Doctoral School

Reading date: 03/07/2024

• LEÓN OVIEDO, TAMARA ELIZABETH: Application of bipolar electrodialysis to the generation of alkaline and acidic solutions from concentrated seawater brines from saltworks
  
  Author: LEÓN OVIEDO, TAMARA ELIZABETH
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CHEMICAL PROCESS ENGINEERING
  Department: Department of Chemical Engineering (EQ)
  Mode: Article-based thesis
  Deposit date: 08/05/2024
  Reading date: 03/07/2024
  Reading time: 12:30
  Reading place: Defensa pública: EEBE (Escola d'Enginyeria Barcelona Est), Sala Polivalent de l'Edifici A, planta baixa, Campus Diagonal-Besòs
  Thesis director: JOFRE CRUANYES, LLUÍS | CORTINA PALLAS, JOSE LUIS
  Committee:
       PRESIDENT: GIBERT AGULLO, ORIOL
       SECRETARI: LICON BERNAL, EDXON EDUARDO
       VOCAL: PAWLOWSKI, SYLWIN
  Thesis abstract: Brines should be treated as waste and disposed accordingly. Nevertheless, brines are typically discharged back into water bodies, thereby affecting the marine environment, soil quality, and groundwater. However, the potential benefits and applications of these brines are worth further investigation. In addition to the high concentration of salt (NaCl), some important elements, such as Critical Raw Materials (e.g. Li, Sr, Ga, Ge) can be found. This has increased interest in using brines as an alternative source for recovering strategic elements, the large content of strong electrolytes (e.g., NaCl and Na2SO4) has opened the possibility of using brines as a source to produce chemical commodities (e.g., strong acid and bases). Specifically , owing to the highly saline nature of brines, they are well-suited for use in electro-membrane processes such as Electrodialysis with Bipolar Membranes (EDBM). EDBM allows for the generation of chemicals from their corresponding salts; the protons and hydroxide ions generated in the bipolar membranes generate, together with the cations and anions removed from the salts , acidic and alkaline solutions, respectively. However, EDBM technology still needs to be improved to reduce the high energy expenses and boost the concentration of products. EDBM remains a non-scale-up technology that requires more research and study to be able to compete with well-established technologies to produce acidic/alkali solutions from brines, including chlor-alkali technology.There fore, it is necessary to investigate mass transfer processes in complex systems such as those involving EDBM with solutions of high salt composition. Additionally, there are a limited number of bipolar membranes and limited information on the behaviour of the membranes in concentrated solutions .In this context, the present thesis aims to carry out an extensive evaluation of the production of acidic and alkaline solutions from brines using EDBM. This involved moving from theoretical proposals based on Computational Fluidic Dynamics (CFO) models to a comprehensive experimental campaign using synthetic brines, in which numerous operational parameters were examined. Two CFO models were introduced using 2-0 geometry, one was time-dependent and the other was not; both aimed to study the mass transpo rt, potential distribution, and water splitting phenomena.The results from both theoretical studies and experiments offered valuable insights into how to enhance the performance of EDBM and make them more competitive with current popular technologies, ultimately leading to the growth and expansion of this technology.
  

• LOPEZ BLANCO, SAMUEL: Current-controlled flash sintering for ultra-fine control of the microstructure of lead-free ferroelectric perovskites.
  
  Author: LOPEZ BLANCO, SAMUEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTATIONAL AND APPLIED PHYSICS
  Department: Department of Physics (FIS)
  Mode: Article-based thesis
  Deposit date: 09/05/2024
  Reading date: 03/07/2024
  Reading time: 11:00
  Reading place: Defensa pública a l'Aula 002, Edifici C4, Jordi Girona 1- 3, Campus Nord, Barcelona
  Thesis director: GARCIA GARCIA, JOSE EDUARDO | OCHOA GUERRERO, DIEGO ALEJANDRO
  Committee:
       PRESIDENT: PEREZ MAQUEDA, LUIS ALLAN
       SECRETARI: JIMENEZ PIQUÉ, EMILIO
       VOCAL: BELTRAN MIR, HECTOR
  Thesis abstract: The global environmental crisis imposes the need to perform changes in modern industrial manufacturing systems. In the context of ferroelectric ceramics, it is required to move towards energy efficient sintering methods and eco-friendly materials. Flash sintering emerges as a potential alternative owing to its rapid densification and reduced energy consumption. This technique has been investigated in depth since its discovery in 2010 but it is yet to be fully understood. In this thesis, flash sintering is employed in order to obtain dense environmentally-friendly ferroelectric ceramics. A proper control of the sintering parameters is used to achieve highly controlled microstructures and enhanced functional properties for specific applications. The flash technique is then taken a step further by exploring the current control mode, which proves to grant further dominion over the microstructure. In this work a comprehensive study of sintering parameters in multiple ferroelectric materials, from well-known compositions to complex perovskite-structured systems, is performed in order to accomplish fine microstructure tailoring. The ultimate goal was to demonstrate that flash sintering is an efficient method of obtaining ferroelectric polycrystals with high quality properties that can rival their conventional counterparts while overcoming the aforementioned environmental concerns.
  

