Explore the vast range of titles available.

The present work applied the Logarithmic Mean Divisia Index methodology to decompose energy consumption in Lithuania, Poland and Slovakia by using a seven-factors equation. The equation allows to highlight the contribution of activity, structure, and intensity components on the energy consumption, jointly with other factors such as climatic conditions, energy consumption per capita, and the impact of district heating sectors which is relevant for the considered countries. Overall, it can be said that the activity component is responsible for a sharp increase in consumption. In contrast, the intensity consumption determines a strong decrease. Finally, the analysis shows that there is an overall increase in district heating consumption attributable to a decrease of the customers’ basis.

In this article, developing turbulent forced convection flow of a water-Al 2 O 3 nanofluid in a square tube, subjected to constant and uniform wall heat flux, is numerically investigated. The mixture model is employed to simulate the nanofluid flow and the investigation is accomplished for particles size equal to 38 nm. An entropy generation analysis is also proposed in order to find the optimal working condition for the given geometry under given boundary conditions. A simple analytical procedure is proposed to evaluate the entropy generation and its results are compared with the numerical calculations, showing a very good agreement. A comparison of the resulting Nusselt numbers with experimental correlations available in literature is accomplished. To minimize entropy generation, the optimal Reynolds number is determined.

This study explores the impact of using water-Al2O3 nanofluids, at different nanoparticle concentrations, in solar thermal collectors for solar cooling applications. Improving the seasonal energy performance of solar cooling systems is a current research priority, and this work investigates whether nanofluids can significantly enhance system efficiency compared to traditional heat transfer fluids. A transient simulation was carried out using a dynamic model developed in TRNSYS (TRANsient SYstem Simulation), evaluating the system performance throughout the cooling season. The results show that in July, under low volumetric flow conditions and with nanoparticle concentrations of 0.6% and 0.3%, the solar fraction reaches a maximum value of 1. Using a nanofluid at 0.6% concentration leads to significantly higher fractional energy savings compared to pure water. Despite increased pumping energy, the overall energy savings—which include the contribution from an auxiliary boiler—exceed 80% when nanofluids are used. This study goes beyond previous work by providing a dynamic, system-level simulation of nanofluid-enhanced solar cooling performance under realistic operating conditions. The findings demonstrate the practical potential of nanofluids as a valid and more energy-efficient alternative in solar thermal applications.

Thermal management in heat exchangers is crucial in many industrial, medical, and scientific applications. However, reducing dependency on active energy sources still represents a substantial challenge. In this context, phase change materials (PCMs) offer an effective solution due to their ability to store and release large amounts of latent heat, assisting in passive thermal management. Therefore, this study proposes the use of RT42 PCM inside a box-type shell-and-tube configuration to establish the relationship between flow rate and charging and discharging behavior of PCM. In the proposed system, heat transferring fluid (HTF) water is circulated in the internal tubes at 60 °C, where the temperature is monitored by a series of thermocouples strategically placed inside the box-type configuration. To evaluate the effect of the flow of HTF on the thermal behavior of the PCM, the charging (melting) and discharging (solidification) analysis is performed by varying the water flow rate at three levels: 1.2, 0.8, and 0.4 L/min inside the laminar region (Re < 2300). A thermal camera and two webcams were used to assess the surface temperature distribution and PCM response, respectively. It was determined that increasing the flow rate accelerates charging and discharging with fluctuations in temperature curves during melting.

The significant energy consumption and contribution to greenhouse gas emissions by the construction sector need careful attention to explore innovative sustainable solutions for improving the energy efficiency and thermal comfort of building envelopes. The integration of phase-change materials (PCMs) into building commodities is a favorable technology for minimizing energy consumption and enhancing thermal performance. This review paper covers the impact of PCM incorporation into construction materials, such as walls, roofs, and glazing units. Additionally, it examines different embedding techniques like direct incorporation, immersion, macro and micro-encapsulation, and form and shape-stable PCM. Factors affecting the thermal performance of PCM-integrated buildings, including melting temperature, thickness, position, volumetric change, vapor pressure, density, optical properties, latent heat, thermal conductivity, chemical stability, and climate conditions, are elaborated. Furthermore, the latest experimental and numerical simulations, as well as modeling techniques, evident from case studies, are investigated. Ultimately, the advantages of PCM integration, including energy savings, peak load reduction, improvement in interior comfort, and reduced heating, ventilation, and air-conditioning dependence, are explained alongside the limitations. Finally, the recent progress and future potential of PCM-integrated construction materials are discussed, focusing on innovations in this field, addressing the status of policies in line with the United Nations Sustainable Development Goals, and outlining research potential for the future.

