Purpose
The purpose of this paper is to experimentally and numerically investigate the cooling performance of the air-to-water thermoelectric cooling system under different working conditions.
Design/methodology/approach
An air-to-water thermoelectric cooling system was designed and manufactured according to the principle of discrete binary thermoelectric Peltier modules, and the thermal performance, heat transfer rate and average COP values were examined at different cooling water temperatures and voltages applied. Additionally, numerical simulations were performed by computational fluid dynamics approach to investigate the temperature distribution and airflow structure inside the cooling chamber.
Findings
Analyses were performed using experimental tests and numerical methods. It was concluded that, by decreasing the cooling water temperature from 20 to 5 °C, the average COP increases about 36%. The voltage analysis showed that the efficiency of the system does not always increase as the voltage rises; more importantly, the optimum voltage is different and depends on whether it is desired to increase COP or increase the cooling rate.
Originality/value
In the studies published in the field of thermoelectric cooling systems, little attention has been paid to the voltage applied and its relationship to other operating conditions. In most cases, the tests are performed at a constant voltage. In this study, several options, including applied voltage and cooling water temperature, were considered simultaneously and their effects on performance have been tested. It was found that under such studies, optimization work should be done to evaluate maximum performance in different working conditions.
In this research, pure water and recycled nanofluids (RNF) are utilized as heat transfer fluids in the thermoelectric cooling (TEC) system, and the effects of these fluids on the cooling performance are experimentally examined. In order to prevent nanofluid sedimentation and enhance stability, a surface modification process on Fe<sub>3</sub>O<sub>4</sub> particles is performed. With modified Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>-mix-(CH<sub>2</sub>)<sub>3</sub>Cl@Imidazol nanoparticles, water-based nanofluids are prepared at a constant volumetric concentration. This nanofluid is used in a TEC system and recycled. The sonication time is chosen as the experimental parameter in the preparation of RNF. The RNF are subjected to ultrasonication at different time periods, including 3.5, 7, and 14 hours. The temperature drops inside the cooling chamber, coefficient of performance (COP) value of the TEC system, and dimensionless numbers, including Reynolds and Nusselt of nanofluids, are evaluated and discussed in detail. It is determined that the performance of the TEC system can be increased significantly with the usage of nanofluids. Although some deterioration in heat transfer properties is observed for the RNF, these fluids provide a significant improvement in cooling performance compared to pure water. Increasing the nanofluid flow rate increases the cooling chamber performance up to a certain level. Moreover, a significant increase in TEC chamber performance is also achieved by decreasing the temperature of the water bath in the system.
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