Research Article Coefficient of Thermal Diffusivity of...

Research ArticleCoefficient of Thermal Diffusivity of Insulation BrickDeveloped from Sawdust and Clays

E Bwayo and S K Obwoya

Department of Physics Kyambogo University PO Box 1 Kyambogo Kampala Uganda

Correspondence should be addressed to S K Obwoya ksobwoyayahoocouk

Received 29 July 2014 Revised 12 November 2014 Accepted 3 December 2014 Published 29 December 2014

Academic Editor Jim Low

Copyright copy 2014 E Bwayo and S K Obwoya This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

This paper presents an experimental result on the effect of particle size of a mixture of ball clay kaolin and sawdust on thermaldiffusivity of ceramic bricks Amixture of dry powders of ball clay kaolin of the same particle size and sawdust of different particlesizes was mixed in different proportions and then compacted to high pressures before being fired to 950∘CThe thermal diffusivitywas then determined by an indirect method involving measurement of thermal conductivity density and specific heat capacityThe study reveals that coefficient of thermal diffusivity increases with decrease in particle size of kaolin and ball clay but decreaseswith increase in particle size of sawdust

1 Introduction

In a recent study by Manukaji [1] thermal diffusivity is veryimportant in all nonequilibrium heat conduction problemsin solid objects The time rate of change of temperaturedepends on the numerical value of thermal diffusivity Thephysical significance of thermal diffusivity is associatedwith the diffusion of heat into the medium during changesof temperature with time Nonequilibrium heat transferis important because of the large number of heating andcooling problems occurring industrially [2] In metallurgicalprocesses it is necessary to predict cooling and heating ratesfor various geometries of conductors in order to predict thetime required to reach certain temperatures Materials withhigh thermal mass will take longer for heat to travel from thehot face of the brick to the cold face and will also take longto release their heat once the heat source is removed [3 4]A paper by Aramide [5] points out that when brick samplesmade with sawdust are fired the sawdust admixture burns offbetween 450ndash550∘C [6] leaving pores (air voids) in the brickwhich retards heat flow

One of the problems facing the building industry inUganda is the high consumption of electric energy causedby poor ventilation and air conditioning systems This is

mainly due to lack of thermal insulation techniques inbuildings [7 8] Nevertheless there are no classified thermalinsulators produced in Uganda The country depends onimported insulation materials which are very expensive andare not easily accessed by the local industry and yet there areabundant mineral deposits in different parts of the countrywhich can provide potential rawmaterials for the productionof different ceramic products like thermal insulating bricksThus this paper presents the results of an experimental studyof the effect of particle size on thermal diffusivity of claybricks of composition as shown in Table 1 which have beenfabricated from a combination of kaolin ball clay and woodsawdust of different particle sizes

2 Experimental Procedures

21 Materials Processing The rawmaterials used in this studywere kaolin ball clay and hard wood sawdust The sawdustwas obtained from mahogany The hard wood was preferredbecause when incorporated in clay bricks it forms uniformpores has high calorific values and does not cause bloating[9] The kaolin was collected from Mutaka in South WesternUganda while ball clay was collected from Ntawo (Mukono)25 km east of the capital city Kampala The ball clay and

Hindawi Publishing CorporationJournal of CeramicsVolume 2014 Article ID 861726 6 pageshttpdxdoiorg1011552014861726

2 Journal of Ceramics

kaolin were separately soaked in water for seven days toallow them to dissolve completely in order to separate thecolloids from heavy particles like stones sand and rootsThe clay was then dried and milled into powder form inelectric ball millThe powders were sieved through test sievesstuck together on a mechanical test sieve shaker The particlesize ranges 0ndash45 120583m 45ndash53120583m 53ndash63120583m 63ndash90 120583m 90ndash125 120583m and 125ndash154120583m were obtained separately for kaolinand ball clay Similarly powders of sawdust of particle sizeranges 0ndash125120583m 125ndash154120583m 154ndash180 120583m 180ndash355 120583m and355ndash425120583m were also prepared

The study was carried out using two sets of batchformulations In the first part the batch formulations A

