Detection of flaws in a two-dimensional body through measurement of surface temperatures and use of conjugate gradient method

This paper aims to obtain parameters (i.e. location and dimensions) relevant to flaws in a two-dimensional body by measuring the temperature on its boundaries. In this endeavour, a steady-state heat conduction problem is formulated, and the geometry under study is subjected to a known heat load, resulting in a specific heat distribution in the body. By using a number of heat sensors, the temperature at selected points on the boundary of the body is obtained. Inverse heat conduction methods implement these temperature data, working toward estimating the flaw parameters. The objective function is optimized using conjugate gradients method, and in solving the direct problem, an FEM code is employed. To check the effectiveness of this method, sample cases with one or more circular, elliptical cavities or cracks in the body, and a case with unknown cavity shape is solved. Finally the ensuing results analyzed

Fluidization and packed bed behaviour in capillary tubes

Packed and fluidised beds in microfluidic devices offer the potential of enhanced heat and mass transfer capability at a scale where the process can be closely controlled. The knowledge of hydrodynamics of packed and fluidized beds in capillary tubes is essential for the design and optimization of such devices. This study experimentally examines the hydrodynamics of packed and fluidized beds in terms of pressure drop, bed expansion and minimum fluidization velocity in tube sizes with inner diameters of 0.8, 1.2 and 17.1 mm. Specifically the effect of particle-wall interaction on the hydrodynamic characteristics of the beds was examined by changing the tube-to-particle diameter ratio. It was found that as the tube diameter reduces the bed voidage sharply increases leading to a reduction in the pressure drop across the bed. Also a distinctive rise in pressure drop was observed at lower tube-to-particle diameter ratios which are found to be associated with the particle-wall interaction

Progress in heat transfer research for high-temperature solar thermal applications

High-temperature solar thermal energy systems make use of concentrated solar radiation to generate electricity, produce chemical fuels, and drive energy-intensive processing of materials. Heat transfer analyses are essential for system design and optimisation. This article reviews the progress, challenges and opportunities in heat transfer research as applied to high-temperature solar thermal and thermochemical energy systems. The topics discussed include fundamentals of concentrated solar energy collection, convective heat transfer in solar receivers, application of liquid metals as heat transfer media, and heat transfer in non-reacting and reacting two-phase solid–gas systems such as particle–gas flows and gas-saturated porous structures. © 2020 Elsevier Ltd