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  Numarul 3/2016

Volumul 7 (2016), Nr. 3

Aspecte termice negative datorate circulatiei neuniforme a agentului termic in rezervoarele de acumulare
Negative thermal issues due to uneven heat circulation in storage tanks
Prof. dr. ing. Florin Iordache

Lucrarea de fata isi propune sa identifice efectele adverse asupra performantei unitatilor de stocare termica, cauzate de fluxul de apa fara incalzire uniforma prin ele. Ea modeleaza procesele de transfer de caldura in regim inconstant care au loc cu rezervoare de stocare a caldurii lichide si determina corelatiile dintre performanta de stocare termica si neuniformitatea miscarii debitului prin intermediul unitatii de stocare. Rezultatele sunt prezentate grafic, astfel consecințele suferite de performanta de stocare termica sa fie clare si ușor de asociat cu cauzele lor neuniformitatea de circulatie de catre unitatea de stocare.

The present paper aims at identifying adverse effects on the performance the thermal storage units, caused by non uniform heating water flow through them. It shapes the processes of heat transfer in unsteady regime that occur with heat storage tanks liquid and determine correlations between thermal storage performance and the unevenness of the movement of flow through the storage unit. The results are shown graphically so the consequences suffered by the thermal storage performance to be clear and easy to associate with their causes the circulation unevenness by storage unit

Monitorizarea starii unei parcari subterane si trecerea acesteia la stadiul de parcare inteligent
The monitoring status of an underground parking and the transition to the stage of smart parking
Cristina Gabriela Saracin, Marian Bizineche

Lucrarea de fata prezinta modul de realizare al unei platforme necesare monitorizarii starii unei parcari subterane. Notiunea de parcare inteligenta apare tot mai des datorita noilor tehnologii informatice. Aceasta lucrare raspunde urmatoarelor cerinte: cum se realizeaza dimensionarea unei parcari, cum se dimensioneaza instalatia de iluminat, cum se monitorizeaza numarul de masini care sunt intr-o parcare si cum se poate dezvolta aceasta platforma. Automatizarile realizate pe platforma au fost pentru: sistemul de ventilatie, sistemul de bariere intrare/iesire si sistemul de stingere a incendiilor. Pentru realizarea practica a acestei platforme am ales automatele programabile Easy 819 DC-RC şi Easy 719 DC-RC.

This paper presents the embodiment of a platform used to monitoring the condition of an underground parking. The concept of smart parking is increasingly confronted by the new information technologies. This work meets the following requirements: how to size the parking dimension, dimensioning of the lighting installation, how to monitor the number of cars parked in a parking lot and how to develop this platform. The automation performed on the platform are made for: ventilation system, entry / exit access barriers and firefighting system. For the physical implementation of this platform, there were chosen Programmable Logic Controllers such as Easy 819 DC-RC and Easy 719 DC-RC

Analiza energetica - sistem sursa hibrid. Cogenerare cu motore cu ardere interna si pompe de caldura
Energy analysis - source hybrid system. Internal combustion engine cogeneration and heat pumps
Prof. dr. ing. Florin Iordache, ing. Radu Alexandru Baciu

Lucrarea isi propune sa analizeze sursa de energie a unui sistem hibrid format dintr-un grup de cogenerare si un grup de pompe de caldura cu compresie. Cele doua grupuri de producere a energiei termice lucreaza n paralel. Grupuri de pompe de caldura folosesc energia electrica produsa de grupul de motoare cu ardere interna si este considerata a extrage energie din mediul lichid (ape subterane sau apa de suprafata libera). Evaluarea eficientei energetice a sistemului hibrid in ansamblu si performanțele sale. Analiza energetica este eficienta pentru un grup de consumatori din cladiri rezidențiale (incalzirea spatiului si consumul de apa calda), luand in considerare si clima din diferite perioade. Rezultatele sunt prezentate grafic intr-un mod mai sugestiv pentru ințelegerea corecta a aspectelor constructive si functionale.

