GTU BE/B.Tech 2018 Winter Question Papers || Gujarat Technological University
Subject Code: 160202
GUJARAT TECHNOLOGICAL UNIVERSITY
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BE - SEMESTER-VI (OLD) EXAMINATION - WINTER 2018
Subject Name: Automobile Heat Transfer
Time: 02:30 PM TO 05:00 PM
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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| Q.1 (a) | Write down general heat conduction equation for Cartesian co-ordinate and derive equation for heat transfer through a plane wall. | 07 |
| (b) | What is convection? Explain types of convection and explain Newton’s law of cooling. | 07 |
| Q.2 (a) | “It is true that insulation is provided to reduce heat transfer rate but due to insulation heat transfer rate is not reduced always” Justify the statement analytically. | 07 |
| (b) | Explain hydrodynamic (velocity) boundary layer. | 07 |
| OR | ||
| (b) | A wall of a furnace is made up of inside layer of silica brick 120 mm thick covered with a layer of magnesite brick 240 mm thick. The temperature at the inside surface of silica brick wall and outside surface of magnesite brick wall are 725°C and 110°C respectively. The contact thermal resistance between the two walls at the interface is 0.0035°C/W per unit wall area. If thermal conductivities of silica and magnesite bricks are 1.7 W/mK and 5.8 W/mK, Calculate 1. Rate of heat loss unit area of wall 2. Temperature drop at the interface. | 07 |
| Q.3 (a) | Derive an expression for heat flow through ‘Rectangular Fin’. | 07 |
| (b) | The resistance R experienced by a partially submerged body depends upon the velocity V, length of the body L, viscosity of fluid µ, density of fluid ? and gravitational acceleration g. Obtain a dimensionless expression for R using Buckingham p method. | 07 |
| OR | ||
| Q.3 (a) | Write a short notes on the following: (A) Total emissive power, (B) Irradiation, (C) Radiosity, (D) Gray Body. | 07 |
| (b) | Assuming the sun to be a black body having a surface temperature of 5800 K, calculate (a) total emissive power, (b) the wavelength at which the maximum spectral intensity occurs, (c) the maximum value of Eb? (d) the total amount of radiant energy emitted by the sun per unit time if its diameter can be assumed to be 1.391x109 m. | 07 |
| Q.4 (a) | Derive an expression for LMTD in case of counter flow heat exchanger. | 07 |
| (b) | An oil of 0.27 kg/sec (Cp=2.09 kJ/kg K) has to be cool from 80°C to 40°C using coolant flow of 0.27 kg/sec (Cp= 4.18 kJ/kg K) at 30°C. Give your choice for selection of heat exchanger with reason. Calculate the area of heat exchanger. | 07 |
| OR | ||
| Q.4 (a) | Derive formula for effectiveness of parallel flow heat exchanger. | 07 |
| (b) | What do you mean by fouling? State the causes of fouling. | 07 |
| Q.5 (a) | What is the function of radiator in an automobile? Explain with a neat sketch construction and working of a radiator. | 07 |
| (b) | What is boiling? Explain boiling regimes. | 07 |
| OR | ||
| Q.5 (a) | What are the functions of cap which is used on a radiator? Explain construction and working of a radiator cap. | 07 |
| (b) | What is condensation? Explain film wise condensation and drop wise condensation. | 07 |
Date: 15/12/2018
Total Marks: 70
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