This post covers the question bank (2 marks and 16 marks ) of Unit-2 convection of the subject, Heat and Mass Transfer. This will help you to study the important and university questions as well as to get more marks in university examinations.
ANNA UNIVERSITY,CHENNAI
REGULATION 2013
DEPARTMENT OF MECHANICAL ENGINEERING
YEAR/SEMESTER: III/V
SUBJECT CODE/NAME: ME 6502/ HEAT AND MASS TRANSFER
UNIT 2-CONVECTION
PART- A (Two Marks )
1. What are hydro dynamic and thermal boundary layer thickness?
2. What is meant by natural and forced convection?
3. State Newton' s law of convection.
4. What are the dimensionless parameters used in forced convection?
5. Define boundary layer thickness.
6. Indicate the concepts or significance of boundary layer.
7. Define convection and write it's types.
8. Draw the velocity and temperature profiles for free convection on a hot vertical plate.
9. Define Prandl number and Grashoff number with its significance.
10. Define Reynolds number and Nusselt number with its significance.
11. Differentiate laminar and turbulent flow.
12. In which mode of heat transfer is the convection heat transfer coefficient usually higher. Why?
PART- B (16 Marks )
1.(a)When 0.6 kg of water per minute is passed through
a tube of 2 cm diameter, it is found to be heated from
20oCto 60oC. The heating is achieved by condensing
steam on the surface of the tube and subsequently the
surface temperature of the tube is maintained at
90o C. Determine the length of the tube required
for fully developed flow.(10)
(b)Sketch the boundary layer development of a flow
over a flat plate and explain the significance of the
boundary layer. (6)
2.Air at 25 oC flows past a flat plate at 2.5 m/s. the plate measures 600 mm X 300 mm and is maintained at a uniform temperature at 95 oC. Calculate the heat loss from the plate, if the air flows parallel to the 600 mm side. How would this heat loss be affected if the flow of air is made parallel to the 300 mm side. (16)
3.A vertical pipe 80 mm diameter and 2 m height is maintained at a constant temperature of 120 o C. the pipe is surrounded by still atmospheric air at 30o C . Find heat loss by natural convection . (16)
4. A plane wall 20 cm thickness generates heat at the rate of 5 x 104 W/m3 when an electric current is passed through it. The convective heat transfer
coefficient between each face of the wall and ambient air is 60 W/m2K. Determine
(a) The surface temperature
(b) The maximum temperature in the wall. Assume ambient air temperature to be 25°C and the thermal conductivity of the wall material to be 16 W/mK. (16)
5.A large vertical plate 5 m high is maintained at 100°C and exposed to air at 30°C Calculate the convection heat transfer coefficient. (16)
6. (a)Air at 400 K and 1 atm pressure flows at a speed of 1.5 m/s over a flat plate of 2 m long. The plate is maintained at a uniform temperature of 300 K. If the plate has a width of 0.5 m, estimate the heat transfer coefficient (12)
(b) Define the term convection and distinguish between free and forced convection(4)
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