ORCHARD HEATING 13 



sumption would be very close to the truth for the rise in tem- 

 perature is small the results show that it required 14 watts 

 per square foot to raise the temperature IQ Fahrenheit. 



With the same amount of power applied again, viz- 40 K. W. 

 (50 horse power) to this inclosure, with the wind blowing ten 

 miles per hour, 18.5 Ibs. of carbon dioxide (i) were liberated in 

 about half an hour and the mean temperature inside was but 

 2.8o F. above that outside and then again on another occasion, 

 '30 Ibs. of carbon dioxide were liberated in 50 minutes with the 

 same amount of power developed and with no wind and the 

 mean difference in temperature was 8-80 F. This was just as 

 much gas as we could get out the tank for in spite of the hot 

 water applied to the neck of the cylinder, it kept freezing up. 

 It appears that the carbon dioxide had little effect in keeping the 

 temperature about the heaters above that outside. 



All of the heaters were now placed in the open away from 

 buildings, being distributed about as smudge pots are dis- 

 tributed in the orchard, and from 75 to 90 K. W. (more than 

 100 H. P.) of power applied- Eight thermometers were used; 

 these were read every ten minutes after a steady state had been 

 reached and the mean taken. As a result of six experiments 

 the mean temperature of the air outside of the heated area feeing 

 70o F. the heaters caused a rise in temperature of llo Centi- 

 grade or 20o Fahrenheit and the anemometer showed a wind 

 velocity varying from a calm to five miles an hour. As an aver- 

 age it required 13 watts applied to a square foot to raise the 

 temperature 1 degree Fahrenheit. 



AMOUNT OF HEAT REQUIRED FROM SMUDGE POTS 

 AND ELECTRIC HEATERS COMPARED 



Considering the common smudge oils as giving out 18,800 

 British Thermal units of heat per pound that is burned and 

 considering a gallon of this oil to last four hours and remem- 



(i). Plenty of gas was liberated because when 1000.0 Ibs of coal 

 in 20 Ib. pots distributed over an acre burned 3.5 hours gave a rise in 

 temperature of 5.6 degrees Fahrenheit, (Farmers Bull. 104, p. 20). This 

 when burned, produced 2660 Ibs. of carbon dioxide, or .06 Ibs. per square 

 foot. At the end of the first half hour there would be approximately 

 .008 Ibs. per square foot. And if the gas rises to a height of fifty feet 

 the lower air would have on an average of .2 per cent carbon dioxide 

 at the end of the first hour. In our experiment where 18.5 Ibs. of 

 carbon dioxide were liberated in the inclosure, the gas was not warm 

 and being heavier than air it would stay largely within the inclosure. 

 This being true there would be .037 Ibs per square foot and an average 

 of 3 per cent carbon dioxide which is about 15 times as much as resulted 

 from the burning of the coal. 



