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March, 1930] WATER COOLING OF INCANDESCENT LAMPS 341
Fig. 5 shows the effect of rate of flow of the cooling water on the temperature of the water cell, and also on the ratio of watts dissipated in the circulating water to watts input into the lamp.
It will be noticed that it is of little utility to increase the flow of water above 1500 cc. per minute. At this point, 75 per cent of the watts are dissipated in the circulating water and the temperature of the water cell is 44°C. At a flow of 3500 cc. per minute, the watts dissipated increase only 3 per cent and the temperature of the cell falls only 2 degrees.
The effect of change of wattage in the same lamp on the temperature of the water cell is plotted in Fig. 6. This curve indicates that it may be possible to operate a lamp of 1700 watts in a 2.5 inch tubular bulb.
SUMMARY
An experimental device is described for absorbing and removing heat from incandescent lamps by means of a water cell surrounding the lamp. Ordinary tap water flows through a cooling coil immersed in the cell and dissipates 75 per cent of the total watts input for a 1500 watt, 115 volt lamp. The loss of light due to the water cell is 5 to 7 per cent. These figures give some idea of the result obtained by water cooling incandescent lamps, but an actual personal exposure to both the regular and experimental lamps affords the only satisfactory means of comparison.
DISCUSSION
MR. EGELER: The problem of taking care of the heat from the light source is not one which has given concern with the ordinary lighting intensities, but in motion picture projection it has been a subject of discussion previously. A number of years ago some publicity was given to the removal of heat from the light beam in connection with motion pictures of medical work where the effect of this non-luminous radiation was destructive to the specimens. For many years, of course, we have used water cells in slide projectors, and in motion picture photography the problem has come up with the changes in operating practice. With the coming of sound pictures most of the old studios, modified to sound practice, had inadequate ventilation; in the new studio design conditions are made much better by providing adequate ventilation without the noise of ventilating fans. There are several methods of attacking this problem: First, the scheme referred to, taking out the heat with adequate circulation of air. The second way would be to take the heat out of the light beam by putting an absorbing medium, such as glass, on the front of the lighting units, so that the radiation directed toward the actors could be filtered and the heat of the unit removed. The remainder of the radiation would be taken care of by