Solar thermal energy application to dry reforming of methane on the open-cell foam to enhance the energy storage efficiency of a thermochemical fluidized bed membrane reformer: modelling and simulation

The hydrodynamic characterization of the solar-driven CO2 reforming of methane through b-SiC open-cell foam in a fluidized bed configuration is performed by reacting Methane (CH4) with carbon dioxide (CO2). The mathematical modelling is important to design and optimize the reforming methods. Usually, the reforming methods's application through b-SiC foam bed improves the heat transfer and mass transfer due to high porosity and surface area of the b-SiC foam. Fluidized Bed Membrane (FBM) Reformers can be substantially studied as a promising equipment to investigate the thermochemical conversion of CH4 using CO2 to produce solar hydrogen. This work has as main objective a theoretical modelling to describe the process variables of the solar-driven CO2 reforming of methane in the FBM reformer. The FBM reformer is filled with b-SiC open-cell foam where the thermochemical conversion is carried out. The model variables describe the specific aims of work and these objectives can be identified from each equation of the developed mathematical model. The present work has been proposed to study two specific aims as (i) The effective thermal conductivity's effect of the solid phase and (ii) molar flows of chemical components. The endothermic reaction temperature's profiles are notably increased as the numeral value of the effective thermal conductivity's effect of the solid phase. is rised. The solar-driven CO2 reforming method is suggested to improve the Production Rate (PR) of H2 regarding the PR of CO.

A numerical method based on domain decomposition to solve coupled conduction-radiation physics using parallel computing within large porous media

A domain decomposition approach is developed to solve coupled conductive– radiative heat transfer within highly porous materials. In this work, a Kelvin–cell foam with five cells in each direction which has ˇ15.6 × 106 of voxels is considered. The coupled heat transfer is solved using the finite volume method where deterministic ray tracing is used to calculate radiative exchange. The temperature distribution is computed and cross–validated with the distribution obtained using a commercial software STAR–CCM+.

Temperature dependency of the long-term thermal conductivity of spray polyurethane foam

The thermal properties of closed-cell foam insulation display a more complex behaviour than other construction materials due to the properties of the blowing agent captured in their cellular structure. Over time, blowing agent diffuses out from and air into the cellular structure resulting in an increase in thermal conductivity, a process that is temperature dependent. Some blowing agents also condense at temperatures within the in-service range of the insulation, resulting in non-linear temperature dependent relationships. Moreover, diffusion of moisture into the cellular structure increases thermal conductivity. Standards exist to quantify the effect of gas diffusion on thermal conductivity, however only at standard laboratory conditions. In this paper a new test procedure is described that includes calculation methods to determine Temperature Dependent Long-Term Thermal Conductivity (LTTC(T)) functions for closed-cell foam insulation using as a test material, a Medium-Density Spray Polyurethane Foam (MDSPF). Tests results are provided to show the validity of the method and to investigate the effects of both conditioning and mean test temperature on change in thermal conductivity. In addition, testing was conducted to produce a moisture dependent thermal conductivity function. The resulting functions were used in hygrothermal simulations to assess the effect of foam aging, in-service temperature and moisture content on the performance of a typical wall assembly incorporating MDSPF located in four Canadian climate zones. Results show that after 1 year, mean thermal conductivity increased 15%–16% and after 5 years 23%–24%, depending on climate zone. Furthermore, the use of the LTTC(T) function to calculate the wall assembly U-value improved accuracy between 3% and 5%.

Microstructural and Chemical Analysis of Polyurethane and Polyisocyanurate Foam Insulations

For some closed cell foam insulation products, the thermal conductivity increases at low temperatures, contrary to single thermal resistance values provided by manufacturers. This phenomenon has been demonstrated in various polyurethane and polyisocyanurate insulations. The reduction in thermal performance has been attributed to the diffusion of air and blowing agent through the foam and to the condensation of blowing agent. Aging processes such as freeze-thaw cycling, moisture accumulation, and polymer degradation further increase thermal conductivity. The initial cell structure plays a role in dictating the thermal performance. To further understand the loss of thermal performance in closed cell foams, microstructure and chemical characterization was performed in this study. The aging behavior of foam insulations was analyzed by imaging foams with SEM and by measuring foam. Changes in the polymer physical attributes were identified and compared to increases in thermal conductivity. This project also used gas chromatography and quantified changes in pentane concentration in polyisocyanurate foams that have undergone aging