Design Guidelines for High Performance Industrial Furnaces - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 249

irst Zone
Combustion Amount

F Second Zone

Combustion Amount

kW(Mcal/h) KW(Mcal/h)

Condition No. 1 Pair No. 2 Pair No. 3 Pair No. 4 Pair Heating Efficiency

Doubled pitch 1 0 1175(1010) 0 1163(1000) 0.598

Doubled pitch 2 0 1420(1220) 0 1420(1220) 0.590

Usual pitch 698(600) 698(600) 698(600) 698(600) 0.652

1500 1500

1400 1400

1300 1300

0 2 4 0 2 4

Distance in furnace with direction, m Distance in furnace with direction, m

F IGURE 5.3 Changes of g as temperature profiles with burner pitches.

test sho w that a temperature variation of 300˚C was caused between the first zone

and the second zone and the heating efficiency increased by 4% as shown in Figure
5.4 , with the temperature deviation of the slab in the thickness direction increased
from 65 to 90

C. For industrial heating applications, the quality of products is very
important. Therefore, the balance between efficiency and uniform-heating condition
must be taken into consideration in the design.

˚

5.1.3.3 Analytical Study of the Effect of a Partition Wall

T o identify the effect of a partition wall, studies were made on (1) the measurement

of wind velocity using air at normal temperature, (2) fluid analysis using air at
normal temperature, (3) measurement of temperature distribution associated with
combustion, (4) analysis of thermal fluid associated with combustion, and (5) opti-
mization of the length of the intermediate partition wall.
The measurement of the wind velocity using air at normal temperature was
carried out using the testing setup shown in Figure 5.5 , and the length of intermediate
wall was varied to four lengths of 0, 1.3, 2.2, and 3 m (or expressed in the percentages
of effective furnace length, 0, 43, 73, and 100%). Fluid analyses were performed
using a total analysis model of reheating furnaces and with the mesh having the
number of approximately 38,000 as shown in Figure 5.6 . The results of these
measurements and analyses are shown in Figures 5.7 and 5.8 , respectively. The
results from the actual measurements and the analyses are similar. Regarding the