This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: PROBLEM 4.19 KNOWN: Relation between maximum material temperature and its location, and scanning velocities. FIND: (a) Required laser power to achieve a desired operating temperature for given material, beam size and velocity, (b) Lag distance separating the center of the beam and the location of maximum temperature, (c) Plot of the required laser power for velocities in the range 0 ≤ U ≤ 2 m/s. SCHEMATIC: r b = 0.1 mm T max = 200°C = 2000 kg/m 3 c = 800 J/kg•K k = 27 W/m•K T 2 = 25°C U = 2 m/s ′ q δ ρ α = 0.45 r b = 0.1 mm T max = 200°C = 2000 kg/m 3 c = 800 J/kg•K k = 27 W/m•K T 2 = 25°C U = 2 m/s ′ q δ ρ α = 0.45 ASSUMPTIONS: (1) Steadystate conditions, (2) Constant properties, (3) Semiinfinite medium, (4) Negligible heat loss from the top surface. ANALYSIS: The thermal diffusivity of the materials is 3 = k/ ρ c = 27 W/m K / (2000 kg/m 800 J/kg K) = 16.9 × 10 m /s α ⋅ ⋅ ⋅ 6 2 (a) The Peclet number is 6 2 b Pe = Ur / 2 = 2 m/s × 0.0001 m / ( 2 × 16.9 × 10 m /s) = 8.38Pe = Ur / 2 = 2 m/s × 0....
View
Full
Document
This note was uploaded on 12/07/2010 for the course MAE Heat Trans taught by Professor Lee,j.s. during the Spring '10 term at Seoul National.
 Spring '10
 LEE,J.S.
 Heat Transfer

Click to edit the document details