This paper aims to analyze the energy source of a hybrid system consisting of a group of cogeneration and a group of heat pumps with compression. The two groups producing thermal power and working in parallel. Groups of heat pumps use electricity produced by the group of internal combustion engines and is considered to extract energy from liquid medium (groundwater or free surface water). Assessing the energy efficiency of the hybrid system as a whole and its performance. Energy analysis is effective for a consumer group capacity on type of residential buildings (space heating and hot water consumption), taking into consideration the request of climate different periods. The results are shown graphically in a manner more suggestive of proper understanding of constructive and functional aspects.

Experimental Study on Ammonia Finned Air-Coolers Working under Frosting Conditions
Rodica Dumitrescu, Anica Ilie, Alina Girip, Madalina Teodora Nichita, Alina Filip

Aceasta lucrare prezinta rezultatele experimentale obtinute in urma testarii unui racitor de aer cu suprafata aripata, care reprezinta vaporizatorul unei instalatii frigorifice cu amoniac. Studiul experimental s-a desfasurat pe un stand special proiectat pentru a asigura masurarea, controlul si achizitia de date. Experimentele s-au efectuat in regim stationar, pentru temperaturi de vaporizare ale amoniacului de -18C şi -10C si puteri de racire ale aerului cuprinse ntre 7.6kW si 18.3 kW. S-a urmarit influenta formarii si depunerii de bruma asupra performantelor termice ale racitorului de aer aripat, in functie de timp, in diferite conditii de functionare. Acestea din urma au fost reprezentate de: temperatura aerului dupa termometrul uscat si continutul de umiditate al aerului la intrarea pe suprafata de racire, ca si de temperatura de vaporizare a amoniacului. De asemenea, s-a studiat variatia caderii de presiune pe partea aerului, in diferite conditii de functionare ale instalatiei. Acest studiu experimental vizeaza problema permanent actuala a economiei de energie, prin baza de date pe care o ofera activitatii de proiectare, avand ca obiectiv cresterea performantei termice a vaporizatorului si a instalatiei frigorifice. In plus, prezenta lucrare abordeaza aspecte legate de protectia mediului inconjurator, prin aceea ca utilizeaza un agent frigorific natural. Amoniacul are impact nul asupra stratului de ozon si asupra incalzirii globale si este bine cunoscut pentru proprietatile sale termofizice superioare celor ale agentilor frigorifici de tip HFC.

This paper reports experimental data obtained for an ammonia air-cooling evaporator working under conditions of frost formation. The experimental study was carried out on a specially designed set-up that allowed measuring, control and acquisition of data. Experiments were conducted for ammonia evaporation temperature of -18C and -10C and cooling capacity from 7.6 kW to 18.3 kW, during steady state operating conditions. The experimental investigation aimed to determine the effect of frost formation and growth on thermal performances of the ammonia finned air-cooler, in time, under different operating conditions. Influence of air dry bulb temperature, air humidity ratio and evaporating temperature has been studied. Air side pressure drop, for the same dry bulb temperature and different humidity air ratio has also been studied. This experimental investigation on an ammonia air-cooling evaporator addresses the current issue of energy savings by assisting improved design of this type of heat exchangers in order to achieve higher thermal performances of evaporators and refrigerating systems. By using ammonia as a refrigerant, this experimental investigation addresses also current ecological issues linked to refrigerants. It is well known that apart from its attractive thermo-physical properties, as compared to HFCs, ammonia is also an environment friendly natural refrigerant, known for its zero ozone depleting potential and zero global warming effect.

