Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470501979
Author: Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, Adrienne S. Lavine
Publisher: Wiley, John & Sons, Incorporated
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Chapter 14, Problem 14.32P
A platinum catalytic reactor in an automobile is used to convert carbon monoxide to carbon dioxide in an oxidation reaction of the form
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An FCC iron-carbon alloy initially containing 0.35 wt% C is exposed to an oxygen-rich and virtually carbon-free atmosphere at 1400 K (1127°C). Under these circumstances the carbon diffuses from the alloy and reacts at the surface
with the oxygen in the atmosphere; that is, the carbon concentration at the surface position is maintained essentially at 0 wt% C. (This process of carbon depletion is termed decarburization.) At what position will the carbon concentration he 0.15 wt% after a 10-h treatment? The value of D at 1400 K is 6.9 x 10m²'s
Compute diffusion coefficients for the interdiffusion of carbon in both (a) α-iron (BCC) and (b) γ-iron (FCC) at 1000˚C. Assume that D0 for the interdiffusion of carbon in α-iron and in γ-iron are 1.1 × 10-6 and 2.3 × 10-5 m2/s, respectively, and that Qd are 80 and 148 kJ/mol, respectively.
Chapter 14 Solutions
Fundamentals of Heat and Mass Transfer
Ch. 14 - Assuming air to be composed exclusively O2 and N2...Ch. 14 - Consider an ideal gas mixture of n species. (a)...Ch. 14 - A mixture of CO2 and N2 is in a container at 25C ,...Ch. 14 - A He-Xe mixture containing 0.75 mole fraction of...Ch. 14 - Estimate values of the mass diffusivity for binary...Ch. 14 - Consider air in a closed, cylindrical container...Ch. 14 - An old-fashioned glass apothecary jar contains a...Ch. 14 - Consider the evaporation of liquid A into a column...Ch. 14 - An open pan of diameter 0.2 m and height 80mm...Ch. 14 - A spherical droplet of liquid A and radius...
Ch. 14 - The presence of a small amount of air may cause a...Ch. 14 - A laboratory apparatus to measure the diffusion...Ch. 14 - A thin plastic membrane is used to separate helium...Ch. 14 - Prob. 14.16PCh. 14 - Consider the radial diffusion of a gaseous species...Ch. 14 - Prob. 14.18PCh. 14 - Prob. 14.19PCh. 14 - Prob. 14.20PCh. 14 - Hydrogen at a pressure of 2 atm flows within a...Ch. 14 - Prob. 14.22PCh. 14 - Insulation degrades (experiences an increase in...Ch. 14 - Prob. 14.24PCh. 14 - Helium gas at 25°C and 4 bars is stored in a...Ch. 14 - Prob. 14.26PCh. 14 - An experiment is designed to measure the partition...Ch. 14 - Ultra-pure hydrogen is required in applications...Ch. 14 - Nitric oxide (NO) emissions from automobile...Ch. 14 - Pulverized coal pellets, which may be approximated...Ch. 14 - To enhance the effective surface, and hence the...Ch. 14 - A platinum catalytic reactor in an automobile is...Ch. 14 - A novel process has been proposed to create a...Ch. 14 - Consider a spherical organism of radius r0 within...Ch. 14 - Prob. 14.35PCh. 14 - Consider combustion of hydrogen gas in a mixture...Ch. 14 - Prob. 14.37PCh. 14 - As an employee of the Los Angeles Air Quality...Ch. 14 - Prob. 14.39PCh. 14 - A large sheet of material 4() mm thick contains...Ch. 14 - Prob. 14.41PCh. 14 - Prob. 14.43PCh. 14 - Prob. 14.44PCh. 14 - Prob. 14.46PCh. 14 - If an amount of energy Q0(J/m2) is released...Ch. 14 - The presence of CO2 in solution is essential to...Ch. 14 - Consider a DVD similar to that of Problem 5.99. To...Ch. 14 - Prob. 14.50PCh. 14 - Prob. 14.51PCh. 14 - Prob. 14.52PCh. 14 - Prob. 14.55PCh. 14 - A person applies an insect repellent onto an...
