Thermal and Mechanical Characteristics of a Multifunctional Thermal Energy Storage Structure
Thermal energy storage (TES) sandwich-structures that combine the heat storage function with structural functionality are described. The structure consists of a thermal interface (TI) connected to a hollow plate lamination. Each laminate is a hollow aluminum plate having a series of mm-scale channels or compartments that are filled with phase change material (PCM). Heat storage is via the latent heat of the PCM. A generalized thermal response model that is applicable to a wide range of channel geometrical configurations is described. The model couples the thermal response of the TI to the hollow aluminum plate/PCM-volume. The temporal response of the system is easily obtained via numerical solution of two ordinary differential equations, which can be solved to give closed-form solutions subject to a simple assumption. Thermal analysis delineates geometrical configurations that have good thermal response characteristics. The mechanical properties of the laminated structure are determined experimentally. Four-point bending experiments are conducted using specimens made with three layers of hollow plates laminated using a structural adhesive. An energy method is developed to model both the deformation and strength of the laminated structure. The energy method is developed based on the assumption that plane cross sections of the structure remain plane under bending, a condition that is valid for both linear and nonlinear materials. The energy method can provide deformation of the aluminum laminates comparable with the experiments. Experiments and modeling indicate that these laminated structures have an excellent performance-to-weight ratio.
Thermal Characteristics of a Compact, Passive Thermal Energy Storage Device

 A Thermal Energy Storage (TES) system uses a Phase Change Material (PCM) to store heat during peak power operation of variable power dissipating devices via the latent heat effect. The TES composite developed is a plate-like structure that consists of a central core of foamed aluminum that is packed with a PCM. By considering the elements of the composite to be thermal resistors and constructing a flat-plate thermal conductivity apparatus, the plate-to-plate effective thermal conductivity is determined. The composite effective thermal conductivity is primarily composed of the thermal conductivity of the aluminum foam which is reduced by the effect of the aluminum foam-to-plate bond resistance. Heat flow through the PCM slightly augments the effective thermal conductivity. An increase in aluminum foam metal fraction results in an increase in the effective thermal conductivity of the composite because only about 2% of the heat flow is through the PCM, and the interfacial bond resistance decreases due to increased contact area. The trade-off is that as there is an increase in aluminum foam metal fraction, the volumetric latent heat decreases; thus, the storage time is reduced.
Evaluation of Lapping Grains based on Shape Characteristics.
The shape and size of abrasive grains during lapping varies complicately and irregularly. In this study, the aspect ratio of grain size and the fractal dimension of the grain external form were used as shape characteristics of grain in order to evaluate grains with lapping time. The results obtained are summarized as follows : (1)The fractal dimension increases due to microscopic fracture and decreases due to macroscopic fracture or attritious wear. (2)The aspect ratio and the fractal dimension, which are grain shape characteristicsis of the macroscopic shape and the microscopic surface complication of grain respectively, can be used for evaluating grain shape variation during lapping.