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HW #3 /Tutorial # 3 WRF Chapter 17; WWWR Chapter 18 ID Chapter 5

Tutorial # 3 WWWR #18.12 (additional data: h = 6W/m 2 -K); WRF#17.1; WWWR#18.4; WRF#17.10 ; WRF#17.14. To be discussed during the week 3-7 Feb., 2020. By either volunteer or class list. Homework # 3 (Self practice) WRF #17.9; WRF#17.16. ID # 5.6, 5.9.

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HW #3 /Tutorial # 3 WRF Chapter 17; WWWR Chapter 18 ID Chapter 5

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  1. Tutorial # 3 WWWR #18.12 (additional data: h = 6W/m2-K); WRF#17.1; WWWR#18.4; WRF#17.10 ; WRF#17.14. To be discussed during the week 3-7 Feb., 2020. By either volunteer or class list. Homework # 3 (Self practice) WRF #17.9; WRF#17.16. ID # 5.6, 5.9. HW #3 /Tutorial # 3WRF Chapter 17; WWWR Chapter 18ID Chapter 5

  2. Unsteady-State Conduction

  3. Transient Conduction Analysis

  4. Spherical metallic specimen, initially at uniform temperature, T0 Energy balance requires

  5. Large value of Bi • Indicates that the conductive resistance controls • There is more capacity for heat to leave the surface by convection than to reach it by conduction Small value of Bi • Internal resistance is negligibly small • More capacity to transfer heat by conduction than by convection

  6. Example 1 (WWWR Page 266) • A long copper wire, 0.635cm in diameter, is exposed to an air stream at a temperature of 310K. After 30 s, the average temperature of the wire increased from 280K to 297K. Using this information, estimate the average surface conductance, h.

  7. Example 1

  8. Heating a Body Under Conditions of Negligible Surface Resistance

  9. IC BC(1) BC(2) x V/A = (WHL)/(2WH)=L/2 BC (1) -> C1=0 BC (2) -> l = np/L Fo = at/(L/2)2 IC -> Fourier expansion of Yo(x) …..> Equation (18-12) Engineering Mathematics: PDE

  10. Detailed Derivation for Equations 18-12, 18-13 Courtesy by all CN5 students, presented by Lim Zhi Hua, 2003-2004

  11. Detailed Derivation for Equations 18-12, 18-13 Courtesy by all CN5 students, presented by Lim Zhi Hua, 2003-2004

  12. Example 2

  13. Heating a Body with Finite Surface and Internal Resistance

  14. Heat Transfer to a Semi-Infinite Wall

  15. Temperature-Time Charts for Simple Geometric Shapes

  16. Example 3

  17. or Figure F.4

  18. Example 4

  19. WWWR 18-12; 18-13 WWWR 18-16 (a) T=Ts @ x =0 WWWR 18-20 (b) -k dT/dx = h (T-T∞) @ x =0 WWWR 18-21

  20. Courtesy contribution by ChBE Year Representative, 2006.

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