RURAL EXGIXEERING. 891 



" The heat economy of quadrui>le effect evaporators as found in practice 

 compared with a computation on ideal lines lay between 0.8 and 0.9. This 

 latter figure was found with well protected and the former with unprotected 

 or badly protected apparatus. 



"A vertical submerged tube apparatus with 5 lbs. gage i)ressure in cell 1 

 (227° F.) and not less than 2«>.5-in. vacuum in last cell (127° F.) should evapo- 

 rate not less than 9 lbs. water per square foot per hour, with juice entering at 

 212° F. and should evaporate 4.2 lbs. water per pound of steam. If these condi- 

 tions are not realized foul heating surfaces, too slow evacuation of condensed 

 waters or incondensible gases, may be looked for. 



"A horizontal tube film evaiwrator had a much greater rate of evaporation 

 than vertical submerged tube evaporators." 



The heat balance of a cane-sugar factory, N. Dekrr (I/aivaiiitn Sugar 

 Planters' /S7a., Agr. and Chcm. Bui. >iS {101.',), pp. 2/).— Investigations on tlie 

 heat value of bagasse and the steam generated by its combustion, the steam 

 required in evaporation in single and multiple effcx^t, and the heat represented 

 by work, are reported. The mean heating value of bagasse is taken as 8,100 

 B. T. U. per pound of dry bagasse, and the actual heat of combustion is taken 

 as the basis of calculation of the etficiency of bagasse as a fuel. 



Comparative tests of a water tube boiler and smoke tube tandem boilers 

 showed that on the average the smoke tube boilers evaporated 2.815, and the 

 water tube boilers 2.328 lbs. of water per pound of bagasse from and at 212° F. 

 " This gives a superiority In so far as regards steam per pound of fuel of 20 

 per cent ; this increased economy is to be attributed solely to the much greater 

 proportion of heating surface per pound of fuel burnt. . . . 



" The efficiency of combustion as evidenced by the percentage of CO2 in the 

 flue gases is very much the same and the superiority in economy found with 

 the tandem boiler is simply due to the greater reduction in the temperature of 

 the products of combustion due to the larger heating surface." 



A comparison of the relative efficiencies of heating surfaces as regards heat 

 transmission showed the water tube boiler to be 1.15 times as efficient as the 

 fire tube boiler. 



It is concluded that capital expended in ample heating surface in the cane 

 sugar industry will always be a profitable investment and that multiple crushed 

 bagasse is equal in fuel value to bagasse not so treated. Further data are given 

 showing the heat used by an entire plant. Heat balances constructed on the 

 basis of such data for two factories of high and average efficiency show that 

 under such circumstances the second factory might operate without extra fuel 

 while the first would have a great surplus for other uses. 



It is concluded " that the heat balance of a cane sugar factory will depend on 

 a multitude of factors so that an analysis is required of each individual factory. 

 The factors without the control of the factory executive are: (1) Fiber in cane, 

 controlling the steam available; (2) sugar in cane, controlling the amount of 

 evaporation to be done at single effect and at multiple effect. The factor under 

 the control of the factory executive is efficiency of the factory, including therein 

 heating surface in boilers and control of the combustion, protection of hot sur- 

 faces, sufficient heating surface in evaporators to obtain not less than 65° Brix 

 in sirup, and arrangement of plant to allow of the use of extra steam and of 

 multiple heating." 



Central station power for farmers, D. 11. Palmquist (-S'ci. Anicr., 109 {1913), 

 No. 22, pp. Jf05. 417, figs. 3). — This article gives " si>ocific data and infoiTuation " 

 as to the cost on farms of using electric power from central stations. 



