Determination of Thermal Stress Effect on Slip Flow in Micro-particle Photopheresis in Gaseous Media | Chapter 1 | Current Perspective to Physical Science Research Vol. 6

This chapter presents a study on photophoresis of a microparticle in gaseous media with focus on the effect of thermal stress slip, which is deemed as one of factors causing deviations of previous theoretical predictions from measurements. The present modified theory exhibits an effective agreement with the measurements and highlights the importance of the thermal stress slip in photophoresis of a particle, particularly one with a small radius when combined with an analysis of one order of magnitude. A schematic diagram of an isotropic homogenous particle suspended in a gas medium with a monochromatic, parallel, and linearly polarized light beam along the z direction has introduced in this chapter. The theoretical expressions combined with an order-of magnitude analysis demonstrate the significance of the thermal stress slip in micro-particle photophoresis and disclosed the reason for deviation of the previous theory at small particle size. Parametric analysis revealed that the influence of thermal stress becomes more pronounced with a reducing particle thermal conductivity and/or increasing Knudsen number.

Author(s) Details:

Chyi-Yeou Soong,
Department of Aerospace and Systems Engineering, Feng Chia University, Seatwen, Taichung-40724, Taiwan, ROC.

Wen-Ken Li,
Department of Mechanical Engineering, Chung Yuan Christian University, Zhongli, Taoyuan-320314, Taiwan, ROC.

Chung-Ho Liu,
Department of Biomedical Engineering, Yuanpei University, Hsinchu-30015, Taiwan, ROC.

Pei-Yuan Tzeng,
Department of Mechanical and Aerospace Engineering, Chung-Cheng Institute of Technology, National Defense University, Taoyuan-33509, Taiwan, ROC.

Please see the link here: https://stm.bookpi.org/CPPSR-V6/article/view/13247

Thermal Deformation and Strength of Materials for Heat-shielding Coatings of a Spacecraft on the Trajectory of Descent from Orbit| Chapter 8 | Techniques and Innovation in Engineering Research Vol. 2

 The basis for a fundamental understanding of the process of material interaction with a medium is the agreement between experimental research and the actual operating conditions of a specific model or structure. Thermal Shield Materials (TSMs) are designed based on certain requirements, such as the characteristics of heating and material destruction under the least amount of shield weight. The more useful space load it can give, the lighter it must be. Since the thermal shield serves as a missile's ballast weight, it is only natural to want to lower the weight of TSMs without sacrificing their capacity to reliably perform their thermal shield role. Utilizing calculations based on the physical characteristics of materials discovered during conditions replicating a spacecraft's re-entry into the atmosphere, the performance of thermal shield structures was examined. The dependence of the temperature T of a thermal shield side surface on the period of descent in dense air layers serves as the basis for physical modelling of the natural conditions of thermal shield use (temperature, heating/cooling rate, composition, and pressure of gas medium). A thermal barrier was made composed of a laminated fibreglass shell with a phenol-phormaldehyde matrix. Investigations were done on temperature-dependent mechanical and thermophysical characteristics. By using numerical analysis, elasticity theory, and thermal conductivity equations to solve a 3D problem, it is possible to characterise the thermally stressed state of a cylindrical shield that is being impacted by a high-temperature gas flow. According to the results, the maximum compression stresses in a fibreglass thermal shield shell are located close to the heated surface and are not higher than the material's strength limit at that temperature. A new, 30% lighter thermal protection system for the re-entry vehicle was proposed and put into practise as a result of the experimental and theoretical investigations that were conducted.

Author(s) Details:

Lyudmila I. Gracheva,
G. S. Pisarenko Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev - 01014, Ukraine.

Please see the link here: https://stm.bookpi.org/TAIER-V2/article/view/8276

Discussion on Formula of Thermogradient Effect | Chapter 4 | Recent Developments in Engineering Research Vol.4

 

This current paper attempts for formulation of empiric formula, which establishes relations between
major matrix parameters of ceramic materials and composites and the coefficient of resistance to
material thermogradient. It has been proved that work-pieces reveal maximum thermal resistance and
preservation of exploitation properties, when total closed porosity is within 2% - 8%, and pore sizes
vary within 1 - 6 mcm. Besides, they are more or less of spherical form and are spread equally in the
matrix. Thermo-gradient effect formula was defined for complex form work-pieces, when surfaces in
the pieces are transacted several times by angles of various curvature radii.

Author (s) Details

Zviad Kovziridze
Georgian Technical University, Institute of Bionanoceramics and Nanocomposites Technology, Tbilisi, Georgia.

View Book :- https://bp.bookpi.org/index.php/bpi/catalog/book/263