Thermalhydraulics & Gasification Laboratory

Dr. Vijay Kumar Mishra

Publications in International Journals (from the thesis)

1. VK Mishra, SC Mishra and DN Basu (2015), Combined Mode Conduction and Radiation Heat Transfer in a Porous Medium and Estimation of Optical Properties of the Porous Matrix, Numerical Heat Transfer Part A, Vol. 67, No. 10, pp. 1119-1135, DOI: 10.1080/10407782.2014.955358
2. VK Mishra, SC Mishra and DN Basu (2016), Simultaneous Estimation of Properties in a Combined Mode Conduction and Radiation Heat Transfer in a Porous Medium, Heat Transfer - Asian Research, Vol. 45, No. 8, pp. 699-713, DOI: 10.1002/htj.21184
3. VK Mishra, SC Mishra and DN Basu (2017), Simultaneous Estimation of Parameters in Analyzing Porous Medium Combustion - Assessment of Seven Optimization Tools, Numerical Heat Transfer Part A, Vol. 71, No. 6, pp. 666-676, DOI: 10.1080/10407782.2016.1139908
4. VK Mishra, SC Mishra and DN Basu (2017), Simultaneous Estimation of Four Parameters in a Combined Mode Heat Transfer in 2-D Porous Matrix with Heat Generation, Numerical Heat Transfer Part A, Vol. 71, No. 6, pp. 677-692, DOI: 10.1080/10407782.2016.1139910

Publications in International Conference Proceedings (from the thesis)

1. VK Mishra, SC Mishra and DN Basu (2013), Heat Transfer Analysis Combined with Estimation of Optical Properties of a Porous Radiant Burner, Proc. 22^nd National and 11^th International ISHMT-ASME Heat and Mass Transfer Conference, Kharagpur, India, December 28-31, Paper ID HMTC1300078
2. VK Mishra, SC Mishra and DN Basu (2014), Combined Mode Conduction and Radiation Heat Transfer in a 2-D Porous Medium and Simultaneous Estimation of its Optical Properties, Proc. 11^th International Conference on Flow Dynamics, Sendai, Japan, October 08-10, pp. 356-357
3. VK Mishra, SC Mishra and DN Basu (2015), Estimation of a parameter in a combined mode heat transfer in a two layered 2D-axisymmetric porous matrix, Proc. 12^th International Conference on Flow Dynamics, Sendai, Japan, October 27 – 29
4. VK Mishra, SC Mishra and DN Basu (2015), Combined Mode Conduction-Radiation Heat Transfer in 2-D Cylindrical Porous Medium and Simultaneous Estimation of its Properties, Proc. 23^rd National and 1^st International ISHMT-ASTFE Heat and Mass Transfer Conference, Trivandrum, India, December 17-20, Paper ID IHMTC2015-998
5. VK Mishra, SC Mishra and DN Basu (2015), Simultaneous estimation of properties of a 1-D porous radiant burner, Proc. 23^rd National and 1^st International ISHMT-ASTFE Heat and Mass Transfer Conference, Trivandrum, India, December 17-20, Paper ID IHMTC2015-1000
6. VK Mishra and DN Basu (2017), Heat Transfer Characteristics of 2D-axisymmetric Porous Radiant Burner, Proc. 24^th National and 2^nd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2017), Hyderabad, India, December 27-30 (Book Chapter in: ISHMT digital library ISSN: 2688-7231 )

Abstract of Thesis

Development of thermal systems like a porous radiant burner, heat exchangers, insulations, etc., quantitative knowledge of heat and/or mass transfer, temperature field are essential. With geometric details, thermo-physical and optical properties, and initial and boundary conditions known, the desired results, viz., temperature and heat flux distributions are known by numerically solving a set of governing equations. However, when a thermal system is designed, a priori knowledge of some or all of the geometric parameters, and thermos-physical and optical properties of the material, and even initial and/or boundary conditions may not be known. Experimental route to optimize these parameters with trial and error approach for the desired outcome is not scientific. Recourse of an inverse analysis is the most preferred option by the scientific community. With thermo-physical properties and initial and boundary conditions known, calculations of the desired velocity field, temperature field or heat and mass flow rates, come under solving a direct problem. However, when either of the desired quantities (temperature, velocity fields, heat and mass transfer rates), and one or more of the properties or initial or boundary conditions are unknown, problem becomes an inverse one. In the direct problem, causes are known, and getting the outcomes are straightforward. On the contrary, in inverse problems, the outcome is known, but not the cause(s). Estimation of cause(s) is relatively, a difficult task. Mathematically, inverse problems are ill-posed. With even a slight variations in governing parameters, solution goes astray. Over the last five decades, many researchers have studied heat and mass transfer in porous media. They have considered different geometric and thermal configurations. However, study on estimation of parameters in a combined mode conduction and radiation heat transfer with or without combustion is scarce. With its application in porous radiant burners in mind, the present work, is aimed at heat transfer analysis as well as estimation of thermo-physical and optical properties in a combined mode conduction and radiation heat transfer in porous media. With aforementioned objective in mind, in the present work, different configurations like single stage, two stage are considered. Different geometries like 1D planar, 2D rectangular, 2D axisymmetric cylindrical are also considered. Also, different optimization algorithms in the inverse analysis are used, such as genetic algorithm, global search algorithm, pattern search algorithm, simulated annealing etc.

Dr. Daya Shankar

Publications in International Journals (from the thesis)

1. D Shankar, DN Basu and M Pandey (2017), Development and Analysis of a Novel Scaling Methodology for Stability Appraisal of Supercritical Flow Channels, Nuclear Engineering and Design, Vol. 323, pp. 46-55, DOI: 10.1016/j.nucengdes.2017.07.030
2. D Shankar, M Pandey and DN Basu (2018), Parametric Effects on Coupled Neutronic-Thermohydraulic Stability Characteristics of Supercritical Water Cooled Reactor, Annals of Nuclear Energy, Vol. 112, pp. 120-131, DOI: 10.1016/j.anucene.2017.10.008
3. D Shankar, M Pandey and DN Basu (2024), Nonlinear Analysis of Coupled Neutronic-Thermohydraulic Stability Characteristics of Supercritical Water-cooled Reactor, Annals of Nuclear Energy, Vol. 195, pp. 110197, DOI: 10.1016/j.anucene.2023.110197

Publications in International Conference Proceedings (from the thesis)

1. D Shankar, DN Basu and M Pandey (2013), Study on Design of Scaled Down Test Facilities for Investigation of Instabilities in Supercritical Water Reactor, Proc. 21^st International Conference on Nuclear Engineering (ICONE21), Chengdu, China, July 29 – August 02, Paper No. ICONE21-16638
2. D Shankar, M Pandey and DN Basu (2018), Coupled-Neutronic-Thermalhydraulic Stability Appraisal of Supercritical Forced Flow Channels Following Lumped Parameter Approach, Proc. 16^th International Heat Transfer Conference (IHTC-16), Beijing, China, August 10-15, Paper ID IHTC16-23961
3. D Shankar, DN Basu and M Pandey (2019), Neutronics-Coupled Thermal Hydraulic Calculation of SCWR under Seismic-wave Acceleration, Proc. 25^th National and 3^rd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2019), Roorkee, India, December 28-31, Paper ID IHMTC2019-NSA-830

Abstract of Thesis

Present thesis work primarily focuses on the analysis of flow instability in one of the most powerful concepts under Generation-IV nuclear reactors technology, namely, Supercritical water-cooled reactor (SCWR). Safety is the primary concern in the any nuclear reactors. Flow instabilities are one of a kind on which the current researches are going on. The reason behind that is the large density difference of the fluid through the coolant channel. Therefore, a downscaled model is required to study the complex phenomena in laboratory conditions; hence a scaled method is proposed here which is useful for the study of both the natural as well as the forced circulation system. For further analysing about the stability of the system, a simple but quite effective model has been developed as the Lumped Parameter Model (LPM). Using this model, a linear and nonlinear stability analysis have been done for the various parametric conditions. Moreover, the stability analysis due to the seismic effects on SCWR has also been considered by using the same LPM. Two types of seismic wave model have been taken into account for the analysis, first the sinusoidal acceleration and the other more realistic Kanai–Tajimi model which is used for more accurate simulation of the seismic wave. These methods are first time introduced in the SCWR.

