Experimental Study on the Influence of Foam Porosity and Pore Size on the Melting of Phase Change Materials

Experimental study was carried out to study the phase change heat transfer within a composite of phase change material (PCM) infiltrated high thermal conductivity foam. An experimental setup was built to measure the temperature profiles and capture the melting evolution of the PCM inside aluminum foams. Aluminum foams were used as the porous material, and low melting temperature paraffin wax was used as the PCM. It was observed from the results that the system parameters of the wax/foam composite had a significant influence on its heat transfer behavior. By using higher porosity aluminum foam, the steady-state temperature was reached faster as compared to the foams with lower porosity. Similarly for the bigger pore size foams the steady state was attained faster as compared to the smaller pore size foams. This was due to the greater effect of convection in both the higher porosity and bigger pore size foams. However, for the lower porosity foams the heater temperature was comparatively lower than the higher porosity foams due to greater heat conduction through the foam material. Therefore, an optimal value should be selected for the foam porosity and pore size such that the effects of both conduction and convection heat transfers can be completely utilized to have a greater and improved thermal performance for the wax/aluminum foam composite

Studying The Performance Of Solid/Perforated Pin-Fin Heat Sinks Using Entropy Generation Minimization

Heat transfer and pressure drop characteristics of a set of pin-fins with uniform heat flux were investigated experimentally and numerically. Test set-up was designed to assess the effects of mass flow rate, fin height, and fin density on convection heat transfer and pressure drop. In the numerical investigation, the flow field of various design parameters of the heat sink was simulated. It was found that heat sinks having fin heights of 20 and 30 mm operated at a lower Reynolds number reached minimum value for thermal resistance when the fin density 10 × 10. Which means it is the optimum number of fins for this case. Also, friction factor increased with a decrease in the bypass flow area or inter-fin distance spacing and using perforated fins reduced the pressure losses and thermal resistance for all studied cases

Numerical and Experimental Investigations of Melting and Solidification Processes of High Melting Point PCM in a Cylindrical Enclosure

In the present work, a computational model is developed to investigate and predict the thermal performance of high melting point phase change material during its melting and solidification processes within a cylindrical enclosure. In this model the phases are assumed to be homogeneous and a source term, S, arises from melting or solidification process is considered as a function of the latent heat of fusion and the liquid phase fraction. The numerical model is verified with a test problem and an experiment is performed to assess the validity of the assumptions of it and an agreement between experimental and computational results is achieved. The findings show that utilizing of PCMs of high melting points is a promising technique especially in space applications

Merits of Employing Foam Encapsulated Phase Change Materials for Pulsed Power Electronics Cooling Applications

In the present work, the potential of using foam structures impregnated with phase change materials (PCMs) as heat sinks for cooling of electronic devices has been numerically studied. Different design parameters have been investigated such as foam properties (porosity, pore size, and thermal conductivity), heat sink shape, orientation, and use of internal fins inside the foam-PCM composite. Due to huge difference in thermal properties between the PCM and the solid matrix, two energy equation model has been adopted to solve the energy conservation equations. This model can handle local thermal nonequilibrium condition between the PCM and the solid matrix. The numerical model is based on volume averaging technique, and the finite volume method is used to discretize the heat diffusion equation. The findings show that, for steady heat generation, the shape and orientation of the composite heat sink have significant impact on the system performance. Conversely, in the case of power spike input, use of a PCM with low melting point and high latent heat is more efficient

Graphite Foams Infiltrated with Phase Change Materials as Alternative Materials for Space and Terrestrial Thermal Energy Storage Applications

In this work, a numerical study is proposed to investigate and predict the thermal performance of graphite foams infiltrated with phase change materials, PCMs, for space and terrestrial energy storage systems. The numerical model is based on a volume averaging technique while a finite volume method has been used to discretize the heat diffusion equation. A line-by-line solver based on tri-diagonal matrix algorithm has been used to iteratively solve the algebraic discretization equations. Because of the high thermal conductivity of graphite foams, the PCM-foam system thermal performance has been improved significantly. For space applications, the average value of the output power of the new energy storage system has been increased by more than eight times. While for terrestrial applications, the average output power using carbon foam of porosity 97% is about five times greater than that for using pure PCM

Graphite Foams Infiltrated with Phase Change Materials as Alternative Materials for Space and Terrestrial Thermal Energy Storage Applications

In this work, a numerical study is proposed to investigate and predict the thermal performance of graphite foams infiltrated with phase change materials, PCMs, for space and terrestrial energy storage systems. The numerical model is based on a volume averaging technique while a finite volume method has been used to discretize the heat diffusion equation. A line-by-line solver based on tri-diagonal matrix algorithm has been used to iteratively solve the algebraic discretization equations. Because of the high thermal conductivity of graphite foams, the PCM-foam system thermal performance has been improved significantly. For space applications, the average value of the output power of the new energy storage system has been increased by more than eight times. While for terrestrial applications, the average output power using carbon foam of porosity 97% is about five times greater than that for using pure PCM

The Effect of Surface Energy on the Heat Transfer Enhancement of Paraffin Wax/Carbon Foam Composites

The influence of carbon foam surface energy on heat transfer through paraffin wax/carbon foam composite was investigated. Carbon foam samples were surface treated and their corresponding surface energy values were measured. A theoretical model was formulated to analyze the mass of paraffin wax absorbed for both pristine and surface activated carbon foam samples based on the concept foam wettability. An experimental study was carried out for heating of the wax/carbon foam composite samples to study the phase change heat transfer due to the melting of wax within the foam matrices. The above studies showed that a greater mass of wax was absorbed within the activated carbon foam samples as compared to the pristine sample which can be due to their greater wettability. This resulted in an improvement in heat transfer rate for the activated samples. The total energy storage rate for the activated composite samples was compared with the pristine sample for the same heating duration and an enhancement of more than 18% was observed for the two activated samples. These studies revealed that the surface energy of carbon foams can play an important role in improving the overall thermal performance of wax/carbon foam composites