Gas Turbine Recuperator and Capacity Ratio

A gas turbine recuperator is a heat exchanger used in gas turbine systems to recover the waste heat from the exhaust gases and transfer it to the incoming compressed air. This process helps to improve the overall efficiency of the gas turbine system.

Capacity Ratio

The capacity ratio in a gas turbine recuperator is defined as the ratio of the mass flow rate of the hot exhaust gases to the mass flow rate of the cold compressed air. It represents the amount of heat that can be transferred from the exhaust gases to the compressed air.

Explanation of the Correct Answer

The correct answer to the given question is option 'B', which states that the capacity ratio is 1. Let's understand why this is the correct answer.

- In a gas turbine system, the hot exhaust gases leaving the turbine section are at a high temperature and contain a significant amount of waste heat. On the other hand, the compressed air entering the combustion chamber is at a lower temperature.

- The gas turbine recuperator aims to transfer the waste heat from the exhaust gases to the compressed air, thereby preheating the incoming air before it enters the combustion chamber.

- In order to achieve this heat transfer, the capacity ratio should ideally be 1. This means that the mass flow rate of the exhaust gases should be equal to the mass flow rate of the compressed air.

- If the capacity ratio is less than 1, it indicates that there is insufficient heat transfer taking place, and the exhaust gases are not able to transfer enough heat to preheat the compressed air effectively.

- On the other hand, if the capacity ratio is greater than 1, it indicates that there is excessive heat transfer taking place, and the exhaust gases are transferring more heat than required to preheat the compressed air.

- Therefore, a capacity ratio of 1 ensures that the heat transfer in the gas turbine recuperator is optimized, allowing for efficient preheating of the compressed air without any wastage or deficiency of heat transfer.

Conclusion

In a gas turbine recuperator, the capacity ratio should ideally be 1 for efficient heat transfer from the exhaust gases to the compressed air. This ensures that the preheating of the compressed air is optimized without any wastage or deficiency of heat transfer.