Made Easy Online Test Series(Thermoal)
May 7, 2017 | Author: Jitendra Yadav | Category: N/A
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1/22/2015
MADE EASY ONLINE TEST SERIES
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Q.1 In a new temperature scale °X, the boiling and freezing point of water at one atmosphere are 200°X and 100°X respectively, is corrected with centigrade scale. The reading 0°X on the centrigrade scale (in °C) is a. 100 b.
– 100
c. 250 d. – 150
Attempt
Correct
Correct Ans.
b
Solution
Q.2
a.
1 , 2, 5 and 6
b.
5, 6, 7 and 8
c. 1, 2, 3 and 8 d. 1, 2, 3 and 4
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Attempt
Incorrect
Your Ans.
a
Correct Ans.
b Solution
Q.3
A gas expands from pressure P1 to pressure
. If the expansion
process is isothermal, the volume at the end of expansion is 0.5 m3 . If the expansion process is adiabatic, the volume (in m3 ) at the end of expansion will be closer to [Take γ for gas = 1.4] a.
0.316
b. 0.50 c. 0.10 d. 0.812
Attempt
Correct
Correct Ans.
a
Solution
Q.4 During steady flow compression process of a gas with mass flow rate of 2 kg/s, increase in specific enthalpy is 15 kJ/kg and decrease in K.E. is 2 kJ/kg. The rate of heat rejection to the environment is 5 kW. The power (in kW) needed to drive the compressor is a.
31
b. 39 c. 34 d. 21
Attempt
Correct
Correct Ans.
a
Solution
Q.5 The gear box of a machine is operating under steady state. The input shaft receives 55 kW from a prime mover and transmits 52 kW to the output shaft, the rest being lost due to friction etc. The gear box surface is at an average temp. of 57°C and looses heat to the surroundings at 27°C. The rate of entropy production (W/K) inside the gear box is a.
10
b. 9.1 × 10–3 c.
9.1
d. 10 × 10–3
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Attempt
Incorrect
Your Ans.
a
Correct Ans.
c Solution
Q.6 Match the ListI (Equipment in the refrigeration) with ListII (Purpose) and select the correct answer from the codes given below the lists:
a. a b. b c. c d.
Attempt
d
Correct
Correct Ans.
d
Solution
Q.7 Two insulated tank containing ideal gases at different pressures and temperatures are connected to each other and gases are allowed to mix. The process that occurs can be called ___________ process. a.
Constant internal energy
b. Constant enthalpy c. Free expansion d.
Attempt
Reversible adiabatic
Incorrect
Your Ans.
d
Correct Ans.
a Solution
Q.8 Consider the following statements: P. Two constant entropy lines cannot intersect Q. Oncethrough boilers never have a steam drum R. In a centrifugal compressor the axial component of the fluid velocity produces rotational effect on the rotor S. The suction pipe diameter of a refrigerator plant should be less than http://m6.onlinetestseriesmadeeasy.in/madeeasy/index.php?pageName=timeManagementReport&testid=50&t=cont1&testType=2
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the discharge pipe diameter. T. The clearance volume of reciprocating compressor is given as a percentage of stroke volume. Which of the above statements are correct? a. P, Q, and R b. R, S and T c.
P, Q, and T
d. Q, R and S
Not Attempt
Correct Ans.
c
Solution
Q.9 Air is flowing steadily through a thermally insulated duct. The pressure and temperature of the air measured at two different stations are as follows:
Considering air as an ideal gas, the direction of flow of air in the duct a. from A to B b.
from B to A
c. air will not flow in the duct d. None of the above
Attempt
Correct
Correct Ans.
b
Solution
Q.10 The mathematical conditions at the critical point for a pure substance would be
a.
b.
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c.
d.
Attempt
Incorrect
Your Ans.
c
Correct Ans.
d Solution
Q.11 5 kg of gas is compressed in a device from a volume of 1.9m3 to a volume of 1.4m3 . During this time, the pressure remains constant at 200 kN/m2 , and it is found that internal energy decreases by 12 kJ. How much energy was transferred as heat (in kJ) to the gas in this process. a.
–112
b. 112 c. 88 d. –88
Attempt
Correct
Correct Ans.
a
Solution
Q.12 A 1000 Ω resistor carrying a current of 10 A for 2 sec is kept at a constant temperature of 27°C by a stream of cooling water. Entropy change of the universe is ________ J/K.
Attempt
Correct
Correct Ans.
