2. Development of Simplified Model for Furnace Cooling Capacity P M V Subbarao Professor Mechanical Engineering Department Empirical Testing for Cooling Capacity of Furnace Walls.

3. System of Equations for Radiative Heat Transfer

4. Define non dimensional temperature using T ad

5. Based on experimental data, it is found that

6. Experimental work by Gurvich & Blokh generated a relation as:

9. Cross-sectional distribution of Temperature

10. Furnace Exit Gas Temperature The temperature of products of combustion at the exit of the furnace is called FEGT. Defines the ratio of furnace heat absorption to outside heat absorption. High FEGT – Compact furnace & Large secondary section FEGT < Ash Deformation Temperature. Generally FEGT = Ash Softening Temperature – 100. FEGT is a Right Measure of Steam Generator Health ! A Healthy SG will Always Perform Better !!! A SG Always Healthy will Perform Better !

11. Cause – Effect Analysis of A Furnace Combustion is a Primary cause Steam Generation is an Ultimate effect Heat transfer is a mediation. Combustion generates flame & Thermal Energy in side a furnace volume and finally produces high temperature gases. These high temperature gases will initiate Radiation and convection heat transfer. Heat Transfer carries thermal energy to furnace wall. Furnace wall transfers this heat to steam tubes. Steam tubes transfers the same to steam by means of Heat Conduction. A relatively cold exhaust leaves the furnace. This is final effect at the exit of the furnace!!!!!!!

12. Phenomenological Model Hot Flue Gas Thermal Structure SH Steam Convection & Radiation HT Convection HT Drop in Enthalpy of Flue Gas Rise in Enthalpy of Steam Mechanism of Heat Transfer Source/Supply Thermal StructureSink /Demand

13. Temperature Field Coefficient Temperature field coefficient accounts for the temperature distribution in the furnace. It is a function of relative level of the burners and on the type of fuels burnt. The expression of M is given as: Z r is the relative position of highest temperature zone wrt to furnace bottom.  Z is a correction factor for tilt of burners. C 1 &C 2 are constants depend on fuel quality

14. Multiple Burner System

15. FuelC1C1 C2C2 Gas or Oil0.540.2 HV coal0.590.5 LV0.560.5 High ash coal0.540.5

16. Distribution of Heat Flux Average Heat flux can be calculated using: As the temperature and emissivity of flame is not uniform in the furnace volume, the local heat flux is not uniform. Actual local wall temperature depends on the value of local heat flux. Special experiments are carried out to find the heat flux distribution on water wall.