Dissertations / Theses on the topic 'Reciprocating pumps'

Thesis (Ph.D.)--University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 28, 2007). Vita. Includes bibliographical references.

An investigation has been carried out to determine the factors controlling the wear characteristics of disc poppet valves in reciprocating slurry pumps used in the transportation of quartzite slurries. A laboratory test rig has been designed and built which closely simulates the operating conditions experienced by slurry pump valves. Experiments have been conducted to determine the effect of the design parameters, namely - slurry constitution, valve closure velocity and valve angle, on the wear resistance of a low alloy steel, as a function of its mechanical properties. It has been shown that the wear of the valves is a sensitive function of the operating parameters. Significant improvements in the life of the valves can be achieved through increasing material hardness, reducing valve closure velocity, slurry density and valve angle. A detailed study has been made of the mechanisms contributing to valve wear. It has been established that both percussive impact and three body abrasion wear mechanisms predominate. The influence of each mechanism has been shown to be a function of the slurry constitution and the material hardness.

[ES] Esta tesis doctoral presenta un estudio de compresores scroll con inyección de vapor (SCVI) para bombas de calor que operan en climas fríos o para aplicaciones de calentamiento de agua a alta temperatura. Para ello, se comparó experimentalmente un SCVI con un compresor de dos etapas de pistones (TSRC) trabajando con R-407C en condiciones extremas. La comparación se realizó en términos de eficiencias del compresor, capacidad, COP y rendimientos estacionales tanto para el modo calefacción como para el modo refrigeración. Los resultados proporcionan una idea general sobre el rango de aplicación de los compresores estudiados y sobre las diferencias en los rendimientos de los compresores. Sin embargo, se identificaron varias limitaciones en la caracterización de los compresores y en el análisis del ciclo. Esto motivó a profundizar en el estudio del ciclo de compresión de dos etapas y sus componentes. El siguiente paso fue realizar un análisis teórico de los ciclos de compresión de dos etapas para aplicaciones de calefacción, en donde se identificó a la presión intermedia y a la relación de inyección como los parámetros del sistema más influyentes sobre el COP. La presión intermedia se optimizó para dos configuraciones de inyección (tanque de separación y economizador) utilizando varios refrigerantes. Basándose en los resultados de la optimización, se propuso una correlación que permite obtener la presión intermedia óptima del ciclo, considerando la influencia del subenfriamiento a la salida del condensador. Además, se analizó la influencia del diseño de los componentes del sistema sobre el COP del ciclo. Posteriormente, el estudio se profundizó a nivel de componentes. El factor más crítico en el sistema es el rendimiento del compresor. Por lo tanto, el siguiente paso fue evaluar la influencia de varios sistemas de compresión con inyección de vapor sobre el COP. Se tomaron en cuenta tres tecnologías de compresores, un SCVI, un TSRC y un compresor scroll de dos etapas (TSSC). Estas tecnologías de compresores fueron caracterizadas y modeladas para estudiar su rendimiento. Para ello, se propuso una nueva metodología para caracterizar compresores scroll con inyección de vapor. Esta metodología permite evaluar el rendimiento del compresor independientemente del mecanismo de inyección que se utiliza en el ciclo. Se identificó una correlación lineal entre la relación de inyección de refrigerante y la relación de compresión intermedia. Esta correlación se utiliza para determinar el flujo másico de inyección en función de la presión intermedia. Posteriormente, se propuso un modelo semi-empírico de compresores scroll y una metodología para extender dicho modelo para compresores scroll con inyección de vapor. Los modelos fueron ajustados y validados usando datos experimentales de cuatro compresores scroll trabajando con R-290 y un SCVI trabajando con R-407C. Finalmente, se comparó un SCVI con dos compresores de dos etapas, un TSSC y un TSRC, trabajando en condiciones extremas. Se optimizó la relación de volúmenes de los compresores de dos etapas. Los resultados muestran que, en las condiciones nominales