BITS Faculty Publications
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Item Flow topology and thermal mechanism in turbulent channel flow with tapered V-shaped baffles(Elsevier, 2025-09) Bhattacharyya, SuvanjanSolar air heaters (SAHs) are widely employed in applications that demand low to moderate temperature thermal energy, such as space heating in residential and commercial buildings, agricultural crop drying, and various industrial processes. A key consideration in the advancement of SAH technology is the enhancement of heat transfer between the absorber surface and the airflow, which directly influences thermal efficiency and overall system performance. In this study, a numerical investigation is conducted to analyze turbulent periodic flow and heat transfer enhancement in a three-dimensional channel fitted with regularly spaced tapered V-shaped baffles (T-VBs). The simulations are performed using the finite volume method in conjunction with the SIMPLE algorithm, and the Generalized k-ω (GEKO) turbulence model is employed to capture the flow dynamics. The analysis examines the effects of varying blockage ratios at their V-back end (BRb = 0.2 to 0.3) and V-apex front (BRf = 0.0 to 0.3) across a range of Reynolds numbers (3,000–20,000). Key dimensionless parameters, including the Nusselt number (Nu), friction factor (f), and thermal performance factor (η), are evaluated. The findings indicate that T-VBs achieve comparable Nusselt numbers to conventional V-shaped baffles (VBs) for Reynolds numbers above 8,000, while consistently demonstrating lower frictional losses. An increased BRb enhances heat transfer, but the impact of BRf varies depending on the Reynolds number and BRf values. Friction losses rise with increasing BRb and BRf, yet remain lower for T-VBs than VBs. A maximal η, 2.49, is achieved at BRf = 0.01 and BRb = 0.2 for Re = 3,000, emphasizing the potential of T-VBs in optimizing thermal performance. The results suggest that T-VBs, with optimized geometries, offer a promising alternative to VBs for enhancing heat transfer and reducing energy consumption.Item Exergy and thermal performance analysis of solar air heater with novel hybrid tape vortex generators for rural applications(Elsevier, 2025-11) Bhattacharyya, SuvanjanIts sustainability, affordability, and environmental compatibility are helping solar energy to attract more worldwide interest. Driving industrial progress and helping economic growth in many areas depend much on it. Among the many solar thermal technologies, Solar Air Heaters (SAHs) are particularly important since they have several uses including agricultural drying, space heating, and seawater desalination. But, because of the bad heat transfer qualities of air, which serves as the working fluid, traditional SAHs frequently have low thermal efficiency. The goal of this work is to improve the thermohydraulic capacity of SAHs by means of innovative and novel hybrid turbulator tape inserts in order to solve this issue. These inserts are meant to create more turbulence and secondary flow, therefore improving heat transfer while keeping reasonable pressure losses. With air as the working medium, circular tube uniformly heated under constant heat flux was used for experimental studies. Covering full turbulent flow regimes, the performance was examined over the Reynolds number (Re) fluctuated between 10,794 and 73,644. The findings show an extraordinary 89% increase in Nusselt number (Nu), suggesting much better convective heat transfer (HT). At the same time, a modest 35% rise in friction factor (f) was noted, suggesting a nice balance between losing pressure and improving heat transfer. These results highlight the possibility of hybrid tape inserts as a quick passive method to increase the thermal performance of SAHs, therefore providing interesting consequences for energy-efficient solar thermal systems. The novelty of this investigation is the experimental implementation of a hybrid wavy with spring inserts of tape type, which delivers increased secondary flows and augmented convective heat transfer. In contrast to conventional inserts, the hybrid design can achieve significant enhancements in thermal and exergy performance with lower pressure penalties. As a consequence, this novel shape observed an impressive 89% growth in the Nusselt number (Nu), and it could be very useful for a real life engineering applications pertaining to energy conversion systems in rural area.Item Evaluating the heat transfer and pressure drop in the transitional flow regime for a horizontal circular tube fitted with wavy-tape inserts(Elsevier, 2024-02) Bhattacharyya, Suvanjan; Soni, Manoj KumarMuch research is available to support the thermo-hydraulic characteristics of heat exchanger tubes in laminar and turbulent flow regimes. However, very little work is available to support the thermohydraulic characteristics of heat exchangers in transition flow regimes, especially in turbulators. Therefore, this research experimentally evaluated the heat transfer and pressure drop characteristics of a circular tube fitted with wavy-tape inserts in the transition flow regime. Experiments were conducted in a circular tube having an internal diameter of 20 mm and a length of 2000 mm and the Reynolds number varied from 533 to 7002. The Nusselt number and friction factor for a smooth tube are validated by comparison with published research works in the laminar and turbulent