Heat exchangers for vuilleumier cycle heat pumps

The invention relates to a heat pump device comprising a pair of chambers and a plurality of elements extending within both chambers. A working fluid is disposed in both of the chambers and a displacer means is positioned in each of the chambers such that they are movable within their respective chambers. Both of the displacer means have a wall that divides their respective chambers into two zones, a regenerator material that is housed therein, a plurality of elements extending outwardly from and in proximity to the elements extending within the respective chamber, and at least one passageway communicating through each displacer means and through the respective regenerator material for the working fluid to flow therethrough between the zones. There is a drive means for reciprocably moving both of the displacer means in their respective chamber between the respective zones of the chamber. There is also means for maintaining one of the zones of each of the chambers at a cool temperature and means for maintaining the other of the zones either at a relatively hot temperature or at a cold temperature.