Journal of Thermal Analysis and Calorimetry最新文献

Temperature-dependent thermal conductivity of copper oxide is of great significance for the research on the thermal hazards caused by poor electrical contact. In addition, copper oxide is also a promising material in energy storage. In the aforementioned fields, the heat transfer and temperature distribution are determined by the thermophysical properties of copper oxide. However, thermal conductivity of copper oxide is seldom mentioned in the available literature. Moreover, it is impractical to test the copper oxide’s thermal conductivity by the existing instruments directly due to the difficulty in sample preparation and the limitations of the equipment. Therefore, we investigate an approach to determine the temperature-dependent thermal conductivity of copper oxide using an inverse method. Temperature-drop experiments are conducted to record the heat transfer process over a broad temperature range. Three optimization algorithms, including SNOPT (Software for Large-Scale Nonlinear Programming), particle swarm optimization, and simulated annealing, except for the optimization methods, the effects of the baseline temperature and measurement errors are also tested. Results demonstrate that the particle swarm optimization is the most applicable method to solve the thermal conductivity problems with minimum errors. The average, lower and upper 95(%) confidence intervals of the parameter estimation results are provided, which can be used for further heat transfer modeling.

This study focuses on the application of nanofluids in the context of automobile radiators. The integration of nanofluids in automotive cooling systems, particularly radiators, presents a promising avenue for enhancing heat transfer efficiency. Because they have enhanced thermal conductivity and are engineered suspensions of nanoparticles in base fluids, nanofluids are a desirable solution for addressing heat dissipation issues in car radiators. The core idea of this study is to improve the work done on radiators by selecting an ideal nanofluid with nanoparticles that have a faster rate of heat transmission, thereby reducing the additional work required to maintain the coolant temperature while concurrently achieving higher heat transfer rates between the radiator and coolant. This study also gives a comprehensive overview of nanofluids, including the types of nanofluids (unary and hybrid), methods for their preparation, and the key characteristics required for nanoparticles to be effective and safe for use in nanofluid coolants. It further discusses the properties of specific nanoparticles such as Al₂O₃, ZnO, SiO₂, and CuO, highlighting their thermal characteristics and potential advantages when incorporated into nanofluids. The experimental setup for testing the industrial coolant and prepared nanofluids using an automobile radiator is described in detail. The setup includes a pump to circulate the coolant, a heat source that replicates the engine's heat, and thermocouples to detect temperature changes at both the inlet and outlet. The experimental results are presented in the form of graphs, demonstrating the average cooling performance of each nanofluid mixture. The study also addresses the importance of nanofluid stabilization and describes various tests conducted to check the quality and specific properties of the nanoparticles and nanofluids, including zeta potential, thermal conductivity, FTIR, and pH tests. To test the prepared nanofluids, a radiator setup with real-time temperature measurement has been fabricated and upon experimentation, the ethylene glycol- and water-based nanofluids, with 0.1 mass% nanoparticles show better stability and cooling performance than the nanofluids with 0.2, 0.3 mass% of nanoparticles and with propylene glycol and water-based nanofluids, with 0.1, and 0.2 mass% nanoparticles show better stability and cooling performance than the nanofluids with 0.3 mass% nanoparticles. The study's findings suggest that the optimum addition of nanoparticles in the radiator coolant will result in enhanced cooling performance of the radiator.

Energy demand has increased gradually. Meeting the energy demand through available sources in the country leads to self-sufficiency. Alternate fuel production and implementation-based research have been more concentrated on encountering that demand for CI engine fuels. Here, transesterification produced biodiesel from the Ziziphus mauritiana seed oil is used. While running, the 5.2 kW CI engine with this new neat Ziziphus mauritiana biodiesel (ZMBD) has 8.7% lesser brake thermal efficiency and 4% and 33% higher NOx and smoke emissions than diesel at full load. Therefore, this biodiesel is blended with 10% and 20% by volume of camphor oil biofuel (COBF) to improve the performance. Also, exhaust gas recirculation (EGR) of 10% and 20% is employed for the better result-produced blend. At full load, 80% ZMBD with 20% COBF blend produced 6.9%, 19.8%, and 15.3% increased brake thermal efficiency, maximum heat release rate, and NOx emission and also 19.05%, 23.73%, 5.78%, and 19.75% drop in CO, unburnt HC, CO₂, and smoke emission than ZMBD. With this blended fuel operation and 20% EGR employment is produced 52.99% reduction in NOx and a 13.96% reduction in smoke emission with 3.33% increased brake thermal efficiency compared to straight ZMBD. Therefore, this 80% ZMBD and 20% COBF blend with 20% EGR is recommended for the CI engine with improved performance and reduced NOx emission.

