http://dspace.dtu.ac.in:8080/jspui/handle/123456789/109 2026-10-18T02:45:19Z 2026-10-18T02:45:19Z KUMAR, RAJESH ZUNAID, MOHAMMAD (SUPERVISOR) MISHRA, RADHEY SHYAM (CO-SUPERVISOR) http://dspace.dtu.ac.in:8080/jspui/handle/repository/23402 2026-10-16T06:36:33Z 2026-10-01T00:00:00Z

Title: NUMERICAL ANALYSIS AND OPTIMIZATION OF HYDROTHERMAL PERFORMANCE OF MICROCHANNEL HEAT SINK Authors: KUMAR, RAJESH; ZUNAID, MOHAMMAD (SUPERVISOR); MISHRA, RADHEY SHYAM (CO-SUPERVISOR) Abstract: The continuous increase in power density and miniaturization of modern electronic systems has intensified the demand for advanced thermal-management technologies capable of dissipating high heat fluxes while maintaining thermal reliability and energy efficiency. Although microchannel heat sinks have emerged as one of the most effective cooling technologies for electronic applications, their performance is often constrained by the competing requirements of heat-transfer enhancement, pressure-drop minimization, and thermodynamic efficiency. Consequently, the development of optimized cooling architectures capable of achieving superior thermo-hydraulic and exergetic performance remains a critical challenge in electronic cooling. To address this challenge, convergent-divergent microchannel heat sinks (CD-MCHS) were selected as the baseline cooling architecture because the periodic flow acceleration and deceleration induced by convergent-divergent passages can enhance fluid mixing, suppress thermal boundary-layer growth, and improve heat-transfer performance. The present research develops an integrated computational framework combining Computational Fluid Dynamics (CFD), Artificial Neural Networks (ANN), the Non Dominated Sorting Genetic Algorithm-II (NSGA-II), and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) for the multi-objective optimization of CD-MCHS. The optimization objective was to maximize thermal performance while minimizing entropy generation and thermodynamic irreversibility. The first phase of the investigation focused on the optimization of the baseline CD-MCHS geometry. The TOPSIS-selected configuration achieved a 20.1% enhancement in heat transfer performance and a 38.1% reduction in entropy generation compared with the conventional straight microchannel. Furthermore, the optimized geometry reduced the outlet temperature by approximately 8 K while exhibiting the lowest exergy destruction ratio (8.53%) and the highest exergy efficiency (91.47%). These findings demonstrate that geometric optimization alone can significantly enhance cooling performance while simultaneously improving thermodynamic behavior. Building upon the optimized CD-MCHS platform, three complementary passive enhancement strategies representing geometric modification (micro-pillars), coolant modification (tri-hybrid nanofluids), and porous-medium augmentation were systematically investigated to explore different mechanisms of thermal-performance Numerical Analysis and Optimization of Hydrothermal Performance of Microchannel Heat Sink P a g e | vii enhancement. For each enhancement strategy, ANN surrogate models were developed and coupled with NSGA-II and TOPSIS to identify the optimal configurations based on thermo-hydraulic and exergetic performance criteria. The optimized micro-pillar-enhanced CD-MCHS achieved a 71.45% increase in heat transfer performance with only a 15.64% increase in entropy generation, while reducing the maximum wall temperature by approximately 3.5 K. The optimized tri-hybrid nanofluid composition enhanced heat transfer by 16.36% while maintaining the lowest thermodynamic penalty among the enhancement techniques and reducing the maximum wall temperature by 1.89 K. In contrast, the optimized porous-medium configuration delivered the highest cooling capability, achieving a 265.65% increase in heat-transfer performance and approximately 7 K reduction in maximum wall temperature relative to the non-porous channel. However, this substantial thermal enhancement was accompanied by significantly higher entropy generation and exergy destruction due to increased flow resistance within the porous matrix. A comprehensive comparative assessment revealed that the three passive enhancement strategies represent distinct thermal-management philosophies. Porous media maximized cooling capability, whereas tri-hybrid nanofluids minimized thermodynamic penalties. The micro-pillar-enhanced CD-MCHS effectively bridged these two extremes by delivering substantial heat-transfer enhancement with moderate entropy-generation and exergetic penalties. Consequently, the micro-pillar configuration emerged as the most balanced passive enhancement strategy, offering the most favorable compromise among cooling effectiveness, thermodynamic efficiency, and pumping-power requirements. Overall, the present research demonstrates that the optimization of advanced microchannel heat sinks should not be guided solely by heat-transfer enhancement but must simultaneously consider hydrothermal and thermodynamic performance. The proposed CFD-ANN-NSGA-II-TOPSIS framework provides a robust methodology for the design and optimization of next-generation thermal-management systems. Furthermore, the findings establish convergent-divergent microchannel heat sinks as a promising platform for high-performance electronic cooling and provide practical design guidelines for advanced computing, power-electronic, and other energy-intensive applications.

