Effects of temperature-density coupled property corrections on internal flow fields in high-temperature centrifugal pumps

Analysis of the Effects of Mixed-Flow Pump Inlet Structure on Pressure Pulsations and Energy Transport Characteristics

To investigate the influence of inlet structure optimization on pressure pulsation and energy transport characteristics in mixed-flow pumps, this study employed experimental and numerical calculation methods to analyze both original and optimized models. The SST-SAS turbulence model was selected for flow field computation. The experimental and numerical results showed that inlet optimization increased the head at the design condition by 1.52 m, improved the efficiency by 5.38%, and reduced the pressure pulsation amplitude by more than 90%. Analysis of energy transport term distribution characteristics within the pump revealed the mechanism behind pulsation intensity improvement: the pressure propulsion power distribution in the impeller became more stable, while the Lamb vector divergence dissipation regions and enstrophy dissipation regions substantially decreased, thereby increasing the proportion of pressure propulsion power contribution. The enhanced energy transport characteristics and improved flow field stability in the impeller region collectively optimized energy conversion performance within the impeller.

Study on the Influence of Medium Temperature on the Performance of a Space Micropump

The present work examines how variations in working fluid temperature govern the hydrodynamic behavior of a space-rated micropump. Using perfluorotriethylamine as the operating medium, three-dimensional CFD simulations employing the SST k-ω turbulence closure were carried out across a broad thermal spectrum, and the resulting flow physics were interpreted through entropy generation analysis. Based on the entropy production theory, the influence laws of different inlet temperatures on the external characteristics, internal characteristics, and flow loss characteristics of the micropump were quantitatively analyzed. The results show that temperature mainly affects the micropump performance by changing the viscosity and density of the working fluid. At low temperatures, the fluid viscosity increases significantly, leading to increased flow resistance, intensified internal friction, reduced head and efficiency, and increased shaft power. As the temperature increases to 0 °C and above, the viscosity change tends to moderate, and the external characteristic parameters tend to stabilize. The internal characteristic analysis shows that under low-temperature conditions, the high-pressure region in the impeller area expands and the turbulent kinetic energy decreases, but the flow separation is to a certain extent suppressed. The region near the volute tongue and the impeller outer edge are the main areas of entropy production loss, and their entropy production rates increase significantly with decreasing temperature. Moreover, at low temperatures, the high entropy production regions expand from locally isolated distributions to continuous large-scale distributions. The impeller outer edge dominates total entropy production, driven by peak fluid linear velocity and intense shear interaction with the volute wall. The findings elucidate how working fluid temperature governs both the hydrodynamic performance and the irreversible loss characteristics of the micropump. These insights can directly inform the engineering design of thermal management loops intended for orbital applications under severe temperature swings.

Engineering Assessment of Dynamic Thermophysical Property Effects on Wellbore Temperature and Pressure Prediction under Lost Circulation

