Forced Convective Heat Transfer of Parallel-Mode Reciprocating Tube Fitted With a Twisted Tape With Application to Piston Cooling

This experimental study, motivated by the need to improve the cooling performance of a piston in a marine propulsive diesel engine, investigated turbulent flow heat transfer in a reciprocating tube fitted with a twisted-tape insert. The nonreciprocating experimental data, obtained from the tube fitted with twisted tape, confirmed that heat-transfer augmentation from plain-tube level occurs. When the test tube reciprocated, buoyancy effects became appreciable, and interacted with the reciprocating and inertial forces to provide considerable heat transfer modifications from nonreciprocating situation. When the reciprocating forces were relatively weak, a range of heat-transfer impediments, that could reduce local Nusselt numbers to levels of about 53% of nonreciprocating values, was observed. A further increase of the relative strength of the reciprocating force resulted in a subsequent heat-transfer recovery, and eventually led to heat-transfer enhancements relative to the nonreciprocating situation. For design considerations, heat-transfer enhancement due to the twisted-tape insert was confirmed, but the impediments from nonreciprocating levels at lower values of pulsating numbers needs particular attention in order to avoid overheating situations.