Experimental Studies of Nozzle/Diffuser Micropumps Using Enhancement Structure

2010 ◽  
Author(s):  
Kai-Shing Yang ◽  
Tzu-Feng Chao ◽  
Ing Youn Chen ◽  
Chi-Chuan Wang
Keyword(s):  
Experimental Studies ◽  
Maximum Flow ◽  
Operating Frequency ◽  
Maximum Efficiency ◽  
Efficiency Ratio ◽  
Pressure Drops ◽  
Test Range ◽  
Micro Nozzle ◽  
Drop Flow ◽  
Fin Design

This study conducts an experimental study concerning the improvement of nozzle/diffuser micropump design subject to enhanced structures. A total of three micropumps, including two enhancement structurs having two-fin or obstacle structure and one conventional micro nozzle/diffuser design. It is found that the pressure drops across the designed micro nozzles/diffusers are increased considerably when the obstacle or fin structure are added. The resultant maximum flow rates are 42.08 mm3/s and 50.15 mm3/s for conventional micro nozzle/diffuser and added two-fin structure in micro nozzle/diffuser operated at a frequency of 350 Hz. It is found that the mass flowrate for two-fin design surpasses that of conventional one when the frequency is below 400 Hz but the trend is reversed with a further increase of frequency. This is because the maximum efficiency ratio improvement for added two-fin is appreciably higher than the other design at a lower operating frequency. In the meantime, despite the efficiency ratio of the obstacle structure also reveals a similar trend as that of two-fin design, its significant pressure drop (flow resistance) had offset its superiority at low operating frequency, thereby leading to a least flowrate throughout the test range.

Research and Development on No-Moving-Part Valves Using Enhancement

2009 ◽  
Author(s):  
Kai-Shing Yang ◽  
Young-Chang Liu ◽  
Chi-Chuan Wang ◽  
Jin-Cherng Shyu
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Research And Development ◽  
Experimental Results ◽  
Efficiency Ratio ◽  
Circular Area ◽  
Interface Friction ◽  
Pressure Drops ◽  
Micro Nozzle ◽  
Maximum Improvement

This study characterizes and analyzes the performances of micro diffusers/nozzles with six types of enhancement structures. The pressure drops across the designed micro nozzles/diffusers are found to be increased considerably when the obstacle and fin structure are added. Further, the micro nozzle/diffuser having added circular area reveals the lowest pressure drop, owing to the hydraulic diameter is increased by circular area and lower interface friction. The maximum improvement of the loss coefficient ratio is about 16% for an added 3-fin structure operated at a Reynolds number around 70. Upon this situation, the static rectification efficiency improves 4.43 times than the conventional nozzle/diffuser. Experimental results indicate the performance peaks at a Reynolds number around 70, and an appreciable decline is encountered when the Reynolds number is reduced. It is due to the efficiency ratio of conventional micro nozzle/diffuser significant increases with the Reynolds number.

scholarly journals DYNAMICS OF TWO-PHASE FLOW ACROSS HORIZONTAL TUBE BUNDLES - A REVIEW

2005 ◽  
Vol 4 (2) ◽  
Author(s):  
G. Ribatskia ◽  
J. R. Thome
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Experimental Studies ◽  
Horizontal Tube ◽  
Prediction Methods ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Drops ◽  
Frictional Pressure Drop ◽  
Tube Bundles

This paper presents a state-of-the-art review of the hydrodynamic aspects of two-phase flow across horizontal tube bundles. The review covers studies related to the evaluation of void fraction, two-phase flow behaviors and pressure drops on the shell side of staggered and in-line tube bundles for upward, downward and side-to-side flows. This study of the literature critically describes the proposed flow pattern maps and semi-empirical correlations for predicting void fraction and frictional pressure drop. These predicting methods are generally based on experimental results for adiabatic air-water flows. A limited number of experimental studies with R-11 and R-113 were also carried out in the past. The review shows noticeable discrepancies among the available prediction methods. Finally, this study suggests that further research focusing on the development of representative databanks and new prediction methods is still necessary.

Estimation of Centrifugal Compressor Stability With Diffuser Loss-Range System

1977 ◽  
Vol 99 (1) ◽  
pp. 76-81
Author(s):  
G. B. Reeves
Keyword(s):  
Centrifugal Compressor ◽  
Flow Characteristic ◽  
Pressure Ratio ◽  
Maximum Flow ◽  
Experimental Results ◽  
Constant Speed ◽  
Maximum Efficiency ◽  
Range Data ◽  
Loss Range ◽  
Estimate Flow

A method has been developed by which centrifugal compressor flow range and the nature of the pressure ratio characteristic approaching surge can be predicted by use of fundamental impeller exit conditions and diffuser entrance geometry in a system where minimum to maximum flow range is determined by the diffuser. Experimental results from compressor tests demonstrate the influence of these basic variables on flow range. Data from pipe type diffuser configurations designed under the assumptions of the loss-range method verify the capability to estimate flow range. Results of tests confirm the use of the method to predict the shape of the pressure ratio/weight flow characteristic and the location of maximum efficiency at constant speed.

