Question

What sets the limits on efficiency of a heat engine?

Answer 1

The temperature of the cold reservoir sets the limit on the efficiency of a heat engine.

[Note: η = \(1-\frac{T_C}{T_H}\)  This formula shows that for maximum efficiency, T_C should be as low as possible and T_H should be as high as possible.]

For a Carnot engine, efficiency

η = \(1-\frac{T_C}{T_H}\),  η →1 as T_C → 0