The thesis work was carried out as an internship at the company MITA Cooling Technologies (Siziano, Pavia). The internship took place in the research and development area of the company, supporting a new product development project, focused on the technical and strategic analysis of cross-flow evaporation towers. In particular, after modeling the phenomena of heat exchange and material occurring inside the exchange pack, a software was developed with the aim of performing a performance comparison between towers in crossflow configuration and counter flow towers. By adopting the simplifying hypotheses introduced by Merkel, mass and energy balances were carried out within the package. We have arrived at a nonlinear two-dimensional model of two partial differential equations in the unknowns water temperature and enthalpy of the air. To solve the model, the finite difference method according to Crank-Nicolson was adopted and an algorithm was identified that is able to calculate the water temperature and enthalpy values of the air inside the package. This algorithm, together with the one used to resolve the Merkel integral, was implemented in FORTRAN 77 language. With the software obtained, comparisons were made between the crossflow and counterflow configurations, first with the same package volume, then in conditions. criticisms of the crossflow package, finally with the same power. With the results obtained, machine operation maps were drawn.
Il lavoro di tesi si è svolto come tirocinio presso l'azienda MITA Cooling Technologies (Siziano, Pavia). Il tirocinio si è svolto nell'area di ricerca e sviluppo dell'azienda, a supporto di un progetto di sviluppo nuovo prodotto, incentrato sull'analisi tecnica e strategica di torri evaporative a flussi incrociati. In particolare, dopo aver modellato i fenomeni di scambio termico e di materia che avvengono all'interno del pacco di scambio, si è sviluppato un software con lo scopo di effettuare un confronto prestazionale fra torri in configurazione crossflow e torri in counter flow. Adottando le ipotesi semplificative introdotte da Merkel, sono stati effettuati i bilanci di massa e di energia all'interno del pacco. Si è giunti ad un modello bidimensionale non lineare di due equazioni alle derivate parziali nelle incognite temperatura dell'acqua e entalpia dell'aria. Per risolvere il modello si è adottato il metodo alle differenze finite secondo Crank-Nicolson ed è stato individuato un algoritmo in grado di calcolare i valori di temperatura dell'acqua e di entalpia dell'aria all'interno del pacco. Tale algoritmo, insieme a quello utilizzato per risolvere l'integrale di Merkel, è stato implementato in linguaggio FORTRAN 77. Con il software ottenuto si sono effettuati dei confronti fra le configurazioni crossflow e counterflow, prima a parità di volume di pacco, poi in condizioni critiche del pacco crossflow, infine a parità di potenza. Con i risultati ottenuti sono state tracciare delle mappe di funzionamento delle macchine.
Simulazione e confronto di torri evaporative a flussi incrociati e controcorrente
FRAGOLA, ANDREA
2018/2019
Abstract
The thesis work was carried out as an internship at the company MITA Cooling Technologies (Siziano, Pavia). The internship took place in the research and development area of the company, supporting a new product development project, focused on the technical and strategic analysis of cross-flow evaporation towers. In particular, after modeling the phenomena of heat exchange and material occurring inside the exchange pack, a software was developed with the aim of performing a performance comparison between towers in crossflow configuration and counter flow towers. By adopting the simplifying hypotheses introduced by Merkel, mass and energy balances were carried out within the package. We have arrived at a nonlinear two-dimensional model of two partial differential equations in the unknowns water temperature and enthalpy of the air. To solve the model, the finite difference method according to Crank-Nicolson was adopted and an algorithm was identified that is able to calculate the water temperature and enthalpy values of the air inside the package. This algorithm, together with the one used to resolve the Merkel integral, was implemented in FORTRAN 77 language. With the software obtained, comparisons were made between the crossflow and counterflow configurations, first with the same package volume, then in conditions. criticisms of the crossflow package, finally with the same power. With the results obtained, machine operation maps were drawn.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/149602