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Solar energy is a clean, abundant renewable energy source. Solar air heaters (SAHs) are essential for space heating due to their low cost and simplicity. However, improving their thermal efficiency remains an area of significant interest. The jet impingement method effectively enhances heat transfer from the absorber plate to the working fluid. In this study, the thermal behavior of heat transfer in a SAH with an absorber plate combined with impinging jets is numerically investigated. Thermal performance was evaluated using a three-dimensional CFD simulation with the k-ϵ turbulence model in ANSYS Fluent 19.2. The arrangement of the impingement jets is W-shaped and accordingly, the study was conducted in two phases. Two aspect ratios were considered, including AR1 = p/h and AR2 = h/p, where p and h represent the pitch and vertical distance of the jet arrangement. In the first phase, three aspect ratios of AR1 = 0.75, 0.83, and 0.92 were analyzed while maintaining a constant vertical distance (h = 120 mm) between the jets. The results showed that AR1 = 0.75 (p = 90 mm) at Re = 7500 exhibited the highest thermal performance among all examined models and Reynolds numbers. With an 80 % increase in Reynolds number (from Re = 7500 to Re = 13,500), the thermal performance of AR1 = 0.75 declined by approximately 8.33 %. In the second phase, three aspect ratios of AR2 = 0.88, 1.11, and 1.33 were analyzed while keeping the horizontal jet distance constant (p = 90 mm). The findings illustrated that AR2 = 1.33 demonstrated the highest thermal performance among all tested models and Reynolds numbers. As AR2 decreased by 16.54 % and 33.83 %, the thermal performance dropped by approximately 1.67 % and 4 %, respectively, at Re = 7500. © 2025 The Authors. Published by Elsevier Ltd.

One of the most important principles in heat exchangers is to increase heat transfer and minimize pressure drop. In the present work, a two-tube spiral heat exchanger equipped with a conical turbulator is considered. In the first part of this analysis, the diameter of the inner spiral coil was investigated. In the second part of the study, the effect of the type of working fluid on heat transfer and the hydrodynamic factors of the fluid were investigated. In the first part of the study, the results showed that the highest value of thermal performance was at the lowest Reynolds number and the value of thermal performance at this Reynolds number (Reynolds = 250) was for diameters of 42 mm, 46 mm. and 50 mm was 35, 20 and 30 percent higher than the number 1. In the second part of the study, the results showed that the thermal performance values for Water/SWCNT_MWCNT, Water/Al2O3_TiO2 and pure water were 39 %, 37 % and 35 % higher than 1, respectively, which indicates the great effect of the conical turbulator and nanohybrid fluids in improving heat transfer. This study showed that the use of the innovative conical turbulator significantly improves heat transfer and increases the efficiency of the studied double-tube spiral heat exchanger. Therefore, the use of the conical turbulator has a significant effect on increasing the thermal performance of the intended heat exchanger and the use of this type of turbulator is recommended in the industry. © 2024 The Authors

The investigation of nanofluid (NF) flow under external fields and their influence on heat transfer rates has become a key focus in both engineering and medical sciences. Among these, magnetic fields have gained considerable attention in recent years owing to their unique properties and diverse applications. This study aims to examine the thermal and fluid dynamic performance of graphene oxide nanofluid flowing over different L-shaped baffles, employing a combination of analytical and statistical techniques. The surface stretches from two coordinates with a velocity of u = -2.6 m/s for x < 0 and u = +2.6 m/s for x > 0.The flow of nanofluids containing graphene oxide moves across the surface at a velocity of one unit in the y-direction, with a temperature of 25 °C. The innovation of this study lies in the first-time analysis of the fluidic and thermal parameters of graphene oxide nanofluid flowing over baffles with different shapes on a tensile surface. Additionally, by utilizing 20 numerical data points in Design Expert software, the optimal values for velocity, temperature, and magnetic parameters on a flat surface were determined. The results of this paper examine how to achieve optimal results through the use of design of experiments (DOE) and response surface methodology (RSM).It highlights that rising magnetic pressure currents and the development of magnetic vortices significantly decrease the nanofluid's temperature and flow velocity. As the temperature difference within the fluid increases, energy is transferred between the nanofluid particles in contact with the surface. The optimization process led to notable improvements in the velocity, temperature, and magnetic characteristics of the graphene oxide nanofluid. The resulting optimal values were: velocity (u) at 1.19 m/s, temperature (T) at 10.83 °C, and magnetic parameter (H) at -0.232 T Furthermore, the optimized geometric parameters included a baffle spacing of 0.026, a baffle height of 0.085, and a page length of 1.119. © 2025

In various engineering applications, particularly pumping systems, two-phase flows that involve the simultaneous flow of two different states of matter are widely employed. For instance, in industrial settings, the utilization of an airlift pump is common for transferring air or other gases to lift liquid. Conversely, in diffusion-absorption refrigeration cycles, a bubble pump is employed to create a two-phase flow through fluid boiling. To comprehend the impact of design and operational parameters on the lift water bubble pump, a comprehensive theoretical study was undertaken. The engineering equation solver (EES) was utilized in this investigation to examine the influence of lift pipe diameter, heat flux, and mass flux on the performance of the bubble pump. The study’s findings revealed that a single set of optimal conditions and values cannot be universally applicable to the bubble pump. This is because each system possesses unique characteristics and operational parameters, leading to a distinct set of optimized parameters. The theoretical study on the lift water bubble pump underscores the significance of considering design and operational parameters while developing and operating pumping systems that employ two-phase flow. Moreover, it emphasizes the necessity for extensive research to establish optimal conditions and values tailored to the specific characteristics and operating parameters of each individual system. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.

