Influence Of Fluid Parameters Research Articles

Local thermal conductivity of inhomogeneous nano-fluidic films: A density functional theory perspective

Combining the mean field Pozhar–Gubbins (PG) theory and the weighted density approximation, a novel method for local thermal conductivity of inhomogeneous fluids is proposed. The correlation effect that is beyond the mean field treatment is taken into account by the simulation-based empirical correlations. The application of this method to confined argon in slit pore shows that its prediction agrees well with the simulation results, and that it performs better than the original PG theory as well as the local averaged density model (LADM). In its further application to the nano-fluidic films, the influences of fluid parameters and pore parameters on the thermal conductivity are calculated and investigated. It is found that both the local thermal conductivity and the overall thermal conductivity can be significantly modulated by these parameters. Specifically, in the supercritical states, the thermal conductivity of the confined fluid shows positive correlation to the bulk density as well as the temperature. However, when the bulk density is small, the thermal conductivity exhibits a decrease-increase transition as the temperature is increased. This is also the case in which the temperature is low. In fact, the decrease–increase transition in both the small-bulk-density and low-temperature cases arises from the capillary condensation in the pore. Furthermore, smaller pore width and/or stronger adsorption potential can raise the critical temperature for condensation, and then are beneficial to the enhancement of the thermal conductivity. These modulation behaviors of the local thermal conductivity lead immediately to the significant difference of the overall thermal conductivity in different phase regions.

Semi-analytical dynamic modeling of parallel pipeline considering soft nonlinearity of clamp: A simulation and experimental study

Clamp is a crucial support structure to secure and connect the parallel pipeline system. Since the metal felt of the clamp is composed of metal rubber material, as well as the clamp structure using bolted connections, clamp is prone to cause nonlinear force during vibration. Nevertheless, no relevant paper has been reported to study the influence of soft nonlinearity of clamps on parallel pipelines. To bridge this gap, the present study introduces a novel semi-analytical dynamic model that effectively considers the influences of nonlinear clamps in parallel pipeline systems. The proposed model simulates the clamp's vertical hysteretic restoring force using the Bouc-Wen model. The clamp parameters are identified using Particle Swarm Optimization (PSO) with experimental and simulation errors as the objective function. Subsequently, the model is then validated by conducting modal and response tests. The numerical results are consistent with the experimental results. In order to prove the validation of the proposed model, experiments are conducted using dual clamps at different positions, and it can be observed that the nonlinear parameters of the clamps still meet the accuracy requirements. Moreover, the influences of fluid parameters on frequency are compared with the ANSYS software and the proposed model, and the influence trends exhibit consistency. By considering the nonlinear effects of clamps, the proposed model facilitates enhanced accuracy in predicting vibration responses.

Mathematical Model Research on the Influence of Fluid Parameter Characteristics on the Solid Fluidization Exploration Process of Hydrate Reservoir

Objective: In order to further study the characteristics of flow parameters in the wellbore during solid fluidization drilling, based on the physical model of solid fluidization exploration of hydrate reservoir, a gas-liquid-solid three-phase flow model is established during the drilling process. Methods: The parameter changes of wellbore pressure, section gas holdup, liquid volume fraction, temperature and wellbore hydrate decomposition rate under the influence of different wellhead choke pressure, displacement and drilling fluid density during solid fluidization are analyzed. Results: The analysis results of the case will show that under different wellhead choke pressures, hydrate begins to decompose at 400m to 500m, and with the increase in wellhead choke pressure, the wellbore pressure and the volume fraction of liquid and solid phase at the same position increase significantly, and the gas production rate and the gas volume fraction decrease. The results also show that under different drilling fluid rates, hydrate begins to decompose at 500m to 550m, and with the increase in drilling fluid rate, bottomhole pressure and wellbore temperature increase, the situation of hydrate decomposition becomes better, and gas volume fraction decreases. Conclusion: With the increase of drilling fluid density, hydrate begins to decompose at 500m to 600m, the wellbore temperature increases, and the hydrate decomposition is delayed. Meanwhile, the difference in the location of hydrate decomposition becomes smaller.

Numerical prediction of solid particle erosion in angle-cutting elbows with gas–solid flow

Angle-cutting elbows (ACEs) are important components of pipelines for fluid diversion and distribution. Severe erosion may occur on the internal walls of ACEs used to transport solid–gas/liquid flow. Erosion may cause pipeline failures. Therefore, the ACE erosion is a fundamental problem. However, the literature on the erosion characteristics and structural optimization of ACEs is rarely reported. This study conducts a numerical prediction of solid particle erosion in ACEs with gas–solid flow. Simulation models based on the two-way coupled Eulerian–Lagrangian approach and the E/CRC model are combined with particle-wall rebound models and a user defined function in the dispersed phase model. Simulation results are verified through a comparison with previously reported experimental results. The findings show that serious erosion occurs in the downstream part of the concave wall of ACE, whereas only slight erosion occurs on the convex wall of ACE. Therefore, anti-erosion measures should be adopted for the concave wall of ACEs. In addition, structural optimization of ACEs for erosion reduction is conducted. The optimal cutting angle is 40° > 50°, and the optimal non-dimensional cutting length is <1.05. The influence of fluid parameters on erosion characteristics is also determined. The erosion rate on the concave wall increases linearly with particle diameter and exponentially with inlet velocity.

