Transient Flow and Pigging Operation in Gas-Liquid Two Phase Pipelines

For simulation of transient gas-liquid two phase flow, the continuity, momentum and energy equations for two fluids should be solved, which requires complex calculations. In oil and gas pipelines, it is possible to perform some simplifications on continuity and momentum equations. This will be done by using quasi steady state assumption for gas continuity equation and also local equilibrium momentum balance for both phases in some flow patterns such as stratified, annular, slug and bubbly flows. In this paper, simplified transient simulation with assumption of isothermal flow was utilized together with flow patterns transition criterion and tested against experimental data for verification of the results. For this purpose, a computer code was written and implemented as transient flow simulator. In this code, the one dimensional differential equations were discretized by semi- implicit finite difference method and solved by an iterative manner. Also, a model for pigging operation was developed to analyze the flow parameters in pipeline during and after pigging. The numerical results were compared with the experimental data and it is observed that agreement with experimental data is satisfactory from practical engineering stand point

Numerical Simulation of Pig Motion through Gas Pipelines

Pigs are utilized in pipelines to perform operations such as dewatering, cleaning and internal inspection for damages. Transient motion of pigs through gas pipelines has been simulated numerically in order to help engineers predict the variables related to pig motion such as estimating its speed, required driving pressure, and the amount of fluid bypass through the pig. In this paper, the continuity and linear momentum equations for compressible gas flows were discretized by finite difference method based on moving and staggered grids. These equations were solved together with dynamic equation for pig movement and the equation for modelling bypass flow. Besides, gas was considered both ideal and real. Test cases representing typical pigging operations in pipelines with or without flanges and branches were studied using the numerical model developed. The fluid flow and pig behaviour predicted by the model have a reasonable behaviour

Meeting the health needs of displaced people fleeing Ukraine: Drawing on existing technical guidance and evidence.

The invasion of Ukraine has unleashed a humanitarian crisis and the impact is devastating for millions displaced in Ukraine and for those fleeing the country. Receiving countries in Europe are reeling with shock and disbelief and trying at the same time to grapple with the reality of providing for a large, unplanned, unprecedented number of refugees mainly women and children on the move. Several calls for actions, comments and statements express outrage, the risks, and the impending consequences to life and health. There is a need to constantly assess the situation on the ground, identify priorities for health and provide guidance regarding how these needs could be addressed. Therefore, the Lancet Migration European Regional Hub conducted rapid interviews with key informants to identify these needs, and in collaboration with the World Health Organization Health and Migration Programme, summarized how these could be addressed. This viewpoint provides a summary of the situation in receiving countries and the technical guidance required that could be useful for providing assistance in the current refugee crisis

Review of nanomaterials in dentistry: interactions with the oral microenvironment, clinical applications, hazards, and benefits.

Interest in the use of engineered nanomaterials (ENMs) as either nanomedicines or dental materials/devices in clinical dentistry is growing. This review aims to detail the ultrafine structure, chemical composition, and reactivity of dental tissues in the context of interactions with ENMs, including the saliva, pellicle layer, and oral biofilm; then describes the applications of ENMs in dentistry in context with beneficial clinical outcomes versus potential risks. The flow rate and quality of saliva are likely to influence the behavior of ENMs in the oral cavity, but how the protein corona formed on the ENMs will alter bioavailability, or interact with the structure and proteins of the pellicle layer, as well as microbes in the biofilm, remains unclear. The tooth enamel is a dense crystalline structure that is likely to act as a barrier to ENM penetration, but underlying dentinal tubules are not. Consequently, ENMs may be used to strengthen dentine or regenerate pulp tissue. ENMs have dental applications as antibacterials for infection control, as nanofillers to improve the mechanical and bioactive properties of restoration materials, and as novel coatings on dental implants. Dentifrices and some related personal care products are already available for oral health applications. Overall, the clinical benefits generally outweigh the hazards of using ENMs in the oral cavity, and the latter should not prevent the responsible innovation of nanotechnology in dentistry. However, the clinical safety regulations for dental materials have not been specifically updated for ENMs, and some guidance on occupational health for practitioners is also needed. Knowledge gaps for future research include the formation of protein corona in the oral cavity, ENM diffusion through clinically relevant biofilms, and mechanistic investigations on how ENMs strengthen the tooth structure

