Considering the significant share of natural gas in the world energy sources reducing the emission in distribution chain is very important and managing the boil-off gas has a substantial role in this context. A novel process for boil-off gas re-liquefaction based on an active magnetic regenerative cryocooler integrated with a cold energy storage unit is proposed and analysed. The active magnetic regenerative refrigeration section of the system consists of nine active magnetic regenerative cryocooler units, each comprising five stages and producing a 37 K temperature span using permanent magnets with a magnetic field strength of 1.5 Tesla. Propane is selected as the heat transfer fluid due to its wide availability and cost-effectiveness. The system includes a closed-loop heat sink cooled by a nitrogen-enriched vapour-compression unit operating at a maximum pressure of 12 bar. A computational one-dimensional model is applied to simulate thermodynamic and heat transfer processes in the regenerators. Key performance parameters including specific energy consumption, exergy efficiency, coefficient of performance, and liquefaction capacity are reported, and finally a comprehensive economic analysis is conducted to evaluate the costs through the proposed process. The proposed system achieves a specific energy consumption of 0.7816 kWh/kgLNG, an exergy efficiency of 0.4192, a coefficient of performance of 0.3396. An 11.7% reduction in specific energy consumption, a 44% improvement in coefficient of performance, 29% increase in exergy efficiency in comparison with currently in use systems and a liquefaction capacity of approximately 90% demonstrate the potential of the active magnetic regenerative refrigeration-based re-liquefaction system to provide an efficient and cost-effective alternative to traditional boil-off gas re-liquefaction systems. The proposed re-liquefaction system provides advantage of eliminating the need for cold boxes and multi-stream heat exchangers, thereby reducing process complexity, lowering reliance on in-port maintenance, and significantly improving scalability. Additionally, the economic analysis shows that, compared with the most widely used commercial LNG carrier re-liquefaction system, it enables noticeable downsizing, with purchased costs of the compressors, heat exchangers, and turbo expanders reduced by approximately 12.6%, 36.6%, and 12.6%, respectively.

Flow cytometry enables rapid, quantitative analysis of individual cells and selective separation of target biological particles. Accurate single-file analysis requires the sample stream to be hydrodynamically compressed to dimensions comparable with the particle diameter so that particles traverse the detection region sequentially. Conventional microfluidic focusing strategies typically employ sequential, two-stage constriction and often position the focused stream close to channel walls, which can induce particle-wall interactions, fouling, sample loss, and degraded measurement fidelity. Here, we propose a novel microfluidic device that achieves true onestep, 3D hydrodynamic focusing by symmetrically compressing the sample stream about the channel centerline in both the horizontal and vertical directions. Coupled numerical simulations performed in COMSOL Multiphysics and an analytical solution for the core-stream dimensions show that the device produces a narrow, centrally aligned cylindrical core in which particles are subjected to minimal shear variability, a uniform optical path, and a consistent axial velocity; conditions that improve the reproducibility of scattering and fluorescence signals. The core stream height/width decreases monotonically with increasing sheath-to-sample velocity ratio and attains a stable confinement regime for velocity ratios greater than 60, beyond which additional increases in this value provide negligible refinement. Comparative analysis using Newtonian and shear-thinning rheology indicates that viscosity exerts only a secondary influence on core size. Finally, analytical predictions and numerical results exhibit excellent agreement across the full range of velocity ratio, validating the analytical assumptions of fully developed flow and negligible axial diffusion for this geometry.

Recent interest has emerged in harnessing renewable energy sources including solar, geothermal, and biogas as complementary drivers in energy conversion technologies. This study presents a thermodynamic and economic assessment of a combined cooling, heating, and power (CCHP) system employing organic Rankine cycle (ORC) with solar, geothermal, and biomass energy sources, enhanced by solar irradiance. Critical design factors turbine inlet temperature, compressor pressure ratio, methane concentration (from biomass), and number of solar reflectors were analyzed via computational simulations using Engineering Equation Solver (EES) and MATLAB software. System optimization was performed through particle swarm optimization (PSO) and genetic algorithm (GA) techniques. Results show that higher compressor pressure ratios enhance turbine output and heat transfer in the HWU unit. With 180 mirrors, the system achieves 15% exergy efficiency, 31,005 kW exergy loss, and $8,300/ hour operational costs. Increasing methane concentration by 0.1 mol reduces turbine power by 2% but lowers system cost rate by 0.5%. Among organic fluids, R123 yields the highest efficiency at 14.81%, producing 6,810 kW electricity, 3,177 kW heating, 827.4 kW cooling, 26.1 kg/s freshwater, and 0.61 kg/h hydrogen.

