Question

A reversible engine is supplied with heat from two constant temperature sources at 900K and 600K and rejects heat to a constant temperature sink at 300 K. The engine develops work equivalent to 90KJ/s rejects heat at the rate of 56KJ/s. 

Estimate: 

1. Heat supplied by each source and 2. Thermal efficiency of the engine .

Answer 1

Given,

T₁ = 900K, T₂ = 600K, T₃ = 300K

W(engine) = 90kJ/s

Q(rejects) = 56kJ/s

As we know,

Solving equation (i) and (ii), we get

Q₁ = 102kJ/s

and, Q₂ = 44kJ/s

The thermal efficiency of the engine is

Efficiency of engine = Total Work Done / Total heat absorbed = 90 / 146

Efficiency of engine = 0.6164

∴ The efficiency of the engine is 61.64%