Design space exploration (DSE) is a tool used to evaluate and compare designs as part of the design selection process. While evaluating every possible design in a design space is infeasible, understanding design behavior and response throughout the design space may be accomplished by evaluating a subset of designs and interpolating between them using surrogate models. Surrogate modeling is a technique that uses low-cost calculations to approximate the outcome of more computationally expensive calculations or analyses, such as finite element analysis (FEA). While surrogates make quick predictions, accuracy is not guaranteed and must be considered. This research addressed the need to improve the accuracy of surrogate predictions in order to improve DSE of structural responses. This was accomplished by performing comparative analyses of linear and nonlinear dimensionality-reduction-based radial basis function (RBF) surrogate models for emulating various FEA nodal results. A total of four dimensionality reduction methods were investigated, namely principal component analysis (PCA), kernel principal component analysis (KPCA), isometric feature mapping (ISOMAP), and locally linear embedding (LLE). These methods were used in conjunction with surrogate modeling to predict nodal stresses and coordinates of a compressor blade. The research showed that using an ISOMAP-based dual-RBF surrogate model for predicting nodal stresses decreased the estimated mean error of the surrogate by 35.7% compared to PCA. Using nonlinear dimensionality-reduction-based surrogates did not reduce surrogate error for predicting nodal coordinates. A new metric, the manifold distance ratio (MDR), was introduced to measure the nonlinearity of the data manifolds. When applied to the stress and coordinate data, the stress space was found to be more nonlinear than the coordinate space for this application. The upfront training cost of the nonlinear dimensionality-reduction-based surrogates was larger than that of their linear counterparts but small enough to remain feasible. After training, all the dual-RBF surrogates were capable of making real-time predictions. This same process was repeated for a separate application involving the nodal displacements of mode shapes obtained from a FEA modal analysis. The modal assurance criterion (MAC) calculation was used to compare the predicted mode shapes, as well as their corresponding true mode shapes obtained from FEA, to a set of reference modes. The research showed that two nonlinear techniques, namely LLE and KPCA, resulted in lower surrogate error in the more complex design spaces. Using a RBF kernel, KPCA achieved the largest average reduction in error of 13.57%. The results also showed that surrogate error was greatly affected by mode shape reversal. Four different approaches of identifying reversed mode shapes were explored, all of which resulted in varying amounts of surrogate error. Together, the methods explored in this research were shown to decrease surrogate error when performing DSE of a turbomachine compressor blade. As surrogate accuracy increases, so does the ability to correctly make engineering decisions and judgements throughout the design process. Ultimately, this will help engineers design better turbomachines.

<p>The purpose of this research was to determine what components of a complex centrifugal  compression system inlet needed to be modelled to accurately predict the swirl and total pressure  distortions at the compressor face. Two computational models were developed. A full-fidelity case  where all the inlet geometry was modelled and a reduced model where a small portion of the inlet  was considered. Both the numerical cases were compared with experimental data from a research  compressor rig developed by Honeywell Aerospace. The test apparatus was designed with a  modular inlet system to develop swirl distortion patterns. The modular inlet system utilized  transposable baffles within the radial-to-axial section of the inlet and blockage plates of varying  sizes and geometries at the inlet to this section.  Discerning the dominant inlet component that dictates distortion behavior at the compressor  face would allow the reduced modelling of inlet components for compression systems and would  allow coupling with more tortuous systems. Furthermore, it would reduce the design iteration and  simulation time of the inlet systems. Several investigations utilizing a reduced model only  considering a radial-to-axial inlet are available in literature, but no comprehensive justification has  been presented as to the impact this has on the distortion behavior.   Experimental surveys of flow conditions just upstream of the inducer of the centrifugal  compressor were conducted at several operating conditions. The highest and lowest mass flow  rates of these operating points were simulated using ANSYS CFX 2020R1 for both the  computational models. Multiple inlet configurations were simulated to test the robustness of the  reduced model in comparison to the full fidelity. The numerical simulations highlighted  shortcomings of the instrumentation used to characterize the experimental flow field at the inducer,  particularly with respect to total pressure distortion. Furthermore, transient pressure data were  measured in experiment and indicated unsteady fluctuations in the inlet that would not be captured  by steady computational fluid dynamic simulations. These data matched locations of disagreement  with swirl distortion behavior at high mass flow rates. This suggested that transient vortex  movement occured at the aerodynamic interface plane in certain configurations.   The total pressure distortion metrics between the two models were remarkably comparable.  Furthermore, the simplified model accurately predicted the mixing losses associated with the  blockage plates at the inlet to the radial-to-axial inlet using a simple inlet extension. Swirl  18  distortion was dictated by the radial-to-axial inlet. The reduced model data trends were comparable  with experiment for both the baffle and blocker plate configurations. The swirl intensities for all  configurations were comparable between the two models. The reduced model swirl directivity  trends matched those of experiment. The most notable deviations between the full-fidelity model  and the reduced model were observed with swirl directivity numerics. </p>

In turbomachines, rotors and stators differ by the rotation of the former. Hence, half of each stage is directly influenced by rotation effects. The influence of rotation on the flow structure and its impact on the performance is studied through wall-resolving large Eddy simulations of a rotor with large relative tip gap size. The simulations are performed in a rotating frame with rotation accounted for through a Coriolis force term. In a first step, experimental results are used to provide validation. The main part of the study is the comparison of the results from two simulations, one representing the rotating configuration and one with the Coriolis force removed, without any other change. This setup allows a very clean assessment of the influence of rotation. The turbulence-resolving approach ensures that the turbulent flow features are well represented. The results show a significant impact of rotation on the secondary flow. In the tip region, the tip leakage vortex is enlarged and destabilized. Inside the tip gap, the flow is altered as well, with uniformization in the rotating case. At the blade midspan, no significant effects are observed on the suction side, while an earlier transition to turbulence is found on the pressure side. Near the hub, rotation effects are shown to reduce the corner separation significantly.

