University of Mumbai 2009-1st Sem M.E Thermal Engineering Advanced Heat Transfer - - Question Paper
V-Bx-l-0*>-F.-St:an-50
3256-09. ADVNff<L* HtT BB-5619
(4 Hours) (Total Marks :
N.B : (1) Question No.l is compulsory.
(2) Answer any four questions out of remaining six questions.
(3) Answers to all parts of a question should be written together and one below the other.
(4) Assume any suitable data wherever required but justify the same.
1. (a) Derive the following equation 10
dx2 + k a dt
(b) What are the practical examples where there is internal heat generation ? 4
(c) The thermal conductivity of a plane wall of thickness L varies ask(T) = k0(I + (3T2) 6 where ko and p are constants. The wall temperature varies from Tj at x = 0
to T2 at x = L. Assuming steady state, derive a relation for the heat transfer rate through the wall.
2. A wire of radius 1 mm and 10m long is wrapped with a plastic coating 1 mm 20 thick (k = 0. i 5 W /mK). A current of 5 A passes through the wire, with a voltage drop of 8 V. If the insulated wire is exposed to an ambient at 35C with h = 24 W/m2K, determine the temperature at the interface of the wire and plastic layer. Derive any equations used.
3. (a) By deriving the equation governing heat transfer from a pin fin find the heat 10 transferred from the fin. Assume insulated fin tip boundary condition.
(b) Explain fin efficiency and fin effectiveness. With respect to a pin fin, discuss 10 the effects of the following on these two parameters :
(i) Length (ii) Diameter (iii) Convection heat transfer coefficient.
4. (a) A square plate of side a1 is bounded by the lines x = 0, x = a, y = 0, y = a. 10 The edges x = 0, x = a, y = 0, are kept at zero temperature while the edge y = a is kept at 50C. Find the steady state temperature distribution in the plate.
(b) Explain the energy balance method to derive the finite difference formulation 10 of the above mentioned plate if the surface at x = 0 is insulated and edge
x = a is subject to convective heat transfer (h) to an environment at Ta
0 5. (a) Under what conditions can lumped parameter analysis can be used in a transient 8 heat transfer problem ?
(b) Discuss factors affecting Biot No. 4
(c) Explain the use of Heisler and Grober charts. 8
6. Two large (infinite) parallel plates are separated by an air film of 4 mm thickness. 20 The lower plate is stationary and maintained at 10C, while the other plate is at 20C and is moving at a speed of 200 m/s.
(a) Beginning with differential form of conservation equation, determine the * velocity and temperature distribution between plates. Clearly specify the
assumption made and the boundary condition used for simplification.
(b) Find the location and magnitude of the maximum velocity.
(c) Calculate the temperature at a distance 2.5 mm from lower plate.
(d) Which plate has higher rate of heat flux ?
7. Write short notes on the following : 20
(a) Implicit and Explicit solution to transient heat conduction problem
(b) Hydrodynamic and thermal boundary layer
(c) Heat transfer enhancement
(d) e-NTU method for heat exchanger analysis.
S
|
Attachment: |
| Earning: Approval pending. |
