Thermodynamics - GATE practice papers - Mechanical for Q. 375
Q. A cyclic heat engine operates between source temperature of 1000 °C and a sink temperature 50 °C. Calculate least rate of heat rejection when net work output is 2 kW. (Marks: 02)- Published on 19 Oct 15a. 2.6799 kW
b. 0.6799 kW
c. 0.7463 kW
d. none of the above
ANSWER: 0.6799 kW
The rate of heat rejection will be least for reversible engine,
ηrev = ηmax = 1 – (Tsink / Tsource )
= 1 – (323 / 1273)
= 0.7463
ηmax = Wnet / Q1
Q1 = Wnet / ηmax
= 2 / 0.7463
= 2.6799 kW
Therefore the least heat rejection rate, Q2 is
Q2 = Q1 – Wnet
= 2.6799 – 2
= 0.6799 kW