Question

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?

Answer 1

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

Step-by-step explanation:

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

`\eta_(th) = 1-(1)/(r^(\gamma-1))` (Eq. 1)

Where:

`r` - Compression ratio, dimensionless.

`\gamma` - Specific heat ratio, dimensionless.

Please notice that specific heat ratio under cold air standard conditions is
`\gamma = 1.4`.

If we know that
`r = 8.2` and
`\gamma = 1.4`, then thermal efficiency of the ideal Otto cycle is:

`\eta_(th) = 1-(1)/(8.2^(1.4-1))`

`\eta_(th) = 0.569`

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