Graphical abstract

The phosphorus–nitrogen flame retardant hexaphenoxycyclotriphosphorus (HPCTP) was used as a flame retardant for rigid polyurethane foam (RPUF) to fabricate a series of RPUF/HPCTP composites by all-water foaming technology. On this basis, the fire retardancy of the composites were investigated by thermogravimetric (TG), thermogravimetric–infrared (TG-FTIR), scanning electron microscopy (SEM), microcalorimetry, and Raman Spectroscopy. The tests showed that the RPUF/HPCTP composites reached the maximum limiting oxygen index (LOI) value of 24.2 vol% and passed UL-94 V-1 rating. It was also observed that RPUF/HPCTP composites exhibited thermal conductivity of 0.035 W m^-1K^-1, suggesting excellent thermal insulation property of the composites. Thermal kinetic investigation confirmed that the activation energy of the initial RPUF is 102.26 kJ·mol^-1. RPUF/HPCTP15 possessed the highest activation energy of 105.24 kJ·mol^-1, indicating the highest thermal stability. TG-FTIR confirmed that HPCTP could decrease the release intensity of CO₂ and isocyanate, indicating enhanced fire safety of RPUF/HPCTP composites. Raman spectra and SEM investigation showed that the graphitization degree and compactness of char residue for RPUF/HPCTP composites were significantly enhanced, which were benefit to fire retarding enhancement for the composites in fire. This work provided a new way for preparation of fire retarded RPUF composites.

Subcooled flow boiling has important applications in cooling systems with high heat fluxes. Additionally, it has higher heat transfer efficiency and better performance in critical heat flux compared to saturated flow boiling. In this paper, subcooled flow boiling heat transfer of deionized (DI) water under varying heat fluxes was investigated experimentally, in a vertical tube with inner and outer diameters of 4.3 and 6.3 mm, respectively. The heat transfer coefficient (HTC) behavior was studied as the flow transitioned from forced convection in a single-phase state to subcooled flow boiling in a two-phase state, ultimately reaching the critical heat flux (CHF). The curve of subcooled flow boiling of deionized water was presented by explaining the heat transfer mechanism in various boiling regions. Investigation of the effects of various parameters, such as mass flux, pressure, subcooled temperature, the length of the heating tube, and output equilibrium vapor quality (Xe), indicated that CHF increased by 42% and 42.7% with increasing mass flux from 689 to 1148 kg m⁻² s⁻¹ and pressure from 1 to 3 bar, respectively. Meanwhile, the critical heat flux decreased by 5% and 24.2% with the increase in subcooling temperature and heating tube length, respectively. Moreover, increasing the mass flux, absolute pressure, and subcooling temperature enhanced the behavior of the heat transfer coefficient. However, as the length of the test section tube increased, the HTC decreased.

A review of the existing literature on the theoretical study of peristalsis reveals that the results of a lot of investigations on peristaltic motion in a variety of complex geometries such as symmetry/asymmetric channel, tube, annulus, non-uniform channel, and curved channel are significantly improved referring to a wide range of biological, biomedical and engineering circumstances. However, as of now, the combined impacts of curvature and asymmetric displacement of walls on wall-induced fluid motion are still kept open even though the structure of the channel may also exist in the form of a curved asymmetric channel in nature. In the current investigation, a theoretical analysis of the peristaltic motion of hybrid nanofluids within a curved asymmetric channel having systematically contracting and expanding sinusoidal heated walls is examined with reference to applications of physiological conduits. Moreover, According to theory, nanofluids are mono-phase liquids in which the base fluid and the floating nanoparticles are at local temperature equilibrium, preventing slippage. The severely nonlinear governing equations of hybrid nanofluid motion powered by peristalsis are restricted to approximations based on a long wavelength and minuscule Reynolds numbers. After that, exact analytical solutions of the hybrid nanofluid were found. Finally, diagrams for the impact of relevant parameters are efficiently used to discuss and conclude the results. The outcomes demonstrate that, in comparison to the base fluid, the hybrid nanofluid has a lower temperature. The difference in heat conductivity between copper (Cu) and silver (Ag) nanoparticles has a small influence, which may be the reason for the extremely small difference in importance between nanofluid and hybrid nanofluid. These findings have several practical implications, some of which, improved drug delivery systems where the lower temperature and efficient heat transfer properties of hybrid nanofluids can be leveraged to design more effective and reliable micro-pumps for drug delivery.

