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Journal of Magnetism and Magnetic Materials 320 (2008) 1406–1411

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Study on power generation using electro-conductive polymer and itsmixture with magnetic fluid

Hiroshi Yamaguchia, Xin-Rong Zhangb,a,�, Shidei Higashia, Mingjun Lia

aDepartment of Mechanical Engineering, Doshisha University, Kyo-Tanabeshi, Kyoto 610-0321, JapanbDepartment of Energy and Resources Engineering, College of Engineering, Peking University, Beijing, 100871, PR China

Received 6 July 2007

Available online 23 December 2007

Abstract

A new power generation system using electro-conductive polymer and its mixture with magnetic fluid is introduced. The system using

non-poison electro-conductive polymer and its mixture with magnetic fluid and operating at room temperature is proposed in the present

paper. The system could be used as a micro-distributed energy supply system for domestic use in the future. An experimental set-up is

designed and established to investigate the performance of the power generation with an aid of a theoretical analysis of the power

generation. It is found that the theoretical results are in good agreement with the measured data. Based on the obtained results, the

electric output increases with Reynolds number, size of the test channel, magnetic strength and electric conductivity. It is understood that

in order to obtain a practical power generation, priority should be put on increasing fluid flow velocity and magnetic field strength.

r 2007 Elsevier B.V. All rights reserved.

PACS: 52.75.Fk; 84.60.Lw; 47.65.Cb; 45.20.Dh; 47.50.�d

Keywords: Electro-conductive polymer; Magnetic fluid; MHD power generation; MHD device; Non-Newtonian fluid flow

1. Introduction

MHD power generation using a liquid metal, plasma gasor solid rocket fuel has been researched for technical usesince 1950s by many researchers. When plasma gas is usedas working fluid, the operation of MHD power generationis in high-temperature conditions. High melting point isconsidered as a problem if liquid metal is used as workingfluid. MHD power generation using solid rocket fuel isonly achieved in 3000–4000 1C in channel for a short time[1,2]. For the above reason, MHD power generation is notsuitable as a distributed energy supply system for thedomestic use in room temperature.

In this paper, a micro-distributed energy supply system isproposed, and it can utilize waste heat from microchip, etc.and provide electric energy to user. A schematic diagram of

- see front matter r 2007 Elsevier B.V. All rights reserved.

/j.jmmm.2007.12.014

onding author at: Department of Energy and Resources

, College of Engineering, Peking University, Beijing, PR

: +861082529066; fax: +861062757421.

ddress: xrzhang@coe.pku.edu.cn (X.-R. Zhang).

the proposed system can be seen in Fig. 1. The proposedsystem can circulate working fluid (magnetic fluid, etc.) byitself and no pump is needed, and this system is based onthe previous work. The details can be seen in Refs. [3,4], inwhich the feasibility of fluid circulating itself, absorbing thewaste heat and releasing heat was confirmed by experi-ments. The proposed system is in very small scale and aimsto supply electric energy to user below 80 1C. In the presentwork, an electro-conductive polymer solution and itsmixture with magnetic fluid are considered as workingfluids in MHD power generation system. As far as theauthors know, MHD power generation using electro-conductive polymer or its mixture with magnetic fluid isnot found in the open literature. The system using electro-conductive polymer or its mixture fluid with magnetic fluidis expected to have a potential as a micro-distributedelectric supply system, because magnetism of the workingfluid and its electric conductivity can be achieved simulta-neously for the mixture fluid. An experimental study iscarried out to investigate basic performance of the powergeneration for the system. Furthermore, a theoretical

ARTICLE IN PRESSH. Yamaguchi et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 1406–1411 1407

method is developed to study impacting factors of thesystem and methods how to improve the electric output.

2. Experiment

2.1. Experimental set-up

In order to investigate the performance of the proposedMHD power generation system, an experimental set-up is

Microchannel

Microchip Heat absorption

Magnet

Heat release

Electric energysupply

Module

100 µm

Fig. 1. Micro-distributed energy supply system.