Automated solid modeling, integrated with computational fluid dynamics (CFD) and optimization of a 3D jet turbine engine has never been accomplished. This is due mainly to the computational power required, and the lack of associative parametric modeling tools and techniques necessary to adjust and optimize the design. As an example, the fluid domain of a simple household fan with three blades may contain 500,000 elements per blade passage. Therefore, a complete turbine engine that includes many stages, with sets of thirty or more blades each, will have hundreds of millions of elements. The fluid domains associated with each blade creates a nearly incomprehensible challenge. One method of organizing and passing geometric and non-geometric data is through the utilization of knowledge based engineering (KBE). The focus of this thesis will be the development of a set of techniques utilizing KBE principles to analyze an assembly which includes multiple fluid domains. This comprehensive system will be referred to as the Parametric Optimization Design System (PODS).

The flow and heat transfer within compressor rotor cavities of aero-engines is a conjugate problem. Depending on the operating conditions buoyancy forces, caused by radial temperature difference between the cold throughflow and the hotter shroud, can influence the amount of entrained air significantly. By this, the heat transfer depends on the radial temperature gradient of the cavity walls and in reverse the disk temperatures are dependent on the heat transfer. In this thesis, disk Nusselt numbers are calculated in reference to the air inlet temperature and in comparison to a modeled local air temperature inside the cavity. The local disk heat flux is determined from measured steady-state surface temperatures by solving the inverse heat transfer problem in an iterative procedure. The conduction equation is solved on a 2D mesh, using a validated finite element approach and the heat flux confidence intervals are calculated with a stratified Monte Carlo approach. An estimate for the amount of air entering into the cavity is calculated by a simplified heat balance. In addition to the thermal characterization of the cavity, the mass exchange of the air in the cavity with the axial flow in the annular gap and the swirl distribution of the air in the cavity are also investigated.:1 Einleitung 2 Grundlagen und Literaturübersicht 2.1 Modellsystem der rotierenden Kavitäten mit axialer Durchströmung 2.2 Ergebnisgrößen 2.3 Strömung in rotierenden Kavitäten 2.4 Wärmeübertragung in rotierenden Kavitäten 2.5 Fluidtemperatur in rotierenden Kavitäten 3 Experimenteller Aufbau 4 Messtechnik 4.1 Oberflächen- und Materialtemperaturen 4.2 Lufttemperaturen 4.3 Statischer Druck 4.4 Dreiloch-Drucksonden 5 Datenauswertung 5.1 Kernrotationsverhältnis 5.2 Wärmestromdichte und Nusseltzahl 5.2.1 Finite-Elemente Modell 5.2.2 inverses Wärmeleitungsproblem 5.2.3 Anpassungsmethode 5.2.4 Testfälle zur Validierung 5.2.5 Validierung Testfall 1 und 3 - ideale Kavitätenscheibe 5.2.6 Validierung Testfall 2 - Reproduzierbarkeit 5.2.7 Validierung Testfall 4 - lokales Ereignis 5.2.8 Bestimmung der Wärmestromdichte-Unsicherheit 5.2.9 Anwendung der Anpassungsmethode auf experimentelle Daten 5.2.10 Wahl der Randbedingungsfunktion 5.2.11 Wärmeübergangskoeffizient und Nusselt-Zahl 5.2.12 Zusammenfassung 5.3 Austauschmassenstrom 6 Experimentelle Ergebnisse 6.1 Dichteverteilung in der Kavität 6.2 Massenaustausch Kavität 6.3 Wärmeübertragung in der Kavität 6.3.1 Fallbeispiel 6.3.2 Einfluss der Drehfrequenz 6.3.3 Einfluss des Massenstromes 6.3.4 Einfluss des Auftriebsparameters 6.4 Wärmeübertragung im Ringspalt 6.5 Drall im Ringspalt und der Kavität 7 Zusammenfassung und Ausblick / Die Strömung und Wärmeübertragung in den Verdichterkavitäten von Flugtriebwerken ist ein konjugiertes Problem. Durch die radialen Temperaturunterschiede in der Kavität wird die Menge der in die Kavität strömenden Luft stark beeinflusst. Somit ist die Wärmeübertragung abhängig von den radialen Temperaturgradienten der Scheibenwände und umgekehrt ist die Scheibentemperatur abhängig von der Wärmeübertragung. Die Nusselt-Zahl in diesem System wurde aufgrund der