1ndashA5

had compositions of kaolin and ball clay of the same particlesize ranges which were mixed with equal masses of sawdustof three different particle size ranges in the ratios 9 7 4 byweight as shown in Table 1Themixture of these powders wasfirst sun dried and then compacted to pressure of 50MPa intorectangular specimens with dimensions of 1051 cm times 525 cmtimes 198 cm The test samples were fired to 950∘C in an electricfurnace in two stages In the first stage they were dried at aheating rate of 233∘Cminminus1 to 110∘C and this temperaturewasmaintained for four hours in order to remove anywater inthe sample In the second stage the sampleswere fired at a rateof 6∘Cminminus1 to 950∘C At this temperature the holding timewas one hour before the furnace was switched off to allow thesamples to cool naturally to room temperature

In the second part of the study batch formulations B1ndash

B5had each of the particle size ranges 0ndash125 120583m 125ndash154120583m

154ndash180 120583m 180ndash355 120583m and 355ndash425 120583m of sawdust mixedwith kaolin and ball clay of the same particle size ranges in theratio 4 9 7 as shown in (Table 1) before compacting themat apressure of 50MPa into rectangular specimens of dimensions1051 cm times 525 cm times 198 cm A similar firing process as forthe first batch formulation was followed Each of the sampleformulations had a total mass of 200 g (90 g of kaolin 70 g ofball clay and 40 g of sawdust)

22 Determination of the Coefficient of Thermal DiffusivityThe coefficient of thermal diffusivity was determined frommeasured values of the specific heat capacity thermal con-ductivity and density using the following equation derivedfrom Fourierrsquos law of heat conduction through solid

120572 =119896

ℓ119888119901

(1)

where 120572 is the thermal diffusivity 119896 is the thermal conductiv-ity ℓ is density and 119888

119901is specific heat capacity [10]

The thermal conductivity was measured by the QuickThermal Conductivity Meter (QTM-500) with sensor probe(PD-11) which uses transient technique (nonsteady state) tostudy the heat conduction of the samples [11 12] Specific heatcapacity was determined by method of mixtures [13] and thedensity was determined by measuring the dimensions andmass of the sample Measurements of thermal conductivitydensity and specific heat capacity were performed at roomtemperature

Table 1 Formulation of the brick samples

Sample

Particle size (120583m)Kaolin

(90 g) + ballclay (70 g)

Sawdust addition (40 g)

A1

90ndash125 0ndash125 125ndash154 154ndash180A2




0ndash45 0ndash125 125ndash154 154ndash180

SampleParticle size (120583m)

Sawdust(40 g) Kaolin (90 g) + ball clay (70 g) addition

B1

0ndash125 63ndash90 90ndash125 125ndash154B2





23 Chemical Composition The chemical composition ofthe fired samples was determined by the X-ray fluorescence(XRF) spectrometer model X1015840 Unique ll [14] to establish thechemical composition ofmajor compounds that influence thethermal properties of insulation clay bricks Table 2

3 Results and Discussions

31 Effect of Particle Size on the Coefficient of ThermalDiffusivity The coefficient of thermal diffusivity was deter-mined by an indirect method involving the measurement ofthermal conductivity specific heat capacity and density offired samples [2 10] The effect of particle size on thermalconductivity density and specific heat capacity and thermaldiffusivity is discussed below

311 Effect of Particle Size on Thermal Conductivity Theresults (Figure 1) show that thermal conductivity increaseswith decrease in particle size of kaolin and ball clay forfixed particle size of sawdust This is because larger particlescreate large pores due to poor filling of the voids thatcontain air after firing compared to small particle sizes[15 16] Thermal conduction of a ceramic material dependson thermal conductive pathways which are affected by themicrostructure particle size distribution and the amount ofair space or voids created during the firing of a body [17]Figure 2 shows that thermal conductivity decreases whenthe particle size of sawdust incorporated into the clay mixincreasesThis is because particle size of combustible organicwaste determines the amount of air spaces that are createdin the insulation clay brick [18ndash20] In addition thermalconductivity decreases further when particle size of themixture of kaolin and ball clay increases due to less contactbetween particles [21] Interlocking of clay particles dependson particle size distribution and particle size range of small

Journal of Ceramics 3

Table 2 Chemical composition of fired samples

Compound SiO2 Al2O3 Fe2O3 CaO TiO2 Na2O MgO K2O MnO2 P2O5

Weight () 6898 2229 187 115 048 204 104 254 005 057

40 50 60 70 80 90 100 110 120 130021

0215022

0225023

0235024

0245

Particle size of kaolin and ball clay (120583m)

125120583m of sawdust addition154120583m of sawdust addition180120583m of sawdust addition

