Outlet Position Research Articles

Effects of the outlet position of splitter blade on the flow characteristics in low-specific-speed centrifugal pump

To elucidate the influences of the outlet position of splitter blades on the performance of a low-specific-speed centrifugal pump, two different splitter blade schemes were proposed: one located in the middle of the channel and the other having a deviation angle at the trailing edge of splitter blade toward the suction side of the main blade. Experiments on the model pump with different splitter blade schemes were conducted, and numerical simulations on internal flow characteristics in the impellers were studied by means of the shear stress transport k- ω turbulence model. The results suggest that there is a good agreement between the experimental and numerical results. The splitter blade schemes can effectively optimize the structure of the jet-wake pattern and improve the internal flow states in the impeller channel. In addition, the secondary flow and inlet circulation on the pressure surface of main blade, the flow separation on the suction side of splitter blade, the pressure coefficient distributions on blade surface can achieve an evident amelioration when the trailing edge of splitter blade toward the suction side of the main blade is mounted at an appropriate position.

Evaluation of a Compact Coaxial Underground Coal Gasification System Inside an Artificial Coal Seam

The Underground Coal Gasification (UCG) system is a clean technology for obtaining energy from coal. The coaxial UCG system is supposed to be compact and flexible in order to adapt to complicated geological conditions caused by the existence of faults and folds in the ground. In this study, the application of a coaxial UCG system with a horizontal well is discussed, by means of an ex situ model UCG experiment in a large-scale simulated coal seam with dimensions of 550 × 600 × 2740 mm. A horizontal well with a 45-mm diameter and a 2600-mm length was used as an injection/production well. During the experiment, changes in temperature field and product gas compositions were observed when changing the outlet position of the injection pipe. It was found that the UCG reactor is unstable and expands continuously due to fracturing activity caused by coal crack initiation and extension under the influence of thermal stress. Therefore, acoustic emission (AE) is considered an effective tool to monitor fracturing activities and visualize the gasification zone of coal. The results gathered from monitoring of AEs agree with the measured data of temperatures; the source location of AE was detected around the region where temperature increased. The average calorific value of the produced gas was 6.85 MJ/Nm3, and the gasification efficiency, defined as the conversion efficiency of the gasified coal to syngas, was 65.43%, in the whole experimental process. The study results suggest that the recovered coal energy from a coaxial UCG system is comparable to that of a conventional UCG system. Therefore, a coaxial UCG system may be a feasible option to utilize abandoned underground coal resources without mining.

Flow field in shallow reservoir with varying inlet and outlet position

ABSTRACTShallow reservoirs are used for multiple purposes, such as storm water retention and trapping of sediments. Reliable predictions of the flow fields are necessary to inform the design and operation of these structures. Using numerical simulations, we performed a systematic analysis of the influence of the location of the inlet and outlet on the flow fields developing in rectangular shallow reservoirs of various sizes. Depending on the relative location of the inlet and outlet with respect to the reservoir centreline, contrasting flow patterns are obtained, involving either no flow reattachment, or a jet reattached on either of the reservoir sidewalls. The results reveal also the occurrence of bi-stable flow configurations, i.e. different steady state flow fields are reached depending on the flow history. This is of high relevance for the design of shallow reservoirs as such configurations should certainly be avoided to achieve a robust hydraulic sizing of the reservoir.

Numerical and Experimental Study of CPU Cooling with Finned Heat Sink and Different P.C. Air Passages Configurations

This study investigated numerically and experimentally fluid flow and heat transfer in the desktop PC. Three patterns of the positions of air inlet and outlet were tested to find the best one for cooling. The computer components in the present study are CPU, finned heat sink, power supply, motherboard, CD, HDD and fans. Three components which were generate heat are CPU, motherboard and power supply and there were two openings for air inlet and two for air outlet. The air inlet velocities were 1.2, 1.8, 2.4 m/s with constant CPU fan velocity. The studied parameters were the changed of inlet air velocity, powers of CPU, motherboard and PSU and the positions of inlet air. The numerical results obtained are found in a good agreement with the experimental results. The experimental results show that the maximum temperature was 81 at 16.5 W and 1.2 m/s. Numerical results showed that the CPU temperature reaches 89.6 at 18.5 W and 1.2 m/s. From the results, it was found that; the temperatures of the main components (PSU and motherboard) affected little by CPU power and vice versa, the finned heat sink has higher cooling efficiency and the pattern 1 was the best pattern for CPU cooling.

