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Applications of Radiation Energy Transfer
Published in John R. Howell, M. Pinar Mengüç, Kyle Daun, Robert Siegel, Thermal Radiation Heat Transfer, 2020
John R. Howell, M. Pinar Mengüç, Kyle Daun, Robert Siegel
Spacecraft re-entry into planetary atmospheres causes extreme frictional heating. Heat shields, like the one shown in Figure 19.13, protect the spacecraft payload through a combination of ablation of the heat shield surface and very low thermal conductivity of the shield material. Radiation and convection from the ablative surface must also be considered, and the radiation from the shock layer preceding the ablating surface is complicated by the presence of many ablated species, thermal nonequilibrium in the gas, and the coupled chemistry and fluid mechanics (Lamet et al. 2008, Bauman et al. 2011Bansal et al. 2011, Howell 2014). Thermal barrier coatings (TBCs) are used to protect turbine blades and some spacecraft re-entry bodies. Their formulation, property measurement, and conduction/radiation analysis has led to broader adoption (Delmas et al. 2014).
Multidimensional and Unsteady Conduction
Published in Anthony F. Mills, Heat and Mass Transfer, 2018
Ablative heat shields are widely used to protect structures from high heat fluxes. Heat shields are made from a great variety of materials, including refractory metals such as tungsten, Teflon, graphite, and silica-phenolic composites. The heat transfer analysis of a simple melting ablator is straightforward if it can be assumed that the liquid melt is removed as fast as it is formed. On a reentry vehicle, the friction and pressure forces will cause the melt to flow backward over the vehicle, leaving only a thin film of negligible thermal resistance. The heat shield in Fig. 3.29 shows evidence of undergoing melting ablation. Alternatively, in some situations, gravity forces may be sufficient to ensure that the liquid drains quickly from the solid surface.
Implementation of Nanotechnology in the Aerospace and Aviation Industry
Published in Cherry Bhargava, Amit Sachdeva, Pardeep Kumar Sharma, Smart Nanotechnology with Applications, 2020
Rameela Davanagere Ramesh, Anusha Santhosh, Sarath Raj Nadarajan Assari Syamala
Heat shields are designed as brakes of the spacecraft that prevent the overheating of the spacecraft by either absorbing, reflecting, or dissipating heat. This, in turn, prevents the spacecraft from crashing while it is re-entering the earth’s atmosphere. Nanomaterials are essential for this process. The Mars Science Laboratory (MSL) spacecraft, which carried Curiosity, went through the most extreme atmospheric entry that ever took place. MSL was protected by a lightweight, thin, carbon-based heat shield material. This material is known as PICA [Phenolic Impregnated Carbon Ablator] and is widely used for heat shields by National Aeronautics and Space Administration (NASA) as well as Space Exploration Technologies Corporation (SPACEX) [30].
Thermal Analysis on Various Design Concepts of ITER Divertor Langmuir Probes
Published in Fusion Science and Technology, 2018
L. Chen, W. Zhao, G. Zhong, C. Watts, James P. Gunn, X. Liu, Y. Lian
The volumetric nuclear heating caused by neutron irradiation is 6.5 MW/m3 in tungsten and 1.5 MW/m3 elsewhere. The temperature of 100°C and pressure of 3 MPa are specified for the coolant water in the tube of the monoblock. The heat load into the gap between the probe sensor and the shield is ignored. For the thermal radiative heat transfer from the tungsten surface to the ITER fusion environment, the emissivity coefficient is assumed to be 0.2 for the tungsten material, and the probe body temperature is 100°C. The thermal contact conductance applied on the bolted interface of the copper heat shield and the CuCrZr heat sink is 3000 W/m2·K, while the TCC value between the probe sensor, ceramic electrical insulator, and heat shield was 10 000 W/m2·K.
Exploring ideality and reality in an archetypal rodlike nematic liquid crystal
Published in Liquid Crystals, 2020
Louis A. Madsen, Theo J. Dingemans, Chi-Duen Poon, Edward T. Samulski
We modified a broadband solids (X) probehead (Bruker-Biospin, Billerica, MA), as shown in Figure 11, This high temperature oven is capable of up to 450°C (720 K) operation with no need for active cooling of the probehead. Fumed-silica tile as used on the outer hull of NASA’s Space Shuttle comprises the insulating walls of our oven, and a skin of aluminium foil (heat shield) attached with ceramic cement (Omega 600 High T Cement) reduces radiative losses to keep the outer shell below 70°C. The cylindrical oven is 6.5 cm tall by 6.5 cm diameter with a 1.4 cm minimum wall thickness. The spectrometer’s variable temperature controller (Bruker BVT 3000) drives a ~ 4 Ohm nichrome heating coil (Omega Ni80-012, 300 µm diam. wire), and reads temperature using a type-E thermocouple (Omega) situated within 4 mm of the sample edge. The base of the nichrome heating coil and the thermocouple is held by cement to the oven base after punching them through the tile. At 400°C, the temperature precision is ±0.2°C and the spread over a 3 mm diameter sample is ≅2°C. Sample equilibration after setpoint changes of <10°C occurs in <2 min. The NMR RF coil consists of a 13 turn tin-plated 22 gauge copper wire tuned to 2H frequency (55.2 MHz), wound to produce an inside diameter of 5.5 mm. We punch the RF coil leads through the silica tile before soldering to the SMA connector plugs that interface with the Bruker probe electronics, and prior to cementing the leads to the tile surface on the inside and prior to attachment of the outer aluminium heat shield. The upper oven assembly (walls and top – see Figure 11) is held down to the main probe body by ordinary rubber bands looped around small screws on the sides of the Teflon® probe base. The probe assembly enables observed 2H linewidths of <30 Hz FWHM, with shimming done in the isotropic phase with proton signals before recording LC-phase spectra.