Small Pressure Loss Research Articles

Numerical Simulation Study of Self-rotary Blade Pipeline Mixers

According to the requirements of the online mixing, the new type of blade spin-rotary pipe mixer was designed innovatively and the feature of mixer was analyzed by the numerical simulation method. The result shows that the features of mixer with small size, simple structure, small pressure loss, easy maintenance and good mixing effect meet the usage requirements of online mixing.

Simulation and Optimization of Throttle Flowmeter with Inner-Outer Tube Element

Abstract In order to solve the dilemma between the smaller pressure loss and the larger flow measurement signal in traditional throttle flowmeters, a throttle structure with the inner-outer tube was designed and analyzed. The mathematical relationship model deduced from hydrodynamics showed there were three major parameters to determine the designed throttle structure. Furthermore, the optimal results were achieved by combining orthogonal test design and computational fluid dynamics by taking the ratio of differential pressure of inner-outer tube divided by that of anterior-posterior tube as the optimization goal. Finally, the simulation results with the best level parameters showed that the differential pressure of the anterior-posterior throttle could remain not only the smaller value among other parameters with the same structure of inner-outer tube. On the other hand, it was about one order magnitude less than differential pressure of V-cone flowmeter in the similar installation conditions with the flow velocity varying from 0.5 to 3.0 m/s. The designed inner-outer tube flowmeter can not only save manufacture costs, but also avoid the large sensitivity of pressure sensors, which may lead to a broader application in chemical and petrochemical enterprises.

伝播時間差式超音波流量計の精度に及ぼす速度分布の影響

The transit time ultrasonic flow meter (TOF) has been widely applied in industry due to its advantages, such as applicability to larger diameter pipe, small pressure loss, etc. Since the TOF derives flow rate from the change of the trantis time between two sensors, the accuracy of TOF is strongly influenced by velocity profile in the pipe. Velocity profile is influenced by not only the upstream condition but also the shape of tranducer pocket on the pipe wall. In this paper, in order to evaluate influence of velocity distribution on the accuracy of TOF, a system to measure the tiransit time and the velocity profile simulataneouly was developed. In experiments, an obstacle plate was installed to distort velocity profiles. The velocity profiles and their transit times of ultrasonic pulses were compared. As a result, line-averaged velocities calculated from the transit time were good agreement with the line-averaged velocities obtained by using UDM.

Interaction of counter rotating longitudinal vortices and the effect on fluid flow and heat transfer

The flow with longitudinal vortices is an important phenomenon in fluid dynamics and heat transfer. As the longitudinal vortices can potentially enhance heat transfer with small pressure loss penalty, vortex generators (VGs) which can generate longitudinal vortices are widely used to enhance the heat transfer of compact heat exchanger. In order to obtain a better heat transfer performance, researchers always try to punch lots of VGs out of the fin surface. But the increasing number of VGs is not necessarily linked with the rise in heat transfer performance augmentation. This is because the longitudinal vortices will interact with each other when they meet in the flow channel and the interaction between the longitudinal vortices is always disadvantage for the heat transfer enhancement. In this paper, numerical simulation of the interaction between two counter-rotating longitudinal vortices was carried out for the plate–fin heat exchanger using two rows of delta winglet type vortex generators. The effect of the transversal distance between the two VGs on the interaction of vortices and the effect of such interaction on heat transfer enhancement are studied in detail. New and important understandings about the interaction of counterrotating longitudinal vortices are obtained. The intensity of the longitudinal vortices and the heat transfer performance are sensitive to the interaction between longitudinal vortices. The interaction between counterrotating vortices decreases the average intensity of vortices, but does not necessarily decrease the heat transfer performance of longitudinal vortices. The common flow region formed between the counterrotating longitudinal vortices is beneficial to the heat transfer enhancement though interaction takes place in the common flow region between longitudinal vortices. An optimum arrangement of VGs exists for obtaining the best heat transfer performance. The arrangement of VGs with the transversal distance is zero must be avoided due to the serious interaction between longitudinal vortices.