666.67 (666.0667.2)
Solution
Q.13 The internal energy of a certain system is a function of temperature alone and is given by formula E = 25 + 0.25 t kJ. If this system execute a process for which the workdone by it per degree temperature increase is 0.75 kNm, the heatinteraction per degree temperature increase is _________ kJ.
Attempt
Incorrect
Your Ans.
26
Correct Ans.
1.00 Solution
Q.14
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A steel flask of 0.04 m3 capacity is to be used to store air at 100 bar, 27°C. The flask is to be protected against excessive pressure by a fusible plug which will melt and allow the air to escape if the temperature rises too high. The temperature at which fusible plug must melt in order to limit the pressure of a full flask to a maximum of 150 bar is ______ (°C). [Take air as perfect gas and R = 287 J/kgK]
Attempt
Correct
Correct Ans.
177 (176178)
Solution
Q.15 A system expands from state ‘1’ (P1 , V1 , T1 ) to the state ‘2’ (P2 , V2 , T2 ) in a reversible nonflow process as defined below (a) A constantpressure process followed by a constantvolume process (b) A constantvolume process followed by a constantpressure process Workdone ratio of the above two processes is _________, if
Attempt
Correct
Correct Ans.
2.5 (2.42.6)
Solution
Q.16 Air enters a compressor in steady flow manner at 140 KPa and 17°C and leaves it at 350 KPa and 127°C. During the flow change in enthalpy and kinetic energy are 110.55 kJ/kg and 3.6 kJ/kg respectively. The minimum reversible work input required is ________ kJ/kg. [Given: Environment temperature is 7°C]
Attempt Incorrect 97.29 (96.897.8)
Your Ans.
114.15
Correct Ans. Solution
Q.17 The weight placed on the steam exhaust port of a domestic pressure cooker never allows the pressure to build up above 250 KPa inside the cooker. The latent heat of vaporization of water is 2257 kJ/Kg at 100°C and 101.325 KPa. The temperature (°C) at which water boils in the cooker is a. 514.4 b. 224.6 c. 400.6 http://m6.onlinetestseriesmadeeasy.in/madeeasy/index.php?pageName=timeManagementReport&testid=50&t=cont1&testType=2
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d.
127.6
Not Attempt
Correct Ans.
d
Solution
Q.18 A heat engine receives half of its heat supply at 1000 K and half at 500 K while rejecting heat to a sink at 300 K. What is the maximum thermal efficiency (in %) of the heat engine? a. 50 b. 45 c. 65 d.
55
Attempt
Correct
Correct Ans.
d
Solution
Q.19 A wind mill is being used to generate pollution free power from the kinetic energy of wind. What is the maximum possible power output (in kW) from such a wind mill for a steady air velocity of 36 kmph, if the diameter of its blades is 10 m? [Assume air is at 27°C and 101 kPa, Take R = 287 J/kgK] a. 84.12 b. 52.18 c. 92.48 d.
46.10
Not Attempt
Correct Ans.
d
Solution
Q.20 Air enters an adiabatic nozzle at 20 bar and 50°C with a velocity of 80 m/s and leaves with a velocity of 300 m/s. If the area ratio of the nozzle is 4 : 1, and nozzle efficiency is 80%. The exit pressure (in bar) of the air is [Take Cp = 1.0 kJ/kgK for air] a. 15.2 b. 14.5 c.
18.6
d. 16.2
Not Attempt
Correct Ans.
c
Solution
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Q.21 A piston cylinder device contains 0.05 m3 of gas initially at 180 kPa. At this state, a linear spring that has a spring constant of 150 kN/m is just touching the piston but exerting no force on it. Now heat is transferred to the gas, causing the piston to rise and to compress the spring until the volume inside the cylinder doubles. If the crosssectional area of the piston is 0.25 m2 , then the total workdone (in kJ) by the gas will be a.
12
b. 14 c. 15 d. 18
Not Attempt
Correct Ans.
a
Solution
Q.22 Long cylindrical aluminium rods (ρ = 2700 kg/m3 and Cp = 0.973 kJ/kgK) of 5 cm diameter are heat treated from 20°C to an average temperature of 400°C by drawing them at a velocity of 10 m/min through a long oven. The rate of heat transfer (in kJ/s) to the rods in the oven is a. 19596.22 b.
326.6
c. 53 d. 426.7
Not Attempt
Correct Ans.
b
Solution
Q.23 A 250 m3 rigid tank contains compressed air at 1 MPa and 300 K. If the environment conditions are 100 kPa and 300 K, then the maximum work (in MJ) that can be obtained from this air is a.