schwierigen Zugänglichkeit in der Historie auf die eine Referenztemperatur vor der Kavität bezogen. Dies ist insofern problematisch, da hierdurch die thermischen Verhältnisse unterschätzt werden können. In dieser Arbeit wird ein neuer Ansatz zu Berechnung der Nusselt-Zahl mithilfe einer modellierten lokalen Lufttemperatur innerhalb der Kavität verwendet. Die lokale Wärmestromdichte auf der Scheibenoberfläche wird mithilfe eines validierten zweidimensionalen rotationssymmetrischen Finite-Element Modells auf der Grundlage von gemessenen Oberflächentemperaturen berechnet. Dies stellt ein inverses Wärmeleitungsproblem dar, welches mithilfe einer Anpassungsmethode gelöst wurde. Die Auswirkung der Messunsicherheit der Temperaturmessung auf die berechnete Wärmestromdichte wird durch eine geschichtete Monte-Carlo-Simulation, nach dem Ansatz der LHC-Methode, untersucht. Neben der thermischen Charakterisierung der Kavität wird zudem der Massenaustausch der Luft in der Kavität mit der axialen Durchströmung im Ringspalt sowie die Drallverteilung der Luft in der Kavität untersucht.:1 Einleitung 2 Grundlagen und Literaturübersicht 2.1 Modellsystem der rotierenden Kavitäten mit axialer Durchströmung 2.2 Ergebnisgrößen 2.3 Strömung in rotierenden Kavitäten 2.4 Wärmeübertragung in rotierenden Kavitäten 2.5 Fluidtemperatur in rotierenden Kavitäten 3 Experimenteller Aufbau 4 Messtechnik 4.1 Oberflächen- und Materialtemperaturen 4.2 Lufttemperaturen 4.3 Statischer Druck 4.4 Dreiloch-Drucksonden 5 Datenauswertung 5.1 Kernrotationsverhältnis 5.2 Wärmestromdichte und Nusseltzahl 5.2.1 Finite-Elemente Modell 5.2.2 inverses Wärmeleitungsproblem 5.2.3 Anpassungsmethode 5.2.4 Testfälle zur Validierung 5.2.5 Validierung Testfall 1 und 3 - ideale Kavitätenscheibe 5.2.6 Validierung Testfall 2 - Reproduzierbarkeit 5.2.7 Validierung Testfall 4 - lokales Ereignis 5.2.8 Bestimmung der Wärmestromdichte-Unsicherheit 5.2.9 Anwendung der Anpassungsmethode auf experimentelle Daten 5.2.10 Wahl der Randbedingungsfunktion 5.2.11 Wärmeübergangskoeffizient und Nusselt-Zahl 5.2.12 Zusammenfassung 5.3 Austauschmassenstrom 6 Experimentelle Ergebnisse 6.1 Dichteverteilung in der Kavität 6.2 Massenaustausch Kavität 6.3 Wärmeübertragung in der Kavität 6.3.1 Fallbeispiel 6.3.2 Einfluss der Drehfrequenz 6.3.3 Einfluss des Massenstromes 6.3.4 Einfluss des Auftriebsparameters 6.4 Wärmeübertragung im Ringspalt 6.5 Drall im Ringspalt und der Kavität 7 Zusammenfassung und Ausblick

<p dir="ltr">As aircraft engine manufacturers continue to embark on their pursuit of higher-efficiency, lower-emissions gas turbines, a prevailing theme in the industry has been the increase of the engine bypass ratio. As the optimization space for engine bypass ratios trends towards smaller and smaller engine core sizes, the feasibility of centrifugal compressors as the final stage in an axial-centrifugal compressor becomes apparent due to their performance advantages at smaller scales.</p><p dir="ltr">This study performed an investigation into the aerodynamics of a stationary diffusion system intended for use with a final stage aeroengine centrifugal compressor using experimental and numerical techniques. Experimental work was performed at the Purdue Compressor Research Lab at Purdue University’s Maurice J. Zucrow Laboratories. Data were collected from several iterations of rapidly prototyped, additively manufactured diffuser and deswirl parts with internal instrumentation features. Furthermore, computational work on the stage was conducted using the Ansys Turbosystem.</p><p dir="ltr">The goal of this research is to identify trends in stationary diffusion system designs and the geometric features that cause them. Furthermore, the ability of steady computational fluid dynamics methods to predict these changes was evaluated using two turbulence models to produce a simulation of the compressor flow field. When used in conjunction with one another, the efficient use of computational methods to identify an optimal design and rapid prototyping to validate it leads to the determination of the best diffusion system design at a lower cost and time requirement than what is otherwise currently possible.