Journal of Thermal Analysis and Calorimetry最新文献

This study employs a machine learning methodology, specifically the Random Forest (RF) model, to evaluate and optimize the productivity of a photovoltaic (PV) unit integrated with a cooling duct equipped with helical fins. A thermoelectric generator (TEG) is strategically positioned above the cooling duct to enhance electricity production. The cooling mechanism utilizes confined jets involving of ND-Co₃O₄- water nanomaterial to improve thermal regulation. The key variables considered include the number of fins (N_f), their revolution number (N_r), inlet velocity (V_i), and heat flux intensity (I). The optimization focuses on three primary objectives: maximizing profit, enhancing CO₂ mitigation (CM), and minimizing pumping power (W_p). The RF model showed strong predictive capability, achieving a test RMSE of 0.4590 and an R² of 0.9474 for W_p, an RMSE of 71.8501 and an R² of 0.8421 for Profit, and an RMSE of 2.9472 with an R² of 0.8143 for CM. A multi-objective optimization technique was used to derive Pareto front solutions, balancing trade-offs among these objectives. The results demonstrate that integrating helical fins and nanoparticle-infused cooling jets significantly improves system performance, with optimized solutions reducing pumping power, while enhancing both profit and CO₂ mitigation.

To reduce energy consumption, a model was developed to optimize a multi-generation system. The system integrates multi-effect distillation through thermal vapor compression (MED-TVC), solar flat plate collectors (FPCs), and photovoltaic panels (PVs). The objective function was to minimize the annual cost of the system. To achieve this, an evolutionary algorithm was employed to determine the optimal values of 34 design parameters. The design parameters considered for optimization included the capacity of the gas turbine as the prime mover, electrical chiller capacity, absorption chiller capacity, size of the boiler, partial loads of the gas turbine for each month of the year (12 values in total), number of FPCs and PVs, number of effects in the desalination unit, driving steam pressure, feed water flow rate, driving steam flow rate, and electric cooling ratio. A novel approach was introduced by incorporating a variable electrical cooling ratio, which represents the proportion of electrical and absorption chiller usage, for each month of the year. The optimization aimed to fulfill the heating, cooling, electricity, and freshwater requirements of a residential complex situated in Bandar Abbas, Hormozgan Province, Iran. The optimization results were compared with a constant electrical cooling ratio system where the electrical cooling ratio was assumed to be fixed throughout the year. The optimal scenario, considering the variable electrical cooling ratio strategy, yielded an annual cost of $0.9780 × 10⁶ $/year, indicating a significant 10.11% improvement compared to the conventional case ($1.0882 × 10⁶ $/year). These findings underscore the potential advantages of the proposed strategy in terms of cost savings and system performance optimization.

The improve design and enhanced thermal management systems nowadays depends upon the enhanced heat transfer capabilities of hybrid nanofluids and their wide range of applications. These lead to efficient cooling in electronic devices, thermal control in chemical processing, and several many industrial as well as biomedical applications. The proposed study aims to enrich the heat transfer characteristic of methanol-based hybrid nanofluid comprising CuO and MgO nanoparticles in convergent and divergent channels. The study focuses on the Jeffery–Hamel flow via porous medium where the impact of heat source is analyzed. The flow behavior is characterized by the role of several pertinent factors those are derived by the implementation of similarity variables in the governing equations. These rules help in transforming the dimensional form of set of equations into non-dimensional form. Numerical solution is presented for the set of equations by using bvp4c routine function in MATLAB particularly utilizing Runge–Kutta fourth-order. However, the investigation explores the key factors such as particle concentration, Reynolds number, Darcy parameter and heat source affecting various flow characteristic. The important results indicate that the existence of CuO and MgO nanoparticles significantly overshoots the conductivity and heat transfer rate in comparison with the base fluid. Further, the fluid velocity is significantly controlled by the increasing Reynolds number.

