Journal of Thermal Analysis and Calorimetry最新文献

The present study examines the thermal performance and exergy characteristics of ZnO/oil nanofluid flow through four different inner twisted tube designs, labeled RT1 to RT4, within a dual-tube heat exchanger (DTHE). Numerical simulations are performed over a Reynolds number (Re) range of 400 to 2000 for the hot-side oil-based nanofluid and at Re = 1800 for the cold-side water flow. The results reveal that increasing both the inlet flow rate and the twist angle of the inner tube enhances the convective heat transfer coefficient (HTC) and pressure drop (Δp). Among the studied configurations, the RT4 design, with a 90-degree twist, yields the highest HTC and Δp at Re = 2000. The application of oil-based nanofluid further enhances thermal performance, with improvements observed in both HTC and Δp values across all designs. However, the performance evaluation criterion (PEC) shows that the benefits of using nanofluids in twisted tubes only surpass the associated drawbacks under certain conditions. For instance, a 2% nanofluid concentration in RT1 and RT2 is the only case where PEC exceeds 1. Exergy analysis reveals that exergy destruction increases with higher values of Re, larger twist angles, and greater nanofluid volume fractions, primarily due to enhanced irreversibilities within the system.

Arterial stenosis in bifurcated arteries is a major contributor to cardiovascular complications due to its effect on blood flow resistance and wall stress. In this study, the hemodynamic response of blood flow through a stenotic bifurcated artery with compliant walls is analyzed using a fractional second-grade fluid model enriched with ternary nanoparticles (Ag(Silver), Cu(copper), and CuO(copper oxide)). Unlike conventional single or hybrid nanofluid approaches, the ternary formulation offers enhanced thermal and rheological properties that improve drug delivery performance. Closed-form analytical solutions were derived under mild stenosis assumptions using Mathematica to evaluate axial velocity distributions and wall shear stress in both parent and daughter arteries. The findings show that ternary nanoparticles produce significantly higher velocity profiles and reduced shear stress compared to nano and hybrid nanofluids. The bifurcation angle exhibited minimal influence on the parent artery but demonstrated an inverse relationship with velocity in the daughter artery. Additionally, compliant wall parameters were observed to increase velocity, while the fractional derivative parameter and relaxation time showed opposite effects on wall shear stress. Beyond hemodynamic improvements, ternary nanoparticles provided a larger surface area and enhanced stability, enabling controlled and prolonged drug release. These properties suggest that ternary nanofluids extend therapeutic circulation times and may enhance treatment efficacy for cardiovascular diseases.

In summary, the integration of ternary nanofluids within a fractional fluid framework presents a promising direction for targeted drug delivery and for the development of improved biomedical strategies to manage atherosclerosis and related vascular disorders.

The impact of heat generation and Soret–Dufour effects on bioconvection stagnation point flow of MHD Boger nanofluid around a spinning sphere in the occurrence of gyrotactic microbes is examined. This paper presents a numerical solution of this impact using back-propagation intelligent Bayesian regularization with the neural network domain (BPIBR-NNs), which is novel with convergent stability. Using a dataset for the proposed (BPIBR-NNs) for many MHD-BNF-TRDS scenarios, the Bvp4c numerical technique. This model may be useful for a variety of systems, including bacterial-powered micromixers, chip-scale micro-devices like bio-microsystems, microbial fuel cells, enzyme-based biosensors, and micro-scale environments like microfluidic devices. Gyrotactic microbes added to nanoparticles increase their thermal efficiency. Reactors and spinning machines need to be built and adjusted for industrial processes to work because reliable mixing and effective heat transmission are essential. This model may be used by environmental engineers to forecast the distribution of nutrients and contaminants in water bodies. To assess the accuracy of the proposed model, the data are processed, correctly tabulated, and its validity is examined. The BPIBR-NNs training, testing, and validation methods were used to evaluate the estimate solutions for specific occurrences and compare the suggested model for verification.

This study explores the role of blood-based pentameric hybrid nanofluids composed of iron oxide, aluminum oxide, silver, gold, and copper, when circulated between two disks, in drug delivery applications. These hybrid nanofluids hold tremendous potential due to their unique properties, particularly in the presence of an external magnetic field and thermal radiation, for controlled drug release, targeted delivery capabilities, and synergistic chemical interactions. The development of drug delivery systems can be supported by mathematical modeling. This approach reduces the need for expensive laboratory experiments by deepening the understanding of the physicochemical mechanisms of drug transport. The Oldroyd-B fluid model is used to understand the mathematical behavior of blood flow under thermal conductivity and heat generation variables. The Darcy–Forchheimer model is applied to represent porous media, taking into account porosity and permeability variables. Graphical analysis reveals that relaxation time, nanoparticle concentration, and magnetic field parameters enhance the velocity pattern near the lower disk but reduce the temperature distribution. Furthermore, higher heat generation coefficient values were found to result in higher temperatures. Improvements in the surface friction coefficient and Nusselt number were observed with increasing magnetic field strength, allowing for precise drug release at the desired location and time in response to magnetic stimulation. The pentagonal nanofluids also demonstrated their ability to maintain near-surface temperatures, which in turn regulates blood flow. The accuracy of the numerical results demonstrates the effective contribution of pentagonal nanofluids to drug delivery systems, enhancing performance by improving thermal and chemical properties.

