B.TECH - Semester 6 heat and mass transfer Question Paper 2019 (jun)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- 604 : HEAT AND MASS TRANSFER (MU) Time : 3 Hours Max. Marks : 100 Instructions :
- Answer all questions from Part A and one full question from each module of Part B.
- Heat and Mass transfer data book is permitted. PART - A
- Discuss the mechanism of heat conduction in solids and fluids.
- Consider a hollow sphere, $r_{1} \leq r \leq r_{2}$ has its boundary surfaces at $r_{1}$ and $r_{2}$ maintained at uniform temperatures $T_{1}$ and $T_{2}$ respectively. Write down the mathematical formulation for one dimensional steady state heat co...
- What do you understand by lumped heat capacity model? Under what circumstance a heat transfer model is treated as lumped? State two practical. situations where lumped heat capacity model is applicable.
- Differentiate between fin efficiency and fin effectiveness. Which is more significant from practical point of view and why?
- Which are the dimensionless numbers involved in free convection? Elucidate their significance in analyzing free convection problems. P.T.O.
- Explain, briefly, the difference between pool boiling and flow boiling.
- Define intensity of radiation. How is it related to total emissive power of a black body?
- What do you mean by radiation configuration factor? Why is it used?
- What is a gray body? How does spectral emissivity vary for a gray body and for a real body?
- Explain phenomenon of equimolar counter diffusion. Sketch the distribution of partial pressures across distance in equimolar counter diffusion of a binary gas mixture. ( $10 \times 4=40$ Marks ) PART - B Module - I
- (a) The thermal conductivity of a plane wall may be approximated by a linear expression of the form $k=k_{0}+a T$, where ' $k_{0}$ ' is a positive constant and ' $a$ ' is a coefficient that may be positive or negative. Obtain an expression for the he...
- (b) The wall of an industrial furnace consists of a fireclay brick of thickness $L_{1}=0.20 \mathrm{~m}$ of thermal conductivity $k_{1}=1.0 \mathrm{~W} / \mathrm{mK}$ which is covered on the outer surface with a layer of insulating material of thickn...
- (a) Obtain an expression for temperature - time history of a lumped heat capacity model during cooling in a quiescent fluid. State the important assumptions used in deriving the expression.
- (b) A plane wall of thickness 0.1 m and thermal conductivity $25 \mathrm{~W} / \mathrm{m} . \mathrm{K}$ having uniform volumetric heat generation of $0.3 \mathrm{MW} / \mathrm{m}^{3}$ is insulated on one side, while the outer side is exposed to a flu...
- (a) Derive the expression for critical radius of insulation on a sphere and show that at critical radius of insulation, the heat loss from the sphere will be maximum.
- (b) Water at a mean temperature $80^{\circ} \mathrm{C}$ and a mean velocity $0.15 \mathrm{~m} / \mathrm{s}$ flows inside a thin walled horizontal copper tube of inside diameter 2.5 cm . At the outer surface of the tube, heat is dissipated by free con...
- (i) the tube wall temperature, (ii) the overall heat transfer coefficient and (iii) the heat loss per meter length of tube.
- (a) Aluminium fins of rectangular profile are attached on a plane wall with 5 mm spacing. The fins have thickness equal to 1 mm , length equal to 10 mm and thermal conductivity equal to $200 \mathrm{~W} / \mathrm{m}-\mathrm{K}$. The wall is maintaine...
- (i) Determine the fin efficiency (ii) Determine the heat loss per square meter of wall surface.
- (b) Air at a pressure of $6 \mathrm{kN} / \mathrm{m}^{2}$ and a temperature of $350^{\circ} \mathrm{C}$ flows with a velocity of $8 \mathrm{~m} / \mathrm{s}$ over a flat plate of length 50 cm . Estimate the cooling rate per unit width of the plate ne...
- (a) Consider a black body at 1449 K emitting into air.
- (i) Determine the wavelength at which the black body spectral emissive power is maximum. (ii) Calculate the corresponding spectral emissive power and the spectral black body radiation intensity.
- (b) Two large parallel plates at $T_{1}=800 \mathrm{~K}$ and $T_{2}=600 \mathrm{~K}$ have emissivities $\varepsilon_{1}=0.5$ and $\varepsilon_{2}=0.8$, respectively. A radiation shield having an emissivity $\varepsilon_{s}=0.05$ on both sides is plac...
- (a) Obtain an expression for mass transfer by steady state diffusion through a plane membrane.
- (b) Estimate the rate of evaporation of toluene from the bottom of a deep, narrow cylindrical vessel to air at 291.7 K flowing over the top surface of the vessel. The diffusivity of air toluene vapour is $0.826 \times 10^{-5} \mathrm{~m}^{2} / \mathr...