Performance measurement analysis of various cone flow meters with various beta edge types and flow field parameters

The beta edge, as one part of the cone element in cone flow meters, has several types. Cone flow meters with different beta edges have different applications and measurement performance. The sharp angle, corner cut and arc are the most common forms of beta edges used in cone flow meters. Their structures are analyzed without changing other parameters. Through theoretical analysis of their hydromechanics, a conclusion can be drawn that the discharge coefficient linearity error and permanent pressure loss in cone flow meters can be predicted based on the consistency in the recirculation quantity and the dissipation function value. The research objects are cone flow meters with different beta edge forms whose inner tube diameter is 100mm and whose β values are 0.45, 0.55 and 0.65. The cone wake flow field characteristics were obtained and analyzed using the CFD method. Different beta edges cause different changes to the recirculation quantity and the dissipation in the cone wake flow region. Based on the theoretical prediction, the corner cut beta edge has the best discharge coefficient linearity error and relatively small permanent pressure loss. The accuracy of this prediction was experimentally verified. The experimental results demonstrate that the sharp-angle beta edge achieves the best performance in mechanical processing consistency, while the arc beta edge is the worst.

Research Status and Prospects of Resonant-type Hydraulic Pulsation Attenuators

Pressure pulsation is generally considered as the main source of vibration and noise, attenuating the pressure pulsation in an appropriate method has a very important significance for reducing vibration and noise in the hydraulic system. Due to the effectiveness in attenuating the pressure pulsation near the nature frequency, small pressure loss, conversion of many kinds, low cost and high reliability, resonant-type hydraulic pulsation attenuators have been widely used in practice. After summarizing the research status, the resonant-type hydraulic pulsation attenuators are classified into three categories:Helmholtz resonator, multiple-chamber type and fluid-structure coupled vibration type, research progress and performance of each category are expounded respectively. Comparisons are conducted among the performance characteristics of each category resonance-type pulsation attenuator to facilitate the users to chose and design them properly. For the deficiency of current technology, the focus direction of the further research is elaborated and it is concluded that good compactness, nice versatility, excellent adaptability of attenuation frequency is the future trend of development of resonant-type hydraulic pulsation attenuator. Finally, a resonant-type pulsation attenuator of new topology structure is proposed, this kind of attenuator can flexibly adjust its shape to fit the demanding space requirements.

Ground source heat pumps: should we use single U-bend or coaxial ground exchanger loops?

Ground source heat pumps are becoming more common as traditional energy costs rise. Innovative pipe loop configurations promise increased performance and efficiency. The coaxial ground loop is among these new systems. The working fluid flows through a pipe to the depth of the system and returns to the surface through a larger annulus surrounding the delivery pipe. This study compares the coaxial and the single U-bend. By use of numerical CFD modelling, it was found that the coaxial performs both better than the U-bend but also exhibits a smaller pressure loss over equal lengths. It was found that the residence time of the fluid in the loop affects the heat transfer greatly, but the U-bend was affected more than the coaxial. Thus, coaxial ground loops are essential for efficient design and performance.

10307 千鳥・碁盤目配列の違いが60度傾斜ティアドロップディンプル面の伝熱総合性能へ及ぼす影響

Recently, heat transfer enhancement with dimples is going attention in internal cooling of gas turbine blade because it induces small pressure loss for moderate heat transfer enhancement. In this study, staggered and in-line arrangements with 60deg angled teardrop-shaped dimples were experimentally compared. Heat transfer measurements were performed by using transient technique with compensation of three-dimensional heat conduction for the Reynolds number of, Re=16,000-36,000. In addition, flow visualization with combination of oil-film method and particle image velocimetry was performed for Re=26,000. At trailing edge of the dimples, the in-line arrangement showed higher heat transfer enhancement than the staggered arrangement. However, the friction factor also increased in the in-line arrangement, and heat transfer efficiency of the in-line arrangement was lower than that of the staggered arrangement.