Humidification-dehumidification (HDH) is considered a promising method for treating high-salinity water. This study investigates a solar-driven HDH system that integrates a novel solar water heater, a humidifier, and a dehumidifier. The solar collector utilised is two-end open evacuated tube collector, whereas coconut fibre is employed as the packing material in the humidifier. The system’s performance is evaluated in terms of thermal efficiency, sustainability, and economic viability. The solar water heater typically achieves an average temperature increase of approximately 11–14 °C at a seawater flow rate of 100 kg h⁻¹. The results revealed that augmenting the flow rates of seawater and air enhances the system’s efficiency and productivity. The highest energy efficiency of 39.6% and the daily productivity of 4.51 L m⁻² day⁻¹ are achieved at seawater flow rate of 200 kg h⁻¹ and air flow rate of 175 kg h⁻¹. The price of water per litre varied from 0.019–0.031 $, with an energy payback period ranging from 1.6–2.6 years. The SD-HDH desalination system has been successfully designed to remove 99.7% of the salt content in seawater, demonstrating its potential to meet freshwater demands at a low cost.

This study experimentally investigates the synergistic effect of rifled riser tubes and MgO nanoparticle-enhanced deionized water (DIW) nanofluids on the performance of a flat-plate solar collector (FPSC) operating in natural circulation mode. The experiments were conducted using a 1-m² collector area coupled with a 50-L hot water storage tank. The rifled tube was tested with pure DI water and MgO nanofluids at varying mass concentrations of 0.25%, 0.5%, and 0.75%, and results were benchmarked against a plain tube collector using DI water. The performance was evaluated based on the collector outlet temperature, thermal efficiency, and the reduced temperature-efficiency characteristics. The rifled-tube design significantly enhanced heat transfer due to increased surface area and induced turbulence, which also minimized nanoparticle agglomeration. Notably, the rifled-tube collector with 0.75% MgO/DIW nanofluid achieved the highest improvements in thermal and exergy efficiencies up to 70% and 21%, respectively—compared to the plain tube collector with DI water. The collector efficiency improved progressively with increasing MgO concentration: 49%, 58%, 65%, and 70% for DI water, and 0.25%, 0.5%, and 0.75% MgO nanofluids, respectively. Additionally, the heat removal factor, F_R(τα), increased by 27%, while the heat loss coefficient, F_RU_L, decreased by 12% with the 0.75% MgO nanofluid. This configuration also enabled a potential 18% reduction in collector area, underscoring its applicability for compact, high-efficiency solar thermal systems.

This study presents an innovative approach to enhancing solar chimney power plants by integrating geothermal heating to simulate geothermal well conditions. The experimental setup included a solar collector with a 12 m diameter and an 8 m tall chimney, along with multi-layered and copper pipes totalling 1000 m to optimise heat transfer. Results showed that integrating geothermal heating significantly enhanced the system’s thermal performance, increasing air velocity to 5.8 m s⁻¹ during peak operation compared to 3.3 m s⁻¹ under standard nighttime conditions. Additionally, the central temperature within the collector (T5) rose to 68.3 °C during the day, compared to 9.2 °C in the early morning. Under traditional operation (without geothermal heating), power generation ceases entirely at night or during cloudy conditions. However, with the geothermal integration, the system demonstrated stable thermal performance and continuous energy production over 24 h. On cloudy days, the inlet temperature (T0) reached 33.7 °C at peak, while the outlet temperature (T6) climbed to 45.3 °C, highlighting the system’s ability to sustain efficient heat transfer despite reduced solar radiation. These results underscore the importance of integrating solar and geothermal energy to ensure continuous power generation. The hybrid system proved to be a sustainable and efficient energy solution, offering consistent performance even under variable weather conditions.

A severe tunnel fire frequently involves multiple fire sources and an obstacle blockage. This study uses FDS software and a full-size tunnel model (360 m × 10 m × 5 m) to investigate the behavior of dual-source fires in naturally ventilated tunnels with obstacle blockage, focusing on the effects of the obstacle blockage rate (α) and dual-source fire spacing (φ). The results show that as α increases, the hot smoke distribution on both sides of the burners changes from symmetric to asymmetric under constant φ; the two fire sources change from completely fused to completely separated as φ increases under constant α, and the maximum temperature beneath the ceiling between the fire sources gradually decreases. Based on α and φ, a formula for the maximum temperature under the ceiling and a segmented prediction formula for the longitudinal distribution of downstream temperature were developed. Error analysis further proved the reliability of the models.

This paper evaluated the thermal hazards in the synthesis process of FOX-7 (1,1-diamino-2,2-dinitroethylene) using 2-methyl-4,6-dihydroxypyrimidine (DHMP) as the raw material. Thermogravimetry–differential scanning calorimetry (TG-DSC) was employed to analyze the thermal stability of DHMP and FOX-7. The results show that: DHMP undergoes significant endothermic decomposition within the temperature range of 317.29–340.75 °C, and its decomposition activation energy was calculated; FOX-7 exhibits an endothermic crystal transformation and a two-stage decomposition process, with the average activation energy of the first stage decomposition being 248.36 kJ mol⁻¹. Accelerating rate calorimetry (ARC) was used to test the adiabatic stability of the nitrification liquid, hydrolysis liquid, and FOX-7, while the exothermic behavior during the reaction process was monitored via reaction calorimetry (Easymax). Under the scenario of cooling failure, the maximum temperature of synthesis reaction (MTSR) of the nitrification reaction and hydrolysis reaction reached 59.01 °C and 28.76 °C, respectively. According to the Stossel reaction classification method, both the nitrification reaction and hydrolysis reaction are classified as “Class 2”, indicating that these two reactions have potential decomposition hazards during industrial operation. The results provide key thermal safety parameters and risk assessment basis for the safe scale-up and industrial production of FOX-7.