Ther

mal

cond

uctiv

ity (W

mminus1

Kminus1)

Figure 1 Effect of particle size of kaolin and ball clay on thermalconductivity with different particle size of sawdust

100 150 200 250 300 350 400015016017018019

02021022023

Particle size of sawdust (120583m)

90120583m of kaolin and ball clay125120583m of kaolin and ball clay154120583m of kaolin and ball clay

Ther

mal

cond

uctiv

ity (W

mminus1

Kminus1)

Figure 2 Effect of particle size of sawdust on thermal conductivityat different particle size of a mixture of kaolin and ball clay

and large particles and also on whether the body is made ofmonosized particles or multiple size particles

312 Effect of Particle Size on Density The density of thesamples increases with decreasing particle size of the mixtureof kaolin and ball clay at fixed particle size of sawdust(Figure 3) Smaller particle sizes have more contact pointsthat allow for more cohesion and lubrication of kaolin byball clays Multiple particle sizes in a ceramic body increasepacking of particles and produce high density body becausefiner grains go into the interparticle voids of the coarserparticles and thus increase the packing density This studyalso shows that there is further decrease in density withincrease in particle size of sawdust at fixed particle size ofkaolin and ball clay [20]

50 60 70 80 90 100 110 120 13010801100112011401160118012001220


Den

sity

(kgmminus3)


Figure 3 Variation of density with particle size of kaolin and ballclay for different particle size of sawdust

100 150 200 250 300 350 40011001120114011601180120012201240


Den

sity

(kgmminus3)


Figure 4 Variation of density with particle size of sawdust atdifferent particle size of kaolin and ball clay

In Figure 4 density of the samples decreaseswith increasein particle size of sawdust for fixed particle size of kaolin andball clay Small pores that are created by small particle sizeof sawdust tend to be closed during densification as a resultof formation of intergranular contact areas while large poreswill remain in the clay matrix during firing and maturing[18] This is attributed to the sufficient length of sawdust thatimproves the bond at the sawdust-clay interface to oppose thedeformation and clay contraction during drying and firing[9]

313 Variation of Specific Heat Capacity with Particle SizeThe specific heat capacities for samples A

1to A5are generally

lower than those of B1to B5(Figures 5 and 6) This implies

that lower thermal diffusivity can be achieved by use ofbigger particle sizes of sawdust [9] The specific heat capacityincreases with increase in particle size of clay materials


50 60 70 80 90 100 110 120 130700750800850900950

100010501100



Spec

ific h

eat c

apac

ity(J

kgminus

1 Kminus1 )

Figure 5 Effect of particle size of amixture of kaolin and ball clay ofspecific heat capacity at different particle sizes of sawdust addition

150 200 250 300 350 400

1000

1050

1100

1150

1200

1250



Spec

ific h

eat c

apac

ity(J

kgminus

1 Kminus1 )

Figure 6 Effect of particle size of sawdust on specific heat capacityat different particle size of a mixture of kaolin and ball clay

(Figure 5) used and increase in particle size of sawdustaddition (Figure 6)

314 Coefficient of Thermal Diffusivity The coefficient ofthermal diffusivity increases as the particle size of themixtureof kaolin and ball clay decreases at fixed particle size ofsawdust addition (Figure 7) The principal effect of particlesize on the thermal diffusivity of the solid material is relatedto the amount of solid and air space which the heat has totransverse in passing through the material This is attributedto large particle size which results in high porosity levels dueto poor filling of voids between large size particles comparedto small sizes thus creating large air spaces [21] The largeproportion of air produces low value of the coefficient of ther-mal diffusivity because of its low thermal conductivity Thedecrease in particle size increases particle content per unitvolume which decreases the average interparticle distanceof the clay matrix This results in close packing of particlesthat leads to densification of clay bricks which increasesthermal diffusivity [16 20] Hence a fine-grained closed-textured material (small particle size) has a much greaterthermal diffusivity than one with a coarser open texture

50 60 70 80 90 100 110 120 130

16171819

22122232425


times10minus7

Coe

ffici

ent o

f the

rmal

diff

usiv

ity


(m2

sminus1 )

Figure 7 Effect of particle size of a mixture of kaolin and ball clayon thermal diffusivity at fixed particle size of sawdust

100 150 200 250 300 350 400111213141516171819times10minus7

Coe

ffici

ent o

f the

rmal

diff

usiv

ity (m

2sminus

1 )