Dr. Milan Krishna Singha Sarkar

Book Chapter (from the thesis)

1. DN Basu and MKS Sarkar, Supercritical Natural Circulation Loop: A Technology for Future Reactors, in: L Chen and Y Iwamoto (eds.) Advanced Applications of Supercritical Fluids in Energy Systems, IGI Global, Hershey PA, USA, Ch. 6, pp. 188-214, 2017, DOI: 10.4018/978-1-5225-2047-4.ch006
2. T Srivastava, P Sutradhar, MKS Sarkar and DN Basu, Supercritical Natural Circulation Loop: A Technology for Future Reactor, in: L Chen (eds.) Handbook of Research on Advancements in Supercritical Fluids Applications for Sustainable Energy Systems, IGI Global, Hershey PA, USA, Ch. 9, pp. 338-369, 2021, DOI: 10.4018/978-1-7998-5796-9.ch009

Publications in International Journals (from the thesis)

1. MKS Sarkar, AK Tilak and DN Basu (2014), A State-of-the-art Review of Recent Advances in Supercritical Natural Circulation Loops for Nuclear Applications, Annals of Nuclear Energy, Vol. 73, pp. 250-263, DOI: 10.1016/j.anucene.2014.06.035
2. MKS Sarkar and DN Basu (2015), Working Regime Identification for Natural Circulation Loops by Comparative Thermalhydraulic Analyses with Three Fluids under Identical Operating Conditions, Nuclear Engineering and Design, Vol. 293, pp. 187-195, DOI: 10.1016/j.nucengdes.2015.07.046
3. MKS Sarkar and DN Basu (2017), Numerical Appraisal on the Suitability of Supercritical Condition in Natural Circulation Loop with Isothermal Boundary Conditions, International Journal of Thermal Sciences, Vol. 111, pp. 30-40, DOI: 10.1016/j.ijthermalsci.2016.08.002
4. MKS Sarkar and DN Basu (2017), Numerical Comparison of Thermalhydraulic Aspects of Supercritical Carbon Dioxide and Subcritical Water-based Natural Circulation Loop, Nuclear Engineering and Technology, Vol. 49, No. 1, pp. 103-112, DOI: 10.1016/j.net.2016.09.007
5. MKS Sarkar and DN Basu (2017), Influence of Geometric Parameters on Thermalhydraulic Characteristics of Supercritical CO₂ in Natural Circulation Loop, Nuclear Engineering and Design, Vol. 324, pp. 402-415, DOI: 10.1016/j.nucengdes.2017.08.032

Publications in International Conference Proceedings (from the thesis)

1. MKS Sarkar and DN Basu (2013), CFD-based Performance Analysis for a Rectangular Natural Circulation Loop with End Heat Exchangers, Proc. 22^nd National and 11^th International ISHMT-ASME Heat and Mass Transfer Conference, Kharagpur, India, December 28-31, Paper ID HMTC1300090
2. MKS Sarkar and DN Basu (2015), Numerical Comparison of Flow Behavior and Heat Transfer Aspects of Supercritical CO2 and Subcritical Water based Natural Circulation Loop, Proc. 23^rd International Conference on Nuclear Engineering (ICONE23), Chiba, Japan, May 17-21, Paper No. ICONE23-1279
3. MKS Sarkar and DN Basu (2015), Effect of Inclination in Thermalhydraulics of Supercritical Natural Circulation Loop, Proc. Indian Chemical Engineering Congress (CHEMCON 2015), Guwahati, India, December 27-30, Paper ID FM-105
4. MKS Sarkar and DN Basu (2016), Experimental and Computational Analysis of Supercritical Natural Circulation Loop, Proc. 6^th International and 43^rd National Conference on Fluid Mechanics and Fluid Power (FMFP2016), Allahabad, India, December 15-17, Paper No. 440.
5. MKS Sarkar and DN Basu (2016), Effect of Geometrical Parameters on Thermalhydraulics of Supercritical Natural Circulation Loop, Proc. 6^th International and 43^rd National Conference on Fluid Mechanics and Fluid Power (FMFP2016), Allahabad, India, December 15-17, Paper No. 551
6. MKS Sarkar and DN Basu (2017), Design and Numerical Performance Evaluation of a Scaled-down Supercritical Natural Circulation Loop, Proc. 24^th National and 2^nd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2017), Hyderabad, India, December 27-30, Paper ID IHMTC2017-11-0617

Dr. Kiran Saikia

Publications in International Journals (from the thesis)

1. K Saikia, M Pandey and DN Basu (2019), Numerical Investigation of the Effect of Inlet Subcooling on Flow Instabilities in a Parallel Channel Natural Circulation Boiling System, Progress in Nuclear Energy, Vol. 114, pp. 13-21, DOI: 10.1016/j.pnucene.2019.01.028
2. K Saikia, DN Basu and M Pandey (2020), Parametric Studies on Startup Transients in Multiple Parallel Channels of a Natural Circulation Boiling System, Annals of Nuclear Energy, Vol. 138, pp. 107211, DOI: 10.1016/j.anucene.2019.107211
3. K Saikia, DN Basu and M Pandey (2022), Numerical Characterization of Thermalhydraulics of Subcooled Flow Boiling through the Annular Core of a Test Facility, Annals of Nuclear Energy, Vol. 167, pp. 108836, DOI: 10.1016/j.anucene.2021.108836

Publications in International Conference Proceedings (from the thesis)

1. K Saikia, RR Hansda, M Pandey and DN Basu (2017), Numerical Simulation of Parallel Channel Natural Circulation System using RELAP5 Code, Proc. 24^th National and 2^nd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2017), Hyderabad, India, December 27-30, Paper ID IHMTC2017
2. SV Kasar, K Saikia, KN Iyer, M Pandey and DN Basu (2017), Experimental Study of Cold Startup in Parallel Channel Natural Circulation System, Proc. 24^th National and 2^nd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2017), Hyderabad, India, December 27-30, Paper ID IHMTC2017-11-1117
3. K Saikia, DN Basu and M Pandey (2018), Effect of Subcooling on the Instabilities of a Two-Phase Natural Circulation System. Proc. 7^th International and 45^th National Conference on Fluid Mechanics and Fluid Power (FMFP2018), Mumbai, India, December 10-12, Paper No. 512
4. K Saikia, DN Basu and M Pandey (2019), CFD Simulation of Local Characteristics of Flow Boiling of Water in a Vertical Annulus, Proc. 25^th National and 3^rd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2019), Roorkee, India, December 28-31, Paper ID IHMTC2019-MPF-735

