Increasing heat transfer in double-pipe heat exchangers (DPHEs) is an interesting topic due to challenges that still remain to be solved, especially when working under low-to-moderate flow rate regimes where poor mixing and thermal boundary layers reduce the effectiveness of convection. Despite numerous studies conducted on the basis of metal-foam and insert-type enhancement methods, existing research mostly covers completely-filled or simplified partially-filled cases. The present work numerically investigates thermo-hydraulic performance of a countercurrent DPHE using various structured metal-foam inserts installed in the annulus region. In particular, a three-dimensional CFD model of the studied geometry was successfully validated with previously reported experimental data with deviations not exceeding ±5 % for the average Nusselt number and ±7 % for the friction factor. In simulations, hot water flows inside the inner pipe at temperature 75 °C and 3 L/min, whereas cold water enters the annulus at temperature 30 °C with flow rates of 1 to 9 L/min, equivalent to Reynolds numbers of 205-1845. In total, nine geometries were considered including a smooth basecase, fully filled foam geometry, circular ring foam baffles, continuous three-strips foam geometry, as well as five interrupted three-strips foams with 5, 7, 9, 11, and 13 interruptions, respectively. For all cases, copper foam with porosity 0.9 and pores density 40 PPI was used, while water thermophysical properties were assumed constant. It was found that inserting structured metal-foam increases heat transfer due to mixing effect and repeated disruption/regeneration of thermal boundary layer. As compared with the smooth base case, the fully filled metal-foam geometry showed the largest improvement in heat transfer performance by providing up to 15 times higher values of the average Nusselt number. Nevertheless, the interrupted strips foam designs demonstrated the best thermo-hydraulic characteristics in terms of trade-off between enhanced heat transfer and increased pressure drop penalty. In particular, the interrupted foams led to approximately 1.5-3 times higher friction factor than the smooth geometry, while performance evaluation factor PEF equaled approximately 2.8. Therefore, it can be concluded that interrupting structured metal-foam inserts could be considered promising passive enhancement approach for low-to-moderate Reynolds number DPHEs.
Inas Faiz Kadhim, A. J. J. Al-jassani, H. Al-Bugharbee· Mathematical Models in Engin...· 0 citations
This work aims to evaluate the thermal and hydraulic performance (TPF) of shell and tube heat exchanger with structured metal foam baffles. The configurations of the metallic foam baffles contain baffles with 20% cut ratio, double cut ratio (2 × 10%), and helical tape form. Additionally, the impact of baffles inclination angle of 0° and 30° were also investigated in the first two configurations. For these entire configurations, metal foam was kept with constant volume. Numerical simulations using ANSYS FLUENT 2025 R2 software were performed to estimate the TPF of the heat exchanger for each configuration. Nusselt number (Nu), outlet temperature, and pressure drop () were calculated and compared with those obtained from conventional solid baffles. All the results were obtained at a mass flow range of 1.2 to 2.0 kg/s. The findings demonstrated that the use of metallic foam baffles generally reduced the pressure drop by up to 52% compared with solid baffles. In comparison to solid baffles, the double‐cut design (2 × 10%) showed a 54.4% increase in the Nu with a 23% reduction in pressure drop and 2.389 increase in the TPF value. Additionally, it was observed an increase of 74% in the Nu, and an increase of 4.906 in the TPF for the helical tape configuration.
R. Faraj, Abbas J. Jubear Al‐ Jassani, H. Al-Bugharbee· Heat Transfer· 0 citations
This study aims to develop and evaluate an innovative design of a shell and tube heat exchanger (STHX) featuring porous sectional baffles to enhance its thermal and hydraulic performance (TPF). A numerical investigation based on computational fluid dynamics (CFD) is conducted to analyze the TPF of STHX. A parametric study is performed to evaluate the effects of baffle inclination angle and double cut ratio design on heat transfer and pressure drop characteristics. The model included six metal foam baffles with an initial cut ratio of 20 % (MFBs), and its performance was compared to that of a conventional heat exchanger with solid baffles. The effect of foam baffle inclinations at various angles (0°,10°, 20°, 30° and 30° parallel) was also analysed. Also, the effect of the double-cut ratio of the foam baffle (2×10 %, 2×15 %, 2×20 %, and 2×10 % parallel) over a range of mass flow rates between 1.2 and 2.0 kg/s and
R
e
range (11000-16000). The results showed that the use of MFBs lead to a maximum reduction of
∆
P
by 32 % with (2×10 %) design at 2 kg/s accompanied by a significant improvement in TPF. Furthermore, a 30° baffle inclination improved the TPF to 2.207 at (1.2 kg/s), accompanied by a 50 % increase in
N
u
and a 25.5 % reduction
∆
P
. The best TPF was recorded at the ratio (2×10 %), where the (TPF) = 2.389 at 1.2 kg/s, with a
N
u
improvement of 54.4 % compared to a solid baffle. The obtained results provide useful design guidelines for STHXs widely used in energy, petrochemical, and chemical processing industries.
R. Faraj, A. J. J. Al-jassani, H. Al-Bugharbee· Mathematical Models in Engin...· 0 citations
