The traditional oil cooler with smooth tube has low heat transfer coefficient and dead zone in shell side flow

and it easily produces dirt. The trefoil screwed expansion pipe is used to enhance the heat transfer of the traditional oil cooler. The heat transfer and pressure drop of the oil cooler with trefoil screwed expansion tube were tested in an experimental system and compared with oil cooler with smooth tube and oil cooler with outer finned tube respectively. The result shows that the oil cooler with trefoil screwed expansion tube improves heat transfer coefficient more significantly compared with oil cooler with outer finned tube

but is accompanied by a higher pressure drop. With Reynolds number increasing

the comprehensive performance of oil cooler with trefoil screwed expansion tube is better gradually than the oil cooler with outer finned tube

which means that oil cooler with trefoil screwed expansion tube has good application prospect.