Numerical Investigation of a Coupled Passive Cooling System Earth to Air Heat Exchange and Solar Chimney in Hot Arid Zone

The papers present a theoretical work on coupled passive cooling system, earth-to air heat exchange and high inertia well insulated solar chimney attached to the building south wall with direct outlet. The system was supposed to be used for summer cooling in hot arid zone in Ghardaia city in the south of Algeria. An investigation on the effects of the systems variable parameters on the cooling efficiency were carried out for hot summer days, these variable parameters were; Pipe: buried depth, cross section, length, disposition, number, and inlet outlet cross sections. Chimney: top and bottom sections, orientation, height, inlet outlet sections and positions, chimney wall insulation and thermal inertia. A numerical simulation carried out during summer days for two similar well insulated buildings, the first one with the above mentioned passive cooling system and the second without any passive features as a reference building, the buildings were assumed located in Ghardaia hot arid climate in the south of Algeria, in order to optimize the above cited variable parameters for the two coupled passive systems.

Numerical study on temperature fluctuation of upper plenum in FBR with a more realistic model

The thermal fatigue caused by the temperature fluctuation is more serious in FBR than that in PWR due to thermal characteristic. Limited by the ability of the computer, the simplified jet models were used to study the temperature fluctuation in published literature, which can not fully reflect the real characteristic of temperature fluctuation of upper plenum in FBR. In present study, the temperature fluctuation of upper plenum with a more realistic model (i.e. three heads of assemblies and the part of central column) in FBR was simulated with LES method. By comparison, the velocity and temperature fields are more complex in a more realistic model than that of the simplified jet model. The characteristic of temperature fluctuation was obtained around the central column. In a more realistic model, the fluid produces intense mixing near interface of the adjacent different temperature regions, which lead to severe temperature fluctuation. The distributions of temperature and temperature fluctuation intensity are asymmetric. The temperature field is divided into three regions with high temperature range θ = 195–285° for the three kinds of temperature inlet conditions, while that is divided into two regions with high temperature range θ = 75–285° for two kinds of temperature inlet conditions. The changes of temperature and temperature fluctuation intensity are complicated by the influence of the head of assembly in the coordinate directions. The position of the most intense oscillation appears in the upper position of the head outlet. However, near the bottom of the central column, the thermal stratification and temperature fluctuation are still relatively obvious with the temperature difference about 30–40 K and the amplitude about 0.1–0.15 times of the maximum inlet temperature difference. Meanwhile, the obvious dominant frequency does not appear. The energy of temperature fluctuation is distributed in a wide frequency range f < 20 Hz.

A CFD approach to assess the effects of different opening combinations in poultry houses

ABSTRACT The aim of this study was to use computational fluids dynamics (CFD) to evaluate hygiene and comfort conditions in function of temperature level and ammonia (NH3) concentration during the night in commercial poultry houses used in Brazil and countries with tropical and subtropical climates. Four models with different curtain heights and different air inlet and outlet positions were used, adopting the open building typology without thermal insulation. The validated CFD model did not present statistical differences from the experimental data, making it possible to use this model to predict the behavior in the four proposed cases. This model can be used to improve the internal conditions of the poultry facilities during the night and could be an important tool to reduce energy consumption and generate better conditions for animal production of chicks over 21 days old.