• ROIG MAYORAL, ORIOL: Paràmetres definitoris de la façana ventilada i la seva influència sobre el funcionament energètic del sistema
  
  Author: ROIG MAYORAL, ORIOL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ARCHITECTURE, ENERGY AND ENVIRONMENT
  Department: Department of Architectural Technology (TA)
  Mode: Normal
  Deposit date: 05/06/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: PARDAL MARCH, CRISTINA | ISALGUE BUXEDA, ANTONIO
  Committee:
       PRESIDENT: BASTERRA OTERO, LUIS ALFONSO
       SECRETARI: COLL LOPEZ, JAIME
       VOCAL: LUNA NAVARRO, ALESSANDRA
  Thesis abstract: The negative repercussions of climate change and global warming are becoming more and more evident. We need to find strategies to reduce our environmental impact and at the same time adapt to these new conditions. The ventilated facade is a constructive system that can be useful to avoid overheating of buildings and improve the comfort of users.The commonly used energy calculation systems, incorporated in the regulations, do not take into account many of the characteristics of ventilated facades. Some of their parameters, or their combination, can affect the ventilation of the cavity and the energy performance of the enclosure. Therefore, these systems may not be sufficient to argue for decision-making about aspects involved in the energy performance of the facade as a whole.This thesis hypothesizes that the simplified calculation systems do not consider parameters of the ventilated facade that can greatly influence the energy performance of the envelope. To demonstrate this, an algorithm is developed. It takes into account the defining parameters of the ventilated façade and related variables.It is an algorithm that takes into account the characteristics of the facade, the building as a whole, and the environment, along with the weather conditions. With this information, it relates the energy flows based on their transfer equations. Transient conduction is considered following the explicit method, with surface finite elements. The airflow through the openings and inside the ventilated cavity depends on the wind pressure and the buoyancy, while the dynamic and frictional losses are conditioned by the geometry and characteristics of the channel.This model is incorporated into a calculation tool programmed in Python and is validated by comparing its results with temperatures measured in five buildings. These cases were chosen to represent different situations, and especially uncertain aspects such as airflow and how it is conditioned by the geometry of the cavity and its interruptions and discontinuities.The validation of the tool is carried out at two levels: graphical and numerical. The first allows us to obtain an image of the model operation and to be able to analyse in which situations it best approximates reality, while the second allows us to obtain objective statistical values. The tool is validated with a minimum coefficient of determination (R²) of 0.87 for each of the periods, which indicates a very good correlation.Once validated, the tool is used to analyse how some parameters influence the energy performance of the envelope. The chosen parameters are the colour of the outer surface, the dimensions of the ventilation channel and the material of the outer sheet. It is verified that these parameters imply a variation of the average outer surface temperature of the inner sheet of between 0.64 °C and 7.97 °C, which proves the hypothesis.In the future, it is proposed that the influence of various parameters in different climates and situations be studied in depth so that this information can be extrapolated and used as a design guide. In this way, architects could reasonably estimate how their technical and design proposals influence the energy performance of the enclosure. By being able to adapt the facade to the environmental, climatic, building or system conditions, a lower energy demand for climate control could be achieved. In addition, this knowledge can be used to implement innovative proposals that can improve the effectiveness and efficiency of the ventilated façade. Finally, it can also be applied to try to influence the regulations and their simplified calculation systems, with the aim that they reflect the actual energy performance of the ventilated facade more accurately.
  

Reading date: 04/07/2024

• NÚÑEZ CORBACHO, MARC: Aerodynamic shape optimization under uncertainties using embedded methods and adjoint techniques
  