</p><p dir="ltr">The different geometries which were tested identified the negative effects of spanwise vane contouring on the diffuser performance and the ability of endwall divergence to augment the pressure recovery performance of a design at the expense of increased losses. A full understanding of the effect of each design parameter is enabled by iterative inclusion or exclusion of certain design parameters. Furthermore, the use of computational fluid dynamics showed that the BSLEARSM turbulence model performs reasonably well in predicting the build-to-build performance trends. However, neither the BSLEARSM nor the SST turbulence model were able to accurately identify performance trends for the deswirl. For this reason, additional work is warranted to identify an optimal set of parameters to characterize the high axial and meridional turning present in this component.</p>

With hydrogen playing a major role for reaching net zero emissions, the main challenge will be the integration of the energy carrier. This includes solutions for storage, production and transportation of the gas. Alternatives for hydrogen transportation could include either train, truck or boat. However, the current most economical and promising technology is pipeline transmission, especially in northern Sweden, with new green projects suchas H2 Green Steel and HYBRIT. They will create a market that needs a hydrogen infrastructure, which hydrogen pipelines could provide. This thesis will cover a techno-economic evaluation of hydrogen piping, involving material, compressor technology and pipeline dimensions. Hydrogen is briefy covered in its main production, applications and transportation options in the beginning of the thesis. This will ultimately converge into a in-depth analysis of hydrogen piping. This analysis includes alternatives for compressors, materials for pipes and main technical challenges. The gathered information concluded that hydrogen transport will most likely use either reciprocating or centrifugal compressors. Centrifugal compressors have the advantage of managing high gas flows, and the reciprocating compressors are mature and have a high capacity for pressure. For materials, embrittlement is the main challenge when transporting hydrogen gas, and standard ASME B31.12 provides current directions for hydrogen piping. A yield strength of 30% is required in the material, to compensate for hydrogen’s attributes. Generally the higher the strength of the material, the higher the risk of embrittlement and pipe damage. Careful selection has to be made in termsof micro structure, strength and coating to minimise leakage. To realise how hydrogen infrastructure could be constructed, three scenarios where created. These scenarios were based on assumptions and article values to best illustrate future hydrogen transportation. Main scenario settings include a pressure ratio of Pratio &lt; 1.5, and length between compressors of maximum 135km. These assumptions help keep fnal results within a reasonable dimensions. The results from the initial calculations yielded an optimal diameter of 0.35m for Scenario A. At this diameter, an operational pressure of 85 bar and one compressor with 40 MWe optimally transported the gas. With compressor cost decreasing as pipe cost increases, a trade of in price is found at the lowest cost. For a higher diameter, optimising fow resulted in a lower OP, and a lower power consumption for compressors. Scenario B resulted in a diameter of 0.3 m, an OP of 150 bar, four compressors for a total of 405 km pipes. The lowest possible diameter yielded the lowest cost. If other factors are to be considered, a larger diameter could be used for a lower OP, thus reducing stress on material and compressors. Comparison with electricity (Scenario C) mainly resulted in a higher CAPEX for Hydrogen infrastructure, but a lower transmission cost per MWe per km. This concludes that hydrogen piping is better suited for carrying the energy, due to the large decrease in transfer cost. Finally, for material selection low strength carbonsteels are currently the best alternative for transportation of hydrogen. This is due to its commercial use, good composition, high strength and availability.