de funcionamiento (Te=-15 °C, Tc=50 °C), la relación de volúmenes óptima del TSSC es 0.58, y del TSRC es 0.57. El TSSC consigue un COP 6% mayor que el SCVI y un COP 11.7% mayor que el TSRC. Bajo un amplio rango de condiciones de operación, el SCVI presenta una mejor eficiencia y COP para relaciones de presión inferiores a 5. Para relaciones de presión más altas, el TSSC presenta mejor rendimiento y consigue una temperatura de descarga más baja. Se concluye que el SCVI es una solución fácil de implementar, desde el punto de vista del mecanizado, y que permite extender el mapa de trabajo de los compresores de una etapa. Sin embargo, los resultados muestran que la compresión en dos etapas consigue mejorar en mayor medida el COP del ciclo y la capacidad, con una mayor redu
[CA] Aquesta tesi doctoral presenta un estudi de compressors scroll amb injecció de vapor (SCVI) per a bombes de calor que operen en climes freds o per a aplicacions d'escalfament d'aigua a alta temperatura. Per a això, es va comparar experimentalment un SCVI amb un compressor de dues etapes de pistons (TSRC) treballant amb R-407C en condicions extremes. La comparació es va realitzar en termes d'eficiències del compressor, capacitat, COP i rendiments estacionals tant per al mode calefacció com per al mode refrigeració. Els resultats proporcionen una idea general sobre el rang d'aplicació dels compressors estudiats i sobre les diferències en els rendiments dels compressors. No obstant això, es van identificar diverses limitacions en la caracterització dels compressors i en l'anàlisi del cicle. Això va motivar a aprofundir en l'estudi del cicle de compressió de dues etapes i els seus components. El següent pas va ser realitzar una anàlisi teòrica dels cicles de compressió de dues etapes per a aplicacions de calefacció, on es va identificar la pressió intermèdia i la relació d'injecció com els paràmetres del sistema més influents sobre el COP. La pressió intermèdia es va optimitzar per a dues configuracions d'injecció (tanc de separació i economitzador) utilitzant diversos refrigerants. Basant-se en els resultats de l'optimització, es va proposar una correlació que permet obtindre la pressió intermèdia òptima del cicle, considerant la influència del subrefredament a l'eixida del condensador. A més, es va analitzar la influència del disseny dels components del sistema sobre el COP del cicle. Posteriorment, l'estudi es va aprofundir a nivell de components. El factor més crític en el sistema és el rendiment del compressor. Per tant, el següent pas va ser avaluar la influència de diversos sistemes de compressió amb injecció de vapor sobre el COP. Es van prendre en compte tres tecnologies de compressors, un SCVI, un TSRC i un compressor scroll de dues etapes (TSSC). Aquestes tecnologies de compressors van ser caracteritzades i modelades per a estudiar el seu rendiment. Per a això, es va proposar una nova metodologia per a caracteritzar compressors scroll amb injecció de vapor. Aquesta metodologia permet avaluar el rendiment del compressor independentment del mecanisme d'injecció que s'utilitza en el cicle. Es va identificar una correlació lineal entre la relació d'injecció de refrigerant i la relació de compressió intermèdia. Aquesta correlació s'utilitza per a determinar el flux màssic d'injecció en funció de la pressió intermèdia. Posteriorment, es va proposar un model semi-empíric de compressors scroll i una metodologia per a estendre aquest model per a compressors scroll amb injecció de vapor. Els models van ser ajustats i validats utilitzant dades experimentals de quatre compressors scroll treballant amb R-290 i un SCVI treballant amb R-407C. Finalment, es va comparar un SCVI amb dos compressors de dues etapes, un TSSC i un TSRC, treballant en condicions extremes. Es va optimitzar la relació de volums dels compressors de dues etapes. Els resultats mostren que, en les condicions nominals de funcionament (Te=-15 °C, Tc=50 °C), la relació de volums òptima del TSSC és 0.58, i del TSRC és 0.57. El TSSC aconsegueix un COP 6% major que el SCVI i un COP 11.7% major que el TSRC. Sota un ampli rang de condicions d'operació, el SCVI presenta una millor eficiència i COP per a relacions de pressió inferiors a 5. Per a relacions de pressió més altes, el TSSC presenta millor rendiment i aconsegueix una temperatura de descàrrega més baixa. Es conclou que el SCVI és una solució fàcil d'implementar, des del punt de vista del mecanitzat, i que permet estendre el mapa de treball dels compressors d'una etapa. No obstant això, els resultats mostren que la compressió en dues etapes aconsegueix millorar en major mesura el COP del cicle i la capacitat, amb una major reducció de la
