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  Numarul 1/2012

Volumul 3 (2012), Nr. 1

Calculul focarelor tip tub de flacara cu pereti de inalta temperatura
Dimensioning of the tube furnaces with high surface temperature
Nicolae Antonescu, Dan-Paul Stanescu

In cazul generatoarelor de aer cald folosind arderea combustibililor, calculul focarului cu metoda clasica a invariantilor (Boltzmann - θf) are o aplicabilitate limitata, deoarece nu tine cont de temperatura peretelui focar, aceasta putind atinge valori semnificative in cazul agentului secundar gazos. Lucrarea de fata se axeaza pe identificarea unor metode alternative de calcul pentru focarele tip tub de flacara cu agent secundar aer si pe metodica de determinare a temperaturii peretelui focar. Luand in considerare o serie de parametrii definitorii cum ar fi temperatura peretelui focar, incarcarea termica volumica, viteza de circulatie a gazelor de ardere, viteza de circulatie a aerului si geometria suprafetei de transfer, se determina erorile ce apar prin folosirea metodei clasice si se analizeaza functional focarul la variatia parametrilor amintiti.

In hot air generators using fuel combustion, furnace calculation by the classical invariants empiric equation (Boltzmann - θf) has a limited application for gaseous secondary agent because it does not take into account the temperature of the furnace wall that can reach significant values. This paper focuses on identifying alternative methods for calculating the tube type furnaces with air as secondary agent and identiffies a method for determining furnace wall temperature. Taking into account a number of defining parameters such as furnace wall temperature, volumic thermal load, flow speed of the flue gases, air circulation and transfer surface geometry, we determine the errors that occur using conventional method and analyze the functional parameters.

Metode de fundamentare a deciziilor in analiza tehnico-economica a randamentului sistemelor de irigatii
Decision - make methods in technical-economic analysis of irrigation systems efficiency
Gheorghe Iordache, Alin Trifan, Marian Dordescu, Anca Constantin, Lucica Rosu

In aceasta lucrare, este prezentata o abordare multicriteriala a tehnicilor de decizie, utilizate in managementul amenajarilor de irigatii. Analiza economica a fost realizata utilizind metoda Electre III in cadrul careia se cuantifica importanta relativa a criteriilor considerate. Alegerea pragurilor este determinata de specificitatea fiecarui criteriu, astfel incit sa reflecte preferinta factorului de decizie. Prin relevarea zonelor cu eficienta economica scazuta, analiza realizata contribuie la imbunatatirea deciziilor care trebuie luate, constituind un important punct de plecare pentru alegerea celor mai bune metode de modernizare a amenajarilor de irigatii. Lucrarea prezinta o analiza a unor importante criterii de evaluare a eficientei sistemelor de irigatii in Sistemul hidrotehnic "Carasu - Nicolae Balcescu", judetul Constanta.

This study presents a multi-criteria approach for decision techniques used in irrigation system management. Economical analysis was made using Electre III method which counts the relative importance of the considered criteria. The level of importance is awarded by the decision-maker according to each specific criterion. By identifying the low economic efficiency areas, the analysis leads to the decisions improvement. It allows us to choose the best modernizing methods for the irigations systems. This study reaveals the analysis of the most important criteria evaluation of the irrigation system eficiency for Nicolae Balcescu hydrotechnical system which is part of Valea Carasu's irigation system.

Determinarea factorilor de influenta ai consumului de energie electrica in statia de epurare Oradea
Determining factors that influence energy consumption in Oradea WWTP
Gheorghe-Constantin Ionescu, Emil Gligor, Florin Dan

Statiile de epurare sunt consumatori importanti de energie electrica din sistemul energetic national. Determinarea factorilor ce influenteaza consumul de energie electrica este primul pas in reducerea costurilor cu energia electrica, cost care detine un procent important in costul total de operare al statiei, consumul lunar fiind de 200 - 500 MWh, ceea ce conduce la un cost de 60.000 - 150.000 RON intr-o luna la un pret de 300 RON/MWh. Determinarea factorilor care influenteaza consumul de energie electrica este primul pas catre procesul ulterior de prognoza a consumului de energie electrica.

Wastewater treatment plants are important consumers of municipal electricity from the national energy system. Determining the factors that influence this electric energy consumption is the first step in reducing the costs of these energy consumption which is an important part of operating costs, monthly consumption ranging between 200-500 MWh per month depending on the capacity which leads to a significant monthly operating cost between 60.000 and 150.000 RON / month at a price 300 RON / MWh. The electric energy consumption influence factors identification contributes to the ulterior process of electric energy forecast.

Determinarea procentului de articulatie (gradului de inteligibilitate) in sala teatrului "EXCELSIOR"
Determination of the rate of articulation and degree of intelligibility in "EXCELSIOR" theater hall
Mariana Cristina Stan, Ioana Mihaela Alexe, Alexandru Radu Stan

Lucrarea prezinta determinarea procentului de articulatie (gradului de inteligibilitate) in sala teatrului "Excelsior" din Bucuresti si compara rezultatele obtinute cu valorile precizate in standardul STAS 9783 / 0 - 84 "Acustica in constructii. Parametrii pentru proiectarea si verificarea acustica a salilor de auditie publica. Clasificare si limite admisibile"

This article presents the determination of the rate of articulation and of the degree of intelligibility in "Excelsior" Theatre Hall in Bucharest and compares the obtained results with the values given by the standard STAS 9783/0-84 "Building acoustics. Parameters for designing and acoustical cheking of auditoria. Clasification and permissible limits"

Performantele betoanelor preparate cu cimenturi cu adaosuri
Performance of concrete prepared with cements with additives
Dan Paul Georgescu, Adelina Apostu, Radu Gavrilescu, Tudor Seba

Articolul prezinta rezultatele unor cercetari experimentale privind caracteristicile de rezistenta si durabilitate (absorbtie, porozitate, permeabilitate, rezistenta la inghet-dezghet, carbonatare) a betoanelor preparate cu diferite tipuri de cimenturi. Extinderea domeniilor de utilizare a cimenturilor avind mai mult de 21% adaosuri a devenit o necesitate in toata lumea deoarece aduce avantaje importante prin reducerea emisiei de CO2 si a consumului de energie, in industria cimentului. In trecut, in Romania au fost utilizate, in putine cazuri, aceste tipuri de cimenturi si, in general, numai pentru betoane de rezistenta scazuta. Astfel, utilizarea cimenturilor cu adaosuri in betoane avind rapoarte A/C ridicate conduce la o comportare necorespunzatoare in timp si nu poate oferi o imagine reala a potentialului acestor tipuri de cimenturi. Cercetarile efectuate prezinta valorile experimentale ale parametrilor care caracterizeaza rezistenta si durabilitatea betoanelor preparate cu anumite cimenturi cu adaosuri.

The paper presents results of experimental research on the characteristics of strength and durability (absorption, porosity, permeability, resistance to freeze-thaw, carbonation) of concrete prepared with different types of cements. Expanding the field of use of cements with more than 21% additives has become a necessity because everyone brings important benefits in reducing CO2 emissions and energy consumption in cement industry. Back in Romania were used, in many cases, these types of cements and, in general, only low strength concrete. Thus, use of cement with additives in concrete reports with A / C high lead to inappropriate behavior in time and can not provide a true potential of these types of cements. Research conducted shows the experimental parameters that characterize strength and durability concrete prepared with some cements with additives.

Management si calitate in constructii
Construction management and quality
Nicolae Postavaru

 
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