A numerical investigation on Latent Heat Thermal Energy Storage System (LHTESS) based on an aluminum foam totally filled with phase change material (PCM) is accomplished. The PCM used is a pure paraffin wax with melting over a range of temperature and a high latent heat of fusion. The LHTESS geometry under investigation is a vertical shell and tube. The corrugated internal surface of the hollow cylinder is assumed at a constant temperature above the PCM melting temperature. The other external surfaces are assumed adiabatic. The paraffin wax phase change process is modelled with the enthalpy-porosity theory, while the metal foam is considered as a porous media obeying to the Darcy-Forchheimer law. Local thermal non-equilibrium (LTNE) model is assumed to analyze the heat transfer in the metal foam. The governing equations are solved employing the Ansys-Fluent code. The numerical simulations results, reported as a function of time, and concerning the LHTESS charging phase, are compared in terms of melting time, average temperature and energy storage rate. The corrugated internal surface effect is analyzed with respect to the wavelength and wave amplitude of the corrugation.

In this paper, a two-dimensional numerical investigation on a prototypal solar chimney system integrated with an absorbing capacity wall in a south facade of a building is presented. The capacity wall is composed of a high absorbing plate and an assigned thickness of phase change material in metal foam. The chimney consists of a converging channel with one vertical absorbing wall and the glass plate inclined of 2°. The channel height inside the chimney is equal to 4.0 m, whereas the channel gap is at the inlet equal to 0.34 m and at the outlet it is 0.20 m. The thermal energy storage system is 4.0 m high. The numerical analysis was intended to evaluate the thermal and fluid dynamic behaviors of the solar chimney integrated with a latent thermal energy storage system. The investigation has shown that in all cases PCM has not fully melted during the day and the presence of aluminum foam inside the box attenuates the variation of temperatures during the day. The results show that the three different thickness of the thermal storage system present very similar fluid dynamic and thermal behaviors. For the analyzed configurations, the phase change material does not reach a total melting during the considered day.

In this paper, mixed convection in a horizontal channel partially filled with a porous medium and the lower wall heated at uniform heat flux is studied experimentally and numerically. A simplified two-dimensional problem is modelled and solved numerically. The domain is made of a principal channel and two channels with adiabatic walls, one upstream and the other one downstream the principal channel. The heated wall temperature profiles as a function of the Ri values are presented. Average Nusselt numbers are evaluated. The experimental test section is made up of a horizontal wall and a parallel adiabatic wall. The distance between the horizontal walls is equal to 40 mm. The porous medium is an aluminium foam and it is placed over the heated lower wall. The porous plate has a thickness equal to 20 mm. The aluminium foam has 10, 20 and 40 PPI. The experiments are performed with working fluid air. The Reynolds numbers investigated are between 5.0 and 250, these being in the laminar regime. The Richardson number, Ri, holds values in the range 1 2000. Results in terms of wall temperature profiles, local and average Nusselt numbers are presented for different Reynolds and Rayleigh number values. Some comparison between experimental and numerical results are accomplished.

Electric cars can be a turning point for climate problems. One of the main problems of electric cars is the thermal control of the batteries, since below and above a certain temperature range, the vehicle’s range decreases abruptly, creating inconveniences to the owners of these cars. The thermal control of lithium batteries for electric cars must take into account both the problems of thermal rise due to the operation of the battery itself, and the climatic conditions outside the vehicle that negatively affect the performance of the car, reducing both the autonomy and the battery life. In this study, a thermal control system based on a phase change material (PCM) partially filled with metallic foam is investigated to evaluate its possible use in the cooling of lithium batteries. A two-dimensional model is considered to numerically study thermal control with different chargedischarge cycles. The metal foam partially fills the PCM. The governing equations, written assuming the local thermal equilibrium for the metal foam, are solved by the finite volume method using the ANSYS Fluent commercial code. Different cases are simulated for different values of the external convective heat transfer coefficient. The results, carried out for metal foams and PCM, are given in terms of temperature and liquid fraction. In addition, some comparisons with pure PCM and fully foam filled PCM are provided within the thermal control system to show the advantages of the composite thermal control system with PCM inside the metal foam.

In this paper, results obtained by the numerical investigation on laminar mixed convection in triangular ducts, filled with nanofluids, are presented in order to evaluate the fluid dynamic and thermal features of the considered geometry by considering Al2O3/water based nanofluids. The system is heated by a constant and uniform heat flux also along the perimeter of the triangular duct section in H2 mode as thermal boundary condition and the single-phase model has been assigned for a Reynolds number value equal to 100. Results are given for different nanoparticle volume concentrations and Richardson number values ranging from 0% to 5% and from 0 to 5, respectively. Results, presented for the fully developed regime flow, show the enhancement of average convective heat transfer coefficients values for increasing values of Richardson number and particle fractions. However, wall shear stress and required pumping power profiles increase as expected. The PEC analysis showed that the use of nanofluids in mixed convection seems slightly convenient. It should be underlined that, at the moment, experimental data are not available to compare the numerical proposed model for mixed convection in horizontal triangular ducts with nanofluids.