2026-10-01T00:00:00Z JAIN, RAHUL KUMAR Singari, Ranganath M. (SUPERVISOR) SINGH, R.C. (CO-SUPERVISOR) http://dspace.dtu.ac.in:8080/jspui/handle/repository/23347 2026-10-16T06:30:07Z 2026-05-01T00:00:00Z

Title: STUDY OF LUBRICATED COLD ROLLING PROCESS USING BIO-DEGRADABLE OILS/EMULSIONS Authors: JAIN, RAHUL KUMAR; Singari, Ranganath M. (SUPERVISOR); SINGH, R.C. (CO-SUPERVISOR) Abstract: This study investigates the transition from mineral oil-based lubricants to biodegradable alternatives in cold rolling operations, emphasizing tribological performance, mechanical properties and its impact on environmental. The lubricant helps in decreasing the friction and makes comparatively smooth output in compare to dry friction rolling process. An exhaustive literature review has been carried out to develop research gaps and research objectives. Cold rolling of aluminium alloy 6061 has been carried out with different rolling parameters as rolling speed, reduction ratio and different lubricating conditions. Tribological properties has been analyzed with biodegradable oil-based oil/Emulsions (BB) as lubricant and compared with mineral oil-based oil/emulsion lubricant (MB). It has been carried out on Pin on Disc setup according to ASTM G99. Biodegradable lubricants derived from vegetable oils and synthetic esters demonstrate comparable tribological properties. The mechanical properties, such as yield strength, hardness, and surface finish, of rolled sheet also compared with both BB and MB lubrication. Rolling force and power consumption in cold rolling also compared with both the BB and MB lubrication as well as environmental impact. Both the oil/ emulsions had shown similar tribological properties.BB and MB oil/emulsion had been tested on a laboratory cold rolling mill in the cold rolling of aluminium strips.BB had 5-8 % greater rolling forces than MB, 6.3% higher power consumption; however, both emulsion systems resulted in similar results in surface finishes (Ra = 0.35 – 0.38 μm) and mechanical properties micro hardness and tensile properties (HV 65-75; TS 135-145 MPa) of the rolled sheet. Environmental evaluations indicated that BB are superior in terms of sustainability for biodegradability 87% vs. 18%; 40% lower COD. In summary, these results indicate that biodegradable palm oil-based emulsions can serve as technical alternatives and environmentally superior options for cold rolling aluminium, while providing the same level of quality and performance as mineral oil-based lubricants. Findings support the feasibility of adopting biodegradable lubricants in industrial cold rolling, aligning mechanical performance of the process with environmental sustainability objectives.

2026-05-01T00:00:00Z BATRA, LALIT Kumar, Sanjay (SUPERVISOR) Agrawal, Saurabh Kumar (CO-SUPERVISOR) http://dspace.dtu.ac.in:8080/jspui/handle/repository/23330 2026-10-16T06:25:51Z 2026-07-01T00:00:00Z

