Heat transfer mechanisms in thermosyphon condensation

This study presents an experimental investigation and a theoretical analysis of condensation phenomena in a two-phase closed thermosyphon. Specific components were designed and assembled for the fabrication of the thermosyphon and its associated testing apparatus. Thermocouples were strategically positioned along the external surface of the thermosyphon, with additional sensors installed to monitor internal temperatures in the evaporator and condenser sections. A data acquisition system, integrated with dedicated software, was employed to record the steady-state temperature distribution. Nusselt’s classical formulation was employed as the basis for estimating the liquid film thickness, while liquid film Reynolds numbers were calculated for each test using the hydraulic diameter as the characteristic length. Experimental heat transfer coefficients were obtained through a thermal resistance network approach, and the corresponding Nusselt numbers for condensation were determined. An uncertainty analysis indicated that the measurements were subject to a deviation of ±23.6%. The experimental results were compared against seven correlations selected from the literature. The substantial discrepancies observed suggest that the mechanisms governing internal heat transfer in such systems are still not fully understood and require further investigation. The combination of theoretical modeling, experimental data, and advanced visualization techniques represents a promising approach toward achieving a more comprehensive understanding of these processes.