Radiator
From Free net encyclopedia
Radiator is a common term for several types of heat exchangers. Radiators can be used in automobiles, buildings, and electronics.
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Automobiles
In automobiles with an internal combustion engine, a radiator is connected to channels running through the engine and cylinder head, through which is pumped a liquid. This liquid is typically a mixture of water with ethylene glycol (a.k.a. antifreeze). The fluid moves in a closed system from the radiator to the engine, where it conducts heat away from the engine parts, perhaps to help warm the interior cabin. It then flows through a thermostat (controlling the rate of flow) back to the radiator, where it is cooled again by convection with the air. This process cools the entire engine. The invention of the automobile water radiator is attributed to Karl Benz. Some engines have an additional oil cooler; a separate small radiator to cool the motor oil. Turbo charged engines may have an intercooler.
Buildings
Image:Radiator.jpg In buildings, a radiator is a heating device, which is warmed by steam from a boiler or hot water being pumped into it from a water heater (usually, if not quite accurately, referred to as a "boiler"). The term is somewhat of a misnomer, as radiators in building transfer the majority of their heat not by radiation, but by convection.
Conventional radiators
A conventional hot-water radiator consists of a sealed hollow metal container, usually flat in shape. Hot water enters at one end and rises to the top of the radiator by way of convection. As it gives out its heat, it cools and sinks to the bottom of the radiator and then is forced out of a pipe at the other end. If there is air trapped inside the radiator, then the water cannot rise to the top, and only the bottom area gets hot. A bleed screw near the top of the radiator allows the trapped air to be 'bled' from the system, and thus restore correct operation. Often radiators located on upper floors will accumulate more air than ones on lower floors as the air will tend to rise to the topmost point in the system. These may have to be bled more often. Usually radiators are bled once or twice per season, or as needed. Another reason to exclude air is to minimise corrosion of the steel pressed radiators. The air near a radiator is heated and produces a convection current drawing in cold air to heat. If set up improperly they can make loud banging noises like someone hammering on the pipes. This is due to the pipes rubbing on surrounding surfaces while expanding and contracting due to heat changes. Stereotypical radiators (as pictured) are no longer common in new construction. The radiator was invented in 1855 by Franz SanGalli, an Italian-born German living in Russia. He was the first to produce a system of central heating and patented his invention in Germany and the US.
Steam has the advantage of flowing through the pipes under its own pressure without the need for pumping. For this reason, it was adopted earlier, before electric motors and pumps became available. Steam is also far easier to distribute than hot water throughout large, tall buildings like skyscrapers. However, the higher temperatures steam systems operate at make them inherently less efficient, as unwanted heat loss is inevitably greater. Steam pipes and radiators are also prone to banging if condensate fails to drain properly; this is often caused by buildings settling and the resultant pooling of condensate in pipes and radiators that no longer tilt slightly back towards the boiler.
Fan assisted radiators
A more recent type of heater used in homes is the fan assisted radiator. It contains a heat exchanger fed by hot water from the heating system. A thermostatic switch senses the heat and energises an electric fan which blows air over the heat exchanger.
Advantages of this type of heater are its small size and even distribution of heat around the room. Disadvantages are the noise produced by the fan, and the need for an electricity supply.
Underfloor heating
The current trend in radiant heating is towards floor heating, where the hot water is circulated under the entire floor of each room in a building. A network of pipes or heating cables is buried in the floor, and a gentle heat rises into the room. These systems are reputed to have a high level of comfort, but are generally difficult to install into existing buildings.
The hypocaust was a Roman heating system using a similar principle of operation.
Electronics
In electronics, a radiator is also known as a radiating element. Radiating elements are a basic subdivision of an antenna. Radiating elements are capable of transmitting or receiving electromagnetic energy.bg:Радиатор de:Radiator es:Radiador fi:Lämpöpatteri nl:Radiator pl:Radiator ru:Радиатор sv:Radiator