Um eine homogene und ausreichende Versorgung des Brennstoffzellen (BZ)-Stapels zu gewährleisten, wird in einem Brennstoffzellen-Fahrzeug dem Stapel mehr Wasserstoff zugeführt, als für die Reaktion benötigt wird. Daher wird nicht verbrauchter Wasserstoff mit einer Strahlpumpe oder einem Rezirkulationsgebläse zum Anodeneingang des BZ-Stapels rezirkuliert. Aufgrund der Diffusion durch die Membran enthält das Anodenabgas neben dem Wasserstoff auch andere Bestandteile wie z.B. Stickstoff. Die Anreicherung des Stickstoffes im Anodenkreislauf führt zu einer ungleichmäßigen Stromdichteverteilung. Um dem entgegenzuwirken, wird in das System ein Spülventil eingebaut, das periodisch Gas ablässt um Stickstoff aus dem Anodenkreislauf abzuführen. Dabei lässt sich ein Wasser­stoffverbrauch nicht vermeiden. Diese Arbeit zielt darauf ab, die Rentabilität des Brennstoffzellensystems im automobilen Einsatz durch Reduzierung des Wasserstoffverbrauchs zu steigern. Hierfür wird die Verwendung eines elektrochemischen Wasserstoffkompressors (EHC) zur Wasserstoffumwälzung vorgeschlagen. Ein EHC ist eine innovative H2-Fördertechnologie, wobei der Wasserstoff gleichzeitig verdichtet und gereinigt werden kann. Im Vergleich zu mechanischen Kompressoren sind elektrochemische Wasserstoffkompressoren aufgrund der nahezu isothermen Bedingungen sehr effizient. Darüber hinaus können Wasserstoffkompressoren aufgrund ihres modularen Aufbaus sehr flexibel und kompakt gebaut werden.:1. EINLEITUNG 2. STAND DER TECHNIK 3. GRUNDLAGEN DER BRENNSTOFFZELLEN 4. TRANSPORTVORGÄNGE IN DER BRENNSTOFFZELLE 5. ELEKTROCHEMISCHER WASSERSTOFFKOMPRESSOR IM REZIRKULATIONSKREISLAUF 6. SIMULATION 7. EXPERIMENTELLE UNTERSUCHUNGEN 8. EINSATZ DES ELEKTROCHEMISCHEN WASSERSTOFFKOMPRESSORS IM BRENNSTOFFZELLENFAHRZEUG 9. ZUSAMMENFASSUNG 10. AUSBLICK / In order to ensure a homogeneous and sufficient supply of the fuel cell (FC) stack, more hydrogen is supplied to the stack in a fuel cell vehicle than required for the reaction. Therefore, unused hydrogen is recirculated to the anode inlet of the FC stack with an ejector or recirculation fan. Due to the diffusion through the membrane, the anode exhaust gas contains not only hydrogen but also other components such as nitrogen. The accumulation of nitrogen in the anode circuit leads to an uneven current density distribution. To counteract this, a purge valve is built into the system that periodically vents gas to purge nitrogen from the anode circuit. Hydrogen consumption cannot be avoided here. This work aims to increase the profitability of the fuel cell system in automotive application by reducing hydrogen consumption. For this purpose, the use of an electrochemical hydrogen compressor (EHC) for hydrogen circulation is proposed. An EHC is an innovative H2 delivery technology, whereby the hydrogen can be compressed and cleaned at the same time. Compared to mechanical compressors, electrochemical hydrogen compressors are very efficient due to the almost isothermal conditions. In addition, hydrogen compressors can be built very flexibly and compactly due to their modular design.:1. EINLEITUNG 2. STAND DER TECHNIK 3. GRUNDLAGEN DER BRENNSTOFFZELLEN 4. TRANSPORTVORGÄNGE IN DER BRENNSTOFFZELLE 5. ELEKTROCHEMISCHER WASSERSTOFFKOMPRESSOR IM REZIRKULATIONSKREISLAUF 6. SIMULATION 7. EXPERIMENTELLE UNTERSUCHUNGEN 8. EINSATZ DES ELEKTROCHEMISCHEN WASSERSTOFFKOMPRESSORS IM BRENNSTOFFZELLENFAHRZEUG 9. ZUSAMMENFASSUNG 10. AUSBLICK

[ES] En un contexto de creciente preocupación por el calentamiento global y de políticas energéticas internacionales, en el cual los sistemas de climatización de los edificios suponen una parte importante del consumo energético global, los sistemas de bombas de calor son considerados como opciones muy interesantes debido a su alta eficiencia y por ser fuentes de energía renovables. En este sentido, una caracterización precisa de estos equipos es de vital importancia con el objetivo de mejorar su diseño y, en aquellos casos dónde este tipo de unidades se integren como parte de sistemas más complejos, implementar estrategias de control eficientes. En este contexto, esta tesis doctoral se centra en el modelado de bombas de calor con el fin de obtener modelos que permitan conocer con precisión el desempeño global de estas unidades en todo el rango de trabajo. En la primera parte del trabajo, se han realizado numerosos ensayos experimentales utilizando un nuevo prototipo de bomba de calor dual, obtenidos dentro del marco de trabajo del proyecto europeo GEOTeCH. Debido a la tipología hibrida de esta unidad, los resultados experimentales obtenidos incluyen datos de desempeño para las principales tecnologías de bombas de calor: las bombas de calor aerotérmicas y geotérmicas. Haciendo uso de toda esta información experimental, esta primera parte del trabajo se centra en obtener modelos polinómicos para la predicción del consumo eléctrico y las capacidades de calefacción y refrigeración en función de las variables externas a la unidad. Dichas variables son fáciles de obtener y suelen medirse en instalaciones reales. Por tanto, estos modelos caracterizan a la bomba de calor como un único componente, simplificando su implementación en modelos globales de sistemas más complejos donde se instalan estas unidades. Además, seleccionado un enfoque empírico para el modelado, en esta parte también se analizan algunos aspectos relevantes, como los términos a incluir en el polinomio, o cómo conformar las matrices experimentales