Effect of using hybrid nanofluids as a coolant on the thermal performance of portable thermoelectric refrigerators

Abstract

This study investigated the effect of using hybrid nanofluids as a refrigerant in portable thermoelectric refrigerator applications on thermal performance. For this purpose, a cooling cabinet with an internal volume of 36 L was designed and produced. Then, the Peltier assembly, with a water-cooled block attached to its hot surface, was placed in this cooling cabinet from the middle of its front cover. With the help of a refrigerant, the heat was removed from the Peltier's hot surface and transferred to the atmosphere via a water-to-air heat exchanger. Hybrid nanofluids prepared with Al2O3-TiO2-SiO2 and nanoparticles and water were used as the refrigerant in the system. To evaluate the thermal performances of these hybrid nanofluids, the tests were repeated using water without added nanoparticles as the reference case. According to the results obtained from the experimental study, it was observed that in all cases, tests using nanofluids gave better results than the reference cases. In addition, it was determined that the efficiency obtained from the system increased as the nanoparticle ratio in the mixture increased in all cases. Despite significant improvements in cooling cabinet and cooled product temperatures in hybrid nanofluids, the COP values ​​of the systems are slightly lower than in the reference case due to the Peltier effect. Considering the difference between the first and last temperatures of the cooled cabinet, the greatest improvement compared to the reference situation was determined as 30.3 % in the case of loaded state conditions and in the case of using 2 % Al2O3-TiO2-SiO2-Water nanofluid. For the unloaded conditions, this value was obtained as 25.1 % in the case of using 2 % Al2O3-TiO2-SiO2-Water nanofluid. On the other hand, for the unloaded condition, the lowest COP value was calculated as 0.47 and 0.45 when Al2O3-TiO2-SiO2-Water nanofluid was used in 1 % and 2 % mass fraction, respectively. For the loaded condition, this value was found as 0.48 in the case where 1 % Al2O3-TiO2-SiO2-Water and 0.47 in the case where 2 % Al2O3-TiO2-SiO2-Water nanofluid was used.