Plate heat exchangers (PHEs) play a critical role in the energy efficiency of heat pump systems. However, non-uniform two-phase flow distribution across parallel channels remains a key limitation, as it may cause local dryout and degrade heat transfer performance. To address the limitations of existing prediction approaches, a hybrid modeling framework coupling computational fluid dynamics (CFD) simulations with a distributed parameter model is developed. The model is validated against experimental data under 12 representative operating conditions. The results show that the average prediction errors for the total mass flow rate, pressure drop, and heat transfer rate are within 3%, ±10%, and ±5%, respectively. The influences of refrigerant outlet conditions and inlet distributor geometry on flow distribution uniformity are systematically investigated, identifying the dominant factors governing pressure drop and the mechanism by which distributor orientation improves uniformity. Quantitative optimization shows that an orifice orientation of 225° reduces flow non-uniformity by 67.8% and enhances the heat transfer rate by 4.33% compared with the distributor-free design. The proposed method is robust across various operating scenarios and provides a reliable, quantitative tool for optimizing PHE inlet distributor designs.
The performance of briquette drying systems is strongly influenced by airflow distribution and thermal uniformity within the drying chamber, which are governed by outlet configuration and internal flow patterns. However, limited studies have systematically quantified the effect of exhaust outlet arrangements on the coupled heat transfer and fluid flow behavior in industrial-scale briquette ovens. This study aims to numerically investigate the influence of single-, double-, and four-outlet configurations on airflow characteristics, temperature distribution, and overall thermal performance of a briquette drying oven. A three-dimensional geometric model representing the combustion chamber, drying chamber, and briquette racks was developed and analyzed using Computational Fluid Dynamics (CFD). Steady-state simulations were performed in ANSYS Fluent employing the standard k–ε turbulence model, with air properties, inlet velocity (9.97 m/s), and thermal boundary conditions defined based on operational data. The results reveal that outlet configuration significantly affects flow recirculation intensity and temperature uniformity across the briquette racks. The four-outlet configuration produced the most homogeneous airflow distribution and reduced thermal gradients, thereby enhancing convective heat transfer effectiveness compared to single- and double-outlet designs. Conversely, the single-outlet case exhibited pronounced recirculation zones and localized temperature variations, potentially leading to uneven drying. These findings demonstrate that optimizing outlet arrangement is a critical design parameter for improving drying efficiency and energy utilization in briquette oven systems, providing a validated numerical framework for future thermal system optimization.
Compact heat exchangers (CHEs) are widely used in modern thermal systems due to their high heat transfer efficiency, compact size, and reduced material usage. They find applications in aerospace, automotive, power generation, chemical processing, and electronics cooling. With the growing demand for energy-efficient and lightweight systems, advanced designs such as plate-fin, microchannel, and printed circuit heat exchangers have gained attention. This study presents a CFD-based analysis of heat transfer and fluid flow in compact heat exchangers. Using the finite volume method and RANS turbulence models, the research evaluates key parameters such as temperature distribution, velocity fields, pressure drop, and thermal performance under varying operating conditions. Parametric studies examine the influence of Reynolds number, inlet temperature, flow arrangement, and surface enhancements. The results highlight the trade-off between heat transfer efficiency and pressure loss, emphasizing the importance of design optimization. Overall, the study demonstrates that CFD is a powerful tool for improving the performance of compact heat exchangers while reducing development cost and time.
