China
Africa
Explore chapters and articles related to this topic
Lamps, Source Types, & Relative Photometry
Published in Michael Stiller, Quality Lighting for High Performance Buildings, 2020
Halogen lamps are very similar to incandescent lamps in their general workings. A filament is energized with an electrical current that causes it to heat up and glow. The main difference is that the filament of a halogen lamp is made of tungsten (a type of metal), and is enclosed in a smaller envelope filled with an inert gas and a halogen. (Halogens are a group of non-metal elements.) The combination of the halogen and tungsten allows the lamp to be run at a higher temperature without burning up. The result is a slightly cooler color of light and a slightly higher luminous efficacy (up to a maximum of 26 lumens per watt), making these lamps marginally more energy-efficient than traditional incandescent lamps. Like incandescent lamps, halogen lamps are dimmable through the full range of their output.
DC circuits
Published in William Bolton, Engineering Science, 2020
Not all circuit elements give graphs which are straight-line for the relationship between the potential difference across them and the current through them. Figure 9.13 shows examples of non-linear relationships that can be obtained with the circuit shown in Figure 9.11. Figure 9.13(a) is the type of graph obtained with a typical thermistor and Figure 9.13(b) is that obtained with a typical filament lamp. With the thermistor, the gradient of the graph decreases as the current increases and so the resistance decreases as the current increases. Thermistors (thermally sensitive resistors) are resistance elements made from mixtures of metal oxides, such as those of chromium, cobalt, iron, manganese and nickel. With the filament lamp, the gradient increases as the current increases and so the resistance increases as the current increases. The material used for a lamp filament is tungsten.
Pressure Measurement Techniques
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2020
The heat loss from the filament depends on the thermal conductivity of the gas in the vacuum space and the temperature of the filament. The thermal conductivity of the filament decreases with decrease in pressure and hence for a given electric energy the filament temperature increases with decrease of pressure. The filament temperature is measured from the variation of the resistance of the filament material. Usually tungsten or platinum is used as the filament. The heat loss from the filament is influenced by the ambient temperature also. Therefore, to compensate for the loss of heat due to ambient temperature variations, two gauges are connected in series, as shown in Figure 7.42. The measurement gauge is evacuated, and both the measuring and the compensation gauge are exposed to the same environment conditions. The bridge is adjusted to null position, using the resistance R2. Now the gauge is compensated for the ambient temperature and is ready for measurement.
Systematic Component Investigation of the Steady-State High-Temperature In-Pile Nuclear Thermal Propulsion Experimental Test Bed
Published in Nuclear Technology, 2022
Tyler R. Steiner, Richard H. Howard
The heater utilizes a filament to generate resistive heating. The filament is held within a ceramic crucible. The ceramic crucible is encompassed by a shell that is used to house thermocouples and other instrumentation. The ends of the ceramic crucible are capped with high-temperature and electrically conductive POCO graphite plugs to keep the filament in place while enabling current delivery. The crucible was a challenging component to push to higher temperatures; zirconia, alumina, hafnia, high-density magnesia, and high-purity magnesia were all tested in this work. The filament was historically cut from a piece of SIGRATHERM® GFA5. GFA5 is functional, however, tests indicated that a related material, SIGRATHERM® MFA5, provided better electrical stability at elevated temperatures and currents. An image labeling the various aforementioned parts of the heater is shown in Fig. 3.
Role of Joule heating and activation energy on MHD heat and mass transfer flow in the presence of thermal radiation
Published in Numerical Heat Transfer, Part B: Fundamentals, 2023
Bejawada Shankar Goud, Gurram Dharmaiah
Melting has many potential applications; light bulbs are a good example. The filament of an incandescent light bulb is comprised of tungsten. The metal filaments of light bulbs need to be heated to very high temperatures to create light. Further, Melt processing includes techniques such as injection molding, blow molding, extrusion, and rotational molding/lining are also comes under potential applications.