56 



Professor W. A. Bone 



[Feb. 2; 



mental unit as an evaporator, we proceeded to construct onr first 

 experimental boiler, made up of ten tubes, each 3 ft. long and 3 in. 

 in diameter, fixed horizontally in a cylindrical steel shell capable of 

 withstanding a pressure of over 200 lb. per square inch. This boiler 

 is shown diagrammatically in Fig. 10 (section showing three tubes 

 only), whilst Fig. 11 is a photograph of it (back view showing feed 

 water heater). The gaseous mixture was forced through the tubes 

 under pressure from a special feeding chamber attachiid to the front 

 plate of the boiler ; tlie products of combustion, after leaving the 

 boiler, passed through a small feed-water heater containing nine 

 tubes, each 1 ft. long and 3 in. in diameter, filled with granular 

 material to facilitate the exchange of heat. 



This combination of boiler and feed-water heater proved pheno- 

 menally successful in every way ; in a trial run at Leeds on December 8, 

 1910, with coal gas of net calorific value 562 B.Th.Us. per cubic foot 

 at N.T.P., and evaporating at the rate of 21 ' 6 lb. of water from and 

 at 212° F. per sq. ft. of heating surface per hour, the ratio of the 

 heat utilized to the net heat developed in the tubes was 0-943. But 

 this remarkable result was eclipsed in another independent trial 

 carried out by German Engineers in London on January 8, 1913, when 

 with coal gas of net calorific value 510 B.Th.Us. per cubic foot at 

 N.T.P., and evaporating at the enormously high rate of 33 '9 lb. 

 from and at 212° F. per square foot of heating surface, the ratio of 

 the heat utilized to the net heat developed by combustion Avas 0*933. 

 The details of these tests are shown below : — 



Dec. 8, I Jan. 8, 

 1910 1913 



1. Net cal. value of gas : B. Th. Us. per cub. ft at 



N.T.P 



2. Rate of evaporation : Lbs. of v^ater per sq. ft. 



heating surface per hour (from and at 212^ Fahr.) 



3. Pressure of gaseous mixture entering the tubes : 



Inches W.G 



4. Pressure of products entering the feed water heater : 



Inches W.G ... 



5. Steam gauge pressure : Lbs. above atmospheric 



6. Boiling point of the v^ater : Fahr. Degrees 



7. Temperature products leaving boiler : Fahr. Degrees 



8. Temperature products leaving feed water heater : 



Fahr. Degrees 



9. Net heat supplied to the boiler per hour : B. Th. Us. 

 10. Net heat transmitted per hour : B. Th. Us 



562 



21-6 



17-3 



2-0 

 100 



838^ 

 446° 



510 



38 -y 



40-9 



5-14 

 108 

 840° 

 534° 



! 



208° i 289° 

 559,800 I 728,383 

 527,800 i 680,000 



Efficiency Ratio .. 



0-943 



0-983 



