Carbon Foam Matrices Saturated with PCM for Thermal Protection Purposes

Publisher Summary Melting and freezing are important processes and these processes have played a decisive role in the formation of the Earth. This phase-change phenomena have become an indispensable part of many processes, such as, manufacturing of glass, crystals, and metal alloys; continuous casting of ingots, fabrics, and wires; food preservation and cryopreservation of biological cells; and desalination of seawater and freezing-out separation processes. This chapter reviews the current knowledge on phase-change phenomena, with particular focus on phase-change problems from solid to liquid or to gas. Because of their simplicity, one-dimensional, phase-change problems involving conduction heat transfer are the most frequently used model problems for the development of solution methods. This chapter begins with the consideration of such one-dimensional methods, either exact or approximate, which have been widely used in the literature. The substantial information about the physics of phase-change processes that can, in fact, be learned from studies of these simple models is discussed. The multidimensional conduction phase-change problems as well as the additional physics attributable to geometrical complexities are also reviewed.

Melting and Freezing

Solid-liquid phase-change heat transfer and interface motion in materials cooled or heated from above or below

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 of an Avionics Module Using Solid-Liquid Phase-Change Materials

Photographic observation of the solid-liquid interface motion during melting of a solid heated from an isothermal vertical wall

An approximate mathematical model was established for the melting of a finite paraffin slab, a problem of interest for phase-change thermal control devices. The method is based on the numerical computer solution of the two-phase, one-dimensional heat-conduction equations with moving interface and variable thermal properties in both the solid and liquid regions. Results from the theoretical model are compared with experimental results for n-octadecane in a bellows-type test cell, and with information published in the literature. The numerical analysis appears to provide a good rigorous treatment of the unidimensional melting problem in an idealized model.

Melting of a finite paraffin slab as applied to phase-change thermalcontrol.

Gravity induced free convection effects in melting phenomena for thermal control, predicting temperature distributions and solid-liquid interface profiles by two dimensional model

Gravity-Induced Free Convection Effects in Melting Phenomena for Thermal Control

Phase change solidification phenomena in n- hexadecane for spacecraft thermal control systems, considering two or three dimensional models

Phase change solidification dynamics

The study presents one method of mathematically modeling the effects of gravity-induced free convection upon the melting phenomena of a finite paraffin slab The theoretical model is based on the numerical computer solution of the solid phase and liquid phase energy equations, coupled with an imposed ideal-viscous flow approximation An implicit alternating-direction technique is used as the finite-difference approximation for the basic energy equations in the numerical solution The theoretical predictions are compared to experimental data from an annular test cell, in which n-octadecane, C18H38, was used as the test material The results show that the model is a good first approximation to the solution of solid-liquid phase change involving gravity-induced free convection

Liquefaction dynamics of n-octadecane in cylindrical coordinates

T HE use of phase change material (PCM) as a thermal control technique has been proposed for many spacecraft applications, including planetary descent probes. Although many promising PCMs have been identified during previous studies, the data required to design a minimum weight PCM device is lacking. A development program was initiated to obtain practical design information, starting with PCMs and container concepts previously identified. This paper discusses the results of an experimental investigation, including the PCM selection, container design, test setup, data analytical correlation and problem areas.

J. O. Golden

Papers

Melting of a finite paraffin slab as applied to phase-change thermalcontrol.

Gravity-Induced Free Convection Effects in Melting Phenomena for Thermal Control

Phase change solidification dynamics

Liquefaction dynamics of n-octadecane in cylindrical coordinates

Development of a Phase Change Thermal Control Device