Abstract: Vuilleumier type heat pumps and other thermal regenerative devices of the same type are improved by the provision of agitation and circulation of the working fluid within the working spaces for greater efficiency of heat exchange to/from these spaces. The circulation may be by means of fans, with electric motors, jet circulators, controlled direct exit of the working fluid from displacers, rotor blades located on a shaft operated from outside the device and other suitable means. The device may be single- or multi-unit. It may provide power to drive itself and/or for other uses.