[EN] This Ph.D. thesis presents a study of scroll compressors with vapor-injection (SCVI) for heat pumps operating in cold climates or in high-temperature water heating applications. To do so, firstly, an SCVI was experimentally compared with a two-stage reciprocating compressor (TSRC) working with R-407C under extreme conditions. The comparison was made in terms of compressor efficiencies, capacity, COP, and seasonal COP, both for heating and cooling modes. The results give a general idea about the application range of the studied compressors and the differences in the compressors' performance. Nevertheless, several restrictions in the compressors' characterization and the cycle analysis were identified. This motivated us to deepen in the study of the two-stage compression cycle and its components. The next step was performing a theoretical analysis of two-stage compression cycles for heating applications, where the intermediate pressure and the injection ratio were identified as the most influential system parameters on the COP. The intermediate pressure was optimized for two vapor-injection configurations (flash tank and economizer) using several refrigerants. Based on the optimization results, a correlation was proposed that allows obtaining the optimal intermediate pressure of the cycle, considering the influence of the subcooling at the condenser outlet. In addition, a theoretical analysis of the influence of the design of the system components on the COP of the cycle was performed. Once the thermodynamic analysis of the two-stage cycle was carried out, the study was deepened at the component level. The most critical factor in the system is the compressor performance. Hence, the next step was evaluating the influence of several compression systems with vapor-injection on the COP. Three compressor technologies were taken into account, an SCVI, a TSRC and a two-stage scroll compressor (TSSC). These compressor technologies were characterized and modeled in order to study their performance. To do so, a new methodology to characterize SCVI was proposed. This methodology allows evaluating the compressor performance independently of the injection mechanism used in the cycle. A linear correlation was identified between the refrigerant injection ratio and the intermediate compression ratio. This correlation is used to determine the injection mass flow as a function of the intermediate pressure. Then, a semi-empirical model of scroll compressors and a methodology to extend the model for scroll compressors with vapor-injection was proposed. The models were adjusted and validated using experimental data from four scroll compressors working with R-290 and an SCVI compressor working with R-407C. Finally, an SCVI was compared with two two-stage compressors, a TSSC, and a TSRC, working in extreme conditions. The displacement ratio of the two-stage compressors was optimized. Results show that, at the nominal operating conditions (Te=-15 °C, Tc=50 °C), the optimal displacement ratio of the TSSC is 0.58, and of the TSRC is 0.57. The TSSC achieves 6% larger COP than the SCVI and 11.7% larger COP than the TSRC. Under a wide range of operating conditions, the SCVI presents a better efficiency and COP for pressure ratios below 5. For higher-pressure ratios, the TSSC presents better performance and achieves lower discharge temperature. It is concluded that the SCVI is an easy solution to implement from the point of view of machining, which allows extending the working map of the single-stage compressors. However, the results show that the two-stage compression technology gets further improve the COP of the cycle and the capacity, with a greater reduction of the discharge temperature operating under extreme conditions.
I thank the financial support provided by the Secretaría de Educación Superior, Ciencia, Tecnología e Innovación (SENESCYT) of Ecuador, through the international scholarship program for postgraduate studies “Convocatoria Abierta 2013 Segunda Fase, Grant No 2015-AR37665”.
Tello Oquendo, FM. (2019). Study of scroll compressors with vapor-injection for heat pumps operating in cold climates or in high-temperature water heating applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/120473
TESIS

