Abstract
This thesis is aimed to the optimization of a waste heat recovery system with thermoelectric generators (TEGs). The system will be optimized by developing an efficient three-dimensional (3D) thermal resistance model. In this thesis, it is shown that analysis of three-dimensional (3D) thermal resistance model is a rapid and simple method to estimate the power generated from a waste heat recovery system with thermoelectric generators (TEGs) and assists to optimize the system. The estimation of generated power is an important part of the system design. Methods of Computational Fluid Dynamics (CFD) assist the analysis and improve the performance with great accuracy but great computational duration. The use of this method saves much time relative to such CFD methods. In 3D thermal resistance model, a node of unknown temperature is located at the centroid of each cell into which the system is divided. The relations of unknown temperatures at the cells are based on the energy conservation and the definition of thermal resistance. The temperatures of inlet waste hot gas and ambient fluid are known. With these boundary conditions, the unknown temperatures in the system are solved, enabling estimation of the power generated with TEGs. A 3D model of the system was simulated with FloTHERM; its numerical solution matched the solution of the 3D thermal resistance model less than 5 %. The power generated with the same system with TEGs (TMH400302055, Wise Life Technology, Taiwan) was measured; the experimental result is consistent with the result obtained from the 3D thermal resistance analysis; the relative deviation is approximately 10 %. The power generated is affected by many variables; the positions of the TEGs, the uniformity of the internal flow of the velocity profile and the internal and external flow velocities are considered in our 3D thermal resistance model analysis. According to the results, both the positions of the TEGs and the uniformity of the internal flow of the velocity profile should be taken into account to maximize the power generation. Under varied operational conditions, the power generated from the system might be more sensitive to the velocity of either the internal or external flow. Choosing an appropriate method makes increasing the power generation efficient. The relations between variables and power generation are readily revealed, even with varied parameters, yielding an optimal design of a waste heat recovery system.