ODD SEMESTER EXAMINATION (2017-18) HEAT & MASS TRANSFER

Heat & Mass Transfer (NME-504)

Section-Wise Important Questions & Study Notes

SECTION–A

(Attempt ALL | 2 × 10 = 20)

Focus on definitions and significance. Keep answers 2–3 lines.

Overall Heat Transfer Coefficient (U)
It represents the combined effect of conduction, convection, and fouling on heat transfer across a composite system.

Significance of Heat Transfer
Heat transfer is essential in energy conversion, power generation, refrigeration, heating, cooling, and industrial processes.

Fin Effectiveness & Efficiency
Effectiveness compares heat transfer with fin to without fin; efficiency is the ratio of actual heat transfer to ideal heat transfer from a fin.

Heisler’s Charts
They provide quick solutions for transient heat conduction problems using Biot and Fourier numbers.

Gray Body
A gray body emits a constant fraction of blackbody radiation at all wavelengths.

Prandtl Number (Pr)
Ratio of momentum diffusivity to thermal diffusivity; indicates relative thickness of velocity and thermal boundary layers.

Intensity of Radiation
Radiant energy emitted per unit area per unit solid angle.

Radiation Shield
A low-emissivity surface placed between hot and cold bodies to reduce radiative heat transfer.

Condensation & Types
Phase change from vapor to liquid; types include filmwise and dropwise condensation.

Classification of Heat Exchangers
Based on flow arrangement (parallel, counter, cross), construction (double-pipe, shell-and-tube), and phase change.

SECTION–B

(Attempt any THREE | 10 × 3 = 30)

Mix of numericals, derivations, and explanations.

1. Composite Wall (Furnace Wall) – Numerical

Prepare:                                                                Thermal resistance network

Interface temperatures                                         Heat loss per unit area
Write steps clearly with units.

2. Rectangular Fin (Infinite Length)

Derive temperature distribution and heat transfer.
Mention advantages (increased area) and applications (engines, radiators).

3. Flat Plate Boundary Layer (Exact Solution)

Calculate:                                                               Hydrodynamic & thermal boundary layer thickness

Drag force per unit width                                      Local heat transfer coefficient and heat rate
Use Re, Pr, Nu relations correctly.

4. Diffuse Emitter & Shape Factor

Explain diffuse emission and view (shape) factor; mention reciprocity and summation rules.

5. Pool Boiling

Define pool boiling and explain regimes:              Natural convection

Nucleate boiling                                                    Transition boiling

Film boiling
Include a boiling curve sketch.

SECTION–C

(Attempt any ONE | 10 × 1 = 10)

3(a) Combined Convection–Radiation (Plate) – Numerical

Compute inside plate temperature considering convection loss and given radiation loss.

OR

3(b) Heat Conduction Equation (Cylindrical Coordinates)

Derive the general equation and explain assumptions.