Despite the solar chimney’s merits in reducing fossil fuel consumption, it often requires design enhancements to meet the ventilation demands of buildings. In this vein, varying techniques have been utilized to boost their heat transfer performance. In the present study, the thermo-hydraulic performance of double-channel solar chimneys versus different absorber-glazing distances is numerically investigated under different inclination angles, evaluating their potential for compact architectural integration. The solar radiation is modeled using the solar ray-tracing method in ANSYS Fluent, enabling the calculation of the incident solar radiation on the solar chimney. The investigated chimney geometry had a height of 150 cm, a width of 62 cm, and a channel gap of 40 cm. The chimney inclination angle was varied from 0° to 45°. For the double-channel configuration, the absorber plate was positioned at distances of 10, 15, 20, 25, and 30 cm from the glass cover to evaluate its effect on ventilation performance. Unlike prior studies that focus on single-channel systems, this work provides a comparative investigation into the geometric optimization of double-channel configurations, assessing the synergy between absorber plate positioning and inclination angles. The CFD study is performed under the ambient conditions of Tehran, Iran. The numerical results demonstrate that the double-channel configuration achieves an 18.5
It has been experimentally demonstrated that the diffusion of Ru atoms into PbO–SiO2 glass during firing directly determines the electrical conductivity σ and thermo-EMF generation (Seebeck effect) in thick-film resistors. Investigations of the distributions of the ruthenium atoms concentration (using energy-dispersive spectroscopy), spreading resistance, and the Seebeck coefficient in the diffusion layer on beveled samples have established a correlation between these parameters. The spatial distribution of of these parameters is described by the complementary error function (erfc), indicating a constant diffusion coefficient within the investigated range. Near the “diffusion layer–glass” interface, the Seebeck coefficient S reaches 5–7 mV/K, whereas at the “glass–RuO2” interface, it is on the order of a few µV/K. The diffusion length estimated from the measurements exceeds 100 μm which is significantly greater than the average distance between RuO2 particles (less than 1–2 μm); this confirms that under standard processing conditions (10 min at 850 °C), the glass matrix of thick-film resistors undergoes uniform doping and acquires high electrical conductivity.
Although there are many mathematical models proposed to represent the heat pump drying (HPD) process, there is not a fully mechanistic model that considers all the relevant phenomena. Then, in this paper a complete model that considers Fourier’s and Fick’s laws within the dried product; phase equilibria in product-air (sorption isotherms) and evaporator tubes-air; heat and mass balances of the drying gas in the drying chamber, heat pump evaporator, and heat pump condenser, and thermodynamic relations including the inverse Carnot cycle, is proposed. The HPD potential for Carica papaya leaves at low (15–30 °C) temperatures was shown. Papaya leaves water average diffusivity, sorption isotherms, and alkaloids retention during drying were experimentally evaluated. Simulation showed that a 4 m3 drying chamber HPD, charged to 30
Annular concentric pipes are widely employed in industrial applications for fluid transport, especially in thermal systems. The cooling process and heat-transfer improvement in these systems, which are among the most challenging configurations, are of interest to industry. This study investigates the influence of an externally applied, pulsating, non-uniform magnetic field on the hydrothermal performance of a non-Newtonian ferrofluid within an annular pipe. The effects of key operating parameters, including magnetic field strength, magnetic field frequency, and Reynolds number, on heat transfer and thermal management are examined experimentally, and numerical simulations are performed to provide deeper insight into the flow behavior under magnetic forcing. The working fluid consisted of a non-Newtonian solution containing 2wt.
Dissimilar welding of stainless steels is extensively used in chemical, petrochemical, food-processing, and power-generation industries, where improved weld quality and mechanical performance are essential. The present study investigates the influence of TiO₂, SiO₂, and hybrid TiO₂+SiO₂ activated fluxes on the microstructural and measured hardness response of SS304–SS316 dissimilar joints produced by Gas Tungsten Arc Welding (GTAW). weld morphology, calculated heat input, surface morphology, localized elemental composition, diffraction response, and microhardness were evaluated using optical examination, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Vickers microhardness testing. The hybrid TiO₂+SiO₂ activated flux produced the deepest weld penetration (3.0 mm), the narrowest bead width (3.8 mm), and the highest measured microhardness (95 HV) compared with conventional GTAW. SEM observations revealed differences in surface morphology among the investigated welding conditions, while EDS analysis indicated differences in elemental distribution across the analysed regions. XRD analysis revealed additional diffraction peaks associated with flux-assisted welding; however, definitive phase identification requires further quantitative analysis. Overall, the hybrid TiO₂+SiO₂ activated flux demonstrated the most balanced combination of weld penetration, bead geometry, microstructural characteristics, and hardness, indicating its potential for improving the quality of dissimilar stainless-steel welds.
