Lucrarea analizează dimensionarea instalațiilor solare termice utilizate pentru încălzirea clădirilor și prepararea apei calde de consum, prin introducerea unui parametru esențial de optimizare: raportul dintre capacitatea de transfer termic a clădirii și suprafața de captare solară (H/SC). Pe baza acestui indicator, este evaluată performanța unui sistem solar instalat într-o clădire colectivă situată în Zona Climatică II (București), utilizând captatoare plane cu kC = 3 W/m²K și un regim de temperatură scăzut (50/30°C). Studiul include determinarea parametrilor termici ai buclei solare, analiza randamentelor lunare, calculul gradului de acoperire energetică și evaluarea balanței energetice sezoniere. Rezultatele arată o contribuție solară semnificativă în perioadele de tranziție (martie–aprilie, septembrie–octombrie), cu acoperiri ce depășesc 100%, dar o eficiență redusă în sezonul rece (15–30%). Sunt analizate trei scenarii de dimensionare (H/SC = 1.3, 11.3 și 52.2), evidențiind compromisurile dintre investiție, performanță și riscul de supraproducție. Concluzia principală este că dimensionarea optimă se obține pentru lunile de tranziție (octombrie/aprilie), în timp ce dimensionarea pentru luna critică (decembrie) devine neeconomică fără stocare sezonieră sau surse auxiliare.

Cuvinte Cheie: instalații solare termice, performanță energetică, sursă auxiliară

This study investigates the sizing of solar thermal systems used for space heating and domestic hot water production by introducing a key optimization parameter: the ratio between the building’s thermal loss coefficient and the installed solar collector area (H/SC). Using this indicator, the performance of a solar thermal installation serving a multi‑apartment building located in Climate Zone II (Bucharest) is evaluated. The system employs flat-plate collectors with kC = 3 W/m²K and operates under a low‑temperature regime (50/30°C). The analysis includes the determination of thermal transfer modules, monthly efficiency assessment, calculation of the solar coverage factor, and evaluation of the seasonal energy balance. Results show high solar contribution during transition months (March–April, September–October), often exceeding 100%, while winter performance remains limited (15–30%). Three sizing scenarios (H/SC = 1.3, 11.3, and 52.2) are compared, highlighting the trade‑offs between investment cost, energy yield, and risk of seasonal overproduction. The study concludes that optimal sizing is achieved when the system is dimensioned for transition months (October/April), whereas sizing for the critical winter month (December) becomes economically inefficient without long‑term thermal storage or auxiliary energy sources.

Keywords: solar thermal systems, energy performance, auxiliary source

The development of numerical analysis and the significant progress made in the field of computing have made it possible to consider the increasingly complex behaviour of geomaterials. Using the finite element method and an elastoplastic approach, a model of the behaviour of an axially loaded soil–pile system is proposed. The effect of soil–structure interaction is incorporated through interface elements. The soil is represented by a MohrCoulomb model with perfect plasticity. For the numerical analysis of soil–pile behaviour, a nonlinear finite element computation code has been developed. Ultimate loads are determined for a pile subjected to axial compression and tension. The results obtained highlight the importance of the contact zone on the distribution of stresses within the soil.

Keywords: Geo-materials, soil–structure interaction, elastoplastic behaviour, piles, interface elements, ultimate loads.

This paper presents an in-depth experimental and analytical study focused on evaluating the performance of sprinkler systems used in fire suppression. The research explores the interaction between droplet distribution, droplet velocity, kinetic energy, and their role in effective fire control. Various measurement and evaluation methods were applied, including Laser Precipitation Monitors (LPM), image processing techniques, and multiple coefficients for distribution uniformity. The study also details a flexible and mobile experimental stand developed to test different types of sprinklers under controlled conditions. Conclusions are drawn based on data gathered from both field and laboratory conditions, offering practical recommendations for system configuration, operation, and optimization.

Keywords: Fire suppression, sprinkler systems, droplet size, CFD simulations, performance evaluation

The relation between air quality and human health is one of the most welldocumented contemporary public health topics and this is determined by the interaction between air pollutants and the body's physiological systems.