Abstract of Thesis

The two-phase natural circulation process is regarded as an efficient mode of energy transmission in boiling systems owing to the passive safety and absence of prime movers. However, flow instability is a vital issue in natural circulation boiling systems.This thesis explores a parallel channel natural circulation boiling system to identify relevant thermal-hydraulic characteristics. The focus of this study is on the Parallel channelNatural Circulation Test Facility(PCNCTF), which is a scaled-down version of the Advanced Heavy Water Reactor (AHWR). Unlike regular parallel channel systems that generally have an even number of channels (mostly two channels), PCNCTF is a three-channel systemthatadds complexities to its dynamics.The thermal-hydraulic instabilities associated with this system are evaluated experimentally, as well as numerically. During boiling operations, the oscillatory behavior of the mass flow transients is observed,which is characterized as density wave oscillations (DWO). The responseof flow rate transients subjected to different system pressure, power inputs,and inlet subcooling are thoroughly investigated. Typically, a Type-Idensity wave oscillation (DWO) is identified by large amplitude out-of-phase oscillations with multiple harmonic frequencies. Usually, the inception of instability can be delayed by first pressurizing the loop externally with N2before applying heat. At constant system pressure, the amplitude and frequency of flow instability can be controlled by regulating input power and inlet subcooling.
To support the experimental study, a 1-D model of the parallel channel test facility is developed to perform numerical simulations for different operating conditions. Simulations are also carried out for differentcore hydraulic diameter. The commercial code RELAP5/MOD3.2 is employed to solve the two-phase conservation equations. Numerical simulation is performed on mass flow oscillations that appear in the startup process of the parallel channel system. An extensive investigation is made to demonstrate the influence of associated geometric and operating parameters on such oscillations. All the parallel channels undergo a prolonged period of single-phase operation initially, characterized by low flow rates and consistent rise in bulk temperature. It is followed by large-amplitude geyseringfluctuations in flow rate and void fraction, on the initiation of the two-phase mode. Geysering may also lead to reverse flow in one of the three parallel channels by forming a local loop between two adjacentchannels. The role of initial pressure in subsiding the startup transients is considerably more significant than other parameters. An augmented initial pressure is capable of neutralizing oscillations and removing any reversed flow and geysering in all the channels.
Inlet subcooling is considered as one of the significant parameters in boiling flow systems. A numerical analysis of the influence of inlet subcooling on flow oscillations is done under different system pressures and input power. For a fixed set of inputs, the flow tends to become steady beyond a specificvalue of subcooling, below which instabilities appear. For high degrees of inlet subcooling, a particular type of superimposed DWO is identified. Flow oscillations of the three channels may be in-phase or out-of-phase depending upon imposed inlet subcooling. However, the scope of the 1-D code is limited since it is unable to calculate the local flow characteristics. A computational fluid dynamics code ANSYS Fluent 15.0 is used to simulate subcooled flow boiling through the annularcore section of PCNCTF. For that purpose, a 2-D axisymmetric model is employed using the RPI boiling model in the Euler-Euler framework. Three important transition locations can be located along the heated surface concerning subcooled boiling. While ONB corresponds to the locationof wall vapor volume fraction becoming positive, OSV exhibits an enhancement in the slope of vapor volume fraction at the wall and thickening of the superheated liquid layer. The third transition location characterizes the point of convective heat flux shrinking to zero, signifying the inception of saturated boiling near the heated surface, which is soon followed by fully-developed saturated boiling. An increase in heat flux and a fall in mass-flux moves the location of ONB upstream. However, system pressure seems to have a negligible effect on the wall vapor generation rate, when the heat flux and mass flux is kept constant.

Dr. Bhaskarjyoti Sarma

Publications in International Journals (from the thesis)

1. B Sarma, V Shahapure, A Dalal and DN Basu (2019), Experimental Characterization of the Growth Dynamics during Capillarity-driven Droplet Generation, Physical Review E, Vol. 100, pp. 013106, DOI: 10.1103/PhysRevE.100.013106
2. B Sarma, V Shahapure, A Dalal and DN Basu (2020), Magnetowetting Dynamics of Sessile Ferrofluid Drops on Soft Surface, Soft Matter, Vol. 16, pp. 970-982, DOI: 10.1039/C9SM01944H
3. B Sarma, S Kumar, A Dalal, DN Basu and D Bandyopadhyay (2021), Electric Discharge Mediated Jetting, Crowning, Bursting, and Atomization of a Droplet, Physical Review Applied, Vol. 15, pp. 014005, DOI: 10.1103/PhysRevApplied.15.014005
4. B Sarma, A Dalal and DN Basu (2022), Interfacial Dynamics of Viscous Droplets Impacting a Superhydrophobic Candle Soot Surface: Overview and Comparison, Physics of Fluids, Vol. 34, pp. 012121, DOI: 10.1063/5.0070828
5. B Sarma, A Dalal and DN Basu (2023), Jetting Dynamics of Viscous Droplets on Superhydrophobic Surfaces, Langmuir, Vol. 39, pp. 14040-14052, DOI: 10.1021/acs.langmuir.3c01820

Publications in International Conference Proceedings (from the thesis)

1. B Sarma, S Kumar, A Dalal, DN Basu, AK Dasmahapatra and D Bandyopadhyay (2016), Instability and Breaking of Aqueous Droplet on a Dielectric Coated Electrode, Proc. Complex Fluids (Comflu 2016), Hyderabad, India, December 12-14
2. B Sarma, S Pokhrel, S Kumar, A Dalal, D Bandyopadhyay and DN Basu (2018), Prediction of Sauter Mean Diameter of Spray during Electric Discharge Mediated Bursting of a Droplet, Proc. International Conference on Recent Innovations and Developments in Mechanical Engineering, Shillong, India, November 8-10, Paper No. 251
3. V Shahapure, B Sarma, A Dalal and DN Basu (2018), High Speed Imaging and Analysis of Drop Formation, Proc. 7^th International and 45^th National Conference on Fluid Mechanics and Fluid Power (FMFP2018), Mumbai, India, December 10-12, Paper No. 680
4. B Sarma, DN Basu and A Dalal (2018), Universal Scaling Laws in Drop-on-deman Generation from a Yarn, Proc. 7^th International and 45^th National Conference on Fluid Mechanics and Fluid Power (FMFP2018), Mumbai, India, December 10-12, Paper No. 467
5. B Sarma, DN Basu and A Dalal (2019), Droplets Impacting upon Superhydrophobic Surfaces, Fluids and Health 2019 Conference: Fluid Dynamics Disease Transmission, Cargese, France, July 23 - August 2 (Oral Presentation Only)
6. B Sarma, A Dalal and DN Basu (2019), Transient Interfacial Dynamics of Viscous Droplets Impacting on Superhydrophobic Surfaces, Proc. 25^th National and 3^rd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2019), Roorkee, India, December 28-31, Paper ID IHMTC2019-MNT-868

Publications in National Conference Proceedings (from the thesis)

1. B Sarma, S Kumar, A Dalal, DN Basu, AK Dasmahapatra and D Bandyopadhyay (2017), Directional Motion of Nanoparticle Laden Droplets on Micro-Fiber Highway, Proc. Nano India 2017, Delhi, India, March 15-16
2. B Sarma, DN Basu and A Dalal (2019), Dynamics of Droplet Generation in a Critically Low Weber Number Flow, Proc. Indian Conference on Applied Mechanics (INCAM-2019), Bengaluru, India, July 3-5, Paper No. 236

Abstract of Thesis

The manipulation of a discrete liquid droplet or a group of droplets with or withoutthe deformation of the liquid-vapour interface in the presence of an externally stim-ulating field is an integral part ofLab-On-Chipdevices, which in turn determinesthe performance of target applications. A detailed appraisal of the underlying rich physics associated with the deformation and/or disruption of the continuous two-phase interface and the behaviour of the contact line during the actuation of adroplet over an open surface or inside a closed channel, engendered in the presenceof an external force, apparently contribute towards enhancing the efficacy of numerous microfluidics applications. In this regard, a plethora of complex hydrodynamicfeatures during actuation, mixing, merging, or splitting of discrete droplets havebeen unfurled by the scientific community over the past years. However, owing tothe growing demand for microfluidics platforms in a host of cutting-edge engineeringand biomedical applications, it has become necessary to assess the existing or noveldroplet-based physical systems more comprehensively. Thanks to the advancementof high-speed visualization tools and computational techniques, the latter task hasbecome easier nowadays. The present thesis work draws enormous motivation from the aforementioned observations and makes an honest attempt to uncover the richphysics associated with the behaviour of single liquid droplets in the presence of ex-ternal potentials, such as electric field, magnetic field, imposed inertia, etc., in a fewinteresting and unexplored physical systems. The problems addressed within the scope of the present thesis include the growth dynamics of a droplet from a yarn,softness mediated magnetowetting of sessile ferrofluid droplets, electric-discharge-mediated atomization of a conducting sessile droplet, and impact dynamics of vis-cous droplets on a superhydrophobic surface. Overall, the focus has been laid on experimentally characterizing the temporal evolution of the shape and contact line(s)during the growth/deformation phase of a droplet and the subsequent atomizationdynamics of the primary droplet. Apart from the externally applied field, the effectof thermophysical properties of the liquid and properties of the substrate in contact have also been characterized during the systematic experimental investigation of theaforementioned systems. High-speed imaging/videography techniques are used pri-marily to analyze the intricate physical details of the systems under consideration.Also, the experimental results are strengthened by scaling analysis and numerical simulations. The comprehensive experimental analysis of each system unveils several interesting hydrodynamic features, such as liquid jet formation, crown formation,bursting ejecta sheet, lamella ejection, capillary pinch-off, high-speed hair-like jetsemanating from a parent droplet exposed to different external stimulations. The aforementioned flow morphologies contribute enormously towards the effective at-omization of the parent droplet, desirable for many microfluidics applications. Thecontributions from this thesis work are expected to pave the way for several newresearch avenues in microfluidics.

