Asian Journal of Physical and Chemical Sciences

Numerical Study of the Thermal Behavior of a Hollow Block with Phase Change Materials (PCM) in the Sahelian Zone

Thu, 05 Jan 2023 00:00:00 +0000

In this work, we present a numerical study of the thermal behavior of a hollow block with or without phase change material (PCM) in the Sahelian zone.

The PCMs used in this study are RT27 paraffin and hydrated salt with a melting temperature of 27°C and 29.9°C respectively and a latent heat of fusion of 179kJ/kg and 184kJ/kg. The equations obtained were adimensionalized then discretized by the finite element method and solved on the COMSOL software. We were first interested in the study of the thermal phase shift, the damping and the evolution of the temperature at the level of the internal wall. In a second phase, we conducted a comparative study between hollow block containing PCM and other construction materials (adobe, BTC and BLT) used in Burkina Faso.

The numerical results obtained show that the temperature of the internal wall of a hollow block containing RT27 is lower than that of a hollow block without PCM, hollow block containing hydrated salt, BTC, BLT and adobe with respectively a temperature difference of 8.354°C; 3.39°C; 5.79°C; 3.97°C and 3.92°C and the difference in terms of phase shift is 1h18min, 6min, 24min, 42min and 6min for the hollow block containing RT27, the hollow block containing hydrated salt, BTC, BLT and adobe.

Therefore, the integration of PCM in building materials increases their thermal inertia.

Influence of Thickness of the Porous Layer on Thin Film Condensation in Forced Convection in a Canal Whose Walls are Covered with a Porous Material: Determination of Lengths of Entry

Wed, 08 Mar 2023 00:00:00 +0000

We have examined film condensation in a channel whose walls are covered with porous media numerically. The transfers in the porous medium and the liquid film are respectively described by the Darcy-Brinkman-Forchheimer model and the equations of the hydrodynamic and thermal boundary layers and are solved by the decentered implicit finite difference method and the iterative Gauss-Seidel method.

After validating, the influence of the thickness of the porous layer on the longitudinal velocity and the temperature profiles in both media (pure liquid and porous medium), the thickness of the liquid film, the local Nusselt number and the lengths of entry have been studied.

We note that an increase in the thickness of the porous layer increases the friction and decreases the contact of the fluid with the cold plate and allows a decrease in the longitudinal velocity and an increase in the temperatures in the porous medium and the pure liquid, a decrease liquid film thickness (disadvantaged condensation) and increases the local Nusselt number and also an increase in the length of entry. The increase in length of entry is quasi-linear. The sensitivity of condensation to a change in thickness of the porous layer is constant.

Processing and Characterization of Iron Oxide Nanoparticle Produced by Ball Milling Technique

J. N. Nwauzor , A. J. Ekpunobi , A. D. Babalola — Tue, 21 Mar 2023 00:00:00 +0000

In this study iron oxide (Fe₂O₃) nanoparticle samples was prepared using mechanical grinding method. The optical properties were studied using UV-Vis spectrophotometer within a range of 200-1100nm. The micro and crystalline size of the nanoparticle were studied using x-ray diffractometer (XRD) and scanning electron microscopy (SEM). The compositional analysis was carried out using energy dispersive x-ray spectroscopy (EDXS). Observation of the electrical properties of the nanoparticle was carried out using an electrical four-point probe system. The XRD pattern in the 2θ range from 20 to 70⁰ revealed that iron oxide had a rhombohedral structure. The SEM result showed that the nanoparticles were well dispersed and had a uniform crystalline structure. The EDXS results showed the elemental analysis of the nanoparticles under consideration. Iron oxide nanoparticles had elemental composition of oxygen, iron, titanium and carbon. The atomic and weight concentration of iron was 14.19 and 30.89%. The four-point probe electrical resistivity result shows that iron oxide nanoparticles had a sheet resistance of 9.8x10⁶Ώ/sq. The optical result made it known that iron oxide nanoparticles possessed a high transmittance, also iron oxide nanoparticles displayed a low reflectance and moderate absorbance. Finally, the bandgap energy of Fe₂O₃ dispersed in ethanol was found to be 2.74 eV. The Band gap of Fe₂O₃ dispersed in distilled water is 2.98 eV.

Evaluation of Health Risk Due to Exposure to Radiation in Some Hospitals in Rivers State

A. Bubu , C. P. Ononugbo — Sat, 25 Mar 2023 00:00:00 +0000

An external background ionization radiation was carried out in Our Lady Health of the sick hospital, Colworth Medical and Olive Tree Medical Diagnostics Port Harcourt. The background radiation reading was taken using the radiation alert meter (Digilert 200). The estimated value for the excess lifetime cancer risk from the three hospitals are lower than the world average, also the annual effective dose equivalent from Our Lady Health of the sick hospital, Colworth Medical Centre and Olive three medical center are lower than the world accepted value. The average absorbed dose rates are higher than the world accepted value which is 84nGy/h. the average exposure rate from the three hospitals is lower than the world accepted value which is 0.013mR/h. the absorbed dose rate exceeded the safe limit for the general public.