FLUE HEATEKS. 

 TABLE No. 9. Tests with Flue Heaters. 



57 



The average results of these four trials show that the use of 

 a flue heater having 44 per cent, as much heating surface as 

 that of the boiler, applied where the temperature of the escap- 

 ing gases is 394 degrees and the initial temperature of the 

 feed-water 92 degrees, increases the evaporation per pound of 

 coal 9.9 per cent. The important question which arises is, 

 does this amount of gain pay for the addition to the plant 

 involved by the employment of this apparatus ? Let us refer 

 the matter to a plant of 1,000 horse-power, and use for a cal- 

 culation the cost of Cumberland coal required for a day's run 

 of 10 hours, given in Table No. 8, which is $63.38. The 

 saving produced by the flue heater is $5.71 per day, and this 

 amount represents for a year of 308 days a total saving of 

 $1,759. The cost of a heater with complete equipment of 

 setting and appurtenances, having a surface of say 5,000 

 square feet, which corresponds to the instances referred to, is 

 $7,000 to $8,000. The economy secured is, therefore, suffici- 

 ent to pay a yearly return of from 20 per cent, to 25 percent, 

 on the additional investment, which is certainly of some 

 importance. 



It must be borne in mind that this result applies only to a 

 case where the temperature of the water supplied to the heater 

 is comparatively low, corresponding to that of the overflow 

 water of a condensing engine. On the. other hand, it is a case 