A miniature reciprocating expander is being developed as part of a larger program to develop a heat actuated heat pump for portable applications. By utilizing the higher energy density of liquid hydrocarbon fuels relative to batteries, a heat actuated heat pump would be able to provide cooling for much longer than motor driven units of equal weight. A prototype expander has been constructed and demonstrated to produce up to 22 W of shaft power at 2500 rpm using 60 psig, room temperature nitrogen as the input. Assuming adiabatic conditions, the expander appears to operate at up to 80% isentropic efficiency. However, when heat inflow to the expander is accounted for, the resulting polytropic efficiency is about 10% lower. In addition to experimental results, models of expander performance with different loss mechanisms are presented. These mechanisms include over- and under-expansion, in-cylinder heat transfer, clearance volume, friction, and valve pressure drop.
Graduation date: 2005

碩士
國立屏東科技大學
材料工程所
101
The purpose of this study is to provide a metal-based surface micromachining method to achieve a valve type of electromagnetic pump. The method includes photo developing, etching, electroplating, laser machining, tapping, etc. PMMA was the construction material of the actuator, and copper clad laminate was utilized to fabricate micro coil. When an AC power applied to the micro coil, the magnetic field changes generated diaphragm displacement due to the AC frequency. The displacement of diaphragm was caused by attraction and repulsion force between the NdFeB permanent magnet and the micro coil. In this study, the dimensions of the micro coils are 150 μm wide, 150 μm spacing and 30 turns. Measurement was executed under the influence of different numbers of series coils to produce magnetic flux. The experimental results indicate a maximum magnetic flux of 4.36 mTesla has been measured when 0.4 amperes of current is applied to the four-layer coils that are electrically connected in series. As the permanent magnets distance is 1.54 mm form the center of the coil, a magnetic force of 4,625.6 Dynes can be produced. As an AC voltage of 3 V is applied, a diaphragm displacement of 108.2 μm is induced. A maximum flow rate of 220.1 μl/s and a head pressure of 240 Pa have been measured when 3 V and 15 Hz of AC power is applied.

碩士
逢甲大學
航太與系統工程所
95
The liquid cooling has many advantages even though its large pump system is not suitable for either the server or the notebook computer nowadays. Hence, the pump should be made as small as possible. However, the micro-piezoelectric pump can not be commercialized due to the cost and the performance limitations. Therefore, a micro-reciprocating pump developed by Loopek Technology Co., LTD. is studied. The commercial software, Fluent, is used as a tool for numerical analysis. The effectiveness, the flow field, the temperature field, and the pressure field of this micro-pump are investigated. An optimal micro-reciprocating pump can be found by a series of parametric study. Finally, the performance curve is verified qualitatively by running an experimental test.

碩士
北台灣科學技術學院
機電整合研究所
97
The study introduces mainly a controller which is dedicated for a type of electromagnetic driving pump. The pump is previously invented in the laboratory. The controller with corresponding driver can generate various periodic power sources for driving the type of pump. In practice, the controller is designed to produce a widely tunable power range with different waveforms which are able to match the request of general applications. Three tunable entities are therefore considered in the design principle: the waveform, frequency, and duty-cycle. Three kinds of waveform, including square, triangular, and sinusoidal waves, with a proper range of frequency which can be continuously adjusted are included in the design. In order to drive the pump more efficiently, a series of adjustable imbalanced duty-cycle are also devised in the study. The presentation of the paper is divided into four parts: the first is to introduce the invention of the pump, the second is the optimization of the pump by ANSYS/Emag simulation, the third is to introduce the design of the controller, and the final presents the performance test with the designed controller. Using the tunable controller, the hydraulic characteristics of the pump can be investigated under different periodic power sources. Also, by the experimental investigation, a good control strategy can be concluded and suggested. The experiments show the pump’s function behavior can be either changed due to the changes of the waveform, the frequency, or the duty-cycle significantly. Therefore, the corresponding best control strategy of the specified pump is eventually reported in the paper. Through the experiments, a rational selection model of a coupled driver for an arbitrarily chosen pump can be extended. With the rational model, the pump with the coupled driver can efficiently cooperated under satisfactorily selected conditions.

碩士
逢甲大學
航太與系統工程所
96
The object of this study is to design a novel, small, and high efficient pump. This reciprocating and electromagnetic pump is constructed of coils and magnet that provides thrust for the pump by the Lorentz force. The experimental data had been compared with those obtained by Lu [25]. The operation of the coils is controlled by the square-wave pulse. Different duty cycle, frequency, voltage, and electric current of the coils results in different square-ware pulse. The experimental parameters include the turns of coil, diameter of copper wire, length of magnet, length of magnet chamber, and magnet rings of the pump. Moreover, the performance of the pump was investigated by the flow rate and the pressure head of the pump. The experimental results show that the best performance can be obtained when the length of magnet is 12.5mm. In addition, the operation of the magnet has optimal performance with optimal frequency and duty cycle. Even though increasing the voltage and current of the coils will result in increasing the initial velocity and frequency of the magnet and the flow rate of the pump, the performance per unit energy of the pump will decrease. The magnet rings of pump can increase the efficiency of the pump and retard the impact between the magnet and the chamber. The outlet pressure of a shorter chamber is higher than that of a longer chamber. However, due to the impact involved in the operation between the magnet and the chamber, a pump with a shorter chamber does not work very well when the operating frequency is greater than 60 Hz. In a contrary, a pump having a longer chamber performs better with a higher frequency of the magnet, although the outlet pressure of the pump is lower than that of a pump having a shorter chamber.