Priya Natarajan· International Journal of Mod...· 0 citations
This paper presents an evaluation of research results on hydrodynamics and heat transfer during the boiling of refrigerant R22 inside a heat exchange tube with internal longitudinal fins, based on models and correlations proposed by various authors in the available literature. The models demonstrate different approaches to representing correlations for heat transfer calculations, taking into account the influence of hydrodynamic forces such as surface tension, viscosity, and inertia, which affect the motion of two-phase flow in tubes and channels and contribute to the understanding of physical phenomena. The study describes the experimental setup, where heat transfer during refrigerant boiling was investigated under the following operating parameters: heat flux density q = 5, 10, and 20 kW/(m2⋅K), mass flux G = 70, 110, and 200 kg/(m2⋅s), local vapor quality x = 0.01–0.64, and refrigerant saturation temperature ts=15 °C. The influence of heat flux, mass flux, and vapor quality on heat transfer was analyzed, providing valuable insights into heat transfer processes during two-phase refrigerant boiling in tubes and channels. A manufacturing technique for longitudinal fins and unique mandrels for drawing inside copper tubes was developed. Flow visualization revealed stratified, wavy, wavy-slugs, and annular flow regimes. Verification of two-phase flow regimes was performed by comparing experimental results with calculations based on corresponding dependencies from existing flow regime maps. Experimental data were processed using an appropriate methodology for calculating heat transfer coefficients. Based on the obtained results, heat transfer during boiling of two-phase R22 flow inside the finned tube was calculated using 14 models and correlations. The analysis identified models and correlations that most accurately describe the experimental results and can be recommended for engineering practice. Bibl. 31, Tab. 4, Fig. 4.
V. Gorin, L. V. Kolomiets, Y. Trokoz· Energy Technologies & Re...· 0 citations
This paper presents a robust and innovative thermal-hydraulic modeling methodology for compact diffusion-bonded heat exchangers with different channel cross-section geometries, including semi-circular, circular, and rectangular channel configurations. The proposed approach employs the square root of the channel cross-sectional area as the characteristic length scale in heat transfer and fluid flow analyses, enabling a unified treatment of different channel shapes using fundamental thermal and hydraulic correlations. A custom experimental facility was developed to validate the model under laminar, transitional, and early turbulent conditions. Experiments covered Reynolds numbers from 480 to 2683 for the water stream and from 799 to 3145 for the airstream. The heat transfer rate ranged from 1.22 to 4.36 kW, while the pressure drop varied from 154 to 1748 Pa for the cold stream and from 131 to 1191 Pa for the hot stream. The model was also validated against literature data for different channel geometries, showing good agreement with overall root mean square errors of 6.72% for heat transfer rate and 6.56% for pressure drop. The proposed framework provides a simplified and geometry-independent methodology for the preliminary and detailed design of compact heat exchangers across different operating regimes.
Gian M. Gatti, A. Sarmiento, M. Mantelli· Journal of thermophysics and...· 0 citations
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 study numerically investigates the thermal and energy performance of double helical and conical coil heat exchangers using CFD simulations under turbulent flow conditions. The analysis focuses on optimizing key design parameters—coil geometry, coil pitch (16 mm and 20 mm), and hot and cold flow rates (1.5 to 6 LPM)—while evaluating the impact of different working fluids: water, 0.4% CuO, 0.4% Al₂O₃, and 0.4% Fe₂O₃ nanofluids. The Taguchi method (L₁₆ orthogonal array) was employed to identify optimal parameter combinations for maximizing heat transfer and minimizing exergy loss across 16 simulation cases. Simulation results revealed that Nusselt number increases with both cold rates, particularly for Al₂O₃ nanofluid, which demonstrated the highest heat transfer performance. In contrast, exergy loss increases with increasing cold flow rate, while water exhibits the lowest and most stable exergy loss across flow conditions. Additionally, increasing coil pitch was found to reduce the heat transfer coefficient, especially in helical configurations. The Taguchi analysis identified that: The optimum combination for maximum heat transfer is a conical coil with 16 mm pitch, 0.4% Al₂O₃ nanofluid, cold flow rate 6 LPM, and hot flow rate 1.5 LPM. The optimum condition for minimizing exergy loss is a conical coil with 16 mm pitch, water, and both cold and hot flow rates at 1.5 LPM. This study provides a comprehensive framework for enhancing the design of compact coil heat exchangers for energy-efficient applications.
Faisal Iqbal, Prasanjit Das, M. Arman· Engineering· 0 citations
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