Dan CONSTANTINESCU
TERMOTEHNICA IN CONSTRUCTII

Fundamentare teoretica si aplicatii

 Volumul 1
 

        Lucrarea a fost conceputa sub forma a doua parti, complementare in economia scopului urmarit, care trateaza atat procesele de transfer de caldura si masa la nivelul elementelor componente ale cladirii, cat si rezultanta acestor procese la nivelul intregii cladiri definita sub forma unui contur termodinamic de tip multizonal. Spre deosebire de lucrarile anterioare care abordeaza punctual problematica dimensionarii higrotermice a elementelor de constructie, cea de fata se adreseaza in special scopului de determinare a performantei energetice a cladirilor, fie in stadiul de proiect, fie existente, pe baza careia se pot concepe solutii de modernizare ale caror caracteristici pot da un plus de valoare cladirilor studiate. Practic se prezinta bazele unei noi discipline, numita de autor "proiectarea energetica a cladirilor".

        Raspunsul termic al elementelor de inchidere si al cladirii in ansamblul sau la solicitarile termice obiective si subiective datorate mediului exterior natural, pe de o parte, si comportamentului celor care ocupa cladirea, pe de alta parte, reprezinta caracteristica proceselor analizate. Principalul instrument de lucru dezvoltat in lucrare este regimul nestationar de transfer de caldura si masa. Regimul stationar de transfer de caldura este exploatat in contextul unor echivalente fenomenologice cu regimul nestationar, fapt care permite utilizarea tuturor avantajelor modelarii in regim stationar, fara a se pierde ceva din specificitatea modelelor in regim nestationar. Utilizarea parametrului "temperatura exterioara virtuala", propus de autor, faciliteaza simbioza functionala a celor doua clase de modelare a proceselor mentionate. Se au in vedere si procesele specifice unitatilor de stocaj termic de tip sensibil in roci si unitatilor de stocaj termic in substante cu schimbare de faza de speta a doua, de tipul solid-lichid. Aceste unitati de stocaj fac parte din dotarea cladirilor moderne de tip pasiv alaturi de sisteme de tip spatiu solar cu circulatie controlata a aerului si sisteme de racire naturala prin efect combinat convectiv-radiativ catre bolta cereasca a apei, care sunt, de asemenea, analizate in lucrare.

        Prima parte a lucrarii abordeaza procesele fundamentale de transfer de proprietate (caldura si masa) intr-o descriere fenomenologica concretizata intr-un limbaj matematic "clasic", accesibil celor cu pregatire superioara corespunzatoare, dar si celor "dotati" cu curiozitatea necesara oricarei investigatii.

        A doua parte a lucrarii abordeaza probleme concrete de transfer de caldura si masa din cladiri ocupate, dar si proprii instalatiilor termice a caror menire este sa asigure confortul termic din spatiile ocupate. Se insista asupra conceptului de performanta in realizarea parametrilor de stare din spatiile ocupate si se ofera algoritmi de cuantificare a calitatii furnizarii caldurii / frigului. O preocupare aparte, premiera in literatura autohtona de specialitate, este cea de identificare a caracteristicilor termice reale ale anvelopei cladirilor existente, cu referire atat la elementele de constructie transparente, cat si la cele opace. Modelele de calcul dezvoltate se inscriu in categoria modelarii inverse si trateaza o mare diversitate de cazuri pornind de la elemente amplasate in zona de camp a anvelopelor opace, pana la ansamblul cladire-instalatii termice din dotarea cladirii.

Dan CONSTANTINESCU
HEAT ENGINEERING IN CONSTRUCTION

Fundamentals and applications

Volume 1 - Fundamentals
 

        This book was conceived in two parts, complementary in terms of the target pursued, dealing with the heat and mass transfer processes at the level of the building members, as well as with the resultant of these processes at the level of the entire building defined as a thermodynamic layout of the multizone type. Unlike the previous studies which deal in a punctual manner with the building members hygrothermal dimensioning, this one is mainly focused on assessing the buildings energy performance, either in the design phase, or existing, based on which upgrading solutions may be envisaged; the characteristics of these solutions may add to the value of the buildings subjected to study. Actually they represent the fundamentals of a new branch called by the author "buildings energy - related design".

        The thermal response of the closing members and of the building as a whole to the objective and subjective thermal loads generated by the natural outdoor environment, on one hand and by the occupants’ behaviour on the other, represents the characteristic of the analyzed processes. The main working instrument developed in the study is represented by the heat and mass transfer unsteady-state conditions. The heat transfer state-state conditions are used in the context of certain phenomenological equivalences with the unsteady-state conditions, which allows the use of all the advantages of the modelling in steady-state conditions, without missing anything in terms of the unsteady-state models specificity. The use of the parameter called "virtual outdoor temperature", proposed by the author, facilitates the functional symbiosis of the two classes of modelling the previously mentioned processes. The processes specific to the units of sensitive thermal storage in rock beds and those specific to the thermal storage units in phase change substances of the second type, of the solid-liquid type are also taken into account. These storage units are part of the equipment of the passive modern buildings, together with systems like solar spaces with controlled air flow and water natural cooling systems based on the convective-radiative to the sky combined effect, which are also examined in the work.

        The first part of the book approaches the property transfer fundamental processes (related to heat and mass) in a phenomenological description concretized in a "classical" mathematical language, accessible to persons with proper expert background as well as to those who have the curiosity necessary in this field of investigation.

          The second part of the book approaches concrete issues related to the heat and mass transfer in occupied buildings, but also specific to the thermal systems meant to provide thermal comfort in the occupied spaces. The work insists on the concept of performance in achieving the state parameters in the occupied spaces; the algorithms of quantifying the quality of heat/cold supply are also provided. A special concern, presented for the first time in the specialized literature in Romania, is the identification of the real thermal characteristics of the existing buildings envelope, referring both to the transparent and opaque building members. The calculation models developed are of the inverse modelling type and approach a large range of cases starting from members located in the opaque envelopes field area, up to the building - thermal systems in the building complex.