85. The following general conclusions are deduced from the results of extensive experiments and tests of radiators: The various materials used for radiators do not show any considerable difference in emissive capacity under similar conditions of internal and external temperature.

## Table 11. Radiators-Vertical, Tube, Prime Surface

 Difference inTemperature.Degrees F°. Vertical Tubes, Massed. Vertical Tubes,Single Row. 40 Inches High.B. T. U. 24 InchesHigh. B. T. U. 40 Inches High.B. T. U. 12 Inches High.B. T. U. 50 1.29 1.54 1.46 2.01 60 1.33 1.58 1.50 2.06 70 1.36 1.62 1.54 2.12 80 1.39 1.66 1.58 2.17 90 1.41 1.70 1.62 2.22 100 1.46 1.74 1.65 2.27 110 1.49 1.78 1.69 2.32 120 1.52 1.82 1.73 2.38 130 1.56 1.86 1.77 2.43 140 1.59 1.90 1.81 2.48 150 1.63 1.94 1.85 2.53 160 1.66 1.98 1.88 2.59 170 1.69 2.02 1.92 2.64 180 1.73 2.06 1.96 2.70 190 1.76 2.10 2.00 2.75 200 1.80 2.14 2.03 2.80 210 1.83 2.18 2.07 2.85 220 1.86 2.22 2.11 2.90 230 1.90 2.27 2.15 2.96 240 1.93 2.31 2.19 3.01 250 1.97 2.35 2.23 3.06

The rate of emission is practically the same for hot water or steam, for equal differences in temperature.

The rate of emission is not affected by the internal volume of the radiator tubes, provided the sectional area is large enough to afford good internal circulation.

In still air, radiators having but one row of tubes are more effective than those having two or more rows.

With equal surfaces, in still air, low radiators are more effective than tall ones, and horizontal tubes are more effective than vertical ones.

86. Table 11 shows the actual emissive capacity of several varieties of direct radiators working in still air, as determined by experiment. The first column gives the difference in temperature, and the remaining columns, the total emission of heat per hour, in still air, per square foot of external surface, per degree difference in temperature.