Question

An ideal gas turbine operates using air coming at 355C and 350 kPa at a flow rate of 2.0 kg/s. Find the rate work output

Answer 1

Answer:

The rate of work output = -396.17 kJ/s

Explanation:

Here we have the given parameters

Initial temperature, T₁ = 355°C = 628.15 K

Initial pressure, P₁ = 350 kPa

h₁ = 763.088 kJ/kg

s₁ = 4.287 kJ/(kg·K)

Assuming an isentropic system, from tables, we look for the saturation temperature of saturated air at 4.287 kJ/(kg·K) which is approximately

h₂ = 79.572 kJ/kg

The saturation temperature at the given

T₂ = 79°C

The rate of work output $\dot W$ = $\dot m$×$c_p$×(T₂ - T₁)

Where;

$c_p$ = The specific heat of air at constant pressure = 0.7177 kJ/(kg·K)

$\dot m$ =  The mass flow rate = 2.0 kg/s

Substituting the values, we have;

$\dot W$ = 2.0 × 0.7177 × (79 - 355) = -396.17 kJ/s

$\dot W$ = -396.17 kJ/s