No description available.

Electrification of vehicles is necessary to combat greenhouse gas emissions, whichcauses global warming and climate change. There has been a demand in the use ofBattery Electric Vehicles due to this increased awareness of sustainability. However,they have been beset with issues such as range and conservation of energy. A partof the solution could be an energy-efficient thermal management system. A 1-Dimensional (1-D) complete vehicle thermal model in GT-SUITE is used topredict the energy efficiency of the vehicle at the conceptual stage. The model helpspredict results quickly and is used for complete system-level simulations. This thesisfocuses on optimizing the method for predicting the realistic and accurate energyconsumption of the thermal management system in the vehicle at the 1-D level. TheCompact Modular Architecture (CMA) platform, which is the vehicle platform usedin current production cars by Volvo Cars will be used for the study and all studiesare performed using a standardized drive cycle. Initial sensitivity studies with afully open grille are performed to understand the operating points of the variouscomponents of interest to investigate. The mass flow rate, ambient temperature,battery temperature, and cooling fan speed are varied.The Active Grille Shutters (AGS) which provides aerodynamic benefit at high speedis implemented in the existing thermal model which could previously accommodateonly the fully open grille. This allows the grille shutters to vary at different anglesbased on cooling demand. The previous existing thermal model method also neededto be optimized to accommodate the AGS. The cooling fan control logic needed tobe improved for better accuracy and energy consumption prediction. Furthermore,the grille shutters and cooling fan speed is needed to regulate the amount of air flowthrough the heat exchangers for the model to behave as close to a real productionvehicle. A code was developed which generated fan speed and grille shutter anglesbased on mass flow rate values to input in the model.Further investigations were made with the optimized thermal model with AGS tostudy the influence of additional mass flow rate on the mass power consumptionof the thermal management system components of interest. It was observed in the initial sensitivity studies that the additional mass flow rate saw significant power savings. However, with the implementation of AGS and additional mass airflowinto the system, the power due to the variation of shutters is taken into account.The results indicate that the total power consumption gradually decreases with theincreasing mass flow rate. But, this is up to a certain extent where the energyconsumption due to the shutter opening takes over the overall power consumptionof the vehicle and overcomes the savings seen by other components in the system causing the total power to increase.

Global warming imposes great challenges, and anthropogenic greenhouse gas emissions have to be reduced by active measures. The transportation sector is one of the key sectors where significant reductions are desired. Within a vehicle, the cooling/thermal management system is a subsystem intended for temperature control of automotive components. Reducing the power consumption for thermal management is one of several possible ways to reduce the environmental impact of the vehicle. This report considers an existing reference cooling system, with three separate circuits at different temperature levels. The purpose is to suggest improvements to the reference system with respect to increasing energy efficiency as well as reducing the number of components. Potential improvements are identified during a literature study, and then evaluated one by one. After the first evaluation, four improvements are selected: Firstly, a liquid-to-liquid heat exchanger in high temperature circuit, with connections to both the medium and low temperature circuits. Secondly, common medium/low temperature radiators, which can be allocated according to cooling demand. Thirdly, pipe connections for coolant transfer between the low and medium temperature circuits. Finally, a liquid-cooled condenser in the active cooling system, cooled by the medium temperature circuit. The result is a system with flexible radiator allocation, more even load distribution, ability to heat components using heat losses from other components, and one radiator less than the reference system. A complete system evaluation is performed in order to find the most beneficial arrangement of the components. Steady state calculations are performed in MATLAB, using five different operational cases as input data. Out of six different alternatives, one is recommended for high load operation and another for low load operation. The difference between the two is the position of the