GATE XE topic:engineering-sciences PYQs & Answers — Page 82

Questions 811–820 of 1772. Imported answers require independent review unless marked reviewed.

An air standard Diesel cycle consists of four processes: 1-2 (isentropic compression), 2-3 (constant pressure heat addition), 3-4 (isentropic expansion) and 4-1 (constant volume heat rejection).

is the temperature (in K) attained at the end of isentropic expansion (3-4) before constant volume heat rejection. The constant volume heat rejection process (4-1) is replaced by a constant pressure heat rejection process (4a-1) such that

is the temperature (in K) reached at the end of isentropic expansion (3-4a), and the state point 1 remains the same. Then

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Gas in a cylinder-piston device expands from state 1

to state 2

. The expansion process is polytropic, i.e.,

. Assuming the ideal gas behaviour, the expression for the work done,

by the system is given by

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The temperature of the working fluid in a real heat engine cycle changes during heat addition and heat rejection processes. The maximum and minimum temperatures of the cycle are

and

, respectively. If

is the thermal efficiency of a Carnot engine operating between these temperature limits, then the thermal efficiency,

of the real heat engine satisfies the relation

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A 1.2 m

rigid vessel contains 8 kg of saturated liquid-vapor mixture at 150 kPa. The specific enthalpy of this mixture is ______ kJ/kg (round off to 2 decimal places).

At 150 kPa:

/kg,

kJ/kg,

kJ/kg

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Air in a closed system undergoes a thermodynamic process from an initial temperature of 300 K to the final temperature of 400 K. The specific heat of air at constant volume,

varies linearly with the temperature,

(in K) as

Change in the specific internal energy of the air in the system is ______ kJ/kg (round off to 2 decimal places).

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A vertical cylinder-piston device contains a fixed mass of gas in equilibrium. The cross-sectional area of the piston is 0.05 m

. For 150 kPa pressure of the gas in the cylinder, the mass of the piston is ______ kg (round off to 2 decimal places).

Assume that the atmospheric pressure is 100 kPa and the acceleration due to gravity is 9.81 m/s

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A steam power plant operates on Rankine cycle. At certain operating condition of the plant, there is a reduction of 20% net work output (kJ/kg) as compared to 100% capacity. This reduction will cause the specific steam consumption (kg/kJ) to increase by ______ % (in integer).

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A Carnot heat pump extracts heat from the environment at 250 K, and supplies 6 kW of heat to a room which is maintained at a constant temperature

. The heat pump requires a power input of 1 kW for its operation. Then, the temperature of the room

is ______ K (round off to nearest integer).

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One of the Maxwell equations is expressed as

, where

is the entropy per unit mass,

is the mass specific volume,

is the pressure, and

is the temperature. In this expression,

is a continuous function of

and

. The derivatives of

are also continuous. Let

be specific heat capacity at constant volume for a gas. Then,

can be written as

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The general relation among the properties

and

at any state point can be expressed as

. If

and

are continuous functions and

is the Joule-Thomson coefficient, then

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GATE XE topic:engineering-sciences PYQs

Question 89

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Question 91

Question 92

Question 93

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Question 95

Question 96

Question 97

Question 98