Figure 8 Variation of thermal diffusivity with particle size ofsawdust at different particle size of a mixture of kaolin and ball clay

(large particle size) Small particle sizes enhance low thermalresistance because the contact points for thermal conductionare very closely packed Large grain size of kaolin and ballclay produces bricks that are more porous and thus moreresistant to sudden temperature changes across the specimen[1 22] The low thermal diffusivity values are suitable forminimizing heat conduction It is observed (Figure 7) thatincreasing particle size of sawdust addition further decreasesthe thermal diffusivity

Thermal diffusivity decreaseswith increase in particle sizeof sawdust at fixed particle size of a combination of kaolinand ball clay (Figure 8) This is because particles of sawdustburn out between 450-550∘C [6] leaving pores or voids inthe samples During drying and firing densification takesplace and small pores created by small particle size of sawdusttend to be closed by clay minerals as a result of formation ofintergranular contact areas while large pores will persist inthe clay matrix [18]


Incorporation of sawdust into the ceramic body whichis removed during the firing step leaves pores whose sizesare related to the organic particle sizes Finer sawdust formssmaller pores most of which may be eliminated duringdensification while large particle sizes form large poresSawdust of large particle size improves the bond at thesawdust-clay interface that opposes the deformation andclay contraction This yields high porosity low density lowthermal conductivity and low rate of change of temperatureacross the specimen Hence thermal diffusivity decreases asparticle size of sawdust increases Generally the values ofthermal diffusivity of B

1to B5are lower than those of A

1to

A5 This is a result of the multiplicative porosity created by

clay and sawdust addition

32 Chemical Composition The percentage composition ofSiO2is 680 while that of Al

2O3is 220 According

to the Bureau of Energy Efficiency [23] report on fireclayrefractories low density fireclay refractories consist of alu-minum silicates with varying silica content between 67 and77 and Al

2O3content between 23 and 33 The chemical

composition of alumina in the developed samples can beimproved either by beneficiating the raw materials (kaolinand ball clay) or by increasing the percentage composition ofkaolin in the samplesThe clay samples contain less than 90of the fluxing components (K

2O Na

2O and CaO)

33 Implications The physical significance of low values ofthermal diffusivity is associated with the low rate of change oftemperature through thematerial during the heating processThe samples therefore have low values of the coefficientof thermal diffusivity and are suitable for use as thermalinsulators The suitable thermal insulator is the samplecontaining a combination of kaolin and ball clay of particlesize range of 125ndash154120583m with sawdust of particle size rangeof 355ndash425120583m This combination was characterized by thelowest value thermal diffusivity of 116 times 10minus7m2 sminus1 and caneasily be prepared for commercial production of thermalinsulation bricks

4 Conclusions

The results of the study show that all the samples analyzedare good thermal insulators and the coefficient of thermaldiffusivity is directly affected by particle size of a combinationof kaolin and ball clay minerals as well as particle sizeof sawdust addition Thus from the overall experimentalanalysis carried out the following was observed

(1) The coefficient of thermal diffusivity increases withdecrease in particle size of a mixture of kaolin andball clay at fixed particle size of sawdust additionSawdust addition of larger particle size decreasesthermal diffusivity even at very small particle size ofkaolin and ball clay

(2) The coefficient of thermal diffusivity decreases withincrease in particle size of sawdust addition to a fixedparticle size of kaolin and ball clay Incorporation of

kaolin and ball clay of a much higher particle sizefurther decreases the coefficient of thermal diffusivitydue to the multiplicative effect of higher porosityproduced by sawdust and clay minerals

(3) The samples contain suitable compositions of silicaand alumina which are suitable for lightweight hightemperature insulation bricks

(4) The samples therefore have low values of the coeffi-cient of thermal diffusivity and are suitable for use asthermal insulators

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the staff at KyambogoUniversity for their guidance and support during the courseof the study and research Further thanks go to the Man-agement and staff of Uganda Industrial Research InstituteUIRI (Department of Ceramics) for availing their labs andequipment to be used for the research and the Departmentof Physics Makerere University In a special way the authorswish to appreciate the financial support they received fromMs Nanyama Christine Dr Mayeku Robert and his wifeMrs Kate Mayeku

References

[1] JUManukaji ldquoThe effects of sawdust addition on the insulatingcharacteristics of clays from the Federal Capital Territoryof Abujardquo International Journal of Engineering Research andApplications vol 3 no 2 pp 6ndash9 2013

