Faculty Publications

Now showing 1 - 4 of 4

Thermal induced motion of functionally graded beams subjected to surface heating
(Ain Shams University, 2018) Malik, P.; Kadoli, R.
Thin beam of the functionally graded (FG) type subjected to a step heat input on one surface and insulated or exposed to convective heat loss on the opposite surface is under consideration for the evaluation of thermal induced motion. The dynamic displacement and dynamic thermal moment of the beam are analysed when the temperature gradient is independent of the beam displacement. The power law index dictates the metal–ceramic distribution across thickness of the beam and its effect on the thermal vibration of the beam is examined. The article discusses, in depth, the influence of various factors such as length to thickness ratio of beam, heat transfer boundary conditions, physical boundary conditions, and metal–ceramic combination on the thermal oscillations of FG beam. It is found that attenuation of the amplitude of static thermal deflection and superimposed thermal oscillations is a strong function of the metal–ceramic combination for the FG beam. © 2015 Faculty of Engineering, Ain Shams University
Comparative computational appraisal of supercritical CO2-based natural circulation loop: effect of heat-exchanger and isothermal wall
(Springer Science and Business Media B.V., 2020) Thimmaiah, S.; Wahidi, T.; Yadav, A.; Mahalingam, A.
Natural circulation loop (NCL) is a geometrically simple heat transfer device in which fluid flow occurs due to density gradient of loop fluid, induced by the temperature difference between the source and the sink. NCL has an inherent problem of instability caused by the combined effect of buoyancy, friction and inertia forces at varying operating conditions, and hence it requires an elegant solution of instability. The primary objective of the present work is to do a comparative study on the dynamic performance between two different configurations of NCL based on supercritical CO2, i.e. (i) NCL with isothermal heater and a cold heat-exchanger (ISO-CHX), and (ii) NCL with hot and cold heat-exchangers (HHX-CHX). To explore these NCLs, two-dimensional transient computational fluid dynamics studies have been carried out on the stability of supercritical CO2-based natural circulation loop. Results are obtained for different operating pressures and temperatures in the form of mass flow rate and velocity variation with respect to time. Results show the higher instabilities in both side heat-exchanger loop than an isothermal heater with heat-exchanger loop. At a lower rate of heat input at source in the HHX-CHX loop, the mass flow is bidirectional, whereas it is unidirectional in the ISO-CHX loop at all level of heat input. It is also observed that as pressure increases, flow instability also increases. Obtained results are validated with the published experimental and numerical data and found in good agreement. © 2020, Akadémiai Kiadó, Budapest, Hungary.
Stability enhancement of supercritical CO2 based natural circulation loop using a modified Tesla valve
(Elsevier B.V., 2020) Wahidi, T.; Chandavar, R.A.; Yadav, A.K.
This article deals with the comparative investigation of instability phenomenon in supercritical CO2 based regular natural circulation loop and a new modified Tesla natural circulation loop. Two-dimensional computational fluid dynamics simulation is carried out for square loops. Fluid flow behaviour and performance of both the loops are determined over a range of pressures (80–100 bar) and heat inputs (500–2000 W). Results show that the use of a modified Tesla valve leads to better stabilization for all supercritical pressures and heat inputs. It is also found that loop with Tesla mitigates the temperature and velocity oscillations without reducing the heat transfer performance. A good agreement with existing correlations is also obtained in the present study. The unidirectional fluid flow circulation achieved in loop with Tesla valve, makes it an efficient technique to combat instability. © 2020 Elsevier B.V.
Numerical Investigation to Analyze the Effect of Various Operating Parameters on the Thermal Characteristics of Heat Pipe
(John Wiley and Sons Inc, 2025) Jose, J.; Sutheesh, P.M.; Bandaru, B.; Gumtapure, V.; Hotta, T.K.
The heat pipe is one of the prime candidates in electronic thermal management due to its higher thermal performance and passive nature. The present study aims to develop a 3D mathematical model to simulate the thermal behavior of the heat pipe of length 380 mm under different operating conditions. Steady-state numerical simulations are performed to predict the effect of heat inputs (in the range of 10–50 W), the coolant flow rates (40 LPH, 25 LPH, and 10 LPH), and the coolant inlet temperatures (298.15, 293.15, and 288.15 K) on the heat pipe's thermal characteristics. The analysis reveals that by increasing the heat input from 10 to 50 W, the heat pipe's thermal resistance is reduced by 49.23%, with the same amount of augmentation in its evaporator heat transfer coefficient. The cooling water flow rate also significantly impacted the heat pipe's thermal resistance and heat transfer coefficient. The evaporator heat transfer coefficient decreased by 2.01% at 25 LPH compared to 10 LPH and increased by 1.68% at 40 LPH compared to 25 LPH. Additionally, with the increase in the cooling water inlet temperature from 288.15 K to 293.15 K, the heat pipe's evaporator heat transfer coefficient increased by 7.55%, and thermal resistance was reduced by 6.02%. This confirms the vivid influence of the input thermal energy and cooling water inlet temperature on the heat pipe's thermal characteristics, while the cooling water Reynolds number (flow rate) had a minimal influence on its operating conditions. Hence, this comprehensive analysis of using the heat pipe offers valuable insight for improving heat dissipation and thermal management in electronic devices. © 2025 Wiley Periodicals LLC.

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