54 kellerman: suggestions for frost protection 



of water which might be warmed at a central station; (2) the 

 suspension of pans holding small quantities of water above each 

 of the fire pots now in use; and (3) the pumping, thru a permanent 

 system of pipes, of steam generated at a central station and mixed 

 wdth large quantities of air to prevent condensation in the pipes. 



While there would be a considerable water economy in the 

 use of steam by either the second or third methods, the feasi- 

 bility of water heating will be sufficiently well illustrated by 

 describing with approximate figures the theoretical possibilities 

 of only the first method. 



If we neglect for the moment the effect of evaporation and the 

 presence of water vapor in the air, the heat liberated by 1 liter 

 of water in cooling from 90° to 0° C. is, in round numbers, cap- 

 able of raising the temperature of 296,100 liters of air from 

 — 1° to 0°C. To raise the temperature of a column of air 3.29 

 meters high and covering 1 hectare from —1° to 0° should there- 

 fore take approximately 111 liters of water at 90°. Assuming 

 that the humidity of such a column of air was 80 per cent, and 

 that at a temperature of —1° it would be saturated by 155 liters 

 of water, the evaporation of the 31 liters of water required for 

 saturation would absorb heat equivalent to that given off in 

 cooling 184 liters from 90° to 0. The very small quantity of 

 hot water, about 1 liter, required to raise the temperature of 

 this aqueous vapor from —1° to 0° is almost negligible. For the 

 rise of each degree, however, approximately 1.1 liters must go to 

 saturate the column of air under discussion, and in evaporating 

 this quantity of water heat is absorbed equivalent to that given 

 off in lowering 7.4 liters of water from 90° to 0°. The total 

 quantity of water at 90° which must be thoroly distributed to 

 cause the initial rise from —1° to 0° of the air column 3.29 meters 

 high, covering 1 hectare, is therefore 111 + 1 + 208.9 + 7.4 = 

 328.3 liters; the subsequent rise from 0° to 1° would require 

 111 +1 +1.1 +7.4 = 120.5 liters of water at 90°; the increase 

 from 1° to 2° would require 111 + 1 + 2.5 + 7.4 = 121.9 liters of 

 water at 90°; and the increase from 2° to 3° would require 111 + 

 1 + 3.9 + 7.4 = 123.3 liters at 90°. 



For a body of air 26 feet deep, covering 1 acre, 86.7 gallons of 



