Articles
Environmental Modelling and Software (18736726)193
Accurately modeling the turbulence characteristics of wind flow entering urban areas is essential for improving the reliability of air pollution simulations, particularly when utilizing the LES approach. In this study, the Consistent Discrete Random Flow Generation method was implemented within the OpenFOAM software and evaluated for the first time in the context of solving concentration equation. A comparison of four inlet boundary conditions was conducted using wind tunnel experimental data. It was found that CDRFG presents more accurate results than the other methods, with an average error of 18 %. Then, the performance of the method in a complex geometry was evaluated by comparison with both experimental data and field measurements. The simulation demonstrated a high degree of accuracy in predicting the average dimensionless concentration, showing a close match with the experimental results, with a mean error of 16 %, and with the field measurements, exhibiting a mean error of 37 %. © 2025 Elsevier Ltd
Atmospheric Pollution Research (13091042)16(1)
Air pollution caused by traffic is a major contributor to unhealthy ambient air quality in the vicinity of urban highways and puts the health of residents and pedestrians at risk. Therefore, it is imperative to examine local pollution reduction methods. The present paper is concerned with Detached Eddy Simulation (DES) of an urban area with high concentration of air pollutants. As an example of a complex surrounding morphology, the studied domain encompasses a 2.5 km stretch of high-traffic highway, a bus terminal, and the nearby residential buildings. The numerical procedure is validated with some benchmark wind tunnel and numerical data. The locations of pollution accumulation have been identified and the effect of the ambient wind speed on the change of the maximum pollution concentration points has been investigated. Furthermore, potential pollution reduction strategies for such complex morphologies have been proposed based on the geometry change to prevent the formation of critical zones of pollution accumulation. The results show that critical zones are generally formed behind the walls of upstream buildings, adjacent to the upstream wall of the highway, and in front of the walls of downstream buildings. It was also found that changes in the ambient wind speed do not significantly alter the location of these critical zones. Furthermore, increasing the distance between adjacent buildings and the highway from 21 m to 30 m, can result in an average reduction of 76% in maximum carbon monoxide concentration values. An investigation into the impact of upstream buildings height indicates that reducing the height of certain buildings can effectively diminish pollution concentration to zero in residential areas and surrounding sidewalks. Additionally, increasing the depth of the highway and erecting 2 m solid barriers on either side of the highway are identified as two other effective techniques for reducing pollution concentration on both sides of the highway. The findings can be utilised to develop novel strategies aimed at enhancing air quality for residents and pedestrians. © 2024 Turkish National Committee for Air Pollution Research and Control
Applied Thermal Engineering (13594311)279
Thermal management has a crucial role in proton exchange membrane fuel cells (PEMFC) to prevent the reduction of electrochemical reactions and membrane breakup. This paper presents a numerical modeling of the cooling plates and their integrated cooling channels and investigates heat removal performance in parallel (laminar) and serpentine (turbulent) flow fields by four distribution of position-dependent heat fluxes generated in PEMFCs. The generating heat, a current density function, is applied to the cooling plate. The results indicated that the distribution of the current density in the PEMFC, and consequently the heat flux distribution to the cooling plate impacts the PEMFC thermal performance. The transition from parallel to serpentine flow fields affects the thermal performance differently. Among the evaluated turbulence models the k-ɛ model demonstrated good predictive accuracy. The serpentine flow plate showed a 50 % lower maximum temperature difference at the studied surface in some cases. However, the pressure drop increases up to 930 kPa in the serpentine channel at the highest simulated water mass flow rate in comparison to the parallel flow field. All the temperature variables experienced lower values by applying serpentine flow filed over the parallel. The uniformity index considered as a final key parameter defining a more homogenous temperature distribution in PEMFC improved by 68 % maximum for serpentine flow field with turbulent flow. © 2025 Elsevier Ltd
Heat Transfer Engineering (15210537)
This paper deals with the three-dimensional modeling of heat and mass transfer in a miniature loop heat pipe operating with water-graphene nanofluid. Different diameters of the liquid and vapor lines are proposed to prevent the vapor from entering the liquid line. Comparison of the numerical outputs with available empirical data shows a good agreement with a reasonable discrepancy. The effects of heat load applied in the range of 20–380 W and nanofluid concentration in the range of 1–3%vf on the thermal performance of the system are investigated and discussed. The results indicate that, by increasing the heat load to 40 W, the average temperatures of the evaporator, vapor line, and condenser increase by 7.5 K, 4.9 K and 3 K, respectively. Also, the evaporation and condensation rates increase by 72.6% and 29.3%, respectively, indicating an improvement in the thermal performance. Using 1% water-graphene nanofluid instead of pure water leads to 1K reduction in the average temperature of evaporator and 4216.4 W/(m2 (Formula presented.) K) increase in its heat transfer coefficient. Moreover, the effective thermal conductivity increased 3.2% with nanoparticles, which indicates again an improvement in the system performance. However, the use of more concentrated nanofluid does not show a significant effect on performance. © 2025 Taylor & Francis Group, LLC.
International Journal of Hydrogen Energy (03603199)48(99)pp. 39064-39083
In this study, energy, exergy and exergy-economic analyses of a novel system that simultaneously generates cooling effect, heat, electricity, hot water and desalinated water for a zero-energy building are presented. It is aimed to evaluate the feasibility of using a solar-geothermal system to meet the energy and water demands of a residential building using exergy-economic indexes. The multi-generation system operates based on solar and geothermal energies, and it consists of proton exchange membrane (PEM) electrolyser, PEM fuel cell, photovoltaic system, and a desalination system with a pressure exchanger. Results indicate that energy and exergy efficiencies in cooling mode are 13.27% and 32.44%, respectively, and in heating mode are 17.25% and 42.4%, respectively. The largest exergy destruction occurs in the photovoltaics and organic Rankine cycle. It is observed that the turbine and boiler have the highest portion in the exergy destruction of the organic Rankine cycle. The capital investment and operating and maintenance cost rate, and the cost of produced distilled water are 4.288 ($/h), 67.63 (c$/m3), respectively. Moreover, the unit exergy costs of power, heating and cooling effect are investigated. The exergy-economic factor and the cost of exergy destruction for the entire system are 57.38% and 4.288([Formula presented]), respectively. © 2023 Hydrogen Energy Publications LLC
