HEATING BUILDINGS 



107 



duction and transmitted to the water in the boiler by 

 conduction. The water next to the hot iron in the boiler, 

 as it receives the heat expands, that is, becomes less 

 dense, and is then forced upward by the cooler water at 

 the bottom of the boiler, which is more dense. The 

 supply of cool water is kept constant by the return from 

 the radiators in the rooms. 



This hot water is thus forced through the pipes from 

 the boiler to the radiators and transmits its heat to the 

 metal of the radiators by conduc- 

 tion. The heat passes off the ra- 

 diator into the room partly by 

 radiation, warming the objects in 

 the room, and partly by conduction 

 to the air which is touching the ra- 

 diator. This air, as it is warmed, 

 is forced toward the ceiling by the 

 cooler air in the room flowing 

 toward the radiator, where it in 

 turn is heated and forced toward 

 the ceiling; thus convection cur- 

 rents are set up in the air, which 

 distribute the heat of the radiator 

 to all parts of the room. The heat 

 is transmitted from the boiler to 

 the radiators in the rooms by the 

 flow of the_ water. What method 

 of transferring heat is this? 



The hot water system of heating is one of the most 

 economical that can be used in a private house. By 

 this system the temperature of the house can be most 

 easily controlled in the early fall and late spring. A 

 small fire in the boiler will warm, the water sufficiently 



STEWART HEATER FOR 

 HOT WATER SYSTEM 



