Electrical heating is a process in which electrical energy is converted to heat. Common applications include water heaters and industrial processes. An electric heater is an electrical device that converts an electric current into energy. The heating element inside each electric heater is an electric converter, and works on the Joule heating principle: the electric current passing through the resistor will convert electrical energy into thermal energy. Most modern electric heaters use nikrom wire as an active source; the heating element, pictured on the right, uses a chrome wire supported by a plastic insulator.
Alternatively, the heat pump uses an electric engine to drive the cooling orbit, which draws heat energy from a source such as soil or outdoor air and directs the heat to the space to be warmed. Some systems can be reversed so that the interior space is cooled and warm air is thrown out or into the ground.
Video Electric heating
Warm-up space
Warm up space is used to warm the interior of the building. Space heating is useful in places where handling air is difficult, as in the laboratory. Some electric space heating methods are used.
Radiator beaming
Electrical radiation heating uses heating elements that reach high temperatures. These elements are usually packed inside a glass-like glass envelope and with reflectors to direct the energy output of the heating body. Elements emit infrared radiation that travels through the air or space until it touches an absorbent surface, where some is converted to heat and partly reflected. This heat directly warms people and objects in the room, rather than heating the air. This heating style is very useful in areas where the airflow is not heated. They are also ideal for basements and garages where spot heaters are desirable. More generally, they are an excellent choice for specific task heating.
Radiant beamed operate silently and presents the greatest potential danger from ignition of nearby furniture due to the intensity of the focus of their output and the lack of overheat protection. In the United Kingdom, this equipment is sometimes called an electric fire, because it was originally used to replace open flames.
The heat-active medium described in this section is a nickel-resistance wire coil in a fused silica tube, exposed to the atmosphere at the end, although the model exists where the fused silica is sealed at the end and the non-nickel-resistance alloy..
Convection heater
In convection heaters, heating elements heat the air in contact with heat conduction. Hot air is less dense than cold air, so it rises because of buoyancy, allowing more cold air to flow in to replace it. It forms a current of hot air convection rising from the heater, heating the surrounding space, cooling and then repeating the cycle. This heater is sometimes filled with oil. They are perfect for heating the enclosed spaces. They operate quietly and have a lower risk of ignition hazard if they make unwanted contacts with furniture compared to radiant electric heaters.
Fan heater
The fan heater, also called forced heating convection, is a convection range of heaters that includes an electric fan to accelerate the airflow. They operate with noise caused by the fan. They are at risk of moderate ignition hazards if they make unintentional contact with the furniture. Their advantage is that they are more compact than heaters that use natural convection and are also cost effective for portable and small heating systems.
Warming up storage
Storage heating systems take advantage of cheaper electricity prices, sold during periods of low demand such as overnight. In the UK, it is named Economy 7. The storage heater stores heat in clay bricks, then releases it during the day when it is needed. New storage heater can be used with various rates. While they can still be used with economy 7, they can be used at daytime rates. This is due to the modern design features added during manufacturing. Along with new designs the use of thermostats or sensors has improved the efficiency of heating storage. A thermostat or sensor can read the room temperature, and change the heater output accordingly.
Water can also be used as a heat storage medium.
Under-floor domestic electric heating
Under-floor electrical heating systems have heating cables embedded in the floor. The current flows through a conductive heating material, provided either directly from the line voltage (120 or 240 volts) or at the low voltage of the transformer. The heated cables warm the floor by direct conduction and will die upon reaching the temperature determined by the floor thermostat. The warmer floor surfaces radiate heat to the cooler surface around it (ceilings, walls, furniture.) That absorb heat and reflect all the heat that is not absorbed onto other cold surfaces. The radiation, absorption and reflection cycles begin slowly and slowly slowly approach the set-point temperature and stop after the balance is achieved. A floor thermostat or a room thermostat or combination controls the floor on/off. In the heating process the thin layer of air associated with the warmed surface also absorbs some heat and this creates a bit of convection (air circulation). Contrary to believing that people are not heated by warm air circulation or convection (convection has a cooling effect) but is heated by direct radiation from the source and reflection of its surroundings. Convenience is achieved at lower air temperatures because it eliminates air circulation. The radiant heating experiences the highest level of comfort as a person's personal energy (Ã, Â ± 70 Watt for adults) (should radiate out in the heating season) balanced with the surroundings. Compared with the convection heating system based on academic research the air temperature can be lowered to 3 degrees. One variation is to use a tube filled with hot water circulation as a heat source to warm the floor. The principle of heating remains the same. Both warm and warm (hydronic) water systems with under floor heating systems are embedded in slow floor construction and can not respond to external weather changes or internal demand/lifestyle requirements. The latest variant puts special electric heating systems and blankets directly under floor decoration and on top of the additional insulation all placed on top of the construction floor. Floor construction remains cool. Changing the principle of heat source positioning allows it to respond within minutes to change the weather and internal demand requirements such as incoming/outgoing lifestyle, at work, rest, sleep, more people present/cooking etc.
