Some Applications of Heat 109 



Steam Heating Method. In using the steam heating method, 

 a steam boiler is installed in the basement of the building. This 

 boiler is connected, by means of pipes, with radiators in the 

 rooms to be heated. There is a set of pipes through which the 

 steam ascends to the radiators and through which the condensed 

 steam returns as water to the bottom of the boiler. In large 

 buildings it is often necessary to have more than one boiler. In 

 rooms heated by steam, the air is usually dry and should be 

 moistened. 



The radiator surface in a room should contain in square feet 

 about one-fiftieth of the number of cubic feet of space to be 

 heated. The radiator itself is heated on the inside by conduction 

 and the heat flows through the metal to the outside in the same 

 way, thus warming the air which comes in contact with it. The 

 room is heated partly by radiation, partly by conduction, but largely 

 by convection currents. These convection currents carry the heat 

 upward from the radiators, and other similar currents are set up 

 in the rooms by the alternate heating and cooling of the air. 



Hot Water Method. The hot water method of heating 

 buildings differs from the steam method in having the boiler, the 

 radiators and the pipes full of water, and in having a tank in the 

 attic, connected by a pipe, for receiving the extra volume of water 

 due to expansion by heating. 



One set of pipes connected with the boiler carries the hot 

 water to the radiators, and another set of pipes, also connected 

 with the boiler, conveys the water, after it cools, back to the boiler. 

 The pipes that convey the water to the radiators start from the 

 top of the boiler, and those which return the water are connected 

 with the boiler at the bottom. In the hot water method, radiation, 

 conduction, and convection are employed. The water in the 

 boiler receives its heat from the fire by conduction through the 

 walls of the boiler. When the hot water reaches the radiators, 

 the cold iron immediately takes up some of the heat, passing it 

 through the iron by conduction to the air in the room to be heated. 

 Convection currents are at once formed. Although considerable 

 heat leaves the radiator by radiation, much of it is carried by 

 these convection currents. 



