Discretization and Heat Transfer Calculation of Engine Water Jackets in 1D-Simulation

The industry is working intensively on the precision of thermal management. By using complex thermal management strategies, it is possible to make engine heat distribution more accurate and dynamic, thereby increasing efficiency. Significant efforts are made to improve the cooling efficiency of the engine water jacket by using 3D CFD. As well, 1D simulation plays a significant role in the design and analysis of the cooling system, especially for considering transient behaviour of the engine. In this work, a practice-oriented universal method for creating a 1D water jacket model is presented. The focus is on the discretization strategy of 3D geometry and the calculation of heat transfer using Nusselt correlations. The basis and reference are 3D CFD simulations of the water jacket. Guidelines for the water jacket discretization are proposed. The heat transfer calculation in the 1D-templates is based on Nusselt-correlations (Nu = Nu(Re, Pr)), which are derived from 3D CFD simulations. Furthermore, additional modifications in the calculation routines and helpful criterions allow to handle the specific characteristics of the complex water jacket geometry user-friendly. The 1D results are compared in detail with the 3D CFD reference and show very good agreement for various operating points regarding inlet mass flow rate and inlet temperature. The methodology is developed using a passenger car engine (Test Engine I) and validated on a large engine (Test Engine II). Whereas the passenger car engine has a water jacket with the cylinders in cross flow, the large engine has single cylinder cooling with flow along the cylinder axis. The analysis of two engines with different water jacket flow characteristic shows the general validity of the developed methodology.