Metallic foams have become a cutting-edge solution for many thermal management problems. These are of interest by thermal research community because of the cellular structure and have gas-filled pores inside a metal matrix. Due to the uniqueness in their structure, they exhibit good performance in boiling heat transfer because of the properties such as higher specific surface area, large number of nucleation sites, wettability characteristics, and capillary action. The boiling heat transfer over metal foam is a complex phenomenon, greatly affected by the thickness, porosity, and pores per inch (PPI) of metal foam along with the thermo-physical properties of the foam and boiling liquid. By thoroughly examining recent research investigations, the paper explains the impact of open-cell metal foams on pool boiling of different liquids such as water, refrigerants, organic liquids, and dielectric liquids. This paper reviews the complexity and various influencing factors involved in flow boiling through metal foam in tubes. It also highlights findings that show metal foam significantly enhances jet impingement boiling heat transfer. Moreover, the discussion on gradient metal foams, offering insights into their potential to enhance boiling heat transfer. The comprehensive review also encompasses numerical modeling studies, such as the lattice Boltzmann method, contributing to a deeper understanding of the intricate flow and heat transfer characteristics within channels filled with metal foam.

In this paper, a continuous microchannel with nonlinear cross section (M-NCS) applied to parallel plate heat exchangers is designed, and the M-NCS is quantitatively analyzed using an analytical calculation method. By comparing the M-NCS with the microchannel with a fixed cross section (M-FCS), it is deduced that under the same internal volume of the pipe and the same average flow velocity at the inlet, the internal flow rate of M-NCS is greater than that of M-FCS, with a local maximum increase of 43%, which can improve heat exchange efficiency. The Darcy friction factor of the internal fluid of M-NCS is smaller than that of M-FCS. The internal fluid pressure drop of the M-NCS is more significant, which requires a higher external pump energy required. It is also deduced that the average temperature change of the fluid inside M-NCS is larger than that inside M-FCS. In addition, the Nusselt number and convective heat transfer coefficient of the fluid inside M-NCS are larger than those of inside M-FCS. Moreover, the local maximum value of M-NCS is 18.5% higher than that of M-FCS. In summary, the obtained results show that, compared with M-FCS, M-NCS can improve the heat exchange degree and heat diffusion capacity of the fluid inside the microchannel pipe under the same inlet mass flow rate, allowing to enhance the heat transfer. This paper also studies the impact of the microchannel local structural changes on the heat transfer and fluid performance, which provides a theoretical support for the optimization of the microchannel design of heat exchangers.

Information about the structure-property relationship can be useful for the synthesis of compounds with desired properties, analysis of the role of intermolecular interactions in various physicochemical processes and separation of the synthesis product from impurities. In the present work, the influence of the position of the carbonyl group on the saturated vapour pressure and enthalpy of vaporization of ketones was studied. The saturated vapour pressures of isomeric decanones, undecanones and isophorone were measured by the transpiration method. The enthalpies of vaporization of isomeric ketones were determined using various methods: solution calorimetry, transpiration and correlation gas chromatography. The obtained values agree with each other within 1 kJ mol⁻¹. It was shown that 2-alkanones have higher enthalpies of vaporization and lower vapour pressures than 3-, 4-, 5-, 6-alkanones, which can be explained by the stronger intermolecular interactions existing between the molecules of 2-alkanones compared to others isomers.

In this study, an attempt has been made to develop a different design for a gray cast iron rear brake disk used in the automotive industry, which can serve as an alternative to traditional designs. The designs were created to enable the production of this brake disk on the Disamatic vertical molding machine. The purpose of this study is to prevent casting defects that may occur in traditional designs. The simulation parameters were clearly explained and the correctness of the mesh structure was stated. These are the necessary parameters to show how reliable our study is. In order to minimize air bubble and sand inclusion defects encountered in the casting of a 4.5-kg automobile brake disk, different runner system simulations were performed and optimized instead of traditional runner system designs. Three different models were evaluated. The result of this study showed that the newly developed designs might be more useful than the traditional design. The resulting different filling profiles were directly associated with the gating system. The Reynolds number was used to indicate whether the liquid metal flow was turbulent or not, making it easier to make a sensible choice between designs. The designs were compared in terms of possible casting defects. The results revealed that the new designs had a more homogeneous filling profile and a lower risk of casting defects. It was found that design 2 was the most suitable option among the proposed models.

