180 



"The civil engineer and architect's journal. 



[Ju.VK 



uianiifartures, we are unalile to decide; fortunately tlie difference 

 is quite inconsideralile, and is not regarded as deserving of further 

 consideration. 



So soon as the tenijierature of the Condenser was reduced to a 

 degree that rendered an examination of it practical>le, one of its 

 Leads was removed in our presence, and tlie tuhes, w lien examined, 

 were entirely free from any deposit or incrustation ujion their sur- 

 faces, and the opinion is entertained, that at a temperature of feed 

 water commensurate with economy of fuel, any difficulty from the 

 deposit of oleaginous matter in this instrument is not to be appre- 

 hended. 



Regarding the particular performances of the Condenser and 

 Evaporator, it appeared that Capt. Ericsson had relied too con- 

 fidently on a general current of the cold water through the former 

 instrument, whereas the current was quite partial, being but 

 directly through its narrowest part, the sides of it : hence, the 

 upper portion of it was almost inoperative — this feature was clearly 

 developed by the application of a hand along the surface — while 

 the effect of it was apparent in the moderate condensation indi- 

 cated by an attached mercurial gauge. 



Of the Evaporator, its capacity was clearly shown, in the facility 

 with wliidi the level of the water in the boiler could he raised 

 through the space between two gauge-cocks, and by a resort to its 

 operation not being necessary for more than one-tenth of the 

 time. 



Immediately after the close of this trial, measures were taken to 

 effect a diffused operation of the cold water, and as diaphragms 

 could not be introtluced between the tubes to alter the current of 

 the water, without incurring an impracticable delay, the expedient 

 of causing the steam to circulate through the tubes was resorted 

 to, and was effected by the application of diaphragms in the open 

 space at each end of the tubes. Upon the completion of this, a 

 further trial was had on Friday, the 1st inst., when several obser- 

 vations furnished the following : — 



Pressure of steam, 50 pounds mercurial gauge. 



Revolutions, 4 7 per minute. 



VacuuEH, 20*5 inches. 



Temperature of feed water, 150° Fahrenheit. 

 Temperature of sea water, 62° „ 



Compared with the ordinary method of condensation, the value 

 of the method observed is determined by an investigation and con- 

 sideration of the following points, viz. : Evaporation, Pressures, 

 Consumption of Fuel, Safety and Duration of the Boiler. 

 1. — Evaporation. Ordinary Method. 

 Temperature of Feed Water, 100° Fahrenheit. 

 Tf'niperature of sensible and latent heats of steam, 1192° 

 •Deduct temperature of feed water, 100° 



Heat to be added, .. .. 1092° 



New Method. 

 Temperature of Feed Water, 150° Fatirenhfit , 

 Temperature of sensible and latent lieats .. 1192° 



Deduct temperature uf feed water .. 150° 



10-12° 



Heat to he added 



1012 -954 



Then — = which represents a earn in tUe evaporating temperature 



1092 1-00 r t> 1 



in the new method rif 4 "56 per cent. 



2. — I'bessurBs. Ordinary Method. 



Pressure of steam — mercurial gauge . . 50 th. 



Vacuum, 28 inches .. .. =1,3 7 lb. 



Cut off at threeeiphths of the strolie. 

 Effective prt,*,-.!,ure on the piston 



New Method. 

 Pressure of steam 

 Vacuum, 205 inches 



C3-7 lb. 



= 47 tt). 



50 Ik. 

 = 1 lb. 



00 tb. 



Effective pressure on the piston .. 445 lb. 



■17 1-05 , . , , . 



Then = which represents a Iiiss in pressure bv the new mslhod 



44'5 rOO 



of 5 per cent. 



3. — Consumption of Fuei,. Ordinary Method. 

 Ill the Gulf of .Mexico and between the Tropif;s, it is nP'essary to blc«v- 

 off. when a hydrometer constructed similar to tbe one alreaily referreil to 

 indicates -jS,; in the Northern and Sonthern /tlantic and Pacific oceans, when 

 ' ^ 2- + 2 5 



it indicates -" . Hence • 



= 2 25 the average point for blowingoff. 



