Forced convective heat transfer of parallel-mode reciprocating tube fittedwith a twisted tape with application to piston cooling

This experimental study, motivated by the need to improve the cooling perfo rmance of a piston in a marine propulsive diesel engine, investigated turbu lent flow heat transfer in a reciprocating tube fitted,vith a twisted-tape insert. The nonreciprocating experimental darn, obtained from the tube fitt ed 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 p rovide considerable heat transfer modifications from nonreciprocating situa tion. When the reciprocating forces were relatively weak, a range of heat-t ransfer impediments, that could reduce local Nusselt numbers to levels of a bout 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 relati ve to the nonreciprocating situation. For design considerations, heat-trans fer enhancement due to the twisted-tape insert was confirmed but the impedi ments from non-reciprocating levels at lower values of pulsating numbers ne eds particular attention in order to avoid overheating situations.