flow regimes. A total of nine wavy tape inserts with different wave and width ratios were investigated. To determine the variation of Nusselt number and friction factor, three constant heat fluxes ( 1, 2, and 3 kW/m2) were applied to the test section. The laminar, transition, and turbulent regimes were marked and identified by using the linear best-fit line method for all the cases considered during the investigation. The results obtained from the study showed a shift in the boundaries of laminar, transition, and turbulent flow regimes. For smooth tube with 1 kW/m2 heat flux, the transition starts and ends at Reynolds number 2202 and 3 804, respectively. It was also revealed that the onset of transition occurred further earlier when tapes were used. The boundaries of transition also shifted with a change in the constant heat flux condition. For wavy tape having w = 0.75, d = 0.8, the transition begins at Reynolds number 2 193, 2 021, 2029 and ends at 4 016, 3 997, 3989 for heat flux 1, 2 and 3 kW/m2, respectively. The transition began earlier for lower values of heat flux, while for higher values, the transition limit was delayed compared with that of lower heat flux. The boundary of transition also shifted with wave ratio and width ratio. An increase in wave and width ratios altogether delayed the start and end of the transition. Correlations were also developed to predict the Nusselt number and friction factor in laminar and turbulent flow regime.Item Turbulent Heat Transfer Augmentation in a Square Channel by Augmenting the Flow Pattern with Novel Arc-Shaped Ribs(MDPI, 2023-03) Bhattacharyya, SuvanjanSolar water heaters (SWHs) are widely used in HVAC industries as well as in households for different heating purposes. The present numerical simulation focuses on the investigation of the thermo-hydraulic performance of novel semi-arc-rib SWHs. Semi-arc-shaped ribs in the square channel of the absorber plates with different pitch and height ratios are investigated in this study. The present novel modification disturbs the boundary layers by generating vortices, and thus, enhanced fluid mixing takes place. Water with a Reynolds number (Re) ranging from 4000 to 25,000 is used as a working fluid, and a 1.0 kW/m2 heat flux is imposed on the tube wall. The results demonstrate a significant increase in the Nusselt number (Nu) as the fluid layers localize behind each rib near the absorber plates, and at the same time, the number of swirls generated inside the tube and the frictional losses both increased noticeably. To ensure the effectivity of the present novel SWH geometry, the thermo-hydraulic performance (η) for each case was calculated, and it was found that in all the cases, it was greater than unity, which signifies that the present semi-arc-rib SWH is promising and can be used in HVAC industrial and household applications.Item Thermohydraulic characteristics of magnetic nanofluid in mini channels under the influence of an external magnetic field(Elsevier, 2023) Bhattacharyya, SuvanjanEngineers and designers are increasingly challenged to maximize processing speed inside a constricted form factor as electronic components increasingly become smaller. Smaller form factors need downsizing of the tools used to distribute that heat, and faster processors entail increasing power usage, which creates additional heat. These factors compel creative engineers and designers to develop systemic solutions in which every factor in the power equation of a device is optimized. Hence, in the present work, results of numerical simulations of mini-channel heat sinks are analyzed and compared. The influences of design, inclination angle, magnetic field, and nanofluid on the thermal and flow performance are evaluated numerically. The results obtained from the investigation shows increments in the Nusselt number with an increase in magnetic field intensity and Reynolds number. The vortices formed in the fluid domain provide intense fluid mixing. The average fluid temperature rises and the thickness of the boundary layer increases and the Nusselt number further decreases in the region of the magnetic field. The magnetic field's intensity determines how big the vortex will be; the stronger the magnetic field, the faster the vortex will swirl which results in the formation of secondary vortices, which, in turn, contribute to intense mixing of fluid. The vortices become larger and combine to create a single vortex when the magnetic field strength increases, and this pattern holds true for greater magnetic field strengths. The findings clearly demonstrate that the reduction in frictional pressure drop exceeds the rise in pressure drop due to vortex formation, even though there must be an increase in pressure drop owing to vortex formation. When the flow blockage is greatest, the pressure drop is also greatest. The thermal performance factor for all the configurations is evaluated. Except for 1200 G, for all other magnetic intensities and Reynolds number, the thermal performance is above unity.Item Turbulent Heat Transfer Augmentation in a Square Channel by Augmenting the Flow Pattern with Novel Arc-Shaped Ribs(MDPI, 2023) Bhattacharyya, SuvanjanSolar water heaters (SWHs) are widely used in HVAC industries as well as in households for different heating purposes. The present numerical simulation focuses on the investigation of the thermo-hydraulic performance of novel semi-arc-rib SWHs. Semi-arc-shaped ribs