Journal of Thermal Analysis and Calorimetry最新文献

This study presents an Eulerian-Lagrangian framework for the numerical analysis of spray dynamics, with a focus on droplet movement, spray-wall interactions, and the effects of varying injection parameters associated with port fuel injection (PFI) system. A grid-independent criterion is introduced to optimize mesh analysis for accurate predictions of fuel penetration length. The size distribution of secondary droplets is described using a probability density function, and statistical optimization is subsequently implemented to estimate their mean size. This probabilistic approach enhances the Lagrangian wall film (LWF) model, leading to accurate predictions of the Sauter mean diameter (SMD) at a given radial width ((R_text{{w}})), with results closely matching experimental data. For (8.0 ~text {mm} le R_text{{w}} le 24.0 ~text {mm}), the maximum SMD of 21.67 (mu)m corresponds to (R_text{{w}} = 14.0, text {mm}), while the smallest SMD of 12.68 (mu)m is computed for a radial position of (R_text{{w}} = 24.0 ~text {mm}). The numerical investigation quantifies the role of spray-wall interactions in determining the trajectory of fuel distribution, particularly in the formation of wall films and the relative spatio-temporal diesel concentration (F/A) %. The study explores aspects such as droplet size variations, heat transfer during evaporation, and film behavior under different injection pressures, providing insights into the multiphysical characteristics of spray-wall systems. Near the impingement site ((2.0 ~text {mm} le R_text{{w}} le 4.0 ~text {mm})), the plume height ((H_text{{w}})) slightly decreases with an increase in injection pressure. While the CFD methodology in this current work has been primarily developed for automotive engineering sector (PFI engines), it also has potential applications in areas such as additive manufacturing, hydropower engineering, climate science, and environmental engineering.

This research aims to assess the significance of nanoparticle size on the natural convection magnetohydrodynamic (MHD) boundary layer flow of a dusty nanofluid across a stretching sheet. Dusty fluids are widely used in industries such as manufacturing and construction, particularly in areas like infrastructure development and material processing. They are used in petroleum transportation, gas purification, power plant piping, automotive exhaust systems, and sedimentation operations. In this study, dusty nanofluid is composed of copper nanoparticles suspended in a mixture of C(_2)H(_6)O(_2)-H(_2)O (50–50%) with a Prandtl number (hbox {Pr}=3.97). The similarity transformations convert the governing partial differential equations (PDEs) into ordinary differential equations (ODEs). These ODEs are then solved numerically using MATLAB’s built-in "bvp4c" method. The effects of various involved parameters on velocity, temperature, skin friction, and Nusselt number are exemplified graphically. The findings indicate that increasing the nanoparticle radius causes temperatures to decrease for both phases, while increasing velocities for both phases. A rise in the suction parameter results in lower temperature and velocity for both phases. A surge in the Biot number significantly raises the temperatures of both phases. Increasing the suction parameter, nanoparticle radius, and Biot number increases the Nusselt number, which optimizes effective heat transfer efficiency by improving thermal conductivity and nanofluid mobility. Skin friction increases for smaller nanoparticles and enhanced suction.

An advanced numerical investigation was conducted on a tubular heat exchanger utilizing CuO-water nanofluid between 0.01% and 0.04% volume fraction to elucidate enhancements in heat transfer rate and effectiveness. The study incorporated twisted tape inserts with three distinct sweeps (5, 10, and 15) for fully developed turbulent flow conditions. The analysis explored varying mass flow rates of the hot nanofluid (0.2–0.5 kg s^-1), while maintaining a constant cold fluid mass flow rate of 0.2 kg s^-1. The k-ε turbulence model was employed to accurately predict heat transfer characteristics in the turbulent regime. Swirl flow analysis revealed a bifurcation of flow patterns: one proximal to the wall and another distal. Results demonstrated a linear correlation between mass flow rate and both heat transfer rate and effectiveness. Peak performance was observed at the highest flow rate, with the maximum effectiveness reaching 0.37 and the heat transfer coefficient attaining 2511 W m^-2 K^-1. This study provides valuable insights into the thermal performance optimization of tubular heat exchangers using nanofluid and twisted tape inserts, offering potential for significant efficiency improvements in heat transfer applications.

In the current research, a quasi-two-dimensional numerical model is used for energetic and exergetic performance predictions taking into account eight inline PTC modules with variable geometries along with the main flow direction, for Therminol VP-1 and Syltherm 800 heat transfer fluids. There are a total of thirty-seven input variables, being thirty-two regarding the geometrical parameters and five environmental/operating parameters. Surrogate-based optimization procedures (Kriging metamodel combined with Non-Dominated Sorting Genetic Algorithm, NSGA-II) are used to build the Pareto frontier for two objective functions: (i) maximization of both useful gain and thermal efficiency and (ii) maximization of useful gain and minimization of exergy destruction. The optimization results indicated that the useful gain of 8 inline PTC array can reach up to 1.0 MW for both thermal oils. By variation in the input parameters along with the PTC array, a broad range useful gain can be achieved, with negligible thermal efficiency degradation. With regard to the Pareto frontier of useful gain and exergy destruction, there is an important asymptotic point for useful gain, in which its augmentation just promotes the increase in exergy destruction. In terms of concentration ratio, the Pareto fronts showed that about 95% and 90% of PTC modules can be assumed at “heterogeneous” along with the array for the first and second objective functions, respectively. At last, convective heat transfer coefficient and outer receiver and outer glass cover temperatures along with the PTC array for different individuals of the Pareto fronts are discussed in detail.