Title: MODELING AND OPTIMIZATION OF VEHICLE SUSPENSION BEHAVIOR FOR ENHANCED COMFORT Authors: BATRA, LALIT; Kumar, Sanjay (SUPERVISOR); Agrawal, Saurabh Kumar (CO-SUPERVISOR) Abstract: The Ride Comfort (RC), is an important parameter of Vehicle Performance & Occupant Safety that is directly influenced by the effectiveness of a vehicle's suspension system, Road Excitations and Bio-Dynamic Response of Human Body. The major sources of discomfort in vehicles are prolonged or Excessive Whole-Body Vibration transmitted to the Driver/Passenger via various road irregularities causing Fatigue, Back Pain & eventually Musculo-Skeletal and Neurological Disorders. The current research focuses on developing a Computational Model to simulate, analyze and control the transmission of vibrations from the Vehicle to the Occupants to improve the Ride Comfort through various Simulations, Controls and Optimizations. This study was developed through the development of a computational bond graph modeling for a 3 DOF quarter car model combined with a (4-DOF) lumped human biodynamic model which represents the head, upper torso, lower torso and pelvis (thigh) when seated on a vehicle in a static posture with no backrest. The models have the ability to provide a realistic representation of the transmission of vibrations from the road surface to the vehicle seat and then to the different parts of the human body. A simulation is created by applying deterministic and random excitations to the model that represent the variability of road surfaces (ISO 8608) classified as A, B, C and D with sine, trapezoidal and square waveforms. This type of excitation allows for a wide range of variability in the road conditions from very smooth highways to very uneven terrain driving environments. Time and frequency domain biodynamic response values are measured for each part of the human body and the vehicle body in response to various road excitations. Results demonstrate how the characteristics of the road surface affect the biodynamic response, providing important information regarding road roughness and its effect on human comfort. For enhanced comfort, a novel Bond Graph-based PID controller was developed to reduce vibrations generated from bumps. The Bond Graph is an effective modeling tool to represent multi-domain energy systems and their control hardware. The SYMBOL SHAKTI software is utilized to simulate an active vehicle suspension system, which is theoretically modeled as a combination of a 4-DOF iv Human Bio-Dynamic Model and a 3-DOF Quarter Automobile System. A comparison of the proposed PID controller's performance versus that of a passive model was performed. Time domain and frequency domain analyses of the systems' performance criteria were evaluated to determine the efficiency of the proposed PID controller suspension system. The results indicate that a substantial decrease in the vibration transmitted to the vehicle and the human body parts enhances ride comfort by the proposed Bond Graph PID controller model of the active vehicle suspension. In addition, the study introduced a Fractional Order PID (FOPID) controller with gain parameters optimized by Particle Swarm Optimization (PSO). The results indicated that both the Bond Graph-based PID controller and the PSO-optimized FOPID controller improve ride comfort compared to a passive vehicle system. The results also indicate that the PSO-optimized FOPID controller exhibited superior performance and achieved smoother dynamic responses over a wide range of frequencies. The research is further broadened to include an 11 DOF full car model linked to a 4 DOF human biodynamic model. A new integrated computer model is created using the bond graph method to evaluate the dynamic performance of a large road vehicle. First, 3-D models of all the individual vehicle bases, suspension units, tires, seats, and joints will be generated as bond graph elements with power ports that allow them to physically connect. This study displays the dynamic performance of a 4 DOF lumped human biomechanical model bonded to an 11 DOF full-car vehicle model utilizing a bond graph simulation method. The dynamic response of the bio dynamic human linked to a full car has been validated by ride comfort criteria based on ISO 2631:1997. The dynamic responses to various bumps in the time domain were simulated at different speeds (40 km/h) when the vehicle passed over identical sized (1m, 2m and 3.7m wide x 1m high) bumps. In addition, RMS responses were analyzed for varying vehicle speeds. The results depicted in the paper illustrate the extraordinary behavior of full-car vehicles. In the last stage of this study; the research will focus on developing an empirical mathematical model with Response Surface Methodology (RSM); that can be used to estimate ride comfort (RC) and road holding (RH) from the experimental data collected. In addition, a three-factor, three-level full factorial design was v implemented with twenty total experimental runs. The developed model was then evaluated to determine if it was adequate to provide accurate predictions by conducting an Analysis of Variance (ANOVA) with a 95% Confidence Level. The variables of interest included: Suspension stiffness coefficient (Ks), suspension damping coefficient (Cs), and tire stiffness (Kt); whereas the response variables were Ride Comfort (RC), and Road Holding (RH). The data showed that all three of the independent variable parameters (i.e., Ks, Cs, and Kt) significantly affect the two dependent variable parameters (i.e., RC and RH). Therefore, an optimal parameter combination for improved performance was identified as the best combination for improving ride comfort and better road holding characteristics.