Numerical study of transport and particle deposition inside buildings

Increasingly, we must reduce our energy consumption related to the ventilation system of habitable environments while improving the indoor air quality. Our work concerns the study of particulate matter inside buildings and more specifically the pollution transport phenomena. A numerical study of particle transport inside a ventilated room (30m3room) was made using STAR CD software to solve the airflow in the domain and an in-house code to calculate the trajectories of solid particles in a three-dimensional turbulent flow. We analyze then the influence of ventilation systems (filtration, flow rate, inlet and outlet positions) on the concentration of indoor air particles. By using prediction tools, we carried out several numerical simulations, and then summarized the results. The main objective of this numerical study is to present the potential of this type of predictive tool that, in addition to determining the trajectories of particles, allow us to address the residence time of particles in the atmosphere, monitor particle-wall deposition and to study the spatial heterogeneity of particle concentrations.

食堂を併設した業務用厨房の換気・空調設計システムに関する研究 （第5報）排気フードに対する調理機器および空調吹出しの設置位置に関する調査

食堂を併設した業務用厨房の換気・空調設計システムに関する研究 （第5報）排気フードに対する調理機器および空調吹出しの設置位置に関する調査

Applying Isothermal Injection Moulding Process in the Manufacturing of Polymer Composite Reinforced with NiTi Shape Memory Alloy

SMART materials have gained several applications in industries, especially aeronautical and biomedical. Therefore, the fabrication process of these materials must present quality in the completion and dimensioning, in addition to well established mechanical properties. In this sense, the Resin Transfer Molding (RTM) process is presented as an alternative to the manufacture of such products. This process presents advantages compared to other methods, such as, product quality and low cost. Thus, this work aims to model and simulate numerically the manufacturing process of polymer composite reinforced with NiTi shape memory alloy by RTM using the Ansys CFX commercial software. Results of pressure, velocity and volume fractions fields of the phases are presented and discussed. It was verified that the process parameters, like injection pressure and resin inlet and air outlet positions influenced the total time of the process and final product quality.

Mathematical Simulation of the Processes of Thermal and Chemical Pollution inside Industrial Premises in Case of Emergency Situation

The purpose of this scientific paper was to create numerical models and develop the methods on their basis for computation of the chemical and thermal pollution of air inside industrial premises when the failure occurs; these also allow us to analyze the chemical and thermal pollution taking into account those weighty factors that affect this process. To simulate thermal pollution of air inside the premises we use the energy equation. To describe the chemical pollution of air we use 2D model that enables the computation of the migration of pollution agent inside the premises. To solve this problem we use the space width-averaged equation of a gradient type. The air flow rate field inside the premises induced by the working ventilation is calculated on assumption that the migration of air inside the premises is potential. The numerical integration of the equation for the velocity potential and Poisson equation is conducted using A.V. Samarskii alternatively triangle method. For numerical integration of the impurity transfer equation, the energy equation and the turbulence transfer equation alternatively-triangle implicit difference diagrams are used. Each difference equation corresponds to the record of balance ratio for the reference volume (the difference cell). The unknown value is calculated at each step using the explicit formula of point-to-point computation. This scientific paper gives constructed computer models and the efficient methods developed on their basis that are used for computation of the thermal and chemical pollution inside industrial premises in case of anthropogenic accidents. Developed computation methods allow the numerical model to take into account any arrangement and any shape of the process equipment and the position of air inlets and outlets.

Fluid dynamics simulation for design on sludge drying equipment

Sludge drying equipment is a key component in the sludge drying disposal, the structure of drying equipment directly affects the drying disposal of the sludge, so it is necessary to analyse the performance of the drying equipment with different structure. Fluent software can be very convenient to get the distribution of the flow field and temperature field inside the drying equipment which reflects the performance of the structure. In this paper, the outlet position of the sludge and the shape of the sludge inlet are designed. The geometrical model of the drying equipment is established by using pre-processing software Gambit, and the meshing of the model is carried out. The Eulerian model is used to simulate the flow of each phase and the interaction between them, and the realizable turbulence model is used to simulate the turbulence of each phase. Finally, the simulation results of the scheme are compared and the optimal structure scheme is obtained, the operational requirement is proposed. The CFD theory provides a reliable basis for the drying equipment research and reduces the time and costs of the research.

