Download GTU BE/B.Tech 2019 Summer 6th Sem Old 160202 Automobile Heat Transfer Question Paper

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Subject Code: 160202

BE - SEMESTER-VI(OLD) - EXAMINATION - SUMMER 2019

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Subject Name: Automobile Heat Transfer

Time: 10:30 AM TO 01:00 PM

Date: 29/05/2019

Total Marks: 70

Instructions:

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1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1 (a) Derive an expression for one-dimensional steady-state heat conduction from composite wall with three layers. (07)

(b) Discuss the various regimes of boiling and explain the condition for the growth of bubbles. (07)

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OR

Q.2 (a) Explain the significance of fin efficiency and effect of Biot number on fin effectiveness. (07)

(b) Explain the circumstances under which natural convection occurs. Differentiate between natural and forced convection. (07)

OR

Q.3 (a) Derive Von-Karman integral momentum equation for hydrodynamic boundary layer over a flat plate. (07)

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(b) State and explain Wien’s displacement law. (07)

OR

Q.4 (a) A wire of 6.5mm diameter at a temperature of 60°C is to be insulated by a material having k=0.174W/m°C. Convection heat transfer coefficient (ho)=8.722W/m²°C. The ambient temperature is 20°C. For maximum heat loss, what is the minimum thickness of insulation and heat loss per meter length? Also find % increase in heat dissipation too. (07)

(b) Briefly explain the significance of following dimensionless numbers. Reynolds number and Prandtl number. (07)

OR

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Q.5 (a) Explain heat exchanger effectiveness, fouling and NTU. (07)

(b) Write a short note on heat pipe stating principle of operation, types and applications. (07)

OR

Q.6 (a) Explain with a neat sketch construction of a radiator. (07)

(b) Discuss the modes of condensation. Why dropwise condensation is preferred? (07)

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OR

Q.7 (a) Assuming the sun to be a black body having a surface temperature of 5800K, calculate (a) the total emissive power, (b) the wavelength at which the maximum spectral intensity occurs, (c) the maximum value of Eu, (d) the total amount of radiant energy emitted by the sun per unit time if its diameter can be assumed to be 1.391 x 10°m. (07)

(b) In a counter flow heat exchanger, flue gases at 800°C (Cp = 1.1kJ/kgK) with flow rate of 4kg/sec. The air on other side is flowing with 6 kg/sec at 400°C inlet temperature and 551.5°C at outlet. Take U = 100W/m²k. Determine: (a) heat transfer area needed and (b) NTU (07)

OR

Q.8 (a) Derive the expression for LMTD for parallel flow heat exchangers. (07)

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(b) What is a radiation shield? When it is used? Also write the expression for radiation heat transfer between two parallel plates with one shield. (07)