Percorrer por data de Publicação, começado por "2026-03-30"
A mostrar 1 - 1 de 1
Resultados por página
Opções de ordenação
- Frost Detection in Refrigeration Systems through Sensor Technology IntegrationPublication . Aguiar, Martim Lima de ; Gaspar, Pedro Miguel de Figueiredo Dinis Oliveira; Silva, Pedro Nuno Dinho Pinto daFrost formation on refrigeration system evaporators degrades thermal performance and increases energy consumption. Conventional defrosting methods, typically timecontrolled, are inefficient and lead to unnecessary energy use. This thesis addresses this issue by developing and validating a cost-effective resistive sensor for demand-defrost applications. An iterative design-build-test methodology was employed to evaluate various sensor configurations, such as the air gap, ceramic medium, and fabric-medium designs. To provide an objective benchmark, a computer vision method was developed to quantify frost accumulation, complemented by an absolute humidity-based detector for validating defrost completion. The FMRS4 sensor demonstrated the most repeatable performance, consistently detecting both frost nucleation and defrost completion when sensor placement is adequate. Signal processing algorithms, including a Frost Nucleation Detector and a Defrost Completion Detector, were successfully developed and implemented. The study also highlights the importance of sensor placement, utilising frost formation maps derived from CV analysis to identify optimal sensor placement. Furthermore, strategies to mitigate electrochemical effects and compensate for temperature dependency were developed, and the feasibility of an energyautonomous sensor powered by a thermoelectric generator was demonstrated. The research culminates in a validated sensor technology that offers a practical pathway towards more intelligent and energy-efficient refrigeration systems.