scholarly journals A Novel Dehumidification Strategy to Reduce Liquid Fraction and Condensation Loss in Steam Turbines

Entropy ◽  
2021 ◽  
Vol 23 (9) ◽  
pp. 1225
Author(s):  
Yan Yang ◽  
Haoping Peng ◽  
Chuang Wen
Keyword(s):  
Two Phase Flow ◽  
Liquid Fraction ◽  
Turbine Blades ◽  
Suction Side ◽  
Phase Region ◽  
Condensation Process ◽  
Phase Flow ◽  
Steam Turbines ◽  
Two Phase ◽  
Nonequilibrium Condensation

Massive droplets can be generated to form two-phase flow in steam turbines, leading to erosion issues to the blades and reduces the reliability of the components. A condensing two-phase flow model was developed to assess the flow structure and loss considering the nonequilibrium condensation phenomenon due to the high expansion behaviour in the transonic flow in linear blade cascades. A novel dehumidification strategy was proposed by introducing turbulent disturbances on the suction side. The results show that the Wilson point of the nonequilibrium condensation process was delayed by increasing the inlet superheated level at the entrance of the blade cascade. With an increase in the inlet superheated level of 25 K, the liquid fraction and condensation loss significantly reduced by 79% and 73%, respectively. The newly designed turbine blades not only remarkably kept the liquid phase region away from the blade walls but also significantly reduced 28.1% averaged liquid fraction and 47.5% condensation loss compared to the original geometry. The results provide an insight to understand the formation and evaporation of the condensed droplets inside steam turbines.

Stability Prediction of the Nuclear Turbine Blades During Wet Steam Nonequilibrium Condensation Process

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Bing Guo ◽  
Weixiao Tang
Keyword(s):  
Turbine Blades ◽  
Condensation Process ◽  
Equivalent Stiffness ◽  
Wet Steam ◽  
Two Phase ◽  
Equivalent Damping ◽  
Novel Method ◽  
Phase Temperature ◽  
Nonequilibrium Condensation ◽  
The Stability

Stability of the nuclear turbine blades is difficult to be accurately predicted because the wet steam load (WSL) as well as its induced equivalent damping and stiffness during nonequilibrium condensation process (NECP) is hard to be directly calculated. Generally, in design, NECP is assumed as equilibrium condensation process (ECP), of which the two-phase temperature difference (PTD) between gaseous and liquid is ignored. In this paper, a novel method to calculate the WSL-induced equivalent damping and equivalent stiffness during NECP based on the combined microperturbation method (MPM) and computational fluid dynamics method (CFDM) was proposed. Once the WSL-induced equivalent damping and equivalent stiffness are determined, the stability of the blade-WSL system, of which the blade was modeled by a pretwisted airfoil cantilever beam, can then be predicted based on the Lyapunov's first method. Besides, to estimate the effects of PTD, comparisons between the WSL-induced equivalent damping and equivalent stiffness as well as the unstable area during NECP and ECP were presented. Results show that the WSL-induced equivalent damping and equivalent stiffness during NECP are more sensitive to the inlet boundary due to the irreversible heat transfer caused by PTD during NECP. Accordingly, the unstable area during NECP is about three times larger than during ECP.

Computational Method for Characterization of a Microchannel Heat Sink Involving Two-Phase Flow

2005 ◽  
Author(s):  
Kanchan M. Kelkar ◽  
Suhas V. Patankar ◽  
Sukhvinder Kang
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Two Phase Flow ◽  
Phase Region ◽  
Heat Fluxes ◽  
Computational Method ◽  
Phase Flow ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Solid Region

