Table 12. Flue Radiators-Natural. Draft

Surfaces.

Heat Emitted per

Square Foot, per Hour, per Degree

Difference.

Total Heat Emitted per Hour, per Degree Difference.

Extended. Square Feet.

Square Feet. Plain.

Extended. B. T. U.

Plain. B. T. U.

Extended. B. T. U.

Plain. B. T. U.

A

B

C

D

E

F

57.80

40.40

1.65

1.97

95.37

79.58

6.40

4.24

2.05

2.39

13.12

10.13

63.10

41.20

1.39

1.85

87.81

76.22

7.18

4.50

1.90

2.24

13.64

10.08

87. The comparative efficiency of flue radiators and plain surface radiators of the same size may be seen in the experimental results shown in Table 12. The data in columns A, C, and E refer to the radiators in their original condition, having the usual ribs, etc., as shown in Fig. 25, while those in columns B, D, and F refer to the same radiators having all of the ribs and " extensions " removed.

It will be observed that, while the rate of emission from the plain surfaces is higher than that from the extended surfaces, yet the total emission is less. This result is due to the great difference in area of the actual emitting surfaces.

88. The average rate of emission of heat from ordinary indirect radiators, which are enclosed in a box and deliver warm air to rooms above through a vertical flue, is shown in Tables 13 and 14:

Table 13. Indirect Radiators-Natukal Draft, Extended Surfaces

Height of Flue. Feet.

Velocity of Air. Feet per Second.

Emission of Heat per

Square Foot.per Hour, per Degree Difference.

B. T. U.

5

2.90

1.70

10

4.10

2.00

15

5.00

2.22

20

5.70

2.38

25

6.30

2.52

30

6.70

2.60

35

7.14

2.67

40

7.50

2.72

45

7.90

2.76

50

8.20

2.80

89. The rate of emission of heat from radiators of the general style shown in Fig. 34, which are specially designed for use with forced blast and are composed mainly of steel or wrought-iron pipe, is shown in the following table: