Our projects

_{Vuilleumier cryocooler design concept}

While the cycle is effectively a heat engine driving a refrigerator at a potentially lower overall COP, the design offers advantages for the intended application. The project is currently in its simulation and design stage; manufacturing is expected to start towards the end of 2026.

While the first test rig will not be tested on a rotor, a concurrent PhD project is concerned with contact-free induction heating and contact-free power transmission and control of two linear motors that will enable the future operation on the Vuilleumier cryocooler in rotation. This concept will be implemented in subsequent test.

The beauty of thermoacoustic machines is the fact that there are no moving parts involved. This makes them very reliable and highly attractive for the cooling of a superconductive rotor. However, due to the wavelengths of the acoustic waves involved, the resonator tube tends to be very long. A current PhD project is currently under way to build a travelling-wave thermoacoustic refrigerator and explore what effect coiling or bending of the resonator tube has on its performance to make them more compact. Los Alamos National Laboratory’s software Delta EC and David Gedeon’s software Sage were used for the modelling. A test rig is currently being assembled (Figures 2 and 3), and experiments are expected to start in the second half of 2026.

_{Thermoacoustic refrigerator test rig}

_{Linear motor development}

Linear motion of pistons and displacers is the preferred operation in Stirling machines as it does not introduce any side load that would lead to increased wear of seals. To drive pistons and displacers in Stirling refrigerators, linear motors are the most common way of achieving this. THERA Lab has started its own linear motor development on a very basic level (Figure 4).

Following on from our previous liquid piston experiments in a four-cylinder Siemens configuration (Figure 5) which were limited in terms of the frequency we could achieve (typically less than 10 Hz), we moved on to using solid pistons (Figure 6). While the advantage of liquid pistons are their total lack of gas leakage, their self-lubrication, and absence of having to machine anything, they would have to be very long to achieve significant amplitudes, and thus, pressure fluctuations. We decided to use solid pistons supported by flexure bearings to be able to tune the natural frequency of the system by changing the piston mass and/or the stiffness of the bearings.

_{Four-cylinder heat engine in Siemens configuration using liquid pistons}

In a current PhD project, we’re investigating the effect of rotation on the performance of heat pipes (Figure 7). An essential part of this project is the optimisation of the wick structure that we are planning to 3d-print.

_{Rotating heat pipe test rig}

_{OpenStar Technologie’s nuclear fusion reactor concept (courtesy of OpenStar Technologies)}

In collaboration with OpenStar Technologies in Wellington, a Master’s project is investigating the conveyance of Neon slush (solid phase suspended in liquid phase) to cool the superconducting magnet that confines a fusion plasma.  Fluid dynamics of slush will be analysed to ensure high solid fraction is delivered to the magnet to maximise the cooling capacity of the latent heat. The challenge will be in creating and validating a model slush system which is realistic enough to enable design of a real system.

_{AI-supported gear optimisation tool}

_{Tim Hart of Compact Motorsport (courtesy of Compact Motorsport)}