de ensayo necesarias, es decir, cuántos puntos experimentales realizar y dónde situarlos en el rango de operación. Por último, la segunda parte de la tesis doctoral está dedicada a modelar uno de los componentes principales en estas unidades, el compresor. En este caso, el desarrollo de una extensa base de datos que incluye numerosos ensayos calorimétricos de las dos principales tecnologías de compresores, pistón y scroll, ha permitido el análisis detallado de las superficies de respuesta del consumo eléctrico y el caudal másico de refrigerante en función de las temperaturas de evaporación y condensación. A partir de esta información y siguiendo un enfoque similar al utilizado previamente, en esta segunda parte se revisan los modelos incluidos en la norma actual de caracterización de compresores, el estándar AHRI 540 (2020), para comprobar si son adecuados o si, por el contrario, debemos utilizar otro tipo de expresiones polinómicas. También se analizan en profundidad cuestiones críticas como el número de puntos necesarios para caracterizar cada tecnología de compresor, dónde situarlos en el dominio experimental, cómo evitar un posible sobreajuste del modelo minimizando problemas de extrapolación o interpolación, o cómo extrapolar los resultados para predecir con otros refrigerantes u otras condiciones de aspiración. / [CA] En un context de creixent preocupació per l'escalfament global i de polítiques energètiques internacionals, en el qual els sistemes de climatització dels edificis suposen una part important del consum energètic global, els sistemes de bombes de calor són considerats com a opcions molt interessants a causa de la seva alta eficiència i perquè són fonts d'energia renovables. En aquest sentit, una caracterització precisa d'aquests equips és de vital importància amb l'objectiu de millorar el seu disseny i, en aquells casos on aquest tipus d'unitats s'integren com a part de sistemes més complexos, implementar estratègies de control eficients. En aquest context, aquesta tesi doctoral se centra en el modelat de bombes de calor per obtenir models que permitisquen conèixer amb precisió el funcionament d'aquestes unitats a tot el rang de treball. A la primera part del treball, s'han realitzat nombrosos assajos experimentals utilitzant un nou prototip de bomba de calor dual, obtinguts dins del marc de treball del projecte europeu GEOTeCH. A causa de la tipologia hibrida d'aquesta unitat, els resultats experimentals obtinguts inclouen dades de funcionament per a les principals tecnologies de bombes de calor: les bombes de calor aerotèrmiques i geotèrmiques. Fent ús de tota aquesta informació experimental, aquesta primera part del treball se centra a obtenir models polinòmics per a la predicció del consum elèctric i les capacitats de calefacció i refrigeració en funció de les variables externes a la unitat. Aquestes variables són fàcils d'obtenir i se solen mesurar en instal·lacions reals. Per tant, aquests models caracteritzen la bomba de calor com un únic component, simplificant-ne la implementació en models globals de sistemes més complexos on s'instal·len aquestes unitats. A més, seleccionat un enfocament empíric per al modelatge, en aquesta part també s'analitzen alguns aspectes rellevants, com els termes a incloure al polinomi, o cóm conformar les matrius experimentals d'assaig necessàries, és a dir, quants punts experimentals realitzar i on situar-los al rang d'operació. Per acabar, la segona part de la tesi doctoral està dedicada al modelat d'un dels components principals d'aquestes unitats, el compressor. En aquest cas, el desenvolupament d'una extensa base de dades que inclou nombrosos assajos calorimètrics de les dues principals tecnologies de compressors, pistó i scroll, ha permès l'anàlisi detallat de les superfícies de resposta del consum elèctric i el cabal màssic de refrigerant segons les temperatures d'evaporació i de condensació. A partir d'aquesta informació i seguint un enfocament similar a l'utilitzat prèviament, en aquesta segona part es revisen els models inclosos a la norma actual de caracterització de compressors, l'estàndard AHRI 540 (2020), per comprovar si són adequats o si, per contra, cal utilitzar un altre tipus d'expressions polinòmiques. També s'analitzen en profunditat qüestions crítiques com el nombre de punts necessaris per caracteritzar cada tecnologia de compressor, on situar-los al domini experimental, cóm evitar un possible sobreajust del model minimitzant problemes d'extrapolació o interpolació, o cóm extrapolar els resultats per predir amb altres refrigerants o altres condicions d'aspiració. / [EN] In a context of global warming concerns and global energy policies, in which heating and cooling systems in buildings account for a significant amount of the global energy consumption, heat pump systems are widely considered as a really interesting option for enabling high efficiency and also for being renewable energy sources. In this sense, an accurate characterization of these units is of vital importance to improve their design and implement efficient control strategies, when the unit is integrated in more complex systems. Against this background, this PhD thesis focuses on heat pump modelling in order to create map-based models able to accurately characterize the global performance of these units for the entire working range. In the first part of this work, many experimental tests have been obtained for a new Dual Source Heat Pump prototype tested in