scholarly journals Design and Experimental Verification of a Single-Phase Asymmetric Hybrid Multi-level Inverter

2020 ◽  
Vol 3 (2) ◽  
pp. 1-17
Author(s):  
Ahmet Mete VURAL ◽  
Ali Osman ARSLAN ◽  
Mustafa DENİZ
Keyword(s):  
Single Phase ◽  
Pulse Width Modulation ◽  
Experimental Studies ◽  
Harmonic Distortion ◽  
Maximum Efficiency ◽  
Output Level ◽  
Semiconductor Switches ◽  
Harmonic Content ◽  
Asymmetric Hybrid ◽  
Multi Level

In recent years, multi-level inverters have emerged as a feasible power conversion solution for medium and high power applications due to better harmonic performance and ability to operate at high voltage/power when compared to traditional two-level inverters. Since the output level of the multi-level inverters depends on the number of the switching elements, as more levels are required, more switching elements are used. This situation makes the circuit and the control design complex and the losses to upsurge. To overcome these limitations and produce low harmonic content at the output, reduced switch count topologies are popular. In this study, a single-phase asymmetric hybrid multi-level inverter is proposed by combining diode clamped and cascaded H-bridge topologies. The inputs of the proposed inverter are selected as two unequal DC voltage sources. In this regard, fewer switching elements are used to obtain the same number of voltage levels at the output when compared to traditional multi-level inverters. The efficiency and the harmonic performance of the proposed topology is both verified by simulation and experimental studies. The gating signals of the semiconductor switches are produced by phase disposition pulse width modulation with carriers’ frequency of 4 kHz. It is shown by the experiments that a maximum efficiency of 94 % and a total harmonic distortion of 29 % are attained in the case studies.

scholarly journals Theoretical and Experimental Studies of Uneven Dust Suction from a Multi-Cyclone Settling Tank in a Two-Stage Air Filter

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8396
Author(s):  
Tadeusz Dziubak
Keyword(s):  
Internal Structure ◽  
Separation Efficiency ◽  
Settling Tank ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Air Filter ◽  
Pressure Drops ◽  
Dust Trap ◽  
Air Stream ◽  
Before And After

In this paper, the uneven air stream distribution problem of individual cyclones is studied in the multi-cyclones of intake air filters in special vehicles’ engines. This problem increases in multi-cyclones, in which several dozen cyclones have a common dust trap from which the collected dust is continuously removed by ejection suction. The aim of this study is the recognition of the theoretical and experimental possibility of reducing the streams’ unevenness, which should result in an efficiency increase in multi-cyclone separation. The methods that led to obtaining a relative stream uniformity from the suction of individual cyclones was analyzed. The method for creating equal pressure drops between the suction streams in the channels was used to achieve this goal. For this purpose, the internal structure of the multi-cyclone settler was changed. The multi-cyclone settling tank space was divided by vertical partitions into independent segments. The settling tank segment was then divided with horizontal shelves into suction channels of different heights, which were assigned a specific number of individual cyclones. The suction channels’ height was theoretically selected in terms of the equal resistance to air stream flow through the channels. For this purpose, the multi-cyclone dust settler segment model was developed. The theoretically determined suction channel’s height was verified by performing experimental flow tests in four (A, B, C, D) dust settler variants. Suction streams of satisfactory uniformity from the cyclones of the variant D settling tank were obtained at a level of 5%. In the next stage, experimental tests of the segment cyclones were carried out with dust before and after the division into suction channels of variant D for the settling tank. A significant increase was achieved from 93.73% to 96.08% in the cyclones’ separation efficiency, which were located as far away from the suction stub as possible and led to a reduction in the non-uniformity of cyclone efficiency in the segment. It follows that the multi-cyclone dust settling segment’s internal structure change gave the expected results.

scholarly journals Optimal Energy Characteristics and Working Parametries of RF Switch Mode Power Amplifier Based on Controllable Current Fed Resonant Inverter

2020 ◽  
Vol 6 (1) ◽  
pp. 43-49
Author(s):  
A. Ganbayev ◽  
V. Filin
Keyword(s):  
Control Method ◽  
Operating Frequency ◽  
Maximum Efficiency ◽  
Power Losses ◽  
Rf Switch ◽  
Energy Characteristics ◽  
Resonant Inverter ◽  
Switching Losses ◽  
Switch Mode ◽  
Optimal Excitation

This article represents us the method for power losses minimizing in transistors of a radio frequency key gen-erator (power amplifying) based on the control method application with overlapping pulses. We see fully formed requirements for the optimal excitation mode, providing maximum efficiency and maximum operating frequency, taking into account the finite times of switching on and off the generator GaN transistors. The article shows the obtained analytical equations for calculating power in a load, loss of efficiency, as well as equations for estimating the maximum operating frequency of the generator depending on the permissible level of losses. The article presents graphics of curves that determine the maximum operating frequency of an RF generator for permissible switching losses on various types of GaN transistors.

