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Teza Doctorat Cristiana CROITORU

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    UNIVERSITATEA TEHNIC DE CONSTRUCII

    BUCURETI Facultatea de Inginerie a Instalaiilor

    Catedra de Instalaii Hidraulice,Termice i Protecia Atmosferei

    TEZ DE DOCTORAT STUDII TEORETICE I EXPERIMENTALE REFERITOARE

    LA INFLUENA TURBULENEI AERULUI DIN NCPERILE CLIMATIZATE ASUPRA CONFORTULUI

    TERMIC

    Doctorand Ing. Cristiana Verona Popescu (cstorit Croitoru)

    Conductor tiinific Prof. univ. dr. ing. Iolanda Colda

    BUCURETI 2011

    Universitatea Tehnic de Construcii Bucureti

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    Titularul prezentei teze de doctorat a beneficiat pe ntreaga perioad a stagiului de pregtire doctoral de burs atribuit prin proiectul Burse doctorale pentru ingineria mediului construit, cod POSDRU/59/1.5/S/2, beneficiar UTCB, proiect derulat n cadrul Programului Operaional Sectorial Dezvoltarea Resurselor Umane, finanat din Fondurile Structurale Europene, din Bugetul Naional i cofinanat de ctre UTCB.

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    Motto: The cure for boredom is curiosity. There is no cure for curiosity!, Ellen Parr

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    Rezumat

    n contextul economic mondial actual, eficiena energetic n toate aspectele sale trebuie s fie parte a contiinei noastre. Astfel, orientarea ctre noi strategii ce conduc la economie de energie n general, dezvoltarea de noi metode de evaluare a parametrilor sistemelor sau elementelor ce le compun sau actualizarea celor existente a devenit o necesitate absolut. Scopul principal al acestei teze de doctorat este analiza influenei turbulenei aerului asupra confortului termic. Acest parametru este prea puin luat n considerare n evaluarea confortului termic cu ajutorul diverselor modele i indici de confort termic, preconizai de standarde i normative internaionale unele dintre nefiind actualizate de mai mult de dou decade. n prima parte a tezei, trecem n revist principalele concepte utilizate ulterior n capitolele de rezultate. Capitolul bibliografic reprezint sinteza reperelor din literatura de specialitate ce ne-au permis s ne orientm ctre un anumit tip de studiu numeric i s alegem o anumit validare experimental, n funcie de rezultatele existente i de mijloacele puse la dispoziie.

    Am prezentat n continuare configuraia dispozitivului experimental ce include celula experimental, manechinul termic i sistemul de msurare. Cea mai important parte din cadrul acestei campanii experimentale este conceperea unui manechin termic, care poate simula i cuantifica comportamentul organismului uman din punct de vedere termic. Prototipul Thermal Boy 1 are ase circuite electrice distincte pentru fiecare parte a corpului, care reproduc temperaturile locale fiziologice ale regiunilor corpului uman.

    n ceea ce privete partea numeric din cadrul acestei teze, am pornit prin a construi un model geometric ce reproduce fidel celula experimental i manechinul termic. Odat ce a fost aleas i validat discretizarea final a domeniului de calcul, am validat modelul de turbulen ales iniial - k- SST - prin compararea cmpurilor mrimilor specifice ale aerului (vitez i temperatur) cu rezultatele obinute pentru apte modele de turbulen i datele de referin din msurri PIV i termografie IR. n ultimul capitol este propus un studiu numeric aprofundat al influenei intensitii turbulenei aerului asupra strii de confort termic percepute ce reprezint principala contribuie original n ceea ce privete abordarea numeric. Patru strategii de ventilare (amestec cu refulare n partea superioar, i n partea inferioar, deplasare i piston) sunt analizate din punctul de vedere al indicilor clasici de confort termic sau a unor corelaii ntre gradul de turbulen local i fluxul de cldur cedat prin convecie de ctre corpul uman. Pentru fiecare caz, se observ o intensificare a transferului de cldur prin convecie, exprimat printr-o cretere medie de 14% a fluxului de cldur convectiv, remarcnd chiar o cretere maxim de aproape 18% pentru strategia de ventilare prin amestec cu refulare n partea inferioar a ncperii studiate.