Pump Flow mete

Incubator Cooler

Circulator Test chann

Permanent magnet Thermo co

Resistance Electromet

1

4

7

10

13 14

11

8

5

2

46 5

7

3

2

1

11

10

9

8

Fig. 2. Experimental set-up for studying performance of the MHD power g

magnetic fluid.

designed, constructed and tested. The experimental set-upis schematically shown in Fig. 2. The established experi-ment system mainly consists of pump, flow meter,temperature control section, power generation sectionand measurement section of power generation output. Itshould be mentioned here that as the first step of studyingthe feasibility of using the proposed fluid as working fluidin micro-distributed energy supply system, the experimen-tal set-up is not established on a very small size base.In this experiment system, test fluid is pumped by the

pump and the flow rate can be controlled by adjustingrotation speed of the pump. The mass flow rate is measuredby a Coriolis mass flow rate (provided by Oval Corpora-tion), which has an accuracy of 70.2%.In the experimental test, the test fluid temperature

can be adjusted and controlled by the temperaturecontrol section. The temperature control section comprisedtemperature control unit, incubator (provided byADVANTEC), cooler (provided by Thomas Kagaku Co.,Ltd.), tank and circulator. Based on the test fluidtemperature in the temperature control unit, incubatorand cooler adjust water temperature in the tank andthe circulator pumps water into the temperature controlunit to control the temperature of the test fluid. Thetemperature control section can achieve the adjustment

r Temperature control unit

Tank

el Electrode

uples Data logger

er Computer

3

6

9

12

15

14 12

13

15

eneration system using electro-conductive polymer and its mixture with

ARTICLE IN PRESSH. Yamaguchi et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 1406–14111408

of the test fluid temperature within an accuracy of70.01 1C.

As shown in Fig. 2, the power generation section consistsof test channel, electrode and permanent magnet (providedby Magna Co., Ltd, Nd–Fe–B Magnet). The powergeneration section is schematically shown in Fig. 3. Thetest channel is made of acrylic, which is a fluid channel witha rectangular cross section of 10� 10mm2. The electrode isset-up on the inner wall of the test channel, with a width of10mm (y-direction) and a length of 200mm (x-direction).A couple of permanent magnets are installed outside thetest channel toward the z-direction, which can be seen inFig. 3. In addition, in the positions of 10mm from theinlet and outlet of the test channel, 2 thermal couples areused to measure the test fluid temperature, with anaccuracy of 70.1 1C.

The measurement section of power generation output iscomprised data logger, resistance, electrometer anddata processing computer. The used resistance is 5 kOand electrometer (provided by KEITHLEY) has ahigh accuracy of 70.004%. The electric current andresistance of the power generation section are measuredby the electrometer. In addition, a real time dataacquisition is used in the experiment. The outputsof the experimental data can be automatically recordedand transported through the data logger and thecomputer as functions of time, with a sampling timeperiod of 1.0 s.

Permanent magnet Magnet holder

Test channel Electrode

z

x

1090

200

270

1

2

3

4

1

3

2

4

x

y

Fig. 3. Schematic diagram of power generation section in the experi-

mental set-up.

2.2. Test fluid

The MHD power generation system using electro-conductive polymer or its mixing fluid with magnetic fluidis expected to be operated in the room temperature and haslow cost. In the present study, MSGW11 provided byFerrotec, USA, is used, which is water-based magneticfluid. For electro-conductive polymer, polymer anilinesulfonic acid is utilized, which is very stable in the airand has a low cost. In the experimental test, theconductivity of the used water solution of the polymeraniline sulfonic with a mass concentration of 5% ismeasured and the result is shown in Fig. 4. It is seen thatthe conductivity increases with temperature and theused electro-conductive polymer has a conductivity of13.1mS/cm at room temperature of 25 1C and is compar-able to the conductivity value 12.9 of KCl solutionat 0.1mol/l.In the experimental test, a mixture fluid of magnetic fluid

and electro-conductive polymer is made, which is water-based magnetic fluid (Ferrotec: MSGW11) mixing withpolymer aniline sulfonic acid by a weight ratio of 1:1.The mixed fluid has been tested to be very stable aftermixing, even when left for 1 month. The conductivityof the used mixing fluid is measured and the result isshown in Fig. 5. It is found that the conductivity alsoincreases with temperature and the mixture fluid has aconductivity of 14.2mS/cm at room temperature of 25 1C.A comparison of Fig. 4 with Fig. 5 shows that thedependence of the conductivity on temperature for theelectro-conductive polymer solution is larger than that ofthe mixing fluid. The reason for this result is not discussedin the present paper.Guass meter (provided by Denshijiki Industry Co., Ltd.)

with an accuracy 72% is used to measure magnetic fluxdensity, from which an average magnetic flux density isobtained at 256mT not only in the x-direction but also inthe y-direction. All the results presented in the paper arecarried out under the laminar flow condition, withReynolds number less than 150.

