Optimizing Heat Transfer and Pressure Drop in Shell-and-Tube Heat Exchangers: A Comparative Study of Segmental and Helical Baffles

Shell-and-tube heat exchangers (STHE) are widely used in various industries due to their simple design, high versatility, and effectiveness in heat transfer. These exchangers operate on the principle of heat transfer between two fluids at different temperatures, transferring thermal energy from the hotter to the cooler fluid, resulting in cooling of the hotter fluid and heating of the cooler one [1]. The flexibility of STHE allows use in chemical engineering, power generation, petroleum refining, refrigeration, and the food industry [2]. Compared to other heat exchangers, shell-and-tube designs are simpler to manufacture, cost-effective, and adaptable to various operational needs [3, 4]. Over 30% of heat exchangers in operation today are shell-and-tube types, highlighting their continued importance [5, 6].

Critical component in STHE design and performance is the baffle, which regulates fluid flow, enhances heat transfer, and prevents tube vibrations. Baffles support the tube bundle, direct shell-side fluid flow, and create turbulence, increasing the heat transfer coefficient by improving contact between hot and cold fluids [7]. Traditionally, single segmental baffles (SB) are commonly used, forcing fluid to flow in a zigzag pattern, promoting turbulence, local mixing, and improving heat transfer. However, SB have inherent limitations affecting efficiency and operational costs [8].

The performance of STHE is significantly influenced by baffle design, with helical baffles (HB) offering advantages over SB. HB eliminates dead zones, reduces pressure drops, and minimizes tube bundle vibrations, improving heat transfer efficiency [9]. Studies by Kral et al. [10] and Gao et al. [11] showed that adjusting the HB angle optimizes heat transfer while controlling pressure drop, with the latter using the second law of thermodynamics to assess flow resistance. Studies by Almulla et al. [12] also indicate that optimized baffle configurations lead to substantial operational improvements. Comparative analyses by Sun et al. [13] consistently show HB outperforming SB and other baffle configurations in heat transfer efficiency and pressure drop characteristics. Numerical investigations by Yang et al. [14] and Li and Kottke [7] confirm the superior performance of HB. Additionally, Pal et al. [15] found that complex flow patterns significantly impact STHE efficiency. Other studies, such as those by Xiao et al. [16], contributed to understanding the role of crossover temperature and the effect of the Prandtl number on heat transfer. These studies highlight the crucial role of baffle configuration in optimizing STHE’s thermal and hydraulic performance, demonstrating efficiency gains achievable through properly configured HB.

In response to these challenges, the heat exchanger industry has increasingly adopted alternative baffle designs, such as HB, to improve both heat transfer and operational efficiency. HB facilitates a more uniform fluid flow, reducing issues with stagnant zones and flow separation [17]. Flow simulations of STHE with HB show continuous helical flow, enhancing fluid mixing and improving the heat transfer coefficient while reducing the pressure drop compared to SB [17]. Reducing stagnant zones also leads to lower fouling rates and minimizes potential erosion and corrosion within the shell, improving the heat exchanger’s lifespan and overall performance.

The design of HB, particularly pitch, plays a crucial role in determining STHE's thermo-hydraulic performance. Several studies have shown that adjusting HB pitch can optimize heat transfer while minimizing pressure drop. Zhang et al. [9] found that varying pitch influences heat transfer and pressure drop, with smaller pitches increasing turbulence and heat transfer at the cost of higher pressure drops. Larger pitches reduce turbulence and pressure drop but may reduce thermal performance. These findings align with Zhang et al. [18], who showed pitch variation directly impacts flow behavior and thermal-hydraulic outcomes. Given these trade-offs, optimizing HB pitch is essential to balance heat transfer efficiency and operational performance, minimizing energy consumption and operational costs.

Growing interest in alternative baffle designs, such as helical and trefoil-hole baffles, arises from the need to optimize STHE performance in terms of heat transfer and operational costs. This is particularly important in industries where energy consumption and operational costs are significant. In SB heat exchangers, high pressure drops increase pumping power, elevating operational costs and reducing system efficiency [14]. Tanujaya et al. [19] and Naqvi et al [20] noted that SB restricts flow and increases hydraulic losses. In contrast, helical and trefoil-hole baffles significantly reduce pressure drops, enhance fluid mixing, and improve heat transfer, making them a more energy-efficient choice for industrial heat exchangers [4, 13]. Additionally, variations in HB pitch improve STHE operational sustainability and thermo-hydraulic performance [21].

