Faculty Publications
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Item Stability analysis of Tesla valve based natural circulation loop for decay heat removal in nuclear power plants(Institute of Electrical and Electronics Engineers Inc., 2019) Chandavar, R.A.In Nuclear power plants, the process of Decay heat removal is very crucial for safe operation of the plant. Passive methods such as using Natural Circulation Loops make the process reliable and cheaper. However, such systems are subjected to instability when both heater and condenser are horizontally positioned. One of the methods to overcome such difficulties is to use a Tesla valve. A Tesla valve is a one way valve with no moving parts which allows fluid to flow easily in one direction but provides a very high impedance in opposite direction. The present study deals with numerical analysis of single phase natural circulation loop with and without Tesla valve having water as the fluid. The loop with Tesla valve stabilizes about 100 seconds earlier than loop without Tesla and incorporation of Tesla results in unidirectional circulation every time. Hence Tesla valve can be used in the loop for stability without appreciable flow resistance. © 2019 IEEE.Item 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.Item Supercritical CO2 flow instability in natural circulation loop: CFD analysis(Elsevier Ltd, 2021) Wahidi, T.; Chandavar, R.A.; Yadav, A.K.Three-dimensional computational fluid dynamics (CFD) simulation on a supercritical CO2 based natural circulation loop (scCO2-NCL) is carried out to explore the effects of various parameters (i.e., pressure and heat inputs) on the loop's transient and stability behaviour. Results show that for supercritical CO2, there is a threshold point that decides the flow's nature. Lower than threshold heat inputs flow shows repetitive-reversal flow while at higher heat input the flow changes to stable or single-direction flow. With an increase in heat input, the system attains stability for a given operating pressure. In addition, a possible mechanism for continuous flow oscillation and measurement of instability with different pressure in unstable loops is also proposed in this study. It is found that the Nusselt number decreases with an increase in operating pressure for given heat input. Obtained simulation results are validated with the two existing correlations and found a good agreement. © 2021 Elsevier Ltd