Physical Science International Journal

Numerical Study of Forced Convection Film Condensation in a Channel with Porous Walls

Momath NDIAYE — 2026-02-19

This work presents a numerical study of laminar film condensation of a pure saturated vapor under forced convection inside a vertical plane channel whose walls are covered with a porous material. The mathematical model, based on the conservation equations of mass, momentum, and energy, is solved using a finite difference method. The flow in the porous layer is described by the Darcy-Brinkman-Forchheimer model. A comprehensive parametric analysis was conducted to examine the influence of nine dimensionless numbers on the liquid film thickness (δ*) and the corresponding heat transfer performance, characterized by the Nusselt number (Nu). The results indicate that the film thickness increases with increasing dimensionless thermal conductivity (λ*), Prandtl number (Pr), and dimensionless viscosity (ν*), which in turn reduces the Nusselt number. Conversely, the film thickness decreases, and the Nusselt number increases, with higher Reynolds number (Re), Froude number (Fr), Jakob number (Ja), porosity (ε), and dimensionless channel thickness (H*). The channel aspect ratio (L/A) was identified as the most dominant parameter affecting both film growth and heat transfer. While the model is validated against existing analytical work, providing a robust theoretical framework, direct experimental comparison remains a scope for future investigation. These findings offer critical insights into the coupled hydrodynamics and thermal phenomena, providing practical guidance for the design and optimization of high-performance compact heat exchangers that leverage porous media to enhance condensation.

Optimization of a Building's Indoor Temperature and Sensitive Air-Conditioning Loads Using the BLT-Parpaing Hollow Double Wall

Daouda Sawadogo — 2026-02-20

In hot, dry tropical climates (sahelian), such as Ouagadougou (Burkina Faso), high demand for air conditioning in buildings poses a major energy challenge. This study aims to optimize the indoor temperature and sensible air conditioning loads of a typical three-bedroom F3 building with cavity walls, using a double-wall system combining lightweight concrete blocks and hollow concrete blocks (LBC-hollow block), a solution rarely studied in these climatic conditions. The methodology consisted of characterizing the thermal properties of the materials and simulating the building in reference and optimized scenarios using KoZiBu software. The results show that the use of BLT-cinder block double walls reduces the average indoor temperature by 2 to 2.6°C depending on the room, with a maximum decrease of 4.1°C in February in room 2, compared to a single-wall building made of hollow cinder blocks. This improvement translates into annual energy savings of 24.06%. However, to promote the adoption of the system, it would be relevant to compare these savings with the additional cost of implementing the BLT double wall.

Enhanced Performance of Dye-Sensitized Solar Cells Using Natural Dye Mixtures and Mesoporous TiO₂ Photoelectrodes

F. Jabli — 2026-02-20

In this study, dye-sensitized solar cells (DSSCs) were fabricated using natural dyes extracted from blackberry, spinach, and red cabbage as environmentally friendly photosensitizers. The optical properties of the extracted dyes were examined using UV–visible spectroscopy. The photovoltaic performance of the DSSCs was evaluated using two two types of photoelectrodes: commercial TiO₂ and laboratory-prepared mesoporous TiO₂. The photoelectrodes were deposited onto fluorine-doped tin oxide (FTO) substrates via electrophoretic deposition, while platinum counter electrodes were prepared by spin coating.

The assembled DSSCs were characterized under simulated solar illumination using a liquid iodine-based electrolyte. Among the investigated sensitizers, the mixed natural dye composed of blackberry, spinach, and red cabbage achieved the highest power conversion efficiency of 1.4%, with an open-circuit voltage of 0.76 V, a short-circuit current density of 2.93 mA·cm⁻², and a fill factor of 62.98%. In comparison, the DSSC sensitized with blackberry dye alone reached an efficiency of 0.72%.

These results demonstrate the potential of natural dye mixtures combined with nanostructured photoelectrodes for improving the photovoltaic performance of DSSCs. The present work highlights the feasibility of using low-cost, eco-friendly materials in the development of sustainable solar energy devices. However, a slight decrease in performance was observed after two days, highlighting the need for further optimization to improve the long-term stability of the DSSCs.

