Subject Code: 160202
GUJARAT TECHNOLOGICAL UNIVERSITY
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BE - SEMESTER- VI (Old) EXAMINATION - WINTER 2019
Subject Name: Automobile Heat Transfer
Date: 16/12/2019
Time: 02:30 PM TO 05:00 PM
Total Marks: 70
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Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
Q.1 (a) Distinguish between the conduction, convection and radiation heat transfer. [07]
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(b) Derive the general heat conduction equation in Cartesian coordinates. [07]
Q.2 (a) Explain the following terms. [07]
a) Efficiency of fin
b) Effectiveness of fin
c) Biot number
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(b) Write a short note on Radiator used in Car including construction, working and application. [07]
OR
Q.3 (a) It is required to heat oil to about 300 °C for frying purpose. A ladle is used in the frying. The section of the handle is 5 mm x 18 mm. the surrounding are at 30 °C. The conductivity of the material is 205 W/m°C. If the temperature at a distance of 380 mm from the oil should not reach 40 °C, determine the convective heat transfer coefficient. [07]
(b) Write short notes on the following: (a) Absorptivity, (b) Grey body, (c) Intensity of radiation and, (d) Black body. [07]
Q.4 (a) Derive Von-Karman integral momentum equation for hydrodynamic boundary layer over a flat plate. [07]
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OR
(b) The effective temperature of a body having an area of 0.12 m2 is 527 °C. Calculate the following: [07]
- The total rate of energy emission
- The intensity of normal radiation
- The wavelength of maximum monochromatic emissive power.
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Q.5 (a) State any three laws of radiation. [07]
(b) What are the functions of cap which is used on a radiator? Explain construction and working of a radiator cap. [07]
Q.3 (a) In a Counter flow type double pipe, HE, water is heated from 25 °C to 65 °C by an oil with specific heat 1.45 KJ/kg K and mass flow rate of hot water is 0.9 KJ/s. the oil is cooled from 230 °C to 160 °C. If the overall HT coefficient is 420 W/m2°C. Calculate, the rate of Heat transfer, the mass flow rate of water and the surface area of Heat exchanger. [07]
OR
(b) Explain the following terms: [07]
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a) NTU
c) Overall heat transfer coefficient.
Q4 (a) Derive an expression for logarithmic mean temperature difference (LMTD) for Parallel flow heat exchanger. [07]
(b) What are the functions of cap which is used on a radiator? Explain construction and working of a radiator cap. [07]
Q4 (a) Explain the circumstances under which natural convection occurs. Differentiate between natural and forced convection. [07]
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OR
(b) Using Buckingham’s p theorem, show that the free convection is given by Nu= ¢ (Gr.) (Pr.) [07]
Q5 (a) Write a short note on heat pipe stating principle of operation, types and applications. [07]
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