scholarly journals Heat Transfer Enhancement by Perforated and Louvred Fin Heat Exchangers

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 400
Author(s):  
Miftah Altwieb ◽  
Rakesh Mishra ◽  
Aliyu M. Aliyu ◽  
Krzysztof J. Kubiak
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
Flow Rates ◽  
Pressure Drops ◽  
Fin Design

Multi-tube multi-fin heat exchangers are extensively used in various industries. In the current work, detailed experimental investigations were carried out to establish the flow/heat transfer characteristics in three distinct heat exchanger geometries. A novel perforated plain fin design was developed, and its performance was evaluated against standard plain and louvred fins designs. Experimental setups were designed, and the tests were carefully carried out which enabled quantification of the heat transfer and pressure drop characteristics. In the experiments the average velocity of air was varied in the range of 0.7 m/s to 4 m/s corresponding to Reynolds numbers of 600 to 2650. The water side flow rates in the tubes were kept at 0.12, 0.18, 0.24, 0.3, and 0.36 m3/h corresponding to Reynolds numbers between 6000 and 30,000. It was found that the louvred fins produced the highest heat transfer rate due to the availability of higher surface area, but it also produced the highest pressure drops. Conversely, while the new perforated design produced a slightly higher pressure drop than the plain fin design, it gave a higher value of heat transfer rate than the plain fin especially at the lower liquid flow rates. Specifically, the louvred fin gave consistently high pressure drops, up to 3 to 4 times more than the plain and perforated models at 4 m/s air flow, however, the heat transfer enhancement was only about 11% and 13% over the perforated and plain fin models, respectively. The mean heat transfer rate and pressure drops were used to calculate the Colburn and Fanning friction factors. Two novel semiempirical relationships were derived for the heat exchanger’s Fanning and Colburn factors as functions of the non-dimensional fin surface area and the Reynolds number. It was demonstrated that the Colburn and Fanning factors were predicted by the new correlations to within ±15% of the experiments.

scholarly journals Effects of Pressure Drops on the Performance Characteristics of Air Standard Otto Cycle

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Mahmoud Huleihil
Keyword(s):  
Pressure Drop ◽  
Constant Pressure ◽  
Performance Characteristics ◽  
Maximum Efficiency ◽  
Maximum Pressure ◽  
Otto Cycle ◽  
Pressure Drops ◽  
Internal Irreversibility ◽  
Expansion Model ◽  
Engine Size

The effects of pressure drops on the performance characteristics of the air standard Otto cycle are reported. The pressure drops are assumed as constant values independent of the engine size. It has been shown that the pressure drops to about 60% of the maximum pressure in the ideal cycle (Curto-Risso et al., 2008). Three different models are studied: constant pressure model, reversible adiabatic expansion model and polytropic expansion model. The findings of this study show that, at this level of pressure drop, the maximum efficiency of the Otto cycle is reduced by 15% approximately based on the constant pressure model. The combined effect of pressure drop with other modes of irreversibility, for example, internal irreversibility and heat leaks, could reduce the maximum efficiency into very low values (approximately 30%). The reversible adiabatic model predicts reduction of 13% in efficiency at 40% pressure drop levels but at the price of zero power production. On the other hand, the polytropic expansion model predicts 40% reduction in efficiency for the same level of pressure drop (40%). All three models show that the power output is very sensitive to pressure drop.

Pressure Drops and Model Modification for Two-Phase Flow in Porous Beds With Coarse Particles

2017 ◽  
Author(s):  
Xumao Zou ◽  
Liangxing Li ◽  
Liubo Kong ◽  
Huasheng Wang
Keyword(s):  
Two Phase Flow ◽  
Fluid Velocity ◽  
Experimental Studies ◽  
Test Facility ◽  
Phase Flow ◽  
Coarse Particles ◽  
Two Phase ◽  
Modified Model ◽  
Pressure Drops ◽  
Interfacial Drag

Motivated by reducing the uncertainties in coolability analysis of a debris bed, this paper proposed a modified model for the pressure drops of two phase flow through packed beds with coarse particles based on the experimental studies. The experiments are carried out on the test facility of DEBECO-LT (DEbris BEd COolability-Low Temperature), which was designed to investigate single / two-phase flow in porous beds. The coarse particles are packed in the cylindrical test section with the inner diameter of 120 mm and the height of 600 mm. Through single-phase flow tests in homogeneous beds, the reliability of the whole experimental system is ensured. Then two-phase flow tests are performed to investigate the flow characteristics, to provide basic data for verifying and modifying the existing models. The results show that, the interfacial drag in beds with coarse particles will result in a decreasing tendency in the pressure drop curves along with the fluid velocity, and the the effect of interfacial drag should be considered in the debris coolability analysis models for beds with coarse particles. Compared with the existing models, the new model shows relatively satisfactory forecasting ability, and the predictions have favorable agreement with existing experimental data under various conditions. This modified model could be applied to calculate the pressure drops of two-phase flow in coarse-particle beds.

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