Jones-Dole Coefficients of Electrolyte Solutions of Zncl\(_2\) in Mixtures of Propylene-Carbonate and 1,2-Dimethoxyethane

J. N. Obowu — 2026-03-02

The paper reports the contrasting impact of non-bonding electrostatic interactions - dipole-dipole and ion-dipole interactions in ZnCl₂ electrolytes; prepared in mixed solvents of propylene carbonate and 1,2-Dimethoxyehane. The organic electrolyte solutions were constituted by incorporating ZnCl₂ salts in the mixed solvents at concentrations of 0.01 M, 0.05 M and 0.10 M at 298.15 K. Density and viscosity measurements were determined at different solvent compositions at 298.15 K. The viscosity of pure solvents ranged from 2.080 to 1.042 cP over the composition (0-100% DME). For the solutions 0.01 M, 0.05 M and 0.10 M ZnCl₂, the viscosities ranged from 2.301 to 0.901 cP, 2.902 to 1.037 cP and 3.697 to 1.185 cP respectively for the composition range (0-100% DME). The viscosity data was fitted to the Jones-Dole equation and coefficient values for A and B extrapolated from plots of of (\(\eta\) _r − 1)/\(\sqrt{C}\) versus \(\sqrt{C}\). The values of the A coefficients were positive over the composition range, confirming the presence of ion interactions. The B coefficient values were also positive over the composition range, confirming the presence of ion-dipole interactions. The A coefficient values decreased from 0.784 to 0.079 over the composition (0-100% DME). The B coefficient values increased from 5.033 to 5.775 and from 5.436 to 5.623 over the composition (0-25% DME) and (50-75% DME) respectively. The B coefficient values decreased from 5.775 to 5.436 and from 5.623 to 3.490 over the composition (25-50% DME) and (75-100% DME) respectively.

Empirical and Measured Analysis of FM Signal Attenuation at 91.1 MHz and 101.5 MHz in Adamawa State, Nigeria

Samson Dauda Yusuf — 2026-03-17

FM signal is one of the major and fastest channels for information dissemination in Nigeria, especially in times of security treats due to the rising insecurity in the nation. However, the quality of radio broadcasting in North-Eastern Nigeria is very poor due to the nature of the terrain that causes interference with the transmitted signals. In this study, analysis of signal attenuation on FM 91.1MHz and 101.5MHz was studied in Adamawa State using propagation models. Primary and secondary data were taken from the field and the radio stations respectively. The field data were that of signal strength of both stations at a mean distance of 20km through a 250km radius of coverage along Adamawa Central and Adamawa North senatorial districts using a field strength meter (TM-195, 3-axis). Calculated attenuation using the Okumura’s model was compared to the measured attenuation. The effect of some atmospheric parameters such as temperature and pressure were also measured. The results show that signal attenuation is directly proportional to linear and vertical distance. The correlation between attenuation and distance is 0.85 for FM91.1 and 0.80 for FM101.5. Attenuation of signal strength appears to be directly proportional to temperature and inversely proportional to increased pressure. It was also discovered that the radio stations do not cover a 250km radius as calculated and documented, which means that there is a disagreement between the field and documented values of the signal strength of the radio stations owing to the high attenuation of the signals in the region. This study will have application in telecommunication, especially in the procurement and installation of transmitters both for public and private sectors within this region of the country.