Bioheat transfer is pivotal in a range of medical and daily applications, contributing to health and well-being. In hyperthermia treatment, it facilitates the elevation of temperatures in malignant tissues, thereby increasing their sensitivity to interventions such as radiation and chemotherapy, as well as in wearable monitoring devices, rehabilitation methods like heating pads and wraps, and electric blankets. This paper investigates the effects of thermal memory and dynamic linear thermal shocks on heat transfer within biological tissues. The research utilizes an advanced form of the Pennes equation for this analysis. The mathematical framework is based on an innovative time fractional generalized Fourier’s law, which can clarify particular aspects of atypical thermal diffusion phenomena. In the model being analyzed, the temperature gradient and its historical context influence the thermal flux. Additionally, at a specific location within the tissue, the thermal source induces a linear thermal shock at every instant. For both graphical and numerical simulations, Mathcad is employed to assess how the thermal memory parameter influences heat transfer.

High flame retardancy and thermal conductivity are key performances for advanced electronic packaging materials. Herein, boron nitride (BN) and epoxy curing agent were chemically bonded with highly flame retardant DOPO moieties to obtain BN-DOPO thermal conductive filler and DOPO-PA curing agent with flame retardancy. The effect of BN-DOPO and DOPO-PA on the thermal stability, flame retardancy, combustion behavior and thermal conductive performance of EP composites were analyzed in detail. Compared with EP/Al(OH)₃, up to 32.5% in LOI, V0 rating in UL-94, prolonged 125 s of TTI, 22% reduction of PHRR and 29% reduction of THR in cone test were observed when both BN-DOPO and DOPO-PA were incorporated into EP cross-linking network. According to the residual char morphology, the excellent flame retardancy of EP/Al(OH)₃ composite containing BN-DOPO and DOPO-PA was attributed to the formation of compact front char covered by fluffy porous carbon and thick continuous back char with tiny aluminum oxide particles. Moreover, the introduction of a small amount of BN-DOPO and DOPO-PA could also greatly improve the thermal conductivity of EP/Al(OH)₃ by 107% due to the better compatibility resulting in lower interface thermal resistance and more effective thermal transfer caused by the participation of BN-DOPO and DOPO-PA into epoxy curing reactions.

Viscoelastic liquids are of great interest for industrial and engineering applications due to their unique properties. This research presents a comparative examination of tri-nanomaterial Darcy-Forchheimer flow, involving Oldroyd-B, Maxwell, and Jeffrey (OMJ) nanofluids, over a permeable stretching sheet. The analysis integrates the influences of quadratic thermal radiation, activation energy, magnetic field, and heat source. Additionally, Buongiorno’s model has been utilized along with convective thermal boundary conditions. By leveraging local non-similar approach (LNSA), the modelled highly nonlinear partial differential equations (PDEs) are transformed into a set of ordinary differential equations (ODEs) which are further solved using the finite-difference-based bvp5c solver. It is determined that a rise in the Forchheimer parameter reduces the velocity field. The least and highest temperature profile is observed for Maxwell and Oldroyd-B nanofluids, respectively. It is further noted that per-unit increase in the Forchheimer parameter declines the drag coefficient by 15.43%, 23.87%, and 14.49% for Oldroyd-B, Maxwell, and Jeffrey nanofluid, respectively. As the temperature ratio raises, the heat transfer rate and mass transfer rate increase. Additionally, it is seen that the Oldroyd-B has the highest transfer rates followed by Jeffrey and Maxwell nanofluid.

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