176 GREENHOUSES 



lowing table has been derived from it. To 

 use, measure the height of the water column 

 in feet, find from the table the factor for this 

 height, and multiply the square root of the 

 radiating surface in square feet by this fact- 

 or. The result will be the size of the flow 

 pipe, in inches (diameter) required. This 

 is based on the assumption that there is a 

 difference of 10 degrees in temperature be- 

 tween the water when it leaves and when it 

 enters the boiler. 



Height of 



Column (ft.) Diameter Factor 



5 0.133 



10 0.113 



15 0.104 



20 0.095 



25 0.091 



30 0.187 



For example, to supply a coil of ten itf- 

 inch pipes 100 feet long (500 square feet) 

 15 feet above the bottom of the boiler, would 

 require a feed pipe the diameter of which 

 would be represented by VSOQ x 0.104 equals 

 22.4 x 0.104 equals 2.33 or a 2%-inch pipe. 



Short Methods. The above formula 

 takes into consideration the fact that the 

 greater the height of the column of water 

 the more rapid the flow and consequently 



