BITS Faculty Publications
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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 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.Item Thermal performance enhancement in heat exchangers using active and passive techniques: a detailed review(Springer, 2022-02) Soni, Manoj Kumar; Bhattacharyya, SuvanjanThe objective of this article is to study the work carried out in heat transfer augmentation using active and passive techniques. A comprehensive summary of the work is highlighted to showcase the strength of these techniques in terms of enhancement in heat transfer. In this work, research studies done in the area of electrohydrodynamic, magnetic field, corona wind, vortex generators, tape and coil inserts, roughness, and modified duct were reviewed and an attempt has been made to make a common platform on which the performance enhancement has been compared and presented. It was found out that passive methods are comparatively more investigated than active methods due to their safe and sound operation along with no additional requirement of power. Result shows that duct modification is an effective and efficient way for heat transfer enhancement (HTE). Based on the literature studied, more emphasis must be focussed on the usage of HTE methods in combination to get the advantages of both the methods and they should complement each other in the best possible way. On comparing the active and passive way of THE, results with active methods are more appreciable. However, passive techniques gain more momentum due to ease of operation and low cost of equipment. Use of passive augmentation techniques, i.e. vortex generators, artificial roughness, etc., changes flow pattern significantly that helps in the heat transfer augmentation. Although understanding of fluid flow behaviour is very essential and helps in the cause of the heat transfer augmentation that will further help in using compound techniques, altering the duct’s surface using ribs, dimples, roughness, etc., shows the thermal performance enhancement of more than 200% when the results were compared with the plain channel. The modified duct may be combined with any other passive augmentation technique which will further lead to performance enhancement.Item Thermal performance investigation of earth air tunnel heat exchanger coupled with a solar air heating duct for northwestern India(Elsevier, 2015-01) Soni, Manoj KumarIn the present research thermal performance of earth air tunnel heat exchanger (EATHE) coupled with a solar air heating duct has been experimentally evaluated for arid climate of Ajmer city of northwestern India, during winter season. An attempt has been made to enhance the heating capacity of EATHE system by coupling it with a solar air heating duct at the exit end. Results show that the air which comes out of coupled EATHE system is relatively hotter than the air supplied by the stand alone EATHE system. It was found that the heating capacity of EATHE system got increased by 1217.625–1280.753 kWh when it was coupled with solar air heating duct with a substantial increase in room temperature by 1.1–3.5 °C. The COP of the system also increased up to 4.57 when assisted with solar air heating duct. Therefore, the heating capacity of EATHE can be significantly increased by coupling it with solar air heating duct.