Design and Implementation of Ultrasonic Flowmeter Based on CPLD

The ultrasonic flowmeter designed in this paper uses improved time difference method to measure the flow velocity, uses MSP430 as microprocessor. The flow velocity measurement equipment of the ultrasonic flowmeter is based on CPLD(EPM7064AE). The results of the experiments show that the ultrasonic flowmeter has many advantages such as low starting flow, small pressure loss, low consume, operation reliable, fully functional and so on. It has good potential application of market.

Granular bed filter: A promising technology for hot gas clean-up

Abstract Hot gas clean-up is important in the integrated gasification combined cycle (IGCC) and advanced pressurized fluidized-bed combustion (PFBC) technologies, which have greater efficiencies and less environmental impacts. The present work attempts to provide a general understanding of granular bed filters, a promising technology for hot gas clean-up. Granular bed filters can be designed as fixed beds, fluidized beds and moving granular beds, and in this paper, their characteristics and performances are summarized and discussed. A fixed bed granular filter has the disadvantage that gas flow must be stopped periodically for cleaning; however, its particle collection efficiency is greater than 99%. A fluidized bed filter provides continuous operation, though it is less efficient at removing small particles. Moving granular beds are promising for hot gas clean-up because typically, they operate continuously with high filtration efficiencies (over 97%) and small pressure losses.

Performance Comparison between Metal Honeycomb and Ceramic Honeycomb in Continuous Waste Heat Recovery

Metal Honeycomb (MH) is a plug-in unit for heat transfer enhancement, which has a large specific surface adjustable range, high heat conductivity and excellent geometric plasticity. The continuous waste heat recovery processes are simulated by FLUENT with inserted MH and ceramic honeycomb(CH) at the same shape and dimension. By comparing the heat exchange of MH with CH, it is found that the heat recovery device with MH has better performance and smaller pressure loss than that with CH.

A methodology for the geometric design of heat recovery steam generators applying genetic algorithms

This paper shows how the geometric design of heat recovery steam generators (HRSG) can be achieved. The method calculates the product of the overall heat transfer coefficient (U) by the area of the heat exchange surface (A) as a function of certain thermodynamic design parameters of the HRSG. A genetic algorithm is then applied to determine the best set of geometric parameters which comply with the desired UA product and, at the same time, result in a small heat exchange area and low pressure losses in the HRSG.In order to test this method, the design was applied to the HRSG of an existing plant and the results obtained were compared with the real exchange area of the steam generator. The findings show that the methodology is sound and offers reliable results even for complex HRSG designs.

Design and Performance of the Converging-Diverging Vortex Flowmeter

Design and Performance of the Converging-Diverging Vortex Flowmeter The converging-diverging structure is introduced to extend the lower limit of measurement of vortex flowmeters. As a compact device, the converging-diverging vortex flowmeter is proposed and designed, and its performance is studied experimentally. It is found that, first of all, an up to 51% extension of the lower measurement limit can be realized through the converging-diverging structure, compared with conventional vortex flowmeters; second, the converging-diverging vortex flowmeter with a trapezoidal bluff body has a larger Strouhal number and smaller pressure loss. The results suggest that the converging-diverging vortex flowmeter provides an alternative device especially suitable for the measurement of low-velocity fluids.

DEVELOPMENT OF A SUPERCRITICAL CO2BRAYTON ENERGY CONVERSION SYSTEM COUPLED WITH A SODIUM COOLED FAST REACTOR

Systematic research has been conducted by KAERI to develop a supercritical carbon dioxide Brayton cycle energy conversion system coupled with a sodium cooled fast reactor. For the development of the supercritical CO₂ Brayton cycle ECS, KAERI researched four major fields, separately. For the system development, computer codes were developed to design and analyze the supercritical CO₂ Brayton cycle ECS coupled with the KALIMER-600. Computer codes were developed to design and analyze the performance of the major components such as the turbomachinery and the high compactness PCHE heat exchanger. Three dimensional flow analysis was conducted to evaluate their performance. A new configuration for a PCHE heat exchanger was developed by using flow analysis, which showed a very small pressure loss compared with a previous PCHE while maintaining its heat transfer rate. Transient characteristics for the supercritical CO₂Brayton cycle coupled with KALIMER-600 were also analyzed using the developed computer codes. A Na-CO₂ pressure boundary failure accident was analyzed with a computer code that included a developed model for the Na-CO₂ chemical reaction phenomena. The MMS-LMR code was developed to analyze the system transient and control logic. On the basis of the code, the system behavior was analyzed when a turbine load was changed. This paper contains the current research overview of the supercritical CO₂ Brayton cycle coupled to the KALIMER-600 as an alternative energy conversion system.

