In the last decades, the research of new materials in order to be able to re-use otherwise wasted energy has been of uttermost importance in order to progress into a more sustainable world. This work aims to shed light of two families of organic materials that are currently being researched as Phase Change Materials (PCMs) in order to reuse thermal energy, the paraffins and the fatty acids. Although these two groups present good thermal storage properties, they have very low thermal conductivity and need to be contained which makes mandatory the need for a metallic structure to contain them and increase their transition rate. To be able to expand their uses to higher temperature applications than the ones where are currently being applied, experimental characterization of thermophysical properties for two relatively high melting temperature species (Lignoceric acid and Sasolwax C80) has been done via a wide array of techniques and reported. The experimental test carried out were laser flash analysis (LFA), Differential Scanning Calorimetry (DSC) and Vertical Dilatometry in order to fully characterize the before mentioned materials in a temperature range from 20 to 100°C. Moreover, in order to be able to use paraffins and fatty acids to design new PCM devices, the understanding of their thermal behavior is needed and the possibility to predict how the thermophysical properties changes with the temperature is highly valuable. For that reason, a comprehensive and extensive data analysis on the available data on the literature for fatty acids and paraffins thermophysical properties has been done and several equations with their goodness are reported. The models reported were on good agreement with the experimental literature data. This way of working is not conventional, since typically the experimental results are presented after the literature survey of the models and data points. However, due to the pandemic conditions at the start of the thesis and for the impossibility of performing tests in initial scheduling, the work was initiated with the literature review and modelling of the materials and then followed with the experimental testing In the experimental simulation chapter, simulations of the LFA test on the materials have been done and compared with the experimental results in order to estimate the model goodness. The comparison gave rise to a good resulting model in the solid temperature ranges while more conditions have to be included to take into account losses at higher temperatures. Lastly, in order to compare how both types of materials would work in a PCM composite conditions, the effective properties of the composites of the organic materials with aluminum were estimated and confronted for different volumetric occupation percentages. The results gave for the same porosity range the fatty acids have slightly better thermal properties combined with higher latent heat of fusion for the same melting range. Moreover, in order to be able to use paraffins and fatty acids to design new PCM devices, the understanding of their thermal behavior is needed and the possibility to predict how the thermophysical properties changes with the temperature is highly valuable. For that reason, a comprehensive and extensive data analysis on the available data on the literature for fatty acids and paraffins thermophysical properties has been done and several equations with their goodness are reported. The models reported were on good agreement with the experimental literature data. In the experimental simulation chapter, simulations of the LFA test on the materials have been done and compared with the experimental results in order to estimate the model goodness. The comparison gave rise to a good resulting model in the solid temperature ranges while more conditions have to be included to take into account losses at higher temperatures. Lastly, In the composite effective properties section, in order to compare how both types of materials would work in a PCM composite conditions, based on equations found in the literature, the effective properties of the composites of the organic materials with Al (and with Cu in the case of paraffins) were estimated and confronted for different volumetric occupation percentages. The results gave for the same porosity range the fatty acids have slightly better thermal properties combined with higher latent heat of fusion for the same melting range.
Negli ultimi decenni, la ricerca di nuovi materiali per poter riutilizzare l'energia altrimenti sprecata è stata di fondamentale importanza per progredire verso un mondo più sostenibile. Questo lavoro ha come obiettivo fare luce su due famiglie di materiali organici che sono attualmente oggetto di ricerca come Phase Change Materials (PCM) al fine di riciclare l'energia termica sprecata e utilizzarla in altri processi, le paraffine e gli acidi grassi. Nonostante questi due gruppi presentino buone proprietà di accumulo termico, hanno una conduttività termica molto bassa e devono essere contenuti, avendo la necessità di una struttura metallica per contenerli e aumentare il loro tasso di transizione di fase. In particolare, al fine di poter espandere i loro usi ad applicazioni a temperature più elevate rispetto a quelle attualmente applicate, la caratterizzazione sperimentale delle proprietà termofisiche per due specie con temperature di fusione relativamente elevate (acido lignocerico e Sasolwax C80) è stata effettuata tramite un ampio gruppo di. Le prove sperimentali effettuate sono state laser flash analysis (LFA), la calorimetria a scansione differenziale (DSC) e la dilatometria verticale al fine di caratterizzare completamente i suddetti materiali in un intervallo di temperatura da 20 a 100°C. Inoltre, per poter utilizzare paraffine e acidi grassi per progettare nuovi dispositivi PCM, è necessaria la comprensione del loro comportamento termico ed è molto importante avere la possibilità di prevedere come le proprietà termofisiche cambiano con la temperatura. Per questo motivo è stata effettuata un'analisi completa ed estesa dei dati sui dati disponibili in letteratura per le proprietà termofisiche degli acidi grassi e delle paraffine e sono riportate diverse equazioni con la loro bontà. I modelli riportati erano in buon accordo con i dati della letteratura sperimentale. Nel capitolo della simulazione sperimentale sono state effettuate simulazioni del test LFA sui materiali e confrontate con i risultati sperimentali al fine di stimare la bontà del modello. Il confronto ha dato origine a un buon modello risultante negli intervalli di temperatura dei solidi, mentre è necessario includere più condizioni per tenere conto delle perdite a temperature più elevate. Infine, nella sezione delle proprietà efficaci dei compositi, al fine di confrontare come entrambi i tipi di materiali funzionerebbero in condizioni di un composito PCM, sulla base di equazioni presenti in letteratura, le proprietà efficaci dei compositi dei materiali organici con Al (e con Cu nel caso delle paraffine) sono state stimate e confrontate per diverse percentuali di occupazione volumetrica. I risultati hanno fornito per lo stesso intervallo di porosità gli acidi grassi hanno proprietà termiche leggermente migliori combinate con un calore latente di fusione più elevato per lo stesso intervallo di fusione.