.75 

 As the average degree of saturation of feed water is ■^., ; the quantity of 



water blown off compared to that fed to a boiler is as '75 to 2-25, which is 

 in the proportion of 1 to 3. 



Temperature of tlie water ilown off at the pressure ami degree of satura- 

 tion given . . . . . . . . 29u° 



Deduct temper.iture of ferd water .. 100" 



Temperature lost by hlowingnff .. 190° 



As tbe heat to he added for tbe purpose of evaporation is 1092^ — 

 1092 X 3 — 1, the proportion of f^erl water evaporated, =2184° 



And 190 X 3 — 2 tbe propoitiun of feed water blown off 190" 



The heat absorbed, is .. 2^74° 



_, 190 -08 



Then — ,-^ which represents the loss of heat bv blowing off in tbe 



2o/4 1*00 



ordinary method of 8 per cent. 



Summary or Results. 

 Gain by Evaporation . . . . . . 4 56 per cent. 



Ditto by Consumption of fuel . . . . 8'6o „ 



Loss by Pressure 



12-56 

 5 00 



Total .. .. 7-5fi 



Which is a saving in the expenditure of heat, affording a like 

 economy in the consumption of fuel and altogether independent of 

 the loss of heat, by the presence of scale in a boiler, when salt 

 water is used, and from leaks incurred by the oxidizing effects of 

 salt water. 



With the Ordinary Method, the level of the water in a boiler is 

 constantly varying from one or both of the following causes, viz. : 

 the quantity of the water blown off, or the particular extent of 

 opening of the feed-valve ; while the effective operation of the 

 feed-pump and neglect of the blow-off valve, involves the burning, 

 or an explosion of the boiler. 



\V^itIi the New JSIethnd, these operations are set aside : thus, 

 blowing off is unnecessary, and the supply to the boiler being first 

 obtained from it, the transit being immediate and the communica- 

 tion incapable of restriction (for if the condensed water was not 

 taken off by the feed pump, the condenser would choke and become 

 inoperative), there can be no decrease in the level of tbe water, 

 other than that arising from leaks of water and steam. Further^ 

 the use of fresh water in a boiler vn ill extend the term of its dura- 

 tion from three and five years to seven and nine. 



With a further modification of the condenser, establishing a 

 more diffused current of the cold water, it is evident that a full 

 vacuum may he obtained, as the practicability of attaining this end 

 by external condensation has long since been developed, and with 

 a less proportion of radiating surface than is exposed in the instru- 

 ment referred to. P'rom the analysis however here given regarding 

 pressures and temperatures, it would appear that a full vacuum, 

 with corresponding reduction of the temperature of the feed water 

 is not authorised ; and as such departure from the hitherto prac- 

 tice, furnishes the temperature necessary to prevent any oleaginous 

 deposit upon the surface of the tubes of the condenser, practice 

 and utility are in desired harmony. 



A very effective and economical element in steam navigation 

 arises with the operation of this new method, from the absence of 

 scale in the boiler, the presence of which is unavoidable where salt 

 water is used, and to avoid the formation of it as far as practicable, 

 other than a low temperature and corresponding pressure are pre- 

 cluded by the waste of fuel and injury to the boiler consequent 

 upon the existence of this scale, acting as a new conductor of tlie 

 heat to the water — whereas, with the use of fresh water, higher 

 pressures can be worked and economy of fuel attained in an in- 

 creased expansion of the steam. 



Reviewing the facts herein presented, we are of the opinion that 

 the operation of the apparatus of t'aptain Ericsson, as far as de- 

 veloped, was eminently successful, and that, with the modification 

 of the condenser suggested, a higher degree of vacuum can bo 

 readily obtained. In view of the very great importance of the 

 successful introduction of this metliod of condensation in the mer- 

 chant and naval services, we recommend to your consideration the 

 propriety of sending the Legnr,' on a distant cruise, for the pur- 

 pose of developing the advantages of the apparatus by continued 

 and extended use. 



Charles H. Haswei.l, 



Eiigiuter-in-Chiet\ U. S. N. 



New rwk,Oct. 31, IStT. " &c. &c. &c. 



