Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
4 results
Search Results
Item Condensation heat transfer and pressure drop of R-134a saturated vapour inside a brazed compact plate fin heat exchanger with serrated fin(Springer Verlag service@springer.de, 2017) Ramana Murthy, K.V.; Chennu, C.; Ashok Babu, T.P.This paper presents the experimental heat transfer coefficient and pressure drop measured during R-134a saturated vapour condensation inside a small brazed compact plate fin heat exchanger with serrated fin surface. The effects of saturation temperature (pressure), refrigerant mass flux, refrigerant heat flux, effect of fin surface characteristics and fluid properties are investigated. The average condensation heat transfer coefficients and frictional pressure drops were determined experimentally for refrigerant R-134a at five different saturated temperatures (34, 38, 40, 42 and 44 °C). A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 22 kg/m2s. In the forced convection condensation region, the heat transfer coefficients show a three times increase and 1.5 times increase in frictional pressure drop for a doubling of the refrigerant mass flux. The heat transfer coefficients show weak sensitivity to saturation temperature (Pressure) and great sensitivity to refrigerant mass flux and fluid properties. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. Correlations are provided for the measured heat transfer coefficients and frictional pressure drops. © 2016, Springer-Verlag Berlin Heidelberg.Item Flow boiling heat transfer and pressure drop analysis of R134a in a brazed heat exchanger with offset strip fins(Springer Verlag service@springer.de, 2017) Amaranatha Raju, M.; Ashok Babu, T.P.; Chennu, C.The saturated flow boiling heat transfer and friction analysis of R 134a were experimentally analyzed in a brazed plate fin heat exchanger with offset strip fins. Experiments were performed at mass flux range of 50–82 kg/m2 s, heat flux range of 14–22 kW/m2 and quality of 0.32–0.75. The test section consists of three fins, one refrigerant side fin in which the boiling heat transfer was estimated and two water side fins. These three fins are stacked, held together and vacuum brazed to form a plate fin heat exchanger. The refrigerant R134a flowing in middle of the test section was heated using hot water from upper and bottom sides of the test section. The temperature and mass flow rates of water circuit is controlled to get the outlet conditions of refrigerant R134a. Two-phase flow boiling heat transfer and frictional coefficient was estimated based on experimental data for offset strip fin geometry and presented in this paper. The effects of mass flux, heat flux and vapour quality on heat transfer coefficient and pressure drop were investigated. Two-phase local boiling heat transfer coefficient is correlated in terms of Reynolds number factor F, and Martinelli parameter X. Pressure drop is correlated in terms of two-phase frictional multiplier ?f, and Martinelli parameter X. © 2017, Springer-Verlag Berlin Heidelberg.Item Investigation of flow boiling heat transfer and pressure drop of R134a in a rectangular channel with wavy fin(Elsevier Masson SAS 62 rue Camille Desmoulins Issy les Moulineaux Cedex 92442, 2020) Amaranatha Raju, M.; Ashok Babu, T.P.; Chennu, C.The saturated flow boiling heat transfer and pressure drop studies of R134a were experimentally investigated in a rectangular channel with wavy fin. Experiments were performed at mass flux range 30–50 kg m?2 s?1, heat flux range 11–18 kW m?2 and quality 0.26–0.8. The experimental data were obtained in a brazed test section. In preliminary step, single phase experiments were conducted to find out the j and f data of the wavy fin. In second step, two-phase flow boiling experiments were conducted to estimate the heat transfer and frictional coefficient based on experimental data. The trends of heat transfer and pressure drop with respect to mass flux, heat flux and quality were studied. Two-phase local boiling heat transfer coefficient is correlated in terms of Reynolds number factor F, and Martinelli parameter X. Pressure drop is correlated in terms of two-phase frictional multiplier, ?f and Martinelli parameter, X. © 2019 Elsevier Masson SASItem Thermal studies of a MEMS-based pressure sensor for aerospace applications(John Wiley and Sons Inc, 2025) Krishna, B.G.; Murthy, K.R.; Khan, K.Z.; Madav, V.; Ashok Babu, T.P.The main objective of this study is to enhance heat transfer for the reduction of temperature in MEMS-based piezoresistive high-temperature pressure sensors. The main parameter that affects the sensor performance especially for Aerospace applications is higher operating temperature because there are many electronic components and devices that may fail due to higher temperatures. Prevention of overheating of the electronic components in the sensor is a challenge; hence, the study of heat transfer from hydraulic fluid is of utmost importance. Different types of fin surfaces to enhance the heat transfer rate are studied using ANSYS CFD (computational fluid dynamics). CFD simulations and experiments are carried out to design novel high operating temperature pressure sensors for aerospace applications. This in turn improves performance due to internal thermo-piezoresistive amplification. In this paper, high-temperature pressure sensors are designed by CFD analyses and experimentally analyzed for a better understanding of the distribution of temperature in the pressure sensor and thermal variation in the sensor and observe the changes during analysis. Extended fin surface concepts are introduced for better heat transfer and to reduce the fluid temperature inside the sensor that is transferred to the electronic components. ANSYS CFD analysis is carried out to determine the temperature distribution and two models are identified for experimental validation. © 2024 Wiley Periodicals LLC.