A thermodynamic apparatus that includes a displacer within a cylinder is disclosed. The displacer reciprocates within the cylinder by a linear actuator that includes electrical coils, an armature, and a coil spring system. The spring system includes collinear first and second coil springs of opposite sense. First ends of the springs are captured in a first plate; second ends of the springs are captured in a second plate. Without constraint, the springs can compensate to forces by bending, rotating, increasing in diameter, and combinations thereof. In certain applications, such as the heat pump, bending should be minimized. By selecting the points of capture of the hooks at the ends of the springs in the plates, bending force of the first spring counteracts the bending force of the second spring.

A tubular reactor which acts as a combustor and heat exchanger is disclosed. Such reactor supplants a system with a combustor having a heat exchanger arranged around the combustor. The combined system includes a diffuser having an inlet for a fuel-and-air mixture and a plurality of holes defined in its surface through which the fuel-and-air mixture exits the diffuser and a plurality of tubes. First linear portions along the length of each tube are mutually parallel with a centerline of the first portions of the tubes displaced from the diffuser by a predetermined distance. Centerlines of the linear portions of adjacent tubes are displaced from each other by a predetermined gap. The fuel and air combust in the proximity of the first portion of the tubes for effective heat transfer to gases traveling through the tubes. Such a tubular reactor can be employed within a thermal-compression heat pump.

A four-process cycle is disclosed for a Vuilleumier heat pump that has mechatronically-controlled displacers. Vuilleumier heat pumps that use a crank to drive the displacers have been previously developed. However, mechatronic controls provides a greater degree of freedom to control the displacers. The four-process cycle provides a higher coefficient of performance than prior cycles in the crank-driven Vuilleumier heat pump and those previously disclosed for a mechatronically-driven Vuilleumier heat pump. The four-process cycle can be drawn out to provide a low demand condition by causing both displacers to remain stationary for a period of time. The four processes in which one of the displacers is commanded to move are separated by periods of inactivity in which both displacers remain stationary.

A thermodynamic apparatus that includes a displacer within a cylinder is disclosed. The displacer reciprocates within the cylinder by a linear actuator that includes electrical coils, an armature, and a coil spring system. The spring system includes collinear first and second coil springs of opposite sense. First ends of the springs are captured in a first plate; second ends of the springs are captured in a second plate. Without constraint, the springs can compensate to forces by bending, rotating, increasing in diameter, and combinations thereof. In certain applications, such as the heat pump, bending should be minimized. By selecting the points of capture of the hooks at the ends of the springs in the plates, bending force of the first spring counteracts the bending force of the second spring.

A four-process cycle is disclosed for a Vuilleumier heat pump that has mechatronically-controlled displacers. Vuilleumier heat pumps that use a crank to drive the displacers have been previously developed. However, mechatronic controls provides a greater degree of freedom to control the displacers. The four-process cycle provides a higher coefficient of performance than prior cycles in the crank-driven Vuilleumier heat pump and those previously disclosed for a mechatronically-driven Vuilleumier heat pump. The four-process cycle can be drawn out to provide a low demand condition by causing both displacers to remain stationary for a period of time. The four processes in which one of the displacers is commanded to move are separated by periods of inactivity in which both displacers remain stationary.

A four-process cycle is disclosed for a Vuilleumier heat pump that has mechatronically-controlled displacers. Vuilleumier heat pumps that use a crank to drive the displacers have been previously developed. However, mechatronic controls provides a greater degree of freedom to control the displacers. The four-process cycle provides a higher coefficient of performance than prior cycles in the crank-driven Vuilleumier heat pump and those previously disclosed for a mechatronically-driven Vuilleumier heat pump.