condenser, since a low condensation temperature should be prioritized at part load but not at high load. The main uncertainties of this report are steady state calculations, which are not fully reflecting real driving situations, and approximations due to lack of input data. For further work, verification of these results by transient simulations and practical testing is recommended. Removing one of the high temperature radiators could be investigated, as well as downsizing the medium temperature radiator. Integration with the cabin thermal management system, which is beyond the scope of this report, is also a relevant area for future investigation. By suggesting improvements to an automotive subsystem, this report strives to make a difference on a small-scale level, but also to contribute to an ongoing transition process on the global level. / Den globala uppvärmningen medför stora utmaningar, och de antropogena växthusgasutsläppen måste minskas genom aktiva åtgärder. Transportsektorn är en av de viktigaste sektorerna där avsevärda utsläppsminskningar eftersträvas. I ett fordon är kylsystemet ett delsystem avsett att kontrollera temperaturen på komponenter som är viktiga för fordonets funktion. Att sänka kylsystemets effektförbrukning är ett av flera möjliga sätt att minska fordonets miljöpåverkan. Den här rapporten utgår från ett befintligt referenskylsystem, med tre separata kretsar som arbetar vid olika temperaturnivåer. Syftet är att föreslå förbättringar för att öka energieffektiviteten, samt minska antalet komponenter i systemet. Potentiella förbättringar identifieras genom en litteraturstudie, och utvärderas därefter en efter en. Efter denna utvärdering väljs fyra förbättringar ut: För det första, en vätskevärmeväxlare i högtemperaturkretsen, med anslutningar till både mellan- och lågtemperaturkretsen. För det andra, gemensamma mellan- och lågtemperaturkylare, som kan fördelas mellan kretsarna efter behov. För det tredje, röranslutningar för överföring av kylvätska mellan låg- och mellantemperaturkretsen. Slutligen, en vätskekyld kondensor i det aktiva kylsystemet, vilken kyls av mellantemperaturkretsen. Resultatet är ett kylsystem med flexibel tilldelning av kylare, jämnare fördelning av värmeförluster, möjlighet att värma komponenter med förlustvärme från andra komponenter, samt en kylare mindre än referenssystemet. Som sista steg genomförs en helsystemsutvärdering, för att hitta det mest fördelaktiga sättet att placera komponenterna i förhållande till varandra. Stationära beräkningar utförs i MATLAB, med fem olika driftfall som indata. Av sex olika utformningar rekommenderas en för drift med hög belastning, och en annan för drift med lägre belastning. Skillnaden mellan dem är kondensorns placering, på grund av att en låg kondensationstemperatur bör prioriteras vid låg belastning men inte vid hög belastning. Den största osäkerheten i tillvägagångssättet är de stationära beräkningarna, som inte helt motsvarar verkliga körfall, samt approximationer som gjorts vid brist på indata. För framtida arbete rekommenderas verifiering av dessa resultat genom transienta simuleringar och praktiska tester. Att ta bort en av högtemperaturkylarna och/eller minska storleken på mellantemperaturkylaren kan också undersökas. Även integration med kupéns värme- och kylsystem, vilket ligger utanför ramen för denna rapport, är ett relevant område för fortsatta undersökningar. Genom att föreslå förbättringar av ett delsystem i ett fordon strävar denna rapport efter att åstadkomma förbättringar på liten skala, men också att bidra till en pågående omvandling på den globala skalan.

The transient thermal response of a 15-cell, 48 volt, lithium-ion battery pack for an unmanned ground vehicle was simulated with ANSYS Fluent. Heat generation rates and specific heat capacity of a single cell were experimentally measured and used as input to the thermal model. A heat generation load was applied to each battery and natural convection film boundary conditions were applied to the exterior of the enclosure. The buoyancy-driven natural convection inside the enclosure was modeled along with the radiation heat transfer between internal components. The maximum temperature of the batteries reached 65.6 °C after 630 seconds of usage at a simulated peak power draw of 3,600 watts or roughly 85 amps. This exceeds the manufacturer's maximum recommended operating temperature of 60 °C. The pack was redesigned to incorporate a passive thermal management system consisting of a composite expanded graphite matrix infiltrated with a phase-changing paraffin wax. The redesigned battery pack was similarly modeled, showing a decrease in the maximum temperature to 50.3 °C after 630 seconds at the same power draw. The proposed passive thermal management system kept the batteries within their recommended operating temperature range.

