (SL × 24 × 350 × P) / SR. This neatly accounts for hourly load, annual operating time, fuel efficiency in producing steam, and fuel price.

The other forms would misplace SR or omit the correct annual-time factor, leading to incorrect units or magnitudes.