Cooling System Study and Simulation

Abstract

AbstractThe cooling system in an automobile maintains its engine and related components at an optimum range of temperature for proper functioning and life of the engine. The first step in designing a heat exchanger for an engine is estimating the heat released by the engine. Analytical methods to calculate the heat release of an engine are presented. A brief explanation of the functioning of the cooling system and the components involved is provided. The factors to be considered in the design of a cooling system are listed out. Computational Fluid Dynamics (CFD) provides a method of simulating heat transfer to predict the temperatures achieved in the engine and related components by incorporating all modes of heat transfer—conduction, convection, and radiation. The methodology and equations adopted in CFD software to model the physics of flow and heat transfer are explained. Simulation of convective heat transfer requires accurate prediction of the flow of the fluid. An important area in CFD contributing to this is turbulence modelling. Various turbulence models and the kind of flows for which they work well are presented. The boiling phenomenon is also expected in engine coolant flows and requires special models in CFD to simulate it. The important factors that affect flow with boiling are explained. Conjugate Heat Transfer (CHT) is the method for solving conduction in solid regions along with convection. The numerics behind these calculations are presented. Radiation models in CFD provide an effective way of predicting radiative heat transfer which is very important in components that reach very high temperatures. One of the most common CFD analyses carried out for the cooling system, particularly at the vehicle level, is the under-hood thermal analysis, which involves simulating airflow through the heat exchangers. When analyses are done at a vehicle level, it is not practicable to capture every flow phenomenon happening inside all the components of the cooling system. Instead, the effect of the component is modelled using experimental data. An explanation of such models is presented. Virtual simulation methods such as CFD provide a method to evaluate the performance of the cooling system before prototyping. The increased use of CFD in industrial problems has been made possible only due to parallel processing. The considerations and some of the solutions for parallel processing in CFD are explained. The increasing computing power also provides the opportunity for more analyses to be carried out. This allows improving the design for more optimal performance. Optimization methods are described in the last section.