2026-07-01T00:00:00Z SAHU, ROHIT Srinivas, Krovvidi (SUPERVISOR) Agrawal, Atul Kumar (CO-SUPERVISOR) http://dspace.dtu.ac.in:8080/jspui/handle/repository/23228 2026-10-16T06:09:41Z 2026-06-01T00:00:00Z

Title: DEVELOPMENT OF COMPOSITE USING ALUMINIUM, CERAMIC AND INDUSTRIAL WASTE Authors: SAHU, ROHIT; Srinivas, Krovvidi (SUPERVISOR); Agrawal, Atul Kumar (CO-SUPERVISOR) Abstract: Aluminium matrix composites (AMCs) have been the subject of a lot of scholarly interest as a lightweight structural material for aerospace and advanced engineering applications, mainly because of their high strength-to-weight ratio, wear resistance and high thermal stability. Among aluminium alloys, AA2024 is generally used in aerospace structures due to its outstanding specific strength and fatigue strength. In spite of this, its relatively low level of hardness and tribological performance restricts its range of applications to highly abrasive environments. Accordingly, the present study attempts to develop and characterize a hybrid aluminium matrix composite based on AA2024 reinforced with titanium diboride (TiB2), waste glass powder (WGP) and nano-copper oxide (Nano-CuO) particles. The main aim of this study is to developed AA2024-based hybrid composites using stir casting method and systematically understand the mechanical, tribological, microstructural and thermal characteristics of the composites using both experimental and computational methods. Composite samples were generated in 8 different formulations by varying amounts of TiB2 substitution of waste glass powder and keeping the nano-CuO as the reinforcement same at 0.25 wt.%. Mechanical characterization revealed a considerable improvement in strength and hardness with the addition of hybrid reinforcements. The optimum composition consisting of 5 wt.% TiB₂, 2.5 wt.% WGP, and 0.25 wt.% nano-CuO exhibited the highest ultimate tensile strength of 580.37 MPa and yield strength of 431.39 MPa compared with 495 MPa and 375 MPa for the base alloy. Similarly, flexural strength increased from 640 MPa to vi 803.37 MPa, while hardness improved from 137 HV to approximately 170 HV. However, a gradual reduction in ductility from 14% to 6% and a slight decrease in impact energy from 2.09 J to 1.91 J were observed, indicating a typical strength–toughness trade-off associated with ceramic particle reinforcement. Microstructural analysis using scanning electron microscopy and energy dispersive spectroscopy confirmed fairly particle distribution, grain refinement, and good interfacial bonding between the matrix and reinforcements. Fractographic studies found a mixed ductile-brittle type failure. Subsequent true stress-strain examinations supported the fact that the hybrid composites possess enhanced strain-hardening behaviour. Finite-element simulations based on the constitutive model of Hollomon showed good agreement with experimental data with the predictive discrepancy limited to 4%-5% thus verifying the reliability of the computational model. The tribological performance of the composites was investigated by assessing the influence of reinforcement content and process parameters, such as normal load, sliding velocity and sliding distance on the wear phenomenon. An optimization study using the Taguchi L16 orthogonal array showed high improvements in wear resistance and hardness due to the synergy of TiB2, WGP and nano-CuO addition. The minimum coefficient of friction obtained was 0.262 while the optimised wear rate, as checked by confirmatory tests, was 4.133 x10-3 g/m. Thermal expansion measurements also showed an increase in dimensional stability with the coefficient of thermal expansion reduced from 23.4 x 10-6 K-1 for the unreinforced alloy to around 21.8 to 22.4 x 10-6 K-1 in the reinforced composites. Overall, the fabricated hybrid AA2024 composites displayed enhanced mechanical strength, superior wear resistance and increased thermal stability which reveals their promising applicability to the advanced aerospace and high-performance engineering environment.

2026-06-01T00:00:00Z