Coupling Analysis of Thermoelectric Characteristics of Power Generation Module in PWR Nuclear Power Plant

[Background]: The thermoelectric power generation technology has advantages in utilizing low-grade heat. Recovery of waste heat from PWR nuclear power plants based on the thermoelectric generators can save energy and protect the ecological environment of the surrounding ocean. [Purpose]: This study aims to propose a simplified model of the thermoelectric generator and carry out the coupling analysis of the power generator module. [Methods]: A single TEG model was established base on COMSOL, which was used to carry out the three-dimensional numerical simulation. The structured mesh generated by the sweep method was used. The temperature and potential contours of the single TEG model were obtained. In order to reduce the computing resources required for the multi-physics coupling calculation, the complex single TEG model was reduced to a thin plate. The reduced model had one type of material. The formula for calculating the equivalent thermal conductivity of the reduced model was derived. Using the original model for the single TEG, the numerical simulation under multiple temperature differences was carried out. The relation of the output power, the equivalent thermal conductivity and the temperature of the hot side and the cold side was obtained. These results were in the form of discrete points. Since the temperature variation in the actual calculation was continuous, the bilinear interpolation method was used to process the data. The reduced model was implemented in FLUENT through the user-defined function (UDF). The model of the thermoelectric generator module with typical structure was established. The model consisted of hot-side water, hot channel wall, cold-side water, cold channel wall and 22 TEGs. The numerical simulation of this model was carried out based on FLUENT. The model had multiple domains, including 2 fluid domains and 22 solid domains. The unstructured mesh was used for the fluid domains, which represented the hot-side water and cold-side water. The structured mesh was used for the solid domains with regular geometry, which was beneficial to reduce the mesh number and improve the mesh quality. The sensitivity analysis was carried out on the influence of hot-side fluid parameters on the output power. [Results]: The thermal-electric coupling analysis of the single TEG is carried out. The temperature drop is mainly concentrated on the semiconductor materials. When the temperature difference between the hot side and the cold side is 200 K, the calculated voltage is 3.8848 V. The result fits well with the reference value, which validates the applicability of this model. The coupling analysis of the thermoelectric generator module is carried out. The temperature distribution and the total output power are obtained by simulation. When the temperature difference between the inlets of hot-side water and cold-side water is 173.15 K, the total output power of the 20 TEGs is 108.66 W. The output power is positively correlated with the temperature and velocity of the hot-side fluid. [Conclusions]: The simplified model of the single TEG is applicable to the coupling simulation. The thermoelectric generator module can utilize the heat source from the PWR nuclear power plant. This study provides reference for the utilization of waste heat in PWR nuclear power plant and the design of thermoelectric generator modules.