ME-701 Heat and Mass Transfer - Dec 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 8 Marks
   aExplain heat transfer laws applicable for:

   1. i)Conduction
   2. ii)Convection and
   3. iii)Radiation
2. 6 Marks
   bA wall is constructed of a section of stainless steel [k=16 W/m K], 5.0 mm thick with identical layers of plastic on both sides of the steel. The overall heat-transfer coefficient, considering convection on both sides of the plastic, is 110 W/m2 K. If the overall temperature difference across the arrangement is 50 degC, calculate the temperature difference across the stainless steel.
   How to answer

   • Overall heat transfer coefficient concept
   • Thermal resistance in series
   • Heat flux from overall delta T
   • Temperature drop across steel resistance
3. 8 Marks
   aWhat is the concept of critical insulation-thickness? Derive its expression as applicable in cylinders and then discuss the plot obtained between heat transfer and radius.
4. 6 Marks
   bA tube 2 cm outer diameter maintained at uniform temperature of T1 is covered with insulation (K=0.20 W/m K) to reduce heat loss to the ambient air at T_infinity with heat transfer coefficient at ambient is 15 W/m2 K. Calculate (i) the critical thickness of insulation and (ii) the ratio of heat loss from the tube with insulation to that without insulation.
5. 8 Marks
   aWhat is the meaning of extended surfaces (fins) and where they are used? For a rectangular plate of uniform cross-section, derive the governing equation.
6. 6 Marks
   bA straight rectangular fin 2.0 cm thick and 14 cm long is constructed of Chrome steel with 20% chromium and placed on the outside of a wall maintained at 200 degC. The environment temperature is 15 degC, and the heat transfer coefficient for convection is 20 W/m2 K. Calculate the heat lost from the fin per unit depth.
7. 8 Marks
   aDerive the relation in the transient heat conduction problem for infinite thermal conductivity method and then draw the variation between temperature and time.
8. 6 Marks
   bDiscuss the flow regimes obtained in the convection heat transfer with the help of neat diagram.
9. 8 Marks
   aWhat is Buckingham pi-theorem? Write its statement and derive a correlation between Nusselt number, Reynold's number and Prandtl number in a forced convection problem.
10. 6 Marks
    bAir at 1 bar and 30 degC flows across a 4.0 cm diameter cylinder at a velocity of 40 m/s. The cylinder surface is maintained at a temperature of 150 degC. Calculate the heat loss per unit length of the cylinder.
11. 8 Marks
    aExplain the broad classification of Heat Exchangers with the help of neat diagram.
12. 6 Marks
    bAir enters a cooler at 115 degC and at 3 bar and is brought to 45 degC by passing through tubes of 10 mm inner diameter surrounded by water which enters the cooler at 15 degC and leaves at 30 degC. Assuming the heat exchanger is counter flow, find the mean temperature difference. If the air velocity in the tube is limited to 6.5 m/s, find the length of the tube required. Neglect the tube resistance and assume water side heat transfer coefficient is 200 W/m2 K.
13. 8 Marks
    aDiscuss the radiant heat exchange between two black bodies separated by a non absorbing medium and hence derive the reciprocity theorem which takes into account the areas and shape factors.
14. 6 Marks
    bIf the inside surface temperature of a hemispherical cavity of 0.5 m diameter is 400 degC and its emissivity is 0.6, calculate the rate of radiant heat transfer from the cavity with the help of neat diagram.
15. 14 Marks
    Write short notes on any two of the following:

    1. i)LMTD calculation for parallel flow heat exchanger
    2. ii)Derivation of general equation of mass diffusion in stationary medium
    3. iii)Wien's displacement law in Radiation heat transfer