<p>An emerging technology in the field of transient thermal management is thermal energy storage, or TES, which enables temporary, on-demand heat rejection via storage as latent heat in a phase-change material.  Latent TES devices have enabled advances in many thermal management applications, including peak load shifting for reducing energy demand and cost of HVAC systems and providing supplemental heat rejection in transient thermal management systems.  However, the design of a transient thermal management system with integrated storage comprises many challenges which are yet to be solved.  For example, design approaches and performance metrics for determining the optimal dimensions of the TES device have only recently been studied.  Another area of active research is estimation of the internal temperature state of the device, which can be difficult to directly measure given the transient nature of the thermal storage process.  Furthermore, in contrast to the three main functions of a thermal-fluid system--heat addition, thermal transport, and heat rejection--thermal storage introduces the need for active, real-time control and automated decision making for managing the operation of the thermal storage device. </p> <p>In this thesis, I present the design process for integrating thermal energy storage into a single-phase thermal management system for rejecting transient heat loads, including design of the TES device, state estimation and control algorithm design, and validation in both simulation and experimental environments. Leveraging a reduced-order finite volume simulation model of a plate-fin TES device, I develop a design approach which involves a transient simulation-based design optimization to determine the required geometric dimensions of the device to meet transient performance objectives while maximizing power density.  The optimized TES device is integrated into a single-phase thermal-fluid testbed for experimental testing.  Using the finite volume model and feedback from thermocouples embedded in the device, I design and experimentally validate a state estimator based on the state-dependent Riccati equation approach for determining the internal temperature distribution to a high degree of accuracy.  Real-time knowledge of the internal temperature state is critical for making control decisions; to manage the operation of the TES device in the context of a transient thermal management system, I design and test, both in simulation and experimentally, a logic-based control strategy that uses fluid temperature measurements and estimates of the TES state to make real-time control decisions to meet critical thermal management objectives. Together, these advances demonstrate the potential of thermal energy storage technology as a component of thermal management systems and the feasibility of logic-based control strategies for real-time control of thermal management objectives.</p>

Managing the thermal loads inside a non-airbreathing hypersonic vehicle is particularly difficult. The heat generated by the power electronics, avionics, etc. must be removed so that the components do not exceed their maximum temperatures. These vehicles cannot dump the waste heat into fuel or ram air because they carry no fuel and do not have provisions for ram air. This means that the thermal energy resulting from the heat generated must be dumped into an onboard heat sink. Existing solutions to this problem have been passive systems based on solid-liquid phase change materials (PCMs), which store thermal energy as they melt. Since space is at a premium, a heat sink must store a lot of energy per unit volume, while keeping components below their maximum temperature. In this project, three heat sink concepts are tested, i.e., one based on PCMs, a second on thermal to chemical (TTC) energy storage, and a third on a hybrid combination of the first two. For the first, three different PCMs are tested and for the second a single endothermic chemical reaction. The hybrid PCM/TTC concept consists of a single PCM which plays the dual role of PCM and reactant in the endothermic chemical reaction of the TTC energy storage. To enhance heat sink performance, the use of thermoelectric generators (TEGs) and a local coolant loop are investigated. The advantage of the former is that they transform waste heat into usable electricity, reducing the amount of thermal energy that needs to be stored by the heat sink. The advantage of the latter is that it results in a more uniform cooling of the heat source and more uniform heating of the heat sink. Prototypes of each of the heat sink concepts and the coolant loop are designed, built, and tested. Experimental results indicate that all the solutions tested in this project outperform widely used paraffin heat sink technologies on an energy per unit volume basis. Our experiments also show that a local coolant loop is indeed advantageous and that current off-the-shelf thermoelectric generators do not generate enough power to offset the power requirements of the coolant loop. Significant improvements in the ZT factor of the thermoelectric materials used by the TEG would be required. / Master of Science / All electronics produce waste heat and have a maximum operating temperature above which they fail due to overheating. Heat sinks absorb the waste heat and prevent overheating. Non-airbreathing hypersonic vehicles do not have natural heat sinks like intake air or liquid fuel which are commonly used as heat sinks in airbreathing vehicles. Heat cannot be transferred to the environment due to the high temperatures caused by the friction of hypersonic air travel. This means that all waste heat must absorbed by an onboard heat sink. Existing heat sinks in non-airbreathing hypersonic vehicles use paraffin based solid-liquid phase change materials (PCMs) which store thermal energy as they melt. Three novel heat sink options are evaluated in this project, hydrated salt PCMs which absorb energy as they melt, a chemical reaction which absorbs heat as it reacts, and a hybrid system which incorporates one of the hydrates salt PCM as a reactant in the chemical reaction. Because space is at a premium, these options are evaluated by the amount of energy they can absorb (kilojoules) per unit volume (in3) while keeping the electronics below their maximum temperature. To enhance heat sink performance, the use of thermoelectric generators (TEGs) and a local coolant loop are investigated. The advantage of the former is that they transform waste heat into usable electricity, reducing the amount of thermal energy that needs to be stored by the heat sink. The advantage of the latter is that it results in a more uniform cooling of the electronics and more uniform heating of the heat sink. Prototypes of each of the heat sink concepts and the coolant loop are designed, built, and tested. Experimental results indicate that all the solutions tested in this project outperform widely used paraffin heat sink technologies on an energy per unit volume basis. Our experiments also show that a local coolant loop is indeed advantageous and that current off-the-shelf thermoelectric generators do not generate enough power to offset the power requirements of the coolant loop. Significant improvements in the state of the art of thermoelectric materials would be required for TEGs to generate enough electricity from our waste heat load to power the local coolant loop.

