Previous Years Gate MCQ’s on Power Engineering 2007-2010

Solved GATE Questions on Power Engineering

Question 1. Which combination of the statement is correct?

The incorporation of reheater in a steam power plant:

P : Always increases the thermal efficiency of the of the plant.

Q : Always increases the dry fraction of steam at condenser inlet.

R : Always increases the mean temperature of heat addition.

S : Always increases the specific work output

(A) P and S

(B) Q and S

(D) P,Q,R and S

GATE-ME-2007

Hint 1. (Ans B)

Reheater always increases the dryness fraction of steam at condenser inlet. Always increase the specific work output.

Question 2. A thermal power plant operates on a regenerative cycle with a single open feed water heater, as shown in the figure. For the state points shown, the specific enthalpies are : and . Thte bleed to the feed water heater is 20% of the boiler steam generation rate. The specific enthalpy at state 3 is

(A) 720 KJ/Kg

(B) 2280 KJ/Kg

(D) 3000 KJ/Kg

GATE-ME-2008

Hint 2. (Ans A)

Common data for Questions 3 and 4

The inlet and outlet conditions of steam for an adiabatic steam turbine are as indicated in thte notations are as usually followed

Question 3. If the mass flow rate of steam through the turbine is 20 kg/s, the power output of the turbine (in MW) is

(A) 12.157

(B) 12.941

(D) 168.785

GATE-ME-2009

Hint 3. (Ans A)

For adiabetic process, Q=0

Alternatively

Applying S.F.E.E

Here

Question 4. Assume the above turbine to be part of a simple Rankine cycle. The density of water at the inlet to the pump is 1000 .ignoring kinetic and potential energy effects, the specific work (in KJ/Kg) supplied to the pump is

(A) 0.293

(B) 0.351

(D) 3.510

GATE-ME-2009

Hint 4. (Ans C)

Pump work

Reversible adiabatic

dq=dh-Vdp

dh=Vdp

Alternatively

Common Data Questions : 5 and 6

In a steam power plant operating on the Rankine cycle, steam enters the turbine at 4 Mpa, 350and exits at a pressure of 15 kPa Then it enters the condenser and exists as saturated water. Next, a pump feeds back to the water to the boiler. The adiabatic efficiency of the turbine is 90%. The thermodynamic states of water and steam arte given in table .

State
Steam : 4 Mpa, 350	3092.5		6.5821		0.06645
Water : 15 kPa
	225.94	2599.1	0.7549	8.0085	0.001014	10.02

‘h’ is specific enthalpy, ‘s’ is specific entropy and ‘v’ the specific volume; subscripts ‘f’ and ‘g’ denote saturated liquid state and saturated vapour state.