Dr. Aritra Mukherjee

Publications in International Journals (from the thesis)

1. A Mukherjee, DN Basu and PK Mondal (2021), Algorithmic Augmentation in the Pseudopotential-based Lattice Boltzmann Method for Simulating the Pool Boiling Phenomenon with High-density Ratio, Physical Review E, Vol. 103, pp. 053302, DOI: 10.1103/PhysRevE.103.053302
2. A Mukherjee, DN Basu and PK Mondal (2022), Mesoscopic Characterization of Bubble Dynamics in Flow Boiling following A Pseudopotential-based Approach, International Journal of Multiphase Flow, Vol. 148, pp. 103923, DOI: 10.1016/j.ijmultiphaseflow.2021.103923
3. A Mukherjee, DN Basu, PK Mondal and L Chen (2022), Characterization of Condensation on Nanostructured Surfaces and Associated Thermal Hydraulics using Thermal Lattice Boltzmann Method, Physical Review E, Vol. 105, pp. 045308, DOI: 10.1103/PhysRevE.105.045308

Publication in International Conference Proceedings (from the thesis)

1. A Mukherjee, DN Basu and PK Mondal (2019), Lattice Boltzmann Simulation of Periodic Bubble Nucleation, Growth and Departure in Nucleate Pool Boiling, Proc. 25^th National and 3^rd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2019), Roorkee, India, December 28-31, Paper ID IHMTC2019-MPF-527
2. A Mukherjee, DN Basu and PK Mondal (2020), Numerical Investigation of the Effect of Surface Topology on Droplet Condensation following Lattice Boltzmann Methods, Proc. 8^th International and 47^rd National Conference on Fluid Mechanics and Fluid Power (FMFP2020), Guwahati, India, December 9-11, Paper ID FMFP2020-244
3. A Mukherjee, L Chen and and DN Basu (2022), Numerical Investigation of Pool Boiling Heat Transfer Enhancement through Surface Modifications using the Lattice Boltzmann Method, Proc. 1^st World Conference on Multiphase Transportation, Conversion & Utilization of Energy (MTCUE 2022), Xi'an, China, July 27-31, Paper ID MTCUE2022-220106

Abstract of Thesis

The pseudopotential-based LB multiphase model has enormous potential in the simulation of phase-change heat transfer problems. It facilitates the natural development and migration of interfaces during the multiphase simulation as well as saves a lot of computational time. Along with these, this model enjoys several advantages like simple implementation procedure, excellent parallelizability, and easy applicability in complex domains. Due to these superiorities, it is becoming increasingly popular among researchers working on numerical simulation of multiphase flow. A pseudopotential model based thermal multiphase flow solver is developed as this thesis work, which is employed in several phase change heat transfer problems related to boiling and condensation.
The first problem successfully explores the capability of the pseudopotential-based thermal lattice Boltzmann model in emulating the underlying thermohydrodynamics of subcooled flow boiling in a narrow fluidic horizontal channel in detail. A two-dimensional rectangular channel with specified inlet temperature and flow rate, and exit pressure, housing a microheater at the bottom wall, is considered as the computational domain of interest. Adopted boundary conditions ensure subcooled flow boiling through the channel. The complete dynamics of bubble ebullition at the nucleation site, and subsequent flow regimes are adequately reproduced. Both bubbly and slug flow patterns are illustrated through the temporal evolution of the interface, and associated pressure drop and heat transport characteristics. Dependence of the departure characteristics on the flow rate, wall superheat and surface wettability is found to be consistent with available literature, which substantiates the competence of the present algorithm.
The next study uses the multiple-relaxation time based LB model to explore the role of surface morphology and cold spot temperature in determining the visual state of the condensate droplet, mode of nucleation and associated rates of energy and mass interactions in temperature controlled condensation process. Such a study is scarcely found in the available literature. A rectangular domain filled with saturated vapor, housing a cold spot on the bottom rough surface is considered, where the bottom surface has rectangular nanopillars to mimic a rough surface. Gradual increase in the spacing modifies the nucleation mode from top through side to bottom, while the droplet changes from Cassie to Wenzel state. A couple of phase diagrams have been developed to study the combined effect of pillar dimensions on Cassie and Wenzel drop formation. One important novelty of the present study is the consideration is non-isothermal condition within LB structure. Enhancement in the degree of subcooling at the cold spot encourages greater condensation and Cassie-to-Wenzel transition.
The same numerical framework is employed to study condensate droplet formation and movement on a microstructured surface, which has not yet been studied using LBM. Two vertical surfaces protruded with rectangular micropillars with disparate dimensions are considered for this purpose. The rectangular domain is assumed to be filled with saturated vapor initially and three separate cold spots are assumed on the cold bottom wall as nucleation sites. Condensate droplet, growth, coalescence, and movement is studied in detail through sequential temporal snapshots. It is observed that closely packed taller columns promote dropwise condensation having high heat transfer rate. Six different surface inclinations are considered to study the effect of gravitational force on condensation, which shows that a vertical surface has highest mass condensation rate and heat transfer rate due to maximum downward gravitational force.
Being motivated by the prime weakness of the pseudopotential based thermal LB model about its incapability of simulating boiling problems with a large density ratio, the last work of this thesis focuses on augmentation of the basic pseudopotential based thermal multiphase algorithm by enhancing the isotropy of the discrete equation and thermodynamic consistency of the overall formulation, to expedite simulation of pool boiling at higher-density ratios. Accordingly, modification is suggested in the discrete form of the updated interparticle interaction term, by expanding the discretization to the eighth order. The proposed amendment is successful in substantially reducing the spurious velocity in the vicinity of a static droplet, while allowing stable simulation at a much higher-density ratio under identical conditions, which is a noteworthy improvement over existing Single Relaxation Time (SRT)-LBM algorithms. Various pool boiling scenarios have been explored for a reduced temperature of 0.75, which itself is significantly lower than reported in comparable literature, in both rectangular and cylindrical domains, and also with micro- and distributed heaters. All three regimes of pool boiling have aptly been captured with both plain and structured heaters, allowing the development of the boiling curve. The predicted value of critical heat flux for the plain heater agrees with Zuber correlation within 10%, illustrating both quantitative and qualitative capability of the proposed algorithm.

Dr. Nitesh Kumar

Book Chapter (from the thesis)

1. N Kumar, DN Basu and L Chen, Effect of Flow Acceleration and Buoyancy on Thermalhydraulics of sCO₂ in Mini/Micro-Channel, in: L Chen (eds.) Handbook of Research on Advancements in Supercritical Fluids Applications for Sustainable Energy Systems, IGI Global, Hershey PA, USA, Ch. 5, pp. 161-182, 2021, DOI: 10.4018/978-1-7998-5796-9.ch005

Publications in International Journals (from the thesis)

1. N Kumar and DN Basu (2021), Role of Buoyancy on the Thermalhydraulic Behavior of Supercritical Carbon dioxide Flow through Horizontal Heated Minichannel, International Journal of Thermal Sciences, Vol. 168, pp. 107051, DOI: 10.1016/j.ijthermalsci.2021.107051
2. N Kumar and DN Basu (2022), Thermalhydraulic Comparison of Supercritical Fluids in Minichannel Heat Sink to Assess the Suitability of Macroscopic Scaling Rules, Nuclear Engineering and Design, Vol. 392, pp. 111750, DOI: 10.1016/j.nucengdes.2022.111750
3. N Kumar, S Ghosh and DN Basu (2023), Thermalhydraulic Assessment and Performance Prediction of Supercritical Minichannel Heat Sink with Airfoil-shaped Obstructions using GA-tuned Neural Network, Applied Thermal Engineering, Vol. 227, pp. 120352, DOI: 10.1016/j.applthermaleng.2023.120352
4. N Kumar and DN Basu (2023), Thermalhydraulic Assessment and Design Optimization of Incorporating Flow Obstructors in a Supercritical Minichannel Heat Sink, Applied Energy, Vol. 349, pp. 121666, DOI: 10.1016/j.apenergy.2023.121666

