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Volume 14 (2023), Nr. 3 - View full issue

Influenta filtrelor din componenta CTA-urilor asupra eficientei energetice
The influence of filters in the structure of air treatment plants units (ATP) on energy efficiency
Marius Adam, Adriana Tokar, Danut Tokar, Cristian Pacurar

The paper aims to analyze the major influence of filters on the consumption of electricity in ventilation systems, especially in air treatment plants in accordance with ISO EN 16890. On-site measurements are made with the help of the air treatment plant within the HVAC laboratory, with a flow rate of 2700 m3/h, on two filters with dimensions of 287 mm x 592 mm x 500 mm. The results indicate an energy class C for the analyzed filter. As future directions of study for the achievement of energy efficiency within an HVAC system, simulation with the help of the TRNSYS software can be used, for different scenarios.

Keywords: air handling unit, filters, energy efficiency, HVAC

Reducerea consumului de energie prin inlocuirea aeratoarelor de suprafata cu aerare cu bule fine in Statia de Epurare a Apelor Uzate Slobozia, Romania
Reduction of energy consumption by replacing surface aerators with fine bubble aeration in Slobozia Wastewater Treatment Plant, Romania
I. Bratu, A. Stamelaki

The biological process in a conventional wastewater treatment plant is one of the largest consumers of energy in wastewater treatment technology. The biological process can use from about 50% to 90% of the electricity used by a treatment plant (depending on its size and technological solutions used), while the cost of energy used can be up to 15–49% of the total costs of an installation. In Slobozia Wastewater Treatment plant, the energy consumption and operational costs were very high, due to the use of surface aerators in the biological tanks. In order to optimize the biological treatment and energy consumption, the present paper analyses the replacement of surface aeration with a fixed grid aeration system with membrane diffusers. By using a fine bubble aeration – lobe blower system, optimized regarding number of diffusers, aeration grids sizing, membrane material, membrane perforations size, blower motor power, the energy consumption in a wastewater treatment plant was considerably reduced and the oxygen transfer efficiency (SAE kgO2/kWh) was increased.

Keywords: wastewater treatment plant, optimization

Materialele de constructie si viitorul solutiilor alternative
Building Materials and the Future of Alternative Solutions
A. Grecu

While conventional materials like hemp could be employed as a lowcost, low-carbon method of reinforcing concrete, building intelligent materials are the future of efficient manufacturing.A new breakthrough in the industry is currently being promised by at least 10 novel construction materials, including plastic that is stronger than steel and 3D-printed mushroom columns.A lot of effort was put into developing biochar cladding, carbon-fiber reinforced concrete, super-strong plastic, and 3D-printed mycelium with the goal of preventing issues like corrosion and fire as well as prolonging the lifespan of concrete structures.Additionally, materials like green charcoal loofah make it possible for the bricks to serve as a habitat for both plant and animal life, boosting the biodiversity of cities.

Keywords: building materials, alternative solutions

Managementul schimbării lanțului de aprovizionare în turism după Covid-19: cazul operatorilor de turism
Tourism supply chain post covid-19 change management: the case of tour operators
R Karsokiene, A Giedraitis

The relevance of this paper is that that covid-19 outbreak, which has been announced by WHO (World Health Organization) on the 30th of March, 2020 and two years later still has continuous effect over most of the world, has caused blockages in all economic sectors, but tourism and its supply chain has been affected the most. The conducted research explores inner-organizational alterations within the tourism supply chain (TSC) management, though the prism of tour operators, in times and post pandemic. Tourism supply chain management strategies have already been adopted by many large tourism service providers, such as hotels and airlines. Therefore the article‘s main focus is on successful tour-operator change management within the chain, addressing the key elements. Study results present the impact caused by the outbreak on tour-operators in Lithuania and accordingly suggest the template for resilience. Furthermore, an interview based systematic crisis resilience model for tourism supply chain management is introduced.

Keywords: tour operators, Covid-19, tourism supply

Eficientizarea energetica a cladirilor de invatamant utilizand panouri fotovoltaice si pompe de caldura aer-apa. Studiu de caz
Energy efficiency of educational buildings using photovoltaic panels and air-water heat pumps. Case Study
Daniel Muntean, Adriana Tokar, Danut Tokar

Considering the current energy context, with the increase in the price of natural gas and electricity, the use of renewable energy has recently had an increasing trend. In this sense, the article presents a case study for the energy efficiency of educational buildings, through the installation of photovoltaic systems and air-water heat pumps. The simulation was carried out with the help of the Polysun calculation program, analyzing the energy consumption of the ASPC building of the Faculty of Construction in Timișoara, in the existing situation and in the proposed efficiency stages. The results show that in the first stage of efficiency in which the photovoltaic PV system and the air-water heat pump are installed, a decrease in costs for the necessary thermal and electrical energy is achieved, by 42.36%. In the second stage, in which it is proposed to decrease the return/return temperature regime of the indoor installation from 60/40 ℃ to 40/30 ℃, the result is a decrease in the electricity consumption from the national network by 7.94%.

