An Otto cycle with air as the working fluid has a compression ratio of 8.2. Under cold air standard conditions, what is the thermal efficiency of this cycle?

Under cold air standard conditions, the thermal efficiency of this cycle is 56.9 percent.

Explanation:

From Thermodynamics we remember that thermal efficiency of the ideal Otto cycle (), dimensionless, is defined by the following formula:

(Eq. 1)

Where:

- Compression ratio, dimensionless.

- Specific heat ratio, dimensionless.

Please notice that specific heat ratio under cold air standard conditions is .

If we know that and , then thermal efficiency of the ideal Otto cycle is:

Under cold air standard conditions, the thermal efficiency of this cycle is 56.9 percent.