Which of the following best defines net heat rate in a propulsion plant?

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Multiple Choice

Which of the following best defines net heat rate in a propulsion plant?

Net heat rate is a measure of how much fuel energy is needed to produce a unit of shaft power in a propulsion plant. It tells you the fuel cost per unit of power delivered to the propeller, so a lower net heat rate means the plant is more fuel-efficient. It’s usually expressed as energy input per unit of shaft power (for example, MJ per kW-hr or BTU per HP-hr). This concept sits opposite to the idea of efficiency: the smaller the heat rate, the higher the efficiency. The other ideas describe different things: the ratio of shaft power to fuel energy input is essentially a measure of efficiency, not heat rate itself; the amount of exhaust energy recovered per cycle relates to energy recovery, not the fuel-to-power conversion; and fuel energy per unit of boiler evaporation concerns boiler performance, not the shaft power generation.

Net heat rate is a measure of how much fuel energy is needed to produce a unit of shaft power in a propulsion plant. It tells you the fuel cost per unit of power delivered to the propeller, so a lower net heat rate means the plant is more fuel-efficient. It’s usually expressed as energy input per unit of shaft power (for example, MJ per kW-hr or BTU per HP-hr). This concept sits opposite to the idea of efficiency: the smaller the heat rate, the higher the efficiency.

The other ideas describe different things: the ratio of shaft power to fuel energy input is essentially a measure of efficiency, not heat rate itself; the amount of exhaust energy recovered per cycle relates to energy recovery, not the fuel-to-power conversion; and fuel energy per unit of boiler evaporation concerns boiler performance, not the shaft power generation.

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