CFD study of thermal managemant of the Ford Otosan truck underhood

Vođenje sustava hlađenja motora jedna je od ključnih zadaća prilikom konstruiranja novih teških vozila. Rezultati provođenja termalne analize koriste se za analizu opterećenja, tj. termalna analiza jedan je od prvih koraka u integriranom procesu dimenzioniranja toplinski opterećenih dijelova. Time naglašava svoju važnost u dizajniranju prototipa. Geometrija motora vrlo je kompleksa za računalnu analizu te zahtjeva inženjersku procjenu o izostavljanju nepotrebnih dijelova kako bi smanjili vrijeme i resurse računanja. Kroz napredne algoritme kreiranja mreže proces simulacije je donekle automatiziran, ali još uvijek zahtjeva najviše vremena. S obzirom na prirodu geometrije kompaktnih izmjenjivača topline koji zahtijevaju milijune elemenata, potrebni su precizni modeli koji bi zamijenili ovu potrebu. U industriji, svaki je izmjenjivač topline ispitan. Ovo znanje se može iskoristiti za modeliranje pada tlaka i toplinske efektivnosti kako bi dobili točan model za simulaciju. U svrhu simuliranja kamionskog kompaktnog izmjenjivača topline s mikro kanalima s jednim prolazom, razvijen je novi model izmjenjivača topline u softverskom paketu foam-extend. Model je uspješno provjeren putem testiranja pojedinačnog izmjenjivača topline kamiona, kao i putem njihovog zajedničkog rada. Ventilator je modeliran kao zona rotacije (engl. Multiple Rotating Frame), dok su izmjenjivači topline modelirani kao porozne zone preko Darcyjevog zakona. Priprema geometrije i mreže odrađena je u ANSA-i. Simulacije su se odradile kroz dva koraka: prvo je simuliran hladni tok, dok je nakon toga simulirana energetska jednadžba kroz dobiveno polje strujanja. Obje simulacije su pokazale stabilnu konvergenciju. Rezultati su prezentirani u zadnjem poglavlju u obliku slika i predane topline pojedinog izmjenjivača topline. U radu se toplinska efektivnost pretpostavila konstantnom. Eksperimentalnim testiranjem ova pretpostavka se može dodatno modelirati s implementiranjem ovisnosti o broju jedinica prijenosa (engl. Number of Transfer Units).Underhood thermal management is a crucial task in the design of new heavy-duty vehicles. Results of performing thermal analysis are used for stress analysis, i.e. it is one of the first steps in an integrated process of dimensioning parts related to thermal conditions. This only emphasises its importance in prototype design. In the CFD simulation, geometry of the underhood parts is rather complex and there is a need for engineer’s decision on removing redundant parts to reduce computational time and resource. Advanced meshing algorithms help in this process, but it still requires the largest amount of time. Due to the compact heat exchanger’s geometry, that requires millions of cells, there is a need for accurate models that represent this feature. In industry, every heat exchanger is experimentally tested. This can be used to model pressure drop and heat effectiveness, ultimately gaining an accurate model for CFD simulations. A new heat exchanger model was developed in foam-extend for purpose of simulating automotive compact micro-channel heat exchanger with one pass. This model was successfully validated through testing on each individual exchanger from a truck’s geometry, and their simultaneous work has been analysed. Truck’s fan was modelled as the Multiple Rotating Frame (MRF) zone, while the heat exchangers were modelled as porous zones with Darcy’s law. Pre-processing of the truck’s geometry was performed in ANSA. Simulations were done in two steps: First, the cold flow simulation was performed, after which the temperature field was solved separately including both streams. Both simulations showed stable convergence. Results are presented in the last chapter in the form of figures and total heat rejection of each heat exchanger for one operational condition. Lastly, in this study the heat exchanger's effectiveness was assumed to be constant, with experimental data this approach can be broader in terms of implementing effectiveness dependency on Number of Transfer Units (NTU)