  Author: NÚÑEZ CORBACHO, MARC
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CIVIL ENGINEERING
  Department: Barcelona School of Civil Engineering (ETSECCPB)
  Mode: Normal
  Deposit date: 09/04/2024
  Reading date: 04/07/2024
  Reading time: 12:00
  Reading place: ETSECCPB, C/Jordi Girona 1-3, edifici C1, sala 002, Campus Nord, Barcelona.
  Thesis director: ROSSI BERNECOLI, RICCARDO | BAIGES AZNAR, JOAN
  Committee:
       PRESIDENT: LEHMKUHL BARBA, ORIOL
       SECRETARI: MARTINEZ FRUTOS, JESUS
       VOCAL NO PRESENCIAL: RICCHIUTO, MARIO
  Thesis abstract: This thesis develops a framework to perform shape optimization under uncertainties for a body under the action of aerodynamic forces. The solution of the flow is performed with finite elements using the full potential equation with an embedded approach, where the object of study is defined implicitly with a level set function. The optimization problem is solved by combining different software packages to perform the solution of the flow, advance in the optimization loop and perform uncertainty quantification. The first contribution of the thesis is the development of a full embedded approach for the solution of the full potential equation. Due to the inviscid hypothesis of potential solvers, these require the definition of a gap in the computational mesh in order to generate lift, known as the wake. Based on previous works where the wake is defined implicitly with an embedded approach, this work also considers the geometry as an embedded body. Mesh refinement and numerical terms are employed to improve the definition of the geometry in the mesh and ensure the definition of the Kutta condition. The solver is validated for two and three dimensions for subsonic and transonic flows with different reference data. Another contribution of the thesis is the development of the adjoint analysis for the subsonic full potential equation with embedded geometries in two dimensions. Each coordinate of the object of study is considered a design parameter in the adjoint analysis, where the effect of the level set function is considered. The sensitivities of the objective function with respect to the design parameters are validated by comparing them to the sensitivities obtained by using a finite differences approach. A shape optimization problem where the lift coefficient is maximized with geometrical constraints is solved as an example of application of the adjoint sensitivities. The embedded shape optimization problem is extended to consider uncertainties in the inlet condition. The optimization problem is reformulated by choosing a risk measure, the Conditional Value-at-risk, which is minimized. The adjoint sensitivities are adapted for the stochastic case, considering the selected risk measure. The estimation of the risk measure is performed thanks to an external uncertainty quantification library, by applying a novel approach which uses Monte Carlo methods to estimate the Conditional Value-at-risk. The stochastic case is solved in a distributed environment, where each optimization step deploys a Monte Carlo hierarchy to estimate the objective function and its gradients.
  

Reading date: 05/07/2024

• AGUILAR MORENO, MIGUEL: Liquid-Liquid membrane contactors for sustainable ammonia recovery and valorization: experimental insights, novel approaches and applications
  
  Author: AGUILAR MORENO, MIGUEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CHEMICAL PROCESS ENGINEERING
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 16/04/2024
  Reading date: 05/07/2024
  Reading time: 10:00
  Reading place: EEBE (Escola d'Enginyeria Barcelona Est), Sala Polivalent de l'Edifici A, planta baixa, Campus Diagonal-Besòs
  Thesis director: CORTINA PALLAS, JOSE LUIS | VALDERRAMA ANGEL, CESAR ALBERTO
  Committee:
       PRESIDENT: DOSTA PARRAS, JOAN
       SECRETARI: GIBERT AGULLO, ORIOL
       VOCAL NO PRESENCIAL: REZAKAZEMI, MASHALLAH
  Thesis abstract: This comprehensive research represents a significant stride in the exploration of innovative strategies aimed at enhancing ammonia recovery within diverse wastewater streams. The study is structured into distinct phases, each addressing crucial aspects of the ammonia recovery process. In the initial phase, the research focuses on augmenting membrane contactor performance, employing coagulation-flocculation (C/F) and aeration as preliminary treatments. The outcomes of this phase demonstrate substantial increases in both the mass transfer coefficient and overall efficiency ofammonia recovery, particularly notable when treating the real sidestream centrate. A pivotal finding underscores the efficacy of dosing aluminum sulphate (Al2(SO4)3) at 30 mg Al+/L in the C/F process, yielding remarkable efficiencies in the removal of chemical oxygen demand (COD), turbidity, and total suspended solids (TSS). Into the second phase, the study delves into the sustainable application of liquid-liquid membrane contactors (LLMC) for ammonia recovery. An array of experimental conditions is meticulously explored, with the results illuminating the considerable impact of replacing the acid washing liquid between steps on the overall performance of the LLMC. Additionally, the study highlights the nuanced relationship between the initial ammonia concentration and the subsequent recovery, providing valuable insights. This phase effectively showcases the potential versatility and efficiency of LLMCs in the valorization of ammonia within wastewater streams. The third and final phase introduces a novel asymmetric hollow fiber liquid-liquid membrane contactor (HF-LLMC) with distinctive selectivity for ammonia over water. The investigation entails a comprehensive examination of various operational parameters, including feed and acid flow rates, mass transfer coefficients, and acid consumption. Notably, the results affirm the high selectivity of the HF-LLMC for ammonia, coupled with minimal water transfer. This establishes the HF-LLMC as a promising technology for the recovery and concentration of ammonium in diluted urban and industrial streams. The amalgamation of these findings, approached with a global perspective, significantly contributes not only to the advancement of sustainable nutrient recovery technologies but also underscores their pragmatic feasibility for implementation within the frameworks of the circular economy and efficient resource management.