ISRO Scientist or Engineer Mechanical 2020

Instructions

For the following questions answer them individually

Question 21

The typical range of Prandtl number for wateris

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Question 22

Analogy between momentum and heat transfer is known as

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Question 23

Whichof the following statementis true for a Rayleigh flow at M=1?

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Question 24

A fluid passes through a well insulated tube of $$4.7 cm^{2}$$ cross section area and 5 m length.If the pipe friction coefficient is 0.07 and the flow velocity is 3 $$\frac{m}{s}$$, then the flow can be represented using?

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Question 25

A fluid having a density of 1 $$\frac{g}{cc}$$ is in a state with Grashof number $$2 \times 10^{6}$$ and prandtl number 0.7. Assuming acceleration due to gravity as 10 $$\frac{m}{s^{2}}$$, calculate the Rayleigh number?

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Question 26

A cold liquid enters a counter flow heat exchanger at 15 deg at a rate of 8 $$\frac{kg}{s}$$. A hot stream of the same liquid enters the heat exchanger at 7 deg at 2 $$\frac{kg}{s}$$ Assuming the specific heat of the fluid as 4 $$\frac{kJ}{kg}.^\circ$$C, determine the maximum heat transfer rate.

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Question 27

The temperature of a surface with $$0.2 m^{2}$$ area is 17 deg C.Calculate the wavelength corresponding to maximum monochromatic emissive power

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Question 28

For a surface, the direct and diffuse components of the solar radiation are 400 and 300 $$\frac{W}{m^{2}}$$ and the direct radiation makes 60 deg angle with the normal .If the surface temperature is 300 K and effective sky temperature is 200 K , Calculate net rate of radiation of heat transfer .(Assume solar absorptivity and emmissivity as 0.1 each;For calculation take Stefan Boltzmanns constant as G \times 10^{-8} $$\frac{W}{m^{2}}.K^{4}$$)

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Question 29

Which of the following element is added to High Speed Tool Steels as a scavengerto remove slag impurities during melting and also for increasing cutting efficiency of tools.

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Question 30

Region of disorder created by movementof dislocations in superlattice is called:

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