Question

what is heat engine derive an expression for its efficiency

Answer 1

i think its carnot heat.carnot heat engine is an engine that operates on the reveraible carnot cycle.this model was launched in 1824by leonard sadi carnot. i think it will help uh

Answer 2

   Heat engine system is a Carnot engine.  It absorbs heat energy (Q1) from a heat source is at a temperature T1. The system performs a useful work W on the surroundings.  Then it rejects heat Q2 to the heat sink at a temperature T2.

According to the first law of thermodynamics :  ΔQ = ΔU + W
Here, it transforms to   Q1 = Q2 + W,  as ΔU = 0

The efficiency is defined as  useful work performed / heat absorbed
    = W/Q1
    = (Q1 - Q2)/Q1
    = 1 - Q2/Q1
    = 1 - T2/T1          (this can be proved by using Entropy principles)