Thermal modeling with solid/liquid phase change of the thermal energy storage experiment
A thermal model which simulates combined conduction and phase change characteristics of thermal energy storage (TES) materials is presented. Both the model and results are presented for the purpose of benchmarking the conduction and phase change capabilities of recently developed and unvalidated microgravity TES computer programs. Specifically, operation of TES-1 is simulated. A two-dimensional SINDA85 model of the TES experiment in cylindrical coordinates was constructed. The phase change model accounts for latent heat stored in, or released from, a node undergoing melting and freezing.
A dynamic thermal insulator: Inducing resonance within a fluid saturated porous medium enclosure heated periodically from the side
Abstract This theoretical and numerical study investigates the natural convection flow within a fluid saturated porous medium enclosure subjected to intermittent heating from the side (hot wall). A theory for predicting the natural convection frequency of the flow wheel circulating inside the enclosure is developed from the general porous medium equations on a scaling basis. Physical insight indicates that heat flow resonance might occur when the input heat frequency matches the flow wheel circulating frequency. Numerical simulations confirm the existence of a preferred (resonance) input heat pulsating frequency. They also reveal that at the resonance frequency the fluid saturated porous medium system behaves as a dynamic thermal insulator in which the strong natural convection activity within the system, characterized by high amplitude heat flow oscillations, coexists with a damped oscillatory heat flux at the isothermal (cold) wall.
Effect of stress conditions on collapse deformation behavior of a rockfill material
A set of saturated and dry-saturated large-scale triaxial tests were conducted in order to explore the effects of stress conditions on the saturation-induced collapse deformation behavior of a rockfill material. Specimens were tested in different confining pressures and for dry-saturated tests the specimens were submerged in various shear stress levels. The results indicate that in all of the dry-saturated tests a sudden reduction in the volume of the specimens was observed during the submerging process. The ratio of the minimum axial strength of a submerged specimen (at the end of the saturation process) to the shear strength of the specimen before saturation is defined as the coefficient of stress recovery, Csr. Results of the dry-saturated tests showed that this ratio increases as the confining pressure increases and decreases by increasing the shear stress level. According to the results of dry-saturated tests the values of internal friction angle reduction caused by saturation (Δϕc), the ratio of the elasticity modulus of the material after saturation to its elasticity modulus in dry condition, i.e., Ewet/Edry, and also the saturation induced sudden volumetric strain (εvc) decrease as the confining pressure increases. However the shear stress level does not have any meaningful effect on the variation of Dfc, Ewet/Edry and (εvc).