Multi-Channel Heat Pipe: Experimental Investigation, CFD Analysis, and Theoretical Modeling of Two-Phase Heat Transfer

This is the study of an innovative application of multi-channel heat pipe use for harnessing and reusing wasted heat from engine exhaust. To unravel the intricacies of two-phase heat transfer involving boiling and condensation within multi-channel heat pipes, a distinctive multichannel heat pipe was designed and constructed. Computational Fluid Dynamics (CFD) and theoretical models for the multi-channel heat pipe were developed for a comprehensive understanding. The simulation of multichannel heat pipe operation using ANSYS Fluent employed the Volume of Fluid (VOF) approach and the Lee model. Multiple Lee models, implemented through user-defined functions (UDF), were compared, and the impact of condenser boundary conditions, saturation temperature, and mass transfer coefficient on the simulations was thoroughly examined. This study identifies the significant limitations of the Lee model for heat pipe simulation, exposing its incapability in predicting heat pipe temperatures due to low physical significance and susceptibility to manipulation. A novel theoretical model was formulated for multi-channel heat pipes which were based on experimental data from multichannel heat pipe. This model uses the thermal-electrical resistance analogy to predict the thermal resistance of the multichannel heat pipe. The selection of optimal correlations for pool boiling and film wise condensation, the developed iterative theoretical model achieved 9.2% error in predicting the thermal resistance of multichannel heat pipe. In conclusion, this research sheds light on the intricacies of multi-channel heat pipes and highlights the shortcomings of existing Lee models in simulating heat pipe behavior. The proposed theoretical model, grounded in experimental data, provides a more accurate prediction of thermal resistance, paving the way for improved design and performance of heat pipe applications vapor absorption cooling systems.