Lighting system
In large office towers, lighting systems are integrated with heating and ventilation systems. Waste heat from fluorescent lamps are captured in the air back from the heating system; in large buildings largely from the annual heating energy supplied by the lighting system. However, waste heat is a liability when using air conditioning. Such expenditure can be avoided by integrating energy-efficient lighting systems that also create a source of electrical heat.
Heat pump
The heat pump uses an electrically driven compressor to operate a cooling cycle that extracts heat energy from the outside air, soil or groundwater, and transfers heat to the warmed space. The liquid contained in the evaporator part of the heat pump boils at low pressure, absorbing heat energy from the outside air or soil. The steam is then compressed by the compressor and piped into the condenser coil inside the building to be heated. The heat from the hot solid gas is absorbed by the air inside the building (and sometimes also used for domestic hot water) causing the hot working fluid to condense back into the liquid. From there, the high pressure fluid is passed back to the evaporator section where it expands through the hole and into the evaporator section, completing the cycle. In the summer months, the cycle can be reversed to move heat out of the conditioned space and into the outside air.
The heat pump can obtain low-level heat from the outside air in mild climates. In areas with average winter temperatures well below freezing, ground source heat pumps are more efficient than air source heat pumps because they can extract residual solar heat stored on soil at warmer temperatures than are available from cold air. According to the US EPA, geothermal heat pumps can reduce energy consumption by up to 44% compared to air source heat pumps and up to 72% compared to heating electrical resistance. High purchase price of a heat pump vs. resistance heaters can be offset when AC is also required.
Maps Electric heating
Liquid heating
Soaking Heater
The immersion heater has an electric resistance heating element enclosed in a tube and directly placed in water (or other liquid) to be heated. Immersion heaters can be placed in an isolated hot water tank. Temperature sensors inside the tank trigger the thermostat to control the water temperature. Small portable immersion heaters may not have a control thermostat, as they are intended to be used only briefly and under operator control.
Domestic immersion heater
Domestic immersion heaters, usually rated at 3 kilowatts and at 1.5-inch British Standard Pipe screwplugs in the UK, run on normal domestic power supplies, but users can also take advantage of cheaper, off-peak electricity tariffs like Economy 7 (in the UK). In typical off-peak installations, the lower immersion heaters are connected to separate off-peak heating circuits and the upper heater is connected to the normal circuit through the switch itself. Consumers then have the option to supplement the available hot water supply at any time, rather than waiting for a cheaper supply to turn on (usually after midnight). Less insulated hot water cylinders will increase operational costs because consumers have to pay for electricity used to replace the lost heat.
Electric shower and heater without tank also use dip (shielded or bare) dips that are turned on with the water flow. A group of separate heaters can be changed to offer different heating levels. Electricity showerheads and tank-less heaters typically use 3 to 7.5 kilowatts.
Industrial immersion heater
Industrial soaking heater may be screws or flanges. The British condensed immersion heater is usually only rated at up to 24 kW, with 6 kW considered the top end that can be safely accommodated in a single-phase supply. Flanged immersion heaters (such as those used in boilers electricity) can be rated up to 2000 kilowatts, or more, and require a three-phase supply.
Electric immersion heater can heat water immediately adjacent to heating elements high enough to increase scale formation, generally calcium carbonate, in hard water areas. It accumulates in the element, and over time, when the element expands and contracts through its heating cycle, the scale cracks and falls to the bottom of the tank, increasingly filling the tank. This reduces the tank capacity and, where the immersion heater is secondary to water heating by a coil fed from a gas or oil-fired boiler, can reduce the efficiency of the primary heating source by closing the other coils and in turn reduce their efficiency. Regular rinsing of sediment accumulation can alleviate this problem.
Such problems can be avoided at the design stage, by maximizing the amount of heat elements in the liquid, thereby reducing the wattage density. It reduces the working temperature of the element surface, reducing the limescale buildup. The wattage density should be 40Ã, W/in 2 or below in the hard water area, but it can safely be 60Ã, W/in 2 (9.3/cm 2 ) where hard water does not matter. Generally, choosing the right wattage density - which can range from 2 to 60 watts per square inch - is a big part to ensure that the liquid is heated and the heater is working optimally.
Circulation heater
The circulating heater or "direct heat heat exchanger" (DEHE) uses a heating element incorporated into the "shell side" directly to provide a heating effect. All the electrical heat generated by the electric circulation heater is transferred to the media, so the electric heater is 100 percent efficient. Direct electric heat exchangers or "circulating heating" are used to heat liquids and gases in industrial processes.
Electrode Heaters
With an electrode heater, there is no wire-wound resistance and the liquid itself acts as a resistance. This has potential hazards, so the rules governing electrode heaters are very tight.
