GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-V (NEW) EXAMINATION - SUMMER 2019
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Subject Code: 2153502 Date: 31/05/2019Subject Name: Introduction to Heat Transfer
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
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2. Make suitable assumptions wherever necessary.3. Figures to the right indicate full marks.
Q.1 (a) What are the modes of heat transfer? 03
(b) What is emissivity? Explain briefly. 04
(c) Derive the expression of critical thickness of sphere. 07
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Q.2 (a) What are the application of fins? 03
(b) Derive equation to calculate the rate of heat flow through sphere. 04
(c) Derive the expression for LMTD in parallel flow heat exchanger. 07
OR
(c) Derive the expression for NTU in parallel flow heat exchanger. 07
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Q.3 (a) Based on types, classify heat exchangers. 03
(b) Explain the concept of Black body. 04
(c) Explain effect of temperature on thermal conductivity. 07
OR
Q.3 (a) Explain natural convection phenomena. 03
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(b) Give the physical significance of (i) Biot number (ii) Fourier number. 04(c) Which side of shell and tube heat exchanger will you select to pass 07
corrosive, viscous and high pressure fluid?
Q.4 (a) Explain about various feed arrangement used in multiple effect evaporator. 03
(b) Explain significance of Nusselt, Prandtl and Reynold’s number. 04
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(c) State the differences between film wise and Drop wise condensation. 07 OR
Q.4 (a) State the parts of heat exchangers. 03
(b) A small blackbody has a total emissive power of 5 kW/m². Determine its 04
surface temperature.
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(c) Using Fourier’s law derive an expression for heat transfer by conduction 07through cylindrical surface:
Q.5 (a) Discuss in brief about Boiling point elevation. 03
(b) Discuss briefly about multiple effect evaporation. 04
(c) An evaporator is operating at atmospheric pressure. It is desired to 07
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concentrate the feed from 5% solute to 20% solute at a rate of 5000 kg/h.Dry saturated steam at a pressure corresponding to saturation temperature of
399 K is used. The feed is at 298 K and boiling point rise is of 5 K. Overall
heat transfer coefficient is 2350 W/m²K. Calculate economy and heat
transfer area for evaporator.
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Latent heat of condensation of steam at 399 K is 2185 kJ/kg
Latent heat of evaporation of water at atmospheric pressure and 373 K is
2257 kJ/kg
Specific heat of feed = 4.187 kJ/kg K
OR
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Q.5 (a) An evaporator operating at atmospheric pressure is fed at rate of 10000 kg/h 03of weak liquor containing 4 % caustic soda. The liquor leaving the
evaporator contains 25% caustic soda. Find capacity of evaporator.
(b) Explain Wien’s displacement. 04
(c) Explain in detail various regions in pool boiling. 07
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This download link is referred from the post: GTU BE 2019 Summer Question Papers || Gujarat Technological University
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