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- An iron-carbon alloy initially containing 0.268 wt% C is exposed to an oxygen-rich and virtually carbon-free atmosphere at 1040°C. Under these circumstances the carbon diffuses from the alloy and reacts at the surface with the oxygen in the atmosphere; that is, the carbon concentration at the surface position is maintained essentially at 0.0 wt% C. At what position will the carbon concentration be 0.201 wt% after a 7 h treatment? The value of D at 1040°C is 2.5 × 10-¹1 m²/s. erf(z) erf(z) 0.55 0.5633 1.3 0.025 0.0282 0.60 0.6039 1.4 0.9523 0.0564 0.65 0.6420 1.5 Z 0.00 0.05 0.15 0.0000 0.10 0.1125 0.70 0.6778 0.20 Z 0.1680 0.75 0.7112 1.7 0.2227 0.80 0.7421 1.8 0.45 0.4755 1.1 0.50 0.5205 Z 1.6 1.2 0.9103 erf(z) 0.9340 2.8 0.9661 0.25 0.2763 0.85 0.7707 1.9 0.9928 0.30 0.3286 0.90 0.7970 2.0 0.9953 0.35 0.3794 0.95 0.8209 2.2 0.40 0.4284 1.0 0.8427 2.4 0.9763 0.9838 0.9891 0.9981 0.8802 2.6 0.9998 0.9993 0.9999arrow_forwardAn iron-carbon alloy initially containing 0.240 wt% C is exposed to an oxygen-rich and virtually carbon-free atmosphere at 1100°C. Under these circumstances the carbon diffuses from the alloy and reacts at the surface with the oxygen in the atmosphere; that is, the carbon concentration at the surface position is maintained essentially at 0.0 wt% C. At what position will the carbon concentration be 0.180 wt% after a 7 h treatment? The value of D at 1100°C is 3.7 × 10-11 m2/s.arrow_forwardA diffusion couple of two metals, A and B, was fashioned as shown in Figure 5.1. After a 26 hour heat treatment at 1170°C (and subsequent cooling to room temperature) the concentration of A is 4.0 wt% at the 11-mm position within metal B. If another heat treatment is conducted on an identical diffusion couple, only at 701°C for 26 hours, at what position (in mm) will the composition be 4.0 wt% A? The preexponential and activation energy values for the diffusion of A in B are 2.4 x 10-4 m²/s and 154 kJ/mol, respectively. i mmarrow_forward
- Q3) Pulverized coal pellets, which may be approximated as carbon spheres of radius R = 1.5 mm, are burned in a pure oxygen atmosphere at 1400K and 1.2 atm. Oxygen is transferred to the particle surface by diffusion, where it is consumed in the reaction, C(s) + O2(g) → CO2(g). The reaction rate is first order and of the form R = -k.Co2 at r = R where k = 0.12 m/s. This is the reaction rate per unit surface area of the carbon pellets. Neglecting change in R, determine the steady-state O2 molar consumption rate in mol/s. At 1400K, the binary diffusion coeffici for O2 and CO2 is 1.6x104 m2/s.arrow_forward34) Hydrogen is allowed to diffuse through a palladium plate that is 0.015m thick at 500°C. The concentrations of carbon at the two faces are 0.65 and 0.30 kg/m3, which are maintained constant. The diffusion coefficient at this temperature is 6.13x1011 m²/s. Calculate the diffusion flux in units of kg/m2s.arrow_forwardConsider a sheet of Iron which is maintained in an atmosphere filled with nitrogen and is permitted to achieve and steady state diffuseion. The thickness of the sheet is 6.5mm. The diffusion coefficient of nitrogen in iron is 1.9 × 10 -11 m 2 /s at 675 0 C.arrow_forward
- The viscosity values for the H2 and Freon-12 gas mixtures at 25 ° C and 1 atm pressure and the mole fractions of the mixture are given in the table below. For H2 and Freon-12, calculate the viscosity values of the mixture for 3 different compositions using pure viscosity values. H2 Mol Frac. 0,00 0,25 0,50 0,75 1,00 Viscosity (µ) x 106 (poise) 124,0 128,1 131,9 135,1 88,4arrow_forwardA copper–nickel diffusion couple similar to that shown in Figure 5.1a is fashioned. After a 700-h heat treatment at 1100C (1373 K), the concentration of Cu is 2.5 wt% at the 3.0-mm position within the nickel. At what temperature must the diffusion couple be heated to produce this same concentration (i.e., 2.5 wt% Cu) at a 2.0-mm position after 700 h? The preexponential and activation energy for the diffusion of Cu in Ni 2.7*10^-5(m^2/s) and 256 kJ/mol.arrow_forwardA membrane is to be manufactured to the following specifications. At 700°C the leak rate of hydrogen at steady state is not to exceed 103 mol cm2 hr' when the concentrations of hydrogen are maintained at Chigh = 7.7 × 1019 atoms cm³ on one side of the membrane and Clow effectively zero on the other side. Determine the minimum thickness, {, of iron foil that will meet these requirements. The diffusion coefficient of atomic hydrogen in iron, DH, at 700°C is 3.091x104 cm? s. Express your answer in units of cm.arrow_forward
- Carbon is allowed to diffuse through a steel plate 10mm thick. The concentrations of carbon at the two faces are 0.85???3 and 0.40???3 which are maintained constant. If the preexponential and activation energy are 5.0 × 10 ―7 ?2??? and 77,000 ????, compute the temperature at which the diffusion flux is 6.3 × 10 ―10 ???2 ∙ ???arrow_forwardThermo-fluid Mechanics I want a quick solutionarrow_forwardANSWER THERMOFLUIDS QUESTIONSarrow_forward
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