دیگ بخار و تاسیسات - HEAT TRANSFER IN THE RADIANT SECTION (part3)

HEAT TRANSFER IN THE RADIANT SECTION OF PETROLEUM HEATERS (part2): 1 - 2 - 3 - 4

ACKNOWLEDGMENT

The authors gratefully acknowledge the helpful suggestions offered during the course of the investigation by Mr. J. H. Rickerman.

APPENDIX
STANDARD FUEL COMPOSITION
STANDARD CRACKED GAS FUEL

Component		Mol PerCent
CH₄	...................................	37.0
C₂H₄	...................................	4.0
C₂H₆	...................................	22.0
C₃H₆	...................................	8.0
C₃H₈	...................................	23.0
C₄H₁₀	...................................	6.0
		____
		100.0

Lower heating value per lb. at 60° F. 20,557 B.t.u. (Higher heating value 22,400 B.t.u.)
Specific gravity relative to air, 1.06
Specific volume at 60° F. and 14.7 lb./sq.in. 0.0807 lb./ft.³
Combustion calculations are based on air at 60° F. and 50% relative humidity.

OIL FUEL

Component		Wt. PerCent
C	...................................	85.0
H₂	...................................	12.0
S	...................................	1.5
O₂	...................................	0.7
N₂	...................................	0.8
		____
		100.0

Lower heating value per lb. at 60° F. 17,130 B.t.u.
Steam for atomization, 0.3 lb./lb. fuel oil
Air at 60° F. and 50% relative humidity.

TEST DATA REQUIRED FOR DETERMINATION OF HEAT ABSORBED
BY OIL IN RADIANT SECTION

A. Quantities:

1. Fuel.

2. Oil through furnace.

3. Steam used for atomization, if any.

B. Temperatures:

1. Oil to and from various sections of furnace.

2. Flue gas from radiant section, determined by high velocity couple traverse, reading being taken about every two feet across furnace.

3. Flue gas from convection section or after bank of convection tubes through which combustion gases first pass, determined by high velocity couple traverse.

4. Air, both atmospheric and preheated, if any.

5. Fuel.

6. Surface of furnace for estimation of radiant losses.

7. Steam used for atomization, if any.

C. Analysis:

1. Fuel, heating value and proximate analysis.

2. Flue gas from radiant section by Orsat analysis of samples drawn through water-cooled sampling tube at intervals comparable to those used in temperature measurements.

3. Flue gas from same convection section section bank after which temperature (3) was measured, sample taken and analized as above.

D. Humidity of Atmospheric Air.

METHOD OF CALCULATION

Due to the fact that in petroleum heaters it is often difficult to determine accurately the heat absorbed by the oil in the radiant section from the oil side because of unknown heat of reaction, vaporization, etc., it is essential in most cases to obtain this figure by heat balance from the flue gas side, determining also by heat balance, as mentioned in the paper, any direct radiation from the combustion box to the convection section. Thus, the balance may be shown as follows:

Heat Input:
	1.	Heat of combustion of fuel.
	2.	Heat in air used for combustion.
	3.	Heat in steam used for atomization, if any.
	4.	Heat in recirculated flue gases, if any.

		Heat Output:
	1.	Heat in flue gases leaving radiant section.
	2.	Heat to oil in radiant section (determined by difference).
	3.	Heat to external losses.
	4.	Heat radiated from combustion box to convection section (determined by heat balance on part or all of convection section).

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