132 



RELATION OF HEAT TO COMFORT 



for many years. It is quite likely that primitive man 

 lived in caves that were heated with open fires. Doubt- 

 less he had to contend with much smoke and many 

 odors. The American Indian built a fire on the floor of 

 his wigwam, and the smoke escaped through a hole at 

 the top. The building of a fireplace into the wall of a 

 house with a chimney attached to remove the smoke 

 and gases marked an important step forward in heat- 

 ing which led finally to the invention of modern stoves 

 and furnaces. 



The fireplace has been in use for centuries. It adds 

 cheer and comfort to the living room of modern 

 homes, and because of its increasing use must be con- 

 sidered a modern home heating device as well as an 

 old one. It has some decided disadvantages, however, 

 that should be considered. It is a very uneconomical 

 heating device because much of the fuel is wasted, 



FIG. 205. COLONIAL FIREPLACE 



most of the heat being carried up the chimney by con- 

 vection currents. Since the heated air passes up the 

 chimney and since air is a poor conductor of heat, 

 the heating of the room is done mainly by radiation. 

 This results in -very uneven heating. Near the fire it 

 is too hot for comfort and some distance away it is 

 too cool. 



Probably the principal advantage of the fireplace 

 lies in the fact that it insures good ventilation. Good 

 air flows into the house around the windows and 

 doors. As the currents of air inside the house are 

 toward the fire, the stale air is rapidly removed 

 through the chimney. 



Stoves have been in use for about two centuries. 

 The first stoves were merely iron boxes with a door 

 at one end and an opening in the top for smoke to 

 escape. Later Benjamin Franklin invented what is 

 known as the Franklin stove (Fig. 206). It consisted 

 at first of a small open box of iron that was placed in- 

 side a fireplace. It was built so that part of the iron 

 box extended into the room. This made for greater 

 efficiency in heating for two reasons : the heated iron 



FIG. 206. FRANKLIN STOVE 



radiated heat better 

 than brick or stone, and 

 layers of air next to the 

 iron, extending into the 

 room, were heated and 

 set up convection cur- 

 rents in the room. Thus 

 less heat escaped 

 through the chimney. 



The modern stove is 

 a greatly improved de- 

 vice. It consists of a 

 stove inside a steel jack- 

 et (see Fig. 207). The 

 air between the stove 

 and the jacket is heated by the burning fuel in the 

 stove. Convection currents which are set up heat the 

 room. Heat energy is also radiated from the stove. 



The rate of burning in the modern stove is con- 

 trolled by three drafts and a smoke-pipe damper (see 

 Fig. 207). When making fire we open the lower draft 

 and the smoke-pipe damper and close the other two 

 drafts. This provides for the largest amount of air. 

 possible to pass through the fuel. After the fire is 

 burning well, the lower draft and the chimney damper 

 are closed. This decreases the amount of air passing 

 through the fire. The hot blast draft is opened next ; 

 this permits air to enter the fire pot above the burning 

 fuel. This provides for better burning of combust- 

 ible gases and carbon particles which otherwise would 



SMOKE -PIPE DAMPER 



SMOKE PIP; 



DAMPER 



FIRE DOOR 



ASHPIT 



FIG. 207. MODERN STOVE 



form smoke and soot. If a slower rate of burning is 

 desired, the check draft is opened. Can you figure 

 out why opening the check draft decreases the rate 

 of combustion? 



How is a home heated by means of a hot-air fur- 

 nace? Although hot-air furnaces are placed in the. 

 basement, they operate on the same principles as the 

 modern stove just described. There are two different 

 types: the pipeless hot-air furnace (Fig. 208), which 

 has a single register through which convection cur- 



