Systems of Heating

Heating. In order to maintain standard room temperature, the heating apparatus must supply heat to replace the lost through the walls, floors, and ceilings, and, in addition, the heat necessary to warm the cold fresh air used for ventilation. Heat is lost by conduction through cracks around doors, windows, etc.

Systems of heating. Leaving stoves and fireplaces out of consideration, the systems ordinarily employed for heating may be classified as follows:

a) hot air

b) steam

c) hot water

Hot air systems. In a hot air system, heated air from the furnace is introduced through leaders, stacks, and registers into the room. This air is at a higher temperature than the room, and, in flowing across the ceilings and down by the walls, heat is abstracted until it is eventually cooled to the desired room temperature. Fresh warm air from the furnace then forces the air that has been cooled to room temperature out of the room through cracks, fireplaces, etc. A heat balance may therefore be written as follows: the heat given up by the entering air equals the heat lost by conduction.

The force which causes hot air to flow from furnace to room results from the difference in densities of the cold air outside and the warm air inside the furnace and pipes.

Advantages. A hot air system is cheap to install, has a low cost of maintenance, and is not hard to manage, its operating cost is little, if any, greater that of hot water or steam system of equal capacity.

Positioning Tools

From using the sun, the moon and the stars to the development of compasses and maps and in very recent times the technology of satellite GPS systems and radar, man has always needed a way to find his bearings, whether travelling on foot, at sea or in the air. Navigation is as fundamental for humans today as it was in the past, and with all the sophisticated technology now available navigation tools are not just used to stop people getting lost.

Consider the transport industry for example. A GPS tracking system on a truck can ensure that a driver takes the best route - avoiding traffic, saving time and petrol costs - but it also helps the transport company to monitor the driver and ensure that he respects the speed limits, only travels at the permitted times and rests at regular intervals for the required amount of time, respecting the law and increasing safety. It can even allow the company to find the vehicle in case of theft!

You have probably used maps on the internet or your mobile phone, and have seen how satellite images can now identify places with incredible detail, even looking into your living room from the sky above! This can be useful for planning a trip before you leave or finding a friend's house; but the technology is also used for a whole series of professional purposes: from calculating weather to urban planning and even security and warfare.

Like all forms of technology the GPS has a few disadvantages of course - it is not always 100% reliable – the suggested route may not always be the best, because some problems are not signaled or the information transmitted to the map is not completely accurate; and some people consider that GPS is an invasion of their privacy. However, this technology is obviously here to stay, and destined to improve; and, if used properly, its advantages are clearly greater than its drawbacks.