Publication in International Conference Proceedings (from the thesis)

1. N Kumar and DN Basu (2019), Computational Appraisal of the Thermalhydraulic Characteristics of Supercritical Carbon dioxide in Heated Minichannel for HVAC Applications, Proc. International Conference on Sustainable Energy and Green Technology (SEGT2019), Bangkok, Thailand, December 11-14, Paper ID 276, IOP Conference Series: Earth and Environmental Science, Vol. 463, DOI: 10.1088/1755-1315/463/1/012048
2. N Kumar and DN Basu (2020), Computational Analysis of Thermalhydraulics of Supercritical CO₂ in Horizontal Finned Square Microchannel Heat-sink, Proc. 8^th International and 47^th National Conference on Fluid Mechanics and Fluid Power (FMFP2020), Guwahati, India, December 9-11, Paper ID FMFP2020-255
3. N Kumar and DN Basu (2021), Numerical Investigation on Heat Transfer Coefficient of Supercritical CO₂ in A Extended Surface Micro Heat-sink, Proc. 26^th National and 4^th International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC 2021), Chennai, India, December 17-20, Paper ID: IHMTC2021-201
4. N Kumar and DN Basu (2022), Analysis of Thermal Performance for Supercritical Fluid Flowing in a Microchannel Heat Sink Utilizing Internal Fins, Proc. 7^th Thermal and Fluids Engineering Conference (TFEC), Las Vegas, USA, May 15-18, Paper ID: TFEC-2022-40865
5. N Kumar and DN Basu (2022), Flow Dynamics in Transient Heat Transfer of Carbon dioxide at Supercritical Pressure in Microchannel, Proc. 1^st International Conference in Fluid Thermal and Energy Systems, Calicut, India, June 9-11, Paper ID: ICFTES2022–TS–163
6. N Kumar and DN Basu (2022), Thermalhydraulic Optimization of Microchannel Heat-sink with Carbon-dioxide at Supercritical Pressure, Proc. 1^st World Conference on Multiphase Transportation, Conversion & Utilization of Energy (MTCUE 2022), Xi'an, China, July 27-31, Paper ID MTCUE2022-220139

Abstract of Thesis

The rapid advancement of high performance tiny electronic devices has been sparked by the growing dependence of modern human life on digitization and artificial intelligence. To ensure dependable performance during the full designated operating regime as well as a satisfactory life term, designers now face the additional problem of thermal management due to the sharp increase in the power density requirements for such equipment. Heat generation is an irreversible process, and it must be removed for components to function continuously. Since the temperature rise in the circuits is the primary cause of component failures, the thermal energy generated during operation needs to be effectively reduced for the components to operate continuously. As a result, a significant amount of study has been focused on the evaluation of alternative working fluids as well as the creation and augmentation of effective cooling strategies over the past ten years. The high area-to-volume ratio of a miniaturised or mini-channel heat sink (MCHS) and the favourable thermophysical properties of the medium have been identified as two factors that make this option particularly enticing.
Both numerical and experimental appraisal of sCO₂ is presented in the present thesis. Thorough numerical investigation has been performed to explore the steady-state, as well as transient characteristics of sCO₂. The applicability of macrochannel scaling laws explored to study the thermalhydraulic characteristics of five different supercritical fluids flowing through minichannel. Comparing supercritical fluids to single-phase and even boiling channels, supercritical fluids consistently have a higher heat transfer coefficient. As a result of the forced scaling, a significant degree of similarity has been seen in the visual character of the dimensionless momentum and heat fields as well as local recirculation patterns across the fluids. The scaling model, however, falls short when it comes to defining dimensionless groups since there are noticeable differences between local Reynolds number and local and area-averaged Nusselt number. For enhancing the used scaling methods, it is advised to take into account the Prandtl number profiles and dimensionless thermal conductivity with dimensionless enthalpy.
With a focus on the impact of local buoyancy, the numerical characterisation of thermal hydraulics of supercritical carbon dioxide flowing through a horizontal minichannel is investigated. It is discovered that buoyancy-induced local recirculation, which results from density stratification, has a significant impact on both azimuthal and axial profiles. Due to thermal asymmetry, the average heat transfer coefficient over the bottom half of the surface is substantially higher than the same over the top half, allowing for delayed heat transfer degradation there. This discrepancy increases at larger heat fluxes but decreases with pressure. The maxima in average heat transfer coefficient corresponds to the pseudocritical temperature. Increased heat transport is aided by larger mass flux, with the peak occurring downstream. Finally, a buoyancy parameter that accurately describes the loop performance is established in accordance with the macrochannel literature.
Flow of sCO₂ is prone to heat transfer deterioration, therefore, modulation of the thermalhydraulic characteristics of the miniaturized heat sink by geometric alteration is mandatory. In order to determine an ideal orientation and design, the current thesis evaluates the response of a square minichannel by including rectangular obstructions. The primary variable is a performance assessment criterion, which is defined as a combined change in both heat transfer coefficient and pressure drop as a result of geometric adjustment. The installation of the obstructions significantly increases the turbulent mixing between the fluid layers, resulting in a smaller temperature difference between the wall and the fluid and an improved heat transfer coefficient. A relatively lower level of temperature is maintained within the baffled section, thereby delaying the appearance of heat transfer deterioration. However, obstructions significantly increase pressure losses, making careful selection of the dimensions necessary. The most practical choice has been determined to be the employment of three pairs of baffles. Along with a thorough thermalhydraulic analysis of the role of the operating variables with the ideal design, desirable values of the height, thickness, and inclination angle for individual plates in this orientation have also been determined.
It is apparent that flow obstructions improve heat transfer performance of minichannel heat sinks but at the cost of higher pressure drop. Therefore, it is necessary to compare the thermalhydraulic performance of various flow obstacle shapes. The installation of airfoil shaped flow obstacles in a CO₂-driven heated minichannel with a square cross-section is being investigated computationally. The use of obstacles is found to be efficient over the whole range of supply flow rate with three or more pairs, but advantageous only over a small range of Reynolds number for single and two pairs of airfoils. Performance is enhanced overall by increasing the separation between adjacent airfoils and the breadth of each obstacle, as well as by vertical orientation. The performance of an airfoil-shaped flow obstruction is superior to a rectangular one for a variety of geometric configurations, according to a study of their thermalhydraulic performance. A multi layer feed forward NN (MLFF-NN) is trained by the back propagation (BP) technique for the successful prediction of the supercritical mini channel heat sink (MCHS) performance corresponding to various geometric configurations of the heat sink and the model is able to predict the performance for several test cases with satisfactory level of accuracy.
To enlarge the corresponding experimental database for sCO₂ flow through minichannels experiments have been performed under heating conditions. The governing parameters are mainly the heat flux, mass flux, operating pressure, and inlet temperature of the supercritical carbon dioxide. The wall temperature measurement of the test section was performed using an infrared thermal imaging camera to capture continuous wall temperature variation in the axial direction. The comparison of experimental data with simulated results showed similar qualitative trend with largest deviation of 7.69% which is very near the uncertainty value of ±7%. In order to reach pseudocritical point with the same inlet temperature, the system needs to be heated for a longer period of time, which causes a delay in peak HTC, albeit with substantially increased magnitude. Because pseudocritical temperature is reached earlier and there is less asymmetry in the flow domain as a result, the impact of a change in system pressure is significantly less noticeable at larger heat fluxes. It is also reasonable to infer that pressure has less of an effect on HTC than does heat flux.
The stability behaviour and flow acceleration caused by variations in the non-linear thermophysical parameters have a significant impact on the supercritical fluids’ capability to transfer heat. With an emphasis on the impact of flow oscillation, numerical analysis has been done to examine the transient properties of sCO₂ at supercritical pressures. A wide range of system parameters, including time period of oscillations, operating pressure, amplitude of the wall heat flux, and mass flow, have been used in the transient simulations. It is discovered that axial profiles are significantly affected by flow acceleration-induced local oscillation, which results from the fluctuation in thermophysical characteristics. Lower response times and longer transient behaviour are caused by higher mass flux. Higher operating pressure subsided fluctuation in both mass flow rate and wall shear stress, indicating that higher operating pressure can aid to reduce system instability, which is caused by the combined effect of reduced viscosity and velocity variation at higher pressure.

