DEVELOPMENT OF HOUSE HEATING 



131 



quantity of water from the freezing point to the boiling 

 point. 



Very careful experiments repeated many times have proved 

 that these figures should be 5.36. Heat which is used thus 

 to change the state of matter without changing its tem- 

 perature is called INSENSIBLE HEAT. When used to change 

 a liquid to a vapor, it is called HEAT OF VAPORIZATION. When 

 used to change a solid into a liquid, it is called HEAT OP FUSION. 

 We now see that the heat of vaporization of water is 5.36 times 

 the sensible heat of raising the same amount of water from the 

 freezing point to the boiling point. 



STEAM HEATING 



151. Principles of Steam Heating. We saw in Arts. 20 

 and 21 that the temperature of steam arising from boiling 

 water is nearly the same as that of the water. It is also known 



FIG. 96. System of piping for steam heating system. 



that as long as the pressure remains constant the tempera- 

 ture of the steam remains the same. In Art. 150 we saw 

 that a large amount of heat must be put into water to turn it 

 into steam. When the steam is again turned into liquid, 

 i.e., liquefied, exactly the same amount of heat is given off 

 as was absorbed in the vaporizing. Steam heating depends 

 upon an application of these principles. 



