Experimentally-theoretical analysis of cooling system of heavy vehicle engine

U ovom radu detaljno je opisan rashladni sustav na teškom vozilu koji provodi hlađenje: - rashladne kapljevine motora (voda u ovom slučaju), - ulja za podmazivanje motora i - ulja za podmazivanje transmisije. Rješenju problema pristupa se provođenjem mjerenja na deset radnih točaka motora. Izmjerene su vrijednosti protoka, te ulaznih i izlaznih temperatura svih fluida koji sudjeluju u izmjeni topline pri stacionarnim uvjetima rada vozila. Za matematički opis procesa prijenosa topline u rashladnom sustavu poslužili su izrazi W. M. Kaysa i A .M. Londona. Pomoću ovih izraza, a i nekih novijih opisa problema prijenosa topline u graničnom sloju, postavljen je matematički model za izračun koeficijenata prolaza topline na svakom fluidu u pojedinim radnim točkama motora. Izračunati koeficijenti prolaza topline, te izmjerene ulazne temperature i izmjereni protoci fluida na svakoj radnoj točki motora, ulazne su veličine za program temeljen na matematičkom modelu za križni izmjenjivač. Izračunom se dobivaju izlazne temperature fluida. Kontrola postavljenog matematičkog modela provedena je usporedbom izračunatih i izmjerenih izlaznih temperatura svih fluida. U ovom radu definiran je matematički model koji dovoljno dobro opisuje sustav hlađenja na predmetnom vozilu, što potvrđuje podudaranje izračunatih i izmjerenih vrijednosti. Verificirani matematički model koji opisuje rashladni sustav na ovom vozilu moguće je primjeniti i na ostalim vozilima čiji je rashladni sustav projektiran na istim principima.In this paper it is in details described cooling system in heavy vehicle, which cools: - engine cooling liquids (in this case - water), - engine lubricating oil and - transmission lubricating oil. Approach to problem solution is carried out by measuring in ten working points of the engine. Values of flows, inlet and outlet temperatures of all liquids participating in heat exchanging are measured at stationary vehicle working conditions. For mathematical describing heat transfer W. M. Kays and A .M. London expressions are used. By means of these expressions, as well as some newer descriptions of heat transfer in boundary layer problem it is set up mathematical model for calculating of heat transfer coefficients on each fluid at every single working point of the engine. Calculated heat transfer coefficients, measured inlet temperatures and measured fluid flows at every single working point of the engine are import values for a program based on mathematical model for cross exchanger. Outlet temperatures of fluids are calculated. Set-up mathematical model is controlled by comparison of calculated and measured outlet temperatures of all fluids. In this paper is defined mathematical model which properly enough describes cooling system of considered vehicle, proven in corresponding of calculated and measured values. This verified mathematical model which describes considered vehicle's cooling system is possible to apply on other vehicles with cooling system designed by similar principles