Dr. Sambit Majumder

Publications in International Journals (from the thesis)

1. S Majumder, A Ghosh, DN Basu and G Natarajan (2022), Revisiting the Partially-Saturated-Cells Method for Incompressible Flows with Stationary and Moving Bodies, Computers and Mathematics with Applications, Vol. 110, pp. 19-39, DOI: 10.1016/j.camwa.2022.01.034
2. S Majumder, A Ghosh, DN Basu and G Natarajan (2023), Computational Assessment of Immersed Boundary-Lattice Boltzmann Method for Complex Moving Boundary Problems, Computational Particle Mechanics, Vol. 10, No. 1, pp. 155-172, DOI: 10.1007/s40571-022-00487-5
3. S Majumder, DN Basu and G Natarajan (2023), Comprehensive Assessment of the Partially-Saturated-Cells Framework for Convective Problems, International Journal of Heat and Mass Transfer, Vol. 217, pp. 124613, DOI: 10.1016/j.ijheatmasstransfer.2023.124613
4. S Majumder, DN Basu and G Natarajan (2024), Partially-saturated-cells Approach for Conjugate Heat Transfer Problems, Computers and Fluids, Vol. 274, pp. 106232, DOI: 10.1016/j.compfluid.2024.106232
5. S Majumder, DN Basu and G Natarajan (2024), A Novel and Simple Approach to Implement Adiabatic Boundary Conditions in Partially-saturated-Cells Method, International Communications in Heat and Mass Transfer, Vol. 156, pp. 107621, DOI: 10.1016/j.icheatmasstransfer.2024.107621

Publication in International Conference Proceedings (from the thesis)

1. A Ghosh, S Majumder, G Natarajan and DN Basu (2018), Comparative Study of Two Immersed Boundary Approaches in the Lattice Boltzmann Framework, Proc. 7^th International and 45^th National Conference on Fluid Mechanics and Fluid Power (FMFP2018), Mumbai, India, December 10-12, Paper ID 800
2. S Majumder, A Ghosh, DN Basu and G Natarajan (2019), Development of An Immersed Boundary-Thermal Lattice Boltzmann Solver for Fluid-particle Interaction in Energy Management Systems, Proc. International Conference on Sustainable Energy and Green Technology (SEGT2019), Bangkok, Thailand, December 11-14, Paper ID 236, IOP Conference Series: Earth and Environmental Science, Vol. 463, DOI: 10.1088/1755-1315/463/1/012044
3. S Majumder, A Ghosh, DN Basu and G Natarajan (2020), Computational Assessment of Immersed Boundary-Lattice Boltzmann Method for Complex Moving Boundary Problems, Proc. 8^th International and 47^th National Conference on Fluid Mechanics and Fluid Power (FMFP2020), Guwahati, India, December 9-11, Paper ID FMFP2020-249
4. S Majumder, DN Basu and G Natarajan (2023), Development and Validation of a Novel Solid Collision Operator in IB-LB Framework for Simulation of Thermal Flows, Proc. 17^th International Heat Transfer Conference (IHTC-17), Cape Town, South Africa, August 14-18, Paper ID IHTC17-404
5. S Majumder, DN Basu and G Natarajan (2023), Comparative Appraisal of Direct-forcing Immersed-Boundary Lattice Boltzmann Method and Partially Saturated Cells Method for Thermofluidic Applications, Proc. 27^th National and 5^th International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC 2023), Patna, India, December 14-17, Paper ID IHMTC2023-225

Abstract of Thesis

This thesis is devoted to the development of a robust and accurate partially saturated cells (PSC) based lattice-Boltzmann (LB) solver for incompressible flows and its application to conjugate heat transfer process. The lattice-Boltzmann (LB) method has emerged as a promising alternative to the conventional Navier-Stokes solvers in the last two decades. Despite certain promising advantages, the conventional treatment of boundary conditions on the curved surfaces using LB approaches suffer staircase representation of the surface. This disparity gets exacerbated in moving boundary problems with continuous interchange of fluid and solid lattice nodes necessitating refilling algorithms at each time, and leads to an increased computational expense. Hence, the need for a fast and robust computational framework for moving body problems has led to the emergence of non-body conformal methods, like the coupled immersed boundary-lattice Boltzmann (IB-LB) method, over the last two decades. Recently, one such variant of the IB-LB method, namely the partially saturated computational cells (PSC) method, has evolved as a promising numerical framework for several moving boundary applications. The key advantage of the technique is that, it employs a unified evolution equation for all media (solid and fluid) present in the computational domain comprising a weighting function based on solid volume fraction and an additional solid collision operator. The latter two elements of the PSC technique are responsible for affecting the boundary conditions to be imposed on the solid body, which may be stationary or moving.
The present thesis demonstrates a comprehensive appraisal of the PSC algorithm subjected to moving boundary scenarios that have hitherto not been explored in open literature but are important for the practical viability of the approach. Key aspects pertaining to the performance assessment of the approach comprise accuracy studies, discrete conservation of properties, dependence of spurious fluctuations on grid resolution for moving boundary problems and Galilean invariance. In addition, the solver’s robustness is exhibited for a wide range of non-trivial benchmark problems encompassing stationary and moving boundary problems for hydrodynamic and thermal flows. Furthermore, a novel algorithm for simulating conjugate heat transfer problems using PSC is expounded. A novel strategy for implementation of adiabatic boundary conditions is also elaborated in the present work. Both of these strategies are validated with standard free, forced and mixed convection problems.

Dr. Shikha Bhuyan

Publication in International Conference Proceedings (from the thesis)

1. S Bhuyan and DN Basu (2017), Numerical Analysis of Effect of Prandtl Number on Natural Convection using Lattice Boltzmann Method, Proc. 24^th National and 2^nd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2017), Hyderabad, India, December 27-30, Paper ID IHMTC2017-09-0368
2. S Bhuyan and DN Basu (2019), Numerical Analysis of Mixed Convection Flow using Non-Boussinesq Approximation Lattice Boltzmann Method, Proc. 25^th National and 3^rd International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2019), Roorkee, India, December 28-31, Paper ID IHMTC2019-NHT-641
3. S Bhuyan, DN Basu and S Majumder (2023), Investigation of Natural Convection in Square Cavity Implementing non-Boussinesq Approximation, Proc. 10^th International and 50^th National Conference on Fluid Mechanics and Fluid Power (FMFP2023), Jodhpur, India, December 20-22, Paper ID FMFP2023-526

Publication in National Conference Proceedings (from the thesis)

1. S Bhuyan and DN Basu (2017), Study of Flow Behavior of Natural Convection for Different Prandtl Number using Lattice Boltzmann Method, Proc. 1^st National Conference in Sustainable Mechanical Engineering: Today and Beyond (SMETB), Tezpur, India, March 24-25

