2. Simplified Analysis of Radiation Heat Transfer in A Furnace P M V Subbarao Professor Mechanical Engineering Department Empirical Testing for Cooling Capacity of Furnace Walls.

3. Models for RTE in gas radiation 2-Flux 4-Flux Multiflux DOM Moment Modified- Moment P N - Approx. Zone MCM Numerical (FD, FV) RTE Optically ThinSelf-absorbingOptically Thick Directional AveragingDifferential Approximation EnergyHybrid DTM Ray Tracing Radiation Element

4. Geometrical Simplification

5. Radiation heat transferred to furnace wall Radiation heat transfer  eff is the emissivity of flame and water wall system. Emissivity of PC flame S : Effective thickness of radiant (flame) layer. V is the volume of the gas and A is the enclosing surface area and p is the pressure of gases.

6. K is the coefficient of radiant absorption Volume fraction of RO 2 & H 2 O : r RO2 & r H2O c 1 : 1.0 for coal and 0.5 for wood c 2 : 0.1 for PC flame, 0.03 for Stoker flame.  h : Concentration of ash particles d h : diameter of ash particles : 13  m for PC & 20  m for stoker.

7. Thermal Efficiency Factor,  If clean water wall is a perfect black body all radiation falling on it will be absorbed. Fouling (  leads to drop in emissivity of the wall. Water walls consists of tubes which generate an angular coefficient, x. Angular coefficient varies with the location of water wall. Thermal efficiency factor is defined as the fraction of incident radiation absorbed by the tubes: The average thermal efficiency factor is calculated as

8. Effect of Angular Coefficient Heat Flux Steam Quality

9. 1: C > 1.4 d 2: C = 0.8 d 3: C = 0.5 d 4: C = 0 5: C < 0

10. Energy absorbed by the steam Final effect : T fl gets changed to Furnace gas Exit Temperature. Due to energy lost by hot gases. –Loss due to Environment –Energy absorbed by water walls Energy lost by hot gasses from flame to exit. Define

11. Heat absorbed =  (energy liberated – energy of gas at furnace exit).

12. Temperature Distribution (burner 1– 5)

13. Temperature Distribution (burner 1 – 4)

14. Combustion Geometry