Design and Implementation of an Early Smoke Detection System for Fire Safety

N. A. Akonjom — 2026-03-19

This project presents the construction of a low-cost, stand alone smoke detector circuit intended for early warning in the event of smoke emissions. The circuit utilizes smoke sensors as the primary detection unit, capable of sensing a wide range of smoke concentrations. A 9V battery supplies power to the system, regulated to 5V using an LM7805 voltage regulator to ensure stable operation of the electronic components. A 10µF capacitor provides additional filtering to smoothen voltage fluctuations. The sensor output is passed through a 10K potentiometer, allowing manual adjustment of the detection threshold and enhancing the system's sensitivity to varying environmental conditions. Once the smoke concentration exceeds the set threshold, a BC547 NPN transistor functions as a switching device, activating an light emitting diode (LED) and a buzzer to provide immediate visual and audible alerts. The TF4 - Open plastic fire (polyurethane) and TF2 - Rapid smoldering pyrolysis fire (wood) was used for the testing. The device was connected to electricity and observed in an environment without smoke for about six hours. Within this period the alarm component did not sense any smoke around, so it remained off. This indicates the circuit was stable and did not produced a false signal. It was able to overcome dust and noise parameters. The smoke detector's obscuration threshold is 16%/meter. The circuit was built and tested successfully on a prototype board, demonstrating accurate detection and reliable response to the presence of a smoke. The prototype proved energy-efficient, portable, and simple to assemble, making it suitable for use in homes, kitchens, laboratories, and small office spaces.

Thermodynamic Characterization of Wet and Dry Atmospheric States Using a Two-State Hidden Markov Model over the Middle Belt Region of Nigeria

I. O. Agada — 2026-03-20

Tropical temperature and rainfall variability in Nigeria is driven by interactions between thermal energy, latent and sensible heat fluxes, and large-scale circulation. Hidden Markov Models (HMMs) can link observed meteorological data to underlying thermodynamic regimes, providing a probabilistic framework to understand wet and dry seasonal transitions beyond traditional statistical approaches. This study investigated the temporal and seasonal evolution of rainfall and temperature variability in the core Middle Belt states (Benue, Plateau, Niger, Kogi, Nasarawa, Kwara, and FCT) of Nigeria using a two-state Hidden Markov Model (HMM). The model identified two hidden thermodynamic regimes representing dry and wet atmospheric states based on 30 years (1991-2020) daily rainfall and temperature data obtained from National Aeronautic and Space Administration (NASA) meteorological center. The results shows that dry-state persistence was strongest in Plateau (0.979), Benue (0.956), and Kogi (0.918), while wet-state persistence was particularly high in Kogi (0.961), Benue (0.911), and Plateau (0.955) as revealed by the transition probabilities, indicating stable atmospheric conditions once a regime is established. State frequency analysis revealed spatial heterogeneity across the Middle Belt, with dry-state dominance in Kwara (80%), Niger (73%), Plateau (69%), and Benue (68%), while wet-state dominance occurred in Nasarawa (77%), the Federal Capital Territory (74%), and Kogi (69%). Seasonal analysis confirmed strong dry-state dominance during the dry season in Plateau (0.996), Niger (0.994), and Kwara (0.985), whereas Nasarawa (0.993) and FCT (0.991) maintained wet-state characteristics even during nominal dry periods, indicating sustained atmospheric moisture availability. The study concludes that there is dual climatic domination in the Middle Belt, with some states (Kwara, Niger, Benue and Plateau) having a dry climate and others (Kogi, Nasarawa, FCT) a wet climate. The two-state HMM effectively captures these hidden atmospheric regimes and provides a physically meaningful framework for understanding seasonal climate variability, agricultural planning, risk flood assessment and improving climate predictability in central Nigeria.

Thermodynamic Optimization of Hybrid Nanofluid Flow in Parabolic trough Solar Collectors for Solar-Powered Agricultural Machinery

C. B. Ogunlade — 2026-04-01

The efficiency of solar-powered farm machinery is often limited by inadequate heat transfer in conventional working fluids, reducing the thermal performance of parabolic trough solar collectors (PTSCs). Enhancing the thermophysical properties of the working fluid using a binary hybrid nanofluid (Cu + Al₂O₃) presents a promising solution for sustainable agricultural systems. Thus, this study investigates the thermodynamic behaviour of hybrid nanofluid flow within PTSCs, focusing on heat transfer enhancement, temperature distribution, and entropy generation. Governing equations for momentum, energy, and entropy were solved numerically using a spectral collocation approach under steady-state conditions. The results show that adding 4% hybrid nanoparticles increased the heat transfer rate by 52% and reduced entropy generation by 12%, indicating a more thermodynamically efficient process. Higher Reynolds numbers promoted uniform temperature distribution across the collector, contributing to overall system stability.