Performance of thermoelectric generators for direct and indirect contact with cooling water

Thermoelectric generators (TEGs) are devices that produce electricity due to the temperature difference between their cold and hot surfaces. The enhanced heat transfer from the cold surfaces of TEGs can increase their electricity efficiency. In this research, an experiment was arranged to study the direct and indirect contact of cooling water on the cold surfaces of the TEGs series and its results on their electricity efficiency. In this experiment, cooling water was flowing inside an aluminum tube with a rectangular cross-section. By changing the slope of the pipe, mixed convection was created in the cooling water. The results showed that the electrical efficiency of the TEGs was higher in the conditions of indirect contact as well as opposing mixed convection. In one of the results, the maximum electricity generation in indirect contact is 48 mW at pipe slop of 30(?) to 35 mW at pipe slop of 90(?), more than direct contact. Since the connection of cold surfaces of TEGs happens indirectly through expensive metal plates such as copper and aluminum, therefore, the results of this research can be useful in the economic evaluation and improvement of such devices.