Graphical abstract

The vaporization enthalpies at T = 298.15 K and vapor pressures from T = (298.15 − 450) K of the major hydrocarbon components in chamomile and cypriol are evaluated by correlation gas chromatography. The components in chamomile include the following four substances: (E, E) α-farnesene, E β-farnesene, bicyclogermacrene and germacrene-D. In cypriol, similar properties have been evaluated for cyperene, α-copaene, and rotundene. Both chamomile and cypriol have been used in the practice of traditional medicine.

This work aims to study the use of polyamide 12 in oil pipelines to replace steel, which is more susceptible to corrosion. Pipes of polyamide were installed in oil fields and, after 1 year of operation, were removed and analyzes. The outer layers of all field samples and the unaged sample did not show, in the DSC, any primary peak close to the melting peak. This is due to the extrusion and the formation of different crystalline structures on the inner surface, giving rise to two melting peaks. All layers of the field samples showed endothermic peaks, but the unaged sample did not. This can be attributed to the annealing process, but this phenomenon does not affect the properties PA12. The results showed no degradation and PA12 can be a viable alternative for oil pipelines, providing savings of more than 50% compared to steel, in addition to operational, human and environmental safety.

Development with the expansion of electronic devices, increased electricity consumption, and supplying the required power are some challenges involving different countries. Iran is also currently consuming in its industries that to supply electricity, it is necessary to adjust the program of various blackouts, hence the stoppage of the production of industries and mines has caused significant damage. This paper presents a comprehensive feasibility study for the construction of a 10-MW grid-connected photovoltaic (PV) power plant aimed at mitigating energy deficits in Iran's iron ore mining sector, particularly during blackout periods. Utilizing HOMER software for technical simulation, the proposed solar plant is projected to generate approximately 16 million kWh annually, with 2 million kWh available during shutdowns. Financial analysis conducted through CAMFAR software indicates a payback period of 8.6 years, an internal rate of return (IRR) of 12.67%, and a net present value of $3.45 million, underscoring the project's economic viability. The plant’s capacity to compensate for the production of 66,750 tons of iron concentrate during outages underscores its potential for significant financial benefits.

In this study, banana slices were dried in convective (CD) and modified temperature-controlled microwave drying (MTCM) methods and at 40, 50, 60, and 70 ºC to produce banana chips. The kinetics, energy analysis, and physicochemical properties of the drying processes were investigated. Drying rates varied between 0.0039 and 0.10 g moisture g dry matter minute⁻¹ for drying processes. Effective diffusion values were determined between 8.22 × 10^–8–1.13 × 10^–5 m²s⁻¹ for drying processes. Rehydration capacities were determined between 49.10 and 65.88% for dry methods. Hardness values were determined between 38.00 and 66.30 N for drying processes. Specific moisture absorption rate values were determined to vary between 0.0015 and 0.0099 kgkWh⁻¹. The energy efficiency values were determined to vary between 0.96 and 6.48% for processes, and the latent heat evaporating values ranged between 0.64 and 2.05 kWh. The most suitable (p < 0.05) color values for CD and MTCM were determined at 70 ºC. In this study, the MTCM 70 ºC method is recommended for drying kinetics and physical quality properties. In future studies, a more comprehensive analysis can be conducted by taking into account its bioactive properties.

In practical fluid mechanics, in terms of tube flow description, there is a lack of analytical descriptions and solutions of frictional adiabatic and isentropic flow. This paper explores the connections between the modeling these two flow types and reveals that frictional isentropic flow can be achieved if the heat generated by friction is removed from the flow. This is, in fact, a polytropic flow, which is made isentropic by heat extraction. The study also presents a new description and solution of adiabatic flow, which is not isentropic due to friction, but no heat loss is considered in this work. Adiabatic frictional flow is implemented by extending the application of the adiabatic exponent (k). The adiabatic exponent (k) is naturally used to describe the isentropic or adiabatic state changes of ideal gases. During adiabatic state changes, the entropy of the ideal gas remains unchanged if the state change occurs without internal friction, without internal thermal expansion and without external energy absorption or loss. This means it is no longer an isentropic change of state if there is internal friction in the fluid. The adiabatic change of state without external heat input is therefore not necessarily isentropic. In common terms, a distinction is not always made between adiabatic and isentropic state changes. This paper expands on the use of the adiabatic exponent to describe frictional flows. Further, the paper outlines the possibility of using the exponent k to describe polytropic flows, which, of course, are by no means isentropic, but can be made mathematically so if one can compensate for internal heat generation by external heat extraction.