Recent advancements in lubrication and cooling strategies have shown potential for improving the performance of rolling-element bearings. However, a lack of a level playing field for comparing different strategies exists. In this study, a multi-bearing system modeling framework to simulate various cooling and lubrication strategies for rolling-element bearings is developed. The framework facilitates the evaluation of novel cooling and lubrication concepts, in conjunction with both passive and active control strategies. Analyses performed on a multi-bearing system model show that implementing smarter lubrication and cooling strategies in rotary machines can reduce friction losses by 14.8% under a dynamic load. The results offer valuable insights for designing and optimizing machinery, paving the way for energy-efficient and durable systems in various industrial applications.

Hybrid concentrated solar power/photovoltaic systems (CSP/PV) combine the advantages of the two separate systems while reducing their drawbacks. The design of such a hybrid system is challenging due to the various trade-offs between the thermal and electrical performance, and the overall system complexity. A reliable simulation model that includes all relevant optical, thermal, and photovoltaic aspects, can therefore be extremely useful to analyse the combined system performance and fine-tune the various design parameters. While multi-physics modelling of photovoltaic systems is well established, this is not the case for hybrid CSP/PV. In this paper, a novel multi-physics framework is presented for a hybrid system consisting of a parabolic trough with integrated PV cells covered by a dichroic coating, focusing incident sunlight towards a thermal receiver. Instead of monofacial PV cells, bifacial cells are considered for harvesting also the diffuse and ground reflected light at the back of the trough. The presented framework relies on an existing simulation tool for PV modules, that is combined with a ray-tracer that includes the spectral beam splitting functionality of the coating, and a novel 1.5D thermal model for the receiver tube. Long term outdoor monitoring results are used to predict the averaged, time-resolved annular thermal and electric energy yield of the system. This energy production is compared for three different multilayer coating designs with an increasing amount of (TiO 2 , SiO 2 ) layers. These results show that the amount of reflected sunlight towards the thermal receiver can be enhanced at the expense of the transmitted sunlight towards the PV cells, when a higher number of layers are used. The reduction of the incident power on the PV cells is however almost fully compensated by the enhanced spectral match of the transmitted light with the spectral response of the considered bifacial cells, in addition to the enhanced cell efficiency due to the lower thermalization losses. This results in superior system efficiency, for the application scenario where the generated thermal energy is also converted in electrical energy, and geographical locations with sufficient direct sunlight; a conclusion that is drawn from comparing the total electrical energy yield in Spain and Belgium, as a function of the thermal to electrical conversion fraction.

Electric vehicles are gaining popularity in the transport sector due to growing concerns over climate change.The driving range of these vehicles remains a challenge and higher power densities are therefore needed, which leads to higher heat fluxes.Proper thermal management is crucial to prevent premature breakdown of the wire insulation and demagnetization.Traditionally, the machine is cooled using a stator jacket, sometimes with end-winding jet cooling.These methods are mostly sufficient to cool the stator region, but could be insufficient to cool the rotor region at high rotational speeds where high frequencies cause higher losses in the rotor.As a result, rotor cooling techniques are increasingly proposed, where the use of lubrication oil allows to bring the coolant closer to the heat source due to its dielectric properties.By using oil for cooling and lubrication, there is a possibility to eliminate the water-glycol circuit of the vehicle to increase the power density further.Various state-of-the-art and novel rotor oil cooling concepts are compared within this study based on the thermohydraulic performance for a high-speed permanent magnet synchronous machine.The methods include hollow shaft, rotor jet, direct magnet and rotor jacket cooling in a closed and open loop configuration.The performance of these concepts is simulated using MotorCAD and an in-house developed zonal thermal model which makes use of 2D finite element simulations and analytical methods to construct a three dimensional equivalent thermal network of the complete machine.As a manner of validation a comparison is made between the results of the models for a stator jacket and end-winding cooled machine in a closed loop configuration and it is shown that the steady-state temperatures correspond well.The relative difference in temperature with respect to the coolant temperature between both models is found to be below 0.9%.The magnet temperatures in these validation cases with only stator cooling methods exceed the limit of 150°C, showing the need for rotor cooling.Of the studied rotor cooling methods, hollow shaft cooling does not add a significant improvement in performance, while simulations with hub jet do show an increase in performance.The highest performance is obtained for the direct magnet and rotor jacket cooling methods, where the relative permanent magnet to coolant temperature can be improved by 68% and 44% for respectively the closed and open loop configuration compared to the benchmark, while the hydraulic performance is only slightly lower (less than 10%).