Keywords: indoor air quality, ambiental comfort, thernal comfort, productivity, performance, environmental quality

The standard for the design, execution, and operation of ventilation and air conditioning installations, indicative of I5/2022, establishes four indoor air quality categories for the occupied area of civil premises. For residential civil buildings, the main source of pollution is bio-effluents emitted by humans. This article presents the result of measuring the CO₂ concentration values recorded in three buildings during the period when there were no users. The analysis of the recorded results does not show any causal links between the way ventilation is performed, through infiltration through leaks or mechanical ventilation with heat recovery, and the variation in indoor CO₂ values

Keywords: ventilation, CO2 concentration, indoor air quality

Lucrarea a vizat producerea unei sticle celulare cu porozitate ridicată, utilizând o rețetă compusă din deșeuri de sticlă sodă-calciu-silice, borax ca agent de flux și soluție apoasă de KOH ca agent de expansiune. Procesul de încălzire pentru sinterizare/spumare s-a bazat pe iradierea cu microunde, o tehnică neconvențională cunoscută, dar practic neutilizată în aplicații la temperaturi înalte până în prezent. Rezultatele au arătat că s-a obținut densitatea de 0,26 g·cm-3, conductivitatea termică de 0,069 W·m-1·K-1 și rezistența la compresiune de 1,6 MPa, corespunzătoare variantei optime. Originalitatea lucrării constă în utilizarea agentului de spumare lichid și aplicarea tehnicii proprii de încălzire cu microunde.

Cuvinte Cheie: sticlă celulară, microundă, soluție de KOH, deșeu de sticlă, porozitate înaltă

The work aimed at producing a high-porosity cellular glass, using a recipe composed of soda-lime-silica glass waste, borax as a fluxing agent, and aqueous KOH solution as an expanding agent. The heating process for sintering/foaming was based on microwave irradiation, a known unconventional technique, but practically not used in high-temperature applications until now. The results showed that density of 0.26 g·cm-3, thermal conductivity of 0.069 W·m-1·K-1, and compressive strength of 1.6 MPa were obtained, corresponding to the optimal variant. The work originality consists in the use of the liquid foaming agent and applying the own microwave heating technique.

Keywords: cellular glass, microwave, KOH solution, glass waste, high-porosity

Lucrarea propune un model de calcul pentru temperatura cablurilor electrice îngropate în pământ, în tuburi de protecție. Transferul de căldură dintre cablu și pământ este analizat similar modului de propagare a căldurii prin aripioarele de răcire. Izolația cablului și tubul de protecție sunt derulate sub formă de lamele plate și se stabilește distribuția temperaturii în tub, temperatura zonei de contact și temperatura conductorului electric. Pentru un anumit cablu, coincidența rezultatelor cu cele din catalogul producătorului confirmă validitatea modelului.

Cuvinte Cheie: cabluri îngropate, încălzire conductori electrici, risc de incendiu la cabluri îngropate

The paper proposes a calculation model for the temperature of electrical cables buried in the ground, in protective tubes. The heat transfer between the cable and the ground is analysed similarly to the heat propagation mode through cooling fins. The cable insulation and the protective tube are unrolled in the form of flat blades and the temperature distribution in the tube, the temperature of the contact area and the temperature of the electrical conductor are determined. For a given cable, the coincidence of the results with those in the manufacturer's catalogue confirms the validity of the model.

Keywords: buried cables, heating of electrical conductors, fire risk in buried cables

This paper presents a TRNSYS 18 dynamic model of a three-zone dwelling in Iași, Romania, with a conditioned floor area of 224 m² and an enclosed volume of 747 m³. The model couples climate processing, solar-radiation conversion, ground interaction, a TRNBUILD multizone building, a thermostat, and an air-source heat pump. Using the uploaded annual plots, the study interprets incident solar radiation, indoor/outdoor temperatures, zone-specific heating and cooling loads, and heat-pump electricity use. The original contribution is the explicit mapping between TRNSYS component outputs and engineering indicators, together with a discussion of the current model-coupling limits and the pathway toward PV-battery integration.

