Numerical Simulation of Heat Transfer and Fluid Flow in Additively Manufactured Plate-Fin Heat Exchangers with Wavy Fins

Abstract

The heat transfer is considered to be one of the most important industrial processes as seen in all these opulent applications in energy conversion and in chemical industry. This thesis presents a CFD numerical simulation of heat transfer and fluid flow in plate-fin heat exchangers (PFHE) design to predict the fluid friction and heat transfer characteristics, and we investigate in detail the effect of longitudinal heat conduction effects using the open source CFD code OpenFOAM. Numerical tests for both the hot and cold fluid in the laminar flow regime ranging between 50 ≤ Re ≤ 2000 of the Reynolds number with different cases of geometrical parameters of the fin were performed (1, 1.1 and 1.2 mm in fin spacing; 0, 1.5, 2 and 2.5 mm in fin amplitude; 65, 100, 130 and 195 mm in fin length). The results for each case of the wavy fin with variation in fin amplitude are presented by means of a Colburn j factor and the Fanning friction factor f. The results reveal that the longitudinal heat conduction in the fins and the plates itself has a significant influence on the heat transfer performance in all cases. The CFD results are compared with available correlations in the literatures for Shah and London [1] and Chennu [2]. We also find that the available correlations for wavy fins are not suitable for the general case of the variable geometrical parameters to predict the heat transfer and pressure drop, particularly when the amplitude of the fins is small. Therefore, we have developed new correlations which extend the application range also for small fin amplitudes. Three models are presented for evaluation the heat transfer coefficient within a given range. A good agreement between the new correlations and analytical and numerical models are shown in this thesis. The CFD data of the single pair of wavy channels in the plate-fin heat exchanger were validated with the experimental data. The heat transfer performance data for both the experimental and CFD numerical results were obtained at the inlet gas temperature, ranging (1023-840 K) for hot gas, and for cold gas ranging between 523-476 K. The experimental and numerical results are validated by the available literatures from Chennau [11], Junqi et al. [13], and new correlations which illustrate a sufficiently good agreement with our results.