Despite extensive studies on STHE with HB, several limitations remain. Most studies focus on global performance indicators like average heat transfer coefficient or pressure drop, without fully analyzing the flow mechanisms behind the trade-off between thermal enhancement and hydraulic penalty. Many comparative studies assess different baffle configurations under varying geometric or operational conditions, complicating the identification of optimal designs from an energy-efficiency perspective. Systematic evaluations directly linking HB pitch variation to flow structure evolution, thermo-hydraulic performance, and performance evaluation factor (PEF) under identical operating conditions are still limited.

To address these gaps, the present study provides a controlled comparative numerical investigation of segmental and HB configurations using identical geometric and operating parameters. The study systematically evaluates the influence of HB pitch (40, 50, and 60 mm) on flow characteristics, pressure drop, heat transfer coefficient, and overall thermo-hydraulic efficiency using the PEF. By linking flow structure behavior to observed thermo-hydraulic performance, this work offers a clearer mechanistic interpretation of the trade-off between heat transfer enhancement and hydraulic resistance, providing practical guidance for energy-efficient baffle design in industrial STHE.

This section presents the results obtained from the numerical simulations performed on four different baffle configurations for STHE: SB and HB with pitch distances of 40 mm, 50 mm, and 60 mm. The results are discussed regarding the flow field characteristics, pressure drop, heat transfer coefficient, and PEF across different mass flow rates.

3.1 Flow field characteristics on the shell side

The flow field characteristics for each baffle configuration were analysed using CFD simulations. Figure 7–10 presents the velocity streamlines and flow patterns for the four configurations: SB and HB with 40 mm, 50 mm, and 60 mm pitch distances.

For the SB configuration (Figure 7), the axial flow is forced to change direction due to the baffle cut, creating a zigzag flow pattern. This zigzag flow is intended to induce turbulence, enhancing heat transfer, as widely reported in the literature [18]. However, the abrupt changes in flow direction also lead to significant recirculation and the formation of stagnation zones near the back of the baffle plates, consistent with findings by Vukić Mića et al. [23] and Pamuk [24]. These stagnation zones reduce fluid velocity and contribute to higher pressure drops within the shell. The fluid velocity decreases significantly as it moves against gravity, leading to a situation where the fluid can become nearly stagnant, especially at lower mass flow rates. This pattern contributes to the high pressure drop observed in systems with SB, as the fluid flow is interrupted and disturbed by the geometry of the baffles. Although this configuration increases the turbulence intensity and heat transfer coefficient ($\propto_s$), the resultant pressure drop ($\Delta \mathrm{P}$) is considerably high.

Figure 7. Flow field characteristics of the segmental baffle (SB)

Figure 8. Flow field characteristics of helical baffle (HB) with baffle pitch 40 mm

Figure 9. Flow field characteristics of helical baffle (HB) with baffle pitch 50 mm

Figure 10. Flow field characteristics of helical baffle (HB) with baffle pitch 60 mm

In contrast, the HB configurations (Figures 8–10) generate a more uniform and continuous flow pattern due to the spiral motion imposed on the shell-side fluid. This spiral flow enhances fluid velocity distribution and significantly reduces the formation of stagnation zones, as demonstrated by Wen et al. [25] and De et al. [26]. The improved circulation allows the fluid to move more evenly around the tube bundle, resulting in better mixing and enhanced heat transfer performance, consistent with observations by Song [27]. The effect of pitch variation is also evident: at smaller pitch distances (40 mm), higher local fluid velocities intensify turbulence and mixing, aligning with findings from Rahmah et al. [28]. As the pitch increases to 50 mm and 60 mm, the flow becomes more uniform with reduced turbulence intensity, leading to lower pressure drops across the shell side, as reported by Yousfi [29]. Overall, HB configurations, particularly at a 60 mm pitch, promote more stable flow behavior and achieve efficient heat transfer with reduced flow resistance compared to the SB configuration.