碩士
國立臺灣海洋大學
機械與機電工程學系
103
Left ventricular assist device (LVAD) is widely discussed with its use in medical area. It not only successfully helps to extend the waiting time of heart transplant but also effectively improves the survival rate in the papers. LVAD with the pulsatile pump can generate pulsatile flow which is similar to the human circulatory system and it is better for the patients. In this research work, the driving signals for a reciprocating electromagnetic driving 24-coils pump has been designed and developed. An induced magnetic field interacted with the magnet inside the piston, and repulsive or attractive force was generated to drive the piston when the current was applied to the coils. Its delay time and the signal sequence can be programmed and the piston moved reciprocating under the system program control. By using the software Maxwell, the magnetic flux density and the driving force distribution can be simulated under different conditions, such as the current applied to single or multi-section coils and different number of magnets inside the piston. Different driving modes have been designed and proposed according to the simulation results. The Hall Effect sensors were put outside the pump to sense the piston position in real time while it was working. Some experiments have been done to verify the piston movement under different designed driving modes. The sensing signals showed the piston moving smoothly and controllable in the air under the different driving modes. The piston hasn’t moved well while the pump was connected to simple fluidic channels fulfilled with water. Furthermore, the pump was test in the mock circulation loop in Keelung Chang Gung Memorial Hospital and the better driving modes were chosen according to the experiment results previous. The induced attractive force distribution covered the whole piston; hence its position can be precisely limited and controlled. The reciprocating rate was adjusted to 1: 2, and the piston still can be driven smoothly and the water flow reached 4.0 liter per minute and the maximum number of reciprocating cycles was able to reach about 35 cycles. This shows the driving signals and driving mode design in this research work is feasible.

碩士
國立臺灣海洋大學
系統工程暨造船學系
106
According to the World Health Organization (WHO) report, cardiovascular disease is one of the top 10 causes of deaths today, in which heart disease is the first death rate, so how effective treatment of heart disease has become an important issue. The development of left ventricular assist device (LVAD) plays a key role in clinical treatment and improves the survival rate of patients with severe heart disease. And compared to the widely used continuous left ventricular aids, pulsating can pulsating the way to promote blood, this method is closer to the heart of the movement, help to restore cardiac function. However, pulsating pumps in the process of promoting the blood to consume higher power, but also make the pump heat, causing inconvenience. This study will refer to the pulse width modulation (Pulse Width Modulation, PWM) method, for the team developed by the 24-coil magnetic drive pump to observe and find low-power drive. The pump will interact with the magnetic field formed by the energization of the coil and interact with the permanent magnets placed in the pump internal piston, thereby driving the piston to reciprocate and use the Hall sensor to monitor the piston position in real time, The drive signal remains the same. Experimental results show that, according to the design of the drive method, can reduce the power loss of 40%, to achieve the purpose of energy conservation.

碩士
國立臺灣海洋大學
系統工程暨造船學系
102
The relationship between the magnetic force driving reciprocating pump control and the circular pipe flow rate and pressure was studied in this research work. The eight-set coils magnetic driving reciprocal pump was adopted and there was a permanent magnet piston inside. The repulsive or attractive force would apply to the piston when the current was applied to the coils and magnetic field was produced. The forward direction or reverse current was controlled by a single-chip which was wired to a relay circuit. The on or off status of the relays was controlled by the signal sequence sent by the single-chip and can decide the current direction. Varying the current/voltage can change the magnitude of the repulsive or attractive force applied to the piston. With different reciprocal times per minutes and values of the current/voltage, the flow rate and pressure difference of the circular pipe flow was obtained. The flow and pressure meters were also set in the pipe flow system. The flow rate was increased from 0.845 to 2.316 L/min if the reciprocal cycles was risen from 30 to 80 per minute under 22 volts driving voltage. The flow rate was increased to 3.185 times. The flow rate growing was only 1.165 times when the voltage was raised from 13 V to 25 V under condition of the reciprocal cycles was 30 per minute. This showed that the main factor to affect the flow rate was the reciprocal cycles per minute. In addition, the increase of the pressure difference of the pipe can achieve 4.215 mmHg when the voltage was from 18 V to 24 V in the condition of 30 reciprocal cycles per minute. According to the experiments in this study, the driving and control method of the eight sets of coils magnetic driving reciprocal pump was successful. The pumping ability of this pump was almost met the requirement of LVAD: 2 L/min. The results can be further provided to the designer to modify the winding process of the coils, and utilizing the fluid similar to blood while testing can be helpful to improve the pump. It is believed the pump can be integrated to the LVAD in the near future.