[2] F Colangelo G de Luca and C Ferone Experimental andNumerical Analysis of Thermal and Hygrometric Characteristicsof Building Structures Employing Recycled Plastic Aggregates andGeopolymer Concrete University of Napoli Parthenope NapoliItaly 2013

[3] R T Faria Jr V P Souza C M F Vieira and R ToledoldquoCharacterization of clay ceramics based on the recycling ofindustrial residuesrdquo in Characterization Raw Materials Pro-cessing Properties Degradation and Healing C Sikalidis Ed2011

[4] A B E Bhatia Overview of Refractory Materials PDH OnlineFairfax Va USA 2012

[5] OAramide Journal ofMinerals andMaterials Characterizationand Engineering 2012 httpwwwSciRPorgjournaljmmce

[6] Government of Uganda State of Uganda Population ReportPlanned Urbanization for Ugandarsquos Growing Population Gov-ernment of Uganda Kampala Uganda 2007

[7] S MukiibiThe Effect of Urbanisation on the Housing Conditionsof the Urban Poor in Kampala Department of ArchitectureMakerere University Kampala Uganda 2008

[8] H Chemani and B Chemani ldquoValorization of wood sawdust inmaking porous clay brickrdquo Scientific Research and Essays vol 8no 15 pp 609ndash614 2013


[9] R E B Sreenivasula Basic Mechanisms of Heat TransfermdashFourierrsquos Law of Heat Conduction College of Food Science andTechnology Ranga Agricultural Unuversity Pulivendula India2013

[10] ASTM D 5334-92 D 5930-97 and IEEE 442-1981 standards[11] A-B Cherki B Remy A Khabbazi Y Jannot and D Baillis

ldquoExperimental thermal properties characterization of insulat-ing cork-gypsum compositerdquo Construction and Building Mate-rials vol 54 pp 202ndash209 2014

[12] ASTMD411-08 Standard TestMethod for Specific Heat Capacityof Rocks and Soils ASTM International West ConshohockenPa USA 2008

[13] M S Shackley X-Ray Fluorescence Spectrometry (XRF) inGeoarchaeology Department of Anthropology University ofCalifornia Berkeley Calif USA 2011

[14] A A Kadir A Mohajerani F Roddick and J Buck-eridgeldquoDensity strength thermal conductivity and leachate charac-teristics of light-weight fired clay bricks incorporating cigarettebuttsrdquo International Journal of Civil and Environmental Engi-neering vol 2 no 4 pp 1035ndash1040 2010

[15] G Viruthagiri S Nithya Nareshananda and N ShanmugamldquoAnalysis of insulating fire bricks from mixtures of clays withsawdust additionrdquo Indian Journal of Applied Research (Physics)vol 3 no 6 2013

[16] W Ling A Gu G Liang and L Yuan ldquoNew compositeswith high thermal conductivity and low dielectric constant formicroelectronic packagingrdquo Polymer Composites vol 31 no 2pp 307ndash313 2010

[17] H Binici O Aksogan M N Bodur E Akca and S KapurldquoThermal isolation and mechanical properties of fibre rein-forced mud bricks as wall materialsrdquo Construction and BuildingMaterials vol 21 no 4 pp 901ndash906 2007

[18] R Saiah B Perrin and L Rigal ldquoImprovement of thermalproperties of fired clays by introduction of vegetable matterrdquoJournal of Building Physics vol 34 no 2 pp 124ndash142 2010

[19] S Zhang X Y Cao Y M Ma Y C Ke J K Zhang and F SWang ldquoThe effects of particle size and content on the thermalconductivity and mechanical properties of Al

2

O3

high densitypolyethylene (HDPE) compositesrdquo Express Polymer Letters vol5 no 7 pp 581ndash590 2011

[20] N Meena Seema Effects of particle size distribution on theproperties of alumina refractories [MS thesis] Department ofInstitute of Technology Rourkela India 2011

[21] A G E Marwa F M Mohamed S A H El-Bohy C MSharaby C M El-Menshawi and H Shalabi ldquoFactors thataffected the performance of fire clay refractory bricksrdquo in Gor-nictwo i Geoinzynieria Rok 33 Zeszyt 4 Central MetallurgicalResearch and Development Institute Helwan Egypt 2009

[22] Bureau of Energy Efficiency Energy Efficiency in ThermalUtilities Energy Efficiency Guide for Industry in Asia Ministryof Power UNEP 2005

