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GATE 2020: Thermodynamics National Champion Quiz (App update required to attempt this test)

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Question 1

1200W of heat is transferred steadily from outside to inside of a room in summer. The outside and inside temperatures of wall are 350C and 250C. The magnitude of rate of entropy generation in the wall is _______W/K.

Question 2

Which of the following is true for a pure substance at critical point _________.

Question 3

For a reaction type steam turbine, the maximum blade efficiency, the speed ratio is given by :

Question 4

When the clearance volume of a reciprocating compressor increases, its volumetric efficiency :

Question 5

Nitrogen gas of 0.05mvolume is contained in a piston cylinder device having initial temperature and pressure of 1bar and 25 ºC. The gas is compressed isothermally and reversibly until the pressure is 5bar. Calculate change in entropy for the process.

Question 6

A cyclic device operates between three thermal reservoirs, as shown in the figure. Heat is transferred to/from the cyclic device. It is assumed that heat transfer between each thermal reservoir and the cyclic device takes place across negligible temperature difference. Interactions between the cyclic device and the respective thermal reservoirs that are shown in the figure are all in the form of heat transfer.

The cyclic device can be

Question 7

A two stage vapour compression plant with a direct contact heat exchanger uses R-12 as refrigerant. The evaporator and condenser temperature are -30 and 40 respectively. The condenser and evaporator pressure are 15.5 bars and 1.2 bars respectively. If the capacity of the plant is 25 tonnes of refrigeration then the COP of the plant is _____(take 1 tonnes of refrigeration=14000 kJ/h)
Given data:

Question 8

A milk chilling unit can remove heat from the milk at the rate of 42 MJ/h. The rate of heat leakage into the milk from the surrounding is 4.2 MJ/h. The specific heat of milk above the freezing point is 4.2 kJ/kg K and below the freezing point is 2.1 kJ/kg K. The freezing point of milk is -2°C and the latent heat is 100 kJ/kg. The time required (in min) for cooling a batch of 100 kg milk from 47°C to -5°C is

Question 9

Propane (C3H8) is burned in an oxygen atmosphere with 10% deficit oxygen with respect to the stoichiometric requirement. Assuming no hydrocarbons in the products, the volume percentage of CO in the products is _________.

Question 10

In a simple Brayton cycle, the pressure ration is 6 and temperatures at the entrance of compressor and turbine are 400 K and 1500 K, respectively. Both compressor and gas turbine have isentropic efficiencies equal to 0.7. For the gas, assume a constant value of Cp (specific heat at constant pressure) equal to 1 kJ/kgK and ratio of specific heats as 1.4. Neglect changes in kinetic and potential energies.  The power required by the compressor (in kJ/kg) of gas flow rate is __________.

Question 11

In an Otto cycle air at 18 °C and 1.02 bar is compressed adiabatically until the pressure is 15 bar. Calculate percentage air standard efficiency for the cycle.

Question 12

In a turbine, air expands from 5 bar and 600ºC to 1bar 250 ºC. During expansion 15kJ/kg is lost to the surrounding at 1bar and 15ºC. Neglecting Kinetic energy and potential energy changes. Determine maximum work per kg of air. (C= 1.005kJ/kgK).
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