142 



SCIENCE. 



[K S. Vol. XXII. No. 553. 



ance to those of us who are not engineers, 

 and, because of preferences in other direc- 

 tions, do not wish to become engineers, to 

 have a laboratory manual which, along with 

 coiirses in measurement, contains directions 

 for work which is on clearly and definitely 

 stated engineering problems. From our stand- 

 point what we need is to get our teaching in 

 part out of the confines of the class-room and 

 even of the laboratory and bring it more into 

 touch with the commercial application of the 

 work. The following outline, arranged to 

 supplement my laboratory course in heat, may 

 serve to indicate what it seems to me is wanted 

 in each branch of physics. If thei^e is a 

 laboratory guide published which includes 

 such plans, I should like to know of it. 



SUPPLEMENTARY WORK IN PHYSICS. II. HEAT. 



1. Coal. 



Plan an experiment to determine tlie amount 

 of heat generated in the combustion of a pound of 

 coal, and write out a report in full in the usual 

 form, leaving blank spaces for the insertion of the 

 data Avhen obtained. After consultation as to 

 the plan you may determine how many pounds 

 of water a pound of coal will raise one degree 

 J'ahr. when no heat is lost. 



Average data for comparison: Heat from the 

 •combustion of one pound of anthracite coal will 

 raise the temperature of 14,000 pounds of water 

 1° F. Heat from the combustion of one pound 

 of coke will raise the temperature of 14,000 

 pounds of water 1° F. Heat from the combustion 

 of one poimd of crude oil will raise the tempera- 

 ture of 19,000 pounds of water 1° F. Heat from 

 the combustion of one pound of gas will raise the 

 'temperature of 1,000 pounds of water 1° F. Heat 

 from the combustion of one pound of hard wood 

 will raise the temperature of 8,500 pounds of 

 water 1° F. Heat from the combustion of one 

 pound of soft pine will raise the temperature of 

 9,000 pounds of water 1° F. Heat from the com- 

 bustion of one pound of peat will raise the tem- 

 perature of 6,000-10,000 pounds of water 1° F. 

 There are no data on the kind of coal which we 

 have. 



2. Boiler. (Study of boiler at the college heat- 

 ing plant.) 



The engineer will tell how much the level of 

 water in the boiler has been lowered in one day 

 without return of water to the boiler, and how 

 much coal was actually used. 



How much would have been needed to evaporate 

 this water under the pressure of forty pounds 

 per square inch if no heat were lost? What is the 

 efficiency of the boiler? What horse power was 

 actually generated ? 



About ten square feet of heating surface are 

 needed per horse power. What is the rating of 

 the boiler? 



The ratio of water heating area to the area of 

 the grate is generally 20-25 to 1. W^hat is the 

 ratio in these boilers? 



What is the pressure of steam in one of the 

 boilers ? Determine with a thermometer the tem- 

 perature of the water in the boiler. How does 

 this temperature compare with the temperature 

 given in the curve of steam pressure? 

 2. The System' on Heating. 



Follow the steam pipes to the tunnels, deter- 

 mine the use of each pipe and see what the dif- 

 ferent valves control. Is any part of the system 

 not under complete control ? How is air re- 

 moved from the pipes? In what different ways 

 may -^vater be obtained and forced into the boilers ? 



What is the temperature of steam in the mains ? 

 What is the temperature of the water in the re- 

 turn pipes? How much heat was radiated from 

 the radiators and pipes ? ( For quantity of steam, 

 see data obtained on boilers.) 



Make the necessary measurements in the room 

 assigned you to determine the number of cubic 

 feet of space, the area of the radiating surface, 

 etc., and ascertain whether there is sufficient radi- 

 ating surface for the room. The following is one 

 of the tables used in such estimates : For each 

 200 cu. ft. of space allow 1 sq. ft. of radiating 

 surface. For each 20 sq. ft. of exposed wall allow 

 1 sq. ft. of radiating surface. For each 2 sq. ft. of 

 glass allow 1 sq. ft. of radiating surface. If the 

 building is poorly constructed twenty per cent, is 

 added to the radiating surface. (To save a large 

 part of the computing, see tables on page 6, Me- 

 chanics' Pocket Memorandum.) 



If a hot water heating system were used five 

 thirds as much radiating surface would be re- 

 quired. What is the exact ratio between the 

 heat given out in the pipes by a quantity of steam 

 at one and one half pounds pressure and the same 

 quantity of water at 150° F., both cooling down to 

 the temperature of the water in the return pipes? 

 What bearing does the curve of cooling which you 

 have drawn have on the selection of a ratio for 

 estimates ? 

 4. Engine (at electric light plant) . 



Explain how the valves control the steam ad- 



