Fourier series based modeling of the dynamics of inclined closed loop buoyancy driven heat exchangers with conjugate effect

TL;DR

This study develops a Fourier series based 1-D model for inclined closed loop buoyancy-driven heat exchangers, validated with CFD data, highlighting the effects of wall conduction and inclination on system dynamics.

Contribution

The paper introduces a Fourier series based 1-D modeling approach for conjugate heat exchangers, validated against 3-D CFD, capturing transient behaviors and flow reversals.

Findings

Good agreement between 1-D model and CFD data.

Wall conduction and inclination significantly affect transient behavior.

Flow reversal can be predicted by the model.

Abstract

The modelling of the dynamics of inclined closed loop buoyancy driven heat exchangers with inclusion of the wall conduction effect at the heat exchanger is presented in the current study. A Coupled Natural Circulation Loop (CNCL) is an ideal system for studying the closed loop buoyancy driven heat exchanger. The modelling utilises a Fourier series based approach to develop a 1-D model which is then verified with the 3-D CFD studies of the respective cases. A good agreement is observed with the 3-D CFD data, which demonstrates the suitability of the 1-D model for transient behaviour prediction. The non-dimensional numbers and thermal coupling sensitivity coefficients which govern the dynamics of the CNCL are identified and an appropriate parametric study is conducted. Results show that the wall conduction and inclination have a significant effect on the transient behaviour of the CNCL system. A jump in the heat transfer coefficient with variation in the inclination of the Conjugate CNCL system is observed. The 1-D model is also able to capture the flow direction reversal with change in the inclination of the Conjugate CNCL system for zero flow field initial conditions.