Experimental investigations and correlation development of convective heat transfer in a rotating smooth channel

An experimental study has been carried out to investigate the effects of Coriolis force and centrifugal buoyancy force on convective heat transfer in a smooth cooling channel under rotating condition in a new rotation facility. The main motivation behind this work is to obtain required data for developing heat transfer correlations based on rotating state. In accordance with the open literature, four parameters, i.e.s Reynolds number, Rotation number, coolant Density Ratio and main flow direction were selected to study the influence on local heat transfer coefficient. Therefore, the investigation considered Reynolds number (Re) ranging from 5000 to 12,000, Rotation number (Ro) in the range of 0–0.15, Inlet Density Ratio (DR) between 0.04 and 0.1 and at the entry developing region of a square smooth channel in a new rotation test bench. Comprehensive experiment have been conducted to collect data on the local Nusselt number at the leading and trailing walls. The results show that the local heat transfer rate is enhanced by rotation on the trailing surface and reduced on the leading surface in outward flow due to symmetrical secondary vortex generated by Coriolis force. The centrifugal buoyancy effect is favorable to the heat transfer enhancement on both walls. Also, by utilizing the extensive experimental data, correlations for the local Nusselt number have been updated for the leading and trailing walls in ranges of the mentioned flow parameters, which can be used as an internal cooling boundary condition for numerical analysis of thermal stresses and cooling efficiency maximization for gas turbine blades

Numerical simulation of flow and thermal characteristics of harmonic pulsed laminar impinging streams

10.1002/apj.1700Asia-Pacific Journal of Chemical Engineering84607-61

Simulation of Drying Characteristics of Evaporation from a Wet Particle in a Turbulent Pulsed Opposing Jet Contactor

The motion and drying characteristics of a single particle in a novel two-dimensional pulsed opposing jet contactor (POJC) are modeled and discussed. Hot air is used as the drying medium. To simulate particle drying, the gas phase and dispersed phase conservation equations are considered in the Eulerian reference frame and the Lagrangian reference frame, respectively. The RNG turbulence model is used to determine the turbulent characteristics of the gas phase. The particle motion is described by the BBO (Basset-Boussinesq-Oseen) equation. The effects of the key parameters, such as the jet Reynolds number, amplitude of pulsation, frequency of pulsation, particle diameter, location of release of particle from one jet as well as velocity profile on residence time (RT) and particle penetration depth (PN) into the opposite jet, are examined. Results show that POJC has strong potential for particulate heat transfer as well as drying; it can improve evaporation rate relative to the corresponding steady OJC by up to 30% as a result of increased residence time in the impingement zone within the parameter ranges simulated. © 2013 Copyright Taylor and Francis Group, LLC

The Impact of Nanoparticles on Forced Convection in a Serpentine Microchannel

In this study heat transfer and fluid flow characteristics of Al2O3/water nanofluid in a serpentine microchannel is numerically investigated. A constant heat flux is applied on microchannel wall and a single-phase model has been adopted using temperature-dependent properties. The effects of pertinent factors such as Reynolds number (Re=10, 20, 50 and 100), particle volume fraction (=0(distilled water), 2, 4 and 8%) and heat flux (q=5, 10 and 15 W/cm2), on the velocity and temperature field, average heat transfer coefficient (havg), pressure drop (Δp), and thermal-hydraulic performance (η) are evaluated. The results show that the use of nanofluid causes increased velocity gradient near the wall which is more remarkable for φ = 8%. The results also reveal that the heat transfer rate increases as nanoparticle volume fraction and Reynold number increase and a maximum value 51% in the average heat transfer coefficient is detected among all the considered cases when compared to basefluid (i.e., water). It is found that a higher heat flux leads to heat transfer enhancement and reduction in pressure drop. Finally, thermal-hydraulic performance is calculated and it is seen that the best performance occurs for Re =10 and φ = 4%