COMPARISON BETWEEN THERMAL MACHINES AND FUEL CELL TREATMENT IN THE FRAMEWORK OF THERMODYNAMICS WITH FINITE SPEED

Autor/autori: Stoian PETRESCU, Monica COSTEA, Vlad MARIS

Rezumat: Lucrarea prezinta momentele importante din Dezvoltarea Termodinamicii cu Viteza Finita (TVF), esenta acesteia, noii parametri (parametrii de stare instantanei si medii) introdusi pentru descrierea proceselor cu viteza finita, principalele formule si instrumente de calcul introduse si folosite in TVF, metoda principala de Optimizare a vitezei, temperaturii si a altor parametrii ai ciclurilor ireversibile, numita Metoda Directa - cu realizarile obtinute pana la Validare. Exprimarea matematica a Primului Principiu al Termodinamicii pentru Procese cu Viteza Finita combinat cu cel de al doilea Principiu este esenta TVF. Avantajul ei (in comparatie cu alte ramuri ale Termodinamicii Ireversibile - TI) consta in capacitatea de a obtine performantele oricarui ciclu cu viteza finita (Randamentul / COP si Puterea Produsa / Consumata) deoarece ia in considerare chiar din sart,ambele tipuri de pierderi: interne si externe. Cum poate ajuta aceasta noua ramura a TI in Proiectarea Optimizata a Masinilor Termice, relatiile TVF cu alte ramuri ale TI, precum si tendintele de unificare intre diversele ramuri ale Termodinamicii Ireversibile sunt prezentate in partea a doua a lucrarii. Este prezentata analogia dintre tratarea cantitativa a proceselor ireversibile in Masinile Termice (MT) si Dispozitivele Electrochimice (DE: pile de combustie, eletrolizoare si baterii). Aceasta analogie se bazeaza pe expresia Primului Principiu al Termodinamicii pentru Procese cu Viteza Finita combinat cu cel de al doilea Principiu, tratata in acelasi format in ambele domenii (MT si DE). Din punct de vedere metodologic, aceasta tratare constituie punctul de plecare al abordarii unitare a Termodinamicii cu Viteza Finita (TVF) in cele doua domenii, Termodinamica Inginereasca si Eletrochimia, care, istoric, s-au dezvoltat independent. Aceasta analogie si tratarea cantitativa similara arata, de fapt, ca toate ireversibilitatile (fie din MT, fie din DE) sunt generate de Viteza Finita de desfasurare a proceselor implicate.

Cuvinte cheie: termodinamica cu viteza finita, ireversibilitati interne si externe, primul principiu combinat cu principiul al doilea pentru procese cu viteza finita, cicluri ireversibile cu viteza finita, Metoda Directa, procese ireversibile in pile de combustie, performante

Abstract: The main Moments in the Historical Development of Thermodynamics with Finite Speed (TFS), the Essence of it, the New Parameters (Instantaneously average parameters of state) introduced for description of Finite Speed Processes, The main Formulas and Tools introduced and used in TFS, the main Method for Optimization of the Speed, Temperature and other parameters of irreversible cycles, called The Direct Method - with their Achievements and Validation are presented. The Essence of TFS is the combination of the First Law of Thermodynamics for Processes with Finite Speed with the Second Law of Thermodynamics. The Advantage of it (in comparison with the other branches of Irreversible Thermodynamics - IT) consists in the ability to obtain the performances of any cycle with Finite Speed (Efficiency/ COP and Power) by taking into account from the start, both internal and external irreversibilities. How this new branch of IT could help improve the Design of Thermal Machines and Relations with the other branches of Irreversible Thermodynamics and the Tendency of Unification, are presented in the second part of the paper. The analogy between the quantitative treatment of irreversible processes in Thermal Machines (TM) and those in Electrochemical Devices (ED: Fuel Cells, Electrolysers and Batteries) is discussed. This analogy is based on expressing the First Law of Thermodynamics for irreversible processes with Finite Speed, combined with the Second Law, in a similar format in both fields (TM and ED). From a methodological point of view, this treatment becomes the starting point for a unitary approach of Thermodynamics with Finite Speed (TFS) in the two domains historical independently developed: Engineering Thermodynamics and Electrochemistry. This analogy and the similar quantitatively treatment shows in fact, that all irreversibilities (either in TM or in ED) are generated by their Finite Speed.

Keywords: thermodynamics with finite speed, internal and external irrevesibilities, First Law for processes with finite speed combined with the Second Law, irreversible cycles with finite speed, the direct method, irreversible processes in fuel cells, irreversible performances

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