Question

A real (non-Carnot) heat engine, operating between heat reservoirs at temperatures of and performs 4.3 kJ of net work and rejects of heat in a single cycle. The thermal efficiency of this heat engine is closest to

Answer 1

Complete Question

A real (non-Carnot) heat engine, operating between heat reservoirs at temperatures of 650 K and 270 K and performs 4.3 kJ of net work and rejects 8.00 kJ of heat in a single cycle. The thermal efficiency of this heat engine is closest to A) 0.35 B) 0.31. C) 0.28. D) 0.38. E) 0.42.

Answer:

The correct option is A

Step-by-step explanation:

From the question we are told that

The first operating temperature is
`T_1 = 650 \ K`

The second operating temperature is
`T_2 = 270 \ K`

The net workdone is
`W = 4.3 \ kJ = 4.3 *10^(3) \ J`( output of the engine )

The amount of heat energy rejected is
`H = 8.00 \ kJ = 8.00 *10^(3 ) \ J`

Generally a heat engine convert heat from a high temperature to mechanical energy and then reject the remaining heat so the absorbed by the engine is

`W + H`

Generally the thermal efficiency is mathematically represented as

`\eta = (out)/(In) * 100`

Here out is the output of the engine

and in is the input of the engine

`\eta = (W)/(W + H) * 100`

=>
`\eta = (4.3)/(4.3 + 8) * 100`

=>
`\eta = 0.35`