A heat shield is designed to protect a substance from absorbing excessive heat from an external source either by scattering, reflecting or simply absorbing heat. This is often used as a form of waste heat management.
Video Heat shield
Thermal protection system
Passive cooling
The passively cooled shield is used initially to absorb the hot peaks and then shine the heat stored into the atmosphere. Unfortunately, early versions require large quantities of metals such as titanium, beryllium, copper, etc. That greatly increases the mass of the vehicle. Absorption of heat and ablative system for the better.
However, in modern vehicles, they can be found, but instead of metal, carbon-reinforced carbon materials are used (also called RCC) reinforced carbon-carbon or carbon carbon ). This material is a thermal protection system from the nose and the front edge of the Space Shuttle and is proposed for X-33 vehicles. Carbon is the best known refractory material with a sublimation temperature (for graphite) of 3825 ° C. This characteristic makes it a very suitable material for passive cooling, but with the disadvantage of being extremely expensive and fragile.
Some high-speed aircraft, such as the Concorde and SR-71 Blackbird, should be designed considering similar, but lower, too hot for what is happening on the spacecraft. In the case of Concorde, the aluminum nose is allowed to reach a maximum operating temperature of 127 ° C (180 ° C higher than ambient air outside that is below zero); the metallurgical consequences associated with peak temperature are significant factors in determining the maximum aircraft speed.
Recently new materials have been developed that can be superior to '' RCC . Prototype SHARP ( S lender H ypervelocity A erothermodynamic R esearch P robe) is based on Ultra-high-temperature ceramic (UHTC) materials, such as zirconium diboride (ZrB 2 ) and hafnium diboride (HfB 2 ). The thermal protection system based on these materials will allow it to reach Mach 7's speed at sea level, Mach 11 at 35000 meters and significant improvements to vehicles designed for Hypersonic speed. The materials used have thermal protection characteristics in the temperature range from 0 Â ° C to 2000 Â ° C, with a melting point in excess of 3500 Â ° C. They are also structurally more resistant than RCC, so they do not require additional reinforcements, and very efficient in irradiating the absorbed heat. NASA funded (and then stopped) a research and development program in 2001 to test this protection system through the University of Montana.
The European Commission is funding a research project, C3HARME, under the NMP-19-2015 call Program Framework for Research and Technology Development 2016 (ongoing) for the design, development, production and testing of a new class of ultra-refractory ceramic composite matrix reinforced with silicon fibers carbides and carbon fibers suitable for applications in severe aerospace environments.
Maps Heat shield
Usage
Automotive
Due to the large amount of heat released by the internal combustion engine, a heat shield is used on most machines to protect components and bodywork from heat damage. As well as protection, an effective heat shield can provide performance benefits by reducing the under-cap temperature, thereby reducing the intake temperature. The heat shield varies greatly in price, but is mostly easy to install, usually with stainless steel clips or high temperature bands. There are two main types of automotive heat protectors:
- The rigid heat shield, to date, is made of solid steel, but is now often made of aluminum. Some high-end rigid heat shields are made of aluminum or other composite sheets, with a ceramic thermal barrier layer to enhance heat insulation.
- Flexible heat protectors are usually made of thin aluminum sheets, sold flat or in rolls, and are bent by hand, by artisans. High performance flexible heat shields sometimes include extras, such as ceramic insulation applied through plasma spraying. These latest products are commonplace in the world of top automotive such as Formula 1.
- Textile heat shields are used for various components such as exhaust, turbo, DPF, or other waste components.
As a result, heat shields are often installed by amateur and professional personnel during the machine's tuning phase.
The heat shield is also used to cool engine mount vents. When a vehicle is at a higher speed, there is enough ram air to cool the engine compartment beneath the hood, but when the vehicle is moving at a lower speed or climbing the gradient, there is a need to insulate the engine heat to be transferred to other parts around it. , eg Engine Installation. With the help of proper thermal analysis and the use of heat shield, engine mounting vents can be optimized for best performance.
Space
Spacecraft that land on planets with atmospheres, such as Earth, Mars, and Venus, are currently doing so by entering the atmosphere at high speed, depending on air resistance rather than rocket power to slow them down. The side effects of this atmospheric re-entry method are aerodynamic heating, which can severely damage the structure of spaces that are unprotected or damaged. The aerodynamic heat shield consists of a protective layer of a special material to remove heat. Two basic types of aerodynamic heat shield have been used:
- The ablative heat shield consists of a layer of plastic resin, an outer surface heated to a gas, which then carries the heat away by convection. Such shields are used on the Mercury spacecraft, Gemini, and Apollo.
- Thermal seam heat shields use insulating materials to absorb and radiate heat from the structure of the spacecraft. This type is used in the Space Shuttle, which consists of ceramic or composite tiles on most of the vehicle surface, with carbon-carbon material being reinforced at the highest thermal load point (nose and wing tip). This material damage to the wing caused the Space Shuttle Columbia 2003 disaster.
Some spacecraft also use a heat shield (in the sense of conventional automotive) to protect fuel tanks and equipment from heat generated by large rocket engines. Such shields are used in the Apollo Service Module and Lunar Module descent phases.
Industry
The heat shield is often affixed to semi-automatic or automatic rifles and rifles as a barrel shell to protect the user's hands from heat caused by a shot shot in rapid succession. They are also often affixed to the action-action gun rifle, which allows soldiers to understand the barrel while using bayonets.
See also
- Van Allen radiation belt
- Aeroshell
- The process of reentering the atmosphere
- AVCOAT
- Sunshield (JWST)
References
Source of the article : Wikipedia
0 Comments