Environmental and efficiency aspects
The efficiency of any system depends on the definition of system boundaries. For electric energy customers, the efficiency of electric room heating is almost 100% because almost all purchased energy is converted into building heat (the only exception is fan noise and indication lamps that require very little electricity and almost none at all when compared to energy drawn very big from the heating itself). However, if a power plant supplying electricity is included, overall efficiency drops dramatically. For example, a fossil fuel power plant can only produce 3 units of electrical energy for every 10 units of fuel energy released. Although the electric heater is 100% efficient, the amount of fuel needed to generate electricity is more than if the fuel is burned in a furnace or boiler in a heated building. If the same fuel can be used for heating the room by consumers, it will be more efficient overall to burn fuel in the end user's building. On the other hand, replacing electric heaters with fossil fuel burning heaters, need not be good because it eliminates the ability to have renewable electric heating, this can be achieved with a power source from renewable sources.
Variations between countries produce electrical power affecting concerns about efficiency and the environment. In France 10% is produced from fossil fuels, in the UK 80%. Cleanliness and efficiency of electricity depend on the source.
In Sweden the direct use of electric heating has been restricted since the 1980s for this reason, and there are plans to stop it completely - see Oil phase-out in Sweden - while Denmark has banned the installation of direct electric space heaters in new buildings. for similar reasons. In the case of new buildings, low energy building techniques can be used that can almost eliminate the need for heating, as it is built to the standard of Passivhaus.
In Quebec, however, electric heaters are still the most popular form of home heating. According to the Canadian Statistics survey in 2003, 68% of households in the province use electricity for heating the room. More than 90% of all power consumed in Quebec is generated by hydroelectric dams, which have low greenhouse gas emissions compared to fossil fuel power plants. Low and stable rates are charged by Hydro-QuÃÆ' Â © bec, a utility owned by the province.
To provide heat more efficiently, electrically driven heat pumps can raise indoor temperatures by extracting energy from soil, outdoor air, or waste streams such as exhaust air. This can cut electricity consumption by as little as 35% from that used by resistive heating. Where the main source of electrical energy is hydroelectric, nuclear, or wind, transferring electricity through the network can be convenient, because the resources may be too far for direct heating applications (with the exception of solar thermal energy).
Economic aspects
The operation of electric heating resistivity to heat the area for a long time is very expensive in many areas. However, intermittent or partial daily use can be more cost-effective than overall heating of buildings due to superior zonal control.
For example: The lunchroom in the office has limited hours of operation. During periods of low use, a "monitor" heat level (50 ° F or 10 ° C) is provided by a central heating system. Peak usage times between 11:00 and 14:00 are heated to "comfort level" (70Ã, Â ° F or 21Ã, Â ° C). Significant savings can be realized in overall energy consumption, because the loss of infrared radiation through thermal radiation is not as big as the smaller temperature gradient between this space and the unheated outdoor air, as well as between the refrigerator and the (now colder) lunch room.
Economically, electric heat can be compared to other home heating sources by multiplying the local cost per kilowatt hour for electricity by the number of kilowatts used by the heater. For example: a heater of 1500 watts at 12 cents per kilowatt hour 1.5ÃÆ' â € "12 = 18 cents per hour. When comparing with fuel combustion it may be useful to convert kilowatt hours to BTU: 1.5 kWh ÃÆ'â € "3412.142 = 5118 BTU.
Industrial electric heating
Electric heating is widely used in industry.
The advantages of electric heating methods above other forms include precise temperature control and heat energy distribution, burning is not used to develop heat, and the ability to reach temperatures is not easily achieved by chemical combustion. Electric heat can be applied accurately to the exact point required in a process, at high concentrations of power per unit area or volume. Electric heating devices can be built in whatever size is needed and can be found anywhere inside the factory. The electrical heating process is generally clean, quiet, and does not release much heat by-products to the environment. Electric heating appliances have a high response speed, lending them to mass-fast cycling production equipment.
The limitations and disadvantages of electrical heating in the industry include higher electrical energy costs compared to direct fuel use, and the capital costs of both the electric heating device itself and the infrastructure required to deliver large amounts of electrical energy to the point of use. This may be somewhat offset by the advantages of in-plant efficiency (on-site) in using less energy overall to achieve the same result.
The design of the industrial heating system begins with the required temperature assessment, the amount of heat required, and a viable mode for transferring heat energy. In addition to conduction, convection and radiation, electric heating methods can use electric and magnetic fields to heat the material.
Methods of electrical heating include heating resistance, electric arc heating, induction heating, and dielectric heating. In some processes (eg, arc welding), electric current is directly applied to the workpiece. In other processes, heat is generated in the workpiece by induction or dielectric loss. In addition, heat can be produced and then transferred to the work by conduction, convection or radiation.
Industrial heating processes can be categorized broadly as low temperatures (up to about 400 ° C or 752 ° F), temperatures (between 400 and 1,150 ° C or 752 ° and 2,102 ° F), and high-temperature (above 1,150 Â ° C or 2,102 Â ° F). Low temperature processes include grilling and drying, curing finished, soldering, printing and plastic forming. Medium temperature processes include liquid and some non-metallic plastics for casting or rebuilding, as well as annealing, stress relieving and metal heat treatment. High temperature processes include steel making, brazing, welding, metal casting, cutting, smelting and preparation of some chemicals.
See also
References
Source of the article : Wikipedia
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