The efficiency of forensic speaker validation (FSV) depends on the system's noise level. Hence, it's inevitable that resilient feature extraction algorithms will be adopted, aiming to remove the noise effectively and, thus, improve the overall system. The voice characteristic is adopted to extract high-order spectral features (HOSF) in the current study. The identity vector, called the i-vector, is employed as a classifier in probabilistic linear discriminant analysis (PLDA). Simulation findings based on additive white Gaussian noise (AWGN) revealed that the performance of HOSFs surpassed other techniques in terms of feature extraction strategies and speaker verification over the range of -10 dB to 10 dB signal-to-noise ratio. © 2025 Author(s).

This study involves a comparison of the experimental findings obtained from testing conducted in the Mode Stirred Reverberation Chamber (MSRC) and the Anechoic Chamber (AC). Directly comparing the reactions of different items under test proved challenging due to variations in the electromagnetic surroundings for both procedures. The tests conducted in both rooms have exhibited varying responses based on the equipment's directivity. Furthermore, the outcomes derived from this examination exhibit variability contingent upon the conditions under which the test is conducted. Hence, the test results obtained from the two chambers exhibit similar error biases. The error bias refers to the proportion of a measured response obtained under specified test conditions compared to the maximum possible reaction. The paper examines the coupling uncertainty and anticipated error bias for both test procedures, analyzing how they vary with apparent directivity. The measured AC data is utilized to ascertain the magnitude and configuration of the apparent directivity of equipment responses. © 2025, Semarak Ilmu Publishing. All rights reserved.

The increasing desire for comfort and healthy indoor environment, as well as improvements in energy standards in recent years, have stressed the need to make an active use of the building mass to achieve the maximum energy saving This is why the application of ventilated hollow-core slab systems (VHCS) can be considered as one of the innovative approaches. These systems have precast concrete slabs with tubular voids directing ventilation air on its length. In the present study Solving this system numerically using the ANSYS fluent program to study the temperature distribution and air flow in the 3-D test model of the present study to determine the feasibility of applying this system in an arid climate especially in Iraq by checking the inlet velocity and temperature and to predict the impact of these operating parameters on human comfort and energy savings. The study aimed to provide a numerical analysis of a conditioned zone's temperature distribution using VHCS. The investigation was carried out on a scale model room of size (1 m × 1.2 m × 1 m) with a scale factor of ¼. Four distinct scenarios were examined: the first two cases occurred during a no-load time in the night when there were no internal or external loads and examined the effects of changes in inlet temperatures and air velocities. The remaining two scenarios were conducted during an occupied period with internal heat gain of 630 W/m2 and external heat gain of 800 W/m2 based on the SHGC for the summer season of Iraq. As previously demonstrated, setting the inlet velocity to 1 m/s resulted in an optimal temperature and velocity distribution in the main flow, irrespective of changes in the external and internal loads and temperatures of the supply core. The findings shown that input air velocity and temperature affect heat remove efficiency. In addition, numerical outcomes have also illustrated that the Thermal Active VHCS System, while used in combination with ventilation strategies, could indeed regulate the space conditions by cooling down the building's ceiling, thus eradicating stored heat. All investigations found VHCS systems suitable for air conditioning in dry and hot locations. The systems are known for their ease of use, simplicity, high performance, comfort, and energy savings. They can also reduce peak loads to boost structural energy efficiency. © 2024 The Authors

Studying cracks in aluminum (Al) nanosheets is crucial because it enhances our understanding of their mechanical properties and failure mechanisms, which are vital for applications in lightweight structures, electronics, and nanotechnology. In this study, different levels of an external electric field (EF) (1, 2, 3, and 5 V/Å) were used to see how they affected the growth of nanocracks in Al nanoplates. This investigation was carried out utilizing molecular dynamics simulation and LAMMPS software. Increasing EFA to 2 V/Å increased to maximum (Max) stress from 230.567 to 242.032 GPa. Furthermore, increasing the voltage to 5 V/Å reduced Max stress to 230.567 GPa. Max (Vel) occurred in the presence of 2 V/Å which reached 14.2192 Å/ps. The increase in atomic Vel in Al nanoplates can be attributed to enhanced atomic collisions and energy transfer among atoms as the EFA increases to 5 V/Å, the Vel declined to 11.9908 Å/ps. On the other hand, the outputs predicted the atomic evolution of designed Al nanoplates can manipulate the EF value changes. Numerically, by changing the EF parameter from 1 to 5 V/Å, the nano-crack length value varied from 27.87 to 30.16 Å. Physically, this structural evolution occurred through changes in interaction energy (mean attraction energy) within various regions of Al nanoplates. In industrial cases, this nano-crack length manipulation by EF amplitude parameter can be used to prepare atomic nanoplates with different resistances to the crack growth process. © 2024