� [m

S/cm

]

T [K]

273.15 300 350 4000

10

20

30

Fig. 4. The measured variation of conductivity with temperature of

polymer aniline sulfonic solution at 5% mass concentration.

ARTICLE IN PRESS

273.15

� [m

S/cm

]

T [K]

280 2905

10

15

20

300 310 320

Fig. 5. The measured variation of conductivity with temperature of the

mixing fluid of electro-conductive polymer and magnetic fluid.

Speed ofworking fluid

Electrode

2wL

2h

Magnetic fluxB

Ju

R

V

Insulator

Channel widthChannel

Externalload

Channel

Output

Voltmeter

Output voltage

Internal resistance

External load

J

R

V

r

V0

Output

Electromotive force

z

x

y

Fig. 6. (a) A schematic diagram of Faraday MHD power generator in the

present study. (b) Schematic of equivalent circuit of the Faraday MHD

power generator.

Calculated valueExperimental value

Gou

t [W

]

K [-]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

(×10-11)

0.25 0.5 0.75 1

Fig. 7. Electric output vs. load factor under Reynolds number 25.0 and at

temperature 25 1C.

H. Yamaguchi et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 1406–1411 1409

3. Results and discussion

The power generation from the system in the paper isbased on Faraday’s law of electromagnetic induction.Fig. 6 gives a schematic diagram of Faraday’s powergenerator for the present study and equivalent circuitschematic of the Faraday power generator. From Fig. 6,electromotive force and internal resistance can be obtained

as follows:

V0 ¼ 2uxBzw, (1)

r ¼w

shL. (2)

Here load factor K is defined by (which also represents aphysical meaning of electric conversion efficiency)

K ¼V

V0¼

E

uxBz

¼R

Rþ r. (3)

A simple theoretical derivation is carried out in order toobtain the power generation for the system and the detailsof theoretical derivation can be seen in Ref. [5]:

Gout ¼ �VJ ¼ 4su2xB2Kð1� KÞhwL. (4)

In the present study, the power generation of the electro-conductive polymer alone is first investigated. The mea-sured and calculated variations of the power generationGout with the load factor are shown in Fig. 7. It is seen thata maximal value of Gout is obtained at 1.0� 10�11W atReynolds number 25.0 and temperature 25.0 1C. The resultis a little disappointing, because the output value is small,although the power generation data measured in the testare found in good agreement with the theoreticallyobtained values based on Eq. (4). The agreement alsovalidates the theoretical derivation of the electric outputfrom the present system. But on the other hand, the resultis also encouraging and positive, because the systemaims to be used as micro-size energy supply apparatus. Itshould be mentioned here that Reynolds number of 25.0 isselected, because Reynolds number higher than 25.0 cannotbe achieved because of high viscosity of the used polymerfluid. Therefore, focus has to be transferred on the mixingfluid of electro-conductive polymer and magnetic fluid.The measured values of electromotive force V0 at

different Reynolds numbers and at the load factor ofK ¼ 1 are presented in Fig. 8, in which calculated values ofV0 are also plotted. From the result, it is seen that the

ARTICLE IN PRESS

(×10-4)

Experimental valueCalculated value

V0

[V

]

Re [-]

0

1

2

3

4

5

50 100 150 200

Fig. 8. Measured and calculated electromotive force of the MHD power

generator at load factor K ¼ 1, using a mixture fluid of magnetic fluid and

electro-conductive polymer.

Experimental valueRe=50Re=100Re=150

Calculated valueRe=50Re=100Re=150

K [-]

Gou

t [W

]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6(×10-10)

0.25 0.5 0.75 1

Fig. 9. Electric output vs. load factor under different Reynolds numbers

at temperature 25 1C.

H. Yamaguchi et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 1406–14111410

measured values of V0 are in a good agreement with thecalculated V0. It is also seen that the electromotive forceincreases with Reynolds number, which shows Reynoldsnumber has an obvious influence on the power generation.The value of V0 at the Re ¼ 150 is measured at3.3� 10�4 V.