No description available.

Energy storage within hypersonic aircraft is becoming increasingly important with the development of more sophisticated electronic components and is an integral piece of expanding their overall capabilities. Hypersonics not only produce large external thermal loads, but also an abundance of internal thermal loads from components such as power electronics, avionics, and batteries. Additionally, limited volume within such vehicles introduces additional constraints. Thus, having efficient heat sinks that are capable of storing much of these heat loads is imperative. Passive thermal management systems, i.e., heat sinks, are preferable in most applications because they do not require power input to operate, and they are typically smaller than active systems such as coolant loops. In identifying and developing heat sinks with increased energy storage capability, an exhaustive search of available phase change materials (PCMs) is conducted. PCMs have been used in hypersonic vehicles in the past as a means of energy storage. Additionally, the use of energy-consuming endothermic reactions is considered. An innovative PCM-endothermic reaction hybrid approach is also developed. Both thermodynamic and transient/quasi-stationary models are developed for each of these proposed heat sink technologies. Prototypes are then developed for the best candidates to validate the models and draw conclusions on each heat sink's performance. Both the thermodynamic modeling and experimental results presented in this paper suggest that PCMs, endothermic reactions, and, especially, the hybrid system show greater energy storage capabilities than what is being used in hypersonic vehicles currently. / Master of Science / Hypersonic vehicles are an important topic of interest in the aerospace and defense industries. To be classified as hypersonic, a vehicle must travel at or above Mach 5, which is at least five times the speed of sound. Hypersonic vehicles often travel at high altitudes and a common application of the technology is in missiles. One major hurdle in developing hypersonic technologies at lower altitudes is that because of the high speeds, the outside skin temperature of the vehicle can reach thousands of degrees. Clearly, these temperatures can affect the heat load on the inside of the vehicle as can the thermal energy release of internal components such as the power electronics, the avionics, etc. To deal with these internal heat loads, innovative energy storage solutions are needed to efficiently and effectively store the thermal energy released internally. One approach considered here is the use of phase change materials (PCMs) as a storage medium. Melting such a material requires large amounts of energy and occurs at constant temperature. This is much more advantageous than heating a material in which only the temperature rises. Another approach considered in this thesis is that of using a chemical reaction, which requires energy input to proceed. Such a reaction is called an endothermic reaction and often results in a temperature decrease. Thus, simply mixing a set of reactants and adding energy helps cool the system. A final approach considered is a hybrid one, which combines a PCM material and an endothermic reaction. Such an approach combines the advantages of both. Each of these approaches are modeled thermodynamically to better understand how devices based on them work. Physical prototypes are then designed, built, and tested to confirm their performance. Both the modeling and experimental results presented in this thesis suggest that these devices show significantly improved energy storage capabilities over the devices currently used in hypersonic vehicles.