In this study, two common configurations based on three pressure levels have been analyzed and compared from a thermo-economic perspective with a simple absorption chiller. All examined systems have been powered using a flat-plate solar collector, in conjunction with a storage tank, as the primary energy source. Variables such as generator temperature variations, pressure ratios in the lower and upper compressors, effects on COP, exergy efficiency of the chiller, solar energy efficiency, exergy efficiency of the solar system, total cost rate, and exergy cost per unit of cooling production have been investigated. This research has been modeled using EES software. The simulation results indicate that modifications to compressor pressure levels and adjustments to generator temperature exhibit complex impacts on the thermo-economic behavior of the system, where in some cases they enhance performance, while in others they lead to efficiency decline. Furthermore, the total system irreversibility is estimated to be 328.1 kW, of which 89 percent, equivalent to 251.9 kW, is attributed to exergy destruction in the solar collector. Additionally, the total cost rate associated with the solar collector is estimated at $75.053 per hour, accounting for 88.09 percent of the overall system cost, which amounts to $85.19 per hour.

This study presents a comprehensive thermodynamic and exergoeconomic analysis of a solar power tower (SPT) system integrated with a supercritical CO2 recompression Brayton cycle (SCRBC) and an ejector-absorption refrigeration cycle (CARC). The system is evaluated using multi-objective particle swarm optimization (MOPSO) to simultaneously improve overall efficiency and reduce both investment and exergy destruction costs. The optimization process led to an increase in SCRBC net power output from 19.3 MW to 20.1 MW and an enhancement in exergy efficiency from 47.0 % to 47.1 %. The CARC subsystem effectively utilized the waste heat, boosting its net work output from 2376 kW to 2473 kW. As a result, the overall system exergy efficiency improved from 25.52 % to 26.58 %, while the exergy destruction cost rate decreased from 3238 $/h to 3147 $/h. Parametric studies revealed that increasing the maximum operating temperature of the SCRBC improves efficiency and reduces costs, whereas raising the minimum operating temperature increases exergy destruction and lowers system performance. The extraction ratio and boiler temperature were found to significantly influence both cooling capacity and power output. These findings demonstrate the potential of the hybrid SPT-SCRBC-CARC configuration for delivering sustainable, efficient, and cost-effective multi-generation energy solutions.

Creating a high heat transfer flux is not a common phenomenon and occurs only when a source of heat production (or consumption) is placed in a small volume; in precision casting systems, heat transfer should be done at a high velocity due to the presence of thin molten branches. Nanofluids present a significant opportunity to improve the thermal efficiency. In this research, a combination of different solutions to enhance heat transfer has been evaluated simultaneously. For this purpose, in the current research, aluminum oxide non-Newtonian nanofluid in volume percentages of 0, 0.5, 1.5, and 2 has been investigated in a torsional heat exchanger with a rotating triangular blade around the tube. The base fluid of this non-Newtonian nanofluid consists of water with 0.1% mass of carboxymethyl cellulose. In this study's results, the heat exchanger's performance has been predicted. Combining neural network optimization code with the numerical simulation of the double-tube spiral geometry and using non-Newtonian nanofluid to increase the heat transfer and improve the performance of the heat exchanger is the innovation of the present research.

This study presents an industrial-scale heat recovery solution for spray dryers utilizing two H-type elliptical finned tube heat exchangers to decrease energy consumption and operational costs in the tile ceramic process. A verified Computational Fluid Dynamics (CFD) model was utilized to simulate realistic operating circumstances for the proposed design at an actual manufacturing facility in Iran, focusing on thermal performance and fluid flow patterns. The initial heat exchanger recovers waste heat from the exhaust air, but the subsequent one employs a Cu-Therminol VP-1 nanofluid loop for heat transfer to the atomizing air, thereby diminishing the energy input to the burner. Simulation results demonstrate a 7.46% enhancement in energy efficiency, with Nusselt number values improving throughout the Reynolds number spectrum, and a maximum outlet atomizing air temperature of 333.2 K at the minimum inlet velocity. The utilization of elliptical fins decreased the pressure drop and significantly lowered the dew-point temperature of the exhaust gases, thus mitigating the risk of sulfuric acid condensation and related corrosion. The monthly gas consumption decreased from 981,787 Nm3 to 683,408 Nm3 during peak usage months, resulting in annual cost savings of $38,219. The total capital investment for the system, which includes the heat exchanger, oil pump, control panel, and maintenance, amounted to $55,500, with a project payback period of 1.5 years. These findings illustrate the economic viability and financial feasibility of implementing elliptical-finned heat exchangers for spray dryers, offering a replicable model for energy enhancement in energy-conscious industrial sectors.

