18-51 A long 35-cm-diameter cylindrical shaft made of stainless steel 304 (k = 14.9 W/mK, p = 7900 kg/m³, cp = 477 J/kg . K. and a = 3.95 x 10-6 m²/s) comes out of an oven at a uniform temperature of 500°C. The shaft is then allowed to cool slowly in a chamber at 150°C with an average convection heat transfer coefficient of h=60W/m² K Determine the temperature at the center of the shaft 20 min after the start of the cooling process. Also, determine the heat transfer per unit length of the shaft during this time period. Solve this problem using the analytical one-term approximation method Answers: 486°C 22.270 kl

18-51 A long 35-cm-diameter cylindrical shaft made of stainless steel 304 (k = 14.9 W/mK, p = 7900 kg/m³, cp = 477 J/kg . K. and a = 3.95 x 10-6 m²/s) comes out of an oven at a uniform temperature of 500°C. The shaft is then allowed to cool slowly in a chamber at 150°C with an average convection heat transfer coefficient of h=60W/m² K Determine the temperature at the center of the shaft 20 min after the start of the cooling process. Also, determine the heat transfer per unit length of the shaft during this time period. Solve this problem using the analytical one-term approximation method Answers: 486°C 22.270 kl

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter3: Transient Heat Conduction

Section: Chapter Questions

Problem 3.10P: 3.10 A spherical shell satellite (3-m-OD, 1.25-cm-thick stainless steel walls) re-enters the...

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An ordinary egg can be approximated as a 5.5-cm-diameter sphere whose thermal conductivity of roughly W overall density of p= 1000. mk' kg m² and heat capacity of Cp = 3000; kgk k = 0.6- : The egg is initially at a uniform temperature of T₁ = 10°C and is dropped into boiling water at T = 90°C Taking the convective heat transfer coefficient to be h = 10. - determine how long it will take for the egg to W m²K reach T = 70°C. In solving this problem, please use the One-term approximation model to compute the time needed by the center of the egg and the surface of the egg to reach the desired temperature of 70 C Please discuss the difference between the three results. In solving the problem, please follow the steps below. For the One-term approximation: 1. Compute the Biot number, use the egg radius (not the diameter) as the characteristic length T-Too 2. Compute the non-dimensional excess temperature 0 = Ti-Too 3. Look up in the table the values for A₁ and ₁ for the Biot number found…
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