Thermal energy storage (TES) consists in storing heat for a later use, thereby reducing the gap between energy availability and demand. The most diffused materials for TES are the organic solid-liquid phase change materials (PCMs), such as paraffin waxes, which accumulate and release a high amount of latent heat through a solid-liquid phase change, at a nearly constant temperature. To avoid leakage and loss of material, PCMs are either encapsulated in inert shells or shape-stabilized with porous materials or a nanofiller network. Generally, TES systems are only a supplementary component added to the main structure of a device, but this could unacceptably rise weight and volume of the device itself. In the applications where weight saving and thermal management are both important (e.g. automotive, portable electronics), it would be beneficial to embed the heat storage/management in the structural components. The aim of this thesis is to develop polymer composites that combine a polymer matrix, a PCM and a reinforcing agent, to reach a good balance of mechanical and TES properties. Since this research topic lacks a systematic investigation in the scientific literature, a wide range of polymer/PCM/reinforcement combinations were studied in this thesis, to highlight the effect of PCM introduction in a broad range of matrix/reinforcement combinations and to identify the best candidates and the key properties and parameters, in order to set guidelines for the design of these materials. The thesis in divided in eight Chapters. Chapter I and II provide the introduction and the theoretical background, while Chapter III details the experimental techniques applied on the prepared composites. The results and discussion are then described in Chapters IV-VII. Chapter IV presents the results of PCM-containing composites having a thermoplastic matrix. First, polyamide 12 (PA12) was melt-compounded with either a microencapsulated paraffin (MC) or a paraffin powder shape-stabilized with carbon nanotubes (ParCNT), and these mixtures were used as matrices to produce thermoplastic laminates with a glass fiber fabric via hot-pressing. MC was proven more suitable to be combined with PA12 than ParCNT, due to the higher thermal resistance. However, also the MC were considerably damaged by melt compounding and the two hot-pressing steps, which caused paraffin leakage and degradation, as demonstrated by the relative enthalpy lower than 100 %. Additionally, the PCM introduction decreased the mechanical properties of PA12 and the tensile strength of the laminates, but for the laminates containing MC the elastic modulus and the strain at break were not negatively affected by the PCM. Higher TES properties were achieved with the production of a semi-structural composite that combined PA12, MC and discontinuous carbon fibers. For example, the composite with 50 wt% of MC and 20 wt% of milled carbon fibers exhibited a total melting enthalpy of 60.4 J/g and an increase in elastic modulus of 42 % compared to the neat PA. However, the high melt viscosity and shear stresses developed during processing were still responsible for a not negligible PCM degradation, as also evidenced by dynamic rheological tests. Further increases in the mechanical and TES properties were achieved by using a reactive thermoplastic matrix, which could be processed as a thermosetting polymer and required considerably milder processing conditions that did not cause PCM degradation. MC was combined with an acrylic thermoplastic resin and the mixtures were used as matrices to produce laminates with a bidirectional carbon fabric, and for these laminates the melting enthalpy increased with the PCM weight fraction and reached 66.8 J/g. On the other hand, the increased PCM fraction caused a rise in the matrix viscosity and so a decrease in the fiber volume fraction in the final composite, thereby reducing the elastic modulus and flexural strength. Dynamic-mechanical investigation evidenced the PCM melting as a decreasing step in ’; its amplitude showed a linear trend with the melting enthalpy, and it was almost completely recovered during cooling, as evidenced by cyclic DMA tests. Chapter V presents the results of PCM-containing thermosetting composites. A further comparison between MC and ParCNT was performed in a thermosetting epoxy matrix. First, ParCNT was mixed with epoxy and the mixtures were used as matrices to produce laminates with a bidirectional carbon fiber fabric. ParCNT kept its thermal properties also in the laminates, and the melting enthalpy was 80-90 % of the expected enthalpy. Therefore, ParCNT performed better in thermosetting than in thermoplastic matrices due to the milder processing conditions, but the surrounding matrix still partially hindered the melting-crystallization process. Therefore, epoxy was combined with MC, but the not optimal adhesion between the matrix and the MC shell caused a considerable decrease in mechanical strength, as also demonstrated by the fitting with the Nicolais-Narkis and Pukanszky models, both of which evidenced scarce adhesion and considerable interphase weakness. However, the Halpin-Tsai and Lewis-Nielsen models of the elastic modulus evidenced that at low deformations the interfacial interaction is good, and this also agrees with the data of thermal conductivity, which resulted in excellent agreement with the Pal model calculated considering no gaps at the interface. These epoxy/MC mixtures were then reinforced with either continuous or discontinuous carbon fibers, and their characterization confirmed that the processing conditions of an epoxy composite are mild enough to preserve the integrity of the microcapsules and their TES capability. For continuous fiber composites, the increase in the MC fraction impaired the mechanical properties mostly because of the decrease in the final fiber volume fraction and because the MC phase tends to concentrate in the interlaminar region, thereby lowering the interlaminar shear strength. On the other hand, a small amount of MC enhanced the mode I interlaminar fracture toughness (Gic increases of up to 48 % compared to the neat epoxy/carbon laminate), as the MC introduced other energy dissipation mechanisms such as the debonding, crack deflection, crack pinning and micro-cracking, which added up to the fiber bridging. Chapter VI introduces a fully biodegradable TES composite with a thermoplastic starch matrix, reinforced with thin wood laminae and containing poly(ethylene glycol) as the PCM. The wood laminae successfully acted as a multifunctional reinforcement as they also stabilized PEG in their inner pores (up to 11 wt% of the whole laminate) and prevent its leakage. Moreover PEG was proven to increase the stiffness and strength of the laminate, thereby making the mechanical and TES properties synergistic and not parasitic. Finally, Chapter VII focused on PCM microcapsules. The synthesis of micro- and nano-capsules with an organosilica shell via a sol-gel approach clarified that the confinement in small domains and the interaction with the shell wall modified the crystallization behavior of the encapsulated PCM, as also evidenced by NMR and XRD studies and confirmed by DSC results. In the second part of Chapter VII, a coating of polydpamine (PDA) deposited onto the commercial microcapsules MC. The resulting PDA coating was proven effective to enhance the interfacial adhesion with an epoxy matrix, as evidenced by SEM micrographs. XPS demonstrated that the PDA layer was able to react with oxirane groups, thereby evidencing the possibility of forming covalent bond with the epoxy matrix during the curing step.