[23] F Colangelo G De Luca and C Ferone Experimental andNumerical Analysis of Thermal and Hygrometric Characteristicsof Building Structures Employing Recycled Plastic Aggregates andGeopolymer Concrete University of Napoli Parthenope CentroDirezionale Naples Italy 2013

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


kaolin were separately soaked in water for seven days toallow them to dissolve completely in order to separate thecolloids from heavy particles like stones sand and rootsThe clay was then dried and milled into powder form inelectric ball millThe powders were sieved through test sievesstuck together on a mechanical test sieve shaker The particlesize ranges 0ndash45 120583m 45ndash53120583m 53ndash63120583m 63ndash90 120583m 90ndash125 120583m and 125ndash154120583m were obtained separately for kaolinand ball clay Similarly powders of sawdust of particle sizeranges 0ndash125120583m 125ndash154120583m 154ndash180 120583m 180ndash355 120583m and355ndash425120583m were also prepared

The study was carried out using two sets of batchformulations In the first part the batch formulations A

1ndashA5

had compositions of kaolin and ball clay of the same particlesize ranges which were mixed with equal masses of sawdustof three different particle size ranges in the ratios 9 7 4 byweight as shown in Table 1Themixture of these powders wasfirst sun dried and then compacted to pressure of 50MPa intorectangular specimens with dimensions of 1051 cm times 525 cmtimes 198 cm The test samples were fired to 950∘C in an electricfurnace in two stages In the first stage they were dried at aheating rate of 233∘Cminminus1 to 110∘C and this temperaturewasmaintained for four hours in order to remove anywater inthe sample In the second stage the sampleswere fired at a rateof 6∘Cminminus1 to 950∘C At this temperature the holding timewas one hour before the furnace was switched off to allow thesamples to cool naturally to room temperature

In the second part of the study batch formulations B1ndash

B5had each of the particle size ranges 0ndash125 120583m 125ndash154120583m

154ndash180 120583m 180ndash355 120583m and 355ndash425 120583m of sawdust mixedwith kaolin and ball clay of the same particle size ranges in theratio 4 9 7 as shown in (Table 1) before compacting themat apressure of 50MPa into rectangular specimens of dimensions1051 cm times 525 cm times 198 cm A similar firing process as forthe first batch formulation was followed Each of the sampleformulations had a total mass of 200 g (90 g of kaolin 70 g ofball clay and 40 g of sawdust)

22 Determination of the Coefficient of Thermal DiffusivityThe coefficient of thermal diffusivity was determined frommeasured values of the specific heat capacity thermal con-ductivity and density using the following equation derivedfrom Fourierrsquos law of heat conduction through solid

120572 =119896

ℓ119888119901

(1)

where 120572 is the thermal diffusivity 119896 is the thermal conductiv-ity ℓ is density and 119888

119901is specific heat capacity [10]

The thermal conductivity was measured by the QuickThermal Conductivity Meter (QTM-500) with sensor probe(PD-11) which uses transient technique (nonsteady state) tostudy the heat conduction of the samples [11 12] Specific heatcapacity was determined by method of mixtures [13] and thedensity was determined by measuring the dimensions andmass of the sample Measurements of thermal conductivitydensity and specific heat capacity were performed at roomtemperature

Table 1 Formulation of the brick samples

Sample

Particle size (120583m)Kaolin

(90 g) + ballclay (70 g)

Sawdust addition (40 g)

A1






SampleParticle size (120583m)

Sawdust(40 g) Kaolin (90 g) + ball clay (70 g) addition

B1






23 Chemical Composition The chemical composition ofthe fired samples was determined by the X-ray fluorescence(XRF) spectrometer model X1015840 Unique ll [14] to establish thechemical composition ofmajor compounds that influence thethermal properties of insulation clay bricks Table 2

3 Results and Discussions

31 Effect of Particle Size on the Coefficient of ThermalDiffusivity The coefficient of thermal diffusivity was deter-mined by an indirect method involving the measurement ofthermal conductivity specific heat capacity and density offired samples [2 10] The effect of particle size on thermalconductivity density and specific heat capacity and thermaldiffusivity is discussed below