    Variind doar intensitatea turbulenei aerului impuse la nivelul dispozitivului de introducere a aerului am obinut diferene semnificative privind transferul de cldur prin convecie la nivelul corpului, i indirect o schimbare a strii de confort termic. n concluzie, putem spune c analiza distribuiilor fluxului convectiv pe suprafaa manechinului termic relev importana unui studiu detaliat al dinamicii curgerilor convective n jurul corpului uman n cadrul analizei confortului termic. Aceast constatare este ntrit de existena unor corelaii puternice ntre fluxul convectiv local i intensitatea turbulent local.

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    Abstract

    Looking through the current global economic context, energy efficiency in all its aspects should be part of our consciousness. Thus, the orientation towards new strategies that lead to energy savings in general, development of new methods for evaluating the system parameters or elements or upgrading existing ones become an absolute necessity. The main objective of this PhD thesis is to analyze the influence of air turbulence on thermal comfort. This parameter is rarely taken into account in assessing thermal comfort using different models and thermal comfort indices, international standards, some of them still remaining unchanged for more than two decades. In the first part of the thesis, we review the main concepts used in results chapters. Bibliographic chapter is the synthesis of the concepts in the literature that allowed us to get directions to a particular type of numerical study and to choose a specific experimental validation, according to existing results and available resources.

    In the next part, we presented the experimental device configuration that includes experimental cell, thermal manikin and measuring system. The most important part of this experimental campaign is designing a thermal manikin that can simulate and quantify human behavior in terms of heat transfer. The prototype Thermal Boy 1 has six separate electrical circuits for each body part that reproduce physiological local temperatures of the human body's regions.

    Regarding the numerical part of this thesis, we started by building a geometric model that reproduces the experimental cell and thermal manikin. Once the final mesh was chosen and validated for the numeric domain, we validated the turbulence model initially chosen - k- SST - by comparing specific fields of air velocity and temperature with the results obtained from seven turbulence models and reference data of PIV measurements and IR thermography. In the last chapter we proposed a numerical study of the influence of air turbulence intensity on the perceived thermal comfort being the main original contribution in terms of numerical approach. Four ventilation strategies (mixing ventilation with inlet at the upper and lower part of the room, displacement and piston) are analyzed in terms of the classic thermal comfort indexes or correlations between the degree of local turbulence intensity and convection heat flux released by the human body. For each case, we find an intensification of convective heat transfer expressed as an average increase of 14% of convective heat flux, even a maximum increase of almost 18% for mixing ventilation strategy with the inlet at the lower part of the studied the room.

    Varying only the air turbulence intensity, imposed at the inlet device we obtained significant differences on the convection heat transfer of by the body, and indirectly a change in state of thermal comfort. In conclusion, we can say that the analysis of convective heat flux distributions on the surface of the thermal manikin reveals the importance of a detailed study of the dynamics of convective flows around the body in the study of thermal comfort. This finding is reinforced by the existence of strong correlation between local convective flux and local turbulent intensity.

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    Rsum

    Dans le contexte conomique actuel, lefficacit nergtique dans tous ses aspects doit rentrer dans notre conscience. Lorientation vers des nouvelles stratgies conduisant en gnral une conomie dnergie, le dveloppement des nouvelles mthodes dvaluation des paramtres des systmes ou de leurs lments composants, ou lactualisation des mthodes existantes, se sont imposs comme une ncessit. Lobjectif principal de cette thse a t danalyser linfluence de la turbulence sur le confort thermique. Ce paramtre est aujourdhui trop peu pris en considration par les modles existants utiliss pour lvaluation du confort thermique prconiss par des rglementations et standards dont certains restent inchangs depuis plus dune dcennie.

    Dans la premire parte de la thse, nous passons en revue les principaux concepts que nous avons utilis et analyss ultrieurement dans les chapitres dtudes exprimental et numrique. Ltude bibliographique propos reprsente la synthse des principaux repres dans la littrature de spcialit qui nous ont permis de nous orienter vers un certain type dtude numrique et choisir la validation exprimentale, en fonctions des rsultats des prcdents tudes et des moyens que nous avons eu disposition.

    Nous avons prsent par la suite, la configuration du dispositif exprimental, incluant la cellule test, le mannequin thermique et le systme de mesure. La plus importante partie de cette campagne exprimentale est reprsente par la conception dun mannequin thermique qui peut simuler et quantifier le comportement de la surface du corps humain du point de vue thermique. Le prototype, appel Thermal Boy 1, a six circuits lectriques distinctes qui chauffent six rgions du corps pour reproduire leurs tempratures physiologiques.

    En ce qui concerne la partie numrique de cette thse, nous avons commenc par

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