ISRO Mechanical Engg.: Heat Transfer Quiz 2

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Question 1

The heat flow rate through parallel walls of thickness L1, L2 and L3 and having surface areas A1, A2, and A3 thermal conductivities k1, k2, and k3, respectively and first and last walls maintained at temperatures t1 and t2 will be

• A
• B
• C
• D

Question 2

Air at 20 °C blows over a plate of 50 cm X 75 cm maintained at 250 °C. If the convection heat transfer coefficient is 25W/m² °C, the heat transfer rate is

• A2.156 kW
• B2156 kW
• C215.6 kW
• D21.56 Kw

Question 3

N_u = CR_e^mP_rⁿ represents heat transfer under

• AFree convection
• BForced convection
• CCombined convection
• DNone of the above

Question 4

A 10 kg solid at 100 °C with a specific heat of 0.8 kJ/kg °C. is inside a container of mass 40 kg at 20C with specific heat 4.0 kJ/kg °C  Estimate the temperature after a long time if the container is insulated?

• A30 °C
• B28 °C
• C26 °C
• D24 °C

Question 5

What is the net radiant interchange per square meter for two very large plates at temperatures 800 K and 500 K respectively. (The emissivity of the hot and cold plates are 0.8 abd 0.6 respectively. Stefan Boltzmann constant is 5.67 X W/).

• A10.26 kW/
• B1.026 kW/
• C102.6 kW/
• D1026 kW/

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