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 Management of an Avionics Module Using Solid-Liquid Phase-Change Materials
A combined experimental and computational investigation of transient thermal control of an avionics module using phase-change material (PCM) is reported. The cone guration examined was a honeycomb core e lled with an organic PCM, n-triacontane, heated from the bottom. Experiments were conducted to evaluate the thermal performance of the PCM device by measuring temperatures at various locations as functions of time until the module temperature reached an acceptable maximum limit. An analysis of melting inside a single honeycomb cell, considering effects of natural convection, showed that, for the power levels and the cell geometry considered, the effect of natural convection on melting was negligible. A system-level analysis of the PCM-e lled device followed. Timewise variations of temperatures at various locations from the model were in good agreement with the experimental data. Times for complete melting, maximum temperature variations within the honeycomb, and evolution of melt shapes are presented as functions of power levels.
THERMAL MANAGEMENT USING “ DRY ” PHASE CHANGE MATERIALS
The thermal response characteristic of a hybrid cooler that is charged with a “dry” solid-solid phase change compound is evaluated. A mathematical model that simulates the performance of a cooler/heat storage unit is formulated. A prototype heat sink that incorporates heat storage using a “dry” PCM is tested, and used to benchmark the simulation model. Different heating and cooling strategies are evaluated and a figure of merit, characteristic of the cooler/PCM under development is introduced.