Abstract of Thesis

This thesis presents a practical and significant advancement in the Lattice Boltzmann Method (LBM) for buoyancy-driven flow in a single fluid phase. Utilizing the D2Q9 lattice and the LBGK method in two dimensions, the developed LBM codes demonstrate excellent performance across a wide range of problems. Special attention is given to ensuring accurate and realistic parameterizations, thoroughly validated both qualitatively and quantitatively through rigorous exercises. The thesis begins by validating the newly developed LBM code through simulations of various benchmark isothermal and thermal flow problems. Next, the thermal lattice Boltzmann method (TLBM) is applied to study natural convection problems. The study introduces non-Boussinesq simulations, considering temperature-dependent fluid properties, and compares them to the traditional Boussinesq approach. The results reveal that non-Boussinesq simulations exhibit higher values of entropy generation and Nusselt numbers, reflecting a more accurate representation of fluid behavior. Furthermore, the role of fluid friction in entropy generation is examined, and it is found that as Ra increases, the contribution of entropy generation due to fluid friction becomes more prominent, exceeding that of heat transfer at a critical Ra value of 106 . This highlights the increasing significance of fluid friction in overall entropy production, particularly beyond the critical Ra.
The prime objective of the thesis work is to understand the buoyancy-driven flow insight behavior. Furthermore, the research explores mixed convection problems on three different configurations, investigating influential parameters and optimizing their effects on heat transfer and entropy generation, providing new insights into this field. The three distinct cases are: (i) Top lid moving in forward direction and bottom lid is kept stationary (Case 1); (ii) Both top and bottom lids moving in forward direction (Case 2); (iii) Both top and bottom lids moving in opposite direction (Case 3). Comparing the three cavity configurations, it is observed that heat transfer rate and irreversibility are minimum for Case 1, followed by Case 2 and Case 3, for all varying parameters. The inclination angle has a notable impact on both Nusselt number and entropy generation values, reaching their maximum limit at φ = 400 for Case 1 and 2, and φ = 500 for Case 3. However, the friction coefficient remains relatively constant for all three cases, regardless of the inclination angle. The maximum heat transfer rate and entropy generation are achieved at φ = 900 for all cases. In addition to this, the study of aspect and velocity ratio suggests that increasing the aspect ratio to AR=4 and decreasing the velocity ratio leads to decreased irreversibility, which may improve the overall performance of the system.
This study extends the applicability of the developed models by exploring a unified approach to investigate the influence of nanofluids on the thermalhydraulic behavior of natural circulation loops (NCLs). The goal is to optimize these systems by reducing entropy generation and improving performance using isothermal boundary conditions at the heater and cooler sections of the NCL. The investigation involves a transient study of NCLs, observing their time-dependent response under various thermal boundary conditions. These considered conditions include isothermal (CT), constant heat flux (CHT), linearly increasing (LI), linearly decreasing (LD), and sinusoidal heat flux conditions. The impact of different heat flux boundary conditions on heat transfer and entropy generation is thoroughly explored. The sinusoidal heat flux condition demonstrates higher heat transfer rates due to induced temperature and velocity fluctuations, resulting in enhanced convective heat transfer through fluid mixing. On the other hand, the linearly decreasing flux condition exhibits the highest fluctuation in entropy generation among the different heat flux boundary conditions.

Dr. Tanuj Srivastava

Book Chapter (from the thesis)

1. T Srivastava, P Sutradhar, DN Basu and L Chen, An Overview of the Dynamics of Supercritical Natural Circulation Loops, in: A Mukhopadhyay, S Sen, DN Basu and S Mondal (eds.) Dynamics and Control of Energy Systems, Springer Nature, Gateway East, Singapore, Ch. 5, pp. 85-110, 2019, DOI: 10.1007/978-981-15-0536-2_5
2. T Srivastava, P Sutradhar, MKS Sarkar and DN Basu, Supercritical Natural Circulation Loop: A Technology for Future Reactor, in: L Chen (eds.) Handbook of Research on Advancements in Supercritical Fluids Applications for Sustainable Energy Systems, IGI Global, Hershey PA, USA, Ch. 9, pp. 338-369, 2021, DOI: 10.4018/978-1-7998-5796-9.ch009

Publications in International Journals (from the thesis)

1. T Srivastava and DN Basu (2022), Numerical Characterization of Heat Transfer Deterioration in Supercritical Natural Circulation Loop and Role of Loop Inclination, Nuclear Engineering and Design, Vol. 390, pp. 111704, DOI: 10.1016/j.nucengdes.2022.111704
2. T Srivastava and DN Basu (2022), Numerical Evaluation of Static and Dynamic Stability Characteristics of A Supercritical CO₂-driven Natural Circulation Loop, The Journal of Supercritical Fluids, Vol. 191, pp. 105782, DOI: 10.1016/j.supflu.2022.105782
3. T Srivastava and DN Basu (2024), Dynamic Characterization of Supercritical Natural Circulation Loop under Periodic Excitation, International Journal of Thermal Sciences, Vol. 197, pp. 108835, DOI: 10.1016/j.ijthermalsci.2023.108835
4. T Srivastava and DN Basu (2024), Numerical Investigation of the Microdynamics of the Initiation of Motion and Startup Transients in a Supercritical Natural Circulation Loop, International Journal of Heat and Mass Transfer, Vol. 224, pp. 125289, DOI: 10.1016/j.ijheatmasstransfer.2024.125289
5. T Srivastava, AK Gond and DN Basu (2024), Numerical Appraisal of the Role of Heat Transfer Regimes on Transient Response of Carbon dioxide based Supercritical Natural Circulation Loop during Power Upsurge, Nuclear Engineering and Design, Vol. 429, pp. 113601, DOI: 10.1016/j.nucengdes.2024.113601

Publication in International Conference Proceedings (from the thesis)

1. T Srivastava and DN Basu (2020), Fluid-to-fluid Scaling of Supercritical Natural Circulation Loop under Steady-state Condition, Proc. 8^th International and 47^th National Conference on Fluid Mechanics and Fluid Power (FMFP2020), Guwahati, India, December 9-11, Paper ID FMFP2020-256
2. P Sutradhar, T Srivastava and DN Basu (2021), Numerical Study of Supercritical Natural Circulation Loop under Condition of Different Inclination and Diameter, Proc. 26^th National and 4^th International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC 2021), Chennai, India, December 17-20, Paper ID IHMTC2021-197
3. T Srivastava and DN Basu (2022), Steady-state Thermal-hydraulic Response of Supercritical Natural Circulation Loop under Different Loop Orientations, Proc. 1^st World Conference on Multiphase Transportation, Conversion & Utilization of Energy (MTCUE 2022), Xi'an, China, July 27-31, Paper ID MTCUE2022-220118

Abstract of Thesis

The natural circulation loop (NCL), despite its complex mathematical complexity, points to an efficient way for energy transfer from a high-temperature source to a low-temperature sink without coming into contact. The primary force behind any natural circulation system is the buoyancy force caused by the density gradient. The operating range of single-phase NCLs is constrained by saturation temperature and low flow rate, whereas two-phase loops are highly concerned about the possibility of dry-out and the emergence of different flow regimes with divergent heat transfer behaviour. Due to its strong capacity for heat transfer and significant volumetric expansion, supercritical fluid unveils a strong alternative by combining the benefits of single- and two-phase versions. In conjunction with this, the idea of a supercritical natural circulation loop (sNCL) has emerged as one of the most important endeavours for generation-IV nuclear reactors in the twenty-first century.
The current thesis presents both numerical and experimental evaluation of sNCL with CO₂ as a working fluid. The steady-state and transient behaviour of sNCL have been thoroughly investigated numerically with. Steady state analysis involved 3D numerical simulation while transient simulations were performed in 2D and 1D numerical framework. The cooler side condition is always set to constant temperature while except a few cases of dynamical response under time varying heating condition, the rest of the cases incorporates the constant heat flux input. Nature of the sNCL is governed by interplay between buoyancy force and friction force.
With the increase in the heating power, the dominance of the buoyancy causes the increment of the mass flow rate and heat transfer coefficient. Reaching the optimum condition of the buoyancy dominance at its peak, the flow rate becomes maximum leading to advent of friction dominance slowly, slow drop in the flow rate was witnessed in the mass flow rate after that. The average loop temperature is this case is slightly higher than T_pc. This is followed by sharp drop in the mass flow rate followed by huge bulk temperature and poor thermalhydraulics of the system, signifying the dominance of the friction force and lead. The condition termed as Flow induced heat transfer deterioration (FiHTD). The focus of the entire subject matter will be around this phenomenon with its relation to safer zone of operation and its correlation with the stability of the loop which is still untouched in the literature under the different sets of boundary conditions.

