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Radiators andconvectors areheat exchangers designed to transferthermal energy from one medium to another for the purpose of space heating.
Denison Olmsted of New Haven, Connecticut, appears to have been the earliest person to use the term 'radiator' to mean a heating appliance in an 1834 patent for a stove with a heat exchanger which then radiated heat. In the patent he wrote that his invention was "a peculiar kind of apparatus, which I call a radiator".[1] The heating radiator was invented byFranz San Galli in 1855, aKingdom of Prussia-bornRussian businessman living inSt. Petersburg.[2][3] In the late 1800s, companies, such as theAmerican Radiator Company, promoted cast iron radiators over previous fabricated steel designs in order to lower costs and expand the market.
Aradiator is a device thattransfers heat to a medium primarily throughthermal radiation. In practice, the term radiator is often applied to any number of devices in which a fluid circulates through exposed pipes (often with fins or other means of increasing surface area), notwithstanding that such devices tend to transfer heat mainly byconvection and might logically be calledconvectors.
The termsconvection heater andconvector refer to a class of devices in which the source of heat is not directly exposed. As domestic safety and the supply from water heaters keep temperatures relatively low, radiation is inefficient in comparison to convection.[citation needed]
Steam has the advantage of flowing through 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 likeskyscrapers. However, the higher temperatures at which steam systems operate make them inherently less efficient, as unwanted heat loss is inevitably greater.
Steam pipes and radiators are prone to producing banging sounds calledsteam hammer. The bang is created when some of the steamcondenses into water in a horizontal section of the steam piping. Subsequently, steam picks up the water, forms a "slug" and hurls it at high velocity into a pipe fitting, creating a loud hammering noise and greatly stressing the pipe. This condition is usually caused by a poor condensate drainage strategy and is often caused by buildings settling and the resultant pooling of condensate in pipes and radiators that no longer tilt slightly back towards theboiler.[citation needed]
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A hot-water radiator consists of a sealed hollow metal container filled with hot water from aboiler or other heating device by gravity feed, a pump, ornatural convection. As it gives out heat, the hot water cools and sinks to the bottom of the radiator and is forced out of a pipe at the other end.Anti-hammer devices are often installed to prevent or minimize knocking in hot water radiator pipes.
Unlike steam or hot water systems which receive heat from a boiler, electric radiators produce heat from electricity at the location of the radiator. This heat may be transferred to a fluid (such as oil) inside the radiator. The oil circulates inside the radiator by convection, which distributes the heat from the heating element to the surface of the radiator. Smaller electric radiators have the advantage of being portable, as they do not need to be connected to pipework. Some electric radiators can also use hot water; this is particularity common forheated towel rails, where the radiator uses hot water when the central heating system is running but switches to electricity when heating the whole building is not required.
Cast iron radiators may be used with hot water or steam systems. Traditional cast iron radiators are no longer common in new construction, replaced mostly with forced hot water baseboard or panel radiators, but they remain available.
Hot-water baseboard convectors (often referred to as "fin-tube radiators") consist of copper pipes which have aluminum fins attached to increase their surface area. Conduction is used to transfer heat from the water circulated in the pipes into the metal radiators or convectors.
Baseboard convectors are designed to heat the air in the room using convection to transfer heat from the radiators to the surrounding air.[4] They do this by drawing cool air in at the bottom, warming the air as it passes over the radiator fins, and discharging the heated air at the top. This sets up convective loops of air movement within a room. If the radiator is blocked either from above or below, this air movement is prevented, and the heater will not work. Baseboard heating systems are sometimes fitted with moveable covers to allow the resident to fine-tune heating by room, much like air registers in a central air system.
Panel radiators arewelded from flat or corrugated steel panels, and are usually hung from the wall. They are usually used with hot water systems, but electric versions are also available. The panels often have fins attached, increasing the surface area and therefore the rate of heat transfer into the air (power). Several panels may be stacked together to make one radiator, and the resulting radiator is referred to with a two-digit type number. The first digit is the number of panels, and the second is the number of sets of fins, for example a type 21 radiator has two panels with one set of fins in between. Air flow around the radiator and between the panels is by convection only, and must be unrestricted if the radiator is to reach its design performance. The heat output of panel radiators is regulated by controlling the flow of hot water, with either a manual or athermostatic valve.
Radiators can also be made from aluminium which is a very good conductor of heat and has better thermal conductivity compared to that of steel. Aluminium radiators tend to have a low water content so this combined with the excellent thermal conductivity qualities of the metal itself make aluminium radiators very responsive to changes in the temperature demand.[5]
A fan-assisted convector contains aheat exchanger fed by hot water from the heating system. Athermostatic switch energises an electricfan which blows air over the heat exchanger to circulate it in a room. Its advantages are small relative size and even distribution of heat. Disadvantages are fan noise and the need for both a source of heat and a separate electrical supply.
Also known as "radiant heat", underfloor heating uses a network of pipes, tubing or heating cables, buried in or attached beneath a floor to allow heat to rise into the room. Best results are achieved with conductive flooring materials such as tile. The large surface area of such room-sized radiators allows them to be kept just a few degrees above desired room temperature, minimizingconvection. Underfloor heating is more expensive in new construction than less efficient systems. It also is generally difficult to retrofit into existing buildings.
The Romanhypocaust employed a similar principle of operation.
Skirting-board radiators are a form of heater which involves placing radiators inside a skirting board. Hot water is piped though the system, usually taken directly from the central heating system.[6]
Radiators, as any system of heating air that does not add water, reduce relativehumidity, possibly contributing to dry skin, reduced comfort, and shrinkage of wood flooring. However, ahumidifier can mitigate this issue.[7]
radiator 1855 invented.