in the square channel of the absorber plates with different pitch and height ratios are investigated in this study. The present novel modification disturbs the boundary layers by generating vortices, and thus, enhanced fluid mixing takes place. Water with a Reynolds number (Re) ranging from 4000 to 25,000 is used as a working fluid, and a 1.0 kW/m2 heat flux is imposed on the tube wall. The results demonstrate a significant increase in the Nusselt number (Nu) as the fluid layers localize behind each rib near the absorber plates, and at the same time, the number of swirls generated inside the tube and the frictional losses both increased noticeably. To ensure the effectivity of the present novel SWH geometry, the thermo-hydraulic performance (η) for each case was calculated, and it was found that in all the cases, it was greater than unity, which signifies that the present semi-arc-rib SWH is promising and can be used in HVAC industrial and household applications.Item Augmented thermal performance in a non-uniform heat flux circular tube with twisted tape insert using hybrid nanofluid(EDP Sciences, 2021-11) Bhattacharyya, SuvanjanThe influence of non-uniform heat transfer on a circular tube with a twisted tape insert using nanofluid (NF) is examined. The circular tube had an inner diameter 20 mm, with 0.5 mm thickness and 2 m of length. Wall heat flux conditions were examined for Reynolds number ranging from 5 000 to 25 000. Heat flux distribution included partial heating at different circumferential positions. Water was used as a base fluid, while single and multi-nano particles are used for simple and hybrid nanofluids (HNF). The goal of this study is to augment the thermal performance by incorporating non-uniform heating, using a twisted tape insert and by using nanoparticle of different volume fraction. NF act as a fluid additive and twisted tape act as a turbulence promoter and they enhance the heat transfer rate. However, major disadvantage in this investigation is the pressure drop incurred due to the twisted tape and NFs. Hence, a series of simulation are carried out to find out the optimum configuration of the set-up for which heat transfer will be enhanced with minimum pressure drop.Item CPU heat sink cooling by triangular shape micro-pin-fin: Numerical study(Elsevier, 2018) Bhattacharyya, SuvanjanThe cooling capability of heat sinks is important for a central processing unit (CPU). In this work, simulation has been done to study heat transfer (HT) in a heat sink (HS) mounted on the triangular cylinder chip of a CPU is studied, to explore the thermofluid behaviour of the designed micro-pin-fin heat sink. Air cooling methods are used for heat extraction. This numerical work considers the effects of inlet turbulence intensity (TI) and fin diameter (D) of the micro-pin-fin on the performance of the heat sink. Turbulent SST model is applied to capture turbulence regime in the system. The heat transfer and pressure coefficient were obtained at different Reynolds number (Re) (i.e. different inlet velocities). As shown in this study, the Nusselt number (Nu) increases with increase in air flow velocity which enhance the heat extraction from CPU.Item Influence of material on heat transfer and fluid flow in the pillow-plate heat exchanger(Springer, 2023-04) Soni, Manoj Kumar; Bhattacharyya, SuvanjanThe traditional heat exchanger has some limitations in thermal efficiency compared to the pillow plate heat exchanger (PPHE). In this way, the PPHE can be an efficient alternative and a good substitute. It is the combination of many pillow-plate channels organized in corresponding to each other. In this paper, the first time conjugate heat transfer (CHT) and transition SST model is used on the pillow plate channel using copper and steel as an outer channel, and the working fluid internally flows through the channel. We can see the primary and recirculation flow from the temperature field, and the temperature gradient increases behind the welding spot and near the inlet and outlet region in both metal sheets. The results showed that copper could be an excellent alternative solution for heat transfer. The thermal performance of copper is higher than steel. In addition, the simulation results were validated with previous experimental results and found better consistency of Nusselt number.Item Single-Phase Fluid Flow and Heat Transfer Characteristics in Pillow-Plate Heat Exchanger: A Numerical Study(Springer, 2023-04) Soni, Manoj Kumar; Bhattacharyya, SuvanjanThe pillow-plate heat exchanger (PPHE) is an excellent substitute for the traditional heat exchanger; in manufacturing industries. In this paper, a numerical investigation is carried out to predict and accurately analyze the fluid flow and heat transfer characteristics in the pillow-plate used for the pillowplate heat exchanger. It is observed that the recirculation region is essential to direct bearing of heat transfer in PPHE compared to the smooth channel. Further, the computational study is based on geometrical parameters such as welding spot and internal hydraulic diameter. The numerical results are validated against some experimental and numerical results. Based on the computational results, the heat transfer enhancement increased significantly and the temperature gradient is increased behind the welding spot. Compared to smooth surface, the thermal performance is more efficient at a lower Reynolds number than a higher one.