碩士
國立臺灣海洋大學
機械與機電工程學系
100
The average human life has been extended as the medical progress, but the function of the organs will be aging as the human getting older. The most serious heart disease which is caused by the aging is heart failure. The heart transplantation remains the most successful treatment in the medical treatment options for heart failure patients. However, the heart donations are few and the implantation of the left ventricular assist device (LVAD) as a bridge to transplant (BTT) or as a permanent support is a good alternative. This research is to develop the control and the current amplifier circuit for the four coil magnetic driven reciprocating pump which is planned to be part of LVAD. The driving method of the pump was based on electromagnetic effect. The current applied to the coils on the pump would produce a magnetic field to drive the permanent magnetic piston inside the pump. The required current was about 0.1A ~3A so the current amplifier design was a key point. The first proposed circuit here was the corporation of the transistors and the relays, and a microcontroller AT89S51 has been adopted to send the signals to the circuit to control the relays to switch the positive and negative current directions. This would make the currents continuously applied to every coils and the every produced magnetic field would affect the movement of the piston. Another problem was the heat produced by the current-carrying coils; therefore, no current state (called the 0 state here) was introduced and this obviously improved the performance of the pump. Using relays as the switches to control the current direction in the coils required two relays for each coil. In this study, total 8 relays were needed for a magnetic driven reciprocating pump because there were four coils of it. This made to reduce the volume of the entire circuit become a difficulty. In addition, the switching of the relay is a mechanical movement and the response speed would be limited. The operational amplifier TA7272P design of the current amplifier circuit was further proposed to replace the circuit which composed of relays and transistors. This circuit was not only the volume was substantially reduced; but the switching speed was also improved. Finally, the four coil magnetic driven reciprocating pump was setup into a closed loop flow system. The function of the current amplifier circuit with the single-chip signal control program proposed in this study has been confirmed. The expected pump piston reciprocating motion was observed obviously and it could effectively drive the flow of water in the closed loop flow system. The pump has the potential to be used in a left ventricular assist device if the design circuit, the pump structure, the piston structure requirements, software and hardware are further modified and integrated well in the future.

碩士
國立臺灣海洋大學
系統工程暨造船學系
103
Abstract The best treatment is the heart implantation for the severe heart failure patients presently; however, this operation cannot be carried until there is a proper donated organ for the patient. The LVAD implantation is one choice to have the extension life time waiting for the proper organ and has been widely used as the treatment in Europe, America, and Japan. The use of LVAD can effectively improve patient survival rates and increase the life time. This study is trying to find the relationship between the coil sets arrangement and the piston moving cycles for a magnetic coil drive reciprocating pump coil. The control parameters: duty cycle, voltage/current, distance between the coils, and the width of the coils were varied and to obtain the best piston movement in the air. The electric magnetic field of single coil and different distances coils was simulated by the software ANSYS Maxwell under different currents. The magnetic strength reduced to half when the distance was larger than 4 mm. For experiments, 10 different pump outer cylindrical shells were made with different coils distances: 1 mm, 2 mm, 4 mm, 6 mm, and 8 mm and different width: 8 mm and 10 mm. The field-programmable gate array was adopted as the signal control system and the current amplify circuits made by IC TA7257P to drive the piston movement in the air. As the experiment results, the highest reciprocating frequency was 120 times/min for the pump wound with 200-turn and 10 mm width coils, and the distance between coils was above 4 mm. On the other hand, the piston reciprocating movements can achieve 300 times per minute when the coil distances were 1 mm and 2 mm. Besides, with 8 mm-coil-width, the piston reciprocating movements was 280 times/min even the coil distance was 4 mm It showed that the current density was high enough for the piston moving smoothly while the pump coils was 8 mm and the movement control was easier. Keywords: left ventricular assist device, linear pumps, magnetic drive coil pump, current density.