Livelihood improvement in the rural areas is the key parameters to achieve the Sustainable Development Goals. This paper attempts the livelihood improvement in rural areas through green energy technologies. The manuscript comprises a detailed review of electric vehicles with unique features of micro cold storage and vehicle-to-grid technologies. A critical analysis of the intrinsic properties of thermoelectric cooler-based micro cold storage for better material selection, performance, and optimization techniques for effective electric vehicle integration is reported. The manuscript encapsulates the thermoelectric intrinsic parameters like Seebeck coefficient (S), electrical conductivity (σ), thermal conductivity (K), and figure of merit (ZT) parameters with coefficient of performance and cooling capacity (Q_C) for different types of thermoelectric modules. The review narrows down into suitable parameters for effective combined system design, such as optimal operating voltage (V_opt) and current (I_opt). The manuscript further reviewed and presented the V2G-enabled nanogrid, control, and grid integration techniques for better-integrated operation. This paper reported an experimental investigation on the designed and developed green agro storage integrated V2G enabled nano grid for a rural village in India. The case analysis was carried out by short distance agro produce transportation, decentralized DC–DC control, and phase-locked loop grid synchronization technique. The electrical, thermal and dynamic system characteristics study was carried out and reported. Also, the manuscript highlights the potential strengths, challenges, opportunities and research gaps for the stakeholders to build a sustainable future. The proposed combined system design will pave a sustainable pathway for achieving sustainable development goals.

In this article, the modeling and optimization of a dual-fuel diesel engine with the combination of South Pars Refinery gas have been discussed at the idle load. First, using the computational fluid dynamics (CFD) method, the modeling has been validated with experimental data, and the results of the present numerical solution are in acceptable agreement with the experimental data. In order to optimization, the considered objective functions include minimum NO_x emission, maximum power generation, and minimum fuel consumption. Optimization variables include start of injection (SOI) time, the mass fraction of mean natural gas (Y_NG), and inlet air pressure (P_i). The number of tests required by the response surface method for the intervals 5 < SOI < 25 before top dead center (BTDC) crank angle (CA), mass fraction 0.02 < Y_NG < 0.04, and 0.75 < P_i < 1.75 (bar) are considered with 20 numerical solutions using the CFD method. The objective functions are set with confidence 95% that has been calculated. In the following, using the non-dominated sorting genetic algorithm method, the objective functions are optimized and the Pareto front is displayed. In addition, by using TOPSIS, the optimal point has been obtained at SOI = 10 BTDC (CA), Y_NG = 0.02, and P_i = 1.6 (bar). Also, in optimal conditions for three revolutions of 850, 1000, and 1250 rpm, the thermal, fluid, and performance parameters of the engine have been compared.

The influence of polymers on entropy generation processes is substantial, particularly in the fields of fluid dynamics and rheology. The FENE-P (Finitely Extensible Nonlinear Elastic-Peterlin) model describes the polymer’s dynamics as a result of the interaction between the stretching caused by the velocity gradient and the elastic force that restores the polymer to its equilibrium position. Models such as FENE-P aid in understanding and predicting polymer flow behaviour allowing for the reduction of entropy generation by optimizing system designs. A continuum approach is employed to express the heat flux vector and polymer confirmation tensor of the model. The study investigates the complex relationship between polymer conformation, flow dynamics, and heat transfer taking into account the thermophoresis (Soret effect) and mass diffusion-thermal diffusion coupling (Dufour effect) phenomena to optimize processes by reducing entropy. This study illuminates polymer’s significance in entropy minimization, improving engineering design methodologies and applications in materials science, chemical engineering, and fluid dynamics. As result, the presence of polymers leads to a substantial decrease in the total entropy of the system. This understanding provides opportunities for enhancing heat transfer systems, thereby facilitating the development of more efficient and sustainable technology.