Enhancing the thermal performance of phase change materials (PCMs) is vital for improving the efficiency of energy storage systems. While fins are widely used to expedite the melting process by boosting thermal conductivity, their effectiveness diminishes as melting progresses and natural convection becomes dominant. Meanwhile, local mechanical oscillation has emerged as a promising technique to further accelerate melting, though its isolated use has been the primary focus of prior studies. The combined effect of fins and local oscillation, particularly their interaction in influencing the heat transfer dynamics of PCM, remains unexplored. Thus, this study develops a numerical model to investigate the interaction between various fin configurations (namely, sinusoidal, and positive/negative straight fins) and local oscillation within a finned rectangular enclosure. Moreover, the local oscillator's placement on the hot wall, as well as its proximity to the fins, are among key factors analyzed. The results demonstrate that negative rectangular fins consistently deliver superior thermal performance, while the effectiveness of local oscillation diminishes when placed between fins, particularly as the melting front progresses. The optimal configuration is a vertical oscillator positioned at the base of the hot wall near a negative fin, which achieves a 64.3 % reduction in melting time. Notably, as the lower fin is installed closer the bottom wall of the enclosure, two distinct mechanisms arising from extension of the heating area and local flow stimulation by the oscillator plate, though differing fundamentally, result in similar effects during the later stages of the melting process, thereby diminishing the overall influence of localized oscillation on the melting process.

The interplay of mixed natural and forced convection in adiabatic enclosures is crucial for a range of engineering applications, including heat exchangers and magneto-convective cooling systems. While previous studies have investigated combinations of influential factors, including wall geometry, magnetic fields, moving objects, and the behavior of Newtonian and non-Newtonian fluids, none have comprehensively explored these factors altogether. Thus, the aim of this study is to investigate these parameters collectively within a unified framework. Through numerical simulations, the effects of cylinder orientation, Richardson numbers (Ri), Hartmann numbers (Ha), power-law indices (n), and nanoparticle volume fractions (φ) on heat transfer are systematically examined. The findings reveal that increasing the power-law index significantly elevates the average Nusselt number (Nu) across all fluid types. In shear-thinning nanofluids, a higher Richardson number generally lowers the average Nu, while in conditions dominated by forced convection (low Ri), a higher Ha boosts Nu. The addition of nanoparticles invariably improves the Nu, indicating improved heat transfer. When utilizing magnetic fields, an overall increase in Nu is observed, with specific optimal nanoparticle fractions identified for varying Ha conditions, 4

This study proposes an innovative fan-shaped heat sink configuration aimed at improving thermal regulation in electronic systems through enhanced latent heat utilization and convective heat dissipation. Featuring inclined fins and triangular cavity structures, the design increases effective surface area and strengthens interaction with the cooling airflow leading to improved thermal response under diverse loading conditions. The heat sink employs a hybrid cooling mechanism using a nano-enhanced hybrid composite phase change material (HcPCM) to deliver compact and efficient thermal management. A detailed three-dimensional conjugate heat transfer model is carried out via COMSOL Multiphysics to evaluate the performance of three different systems: air-only, HcPCMonly, and a hybrid air-HcPCM-cooled configuration. Numerical simulations are performed across heat fluxes of 20, 25, and 30 kW/m2, and convective heat transfer coefficients ranging from 10 to 50 W/m2 & sdot;K, capturing both natural and forced convection regimes. The HcPCM is formulated by dispersing graphene oxide and multi-walled carbon nanotubes into RT-35HC at volume fractions of up to 6 %. At higher volume fractions, the phase transition started earlier and liquid fraction growth was faster, where the duration of latent buffering reduces by up to 9 %. Findings reveal that the hybrid approach ensures stable temperature profiles and faster equilibrium, particularly at higher convective coefficients demonstrating its efficacy for high-performance by maintaining the base temperature within 315.15-343.15 K range under high thermal loads and strong convection. Additionally, reconfiguring HcPCM distribution zones yields improved melting dynamics and energy dispersion under moderate convection conditions (h = 30 W/m2 & sdot;K) achieving 40 % reduction in convective cooling demand.

This study investigated a forced convection of nanofluid in a microchannel with the presence of square obstacles using lattice Boltzmann method. The slip boundary conditions for velocity and temperature jump are considered for microchannel. The study is conducted in three volume fractions of nanoparticles, two Knudsen numbers and two Reynolds numbers. The results is shown that with enhancing the volume fraction of nanoparticles, the heat transfer coefficient increases more than two times. It is observed that by increasing the Knudsen number, the velocity slip and also temperature jump increases, but the heat transfer coefficient and the friction coefficient decreases. The first obstacle in the microchannel is more effective which is due to the creation of the vortex and the vortex characteristics in dissembling the hydraulic and thermal boundary layers. Also, increasing the nanoparticles volume fraction, the heat transfer coefficient rises noticeably.

