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Heat Transfer Mock Test 4


Correct Answer: 2 points | Wrong: -1 point
Grades: A* (100% score) | A (80%-99%) | B (60%-80%) | C (40%-60%) | D (0%-40%)
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Question 1 of 10

1. The temperature variation of a thick brick wall during periodic heating or cooling follows a sinusoidal waveform. During a period of 24 hours, the surface temperature ranges from 25 degree Celsius to 75 degree Celsius. Workout the time lag of the temperature wave corresponding to a point located at 25 cm from the wall surface. Thermo-physical properties of the wall material are; thermal conductivity = 0.62 W/m K; specific heat = 450 J/kg K and density = 1620 kg/m3

Question 1 of 10

Question 2 of 10

2. “An infinite solid is one which extends itself infinitely in all directions of space”. Identify the correct option

Question 2 of 10

Question 3 of 10

3. For a grey surface

Question 3 of 10

Question 4 of 10

4. Transmissivity is defined as

Question 4 of 10

Question 5 of 10

5. Which is true regarding lumped system analysis?
(i) Conductive resistance = 0
(ii) Convective resistance = 0
(iii) Thermal conductivity = 0
(iv) Thermal conductivity = infinity
Identify the correct statements

Question 5 of 10

Question 6 of 10

6. At a certain time instant, the temperature distribution in a long cylindrical fire tube can be represented approximately by the relation
T = 650 + 800 r – 4250 r2
Where temperature t is in degree Celsius and radius r is in meter. Find the rate of heat flow such that the tube measures: inside radius 25 cm, outside radius 40 cm and length 1.5 m.
For the tube material
K = 5.5 W/m K
α = 0.004 m2/hr

Question 6 of 10

Question 7 of 10

7. When a surface absorbs a certain fixed percentage of striking radiation the surface is called

Question 7 of 10

Question 8 of 10

8. A large plane wall, 40 cm thick and 8 m2 area, is heated from one side and temperature distribution at a certain time instant is approximately prescribed by the relation
T = 80 – 60 x +12 x2 + 25 x3 – 20 x4
Where temperature t is in degree Celsius and the distance x in meters. Make calculations for heat energy stored in the wall in unit time.
For wall material:
Thermal conductivity = 6 W/m K and thermal diffusivity = 0.02 m2/hr.

Question 8 of 10

Question 9 of 10

9. A 12 cm diameter cylindrical bar, initially at a uniform temperature of 40 degree Celsius, is placed in a medium at 650 degree Celsius with convective coefficient of 22 W/m2 K. Determine the time required for the center to reach 255 degree Celsius. For the material of the bar:
Thermal conductivity = 20 W/m K
Density = 580 kg/m3
Specific heat = 1050 J/kg K

Question 9 of 10

Question 10 of 10

10. Radiation heat transfer is characterized by

Question 10 of 10


 

Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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