Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470917855
Author: Bergman, Theodore L./
Publisher: John Wiley & Sons Inc
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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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Insulation degrades (experiences an increase in thermal
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A mechanism for hardening steel is called carburization. To achieve this process, the piece of steel is exposed to an atmosphere rich in hydrocarbon such as methane (CH4). Consider a steel with a carbide concentration of 0.25wt%, which must be treated at 950˚C. If the carbon concentration at the surface is suddenly increased to 1.20wt%, how long does it take for a penetration of 0.5mm from the surface to reach a concentration of 0.80wt%? . The diffusion coefficient for carbon in iron at this temperature is 1.6 x 10-11 m2s-1. Assume that the piece of steel is semi-finite. Use the table below.
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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- Oxygen gas is maintained at a pressure of 4 bar and 1 bar on opposite sides of a membrane. The plastic membrane is 0.4 mm thick. What is the mass flow rate of oxygen in unit area through the membrane? Diffusivity of oxygen through the plastic membrane D = 2x10-8 m2/s Solubility of oxygen in the membrane material S = 10-6 kg/m3.Paarrow_forwardAn 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'sarrow_forwardCompute 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.arrow_forward
- An 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_forwardFind the diffusitivity of air in methane and the molecular diffusion of methane, if the tank filled with a mixture of methane and air at 102 kPa and 25 ⁰C is connected to another large tank filled with a different composition of methane and air also at 102 kPa and 25 ⁰C. The connection between the tanks is a tube with an inner diameter of 50 mm and length of 150 mm. The concentration of methane in one tank is 90% by mole and in the other, 5% by mole.arrow_forwardThe wear resistance of a steel shaft is to be improved by hardening its surface by increasing the nitrogen content within an outer surface layer as a result of nitrogen diffusion into the steel; the nitrogen is to be supplied from an external nitrogen-rich gas at an elevated and constant temperature. The initial nitrogen content of the steel is 0.0020wt%, whereas the surface concentration is to be maintained at 0.50wt%. For this application, a nitrogen content of 0.10wt% at a position 0.40 mm below the surface is desired. I. Will this process be a steady state or non-steady state process? Why? II. Would you expect nitrogen to diffuse by a vacancy mechanism or an interstitial mechanism? Why?arrow_forward
- A 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_forwardQ3) 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_forward
- A 0.001 in. BCC iron foil is used to separate a high hydrogen gas from a low hydrogen gas at 650 °C. 5 ×108 H atoms/cm3 are in equilibrium on one side of the foil, and 2 × 103 H atoms/cm3 are in equilibrium on the other side. Determine (a) the concentration gradient of hydrogen; and (b) the flux of hydrogen through the foil.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 m2/s at 6750C. If the concentration on the high-pressure side of the plate is 3kg/m3 and the diffusion flux is 1.7 × 10-8 kg/m2 s . Determine the concentration on the low-pressure side of the plate if the depth of concentration of low-pressure side is 0.001 m. A) 3.2 kg/m3 B) -3 kg/m3 C) 2.1 kg/m3 D) 0.001 kg/m3arrow_forwardAn FCC iron–carbon alloy initially containing 0.25 wt% C is exposed to an oxygen-rich and carbon-free atmosphere at 1400 K. 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 (x, in mm) will the carbon concentration 0.10 wt% after a 8-h treatment? The value of D at 1400 K is 6.9 x10-11 m2/s. Round your answer to 2 decimal place.arrow_forward
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