Keywords: energy efficiency, photovoltaic panel, heat pump

Alternativ material de constructie termoizolant fabricat prin spumarea deseului de sticla cu antracit sub efectul radiatiei microundelor
Alternative thermal insulation building material manufactured by expanding the glass waste with anthracite under the effect of microwave radiation
Lucian Paunescu, Sorin Mircea Axinte, Felicia Cosmulescu, Bogdan Valentin Paunescu

Sticlă celulara cu excelente proprietati termoizolante (densitate de 0,27 g/cm3 si conductivitate termica de 0,053 W/mK) si rezistenta acceptabila la compresiune (2,7 MPa) a fost produsa din deseu de sticla, fosfat disodic (5,7 %) ca agent de stabilizare a spumei si antracit (0,9 %) ca agent carbonic de spumare, prin sinterizare cu microunde la 793 ºC. Antracitul a fost folosit pentru prima oara in cuptoare cu microunde intr-un proces original. Eficienta energetica a procesului (0,66 kWh/kg) a fost remarcabila fata de procesele conventionale datorita vitezei de incalzire semnificativ mai inalta fata de vitezele utilizate in procesele conventionale, fara afectarea microstructurii omogene a produsului. Acesta este adecvat utilizarii ca material termoizolant in constructii.

Cuvinte Cheie: sticla celulara, microunde, antracit, agent de spumare, fosfat disodic, material termoizolant.

Cellular glass with excellent thermal insulation properties (density of 0.27 g/cm3and thermal conductivity of 0.053 W/mK) and acceptable compressive strength (2.7 MPa) was produced of glass waste, disodium phosphate, (5.7 %) as foam stabilizing agent and anthracite (0.9 %) as carbonaceous expanding agent by microwave sintering at 793 ºC. Anthracite was used for the first time in microwave ovens in an original process. The process energy efficiency (0.66 kWh/kg) was remarkable compared to the conventional processes due to the heating rate significantly higher than the rates used in conventional processes, without affecting the product homogeneous microstructure. This is suitable for using in building as a thermal insulation material

Keywords: cellular glass, microwave, anthracite, expanding agent, disodium phosphate, thermal insulation material.

Caracterizarea betonului autocompactant amestecat cu argilă calcinată - corelația dintre doza de super-plastifiant și proprietățile betonului autocompactant
Characterization of Calcined Clay Blended Self Compacting Concrete-Correlation between Super-plasticizer dosage and Self-Compacting Concrete Properties
Kumator J. Taku, Bilkisu Amartey, George Gondo, K. G. Avre Chinedu Eze

Sustainability in the construction industry is essential to economic development and can be achieved by the use of locally available construction materials. This research work, thus, uses locally available materials –calcined clay and Sandcrete SPR-300 superplasticizer in the production of Self Compacting Concrete (SCC) by investigating the correlation between the superplasticizer dosage and the fresh and hardened states properties of a grade 30 SCC made by incorporating a Calcined Clay (CC) – Portland Limestone Cement (PLC) blend as the cementitious material at 15% replacement of PLC with CC and using CC as filler. The superplasticizer dosage was varied from 0.0 to 3.0% by weight of cementitious material and the fresh state properties - measured using slump flow tests, v-funnel time test and L-box test – as well as strength parameters investigated. The result shows a positive correlation between the increased dosage of the superplasticizer and the fresh and hardened states properties of the SCC up to 2% dosage of the SCC. The J¬Spread¬, t¬500J¬, Slump flow, L-box H¬2¬/H¬1 ¬ratio and strength, all increases with SP dosage while the V-funnel flow decreased with SP dosage. Overall, SP ratio of 1.5 and 2.0% by mass of cementitious material can be used in improving the properties of SCC produced using calcined clay both as filler and SCM. However, because of the volume of clay used and the nature thereof, the target strength could not be reached. It is therefore recommended that SP dosage of Sandcrete SPR-300 of between 1.5 and 2.0% be used with calcined clay as SCM but different filler, like limestone powder, be used.

Keywords: Calcined Clay, Compressive Strength, Fresh-state Properties of SCC, Self-Compacting Concrete, Superplasticizer dosage.

Procedura simplificata de evaluare a sistemelor fotovoltaice
Simplified PV panels system energy evaluation procedure

Lucrarea prezentata reprezinta o metodologie simplificată de evaluare a sistemului fotovoltaic in ceea ce priveste energia generata, acoperirea globala a cererii de energie a sistemului analizat, energia suplimentara necesara din retea si performantele sistemului la modificarea parametrilor de montaj. Ecuatii propuse si legatura cu metodologia nationala MC001 si anexele acesteia, lucrarea propune o evaluare rapida a aspectelor economice si a perioadei de rambursare. S-a demonstrat ca investitiile in astfel de sisteme sunt rambursate rapid in perioade de la 4 pana la 5 ani pentru consumatorul obisnuit cu un consum mediu zilnic de 11,15 kWh. In ultima parte a procedurii, a fost definit un parametru de suprafata specific consumatorului, util in calculul rapid a suprafetei solare nete totale a sistemului pentru a satisface un consumator cunoscut. In final, a fost studiata locația Bucurestiului, iar parametrii propuși de ecuatiile date au fost supusi unei evaluari de optimizare.

