INFLUENCE OF RECIPROCATING MOTION ON HEAT-TRANSFER INSIDE A RIBBED DUCT WITH APPLICATION TO PISTON COOLING IN MARINE DIESEL-ENGINES

This paper presents the results of an experimental study aimed at inve stigating the effect of reciprocating motion on the heat transfer for the flow inside a square ribbed enclosure. This flow configuration was a modification of the modern cooling system within a reciprocating pi ston of a marine heavy diesel engine. Initially, the heat transfer cha racteristics for the ribbed duct flow were examined and validated by c omparing the present data with the relevant publications. Significant heat transfer enhancements detected from the nonreciprocating forced c onvection tests suggested the potential for heat transfer improvement using ribbed coolant channel, For the shaking effect on the cooling pe rformance of the ribbed enclosure, a heat transfer impediment near whi ch the thermal boundary layers were initiated was found when the recip rocating force was relatively low. Further increase of the reciprocati ng force or the level of heating power enhanced heat transfer. At the highest reciprocating speed tested, the heat transfer could be increas ed to a level about 145% of the equivalent stationary case. This study clarified that the circular ribs could be added inside the cooling pa ssages in order to improve the cooling performance of the piston.