1. Radiation Exchange EGR 4345 Heat Transfer

2. Blackbody Radiation Exchange

3. Rate at which radiation leaves surface i and is intercepted by surface j For a black surface, J i = E bi Net radiative exchange

4. Blackbody Radiation Exchange Therefore Or Net radiation transfer from any surface in an enclosure of black surfaces

5. Net Radiation Exchange at a Surface in an Enclosure

6. Assumptions – Isothermal surfaces, T i is known – Uniform radiosity – Uniform irradiation – Opaque – Diffuse – Gray surface – Medium in enclosure is nonparticipating

7. Net Radiation Exchange at a Surface in an Enclosure Determine the net rate at which radiation leaves surface i Where In terms of emissive power and absorbed radiation

8. Net Radiation Exchange at a Surface in an Enclosure For an opaque, diffuse, gray surface Solve for G i and substitute into q i Or Driving Potential Surface Radiative Resistance

9. Net Radiation Exchange Between Surfaces in an Enclosure

10. Total rate at which radiation reaches surface i from all surfaces, including i Reciprocity Substituting in for G i

11. Net Radiation Exchange Between Surfaces in an Enclosure Summation rule Therefore Or Use matrix operations to solve Space or Geometric Resistance

12. Net Radiation Exchange in a Two-Surface Enclosure Two diffuse, gray surfaces that form an enclosure

13. Net Radiation Exchange in a Two-Surface Enclosure General Equation Special equations

14. Radiation Shields General Equation Low emissivity increase resistance

15. Reradiating Surface Zero net radiation, q i = 0

16. Reradiating Surface