Cuvinte Cheie: Energie regenerabila, panou fotovoltaic, MC001, SEN

Presented paper represent a simplified methodology for evaluation of PV system with regards to generated energy, overall energy demand coverage of the system analyzed, supplementary energy required from the grid and performances of the system when mechanical parameters are changed. Proposed equations and link with Romanian national methodology MC001 and its annexes the paper proposes a quick evaluation for economic aspects and refund period. Was shown that investments in such systems are rapidly reimbursed in periods of 4 to 5 years for common household appliances consumer with a daily average consumption of 11.15kWh. In last part of the procedure, it was defined a specific consumer specific surface parameter, useful in rapid return of system total net solar surface to satisfy a known consumer. In the end, location of Bucharest was studied, and the parameters proposed by this paper equations where subjected to an optimization evaluation.

Keywords: Renewable energy, PV panel, MC001, SEN

Consideratii privind limitarea contributiei cladirilor la schimbarile climatice prin utilizarea eficienta a energiei
Considerations for limiting the contribution of buildings to climate change through efficient energy use
Adriana Tokar, Danut Tokar, Marius Adam, Cristian Pacurar, Daniel Muntean, Catalin Dragota

The incontestable evidence of climate change and extreme weather events has brought the entire world to the brink of a red code alert, which determined the need to establish targets for limiting greenhouse gas emissions and the other actions that can be taken to solve them. The paper presents aspects of limiting the contribution of buildings to climate change through energy efficiency measures with an emphasis on the importance of the nZEB concept. The need to reduce the consumption of energy from fossil sources and increase the contribution of energy renewable sources is discussed, in a realistic context.

Keywords: efficient energy, climate change, renewable sources, buildings

Influenta gradientului vertical de temperatura asupra conditiilor de lucru in hale industriale incalzite cu tuburi radiante. Studiu de caz
The influence of the vertical temperature gradient on working conditions in industrial halls heated with radiant tubes. Case Study
Dănuț Tokar, Mihai Cinca, Mirela Țoropoc, Adriana Tokar

The article analyses the variation of the vertically temperature gradient, in an industrial space heated with radiant tubes. Data monitoring was done with a workstation equipped with 5 high-performance temperature sensors. The temperature measurement was carried out in 5 distinct points inside/outside the production space, selected in different hypotheses, and a thermovision camera was used at the floor level. The values of the indoor air temperature measured at the level of the ankles, at the level of the work plane and at the level of the head of the people in the productive space fall within the normal limits.

Keywords: temperature gradient, working conditions, industrial halls, radiant tubes

Contributii la conceptul de casa pasiva prin utilizarea panourilor fotovoltaice
Contributions to the passive house concept through the usage of photovoltaic blinds
Dănuț Tokar, Daniel Muntean, Adriana Tokar, Marius Adam

The paper presents a study on the efficiency of installing photovoltaic blinds in a didactic laboratory with large glased surfaces, in order to ensure the shading of the interior spaces and to avoid the use of air conditioners during warm periods of the year, as a contribution to the passive house concept.

Keywords: photovoltaic bilds, passive house, thermal comfort, solar energy

Studiu comparativ a doua sisteme de incalzire/racire pentru o cladire de birouri utilizand software-ul Design Builder
Comparative study of two heating/cooling systems for an office building using Design Builder software
Mirela Toropoc, Adriana Tokar, Danut Tokar, Mihai Cinca, Marius Florin Oprea

The buildings sector is responsible for the largest percentage of total energy consumption, especially for heating and cooling. For this reason, the paper compares two heating/cooling systems (multisplit VRF and respectively chiller, central heating and fan coil units) for an office building. Energy consumption for heating/cooling, domestic hot water preparation and lighting, expressed in MWh/year, was analyzed. Following the simulation, the VRF air-conditioning system, which registers a global consumption of 70.23 MWh/year, compared to the system with a chiller, thermal plant and fan coil units, which registers a global consumption of 81.25 MWh/year, was found more advatageous

Keywords: global energy consumption, heating, cooling, building

Imbunatatirea transferului de caldura la radiatore folosind nanofluide
Radiator heat transfer enhancement using nanofluid
Emilian-Florin Turcanu, Vasilica Ciocan, Nelu-Cristian Chereches, Sebastian-Valeriu Hudisteanu, Ana Diana Ancas, Verdes Marina, Catalin-George Popovici

This research article presents a computational fluid dynamics (CFD) analysis of the heat transfer enhancement in a radiator using nanofluid. The study investigates the effect of varying the concentration of nanoparticles and the inlet velocity of the fluid on the heat transfer rate and pressure drop. The simulation results show that the use of nanofluids in radiators leads to a significant increase in heat transfer rate compared to traditional fluids. However, the pressure drop also increases with the concentration of nanoparticles, which can affect the overall efficiency of the radiator. The study provides valuable insights into the design and optimization of nanofluid-based radiators using CFD simulations.

Keywords: Nanofluids, Heat transfer enhancement, Thermal conductivity, Radiators, Nanoparticle concentration

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