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This quiz contains multiple-choice problems on molecular diffusion in solids, liquids and gases, multicomponent diffusion, diffusion through variable and binary gas mixtures.
__ energy helps with molecular diffusion.
Thermal
Electrical
Internal
All of the above
Estimate the mole fraction of A if its concentration is 2 mol/cu.m and the total concentration is 5 mol/cu.m.
0.2
0.25
0.4
1
Find the partial pressure of A if the total pressure is 2 atm, the concentration of A is 2 mol/cu.m, and the total concentration is 5 mol/cu.m.
0.2 atm
0.4 atm
0.6 atm
0.8 atm
The value of N flux of A under steady-state non-diffusing B with diffusing A is
0
Constant
Infinity
None of the above
For two particles at a steady-state collision of A and B, A's J flux is 2 mol/sq.m.s. Find the J flux of B.
1
2
3
None of the above
Find the permeability if diffusivity is 2 units and solubility coefficient is 5 units (assume all are in SI units).
10 units
2.5 units
0.4 units
None of the above
Find the operation out of the following where diffusion of solids does not occur.
Adsorption
Leaching
Drying
Distillation
From the reaction [methane –> carbon + 2*(hydrogen molecule)], find the ratio of N flux of A to the total N flux of A and B (given N flux of B = -2 * N flux of A).
1
-1
2
-2
For the free convection circumstances, the following dimensionless numbers apply:
(i) Grashof number
(ii) Prandtl number
(iii) Nusselt number
Identify the correct answer out of the following
ii and iii
ii only
i and ii
i, ii and iii
If the ratio value of N flux of A to the total N flux is 1, it is a steady-state diffusion of non-diffusing B. True or false?
True
False
Estimate the heat transfer from a 40 W incandescent bulb at 125 °C to 25 °C in quiescent air. Approximate the bulb as a 50 mm diameter sphere. The approximate correlation for the convection coefficient is Nu = 0.60 (Gr Pr) 0.25, where the different parameters are evaluated at the mean film temperature. The characteristics length is the sphere's diameter.
4.71 W
5.71 W
6.71 W
7.71 W
Two horizontal steam mains with diameters 5 cm and 15 cm are to be laid in a boiler house that any mutual heat effect is precluded. The mains are at the same surface temperature of 500 °C whilst the ambient air is at 50 °C. Work out the ratios of the heat transfer coefficients.
0.136
1.316
2.136
3.136
A spherical heater of 20 cm diameter and at 60 °C temperature is immersed in a tank of water at 20 °C temperature. Determine the convective heat transfer coefficient.
458.32 W/m^2 K
558.32 W/m^2 K
658.32 W/m^2 K
758.32 W/m^2 K
For a steady-state diffusion of A through non-diffusing B, N flux of B =
0
1
2
∞
A steam pipe of 50 mm diameter and 2.5 m length is placed horizontally and exposed to still air at 25 °C. If the pipe wall temperature is 295 °C, determine the rate of heat loss. At the mean temperature difference of 160 °C, the thermo-physical properties of air are
k = 3.64 * 10 -2 W/m K
v = 30.09 * 10 -6 m^2/s
P{r}= 0.682
Β = 1/160 + 273 = 2.31 * 10^(-3) per K
1156.5 W
1146.5 W
1136.5 W
1126.5 W
