Faculty Publications
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Item Transient analysis of subcritical/supercritical carbon dioxide based natural circulation loop with end heat exchangers: experimental study(Springer Verlag service@springer.de, 2017) Yadav, A.K.; Ramgopal, M.; Bhattacharyya, S.Carbon dioxide (CO2) based natural circulation loops (NCLs) has gained attention due to its compactness with higher heat transfer rate. In the present study, experimental investigations have been carried out to capture the transient behaviour of a CO2 based NCL operating under subcritical as well as supercritical conditions. Water is used as the external fluid in cold and hot heat exchangers. Results are obtained for various inlet temperatures (323–353 K) of water in the hot heat exchanger and a fixed inlet temperature (305 K) of cooling water in the cold heat exchanger. Effect of loop operating pressure (50–90 bar) on system performance is also investigated. Effect of loop tilt in two different planes (XY and YZ) is also studied in terms of transient as well as steady state behaviour of the loop. Results show that the time required to attain steady state decreases as operating pressure of the loop increases. It is also observed that the change in temperature of loop fluid (CO2) across hot or cold heat exchanger decreases as operating pressure increases. © 2017, Springer-Verlag Berlin Heidelberg.Item Failure of a Cooling Water Pump Shaft(Springer, 2021) Sondar, P.R.; Kumar, J.K.R.; Chawla, S.; Dsilva, P.C.; Hegde, S.R.This study investigates the failure of an industrial cooling water pump which experienced a drive shaft failure. As per the fail-safe design, during adverse loading of the shaft, key should fail by shear. The key, if fails, can be easily replaced to resume the operation of the pump. However, this investigation reveals that both the key and the shaft failed due to materials processing issues. A detailed failure analysis was carried out including design calculations, visual inspection, dye penetrant inspection, magnetic particle inspection, hardness test, microstructural analysis, and fractography. The study found that the hardness of the shaft varied radially from the core to the surface. The subsurface of the shaft near the keyway, happened to be significantly softer than the key. During operation, the keyway widened by plastic deformation and caused rattling of the key. Due to rattling and vibration, the key developed numerous fatigue cracks and eventually failed by crack linkages. The shaft eventually failed by torsional shear near the midpoint of the keyway. The analysis adjudged hardness variation in the shaft due to materials processing issues as the root cause of the failure. © ASM International 2020.Item 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.