JNTU
JNTU B.Tech II FLUID MECHANICS AND HEAT TRANSFER Previous Question Paper (April - 2018 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
Distinguish between ideal and real fluids.
Answer
An ideal fluid is incompressible and has zero viscosity (inviscid), meaning there is no internal friction between layers. A real fluid possesses both viscosity and compressibility, resulting in shear stress and energy dissipation during flow.
What is specific gravity? How it is related to density?
Answer
Specific gravity is the ratio of the density of a substance to the density of a standard fluid (usually water at 4°C for liquids). It is related to density by the formula:
where ρ is the density of the fluid and ρ_water is the density of water (1000 kg/m³).
State Bernoulli’s theorem.
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Define the Equation of Continuity.
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State Fourier law of heat conduction.
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List down three types of boundary conditions.
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State the application of fins.
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What are the dimensional parameters used in forced convection?
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What are the assumptions made to calculate radiation exchange between the surfaces?
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State Wien’s displacement law.
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Part B
Obtain an expression for capillary rise of a liquid.
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If the pressure at a point below the sea is 137.7 kN/m2 what is the pressure 30 meters below this point. Specific weight of ocean water is 10.06 kN/m2.
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Define viscosity. Derive Newton’s equation of viscosity. Explain the variation of shear stress with velocity gradient in the case of various fluids.
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Calculate the capillary rise in a glass tube of 3.2 mm diameter when immersed vertically in mercury. Take surface tension for mercury is 0.073 N/m.
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What is the equation of continuity? Derive it for a three-dimensional flow in the differential form.
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Discuss path line, stream line, streak line and stream tube with neat sketches.
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What is a venturimeter? Deduce an expression for the rate of flow through a venturimeter.
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Water flows through a pipe with diameters 300mm and 450mm at its two ends where the corresponding pressures are 120 kN/m2 and 400 kN/m2 respectively. If the rate of flow through the pipe is 50 lit/s, find the differences in the datum head.
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A wall is constructed of several layers. The first layer consists of masonary brick 20 cm thick of thermal conductivity 0.66 W/m K, The second layer consists of 3 cm thick of mortar of thermal conductivity 0.6 W/m K. The third layer consists of 8cm thick lime stone of thermal conductivity 0.58 W/m K and the outer layer consists of 1.2 cm thick plaster of thermal conductivity 0.6 W/mK. The heat transfer coefficient on the interior and exterior of the wall are 5.6 W/m2K and 11 W/m2K respectively. Interior room temperature is 220C and outside air temperature is -50C. Calculate:
- Overall heat transfer coefficient
- Overall thermal resistance
- The rate of heat transfer
- The temperature at the junction between the mortar and limestone.
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A steel tube (K=43.26 W/m K) of 5.08 cm of inner diameter is covered with 2.5 cm layer of insulation (K= 0.208 W/m K) the inside surface of the tube receives heat from a hot gas at the temperature of 3160C with heat transfer coefficient of 28 W/m2K. While the outer surface exposed to ambient air at 300C with heat transfer coefficient of 17 W/m2K. Calculate the heat lost for 3m length of the tube.
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What is the difference between laminar and turbulent flow on a flat plate?
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Air at 200C at a pressure of 1 bar is flowing over a flat plate at a velocity of 3 m/s. If the plate is maintained at 600C, Calculate the heat transfer per unit width of the plate. Assuming the length of the plate along the flow of air is 2m.
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Explain the principle of dimensional homogeneity. How it is utilized in deriving the dimensionless groups.
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Explain about velocity boundary layer on a flat plate.
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What is radiation shield? Why is it used?
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Calculate for the following for an industrial furnace in the form of a black body and emitting radiation at 25000C.
- Monochromatic emissive power 1.2 µm length
- Maximum emissive power.
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Derive an expression for LMTD in parallel flow and counter flow heat exchangers.
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