GATE ME format:nat PYQs & Answers — Page 30

Questions 291–300 of 418. Imported answers require independent review unless marked reviewed.

Topic practice 418 questionsPage 30 of 42

An idealized centrifugal pump (blade outer radius of 50 mm) consumes 2 kW power while running at 300 rpm. The entry of the liquid into the pump is axial and exit from the pump is radial with respect to impeller. If the losses are neglected, then the mass flow rate of the liquid through the pump is ______ kg/s (round off to two decimal places).

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A steam power cycle with regeneration as shown below on the T-s diagram employs a single open feedwater heater for efficiency improvement. The fluids mix with each other in an open feedwater heater. The turbine is isentropic and the input (bleed) to the feedwater heater from the turbine is at state 2 as shown in the figure. Process 3-4 occurs in the condenser. The pump work is negligible. The input to the boiler is at state 5. The following information is available from the steam tables:

State	1	2	3	4	5	6
Enthalpy (kJ/kg)	3350	2800	2300	175	700	1000

The mass flow rate of steam bled from the turbine as a percentage of the total mass flow rate at the inlet to the turbine at state 1 is ______.

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An air standard Otto cycle has thermal efficiency of 0.5 and the mean effective pressure of the cycle is 1000 kPa. For air, assume specific heat ratio

and specific gas constant R = 0.287 kJ/kg·K. If the pressure and temperature at the beginning of the compression stroke are 100 kPa and 300 K, respectively, then the specific net work output of the cycle is _____ kJ/kg (round off to two decimal places).

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A gas turbine with air as the working fluid has an isentropic efficiency of 0.70 when operating at a pressure ratio of 3. Now, the pressure ratio of the turbine is increased to 5, while maintaining the same inlet conditions. Assume air as a perfect gas with specific heat ratio

=1.4. If the specific work output remains the same for both the cases, the isentropic efficiency of the turbine at the pressure ratio of 5 is ______ (round off to two decimal places)

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The figure shows a pouring arrangement for casting of a metal block.

Diagram for Mechanical Engineering question 50

Frictional losses are negligible. The acceleration due to gravity is 9.81 m/s². The time (in s, round off to two decimal places) to fill up the mold cavity (of size 40 cm × 30 cm × 15 cm) is _____

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The value of the following definite integral is____ (round off to three decimal places)

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A gas tungsten arc welding operation is performed using a current of 250 A and an arc voltage of 20 V at a welding speed of 5 mm/s. Assuming that the arc efficiency is 70%, the net heat input per unit length of the weld will be _____ kJ/mm (round off to one decimal place).

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In ASA system, the side cutting and end cutting edge angles of a sharp turning tool are 45° and 10°, respectively. The feed during cylindrical turning is 0.1 mm/rev. The center line average surface roughness (in μm, round off to one decimal place) of the generated surface is____

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The thickness of a sheet is reduced by rolling (without any change in width) using 600 mm diameter rolls. Neglect elastic deflection of the rolls and assume that the coefficient of friction at the roll-workpiece interface is 0.05. The sheet enters the rotating rolls unaided. If the initial sheet thickness is 2 mm, the minimum possible final thickness that can be produced by this process in a single pass is _____ mm (round off to two decimal places).

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Taylor’s tool life equation is given by

, where

is in m/min and

is in min. In a turning operation, two tools X and Y are used. For tool X,

= 0.3 and

= 60 and for tool Y,

= 0.6 and

= 90. Both the tools will have the same tool life for the cutting speed (in m/min, round off to one decimal place) of____

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GATE ME format:nat PYQs

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