A Thesis Submitted to the School of Graduate Studies in Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in Mechanical Engineering / In the wake of the rising global demand for more electric transportation, aerospace electrification is becoming a highly active research area as commercial fully electric aircrafts are becoming a reality. The transportation electrification industry is challenged to develop powerful, safe, and compact-sized machines that can replace fossil fuel powered engines in aircrafts. Axial Flux Permanent Magnets (AFPM) machines are currently being intensively developed as a great candidate for this purpose due to their inherently higher power density compared to other machine electric machines topologies. The efforts of further increasing AFPM machines power density add more thermal challenges as intensive cooling is required at a relatively small machine package to avoid machine failure. One of the most concerning failure modes in these machines is power output reduction due to overheating of the rotor-mounted permanent magnets or even complete failure due to irreversible demagnetization. This research discusses the design process of an integrated rotor air cooling system for a 100 kW AFPM machine designed for an electric aircraft propulsion system. The embedded cooling system allows the rotor to be self-cooled at a sufficient cooling rate while minimizing the impact on machine efficiency due to windage power losses. The presented design process includes several stages of cooling enhancement including the addition and fine-tuning of rotor fan blades and rotor vents design. These enhancements are done by studying the air flow over the rotor surfaces in conjunction with heat transfer through Conjugate Heat Transfer (CHT) Computational Fluid Dynamics (CFD) analyses. In an initial study, different rotors with different combinations of rotor cooling features are studied and their thermal performance is compared. The results show that using rotor embedded fan blades in throughflow ventilated rotor geometry offers the best performance balance, achieving sufficient rotor cooling rate within a reasonable increase of windage power loss. A parametric study is performed to improve the rotor blade geometry for a higher ratio of heat transfer to windage losses. Another study is performed where the rotor and the enclosure geometries are fine-tuned simultaneously to reduce the negative effect on rotor heat transfer imposed by the enclosure. The final geometry of the rotor enclosure assembly is generated based on the research results and the design is integrated into the final machine prototype to be tested. / Thesis / Master of Applied Science (MASc) / Axial-flux permanent magnets (AFPM) machines are gaining the transportation electrification industy attention as a greener alternative to combustion engines in aircraft propulsion systems due to their high power and torque density. The intense endeavors of the current research to further improve AFPM machines power densities brings thermal design challenges to ensure the safe operation of the machine. Rotor permanent magnets failure due to demagnetization as a result of overheating can impose a great risk to the machine operation and safety. Accordingly, special attention should be paid to rotor thermal management. This research discusses the design process of an integrated rotor air cooling system for an AFPM machine designed for an electric aircraft. The machine mechanical and thermal design parameters are used to set an initial rotor design with different rotor cooling features based on literature findings. Rotor fan blades and air vents are selected as the main rotor cooling features for the design. Several design iterations are then made to fine-tune the rotor geometry targeting low operating temperature of the permanent magnets at a low cost of windage losses. The thermal performance of the different designs is assessed and compared to each other using conjugate heat transfer (CHT) computational fluid dynamics (CFD) analyses. Safe operating temperature of the magnets is achieved at an acceptable windage losses value with the final design, and it is selected for prototyping.