Najiba Hasan Hamad^1,*, Ranj Sirwan Abdullah², Ahmed Mohammed Adham²

Energy Engineering, Vol.123, No.1, 2026, DOI:10.32604/ee.2025.073377 - 27 December 2025

Abstract Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance, driven by favorable flow characteristics. This study investigates the effect of modifying coil and shell configurations on heat transfer efficiency. Two key enhancements were examined: adding fins to the outer coil surface and integrating longitudinal slots within a hollowed shell. These modifications promote turbulence and extend heat transfer duration, thereby improving performance. However, they also introduce challenges, including increased pressure loss and manufacturing complexity. Numerical simulations were conducted using ANSYS Fluent 2024R1 under identical boundary conditions. With a… More > Graphic Abstract

Dong Hu^1,2, Lingxing Hu³, Facheng Qiu^3,*

Frontiers in Heat and Mass Transfer, Vol.23, No.6, pp. 1865-1882, 2025, DOI:10.32604/fhmt.2025.073409 - 31 December 2025

Abstract With the acceleration of industrialization and urbanization, ammonia nitrogen pollution in water bodies has become increasingly severe, making the development of efficient and low-consumption wastewater treatment technologies highly significant. This study employs three-dimensional computational fluid dynamics (CFD) to investigate the cavitation mechanisms and flow field characteristics in a novel jet impingement-negative pressure ammonia removal reactor. The simulation, validated by experimental pressure data with a high degree of consistency, utilizes the Mixture model, the Realizable k-ε turbulence model, and the Schnerr-Sauer cavitation model. The results demonstrate that the flow velocity undergoes a substantial acceleration within the… More > Graphic Abstract

Shuo Wang^1,2,*, Huiming Wang^1,2, Ying Zhang^1,2, Zhiqiang Zhang^1,3, Li Jia^1,2

Frontiers in Heat and Mass Transfer, Vol.23, No.6, pp. 1721-1740, 2025, DOI:10.32604/fhmt.2025.073226 - 31 December 2025

Abstract This experimental investigation was conducted on the flow boiling performance of refrigerant R134a in two types of parallel microchannels: sintered porous microchannels (PP-MCs) and smooth parallel microchannels (SP-MCs). The tests were performed under controlled conditions including an inlet subcooling of 5 ± 0.2°C, saturation temperature of 33°C, mass fluxes of 346 and 485 kg/m²·s, and a range of heat fluxes. Key findings reveal that the sintered porous microstructure significantly enhances bubble nucleation, reducing the wall superheat required for the onset of nucleate boiling (ONB) to only 0.13°C compared to 2.2°C in smooth channels. The porous structure… More >

Weifang Yang¹, Yaping Liu^1,*, Chao Gui¹, Yangyu Shi², Mengyi Ge¹

Frontiers in Heat and Mass Transfer, Vol.23, No.6, pp. 2051-2072, 2025, DOI:10.32604/fhmt.2025.070138 - 31 December 2025

Abstract This study experimentally investigates the operational performance of a scroll compressor using R513A to expand its application range as a substitute for R134a. A vapor compression heat pump test platform was established to analyze the variation trends of heating capacity, refrigerant mass flow rate, compressor power consumption, and current by controlling the compressor inlet and outlet pressures (i.e., evaporating and condensing temperatures). The results indicate that both heating capacity and refrigerant mass flow rate decrease with increasing pressure ratio. Compressor power consumption and current initially increase and then decrease with rising evaporating temperature, whereas they… More > Graphic Abstract

Noor Moneer Basher¹, Omar Rafae Alomar^1,*, Omar Mohammed Ali², Diyar Abdullah Ahmed³

Frontiers in Heat and Mass Transfer, Vol.23, No.6, pp. 2001-2024, 2025, DOI:10.32604/fhmt.2025.066997 - 31 December 2025

Abstract The energy consumption of a Split air conditioning unit (ACU) inside a building is extremely large, and efforts to decrease this issue are ongoing. The current work aims to experimentally investigate the thermal performance of ACU using an external cooling-water loop for pre-cooling the condenser to improve the efficiency and to reduce energy consumption by reducing refrigerant temperature before entering the condenser, thereby reducing the coefficient of performance. The experiments are performed on ACU with and without using an external cooling-water loop under different climate conditions. By using the experimental data, the systems’ performances for… More >

