Experimental analysis of a dew-point evaporative cooler based on triply periodic minimal surfaces

The global increase in energy demand, driven by climate change, urbanization, and rising living standards, has made indoor cooling a critical challenge. Traditional air conditioning systems, based on vapor compression cycles, are energy-intensive and rely on refrigerants with high global warming potential, while traditional direct evaporative coolers add moisture to the ambient air. As a result, sustainable alternatives are gaining attention, particularly Dew Point Evaporative Cooling (DPEC), which offers high efficiency without adding moisture to the ambient air. This thesis presents an experimental investigation of a novel DPEC system that integrates Triply Periodic Minimal Surfaces (TPMS) (specifically, a gyroid geometry) into the heat exchanger design. These surfaces, characterized by high surface-to-volume ratios and zero mean curvature, are ideal for enhancing heat transfer. The gyroid structure was fabricated using additive manufacturing (3D printing) with PLA material, enabling the creation of complex geometries that are otherwise unfeasible with conventional methods. The research has two main objectives: (1) to evaluate the thermal and fluid dynamic performance of the TPMS-based heat exchanger within a DPEC cycle, and (2) to develop a modular and reusable experimental setup for future studies. The test rig includes sensors for temperature, humidity, and pressure, a centrifugal fan, an electric heater, and a water injection system, all controlled via Arduino boards. The setup allows for flexible configuration and precise control of operating parameters. A total of 64 experimental configurations were tested, varying fan speed (PWM), inlet air temperature (30°C and 35°C), and recirculation rate. Key performance indicators such as cooling capacity, wet bulb effectiveness, coefficient of performance (COP), water consumption, and relative humidity were analysed. The results show that while absolute cooling capacity and COP are lower than those reported in literature, the cooling capacity per unit volume is competitive, highlighting the potential of TPMS geometries in compact applications. Thermographic analysis revealed uneven water distribution within the wet channel, which affected performance consistency. This suggests that future improvements should focus on optimizing the water injection system, possibly through better nozzle design or surface coatings. Additionally, the use of materials with higher thermal conductivity could further enhance performance. The study also identifies limitations in measurement accuracy and proposes improvements in instrumentation and experimental protocols. Despite these challenges, the research demonstrates the feasibility of using TPMS structures in DPEC systems and lays the groundwork for further development. The modular test rig will be used in upcoming research funded by the university, aiming to refine the system and explore new geometries and materials. This thesis contributes to the advancement of sustainable cooling technologies by combining innovative geometry with experimental validation. The findings support the integration of TPMS-based heat exchangers in energy-efficient cooling systems, with promising applications in buildings, industrial processes, and data centres.