The reciprocating heat-transfer device or reciprocating heat pipe has a high effective thermal conductance, and applications can be found in various reciprocating mechanisms, including offset cam mechanisms, Scotch yoke mechanisms, and piston assemblies of internal combustion engines. The liquid return mechanism presents the most important operating limitation for this type of heal-transfer device. In this paper, the potential applications of the reciprocating heat-transfer device to Various reciprocating mechanisms are described. Theoretical analyses are performed for the critical working frequency of the device in connection with the reciprocating mechanisms. An analytical solution and semi-empirical correlation, with and without taking into account the how resistance, are obtained. Extensive experiments for the critical working frequency are then undertaken on an engine tester. Comparison:of the analytical and experimental results indicates that the analytical solutions and semi-empirical correlation provide an accurate prediction for the working limits of reciprocating heat-transfer devices. (C) 1997 Elsevier Science Ltd.