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.
TED-AJ03-359 A POLYMER-BASED THERMAL ENERGY STORAGE COMPOSITE FOR TEMPERATURE CONTROL OF SENSORS AND ELECTRONICS
A novel lamination that consists of aluminum heat spreader plates interspersed with a polymer-based thermal energy storage composite is described. The composite consists of a thermoplastic matrix that encapsulates paraffin such that it is immobilized when in the liquid phase. As a consequence, the thermal energy storage/release process is independent of g-loading or orientation. Composites with paraffin mass fractions as high as 80% have been formulated. When combined with a suitably designed heat input/spreader mechanism, the resulting lamination is a responsive and compact thermal energy storage element. The fabrication methodology and thermal characteristics of the polymer composite are described. Hermeticity testing at elevated temperatures, and durability testing of the composite and its bond to aluminum heat spreader plates in repeated thermal cycling across the paraffin phase transition is documented. A thermal model of the heat storage/release process is developed and used to optimize the design of plate-like laminations. Prototype TES-systems are fabricated and tested to benchmark the thermal performance model.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.