Ozer, Rahim Aytug; Doğuş Tuncer, Azim; Khanlari, Ataollah; Sözen, Adnan; Kılınç, Cuma; Afshari, Faraz

This study experimentally investigates the performance of a fanless thermoelectric cooling system operating under natural convection conditions, with particular emphasis on simple and cost-effective hot-side thermal management. A commercial TEC12703 module was integrated into a miniature refrigeration system consisting of a Styrofoam enclosure, where heat rejection from the hot side was achieved using a folded aluminum plate without any auxiliary cooling components such as fans, pumps, or heat pipes. The aluminum plate was geometrically modified to enhance heat dissipation while maintaining a small footprint and to reduce thermal interaction with the refrigerator wall by increasing the effective separation distance. Experiments were conducted at six different input voltages (3, 4, 5, 6, 7 and 8 V) to evaluate the voltage-dependent cooling behavior and overall system performance under passive cooling conditions. The results demonstrate that even with a simple plate-type heat spreader, stable operation of the thermoelectric module can be maintained, although hot-side temperature rise significantly influences cooling capacity and coefficient of performance (COP) as the input voltage increases. The folded plate configuration achieved up to approximately 2–3 °C lower cold space temperatures and about 15–20% higher COP values compared to the flat plate, particularly within the optimum operating voltage range of 5–6 V. The findings highlight the critical role of hot-side heat rejection in fanless thermoelectric systems and confirm that appropriately designed folded aluminum plates can provide a viable passive thermal management solution for low-power and compact refrigeration applications where simplicity, reliability, and low energy consumption are prioritized.

Celik, Adem; Yilmaz, Mehmet; Kaya, Mehmet; Karagoz, Sendogan

In the present study, it was aimed to produce a fundamental information and to investigate the effects of various design parameters on tube performance characteristics by setting up vortex tube experimental system in order to study the parameters predetermined for the design of vortex tubes and by conducting thermodynamic analysis. According to the findings of experiments, as the mass flow rate of cold flow increases (yc) temperature of cold flow also increases, while the temperature of warm flow increases approximately to yc = 0.6 and then decreases. Increases in inlet pressure, inlet nozzle surface and diameter of the cold outlet orifice increased temperature differences between cold and warm flows. Tube with L/D = 10 showed better performance than with L/D = 20. The finding that irreversibility parameter is very close to critical threshold of irreversibility proved that process in vortex tube is considerably irreversible. Coefficient of performance (COP) values in vortex tube were much lower than other heating and cooling systems. This situation may show that vortex tubes are convenient in the processes where productivity is at the second rate compared to other factors.