The variations in power generation Gout with the loadfactor under Reynolds number are shown in Fig. 9. In thisfigure, both experimental and calculated results are given.It is seen that the power generation Gout increases with theload factor K until K ¼ 0.5, and after K ¼ 0.5, Gout

decreases with increase in load factor K. A maximal valueof Gout is found at the load factor of K ¼ 0.5 for thedifferent Reynolds numbers. In addition, it is also seen thatpower generation Gout increases with Reynolds number.Reynolds number has a great influence on the electricoutput value of Gout. From the results shown in Fig. 9, amaximal value of Gout is obtained at 1.3� 10�10W withinthe present test range. The agreement between themeasured data and theoretical value for the powergeneration Gout is achieved again. The power generationvalue is still small and it is difficult for the present mixingfluid to be used in a normal-size apparatus but may bepotential use in the micro-size system shown in Fig. 1. Inorder to achieve a more practical electric output, we needto further observe Eq. (4). Based on this equation, it can beseen that fluid flow velocity, magnetic flux density andelectric conductivity have obvious influences on the powergeneration output Gout. Among the influencing factors,especially, the flow velocity and magnetic flux density havegreatest influences on Gout, because Gout is directlyproportional to square of both fluid flow velocity andmagnetic flux density. A great increase of Gout can beachieved by increasing the fluid flow velocity or magneticflux density. Therefore, priority is firstly put on the fluidflow velocity and magnetic strength to improve the electricoutput. Furthermore, electric conductivity s is also an

important factor for enhancing the electric output Gout.The obtained small values of Gout in the present test cangreatly be contributed to the low conductivity of the usedmixing fluid, although an electro-conductive polymer witha high conductivity is used. Its conductivity of the mixturefluid is less than 1 millionth of liquid metal values. In orderto achieve a practical value of Gout, the electric conductivityof the used working fluid has to be increased. For someMHD power generation method, mercury used in the hightemperature is toxic, although its conductivity is high. Inthe future, low-melting-point alloy can be considered as apotential fluid to be used in the present study forestablishing a MHD power generator operating at roomtemperature as a micro-distributed electricity supply. Thelow-melting-point alloy is non-toxic and also has a veryhigh conductivity. In addition, increasing the channel sizeis also an effective way to increase the electric output ofGout, because Gout is directly proportional not only tolength but also to width and height.

4. Conclusions

(1)

MHD power generation using electro-conductive polymerand its mixture with magnetic fluid is introduced. For theused fluid, an experimental set-up is designed, constructedand tested to measure the performance of the electricoutput. The calculated results are found in good agreementwith the measured data, which verifies the theoreticalanalysis used in the present study.

(2)

The power generation is found to increase withReynolds number, magnetic strength and electricconductivity. A maximal value of the power generationis obtained at the load factor 0.5.

(3)

Based on the obtained data, to obtain a more practicalelectric output, priority should firstly be focused onincreasing the flow velocity and magnetic strength.Furthermore, electric conductivity is an important

ARTICLE IN PRESSH. Yamaguchi et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 1406–1411 1411

factor and will have to be improved and low-melting-point alloy is considered as a potential workingfluid, because this kind of fluid can be used as workingfluid at room temperature and also has very highconductivity.

Acknowledgments

This study was supported by the Academic FrontierResearch Project on ‘‘Next Generation Zero-EmissionEnergy Conversion System’’ of Ministry of Education,Culture, Sports, Science and Technology, Japan.

References

[1] M.R. Perry, B.M. Berkovky, Thermomechanics of Magnetic Fluids,

Hemisphere, Washington, DC, 1978, pp. 224–225.

[2] K. Shimada, S. Kamiyama, J. Magn. Magn. Mater. 122 (1993) 214.

[3] S. Shuchi, K. Sakatani, H. Yamaguchi, J. Magn. Magn. Mater. 289

(2005) 257.

[4] N. Inoue, H. Yamaguchi, T. Kuwahara, Heat transport characteristics

of heat transport device using temperature sensitive magnetic fluid in

different subcool, JSMF Annual Meeting 2006, Kanazawa, August

4–6, 2006, pp. 388–389.

[5] K. Kojima, Characteristics of MHD power generation using electro-

conductive polymer mixing magnetic fluid in Faraday channel,

Master’s Thesis, Department of Mechanical Engineering, Doshisha

University, Japan, 2006, pp. 8–20.