350.6
b. 120.76 c. 29 d. 350646.22
Not Attempt
Correct Ans.
a
Solution
Q.24
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A Lenoir cycle comprises the following processes: (i) Isochoric heat addition of 470 kJ/kg. (ii) Adiabatic expansion to its original pressure with loss of 140 kJ/kg in internal energy. (iii) Isobaric compression to its original volume with heat rejection of 400 kJ/kg. What will be the overall heat transfer and workdone during the cycle respectively? a.
140 kJ and 140 kJ/kg
b. 35 kJ and 70 kJ/kg c.
70 kJ and 70 kJ/kg
d. 70 kJ and 35 kJ/kg
Attempt
Incorrect
Your Ans.
a
Correct Ans.
c Solution
Q.25 What will be the temperature rise (in °C) due to water falling over a height of 1000 m? Change in internal energy of water is related to the temperature change by equations,ΔU = 4.2 Δt kJ/kg (Here Δt is in °C). [Assume water comes to rest after falling) a. 4.6 b. 23 c. 0.23 d.
Attempt
2.3
Correct
Correct Ans.
d
Solution
Q.26 Two heat engine cycles (1 – 2 – 3 – 1 and 1′ – 2′ – 3′ – 1′) are shown below on T – S coordinates.
On pressure volume coordinates, the above cycles are best http://m6.onlinetestseriesmadeeasy.in/madeeasy/index.php?pageName=timeManagementReport&testid=50&t=cont1&testType=2
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represented as:
a.
b.
c.
d.
Attempt
Correct
Correct Ans.
d
Solution
Q.27 A reversible heat engine operates with three thermal reservoirs and delivers 50 kW power. The engine absorbs 1000 kJ/s from a reservoir at 600 K. The temperature of the other reservoirs are 400 K and 300 K. The thermal efficiency (in %) of the engine is a. 15.2 b. 8.2 http://m6.onlinetestseriesmadeeasy.in/madeeasy/index.php?pageName=timeManagementReport&testid=50&t=cont1&testType=2
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c. 27.2 d.
2.7
Attempt
Correct
Correct Ans.
d
Solution
Q.28 The ratio of work input needed to isentropically compress the saturated steam from 1 bar to 5 bar and work input needed to isentropically compress the saturated water for the same pressure ratio is _________.
Attempt
Correct
Correct Ans.
800 (799801)
Solution
Q.29 A rigid insulated tank contains 1 kg of air at 2 bar and 27°C. A paddle wheel inside the tank is rotated by an external motor till the temperature rises to 77°C. The exergetic efficiency of the process is ________ %. [Assume surrounding air is at 27°C and Cv for air = 0.72 kJ/kg°C]
Not Attempt
Correct Ans.
7.5 (7.37.7)
Solution
Q.30 Considering steady heat transfer through a 10 m × 15 m brick wall of a house of thickness 50 cm. On a day when the temperature of the outdoors is 7°C and the indoor temperature is maintained at 27°C. the temperature of the inner and outer surfaces of the brick wall are measured to be 25°C and 9°C, respectively, and the rate of heat transfer through the wall is 1500 watt. Rate of total entropy generation associated with this heat transfer process is ________ W/K.
Attempt Incorrect 0.357 (0.340.37)
Your Ans.
75
Correct Ans. Solution
Q.31 A 100 kg block of iron casting at 500 K is thrown into a large lake that is at a temperature of 285 K. The iron block eventually reaches thermal equilibrium with the lake water. Assuming on average specific heat of http://m6.onlinetestseriesmadeeasy.in/madeeasy/index.php?pageName=timeManagementReport&testid=50&t=cont1&testType=2
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0.45 kJ/kgK for the iron, the entropy generated during the process is ______ kJ/K.
Not Attempt
Correct Ans.
8.65 (8.09.2)
Solution
Q.32 Two rigid tanks, each filled with 50 kg of air, have temperature of 900 K and 300 K. A heat engine placed between the two tanks extracts heat from the high temperature tank, produces work, and rejects heat to the low temperature tank. Maximum work obtained from the tank is ________ kJ.
Not Attempt
Correct Ans.
5772.72 (5772.05773.2)
Solution
Q.33 A 1200 kg vehicle travelling at 90 km/hr impacts a plunger attached to a pistoncylinder arrangement. If all of the energy of the vehicle is absorbed by the 100 kg of liquid contained in the cylinder. The maximum temperature rise of the liquid is ________ °C. The specific heat of the liquid is 4.0 kJ/kg°C.
Attempt Incorrect 1.87 (1.801.94)
Your Ans.
.9375
Correct Ans. Solution
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