162 THE APPLICATION OF SMALL STEAM TURBINES 



Direct connected. Geared. 



1. Horse-power 347 340 



2. Efficiency ratio 0.25 .47 



3. R. P. M 1350 ' 3620 



4. Ideal water rate (250 — 10 lbs.) 14-55 14-55 



5. Actual water rate (lbs. per B. H. P. hr.) . . 58.2 31 



6. Total steam per hr. = (i) X (5) 20195.4 10540 



7. Total heat per lb. at 250 lbs. pressure 1 199.2 1 199.2 



8. Heat in exhaust with 100% efficiency. . . . 1024.4 1024.4 



9. Available heat = (7) — (8) 174.8 174.8 



10. Actual heat used = (9) X (2) 43-700 82.156 



1 1 . Heat required per lb. to be generated to run 



circulating pumps = (7) — (Head of 



liquid of exhaust) 99i'2 991-2 



12. Total heat requisite to run circulating 



pumps = (6) X (11) 20017680.48 10447248.0 



13. Total heat returned to system per lb. steam 



= (7) — ( 10) + 208.6 946.9 908.444 



14. Total heat returned to heater = (6) X 



(13) 19123024.26 9575590-0 



15. Total heat chargeable to circulating pumps 



= (13) — (14) 894656.22 871658.0 



16. Same as (15) for two turbines = (15) X 



2 1789312.44 1743316.0 



17. Total steam required for remaining appa- 



ratus (lbs. per hr.) 600000 600000 



18. Total heat required for remaining appa- 



ratus ^ (17) X (7) — 70 . . 677520000.0 677520000.0 



19. Saving by using gears (16 Col. i) — (16 



Col. 2) 45996.44 



20. Total heat for all purposes := (18) -f (16) 679309312.44 679263316.0 



21. Per cent saving = ) ^v, . — ^ .00677 



(20 Col. I ) 



To improve the unit efficiency of various parts of the apparatus, gears are 

 being resorted to. 



Regarding the advantage of gear-driven auxiliaries, it is true the unit ef- 

 ficiency is improved, and granted that remarkable developments have been made in 

 recent years towards the production of a satisfactory gear, it is nevertheless a fact 

 that the gear-box considered as a unit is another piece of apparatus to take care of, 

 and the writers' experience has been that this piece of apparatus is still far from per- 

 fect. Of course there are good gears, but the successful operation apparently de- 

 pends so much on perfect workmanship that there seems to exist a big element of 