Aspects concerning the use of binary ice for comfort air-conditioners
Madalina Teodora NICHITA, Rodica DUMITRESCU, Florea CHIRIAC

This paper refers to the use of ice-slurry, as an intermediary phase changing cooling fluid, in air-conditioning. Ice-slurry is provided by a scraper-type generator that is part of a single stage compression system working with R404A, as primary refrigerant. A mixture of ice-slurry, water, and talin (10% mass concentration) represents the secondary cooling medium. This was used in a heat exchanger of classical type, namely an air cooler, with aluminum fins, of 0.1 mm thickness. This paper reports experimental results of ice-slurry used as cooling fluid for air-conditioning consumers of various cooling capacity demands. Experiments have been carried out using two different ice mass fractions, namely approximately 15% and 20% and two different air volumetric flow rates, namely Qair = 3000 m3 / h and Qair = 2000 m3 / h The cooling capacity of the ice-slurry generator has been experimentally validated by simultaneously determining the thermal capacity for the evaporator (as a function power input to the compressor), for the air-cooler and air heaters

Analiza energetica privind un posibil sistem sursa hibrid
Energy analysis on a possible hybrid power system
Prof. dr. ing. Florin Iordache

Sursa hibrid propusa pentru analiza in lucrare se refera la motoarele cu combustie termica pe baza de cogenerare, cuplate cu pompe de caldura. Motoarele termice realizeaza primul pas prin incalzirea unui flux de caldura, cresterea in continuare a potentialului va fi realizat cu ajutorul pompelor de caldura. Sistemul hibrid mentionat realizeaza atat energie termica cat si energie electrica necesara pentru nevoile consumatorilor. Lucrarea prezinta o analiza a sistemului hibrid ca sursa de putere in comparatie cu sursa de baza a motoarelor termice. Performanta sistemului sursa hibrid si capacitatea instalata este determinata pentru sistemul hibrid sursa. Analiza energetica intreprinsa are ca scop identificarea performantei energetice a unui astfel de sistem

The proposed hybrid source for analysis in the paper refers to cogeneration based thermal combustion engines, coupled with heat pumps. Thermal engines performs the first step by heating a heat flow, further raising the potential will be realized with heat pumps. Mentioned hybrid system achieved both heat and electricity required for consumer needs. The paper presents an analysis of the system power hybrid source system compared to their base source of heat engines. Define performance of the hybrid source system and installed capacity is determined for the hybrid souces system. Energy analysis undertaken aims to identify energy performance of such a system.

Experimental Investigation on Frost Formation in Ammonia Finned Air-Coolers
Rodica Dumitrescu, Anica Ilie, Alina Girip, Madalina Teodora Nichita, Alina Filip

Aceasta lucrare prezinta rezultatele experimentale obtinute la testarea unui racitor de aer cu amoniac, in conditii de depunere de bruma pe suprafata de transfer de caldura. Obiectivul lucrarii este acela de a determina influenta unor factori cheie asupra vitezei de formare si acumulare a brumei pe suprafata rece, in diferite conditii de functionare. S-au studiat: influenta temperaturii si continutului de umiditate ale aerului la intrarea pe suprafata racitorului, precum si influenta temperaturii de vaporizare. De asemena, s-a studiat variatia densitatii brumei formate in functie de temperatura si continutul de umiditate ale aerului la intrarea pe suprafata racitorului. Studiul experimental s-a efectuat pe un stand special proiectat pentru a asigura masurarea, controlul si achizitia de date. Experimentele s-au efectuat in regim stationar, pentru temperaturi de vaporizare ale amoniacului de -18C si -10C si puteri de racire ale aerului cuprinse intre 7.6kW si 18.3 kW. Rezultatele experimentale obtinute au fost comparate cu date din literatura de specialitate si s-a constatat ca acestea sunt in concordanta cu valori obtinute de catre alti cercetatori. Scopul acestei lucrari este acela de a furniza o baza de date experimentale, care poate fi utilizata in activitatea de proiectare a racitoarelor de aer aripate, care functioneaza cu amoniac si sunt utilizate in aplicatii din domeniul alimentar, in vederea cresterii performantei termice a vaporizatoarelor si a coeficientului de performanta al instalatiei frigorifice. Implicit, acest studiu abordeaza problema permanent actuala a economiei de energie si a protectiei mediului inconjurator, prin aceea ca utilizeaza un agent frigorifc natural, si anume amoniacul (ODP=0 si GWP = 0), bine cunoscut pentru proprietatile sale termofizice superioare celor ale agentilor frigorifici de tip HFC.