Experimental investigation on clocking effect of vaned diffuser on performance characteristics and pressure pulsations in a centrifugal pump

Clocking effects can generally have a great influence on the operational state of centrifugal pumps. In order to analyze the effects of the positions of the vaned diffuser relative to the annular volute on the performance characteristics and the pressure pulsations of a centrifugal pump, experimental tests were carried out at three different relative positions. Frequency domain and time-frequency domain of the pressure pulsations were obtained using the Welch’s power spectral density estimate and the short-time Fourier transform (STFT) methods, respectively. The diameter mode analysis was applied to explain the dominant frequency induced by rotor-stator interaction. The results showed that the centrifugal pump can obtain the highest efficiency when the diffuser was fixed at position A, where the diffuser was rotated 90 degrees in counterclockwise direction from position B. The maximum difference in the efficiency between 0.9Qd and 1.1Qd was 1.5% under three different diffuser positions. The pressure pulsations in the volute were determined not only by the impeller-diffuser interaction but also by the diffuser-volute interaction. Furthermore, nonlinear frequency existed in the frequency domain of the pressure pulsations at the volute outlet. The relative positions of the diffuser had great effect on the dominant frequency and the amplitudes of the decomposed frequencies of the pressure pulsations. A comparison of the amplitudes of the main frequencies of the pressure pulsations showed that the transient pressure on the volute had the lowest pulsations when the trailing edge of the diffuser reached the left corner of the volute outlet (position B).

Design and CFD modelling of the anodic chamber of a continuous PhotoFuelCell reactor for water treatment

Abstract A continuous PhotoFuelCell (PFC) reactor was proposed, designed and modelled using computational fluid dynamics (CFD). The important PFC reactor parameters such as hydrodynamics, radiation field and surface kinetics were modelled using the CFD model in order to simulate the events within the PFC reactor. Additionally, the formulated CFD model was used to predict the performance of the anodic chamber of PFC reactor by varying the inlet, outlet and photoanode positions prior to selecting the optimum design for real physical PFC reactor fabrication. The effect of variation in flow distribution over a wide range of Reynolds (Re) numbers, 200

Flow complexity in open systems: interlacing complexity index based on mutual information

Flow complexity is related to a number of phenomena in science and engineering and has been approached from the perspective of chaotic dynamical systems, ergodic processes or mixing of fluids, just to name a few. To the best of our knowledge, all existing methods to quantify flow complexity are only valid for infinite time evolution, for closed systems or for mixing of two substances. We introduce an index of flow complexity coined interlacing complexity index (ICI), valid for a single-phase flow in an open system with inlet and outlet regions, involving finite times. ICI is based on Shannon’s mutual information (MI), and inspired by an analogy between inlet–outlet open flow systems and communication systems in communication theory. The roles of transmitter, receiver and communication channel are played, respectively, by the inlet, the outlet and the flow transport between them. A perfectly laminar flow in a straight tube can be compared to an ideal communication channel where the transmitted and received messages are identical and hence the MI between input and output is maximal. For more complex flows, generated by more intricate conditions or geometries, the ability to discriminate the outlet position by knowing the inlet position is decreased, reducing the corresponding MI. The behaviour of the ICI has been tested with numerical experiments on diverse flows cases. The results indicate that the ICI provides a sensitive complexity measure with intuitive interpretation in a diversity of conditions and in agreement with other observations, such as Dean vortices and subjective visual assessments. As a crucial component of the ICI formulation, we also introduce the natural distribution of streamlines and the natural distribution of world-lines, with invariance properties with respect to the cross-section used to parameterize them, valid for any type of mass-preserving flow.