Modelling thermophysical properties of fatty acids for composite phase change materials, including experimental data on lignoceric acid
Morcella, Tomas Hector
2021/2022
Abstract
In the last decades, the research of new materials in order to be able to re-use otherwise wasted energy has been of uttermost importance in order to progress into a more sustainable world. This work aims to shed light of two families of organic materials that are currently being researched as Phase Change Materials (PCMs) in order to reuse thermal energy, the paraffins and the fatty acids. Although these two groups present good thermal storage properties, they have very low thermal conductivity and need to be contained which makes mandatory the need for a metallic structure to contain them and increase their transition rate. To be able to expand their uses to higher temperature applications than the ones where are currently being applied, experimental characterization of thermophysical properties for two relatively high melting temperature species (Lignoceric acid and Sasolwax C80) has been done via a wide array of techniques and reported. The experimental test carried out were laser flash analysis (LFA), Differential Scanning Calorimetry (DSC) and Vertical Dilatometry in order to fully characterize the before mentioned materials in a temperature range from 20 to 100°C. Moreover, in order to be able to use paraffins and fatty acids to design new PCM devices, the understanding of their thermal behavior is needed and the possibility to predict how the thermophysical properties changes with the temperature is highly valuable. For that reason, a comprehensive and extensive data analysis on the available data on the literature for fatty acids and paraffins thermophysical properties has been done and several equations with their goodness are reported. The models reported were on good agreement with the experimental literature data. This way of working is not conventional, since typically the experimental results are presented after the literature survey of the models and data points. However, due to the pandemic conditions at the start of the thesis and for the impossibility of performing tests in initial scheduling, the work was initiated with the literature review and modelling of the materials and then followed with the experimental testing In the experimental simulation chapter, simulations of the LFA test on the materials have been done and compared with the experimental results in order to estimate the model goodness. The comparison gave rise to a good resulting model in the solid temperature ranges while more conditions have to be included to take into account losses at higher temperatures. Lastly, in order to compare how both types of materials would work in a PCM composite conditions, the effective properties of the composites of the organic materials with aluminum were estimated and confronted for different volumetric occupation percentages. The results gave for the same porosity range the fatty acids have slightly better thermal properties combined with higher latent heat of fusion for the same melting range. Moreover, in order to be able to use paraffins and fatty acids to design new PCM devices, the understanding of their thermal behavior is needed and the possibility to predict how the thermophysical properties changes with the temperature is highly valuable. For that reason, a comprehensive and extensive data analysis on the available data on the literature for fatty acids and paraffins thermophysical properties has been done and several equations with their goodness are reported. The models reported were on good agreement with the experimental literature data. In the experimental simulation chapter, simulations of the LFA test on the materials have been done and compared with the experimental results in order to estimate the model goodness. The comparison gave rise to a good resulting model in the solid temperature ranges while more conditions have to be included to take into account losses at higher temperatures. Lastly, In the composite effective properties section, in order to compare how both types of materials would work in a PCM composite conditions, based on equations found in the literature, the effective properties of the composites of the organic materials with Al (and with Cu in the case of paraffins) were estimated and confronted for different volumetric occupation percentages. The results gave for the same porosity range the fatty acids have slightly better thermal properties combined with higher latent heat of fusion for the same melting range.| File | Dimensione | Formato | |
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Thesis - Morcella.pdf
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Executive Summary - Morcella.pdf
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Descrizione: Executive Summary
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https://hdl.handle.net/10589/186243