During drilling in deep, high-temperature, high-pressure (HTHP) wells, lost circulation can significantly alter annular flow distribution, wellbore heat transfer balance, and pressure response, making conventional constant-property models inadequate for accurate wellbore temperature and pressure prediction. In this study, we develop a transient wellbore-formation temperature-pressure (T-P) coupling model for known lost circulation conditions. The model accounts for flow redistribution caused by fluid loss, transient wellbore-formation heat transfer, wellbore pressure response, and the dynamic evolution of thermophysical properties within a unified computational framework. The governing equations are solved using a fully implicit finite-difference scheme, in which temperature, pressure, and fluid properties are iteratively updated. Because the loss scenarios are constrained by field-measured loss data, recorded loss volumes, or prescribed operating conditions, the model is intended as an engineering-scale tool for evaluating post-loss redistribution of wellbore temperature and pressure. The model is validated against classical models and field temperature and pressure measurements under normal and lost circulation conditions. The results show that dynamic thermophysical properties significantly affect wellbore temperature and pressure predictions during lost circulation. Compared with the constant-property model, the dynamic-property model reduces the bottomhole temperature (BHT) prediction error to 1.06%, provides a conservative upper-bound estimate of BHT, and avoids systematic overestimation of bottomhole pressure (BHP). Lost circulation reduces annular flow rate and disturbs the wellbore heat transfer balance, leading to nonlinear redistribution of temperature and pressure. Sensitivity analysis indicates that BHT is mainly controlled by density and specific heat capacity, with relative contributions of 42.89% and 39.11%, respectively, whereas BHP is dominated by density, with a contribution of 96.59%. Full-factorial interaction analysis further shows that the interaction between density and specific heat capacity is the key coupled factor affecting BHT, and higher specific heat capacity reduces the sensitivity of BHT to density variation by approximately 28%. Extended sensitivity analyses of inclination angle, drillstring eccentricity, high equivalent circulating density (ECD) conditions, and loss rate show that the model can characterize temperature and pressure response differences under complex wellbore configurations and operating conditions. The results provide engineering support for post-loss T-P assessment, loss-zone diagnosis, well-control safety-margin evaluation, and circulation-parameter optimization under lost circulation.

Two-Phase Flow Distribution in Plate Heat Exchangers Using a Coupled CFD–Distributed Parameter Model

Plate heat exchangers (PHEs) play a critical role in the energy efficiency of heat pump systems. However, non-uniform two-phase flow distribution across parallel channels remains a key limitation, as it may cause local dryout and degrade heat transfer performance. To address the limitations of existing prediction approaches, a hybrid modeling framework coupling computational fluid dynamics (CFD) simulations with a distributed parameter model is developed. The model is validated against experimental data under 12 representative operating conditions. The results show that the average prediction errors for the total mass flow rate, pressure drop, and heat transfer rate are within 3%, ±10%, and ±5%, respectively. The influences of refrigerant outlet conditions and inlet distributor geometry on flow distribution uniformity are systematically investigated, identifying the dominant factors governing pressure drop and the mechanism by which distributor orientation improves uniformity. Quantitative optimization shows that an orifice orientation of 225° reduces flow non-uniformity by 67.8% and enhances the heat transfer rate by 4.33% compared with the distributor-free design. The proposed method is robust across various operating scenarios and provides a reliable, quantitative tool for optimizing PHE inlet distributor designs.

Enhancement of heat and mass transfer through temperature-sensitive viscosity in power-law binary fluids

Development of Reynolds-number-based Correction Factors for Low Specific-speed Centrifugal Pumps Using Energy Loss Analysis

Accurate prediction of centrifugal-pump performance under viscous operating conditions remains challenging, particularly for low specific-speed pumps operating at low Reynolds numbers. This study develops a Reynolds-number-based correction-factor framework derived from a physically based energy-loss analysis. The method explicitly accounts for major internal loss mechanisms, including hydraulic losses, disk friction, leakage flow, recirculation, mixing and diffusion losses, slip-factor deviation, and blade blockage. The model was calibrated using water-test data from an FM-50 centrifugal pump at 1200 rpm and validated using an independent dataset at 900 rpm. The validation results showed accurate head prediction, with and . Efficiency prediction showed larger deviation, with percentage points, reflecting the sensitivity of efficiency to measurement uncertainty and combined loss mechanisms. After validation, the model was extended to viscous-flow conditions and used to derive compact analytical correction factors for head and efficiency as functions of Reynolds number. The proposed expressions showed strong cross-validation performance within the investigated range, with mean for the head correction factor and for the efficiency correction factor. Comparison with ANSI/HI, KSB, and Gülich methods shows that the proposed formulation follows the expected Reynolds-number-dependent trend while providing a more physically interpretable basis for viscous-performance correction. The proposed method offers a practical alternative to conventional correction charts for low specific-speed centrifugal pumps operating under viscous or low-Reynolds-number conditions.