Question

A diesel engine is used to run an electric generator to produce electric power that is used for an electric kettle. The overall efficiency of the system is 45 %. The power supplied to the diesel engine is double the power consumed by the kettle. Determine the efficiency of the kettle as well as the one for the diesel engine, if 18 % of the power received by the generator is lost and the power supplied to the kettle is 480 W.​

Answer 1

Resposta:

Em ≅ 0,61 and Ek = 0,90.

Explicação:

Be the following power transmission chain:

→  M  →  G  →  K  →

1       2       3      4

Em = P₂ / P₁   (motor efficiency = power 2  / power 1)

Eg = P₃ / P₂   (generator efficiency = power 3  / power 2)

Ek = P₄ / P₃   (kettle efficiency = power 4  / power 3)

EG = P₄ / P₁   (global efficiency = power 4  / power 1)

Eg = 0,82 = 480/P₂  ⇒  P₂ = 480 / 0,82  ⇒ P₂ = 585,4 W

Em = P₂ / P₁  = P₂ / 2. P₃ = 585,4 / (2 . 480)  ⇒  Em ≅ 0,61.

Ek = P₄ / P₃  = P₄ / 480  ⇒  Ek = P₄ / 480    (*)

EG = P₄ / P₁ = 0,45  ⇒  0,45 = P₄ /960  ⇒  P₄ = 432 W

Put this value into (*), so:

Ek = P₄ / 480 = 432 / 480  ⇒  Ek = 0,90.