170 THE DESIGN OF STATIC TRANSFORMERS 



that the icmpiTjitmv I'i.M- of the transformer shall IK- 

 not more than, for instance, III) , then if tin; temperature of 

 the room is '20 we may take (20 + 30 =) 50 as the tempera- 

 tuiv of the oil in the immediate neighbourhood of the cooling 

 pipi-s. As in the case of steam condensers, it will not he 

 practicable to raise the temperature of the water quite up to 

 the temperature of the medium external to the pipes. Con- 

 sequently if the water enters the transformer at, say, 18, it 

 will, with a sufficient length of piping, leave the transformer at, 



say, 45. It will thus have sustained a temperature rise of 

 (45 18 =) 27, and each ton will carry away (27 X 1,16 =) 

 31,3 kelvins of energy. The amount of water passing through 



the cooling coil must consequently be (o-r'o ) 0,447 ton per 



hour. (Since there are 220 gallons in one ton of water, this is 

 equal to 0,447 X 220 = 99 gallons per hour, or 1,65 gallons 

 per minute.) 



If in another instance, a temperature rise of 40 is per- 

 mitted, if the room temperature is 20, if the water enters 

 at 15, and if its final temperature attains to within 7 of the 

 temperature of the oil, then the quantity of water would be 

 calculated as follows : 

 Temperature of room ..... . 20 



Temperature rise of oil . . 40 



Ultimate temperature of oil . (20 + 40 =) 60 



Entrance temperature of water ..... 15 



Exit temperature of water . (60 7 =) 53 



Temperature rise of water . . (53 -- 15 =) 38 



Energy absorbed by each ton of water (1,16 X 38 =) 44 



kelvins 



Weight of water per hour . . . y = 0,319 ton 

 Volume of water per hour . (0,319 X 220 =) 70 gallons 

 Volume of water per minute . . f^g =J 1,17 gallons 



