Assessment of Working Fluid Efficacy in Shell-and-Tube Heat Exchangers using OpenFOAM
Rida SN Mahmudah, Restu Widiatmono, Denny Darmawan

Universitas Negeri Yogyakarta

Abstract

The choice of working fluid significantly influences the thermal performance of heat exchangers, especially in high-temperature energy systems such as those used in nuclear reactors. This study compares four candidate fluids-water, molten salt, lead-bismuth eutectic (LBE), and FLiBe-used in a shell-and-tube heat exchanger model. Transient conjugate heat transfer simulations were performed using OpenFOAM v12 for each fluid at four different mass flow rates (0.01, 0.05, 0.25, and 0.5 kg/s) while maintaining a constant temperature difference between shell and tube inlets.
The results show that water has the highest heat transmission rate due to its large specific heat capacity- however, its effectiveness decreases at higher flow rates. In contrast, owing to its excellent thermal conductivity, LBE provides superior thermal efficiency, particularly at low flow rates. FLiBe demonstrated a strong balance between thermal transfer capabilities and efficiency under a variety of flow conditions. The study emphasizes the trade-offs between energy transmission and utilization, demonstrating that higher heat transfer rates do not necessarily equate to greater effectiveness. These findings support a more informed selection of working fluids for thermally demanding systems such as nuclear heat exchangers.

Keywords: conjugate heat transfer, OpenFOAM, multi-region heat exchanger, molten salt, transient heat transfer

Topic: Instrumentation and Computational Physics