the framework of the European project GEOTeCH. Due to the dual typology, the experimental results include performance data for the two main heat pump technologies: Air Source Heat Pumps and Ground Source Heat Pumps. By using all this experimental information, this first part focuses on obtaining empirical polynomial models capable of accurately predicting energy consumption and heating and cooling capacities as a function of external variables. Such variables are easy to measure and are usually recorded in real installations. Therefore, these models characterize the heat pump as a single component, simplifying its implementation in global models of more complex systems where these units are installed. Furthermore, selecting the empirical model approach, this part also includes some critical aspects, such as how to obtain the best polynomial expression, or how to perform the required experimental test matrices, i.e., how many tests should be conducted and where in the operating range. Finally, the second part of this PhD thesis is dedicated to modelling one of the main components of these units, the compressor. In this case, the development of an extensive database including numerous calorimetric tests on the two main compressor technologies, reciprocating and scroll compressors, has allowed the detailed analysis of the response surfaces of their performance parameters, i.e., the energy consumption and mass flow rate as a function of the evaporation and condensation temperatures. Using this information, and following an approach similar to that used in the first part, this second part reviews the models included in the current compressor characterization standard, the AHRI 540 (2020), in order to check whether they are appropriate or, on the contrary, whether we should use of other types of polynomial expression. Critical issues such as the number of points needed to characterize each compressor technology, where to place them in the experimental domain, how to prevent possible overfitting in the model adjustment to minimize extrapolation or interpolation problems, or how to extrapolate results for predicting other refrigerant or suction conditions, are discussed in depth. / I would like to acknowledge the financial support that has made this PhD thesis possible. The doctoral fellowship FPU15/03476 was founded by “Ministerio de Educación, Cultura y deporte” inside the program “Formación de Profesorado Universitario”, and the GEOTeCH project (No 656889) founded by the European Union under the “Horizon 2020 Framework Programme for European Research and Technological Development” / Marchante Avellaneda, J. (2023). Study of Response Surface Models for the characterization of the performance in Refrigeration Equipments and Heat Pumps [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/192653

Tesis por compendio / [ES] La tecnología de bombas de calor se ha vuelto estratégica en Europa, está extendiéndose rápidamente y se planea que reemplace las calderas de gas en un futuro cercano. Sin embargo, aún enfrenta desafíos, como encontrar refrige-rantes nuevos viables y altamente eficientes, y mejorar aún más el rendimiento del sistema. Para abordar este último problema, han surgido las bombas de calor de velocidad variable que prometen reducir el consumo anual e incremen-tar el confort adaptando la potencia suministrada a las necesidades cambiantes. Esta tecnología se está implementando ya, pero carece de una metodología estandarizada para diseñar y seleccionar sus componentes. Esta tesis tiene como objetivo establecer pautas de diseño generales para la selección y diseño de componentes de bombas de calor de velocidad variable, y ofrecer información valiosa que se pueda traducir en herramientas para asistir en la simulación, diseño, selección y detección de fallas en estos dispositivos. El contenido del estudio se puede dividir en tres áreas temáticas: En una primera parte, se estudian los compresores de velocidad variable. El compresor es el primer componente que se selecciona en una bomba de calor, modula la capacidad y es el principal consumidor de energía. Sin embargo, no existen metodologías bien establecidas para modelar su comportamiento. En esta parte, se realizan ensayos de caracterización de compresores de velocidad variable y sus inversores para comprender su comportamiento y proporcionar correlaciones compactas para modelar su rendimiento. En la segunda parte, se propone una metodología para dimensionar los intercambiadores de calor en bombas de calor de velocidad variable. Nor-malmente, se diseñan para una potencia fija y temperaturas de trabajo constan-tes, sin embargo, en las bombas de velocidad variable, la capacidad y las tempe-raturas de trabajo fluctúan significativamente con el tiempo. En esta parte, se estudia la evolución del rendimiento de los intercambiadores de calor con la capacidad (velocidad del compresor) y se propone una metodología de selec-ción/dimensionamiento que considera la evolución de la capacidad requerida y de las condiciones climáticas externas a lo largo del año. Por último, se evalúa la circulación del aceite en las bombas de calor de velocidad variable. Gestionar la lubricación en los compresores de velocidad variable es un problema típico ya que, para tener suficiente lubricación a bajas velocidades, el compresor termina bombeando un exceso de aceite a altas velo-cidades. En esta parte se estudia la evolución de las tasas de circulación de acei-te con la velocidad