In this study, the solidification of four types of phase change materials (PCMs)in the shell is investigated to heat up ambient air. The shell is placed in a room, and the effect of addition of aluminum oxide, titanium oxide, and copper oxide, nanoparticles is studied numerically on the thermal behavior of material. The enthalpy porosity method is used for the transient three-dimensional modeling during the solidification process. The nanoparticle volume fraction is varied from 0% to 10%. According to the results, an increase in the volume fraction of nanoparticles leads to the rising rate of heat transfer and solidification of PCMs. Furthermore, it decreases the liquid fraction maximum up to 41%, but it does not significantly affect the ambient air temperature. It was found that the type of material has a great effect on reducing the solidification time and liquid fraction. Also, RT41 without adding nanoparticles is the best material with the maximum increase in the air temperature of 8K and approximate stabilization of 3.5 hours.

We studied Rankine power and absorption cooling cycles using a dual mixture of water and ammonia as the working fluid and power and cooling cycles generated simultaneously using a single heat source. Parametric analysis was used to assess the impacts of thermodynamic parameters on the performance of the combined cycle. The results show that increasing the superheater temperature increases the output power, the exergy efficiency, and the economic cost but reduces the thermal efficiency. On the other hand, increasing the maximum cycle pressure results in a reduction of the output power and the economic cost, but increases the pressure to 30 bar. Meanwhile, increasing the absorbent temperature decreases the output power, the exergy efficiency, the economic cost, and the thermal efficiency. By using decision-making parameters such as the superheater temperature, the absorbent temperature, and the concentration of the base mixture, the cycle can be optimized by using a genetic algorithm to achieve the maximum exergy efficiency but minimum cost. The results obtained by using the genetic algorithm reveal that, when the super heater temperature is 402 K, the absorbent temperature is 260 K, and the concentration of the base mixture is 0.54, the cycle reaches an optimum exergy efficiency of 0.758 with an economic cost of 7.699 dollars per hour. These three variables were found to be appropriate for optimization. Therefore, using the input variables of the superheater temperature, the absorber temperature, and the concentration of the base solution, the cycle was optimized, reaching a maximum exergy efficiency and minimum economical cost, by using a genetic algorithm. The results of the algorithm indicate that, when the superheater temperature is 402 K, the absorber temperature is 260 K, and the concentration of the base solution is 0.54

The left ventricular assist device (LVAD) is a blood pump that boosts the pumping ability of the bottom left chamber of the heart in patients with advanced stage of heart failure. This study aims to present a detailed investigation into the hemolytic characteristics associated with an LVAD, while scrutinizing the impact of valves on blood damage in a reciprocating blood pump. To this end, a numerical approach is utilized to explore the effect of valves movement and leakage flow as the two critical causes of red blood cell damage (hemolysis) by capturing the full range of the valve motion. To predict both blood flow and the hemolysis index, corresponding time-dependent nonlinear partial differential equations are integrated into the governing formulation system. The fluid dynamic characteristics are derived from the Navier–Stokes equations, while the degree of hemolysis is determined by incorporating two additional scalar transport equations using an Eulerian transport method. To simulate valves closure, we consider different methods namely, dynamic mesh technique, viscosity valve closure model and the combination of both. The findings reveal that the hemolysis index is minimum at the inlet region and acquires its maximum value at the valves and clearance subdomains. Moreover, the results depict a favorable reduction in the hemolysis index through a simultaneous increase in frequency and decrease at a specific Reynolds number. It is observed that valves movement and valves leakage flow lead to a sensible one and two order of magnitude increase in the hemolysis index, respectively.

In the present work, the convection heat transfer and pressure drop of the turbulent flow based on a non-Newtonian fluid were numerically investigated in a double-pipe heat exchanger with various porous rings by considering the inner tube under constant heat flux. The solution of 0.1% and 2% mass carboxy methyl cellulose in deionized (DI) water water was used as the base non-Newtonian fluid. The fluid flow and heat transfer in this study were modeled by using the RNG K-epsilon turbulent viscosity with the enhanced wall treatment. The non-Newtonian power-law method was used in ANSYS Fluent software to resolve the flow within the numerical solution domain in the double pipe. Furthermore, the thermal performance of the heat exchanger, and the effects of the geometry, number, thickness, and height of the porous rings at the various Reynolds numbers were studied. According to the results, using non-Newtonian fluid had a significant effect on the average Nusselt number and pressure drop which were increased by up to 40.1% and 10 times, respectively. The annular tube possessing six porous rings at Re = 4,000 and height = 2 mm, thickness = 6 mm, applying non-Newtonian fluid can improve the efficiency of the system by up to 11.25%. It also found that by increasing the porous thickness, the Nusselt number increased by up to 56.3% at its maximum. The results have demonstrated a satisfactory level of agreement with experimental and correlation data by comparing them with existing data in similar literature.