Keywords: TRNSYS 18, air-source heat pump, residential building, heating and cooling loads

Educational buildings frequently face issues with overheating and high energy consumption associated with HVAC systems, amid rising global temperatures and increasing demands for thermal comfort. Night Ventilation (NV) has been recognized as an effective passive or semi-passive cooling technique that utilizes cooler outdoor air to discharge the building's thermal mass during the night, thereby creating a 'cool reservoir' for the following day. This article presents a case study on the implementation of night ventilation strategies in an educational building, aiming to evaluate energy efficiency and the impact on thermal comfort. The study analyzes the interaction between night ventilation rates, building thermal inertia, and the energy consumption of HVAC equipment during occupancy periods. The results demonstrate that an optimized night ventilation strategy can significantly reduce peak cooling loads and the number of thermal discomfort hours. Furthermore, the paper explores the economic cost-benefit ratio by comparing the energy consumption of fans during the night with the savings generated by the reduced use of HVAC systems during the day. The study emphasizes that, although night ventilation cannot always independently ensure full thermal comfort, its integration as part of a hybrid cooling system is a feasible and energy-efficient solution for educational buildings.

Keywords: Night ventilation; HVAC efficiency; educational buildings; thermal mass; energy savings; thermal comfort

Urban areas face growing flood risks and hydraulic overloads due to climate change, urban densification, and the expansion of impervious surfaces. In this context, decentralized rainwater management is increasingly recognized as a valuable complement to conventional drainage systems. This paper outlines the principles and policy context of decentralized rainwater harvesting and infiltration, with a focus on nature-based and building-scale solutions that align with European water policies. The practical application of these approaches is illustrated through a case study of a decentralized rainwater harvesting and infiltration system implemented in an educational building in Cluj-Napoca, Romania. The findings demonstrate that such systems can reduce stormwater discharge, support non-potable water reuse, and improve urban water resilience.

Keywords: decentralized rainwater management; stormwater management; urban resilience; nature-based solutions; rainwater harvesting; infiltration systems

This paper presents a comparative analysis of three radiant heating systems—floor, ceiling, and hybrid floor–ceiling—applied to a 20 m² office room under winter conditions. The objective is to evaluate their thermal behavior and energy performance under identical operating conditions. The analysis is based on numerical simulations, focusing on indoor air temperature evolution, thermal energy delivered, and system efficiency. The results show that all systems maintain indoor temperatures close to the setpoint value of 22 °C, with minor differences in thermal response. The hybrid floor–ceiling system achieves the highest energy performance, with SCOP values up to 4.9, due to improved operating conditions of the heat pump. The floor heating system ensures the highest thermal stability, while the ceiling system exhibits slightly higher variability and lower efficiency. The findings highlight the advantages of hybrid radiant configurations in improving energy efficiency and maintaining adequate thermal comfort in office buildings.

Keywords: Geothermal heat pump; Radiant heating; Hybrid radiant heating system; Energy efficiency; Thermal comfort

Urban areas consume over 65% of global energy, much of which is used for street and public lighting. As energy costs rise and the need to reduce CO2 emissions grows, smart lighting emerges as a key strategy for energy conservation, safety, and urban aesthetics. Cities are adopting energy-efficient LEDs and smart systems with features like dimming and safety controls, allowing real-time, remote management of lighting based on area usage. Though implementing smart systems city-wide is costly, a gradual approach targeting specific areas can be effective. Lampposts equipped with connected lighting can provide additional services, such as public Wi-Fi and support for IoT sensor networks, which monitor environmental factors like air quality and waste management. Smart lighting can reduce energy consumption by 50-70% without compromising safety, enhancing the city’s appeal and attracting visitors and investments.

