Theoretical Analysis of Internal Combustion Engine Miscellaneous Heat Losses

With more stringent emissions regulations (e.g., US EPA 2010), heat rejection control in cooling system design becomes increasingly important and a necessary part of the emissions control recipe in modern diesel engine design. Energy balance of the gas-side performance data (flow rate and temperature) with thermodynamic first law is an effective approach to analyze coolant heat rejection. In order to determine a critical engine design characteristic, base engine heat rejection percentage, an accurate assessment on various miscellaneous heat losses is required. Once the miscellaneous heat losses are known, it is convenient to use the gas-side energy balance to compute base engine coolant heat rejection. In this paper, a theoretical analysis was conducted to derive the parametric dependency of the miscellaneous losses to the ambient through the surfaces of exhaust manifold, turbocharger and engine block via convection and radiation heat transfer. Two energy balance analysis methods with different boundaries are presented to support the analysis of miscellaneous heat losses. The results were validated by coolant heat rejection experimental data. GT-POWER simulation results are also included.