Microchannel heat sinks are being increasingly considered for the cooling of electronic equipment because of their ability to absorb high heat fluxes directly from the heat-dissipating components in a compact manner with a low thermal resistance. In this study, a computational method is presented for the analysis of conjugate heat transfer and two-phase flow in a heat sink containing a single microchannel. It involves a two-domain solution of the three-dimensional conduction within the solid region and the one-dimensional two-phase momentum and energy transfer within a microchannel. The nonlinear coupling between the two domains that occurs through the heat exchange at the walls of the microchannels is handled using an iterative calculation. Analysis of the flow and heat transfer in the microchannel is based on the homogenous flow assumption that is deemed to be accurate for the flow of low surface tension coolants such as methanol, isobutane, and HFC’s. Representative single and two-phase correlations are used for the calculation of the friction factor and the heat transfer coefficient. The computational model is applied for the prediction of the performance of a microchannel heat sink over a range of mass flow rates. The results of the analysis show the important physical effects that govern the performance of the microchannel heat sink involving two-phase flow. These include the acceleration of the flow in the microchannel in the two-phase region that influences the pressure drop through it and the two-phase enhancement of heat transfer that determines the temperature field within the solid region.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.

FLUTE: FLUORESCENT TECHNIQUE FOR TWO-PHASE-FLOW LIQUID-FRACTION MEASUREMENTS

1992 ◽  
Vol 118 (1) ◽  
pp. 237-249 ◽  
Author(s):  
S. ANGELINI ◽  
W.M. QUAM ◽  
W.W. YUEN ◽  
T. G. THEOFANOUS
Keyword(s):  
Two Phase Flow ◽  
Liquid Fraction ◽  
Phase Flow ◽  
Two Phase ◽  
Fluorescent Technique

scholarly journals Flow Regimes and Transitions for Two-Phase Flow of R152a During Condensation in a Circular Minichannel

2021 ◽  
Vol 9 ◽  
Author(s):  
Na Liu ◽  
Qian Zhao ◽  
Zhixiang Lan
Keyword(s):  
Flow Regime ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Cooling Water ◽  
Saturation Temperature ◽  
Flow Regimes ◽  
Condensation Process ◽  
Phase Flow ◽  
Two Phase ◽  
Water Mass Flow Rate

Two-phase flow regimes were experimentally investigated during the entire condensation process of refrigerant R152a in a circular glass minichannel. The inner and outer diameters of the test minichannel were 0.75 and 1.50 mm. The channel was 500 mm long to allow observation of all the two-phase flow regimes during the condensation process. The experiments used saturation temperatures from 30 to 50°C, a mass flux of 150 kg/(m2·s) and vapor qualities from 0 to 1. The annular, intermittent and bubbly flow regimes were observed for the experimental conditions in the study. The absence of the stratified flow regime shows that the gravitational effect is no longer dominant in the minichannel for these conditions. Vapor-liquid interfacial waves, liquid bridge formation and vapor core breakage were observed in the minichannel. Quantitative measurements of flow regime transition locations were carried out in the present study. The experiments also showed the effects of the saturation temperature and the cooling water mass flow rate on flow regime transitions. The results show that the annular flow range decreases and the intermittent and bubbly flow ranges change little with increasing saturation temperature. The cooling water mass flow rate ranging from 38.3 kg/h to 113.8 kg/h had little effect on the flow regime transitions.

Fundamental and Higher-Mode Density-Wave Oscillations in Two-Phase Flow

1972 ◽  
Vol 94 (2) ◽  
pp. 189-195 ◽  
Author(s):  
G. Yadigaroglu ◽  
A. E. Bergles
Keyword(s):  
Heat Capacity ◽  
Atmospheric Pressure ◽  
Single Phase ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Region ◽  
Flow Instabilities ◽  
Phase Flow ◽  
Two Phase ◽  
Density Wave Oscillations

This paper treats the oscillatory two-phase flow instabilities commonly referred to as density-wave oscillations. A dynamic analysis of the single-phase region of a boiling channel, accounting for wall heat capacity and the effect of pressure variations on the movements of the boiling boundary, is summarized. Experiments conducted with a Freon-113 channel at atmospheric pressure revealed the existence of “higher-mode” oscillations. These appeared at high subcoolings and low power levels and were characterized by unexpectedly short periods that were fractions of the transit time. The presence of the higher modes and other observations are explained in terms of the dynamic behavior of the boiling boundary.

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