This paper presents results of an experimental investigation conducted on an ammonia air-cooling evaporator working under conditions of frost formation in order to determine the effect of several key factors on the rate of frost formation and growth on finned coil surfaces, under different operating conditions. The influence of inlet air dry bulb temperature and air humidity ratio as well as evaporating temperature has been studied. Frost density, for different dry bulb temperature and humidity air ratio has also been studied. The experimental study was carried out on a specially designed set-up that allowed measuring, control and acquisition of data. Experiments were conducted for ammonia evaporation temperature of-18C and -10C and cooling capacity from 7.6 kW to 18.3 kW, during steady state operating conditions. Experimental results have been further compared to data in the open literature by authors with similar experimental investigations. The paper concluded that experimental results are in fairly good agreement with other authors work and consequently reliable. The objective of this work is to provide experimental data based on which improved design of ammonia finned evaporator coils used in food freezing or storage as air-coolers may be developed, thus leading to higher thermal performances of evaporators and higher coefficients of performance of the refrigerating system. Implicitly this experimental investigation addresses the permanent objective of energy savings. In addition, by using ammonia as a refrigerant, this experimental investigation addresses also current ecological issues linked to refrigerants. Ammonia is an environment friendly natural refrigerant, known for its zero ozone depleting potential (ODP)l and zero global warming effect (GWP), whose thermo-physical properties are attractive, as compared to HFCs.

The Pressure Losses for Two Phase Flow of Air Water in Horizontal Tubes
Alina Filip, Anica Ilie

The gas-liquid two-phase flow is characterized by continuous and local change of surface separation of phases and by their mutual interactions. Due to the instability of the flow, heat transfer and mass, a precise analytical approach is difficult to achieve. Despite these difficulties, efforts are underway to progress from the more frequent empirical studies to reliable analytical models. This requires an accurate research of the processes involved in the two phase flow and how they interact with one another. This paper aims to determine the pressure drop for a two-phase flow in a horizontal pipe of a heating plant. The author would like to to compare the results obtained by numerical simulation with existing results in the domain. The mixture is air-water, at an environmental temperature of 25˚C.

Masurarea poluarii aerului datorate traficului rutier din Bucuresti
Air pollution measurements due to urban traffic in Bucharest
Razvan Popescu, Andrei Damian, Lelia Popescu

In aceasta lucrare s-a urmarit masurarea poluarii exterioare din campusul Universitar al Facultatii de Inginerie a Instalatiilor Bucuresti. Unii dintre poluantii studiati prezinta valori de concentratii apropiate de limitele maxime admise de regelementările existente si pot cauza probleme de sanatate pentru studenti si profesori. Au fost realizate comparaţii ale valorilor masurate pentru o zi insorita si pentru o zi ploioasa, in vederea identificarii influentei parametrilor climatici. Masurarile sunt realizate cu un autolaborator de ultima generatie, datele fiind prelevate si stocate la un interval de 30 minute. Compusii masurati includ COV-uri, NOx, SO2, O3, CO si particule de praf.

In this paper the aim eas to measure the outdoor air pollution in the University Campus of the Faculty of Building Services. Some of the studied pollutants have values close to the maximum limits, that can cause health problems for the students and teachers. We compared the pollution levels in a rainy and sunny day to find out the influence of weather parameters. All the measurements were made with a new and modern autolaboratory, all the data being saved at 30 min interval. The measured compounds include VOCs, NOx, SO2, O3, CO and dust particles.

 
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