652 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



in which a series of combustion tubes are lixed. By means of such 

 an apparatus, lead (or other fusible metals or alloys) may be melted 

 not only very rapidly, but with extraordinary efficiency. The follow- 

 ing is the result of a test carried out at the experimental station with 

 a single-tube apparatus: 



Lead-melting test. 



Degrees C. Degrees i". 



Temperature of metal charged 



Temperatm-e of metal tapped 



Temperature of gases leavmg apparatus 



15 

 372 

 500 



60 

 682 

 932 



Lead melted per hour= 1,176 pounds. 



Heat required per hour to raise metal from 15° C. to 372° C.= 1,176X32.67=38,420 B. t. u. 



Gas burnt per hour= 100 cu. ft. at N. T. P. 



Net calorific value of gas=559 B. t. u. per cu. ft. at normal temperature and pressure. 



"65.900 



The conditions were so arranged that the mean temperature of the 

 molten metal in the apparatus was 372° C. throughout the test. Lead 

 ingots, each weighing about 30 pounds, were added at intervals of 

 1.5 minutes, and the molten metal displaced Avas simultaneously run 

 off into molds. Great care was taken to keep the bath thoroughly 

 molten, and at a temperature within a few degrees of the mean 

 value. Burning gas of net calorific value of 559 British thermal 

 units per cubic foot, at the rate of 100 cubic feet per hour, it was 

 found possible to raise the temperature of 1,176 pounds of lead per 

 hour from 15° to 372° C. ; the temperature of the products of combus- 

 tion leaving the tube being constant at 500° C., or only 128° above 

 the temperature of the molten metal. Using the latest determination 

 by Spring of the specific heat of lead at temperatures up to and 

 albove its melting point, and ajdopting the usually accepted value for 

 the latent heat of fusion of lead, Prof. Bone estimates that at least 70 

 j)er cent of the heat developed was utilized. My observations of 

 this type of heating apparatus, in comparison with externally heated 

 melting pots, show a great difference in fuel consumption in favor of 

 internal heating. 



Many other applications of flameless combustion are undergoing 

 exhaustive investigation by Prof. Bone and his able colleague, C. D. 

 McCourt, and in the near future we may look for further interesting 

 developments within the many departments of the field of combus- 

 tion without flame. 