High Performance Recuperator With Oblique Wavy Walls

A series of numerical simulation of the flow and heat transfer in modeled counterflow heat exchangers with oblique wavy walls has been made toward optimal shape design of recuperators. The effects of oblique angles and amplitudes of the wavy walls are systematically evaluated, and the heat transfer and pressure loss characteristics are investigated. It is found that counter-rotating streamwise vortices are induced by the wavy walls, and the flow field has been drastically modified due to the intense secondary flow. By using the optimum set of oblique angle and wave amplitude, significant heat transfer enhancement has been achieved at the cost of relatively small pressure loss, and the j∕f factor becomes much larger than that of straight square duct or conventional compact recuperators. When thermal coupling of hot and cold fluid passages is considered, the heat transfer is found to be strongly dependent on the arrangement of counterflow passages. The total heat transfer surface area required for a given pumping power and heat transfer rate can be reduced by more than 60% if compared to the straight square duct.

Incorporating reliability analysis into the design of passive cooling systems with an application to a gas-cooled reactor

A time-dependent reliability evaluation of a two-loop passive decay heat removal (DHR) system was performed as part of the iterative design process for a helium-cooled fast reactor. The system was modeled using RELAP5-3D. The uncertainties in input parameters were assessed and were propagated through the model using Latin hypercube sampling. An important finding was the discovery that the smaller pressure loss through the DHR heat exchanger than through the core would make the flow to bypass the core through one DHR loop, if two loops operated in parallel. This finding is a warning against modeling only one lumped DHR loop and assuming that n of them will remove n times the decay power. Sensitivity analyses revealed that there are values of some input parameters for which failures are very unlikely. The calculated conditional (i.e., given the LOCA) failure probability was deemed to be too high leading to the identification of several design changes to improve system reliability. This study is an example of the kinds of insights that can be obtained by including a reliability assessment in the design process. It is different from the usual use of PSA in design, which compares different system configurations, because it focuses on the thermal–hydraulic performance of a safety function.

Laminar flow and heat transfer in a periodic trapezoidal channel with semi-circular cross-section

Computational fluid dynamics (CFD) has been used to study fully developed laminar flow and heat transfer behaviour in periodic trapezoidal channels with a semi-circular cross-section. The trapezoidal elements are characterised by their wavelength (2 L), channel diameter ( d), radius of curvature of bends ( R c), the amplitude (2 A) and the length of the straight section ( B) with results reported for Reynolds numbers ( Re) up to 400, as well as for a range of geometric configurations ( 0.525 ⩽ R c d ⩽ 1.3 , 3.6 ⩽ L d ⩽ 12 , 0.17 ⩽ B L ⩽ 1 , 0.125 ⩽ A L ⩽ 1 ) at Re = 200. This generic geometry takes a variety of shapes with limiting forms of a regular square serpentine ( B = 2 A = L) and a zig-zag or saw-tooth ( B → 0). The flow in these channels is characterised by the formation of Dean vortices following each bend. As the Reynolds number is increased, stronger vortical flow patterns emerge and these vortices lead to efficient fluid mixing and high rates of heat transfer. Constant wall heat flux (H2), constant axial heat flux with peripherally constant temperature (H1) and constant wall temperature (T) boundary conditions are examined for a fluid with a Prandtl number of 6.13. Higher rates of heat transfer with relatively small pressure loss penalty are found relative to fully developed flow in a straight pipe, with heat transfer enhancements of up to four at the highest Reynolds number. In addition to presenting channel enhancements the stackability of channels on a plate is considered. The concepts of area enhancement (based solely on geometric factors) and heat transfer intensification, the product of the heat transfer enhancement and the area enhancement, are introduced and used to compare different geometrical configurations. The swept zig-zag pathway provided the greatest intensification of heat transfer in a multi-channel plate structure.