Siwei Zhang, Xiaozhou Xia^*, Xin Gu, Meilin Zong, Qing Zhang^*

CMES-Computer Modeling in Engineering & Sciences, Vol.145, No.3, pp. 3243-3278, 2025, DOI:10.32604/cmes.2025.073841 - 23 December 2025

Abstract This study presents a coupled thermo-hydro-mechanical-fatigue (THM-F) model, developed based on variational phase-field fatigue theory, to simulate the freeze-thaw (F-T) damage process in concrete. The fracture phase-field model incorporates the F-T fatigue mechanism driven by energy dissipation during the free energy growth stage. Using microscopic inclusion theory, we derive an evolution model of pore size distribution (PSD) for concrete under F-T cycles by treating pore water as columnar inclusions. Drawing upon pore ice crystal theory, calculation models that account for concrete PSD characteristics are established to determine ice saturation, permeability coefficient, and pore pressure. To… More >

Quang-Thai Nguyen^1,2,#, Duong Ngoc Hai^3,4,#, The-Duc Nguyen^1,3,4,*, Van-Tu Nguyen^2,*, Jinyul Hwang², Warn-Gyu Park²

CMES-Computer Modeling in Engineering & Sciences, Vol.145, No.3, pp. 3433-3452, 2025, DOI:10.32604/cmes.2025.070570 - 23 December 2025

Abstract This study presents a numerical analysis of the effects of a rigid flat wall with oscillating motion on the pressure wave propagation during a single spherical cavitation bubble collapse at different initial bubble positions. Different nondimensional distances S = 0.8, 0.9, 1.0, 1.1, 1.2 and 1.3 were considered to investigate the effects of initial in-phase and out-of-phase oscillations of the flat wall. Numerical simulations of cavitation bubble collapse near an oscillating wall were conducted using a compressible two-phase flow model. This model incorporated the Volume of Fluid (VOF) interface-sharpening technique on a general curvilinear moving… More > Graphic Abstract

Yuxin Wang¹, Youjiang Wang², Jieping Wang², Chao Zhang^1,*, Fanguang Meng³, Linhua Zhang¹, Yongxing Song^1,*

FDMP-Fluid Dynamics & Materials Processing, Vol.21, No.11, pp. 2761-2777, 2025, DOI:10.32604/fdmp.2025.072236 - 01 December 2025

Abstract High-pressure water jet technology has emerged as a highly effective method for removing industrial-scale deposits from pipelines, offering a clean, efficient, and environmentally sustainable alternative to conventional mechanical or chemical cleaning techniques. Among the many parameters influencing its performance, the geometry of the nozzle plays a decisive role in governing jet coherence, impact pressure distribution, and overall cleaning efficiency. In this study, a comprehensive numerical and experimental investigation is conducted to elucidate the influence of nozzle geometry on the behavior of high-pressure water jets. Using Computational Fluid Dynamics (CFD) simulations based on the Volume of… More >

Yan Wang^1,2,*, Fuqiang Zhang¹, Long An¹, Bo Wang¹, Xueya Yang¹, Jie Jin^3,4

FDMP-Fluid Dynamics & Materials Processing, Vol.21, No.11, pp. 2651-2671, 2025, DOI:10.32604/fdmp.2025.070122 - 01 December 2025

Abstract A downburst is a strong downdraft generated by intense thunderstorm clouds, producing radially divergent and highly destructive winds near the ground. Its characteristic scales are expressed through random variations in jet height, velocity, and diameter during an event. In this study, a reduced-scale parked wind turbine is exposed to downburst wind fields to investigate the resulting extreme wind loads. The analysis emphasizes both the flow structure of downbursts and the variations of surface wind pressure on turbine blades under different jet parameters. Results show that increasing jet velocity markedly enhances the maximum horizontal wind speed,… More > Graphic Abstract

Božo Damjanović^*, Pejo Konjatić, Marko Katinić

CMES-Computer Modeling in Engineering & Sciences, Vol.145, No.2, pp. 1735-1753, 2025, DOI:10.32604/cmes.2025.072256 - 26 November 2025

Abstract Ensuring the structural integrity of piping systems is crucial in industrial operations to prevent catastrophic failures and minimize shutdown time. This study investigates a transportation-damaged pipe exposed to high-temperature conditions and cyclic loading, representing a realistic challenge in plant operation. The objective was to evaluate the service life and integrity assessment parameters of the damaged pipe, subjected to 22,000 operational cycles under two daily charge and discharge conditions. The flaw size in the damaged pipe was determined based on a failure assessment procedure, ensuring a conservative and reliable input. The damage was characterized as a… More >