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Farmers' Bulletin 1096. 



reduced by mixing with the cold outside air. This is the function 

 of the tall stack. Generally speaking, the high-stack heaters burn 

 with less smoke and soot than any other type in general use. The 

 short-stack heaters throw off less smoke than the lard-pail type, but 

 the amount is large enough to be object ion able. 



The high-stack type of heater is open to the objections that the 

 heat is released too far above the ground, at too high a temperature 

 and with too great an upward velocity to obtain the best results. 

 These objections would probably be serious in localities where the 

 temperature inversion is slight, but in southern California, where 

 these heaters are in most general use, the temperature is often 20 

 higher on a cold night at a height of 200 feet above the ground than 

 at the ground. 



FIG. 6. Short-stack oil heaters in orange grove. The one on the left has cover removed 

 and draft open. This type of heater has given great satisfaction where there is not 

 too much objection to the formation of heavy smoke. 



There is no doubt the heat should be liberated as near the ground 

 as possible in order to obtain the best results. However, at the 

 present time the use of the high stack is the only practicable means 

 of obtaining fairly perfect combustion. Some of the heat from 

 these heaters is undoubtedly lost through its rising too high above the 

 ground, but this is probably nearly offset by the additional heat ob- 

 tained through the more complete combustion. The smoke and soot 

 given off by other types of heaters are more or less completely con- 

 sumed in the high-stack heater. It is estimated that from 40 to 50 

 per cent of the heat in the oil is made available in the lard-pail 

 type, as against TO to 80 per cent in the high-stack type. 



