Question

wall 0.12 m thick having a thermal diffusivity of 1.5 x 10^6 m²/s is initially at a uniform temperature of 85°C. Suddenly one face is lowered to a temperature of 20°C, while the other face is perfectly insulated. (a) Using the explicit finite-difference technique with space and time increments of 30 mm and 300 s, respectively, determine the temperature distribu tion at t= 45 min. (b) With Ar-30 mm and At 300 s, compute 7(x, t) for 0stst where t is the time required for the temperature at each nodal point to reach a value that is within 1°C of the steady-state temper ature. Repeat the foregoing calculations for At=75 s. For each value of At, plot temperature histories for each face and the midplane.

Answer 1

Answer:

ASSUMPTIONS: (1) One-dimensional transient conduction (2) Constant properties ANALYSIS: (a) The finite-difference equations for the interior points, nodes 0, 1, 2, and 3, can be determined from Equation 5.78 T&* = FOTO-2 +2+1)+(1-2F). (1) with Fo=&at/Ax? = 1.5*10*6m/sx3005/(0.