The technological background of the reciprocating heat pipe (or shaking-up heat pipe) is described. Four reciprocating heat pipes with different geometrical dimensions are tested for the determination of the minimum reciprocal frequency of the heat pipe. The experimental results show that the minimum frequency is lower for a reciprocating heat pipe with a shorter length and larger diameter. Overall, the minimum frequency is essentially insensitive to the variation of heat pipe dimensions and power inputs. This means that the reciprocating heat pipe can be used for piston cooling without encountering any major working limitations. The experimental results also show that at a higher engine cranking speed, the effective thermal conductance of the reciprocating heat pipe is more than 130 times that of a copper bar having the same size as the heat pipe. This would rank the reciprocating heat as one of the best performers in various heat pipe applications, considering the small length of the reciprocating heat pipe. Finally, a reciprocating heat pipe without air evacuation is tested, which indicates that the contribution of the liquid impingement in the heat pipe is significant, and that this heat pipe works relatively well at a lower heat input.
