The system of heating

Besides masonry, a brick work, any engineer must know about heating and ventilation. They are two branches of engineering which are very closely connected. Both they are treated(1) as a dual subject. Heating is to prevent(2) too rapid loss of heat from the body. The rate of heat lost from the body is controlled. Some old concepts of heating have been gradually(3) changed since engineers obtained more precise knowledge about how the body loses heat. Insufficient(4) attention was paid formerly to loss by radiation, which is the transmission of energy in the form of waves from a body to surrounding bodies at a temperature. The human being also loses heat by conduction (through his clothes) and convection.

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The most widely used system of heating is the central heating.

There are two most common(5) systems of heating: hot water and steam. There the fuel is burned in one place, from which steam, hot water or warm air is distributed to adjacent and remote spaces to be heated.

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 the rooms. The steel or copper pipes give hot water to radiators or convectors which give up their heat to the rooms. Then cooled water is returned to the boiler for reheating.

As for steam systems, steam is usually generated. 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 radiators to the room. After this cooling of the steam condenses(6) to water. The condensate is returned to the boiler by gravity or by a pump. The air valve on each radiator is necessary for air to escape. Otherwise(7) it would prevent(8) steam from entering the radiator.

But, to do comfortable atmosphere is to use heating and ventilation together. Heating and ventilation are concerned with providing(9) a required atmospheric environment within a space to produce a desired temperature for comfort. Nowadays air-conditioning is closely related to both heating and ventilation.

We have mentioned about building materials as one of the components of building. It is high time to tell about them. It is important for an engineer to know that all building materials are used in two basic ways. In the first way they are used to support the loads on a building and in the second way they are used to divide the space in a building. But it is more important to realize that building components are made from building materials.

1. The first type of a construction is made of building materials such as a brick, a stone or concrete. They are called blocks. The blocks arc put together to form solid(10) walls. These materials are heavy. They can support the structural loads because they have the property of high compressive strength. At the same time the walls made up of blocks support the building and divide the space in the building.

2. The second type of a construction is made of sheet materials.

Timber, concrete and some plastics can be made into large rigid sheets and fixed together to form a building. Such kind of buildings is lighter and faster to construct than a building made up of blocks.

3. The third type of a construction is made of rod materials. They can be used for structural support but not for dividing spaces. There timber, steel and concrete can be formed into rods. Usually rod materials are used as columns because of high tensile(11) and compressive strength. On the other hand, they can be fixed together to form framed structures. The spaces between the rods can be filled with light sheet materials.

Building materials are very important in the construction. But it is more important for any designer to select and adapt such building materials of construction that will give the most effective result by the most economical means. In this choice of materials for any work of constructions many factors must be considered(12) by the civil engineer. These factors include availability(13), cost, physical properties of materials and others.

Practically, all buildings materials have their advantages and disadvantages. That's why some materials are used most widely in building construction for the purpose of binding together masonry units. Among them are lime, gypsum and cement. Last material forms very important elements in all masonry structures, such as stone, a brick.

Since the time of its introduction a gradual(3) improvement of Portland cement quality has led to the elaboration of rapid hardening Portland cement.

So, cement is the most important component of concrete. Concrete is even less uniform than many other materials. Concrete may be considered(12) an artificial conglomerate of "crushed stone, gravel or similar inert(14) material with a mortar".

One of the building materials used in a construction is a brick. The production of a brick was industrialized in the 19th century. Earlier it was a process of hand-molding. Later it was superseded by «pressed» bricks. It wa