Mixed magnetohydrodynamic convection in a Cu-water-nanofluid-filled ventilated square cavity using the Taguchi method: A numerical investigation and optimization

In this paper, the optimal condition of mixed magnetohydrodynamic convection in a ventilated square cavity filled with a Cu-water nanofluid with different positions of inlet and outlet port is analyzed. To serve the purpose, the L16 (43) orthogonal Taguchi array is used by means of the Taguchi method. Discretization of the governing equations is obtained through the finite volume method and then solved with the SIMPLE algorithm. A very effective mode, namely the Taguchi method, is used for the L16 (43) orthogonal Taguchi array. The effects of Richardson number (0.01-10), Hartmann number (0-50), and inlet and outlet positions (0-0.9 H) at \(\Phi\) = 1% are investigated. The entire analysis is performed for fixed Grashof number 104. It is found that the mean Nusselt number decreases by increasing the Richardson number, Hartmann number and the position of the inlet port, whereas the position of the outlet port has an increment effect on the mean Nusselt number. The optimal distance of outlet port position from the upper wall of the cavity is 0.9H at Richardson number 0.01, while the Hartmann number of optimal design for heat transfer is noted as 30. Comparison with existing studies is made as a limiting case of the considered problem.

Air Distribution Analysis and Design of Air Duct for B10 Railway Refrigerated Car

Aiming at the problems of the air flow of railway refrigerated transport equipment, the air distribution of the B10 railway refrigerated car was optimized. This paper find the best position of air supply outlet in the car, the main part of the outlet should be placed at the distance from the position of air return side 7300mm until the tail of the car. The research has been applied and the effect is good.

Airflow Analysis in Policlinic and Lobby Space for Prevention of Airborne Infection in General Hospitals

This study analyzes the types of space in the polyclinic and lobby spaces of hospitals, which are thought to be exposed to secondary airborne infections within hospitals. A hospital, which has space where the human traffic from the polyclinic overlaps with that of the lobby (space type II), was selected as the subject of this study. The air current distribution in the polyclinic and lobby areas are analyzed using the calculation program Star-ccm+. The air current distribution in the existing air-conditioned space is analyzed using T·A·B (Testing, Adjusting, Balancing) measured values. The result proved the possibility of secondary airborne infections caused by mixing of the air currents from the polyclinic and lobby in the upper and middle air layers. Five improvement suggestions in terms of changing the position of air inlets and outlets are proposed in this study. Among them, [ALT-3] the arrangement wherein outlets are placed on the first and third lines and inlets are placed on the second line is expected to significantly reduces the possibility of airborne infections, as the air currents in the lower, middle, and upper layers in the polyclinic and lobby spaces are not intermixed.

Numerical Analysis of Ward’s Flow Field and Pollutant Distribution and Its Impact of Patients and Visitors

This paper mainly uses CFD method to simulate the ward internal environment, including contaminant distribution, velocity field and temperature filed. Using Gambit to establish a standard ward physical model. Based on the model, using Fluent to calculate, then get the ward’s comprehensive flow field. On this basis, analysis the influence of personnel’s thermal comfort and health, to optimize the ward air distribution form, adjustment of inlet and outlet position put to provide theory basis.

Numerical and Experimental Analysis of Airflow in a Multi-Duct Cleaning System for a Rice Combine Harvester

Abstract. In order to improve the cleaning quality and efficiency of a rice combine harvester, a cleaning system comprising a cen-trifugal fan and four outlet ducts was developed. Three multi-duct centrifugal fans with the same rotor but different up-per outlet positions and volute walls were studied numerically and experimentally to evaluate the impact of the upper outlet on the inner flow field distribution of the fan. Computational fluid dynamics (CFD) was used to analyze the veloc-ity profiles, flow rate, internal velocity, and pressure of the centrifugal fan. Experiments were performed using hot-wire anemometers to measure the velocity at the four outlets of the fan to validate the simulations. CFD simulations were used to perform detailed flow visualization, velocity profile and flow rate estimation, and internal velocity field and pressure field analysis. Special attention was paid to the effect of the upper outlet on the inner flow field distribution and on achieving a balanced airflow division between the four outlets. It was observed that the internal field distribu-tion and the mass flow rate division between the four outlets can be greatly influenced by the upper outlet position. The optimal structure of the multi-duct centrifugal fan was obtained for the rice combine.