Experimental Investigation of Two-Phase Heat Transfer in a Simulated Cooling Duct of a Piston Engine Cylinder Head

Abstract

Liquid cooling of cylinder and piston parts in highly boosted internal combustion engines is generally accompanied by local phase transition phenomena, such as surface nucleate boiling. The heat transfer coefficient of nucleate boiling is several times higher than that of single-phase convection. In order to efficiently exploit the thermal effect of nucleate boiling in cooling systems, simultaneously preventing emergency supercritical modes, a deeper understanding of boiling physics based on full-scale experiments is required. We conducted experimental investigation of heat transfer in a simulated cooling duct of a piston engine cylinder head, using a bespoke motor-free installation. We studied the effects of velocity, flow character and coolant type on the heat transfer, accounting for the presence of congestion regions. Over the course of the experiment, we simulated thermal conditions characteristic of different heat transfer types: single-phase convection, nucleate boiling, the onset of boiling crisis. We used the experimental data to plot the coolant heat flow density as a function of wall temperature for different measuring points situated inside the stream and the turbulent flow regions (congestion regions). We show that the mature nucleate boiling mode is the most favourable in terms of how uniform the temperature field within a part is. The experimental data obtained during the investigation may be used to verify mathematical simulations in the two-phase heat transfer theory, provided the data have been appropriately processed