A220 色彩場中の固体粒子・気泡可視化トレーサー追跡による三次元速度場測定

The phenomena of the turbulent coherent structures and collapse of vortex are indispensable to realize high performance in heat transfer with a small pressure loss. Not only time-mean thermo- and fluid- dynamics but also unsteady and sequential 3D-phenomena are very important to study and control these phenomena in engineering applications. The most percentage of heat transfer enhancement were given birth for very short time period, when the turbulent structure just come and make effect on the heat transfer field near wall. But the time-dependent correlations between unsteady fluid and heat transfer fields are still unknown, which are most interesting and exciting to investigate experimentally. In this study, the three-dimensional velocity measurement system would be improved with multi-color field by the illumination optics for liquid crystal projectors and image processing for the detection of 3-D velocity vector. The unsteady collapse processes of periodic vortex by plate are investigated near wall region on the plane, and are shown by graphic figures. The results also are shown about the effects of unsteady velocity field with the adding the micro-bubbles near wall for control.

Determination of dynamic and sliding friction, and observation of stick-slip phenomenon on compacted polymer powders during high-velocity compaction

Dynamic friction, sliding friction, and the stick-slip phenomenon have been studied on compacted polymer powders during high-velocity compaction. It is particularly important from a practical point of view to distinguish the stick-slip mechanism and the sliding mechanism which occur concurrently. A practical experimental system has been successfully developed to study the dry frictional force and to measure the sliding coefficient between the polymer powder particles and the die wall during high-velocity compaction. Two new components have been introduced as relaxation assists to improve the compaction process by reducing the frictional forces. It was found that the relaxation assist device leads to an improvement in the polymer powder compaction process by giving a more homogeneous opposite velocity and a better locking of the powder bed in the compacted form with less change in dimensions. The subsequent movement of the particles can be reduced and the powder bed attains a higher density with a minimum total elastic spring-back. The relative time of the stick-slip phenomenon during the compacting stage is also reduced so that the time needed to transfer from an intermittent stick-slip state to a smooth sliding state is reduced and the powder bed slides smoothly. It was found that the dynamic, dry frictional force is intermittent (stick-slip mechanism) at low compaction rates but that at high compaction rates is becomes more smooth (sliding mechanism). Both mechanisms depend on the nature of the powder and on the compaction conditions. At the beginning of the compaction stage, the sliding coefficient decreases due to an increase in the radial to axial stress ratio until the maximum pressure has been reached. During the reorganization stage, more time is needed for large particles to move, rotate and slide due to their relatively large diameter and mass. As a result, the reorganization stage is extended and the stick-slip phenomenon is observed more with increasing particle size. Much better transfer of the pressure throughout the powder bed and less loss of pressure lead to a higher sliding coefficient due to the overall friction during the compaction process. It was found that the sliding coefficient is proportional to the density. A more homogeneous density distribution in the compacted powder and a smaller pressure loss during compaction has a major influence on the sliding coefficient and on the quality of the compacted material.

Evaluation of earth-to-air heat exchangers with a standardised method to calculate energy efficiency

In designing an earth-to-air heat exchanger (EAHX), a decision on design goals has to be made. If the air flow is given by the ventilation system and the construction site is known, the question is: is it more important to achieve a high specific energy performance based on the surface area of an EAHX, a high adoption of air temperature to ground temperature or a very small pressure loss? This paper deals with the performance of three EAHXs for mid European office buildings in service, with the aim of characterising their efficiency. A general method to compare EAHXs in operation will be introduced. First, the temperature behaviour is described by plots over time and characteristic lines, and compared by standardised duration curves. Second, the energy gain is illustrated by standardised graphs. Third, a parametric model is used to provide general efficiency criteria. Thermal efficiency should be defined by both the dynamic temperature behaviour and energy performance.