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BARC 2021 ME: Heat Transfer Nuclear Quiz 1

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Question 1

Two finned surfaces with long fins are identical, except that the convection heat transfer coefficient for the first finned surface is twice that of the second one. What statement below is accurate for the efficiency and effectiveness of the first finned surface relative to the second one?

Question 2

A solid cylindrical rod having the length L = 0.15m and diameter D = 0.05m. The top and bottom surfaces of the rod are maintained at constant temperatures of 20oC and 95oC, respectively, while the side surface is perfectly insulated. If it is made of granite with k= 1.2 W/m-oC, the rate of heat transfer through the rod is

Question 3

A spherical shaped orange (k= 0.3W/m) 80mm in diameter undergoes ripening process and generates 5000W/m3 of energy. If external temperature of orange is 10℃ and it is surrounded by air having heat transfer coefficient 20W/m2-k then the maximum temperature (℃) in at the centre of orange will be

Question 4

A spherical body of diameter 750mm of initial temperature 25 is immersed in the fluid at temperature 400. Thermo physical properties of the body are k=22W/m-K, c=400 J/kg and ρ=9000kg/m3 (Regular notations used). Determine the time (in seconds) when the temperature will become 390, given the convective heat transfer coefficient between body and fluid is 300W/m2-k.

Question 5

Peclet Number is ________.

Question 6

The effect of forced convection can be neglected if

Question 7

If Prandtl number is 0.064 and friction coefficient is 0.64, Stanton number will be equal to___.

Question 8

For a counter-flow heat exchanger with heat capacity ratio is equal to 1, the number of transfer units is 1.5. The effectiveness of this heat exchanger is

Question 9

In a counter flow heat exchanger the ratio of masses of the hot and cold fluid is 2:1 and their ratio of specific heat is 1:3 respectively. Hot fluid enters at 80°C and leaves the heat exchanger at 50°C. Cold fluid enter at 40°C and exit at some temperature. Find the exit temperature (in °C) of the cold fluid.

Question 10

Match list-I (Surface with orientations) with List-II (Equivalent emissivity) and select the correct answer using the codes given below the lists :
A- Infinite parallel planes
B- Body 1 completely enclosed by body 2 but body 1 is very small
C- Radiation exchange between two small gray bodies.
D- Two concentric cylinders with large lengths.
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