An Experimental and Numerical Study of Precision Cooling to Determine Optimum Coolant Velocity of Downsized Internal Combustion Engines Using Boiling

Nowadays, due to the internal combustion engine (ICE) industry’s orientation toward downsizing, modern efficient cooling systems with lower power consumption, small size, and high compactness are essential. To improve these items, applying precision cooling and boiling phenomenon are inevitable. Having an appropriate coolant flow velocity that leads to utilize only the advantages of boiling heat transfer has always been a challenge. Two experimental test rigs, one for modeling and accurate prediction of subcooled flow boiling and the other for measurement and validation of coolant velocity in a water jacket by particle image velocimetry (PIV) method, are set up. An accurate and robust empirical correlation for modeling of subcooled flow boiling that occurs in the water jacket is developed. Then, through a three-dimensional (3D) thermal analysis, the heat transfer parameters such as heat flux and temperature distribution of the ICE cylinder block and head are obtained numerically. Finally, as the main achievement of this study, a diagram is presented, which combines the concept of precision cooling and subcooled flow boiling and gives the minimum coolant velocity in terms of heat flux. Without going into detailed thermo-fluid analysis, this provides a convenient tool to determine the minimum velocity of the coolant flow over the different regions of the ICE water jacket wall to keep it at its allowable temperature range.