ISRO Scientist or Engineer Refrigeration & Air-Conditioning 2020

Instructions

For the following questions answer them individually

Question 61

A square beam and a circular beam of same material have the same length, same allowable stress and the same bending moment. The ratio of weights of the square beam to that of circular beam is

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Question 62

A circular shaft subjected to torsion undergoes a twist of $$1^\circ$$ in a length of 120 cm. If the maximum shear stress induced is limited to $$1000 kg/cm^2$$ and if the modulus of rigidity $$G = 0.8 \times 10^6 kg/cm^2$$, then the radius of shaft in cm should be

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Question 63

Air flows isentropically through a duct. At a section, the area is $$0.05 m^2$$, velocity $$\nu$$ = 180m/s and temperature T = 470 K. Compute the stagnation temperature $$T_0$$

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Question 64

Which of the following element in the refrigerant is the main contributing factor for ozone depletion of the stratosphere?

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Question 65

If fan running at 720 rpm develops static pressure of 12 mm. If the speed of the fan is doubled the static pressure developed will be

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Question 66

The Apparatus Dew Point (ADP) for the cooling coil of an air conditioning system with high latent load compared to a system with high sensible load will be

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Question 67

Gasoli ne at $$20^\circ C (density = 680 kg/m^3)$$ is pumped through a smooth 12 cm diameter Pipe, 10 km long, at a flow rate of $$75 m^3/hr.$$ The inlet is fed by a pump at an absolute pressure of 24 atm. The exit is at standard atmospheric pressure and is 150 m higher. Estimate frictional head loss $$h_f$$.

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Question 68

Oil at $$20^\circ C (density = 870 kg/m^3$$ and viscosity = 0.104 kg/m-s) flows at $$1.1 m^3/hr$$ through a horizontal pipe with diameter d = 2 cm and length L = 12 m. Find the Reynolds number for the flow.

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Question 69

A person rests her coffee mug on a horizontal tray while she accelerates at $$\frac {10}{\sqrt 3} m/s^2.$$ The mug is 10 cm deep and 6 cm in diameter and contains coffee 7 cm deep at rest. Assuming rigid body acceleration, calculate gauge pressure in the bottom corner point A as shown in figure if density of coffee is $$1010 kg/m^3$$. Assume acceleration due to gravity $$g = 10 m/s^2$$

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Question 70

A process in which the working substance neither receives nor gives out heat to its surroundings during its expansion or contraction is called

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