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 14.22P
To determine
Molar diffusive flux of
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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.
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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 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_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_forward
- Calculate the volume of water in ltrsarrow_forwardDiffusion of carbon into BCC iron for 12 hours at a temperature of 500 °C results in a carbon concentration of 0.2 wt% at a depth 2 mm from the surface. How long would it take to get a concentration of 0.2 wt% at a depth 3 mm from the surface at 500 °C?arrow_forward6. Exhaust gas from an automobile contains air and 105 mole fractions of CO in air at 25 degC and 1.2 atm. Express this concentration as a mass concentration (kg/m³).arrow_forward
- Find 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_forwardA plate of iron is exposed to a carburizing atmosphere on one side and a decarburizing atmosphere on the other side at 850 oC. If a condition of steady state is achieved, calculate the diffusion flux of carbon through the plate if the concentrations of carbon at positions of 5 and 10 mm beneath the carburizing surface are 1.4 and 0.8 kg/m3, respectively. Assume a diffusion coefficient of 3 x 10 -11 m2/s at this temperature.arrow_forwardCalculate w and ΔE when 1 mole of a liquid is vaporized at its boiling point (80.°C) and 1.00 atm pressure. ΔH for the vaporization of the liquid is 30.7 kJ/mol at 80.°C. Assume the volume of 1 mole of liquid is negligible as compared to the volume of 1 mole of gas at 80.°C and 1.00 atm.arrow_forward
- Nitrogen from a gaseous phase is to be diffused into pure iron at 700°C. If the surface concentration is maintained at 0.14 wt% N, what will be the concentration (in weight percent) 2.3 mm from the surface after 6.5 h? The diffusion coefficient for nitrogen in iron at 700°C is 1.4 x 10-10 m²/s. Z 0.00 0.025 0.0282 0.60 0.05 0.0564 0.30 erf(z) 0.0000 0.55 0.35 Z erf(z) 0.40 0.45 0.50 0.65 0.10 0.1125 0.70 0.6778 1.6 0.5633 1.3 0.6039 0.4755 1.1 Z 0.15 0.1680 0.75 0.7112 0.20 0.2227 0.80 0.7421 1.8 0.25 0.2763 0.85 0.7707 1.9 0.9928 0.3286 0.90 0.7970 0.5205 1.2 0.6420 1.5 1.4 0.3794 0.95 0.8209 2.2 0.4284 1.0 1.7 0.9103 2.0 erf(z) 0.9340 0.9523 0.9661 2.8 0.9763 0.9838 0.9891 0.9953 0.8427 2.4 0.9993 0.9981 0.8802 2.6 0.9998 0.9999arrow_forward(c) A 1020 steel gear is carburized at 927°C and gives the surface carbon concentration maintained at 1.2 wt%. After 8 hours, the concentration of carbon is 0.4 wt%. Note: D (C in y iron) at 927°C = 1.28 × 10*1" m²/s. Determine the depth of the carbon diffuse to the gear steel after 8 hours. (d) State the importance of case hardening in gear steel components in the steel metal industry.arrow_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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