Simulated Thermal Resistance of Thermogalvanic Cells with Triply Periodic Minimal Surface Structures using ANSYS

Buildings release an abundance of waste heat that is left unused. Thermogalvaniccells (TGCs) can take advantage of waste heat to generate electricity with a low temperature gradient. In this dissertation, I simulated the thermal transport of TGCs containing different triply periodic minimal surface (TPMS) structures, compared it to measured values and conducted a mesh convergence study to examine the viability of the computational fluid dynamics (CFD) solutions. Natural convection effects are one of the driving forces in TGCs. Using the Bousinesq approximation, I was able to capture those effects in the CFD simulations as it accounts for the density variations of the fluid. Upon simulating the TGC using the Schwarz P TPMS geometry, the cathode temperature converged as I refined the mesh and approached the measured value. As for the IWP TPMS structure, the solution converged as I refined the mesh, despite having a deviation to the measured values. This was due to the abundance of sharp regions along the walls of the TPMS that ANSYS had difficulty to accurately model. Furthermore, I simulated the TGCs using different boundary condition (BC) approximations to observe the cathode and anode temperatures as well as their overall ∆T across the cell. For the TGC containing the Schwarz P geometry, Case C (constant anode temperature BC with TPMS conduction) was the most accurate while Case D (convection BC at anode with TPMS conduction) deviated from the measured values, had the most accurate ∆T and was well within the uncertainty bounds of the measured values. Larger temperature fluctuations were seen closer to the cathode while the effects steadily decrease as the fluid approaches the anode. Moreover, the TGC containing the IWP structures presented interesting results. The main deviation was from the cathode temperatures because a higher temperature readings meant that more cells in the fluid domain were prone to diverging, thereby resulting in a higher calculated cathode temperature. Simulating the TGC with the Schwarz P geometry produced satisfactory results while the TGC using the IWP geometry deviated due to the software limitations. Finally, the effects of natural convection and TPMS on TGCs were studied and it was found that the absence of natural convection lead to a higher ∆T while the absence of TPMS resulted in a more uniform temperature distribution throughout the domain