3.2 Pressure drop

Pressure drop (ΔP) is a crucial performance parameter for STHE, as it directly affects the pumping power required to maintain fluid flow. Figure 11 presents the pressure drop for each baffle configuration as a function of mass flow rate.

Figure 11. Pressure drop (ΔP) of the variation baffle versus mass flow rate

As expected, the SB exhibits the highest pressure drops across all mass flow rates. This is due to the flow disturbances and flow separation caused by the sharp directional changes imposed by the SB. These sharp flow changes result in large recirculation zones and significant turbulence, leading to higher pressure losses. Such characteristics align with findings reported in Lei et al. [30] and Zhang et al. [18]. The pressure drop increases significantly with the mass flow rate, indicating that the pumping energy required to overcome flow resistance is directly proportional to the flow rate. The SB configuration exhibits a pressure drop that is considerably higher than that of the HB, as expected from previous studies [14].

For the HB, the pressure drop decreases as the baffle pitch increases. The configuration with a 40 mm pitch shows the highest pressure drop due to the tighter spacing between the baffles, which increases flow resistance. However, this configuration also provides the highest heat transfer rate, as discussed in the following section. As the baffle pitch is increased to 50 mm and 60 mm, the pressure drop is significantly reduced. The 60 mm pitch configuration produces the lowest pressure drop among the HB designs, reflecting smoother flow transitions and lower resistance to flow. This result supports the findings of Zhang et al. [9], who showed that HB reduces pressure drop compared to SB while maintaining high heat transfer efficiency.

Interestingly, the increase in pressure drop with the 40 mm pitch HB configuration is particularly prominent, with increases of 149.14%, 164.87%, 169.57%, and 168.86% compared to the 60 mm pitch configuration. This higher pressure drop is due to the tighter spacing between the baffles, which increases flow resistance [11]. Thus, while a smaller pitch enhances heat transfer by promoting more intense turbulence, it also leads to higher pressure drops, necessitating a careful optimization of pitch distance.

3.3 Heat transfer coefficient

The heat transfer coefficient ($\propto_s$) is a key measure of the heat exchanger's thermal performance. As shown in Figure 12, the heat transfer coefficient increases with increasing mass flow rate for all baffle configurations [31]. This trend is associated with the increase in Reynolds number, which enhances turbulence intensity, reduces the thickness of the thermal boundary layer, and improves convective heat transfer on the shell side.

Figure 12. Heat transfer coefficient ($\propto_s$) for variation of baffle configurations versus mass flow rate

The HB with a 40 mm pitch provides the highest heat transfer coefficient, which is a direct result of the intense turbulence and fluid mixing induced by the smaller pitch [18, 30]. On the microscopic level, the tighter pitch generates a continuous helical flow with strong secondary swirling motions, increasing wall shear stress, and continuously renewing the near-wall fluid layer. This mechanism suppresses thermal boundary-layer growth along the tube surface and maintains a high local temperature gradient, significantly enhancing convective heat transfer [32]. However, the increased turbulence and flow velocity also cause a higher pressure drop, making the 40 mm pitch configuration less favorable in terms of energy efficiency and operational cost [33].

The 50 mm and 60 mm pitch HB exhibit lower heat transfer coefficients, with average increases of 4.23% and 1.42%, respectively, compared to the SB configuration. The reduction in heat transfer performance with increasing pitch is attributed to weakened secondary flow structures and partial redevelopment of the thermal boundary layer between successive baffles [34]. Although the 60 mm pitch configuration maintains a heat transfer coefficient comparable to that of the SB, it achieves a significantly lower pressure drop, indicating smoother and more uniform flow behavior. In contrast, SB induces localized turbulence through abrupt flow redirection but generates recirculation and dead-flow zones, resulting in inferior thermohydraulic performance for a given hydraulic penalty.

3.4 Performance evaluation factor

The PEF was calculated by comparing the heat transfer rate ($\dot{\mathrm{Q}}$) and pressure drop ($\propto_s$) for each baffle configuration. These two parameters are closely linked, and their combined effect determines the overall efficiency of the heat exchanger. In an ideal STHE design, higher heat transfer rates ($\dot{\mathrm{Q}}$) and lower pressure drops ($\propto_s$) lead to better performance, with lower energy consumption and operational costs. Therefore, the PEF serves as an important metric for evaluating the efficiency of each baffle configuration [12, 27].

