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118
There are two most common systems of heating - hot water and steam.
Both systems are widely used nowadays. A hot-water system consists of the
boilers and a system of pipes connected to radiators suitably located in rooms to
be heated. The pipes, usually of steel or copper, feed hot water to radiators or
convectors which give up their heat to the room. The water, now cooled, is re-
turned to the boiler for reheating. As for steam systems, steam is generated usu-
ally, at less than 5 pounds per square inch in the boiler and the steam is led to
the radiators through or by means of steel or copper pipes. The steam gives up
its heat to the radiators and the radiator to the room and the cooling of the steam
condenses it to water. The condensate is returned to the boiler either by gravity
or by a pump. The air valve on each radiator is necessary for air to escape. Oth-
erwise it would prevent steam from entering the radiator. Recent efforts to
completely conceal heating equipment have resulted in an arrangement
whereby the fluid, whether it be hot water, steam, air, or electricity, is circulated
through distribution units embedded in the building construction. Panel heating
is a method of introducing heat to rooms in which the emitting surfaces are usu-
ally completely concealed in the floor, walls, or ceiling. The heat is dissemi-
nated from such panels partly by radiation and partly by convection, the relative
amounts depending on the panel location. Ceilling panels release the largest
proportion of heat by radiation and floor panels the smallest. The proportion of
heat disseminated by radiation and convection is also dependent to some extent
upon panel-surface temperatures.The basic advantage claimed
for a panel heat-
ing system is that of comfort.
Application of certain panels is frequently restricted by structural details,
other factors to be considered are type of occupancy, furniture or equipment lo-
cation, large glass areas, heat-storing capacity of building construction, room
height, possible change of wall partitions, climate, exposure, and first cost.
Building materials. Metals
All metals are divided into ferrous metals
and non-ferrous metals.
Ferrous metals are metals and alloys
the main component of which is
iron. The classification of ferrous metals includes iron, steel and its alloys.
Metals, in general, and especially ferrous metals are of great importance
in various constructions.
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