JNTU
JNTU B.Tech II FLUID MECHANICS AND HEAT TRANSFER Previous Question Paper (December - 2017 - 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
Define Uniform flow and non-uniform flow.
Answer
Uniform flow is a flow in which the velocity at any given time does not change with respect to space (distance) along the direction of flow. Non-uniform flow is a flow in which the velocity changes from point to point along the stream line at any given instant.
Define the equation of continuity.
Answer
The equation of continuity is based on the principle of conservation of mass. It states that for a steady, one-dimensional flow of an incompressible fluid, the mass flow rate remains constant across any cross-section of a conduit. Mathematically, it is expressed as:
where A is the cross-sectional area and v is the average velocity at the respective sections.
What is venturimeter?
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Explain any one application of momentum equation
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Define thermal conductivity and explain its significance in heat transfer.
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What are the three modes of heat transfer?
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Explain about thermal boundary layer.
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Explain Rayleigh’s method.
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Explain about monochromatic emissive power.
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Explain the significance of NTU method.
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PART-B
List all fluid properties and derive Newton’s law of viscosity.
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Find the height through which water rises by capillary action in a glass tube of 2mm bore if the surface tension at the prevailing temperature is 0.075 N/m.
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Define stream function and velocity potential. What are their uses?
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Determine whether the following velocity components satisfy the continuity equation: i) u = cx, v = -cy ii) u = -cx/y , v = c log xy
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Derive Bernoulli’s equation for the flow of an incompressible frictionless fluid from consideration of momentum.
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A horizontal venturimeter with inlet and throat diameters 30cm and 15 cm respectively is used to measure the flow of water. The reading of Differential manometer connected to the inlet and the throat is 20 cm of Mercury. Determine the rate of flow. Take Cd = 0.98.
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Find the discharge of water flowing through a pipe 30 cm diameter placed in an inclined position where a venturimeter is inserted, having a throat diameter of 15 cm. The difference of pressure between the main and throat is measured by a liquid of sp. Gr. 0.6 in an inverted U- tube which gives a reading of 30 cm. The loss of head between the main and throat is 0.2 times the kinetic head of the pipe.
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A cylinder 1 m long and 5 cm in diameter is placed in an atmosphere at 45°C. It is provided with 10 longitudinal straight fins of material having k = 120 W/mK. The height of 0.76 mm thick fins is 1.27 cm from the cylinder surface. The heat transfer coefficient between cylinder and atmospheric air is 17 W/m²K. Calculate the rate of heat transfer and the temperature at the end of fins if surface temperature of cylinder is 150°C.
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Describe the mechanism of i) Heat Conduction ii) Convection iii) Radiation
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A hot plate of length 0.75m, width 0.5m and thickness 2cm is placed in air stream at 20°C. It is estimated that a total of 300W is lost from the plate surface by radiation. Taking the convective heat transfer coefficient as 25 W/m²K, and the thermal conductivity of the plate as 43 W/mK, calculate the inside temperature of the plate?
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Compare the variations of velocity, temperature and local heat transfer coefficient along a vertical plate for the plate under natural convection and force convection?
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A flow through a long rectangular (30 cm height × 60 cm width) air conditioning duct maintains the outer duct surface temperature at 15°C. If the duct is uninsulated and exposed to air at 25°C, calculate the heat gained by the duct per meter length, assuming it to be horizontal?
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Using Buckingham π dimensional analysis, derive an expression for heat transfer coefficient for a free convection. The variables involved are h(heat transfer coefficient), ρ(fluid density), D(tube diameter), µ(fluid viscosity), cp(specific heat), k (thermal conductivity), βg ∆t (β - coefficient of volume expansion of the fluid, ∆t - difference of temperatures between the heated surface and the undisturbed fluid).
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Derive an expression for logarithmic mean temperature difference (LMTD) in case of counter flow heat exchanger.
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A vertical plate 2.8 m high is maintained at 54°C in the presence of saturated steam at atmospheric pressure. Calculate the heat transfer per unit width.
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What is the Stefan-Boltzmann Law? Explain the concept of total emissive power of a surface?
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Explain how the heat exchangers are classified.
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