Browsing by Author "Ramana Murthy, K.V."

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    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.
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    Experimental investigation on heat transfer coefficients and frictional pressure drop during R134a condensation inside a plate-fin heat exchanger with wavy fin
    (Begell House Inc., 2018) Ramana Murthy, K.V.; Chennu, C.; Ashok Babu, T.P.; Luo, X.
    This paper presents the heat transfer coefficients and frictional pressure drops measured during the saturated vapor condensation of R134a inside a small plate-fin heat exchanger with wavy fin surface for air-conditioning systems in aircraft. The experiments were carried out at three different saturated temperatures (34°C, 38°C and 42°C). The effects of the saturation temperature, heat flux and mass flux on the mean condensation heat transfer coefficient and core frictional pressure drop were investigated experimentally and discussed in detail. The condensation heat transfer coefficients and frictional pressure drops are compared with serrated fin surfaces obtained in previous experiments. The correlations for heat transfer coefficient and frictional pressure drop during downward flow condensation of R134a inside the plate-fin heat exchanger with wavy fin are developed based on the experimental data. Compared with the serrated fins for saturated conditions of R134a at same mass flux and saturated temperature/pressure conditions, it is found that although the wavy fins have low condensation heat transfer coefficients, its two-phase frictional pressure drop is even lower than that of the serrated fins. Therefore, if the pressure drop limitation is critical, the wavy fins can be a good selection. © 2018 International Heat Transfer Conference. All rights reserved.