Numerical simulation of gas-liquid two-phase flow in the micro-fracture networks in fractured reservoirs

The fracture network in fractured reservoirs is the main channel for fracturing fluid intrusion and gas flow, and the presence of liquid has a great influence on the gas flow pattern, and the gas flow shows more diversity in fluids with different properties such as fracturing fluid or formation water. In order to study the characteristics of gas-liquid two-phase flow in the microfracture network of the fractured gas reservoir, the topology of the microfracture network is simplified to T-junction and Y-junction. Based on the volume of fluid model, the gas-liquid two-phase flow interface is tracked. The model is solved by computational fluid dynamics software OpenFOAM, and the correctness of the model is verified by comparing it with laboratory microscopic experiment results. The flow characteristics of the gas phase in different fluids at the microscale and the influence of fluid parameters on flow pattern are analyzed. The results show that the properties of the liquid phase have a strong influence on the gas flow pattern, and the two-phase flow velocity and the properties of fluid parameters affect the gas flow to reach the stable state. The findings of this study can be used for reference to analyze the flow characteristics of gas in fracturing fluid and the flowback technology of fracturing gas well.

In-plane dynamic response of a hydraulic pipe subjected to random vibration

PurposeTo improve the transmission efficiency and reduce the damage to pipes in the hydraulic systems of tunnel boring machine subjected to random vibration, this paper aims to propose a novel dynamic characteristic analysis method that considers random vibration.Design/methodology/approachA fluid-structure interaction motion equation of the pipe is established by using Hamilton’s principle. The finite element method and discrete analysis method of random vibration are used to construct a model of the dynamic behavior of the pipe.FindingsThe influences of fluid parameters and external excitation parameters on the dynamic characteristics of pipes are analyzed. The experimental results are found to be in good agreement with the simulation results, which demonstrates that the proposed analytical method can provide a theoretical reference for the design and selection of hydraulic pipes subjected to random vibration.Originality/valueThe proposed method can be regarded as a future calculation method for pipes subjected to random vibration, and the transmission efficiency of the pipe can be improved.

Performance of Loaded Thermal Storage Unit with a Commercial Phase Change Materials based on Energy and Exergy Analysis

This work presents an energy/exergy analysis to investige performance of thermal storage unit which loaded with a commercial phase change material (Plus ICE H190). The influence of fluid parameters on the energy/exergy effectiveness was examined. The temporal changes of the energy and exergy rate and performace of the storage unit are obtained in the results. Latent heat principle is considered an efficient method to gain a higher effectiveness of system from an energy and exergy aspects. The fluid mass flow rate during charging and discharging periods were 2.50 kg/min and 1.26 kg/min, respectively. The results showed a significant increase of thermal resistance on the thermal storage unit performance. Fluid and phase change material show significant temperature difference on the rate of energy/exergy quantites and the time of melting or soldification. Ther results indicated that the average rate of energy and exergy were 1.3 kW and 0.54 kW, respectively. Wheras, energy and exergy average rate during discarging periods were 1.1 kW and 0.31 kW, respectively. Also, the global rate during the experimetal periods were about 84% and 54%, respectively.Article History: Received July 6th 2017; Received in revised form September 15th 2017; Accepted 25th Sept 2017; Available onlineHow to Cite This Article: Olimat, A.N., Awad, A.S., Al-Gathain, F.M., and Shaban, N.A.. (2017) Performance of Loaded Thermal Storage Unit With A Commercial Phase Change Materials Based on Energy and Exergy Analysis. International Journal of Renewable Energy Development, 6(3),283-290.https://doi.org/10.14710/ijred.6.3.283-290

Performance of Loaded Thermal Storage Unit with a Commercial Phase Change Materials based on Energy and Exergy Analysis

This work presents an energy/exergy analysis to investige performance of thermal storage unit which loaded with a commercial phase change material (Plus ICE H190). The influence of fluid parameters on the energy/exergy effectiveness was examined. The temporal changes of the energy and exergy rate and performace of the storage unit are obtained in the results. Latent heat principle is considered an efficient method to gain a higher effectiveness of system from an energy and exergy aspects. The fluid mass flow rate during charging and discharging periods were 2.50 kg/min and 1.26 kg/min, respectively. The results showed a significant increase of thermal resistance on the thermal storage unit performance. Fluid and phase change material show significant temperature difference on the rate of energy/exergy quantites and the time of melting or soldification. Ther results indicated that the average rate of energy and exergy were 1.3 kW and 0.54 kW, respectively. Wheras, energy and exergy average rate during discarging periods were 1.1 kW and 0.31 kW, respectively. Also, the global rate during the experimetal periods were about 84% and 54%, respectively.

Study on Influence of Fluid Parameters on Axial Coupled Vibration of Pipeline Conveying Multiphase Flow

Taking a slurry reservoir-pipeline-valve system as research object, axial dynamic vibrations of pipe system were induced by coupled hydraulic transient due to rapid closure of valve at the end of pipe. The influences of fluid parameters in multiphase flow, including void fraction, density ratio, and elastic modulus ratio between solid phase and liquid phase, on vibration behaviors of pipe system were analyzed. Results of this study show that wave velocities of pressure and stress can be attenuated evidently when void fraction in multiphase fluid is increased appropriately; meanwhile, the amplitudes of pressure fluctuation and pipe vibration are also weakened obviously. With the increase of density ratio between solid phase and liquid phase, the vibrational intension of pipe system becomes stronger and stronger. In this instance, the increments of vibrational energy mainly concentrate in fluid, which leads the pressure energy of fluid to rise up quickly. When elastic modulus ratio between solid phase and liquid phase increases, the total elasticity of fluid decreases gradually. At the same time, both pressure energy of fluid and vibrational intension of pipe are enhanced but the increments are very slight.