Abstract: 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.

Abstract: A heat pump is disclosed that has a hot displacer section and a cold displacer section with a linear actuator section disposed between the hot and cold displacer sections. By providing the linear actuator section between the displacers, the shafts that couple the actuators in the linear actuator section to their respective displacer is shorter than if the linear actuator section were located at the bottom of the cold displacer. The shorter shaft can be less stiff to avoid buckling. Due to a lesser propensity to cock, there is less friction of the shaft when reciprocating.

Abstract: 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.

Abstract: A linear actuator is disclosed that is a double-ended solenoid with springs to provide much of the force for movement. The linear actuator can be used in a thermodynamic apparatus, such as a Vuilleumier heat pump in which two linear actuators are provided to drive two displacers. The linear actuator also has a cylindrical back iron section having first and second recesses with coils disposed in the recesses. The linear actuator assists in moving the armature from one end to the other and holds the armature at the end of travel. However, much of the force for moving the armature is provided by a spring exerting a force on the shaft with respect to the back iron section. In one embodiment, the spring is a compression-tension spring. Alternatively, two compression springs acting in opposition are provided.

Abstract: Some heat pumps have displacers mechatronically-controlled via springs and coils acting upon a ferromagnetic plate. In some prior art heat pumps, the components are housed in hot parts of the heat pump and in others, the components are housed in a cold part of the heat pump, but the components are offset from a central axis of the heat pump. A heat pump with the mechatronic driver components collinear with a central axis of the heat pump has the components in a cold part of the heat pump.

Abstract: 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.

Abstract: A gas-fired heat pump has been built with a mechatronic system. Stators (a coil in a back iron) are provided at the ends of travel to draw armatures which are coupled to displacers from one end to the other. It has been found that such a system requires high current flow to draw the displacer when it is at a great distance from the stator. Additionally, it has been found to be difficult to control the current in the coils to ensure a soft landing. A linear actuation system is disclosed in which in addition to the stators at the end of travel (face stators) side stators are provided along the travel to control the linear actuator particularly during mid-travel.

Abstract: A thermodynamic apparatus, such as a Stirling engine or a Vuilleumier heat pump, has a heat exchanger in which energy is exchanged between a working fluid and an exhaust gas stream. On top of the cylinder of the thermodynamic apparatus is a dome-shaped section. By incorporating the heat exchanger within the dome, the flow paths can be simplified, the number of separate components reduced, and overall weight reduced. Flow passages for the working fluid are embedded in the dome. Channels for the exhaust gases are formed in an outer surface. The passages and the channels are helically arranged, one clockwise and one counter clockwise. The dome can be cast with a core for the casting fabricated via three-dimensional printing. In some embodiments, the dome is made of fiber-reinforced material.

Abstract: 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.

Abstract: 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.

Abstract: Some heat pumps have displacers mechatronically-controlled via springs and coils acting upon a ferromagnetic plate. In some prior art heat pumps, the components are housed in hot parts of the heat pump and in others, the components are housed in a cold part of the heat pump, but the components are offset from a central axis of the heat pump. A heat pump with the mechatronic driver components collinear with a central axis of the heat pump has the components in a cold part of the heat pump.

Abstract: A thermodynamic apparatus, such as a Stirling engine or a Vuilleumier heat pump, has a heat exchanger in which energy is exchanged between a working fluid and an exhaust gas stream. On top of the cylinder of the thermodynamic apparatus is a dome-shaped section. By incorporating the heat exchanger within the dome, the flow paths can be simplified, the number of separate components reduced, and overall weight reduced. Flow passages for the working fluid are embedded in the dome. Channels for the exhaust gases are formed in an outer surface. The passages and the channels are helically arranged, one clockwise and one counter clockwise. The dome can be cast with a core for the casting fabricated via three-dimensional printing. In some embodiments, the dome is made of fiber-reinforced material.

Abstract: Reciprocating apparatuses such as a displacer in a Stirling engine or Vuilleumier (thermally-driven) heat pump and such as a poppet valve in an internal combustion engine have been known to be built with a mechatronic actuator. The reciprocating element has two springs in compression biased against each other. It has been found that conventional springs in compression introduce losses. A spring is disclosed in which a portion of the coil is wound in a clockwise direction and a portion is wound in a clockwise direction. Also, in reciprocation, the spring is in compression at one end of travel and in tension at the other end of travel.

Abstract: 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.

Abstract: A thermally driven heat pump is disclosed in which at least most of the warm heat exchanger is disposed within the cylinder between the hot and cold displacers. Such an arrangement is not suitable for a prior art heat pump in which movement of the displacers is based on a crank because it would lead to too much dead volume in the system. However, with mechatronically-controlled displacers in which the displacers are independently controlled, the displacers can reciprocate up to the heat exchanger. Such a configuration reduces dead volume compared to prior art Vuilleumier heat pumps in which the warm exchanger occupies a portion of an annular space between the cylinder in which the displacers move.

Abstract: Regenerators for Stirling engines and Vuilleumier heat pumps are difficult to reliably manufacture. A regenerator is disclosed in which edges of the regenerator wire meshes are coated with a stabilizing material. The regenerator wire meshes are then sufficiently stable to be machined to the dimensions of the housing. In some embodiments, the material on the outer surface of the edges of the regenerator is relatively thermally insulating to limit heat transfer to the housing.

Abstract: Newly-developed manufacturing techniques have opened up new possibilities in fabricating designs of components that were previously infeasible. One such component is a heat exchanger. A crossflow heat exchanger is disclosed that includes a plurality of internal passages for conducting a first fluid. The internal passages that form a spiral with adjacent passages separated by a gap of a predetermined distance or less. The second fluid passes through the gaps. The internal passages may be a plurality of parallel passages arranged along a first line. From upstream to downstream, each of the passages form an inlet spiral connected to an inner ring connected to an outlet spiral. The gaps are less than a predetermined distance related to a Reynolds number that is less than that at which laminar flow exists.

Abstract: 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.

Abstract: Substituting a solar concentrator for a conventional burner for heating is desirable. However, the sun's energy is diurnal and cannot be counted upon even during daylight hours. To ensure heating is available, a backup conventional combustor can be provided. According to the present disclosure, a heat exchanger element of the heater assembly is directly acted upon by solar rays via a solar concentrator and by combustion. The heat exchanger acts as the combustion holder. Fuel provided to the outside of the heat exchanger is adjusted based on the demanded for heating and the amount of insolation achieved via the solar concentrator. The heat exchanger can be part of a conventional heater or a heat pump for heating water.