A detailed numerical investigation was conducted to scrutinize the impact of heated wall configurations, serving as a primary heat source, on the melting process of phase change materials (PCM) within a rectangular cavity. The study explored various configurations, including square, rectangular, trapezoidal, and curvy, to understand their influence on the liquid fraction, melting time, and stored energy. Through employing the enthalpy-porosity method for the phase change, the analysis revealed that wall geometry significantly affects the melting process, where formation of local enclosed regions acting as heat sources enhance both conduction and convection heat transfer mechanisms. The investigation showed that the curvy wall configuration, by facilitating more effective free convection due to its smooth and continuous surface, markedly improves the melting process. This configuration minimizes flow separation and promotes uniform fluid motion, thereby enhancing convective heat transfer efficiency, particularly in the latter melting stages. The results underscore the superiority of the curvy configuration, with a 57.6 % decrease in melting time and a 16.3 % increase in energy storage capacity compared to the baseline case. These findings highlight the critical role of heated wall geometry in advancing the efficiency of PCM-based energy storage solutions.

In this study, we experimentally investigate the effects of metal foam porous rings on heat transfer, pressure drop, and the heat transfer performance ratio of two non-Newtonian fluids in a double-pipe heat exchanger. Enhancing the heat transfer rate is crucial for reducing the size and cost of heat exchangers. We considered various parameters in the experiment, including the power-law index (0.91 and 0.85), porous ring thickness (4, 6, and 8 mm), and the number of porous rings (2, 4, 6). The flow is a turbulent regime, with the Reynolds number ranging from 4000 to 10,000. The test setup includes a test section with a length of 1.6 m and a diameter ratio of 0.6. Open-cell copper metal foam rings with a porosity of 0.92 are placed in the annular pipe, while the internal surface of the inner pipe is subjected to constant heat flux. The results show that, for non-Newtonian Carboxy Methyl Cellulose fluids with concentrations of 0.1% and 0.2%, the average heat transfer coefficients at Reynolds number 4000 increase by 22.0% and 32.0%, respectively. With porous rings, these coefficients increase by 80.3% and 92.7%. Additionally, the average friction factor increases by 19.2% and 35.5% without porous rings and by 320% and 280% with porous rings, respectively. Furthermore, increasing the number of porous rings from 2 to 6 increases the Nusselt number by approximately 16.8% and 17.1%, respectively. The maximum friction factor is 400% higher when using a 0.2% concentration of non-Newtonian fluid. Finally, the performance of the two nonNewtonian fluids improved by approximately 28% and 36.4%, respectively, compared to the base fluid.

In this paper, the applicability of the heat exchangers for the heat recovery and energy saving purposes in spray dryers by utilizing Computational Fluid Dynamics (CFD) is investigated. For this purpose, two different tube-finned heat exchangers with the elliptical holes are added to the equipment. The first one gives the heat of the exhaust air and the second one translates the recovered heat from the exhaust air to the atomizing air. Initially, the effect of different parameters on the heat exchangers are studied. Then, numerically the effect of adding heat exchanger on the factory performance is evaluated. It is observed that by adding the mentioned heat exchangers, the energy consumption and energy price of the factory and the spray dryer decreases. Hence, the suggested equipment can be used for energy saving in the spray dryers.

In present research, an experimental and numerical study investigated for heat transfer of non-Newtonian nanofluid flows in corrugated tubes under constant heat flux which are equipped with twisted tapes. The experimental results are based on different Reynolds number from 2400 up to 6800 and with various volume concentrations of silicon dioxide (SiO_2) nanoparticles and different twisted ratios. Present numerical simulation is carried out by utilizing computation fluid dynamic (CFD) code and for validation of obtained results, they are compared to various turbulence modeling and empirical correlations presented by other researchers. Results of experiments showed that amount of power law index of non-Newtonian nanofluids increased while the consistency index generally decreased by intensifying volume concentrations of nanoparticles. Moreover, the numerical results showed standard κ–ε model of turbulence is more proper model rather than other available models.