Keywords: reducing CO2 emissions, energy efficiency, lamppost, smart lighting

The protection of hospital infrastructure during extreme events represents a fundamental requirement for civil protection systems. The present study evaluates the engineering design of a civil protection shelter integrated in the Mioveni Hospital project. The analysis focuses on ventilation performance, NBC filtration efficiency, sanitary autonomy and pressure control mechanisms required to maintain safe environmental conditions. Engineering calculations are presented for airflow demand, pressure losses, filtration efficiency and system reliability under conventional warfare scenarios, biological and chemical contamination scenarios and nuclear events.

Keywords: civil protection shelter, hospital resilience, NBC filtration, ventilation systems, overpressure protection

Thermography is a method used for rapid and accurate diagnosis of the energy status of buildings, which can identify obvious problems, reduce uncertainties or identify anomalies (that could be neglected) before they cause serious problems. The present study addresses the thermography method for a building that was brought from efficiency class G to class C by optimizing the installation systems that provide space heating and cooling, as well as hot water for consumption. The thermography method identified the areas of the building envelope elements where energy leaks are recorded and proposed measures to reduce or even eliminate these losses so that the building can be classified in higher energy classes.

Keywords: energy losses, thermography, energy efficiency, measures, energy class

This article analyzes the relationship between the integration of biophilic design principles in architecture and the energy performance of buildings. Strategies such as natural lighting, natural ventilation, and the integration of vegetation are evaluated, highlighting their impact on energy consumption and indoor comfort. The study demonstrates that biophilic design is not only an aesthetic approach, but also an effective tool for optimizing the energy performance of the built environment.

Keywords: biophilic design, natural ventilation, materiality, vegetation, stack effect (natural draft), skylight, orientation

This study analyses the benefits of integrating high-entropy alloys (HEAs) into HVAC systems using 3D printing technologies. The results indicate high performance in corrosive environments and under thermal stress, optimizing critical components such as fans and heat exchangers. The paper introduces cost-effective repair methods and advocates for the standardization of additive manufacturing processes to maximize the impact of HEAs in high-performance industrial applications

Keywords: 3D printing, High-Entropy Alloys, HVAC system, additive manufacturing

Construction advances in 3D concrete printing boost design freedom, but reinforcement bars present obstacles. Incompatibility with 3D printing, positioning and accuracy issues, concrete adhesion issues, synchronization issues, and corrosion and fractures are major obstacles. To solve these problems, the use of fiber and other methods is necessary. Digital control and robotics improve printing accuracy, but the lack of standards makes study validation and comparability difficult. Since present techniques weaken automation and structural strength, rebar integration must be addressed. To improve 3D concrete printing, future research must combine materials science, mechanics, and robotics.

Keywords: 3D concrete printing, reinforcement bars, Incompatibility, rebar integration

Prezenta lucrare are ca obiectiv studiul confortului termic în corturi militare, prin analiza numerică a unui cort utilizat ca adăpost temporar pentru personalul militar, în condiții climatice de vară. Tema a fost aleasă pornind de la importanța structurilor temporare în activități militare, intervenții operative sau situații în care personalul trebuie să desfășoare activități în teren deschis. Scopul principal al lucrării a fost evaluarea confortului termic într-un cort militar, prin compararea mai multor scenarii de simulare și prin identificarea soluțiilor care pot reduce supraîncălzirea și pot îmbunătăți calitatea mediului interior. Rezultatele obținute sunt încurajatoare și vor trebui confirmate printr-o campanie experimentală.

Cuvinte Cheie: confort termic, calitatea aerului interior, corturi militare

The present paper presents a study of thermal comfort in a military tent, through numerical analysis using dynamic simulations, under summer climatic conditions. The topic was chosen based on the increasing importance of temporary structures in military activities, operational interventions, training camps or situations in which personnel must carry out activities in open field. The main goal was to evaluate thermal comfort in a military tent, by comparing several operational scenarios and by identifying solutions that can reduce overheating and improve the quality of the indoor environment. The results obtained are promising and should be confirmed by an experimental campaign.

Keywords: thermal comfort, indoor air quality, military tents