Mr. Ashok K Gond

Publications in International Journals (from the thesis)

1. AK Gond, A Dalal and DN Basu (2023), Thermalhydraulic Characterization and Feasibility Assessment of Double-cooled Annular Channel under Supercritical Heat Transfer, International Journal of Thermal Sciences, Vol. 193, pp. 108508, DOI: 10.1016/j.ijthermalsci.2023.108508
2. AK Gond, T Srivastava, A Dalal and DN Basu (2024), Characterization and Comparative Appraisal of Two Novel Annular Channel Designs with Variable Flow Areas for Supercritical Heat Transfer, Nuclear Engineering and Design, Vol. 430, pp. 113679, DOI: 10.1016/j.nucengdes.2024.113679

Publication in International Conference Proceedings (from the thesis)

1. AK Gond, DN Basu and A Dalal (2021), Thermalhydraulic Assessment of Supercritical CO₂ filled Double-cooled Annular Channel, Proc. 26^th National and 4^th International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC 2021), Chennai, India, December 17-20, Paper ID IHMTC2021-563
2. AK Gond, DN Basu and A Dalal (2022), Heat Tranfser Characteristics of Supercritical CO₂ in A Tapered Cylindrical Annular Channel, Proc. 1^st World Conference on Multiphase Transportation, Conversion & Utilization of Energy (MTCUE 2022), Xi'an, China, July 27-31, Paper ID MTCUE2022-220113
3. AK Gond, DN Basu and A Dalal (2022), Numerical Investigation of Heat Transfer Characteristics of sCO₂ in A Divergent Tapered Annular Channel, Proc. 9^th International and 49^th National Conference on Fluid Mechanics and Fluid Power (FMFP2022), Roorkee, India, December 14-16, Paper ID FMFP2022-6463

Mr. Biswajyoti Baishya

Publications in International Conference Proceedings (from the thesis)

1. B Baishya, A Mukherjee, Sambit Majumder and DN Basu (2023), On the Impact of Adjustable Surface Tension on Pool Boiling Phenomena via a Pseudopotential-based Solver, Proc. 10^th International and 50^th National Conference on Fluid Mechanics and Fluid Power (FMFP2023), Jodhpur, India, December 20-22, Paper ID FMFP2023-519

Ms. Urmi S Tejaswini

Publication in International Journals (from the thesis)

1. US Tejaswini, DN Basu and M Pandey (2017), Improved Scaling Analysis for Heat Transfer in a Circular Tube with Various Supercritical Fluids using Computational Fluid Dynamics Simulations, Heat Transfer Engineering, Vol. 38, No. 2, pp. 149-161, DOI: 10.1080/01457632.2016.1156432

Publications in International Conference Proceedings (from the thesis)

1. US Tejaswini, DN Basu and M Pandey (2013), CFD Investigation of Heat Transfer Deterioration in Supercritical Water Flowing through Vertical Annular Channels, Proc. 21^st International Conference on Nuclear Engineering (ICONE21), Chengdu, China, July 29 – August 02, Paper No. ICONE21-16720
2. US Tejaswini, DN Basu and M Pandey (2013), Scaling Analysis of Heat Transfer for Supercritical Fluids through CFD Simulations, Proc. 22^nd National and 11^th International ISHMT-ASME Heat and Mass Transfer Conference, Kharagpur, India, December 28-31, Paper ID HMTC1300096

Mr. Laxmikant S Korade

Dr. Abhilash Tilak

Publications in International Journals (from the thesis)

1. MKS Sarkar, AK Tilak and DN Basu (2014), A State-of-the-art Review of Recent Advances in Supercritical Natural Circulation Loops for Nuclear Applications, Annals of Nuclear Energy, Vol. 73, pp. 250-263, DOI: 10.1016/j.anucene.2014.06.035
2. AK Tilak and DN Basu (2015), Computational Investigation of the Dynamic Response of a Supercritical Natural Circulation Loop to Aperiodic and Periodic Excitations, Nuclear Engineering and Design, Vol. 284, pp. 251-263, DOI: 10.1016/j.nucengdes.2014.12.028

Publication in International Conference Proceedings (from the thesis)

1. AK Tilak and DN Basu (2015), Effect of Geometric and Operating Parameters on the Steady-state Characteristics of an SCNCL, Proc. 23^rd National and 1^st International ISHMT-ASTFE Heat and Mass Transfer Conference (HMTC2015), Trivandrum, India, December 17-20, Paper ID IHMTC2015-6

Mr. Yogesh K Ratre

Mr. Mayur Krishnani

Publications in International Journals (from the thesis)

1. M Krishnani and DN Basu (2016), On the Validity of Boussinesq Approximation in Transient Simulation of Single-phase Natural Circulation Loops, International Journal of Thermal Sciences, Vol. 105, pp. 224-232, DOI: 10.1016/j.ijthermalsci.2016.03.004
2. M Krishnani and DN Basu (2017), Computational Stability Appraisal of Rectangular Natural Circulation Loop: Effect of Loop Inclination, Annals of Nuclear Energy, Vol. 107, pp. 17-30, DOI: 10.1016/j.anucene.2017.04.012

Mr. Satyendra N Baro

Dr. Harshad S Gaikwad

Publications in International Journals (from the thesis)

1. H Gaikwad, DN Basu and PK Mondal (2017), Non-linear Drag Induced Irreversibility Minimization in a Viscous Dissipative Flow Through a Micro-porous Channel, Energy, Vol. 119, pp. 588-600, DOI: 10.1016/j.energy.2016.11.020
2. H Gaikwad, DN Basu and PK Mondal (2017), Slip Driven Micro-pumping of Binary System with A Layer of Non-conducting Fluid under Electrical Double Layer Phenomenon, Colloids and Surfaces A: Physicochemical and Engineering Aspects, Vol. 518, pp. 166-172, DOI: 10.1016/j.colsurfa.2017.01.024
3. HS Gaikwad, PK Mondal, DN Basu, N Chimres and S Wongwises (2019), ­­Analysis of the Effects of Joule Heating and Viscous Dissipation on Combined Pressure-driven and Electrokinetic Flows in A Two-parallel Plate Channel with Unequal Constant Temperatures, IMechE Part E: Journal of Process Mechanical Engineering, Vol. 233, No. 4, pp. 871-879, DOI: 10.1177/0954408918809612

Publication in International Conference Proceedings (from the thesis)

1. H Gaikwad, DN Basu and PK Mondal (2015), Irreversibility Analysis of a Non-Newtonian Liquid Film Falling Down on Inclined Porous Heated Wall, Proc. Indian Chemical Engineering Congress (CHEMCON 2015), Guwahati, India, December 27-30, Paper ID FM-103
2. HS Gaikwad, C Borole, DN Basu and PK Mondal (2016), EMHD Micro-pumping of a Non-conducting Shear-thinning Fluid under EDL Phenomena, Proc. 6^th International and 43^rd National Conference on Fluid Mechanics and Fluid Power (FMFP2016), Allahabad, India, December 15-17, Paper No. 43

Mr. Chetan Borole

Publication in International Conference Proceedings (from the thesis)

1. C Borole and DN Basu (2015), Lattice Boltzmann Simulation of Mixed Convection in a Cavity with Parallel Moving Lids, Proc. Indian Chemical Engineering Congress (CHEMCON 2015), Guwahati, India, December 27-30, Paper ID FM-099

Mr. Pushkin Mittal

Mr. Sujeet Kaushik

Mr. Uddipta Singha

Dr. Sambit Majumder

Publication in International Conference Proceedings (from the thesis)

1. A Ghosh, S Majumder, G Natarajan and DN Basu (2018), Comparative Study of Two Immersed Boundary Approaches in the Lattice Boltzmann Framework, Proc. 7^th International and 45^th National Conference on Fluid Mechanics and Fluid Power (FMFP2018), Mumbai, India, December 10-12, Paper ID 800

Mr. Pankaj Kaushik

Mr. Arnab Ghosh

Publication in International Conference Proceedings (from the thesis)

1. A Ghosh, S Majumder, G Natarajan and DN Basu (2018), Comparative Study of Two Immersed Boundary Approaches in the Lattice Boltzmann Framework, Proc. 7^th International and 45^th National Conference on Fluid Mechanics and Fluid Power (FMFP2018), Mumbai, India, December 10-12, Paper ID 800

Ms. Alisha Daimari

Mr. Manjul K Mishra

Mr. Vijay B Shahapure

Publication in International Conference Proceedings (from the thesis)

1. V Shahapure, B Sarma, A Dalal and DN Basu (2018), High Speed Imaging and Analysis of Drop Formation, Proc. 7^th International and 45^th National Conference on Fluid Mechanics and Fluid Power (FMFP2018), Mumbai, India, December 10-12, Paper No. 680

Mr. Atul K Bhardwaj

Mr. Shakti Singh

Mr. Jayanta Gogoi

Mr. Soumitra Samai

Mr. Sourabh Panda

Mr. Krunal Gautam

Mr. Santosh K Kaithal

Mr. Arkaprava De

Ms. Priyakhee Kachari

Mr. Piyush