As seen in Figure 13, the HB with a 60 mm pitch exhibited the highest PEF, demonstrating the most efficient performance. This is because the 60 mm pitch configuration achieved a high heat transfer rate ($\dot{\mathrm{Q}}$) while maintaining a very low pressure drop ($\Delta \mathrm{P}$), making it the most energy-efficient option. The 60 mm pitch HB configuration strikes the best balance between heat transfer efficiency and pressure drop, leading to lower operational costs due to reduced pumping power requirements [13, 35].

In contrast, the 40 mm pitch HB showed the lowest PEF. While it provided the highest heat transfer rate ($\dot{\mathrm{Q}}$), the significant pressure drop caused by the tighter pitch resulted in a lower overall performance. The high pressure drop (ΔP) with the 40 mm pitch configuration leads to increased energy consumption, as more pumping power is required to overcome the flow resistance, thus making it less efficient compared to other configurations.

The PEF analysis also revealed significant performance improvements of the HB compared to the SB. The HB with 50 mm and 60 mm pitches achieved 28.59% and 48.49% higher PEF values, respectively, than the SB configuration. This indicates that HB outperforms SB in both heat transfer efficiency and pressure drop reduction, making them a more energy-efficient choice for industrial applications [36].

On the other hand, the 40 mm pitch HB exhibited a 27.34% decrease in PEF compared to the 50 mm and 60 mm pitch configurations. Although it provides the highest heat transfer, the associated increase in pressure drop reduces its overall efficiency. This highlights the inherent trade-off between heat transfer and pressure drop, where smaller baffle pitches improve heat transfer but increase flow resistance, leading to higher operational costs.

The PEF analysis thus underscores the importance of baffle pitch optimization in STHE. The 60 mm pitch HB emerged as the most optimal configuration, providing the best overall balance of heat transfer efficiency and low pressure drop, which is essential for improving energy efficiency and reducing operational costs in industrial heat exchangers.

Figure 13. Shell side performance evaluation factor (PEF) of variation baffle versus mass flow rate

Beyond overall thermo-hydraulic efficiency, the performance trends reflected by the PEF provide relevant insights into practical engineering implications for industrial operation. In addition to thermo-hydraulic performance, economic aspects should also be considered when selecting baffle configurations. Although a quantitative cost–benefit analysis was not conducted due to the lack of proprietary industrial cost data and the scope of this CFD-based study, a qualitative assessment can be discussed. SB generally has lower manufacturing costs; however, its higher pressure drop leads to increased pumping power requirements and operational energy costs [37, 38].

HB may involve higher fabrication complexity and initial costs, but their significantly lower pressure drop—particularly for larger pitch distances—can reduce long-term operating and maintenance costs. In particular, the HB with a 60 mm pitch provides a favorable balance between heat transfer performance and pressure drop, indicating promising economic potential when lifecycle operational efficiency is considered. The highest PEF obtained for this configuration is associated with smoother and more continuous shell-side flow characteristics, lower pressure fluctuations, and reduced flow interruption compared to the SB and HB with smaller pitch distances. Such flow conditions play an important role in minimizing stagnant zones, which are known to accelerate particle deposition and fouling during long-term operation.

In addition, the more gradual flow redirection provided by the larger-pitch HB potentially reduces the risk of localized erosion–corrosion caused by high-velocity fluid impingement near baffle edges. From an operational stability perspective, the more stable and continuous flow pattern also contributes to reduced pressure fluctuations and flow-induced vibrations, thereby enhancing mechanical reliability and extending the service life of STHE. Although fouling, corrosion, and long-term stability were not quantitatively evaluated in this study, the simulated flow behavior provides a strong basis for concluding that optimized HB configurations offer advantages not only in energy efficiency but also in operational reliability and sustainability for industrial applications [39].

The authors would like to express their sincere gratitude to Kementerian Pendidikan Tinggi, Kebudayaan, Riset dan Teknologi Republik Indonesia for funding this fundamental research (Contract number: 01768/PL8/AL.04/2024). The authors also extend their deepest appreciation to Universitas Pembangunan Nasional Veteran Jakarta and Politeknik Negeri Bali for their valuable resources and facilities throughout this study.