GATE ME Thermal Science : National Champion Test for ESE & GATE ME Exams

Question 1

Which one of the following is a CFC refrigerant?

Question 2

Which type of heat exchanger an automobile radiator is?

Question 3

Which of the following statements are TRUE with respect to heat and work?
(i) They are boundary phenomena
(ii) They are exact differentials
(iii) They are path functions

Question 4

The INCORRECT statement about the characteristic of critical point of a pure substance is that

Question 5

A Carnot cycle is having an efficiency of 0.75. If the temperature of the high temperature reservoir is 727 ⁰C, what is the temperature of low temperature reservoir?

Question 6

The compression ratio of a gas power plant cycle corresponding to maximum work output for the given temperature limits of T _min and T _max will be

Question 7

The efficiency of superheat Rankine cycle is higher than that of simple Rankine cycle because _______.

Question 8

In a mixture of dry air and water vapour at a total pressure of 750 mm of Hg, the partial pressure of water vapour is 20 mm of Hg. The humidity ratio of the air in grams of water vapour per kg of dry air (g_w/kg_dA. is_____

Question 9

A reversible heat engine receives 2 kJ of heat from a reservoir at 1000 K and a certain amount of heat from a reservoir at 800 K. It rejects 1 kJ of heat to a reservoir at 400 K. The net work output (in kJ) of the cycle is

Question 10

An ideal gas undergoes a reversible process in which the pressure varies linearly with volume. The conditions at the start (subscript 1) and at the end (subscript 2) of the process with usual notation are: p₁ = 100 kPa, V₁ = 0.2 m³ and p₂ = 200 kPa, V2 = 0.1 m³ and the gas constant, R = 0.275 kJ/kg-K. The magnitude of the work required for the process (in kJ) is ________

Question 11

Steam enters a well-insulated turbine and expands is entropically throughout. At an intermediate pressure, 20 percent of the mass is extracted for process heating and the remaining steam expands is entropically to 9 kPa.
Inlet to turbine:

Intermediate stage: h = 2776 kJ/kg
Exit of turbine: P = 9 kPa, h_f = 174 kJ/kg, h_g = 2574 kJ/kg, s_f 0.6 kJ/(kg.K), s_g = 8.1 kJ/(kg.K)
If the flow rate of steam entering the turbine is 100 kg/s, then the work output (in MW) is__________

Question 12

A 2 kW, 40 litre water heater is switched on for 20 minutes. The heat capacity C_P for water is 4.2 kJ/kg K. Assuming all the electrical energy has gone into heating the water, increase of the water temperature in degree centigrade is

Question 13

A gas contained in a cylinder is compressed, the work required for compression being 5000 kJ. During the process, heat interaction of 2000 kJ causes the surroundings to the heated. The change in internal energy of the gas during the process is

Question 14

A reversible heat engine operating between hot and cold reservoirs delivers a work output of 54 kJ while it rejects a heat of 66 kJ. The efficiency of this engine is:

Question 15

For a gas turbine power plant, identify the correct pair of statements.
P. Smaller in size compared to steam power plant for same power output
Q. Starts quickly compared to steam power plant
R. Works on the principle of Rankine cycle
S. Good compatibility with solid fuel

Question 16

The stroke and bore of a four stroke spark ignition engine are 250 mm and 200 mm respectively. The clearance volume is 0.001m³. If the specific heat ratio $Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\GATE ME 18-Mar\GATE-ME-2007_files\image066.png$ the air–standard cycle efficiency of the engine is

Question 17

A Brayton cycle (air standard) has a pressure ratio of 4 and inlet conditions of one standard atmosphere pressure and 27 °C. Find the air flow rate required for 100 kW power output if the maximum temperature in the cycle is 1000 °C. Assume γ =1.4 and C_p = 1.0 kJ/kg –K

Question 18

Moist air at 35 °C and 100% relative humidity is entering a psychometric device and leaving at 25 °C and 100% relative humidity. The name of the device is

Question 19

In the vapour compression cycle shown in the figure, the evaporating and condensing temperatures are 260 K and 310 K, respectively. The compressor takes in liquid-vapour mixture (state 1) and isentropically compresses it to a dry saturated vapour condition (state 2). The specific heat of the liquid refrigerant is 4.8 kJ/kg-K and may be treated as constant. The enthalpy of evaporation for the refrigerant at 310 K is 1054 kJ/kg.

The difference between the enthalpies at state points 1 and 0 (in kJ/kg) is______

Question 20

A building has to be maintained 21^oC at (dry bulb) and 14.5^oC (wet bulb). The dew point temperature under these conditions is 10.17^oC. The outside temperature is –23^oC (dry bulb) and the internal and external surface heat transfer coefficients are 8 W/m² K and 23 W/ m² K respectively. If the building wall has a thermal conductivity of 1.2 W/mK, the minimum thickness (in m) of the wall required to prevent condensation is

Question 21

I n a steam power plant operating on an ideal Rankine cycle, superheated steam enters the turbine at 3 MPa and 350℃. The condenser pressure is 75 kPa. The thermal efficiency of the cycle is ________ percent.
Given data:
For saturated liquid, at P = 75 kPa, h_f = 384.39 kJ/kg, v_f = 0.001037 m3/kg, s_f = 1.213 kJ/kg‐K
At 75 kPa, h_fg = 2278.6 kJ/kg, s_fg = 6.2434 kJ/kg‐K
At P = 3 MPa and T = 350℃[Superheated steam], h = 3115.3kJ/kg, s = 6.7428 kJ/kg‐K

Question 22

In a statement if a system is said to be in thermal equilibrium on experiences no net change in thermal energy, and considering A, B, and C as distinct thermodynamic systems, then which among the following statement is correct:

Question 23

An inventor says that his new concept of an engine, while working between temperature limits of 27 °C and 327 °C rejects 45% of heat absorbed from the source. His engine is then equivalent to which one of the following engines?

Question 24

A moist air sample has dry bulb temperature of 30 ºC and specific humidity of 11.5 g water vapour per kg dry air. Assume molecular weight of air as 28.93. If the saturation vapour pressure of water at 30 ºC is 4.24 kPa and the total pressure is 90 kPa, then the relative humidity (in %) of air sample is ______.

Question 25

A vapor absorption refrigeration system is a heat pump with three thermal reservoirs as shown in the figure. A refrigeration effect of 100W is required at 250 K when the heat source available is at 400 K. Heat rejection occurs at 300 K. the minimum value of heat required (in W) is
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