y se analiza teóricamente su efecto en el rendimiento de la bomba de calor. / [CA] La tecnologia de les bombes de calor s'ha tornat estratègica a Europa, s'està estenent ràpidament i es preveu que substituïsca les calderes de gas en un futur pròxim. Tanmateix, encara s'enfronta a desafiaments com trobar refrigerants nous viables i altament eficients, i millorar encara més el rendiment del sistema. Per abordar aquest darrer problema, han sorgit les bombes de calor de velocitat variable que prometen reduir el consum anual i incrementar el confort adaptant la potència subministrada a les necessitats variables. Aquesta tecnologia ja s'es-tà implementant, però manca d'una metodologia estandarditzada per dissenyar i seleccionar els seus components. Aquesta tesi té com a objectiu establir pautes de disseny generals per a la se-lecció i disseny de components de bombes de calor de velocitat variable, i oferir informació valuosa que es pugui traduir en eines per ajudar en la simulació, disseny, selecció i detecció de fallades d'aquests dispositius. El contingut de l'estudi es pot dividir en tres àrees temàtiques: En una primera part, s'estudien els compressors de velocitat variable. El compressor és el primer component seleccionat d'una bomba de calor, modula la capacitat i és el principal consumidor d'energia. Tanmateix, no hi ha metodo-logies ben establides per modelar el seu comportament. En aquesta part, es realitzen assajos de caracterització de compressors de velocitat variable i els seus inversors per comprendre el seu comportament i proporcionar correlaci-ons compactes per modelar el seu rendiment. En la segona part, es proposa una metodologia per dimensionar els inter-canviadors de calor en bombes de calor de velocitat variable. Normalment, es dissenyen per a una potència fixa i temperatures de treball constants, no obs-tant això, en les bombes de velocitat variable, la capacitat i les temperatures de treball fluctuen significativament amb el temps. En aquesta part, s'estudia l'evo-lució del rendiment dels intercanviadors de calor amb la capacitat (velocitat del compressor) i es suggereix una metodologia de selecció/dimensionament que considera l'evolució de les càrregues i de les condicions climàtiques externes al llarg de l'any. Finalment, s'avalua la circulació de l'oli a les bombes de calor de velocitat variable. Gestionar la lubricació als compressors de velocitat variable és un pro-blema típic, ja que per tenir suficient lubricació a baixes velocitats, el compres-sor acaba bombejant un excés d'oli a altes velocitats. En aquesta part s'estudia l'evolució de les taxes de circulació d'oli amb la velocitat i s'analitza teòricament el seu efecte en el rendiment de la bomba de calor. / [EN] Heat pump technology has become strategic in Europe, it is rapidly spread-ing, and it is planned to replace gas boilers in the near future. However, they still have challenges to solve, such as finding new viable and highly efficient refriger-ants and further increasing their system performance. For this latter issue, vari-able-speed heat pumps arise, which claim to decrease annual consumption and increase comfort by adapting the delivered capacity to the changing loads. This technology is being implemented but lacks a standardized methodology to de-sign and select its components. This thesis aims to establish comprehensive design guidelines for selecting and designing variable-speed heat pump components and give insights that can translate into valuable information and tools for engineers to assist them in the pump simulation, design, selection and fault detection. The content of the study can be divided into three thematic areas: In the first part, variable-speed compressors are studied. The compressor is the first selected heat pump component; it modulates the capacity and is the primary energy consumer. However, there are no well-established methodolo-gies to model their behavior. In this part, extensive testing of variable-speed compressors and their inverters was carried out to understand their behavior and to provide compact correlations to model their performance. The second part proposes a methodology to size heat exchangers for variable-speed heat pumps. Typically, they are designed for a fixed capacity and constant working temperatures. However, the capacity and working tempera-tures fluctuate significantly overtime in variable-speed pumps. In this part, the performance evolution of heat exchangers with capacity is studied, and a meth-odological selection/sizing technique is proposed that considers the evolution of external climatic conditions and loads over the year. Lastly, the oil circulation in variable-speed heat pumps is assessed. Man-aging lubrication in variable-speed compressors is a typical issue, as a design valid for sufficient lubrication at low compressor speeds will end up pumping excess oil at high speeds. In this final part, the evolution of oil circulation rates with speed is studied, and its effect on heat pump performance is theoretically analyzed. / I am indebted to the Spanish and European governments for their financial support with the grant PRE2018-083535, which made this research possible. Their commitment to academic excellence and research advancement has been crucial in successfully completing this thesis. / Ossorio Santiago, RJ. (2024). Modelling of Heat Pumps Working with Variable-Speed Compressors [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/203104 / Compendio