Trans. N. V. Ac. Sci. 68 Dec. 19, 



If the process be continuous, and the proper amount of air be ad- 

 mitted and removed every hour or minute, the only other requirements 

 are that the entering- air shall be pure, that it shall be properly warmed 

 in cold weather, either before it enters the room or by the mixture and 

 diffusion of wa*-!/! and cold air in the room; and that the introduction 

 and removal ot air shall take place by genile or inappreciable currents 

 in such a manuer that the pure air may be thoroughly diffused through- 

 out the room before it is removed. 



These simple rules are easily sta'ed and comprehended. It is also 

 well undeistood that to produce a movement ot air requires force in 

 proportion to the mass moved and the velocity imparted to it. 



The problems which arise in ventilation consist mamly in determining 

 the position, arrangement and sizes of the passages through which the 

 air enters and leives, and the proper adaptation of these passages to 

 the forces which produce the movement. 



On the correct soluti n of these problems, too often misapplied or 

 misunderstood, successful ventilation depends. 



The various modes of producing the movement of air for ventilation 

 are : 



First. — Ventilating chimneys or flues in which the movement is 

 caused by the difference in weight between the heated air in the flue 

 and the cool-r air outside. This requires that the air before entering 

 the flue shall be warmed, and the heat necessary may be that due to 

 the heat of the room when fires are necessary for warmth ; or the heat 

 may be imparted by stoves in the base of the flues, by gas jets, or by 

 steam-heated pipes. 



Second. — The movement may be produced by fans or blowers or by 

 steam jets the latter being seldom applied. 



The object of this paper is to investigate the laws which govern the 

 ventilation when the air is heated at the base of the flues by steam 

 pipes, the air in its passage to the flue receiving heat by its contact with 

 the exterior surface of the pipes. As far as I am informed these laws 

 have not heretofore been developed, and, as this system is a very 

 simple one, capable of very extended applications, it is hoped that the 

 following analysis may at least lead to a full discussion of the subject : 



Let it be supposed that the air in a room is to be renewed at the 

 rate of (W) lbs per second. Suppose also that it is to be rejected 

 through a flue whose cross-section in square feet is (A), and height 

 in feet (H). And that it is to be heated by steam coils whose aggregate 

 exterior surface in square feet is (S) 



The following notations will be used : 



W. Weight of air removed per second (lbs). 



H. Height of flue in feet. 