Latent heat storages have numerous times been demonstrated to benefit from including highly conductive fin structures for elevated charging and discharging properties. However, to this point it is still unclear how fins should be designed for optimal charging performance while meeting constraints on minimum storage density and manufacturability. Therefore, in the present work, we use topology optimization to obtain optimal designs for rectangular Phase Change Material (PCM) modules charged by a water flow, based on a conductive heat transfer model for the PCM. The optimal topologies are designed for maximum mean charging power of the PCM over a desired charge time. The optimal designs feature tree-like metal structures with an increased amount of branching for higher power requirements. Moreover, the optimal topologies are compared with straight fins with an equal minimal length scale. This comparison reveals the sub-optimality of the obtained tree-like designs for conduction driven phase-change problems.

The development of the next generation electrical vehicles requires drive-trains to become more compact, high-performant, and robust at the lowest possible cost. These more compact drive-trains operate at the same power ratings as their bigger sized equivalent and do need to dissipate their heat in a smaller volume. Therefore, more advanced liquid cooling methods of the drive-train components are needed to enhance the heat removal and increase the compactness, i.e., power density. Recent studies showed the high potential of direct oil jet cooled motor windings as one of the most promising cooling solution. However, several challenges need to be tackled to make such a jet cooling method robust. Therefore, this paper presents a method on how to achieve a robust oil jet cooled design systematically. From a pre-selection of an oil matching the lubrication & cooling conditions of the powertrain, an expert selection of sub-component materials for the motor design, the best robust motor design have been determined. This has been achieved via a degradation validation guide which includes standard oil-material degradation tests, electrical insulation, DC break down voltage tests, and a final motor testing validation phase.

Charging of latent heat storages is hampered by the low PCM thermal conductivity. Moreover, the lack of design rules for LHSs complicates the development of commercial compact storages. In the present work, the combined charging power and storage density is presented for PCM storages enhanced by highly conductive aluminium fins, charged by a water flow with a finite total heat capacity, and dominated by conductive heat transfer in the PCM. The performance maps are valid for low temperature differences and small PCM enclosures, as for such designs effects of natural convection can be neglected. We show that the overall storage performance can be estimated from a unit cell approach which greatly reduces the computational effort. Moreover, reducing the individual compartment height as well as slowly and simultaneously charging the individual cells is demonstrated to be effective for increased charging performance.

The increasing need for high power density electrical drivetrains necessitates advanced cooling approaches to avoid overheating of components. Unfortunately, the use of multiple coolants requires different cooling circuits with according equipment which hampers the way towards high power densities. Therefore, in this work, we present a full thermal-hydraulic model of an electrical drivetrain which is cooled by a single oil cooling circuit using the Simscape Matlab environment. The thermal-hydraulic model is verified using more advanced computational tools, and is aimed to investigate the thermal response of the electrical drivetrain under varying load conditions and using different cooling approaches.

In this research, optimal fin distributions are presented for latent heat storages charged by a constant input power water flow. The limited input power results in non-uniform melting of the Phase Change Material (PCM). Therefore, new designs with non-uniform fin distributions provide the opportunity to outperform the ones with uniform distributions. In this paper, we show that different optimal fin distributions are found depending on the fin width, amount of fins and the input power. The gain in charging performance is discussed by comparing with latent heat storages without heat transfer enhancement.