311 Effect of Particle Size on Thermal Conductivity Theresults (Figure 1) show that thermal conductivity increaseswith decrease in particle size of kaolin and ball clay forfixed particle size of sawdust This is because larger particlescreate large pores due to poor filling of the voids thatcontain air after firing compared to small particle sizes[15 16] Thermal conduction of a ceramic material dependson thermal conductive pathways which are affected by themicrostructure particle size distribution and the amount ofair space or voids created during the firing of a body [17]Figure 2 shows that thermal conductivity decreases whenthe particle size of sawdust incorporated into the clay mixincreasesThis is because particle size of combustible organicwaste determines the amount of air spaces that are createdin the insulation clay brick [18ndash20] In addition thermalconductivity decreases further when particle size of themixture of kaolin and ball clay increases due to less contactbetween particles [21] Interlocking of clay particles dependson particle size distribution and particle size range of small




Weight () 6898 2229 187 115 048 204 104 254 005 057

40 50 60 70 80 90 100 110 120 130021

0215022

0225023

0235024

0245



Ther

mal

cond

uctiv

ity (W

mminus1

Kminus1)


100 150 200 250 300 350 400015016017018019

02021022023



Ther

mal

cond

uctiv

ity (W

mminus1

Kminus1)




50 60 70 80 90 100 110 120 13010801100112011401160118012001220


Den

sity

(kgmminus3)



100 150 200 250 300 350 40011001120114011601180120012201240


Den

sity

(kgmminus3)





1to A5are generally




50 60 70 80 90 100 110 120 130700750800850900950

100010501100



Spec

ific h

eat c

apac

ity(J

kgminus

1 Kminus1 )


150 200 250 300 350 400

1000

1050

1100

1150

1200

1250



Spec

ific h

eat c

apac

ity(J

kgminus

1 Kminus1 )




50 60 70 80 90 100 110 120 130

16171819

22122232425


times10minus7

Coe

ffici

ent o

f the

rmal

diff

usiv

ity


(m2

sminus1 )


100 150 200 250 300 350 400111213141516171819times10minus7

Coe

ffici

ent o

f the

rmal

diff

usiv

ity (m

2sminus

1 )









1to




2O3is 220 According




2O Na

2O and CaO)


4 Conclusions









Acknowledgments


References





















2

O3













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Weight () 6898 2229 187 115 048 204 104 254 005 057

40 50 60 70 80 90 100 110 120 130021

0215022

0225023

0235024

0245



Ther

mal

cond

uctiv

ity (W

mminus1

Kminus1)


100 150 200 250 300 350 400015016017018019

02021022023



Ther

mal

cond

uctiv

ity (W

mminus1

Kminus1)




50 60 70 80 90 100 110 120 13010801100112011401160118012001220


Den

sity

(kgmminus3)



100 150 200 250 300 350 40011001120114011601180120012201240


Den

sity

(kgmminus3)





1to A5are generally




50 60 70 80 90 100 110 120 130700750800850900950

100010501100



Spec

ific h

eat c

apac

ity(J

kgminus

1 Kminus1 )


150 200 250 300 350 400

1000

1050

1100

1150

1200

1250



Spec

ific h

eat c

apac

ity(J

kgminus

1 Kminus1 )




50 60 70 80 90 100 110 120 130

16171819

22122232425


times10minus7

Coe

ffici

ent o

f the

rmal

diff

usiv

ity


(m2

sminus1 )


100 150 200 250 300 350 400111213141516171819times10minus7

Coe

ffici

ent o

f the

rmal

diff

usiv

ity (m

2sminus

1 )









1to




2O3is 220 According




2O Na

2O and CaO)


4 Conclusions









Acknowledgments


References





















2

O3













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




50 60 70 80 90 100 110 120 130700750800850900950

100010501100



Spec

ific h

eat c

apac

ity(J

kgminus

1 Kminus1 )


150 200 250 300 350 400

1000

1050

1100

1150

1200

1250



Spec

ific h

eat c

apac

ity(J

kgminus

1 Kminus1 )




50 60 70 80 90 100 110 120 130

16171819

22122232425


times10minus7

Coe

ffici

ent o

f the

rmal

diff

usiv

ity


(m2

sminus1 )


100 150 200 250 300 350 400111213141516171819times10minus7

Coe

ffici

ent o

f the

rmal

diff

usiv

ity (m

2sminus

1 )









1to




2O3is 220 According




2O Na

2O and CaO)


4 Conclusions









Acknowledgments


References





















2

O3













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






1to




2O3is 220 According




2O Na

2O and CaO)


4 Conclusions









Acknowledgments


References





















2

O3













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials















2

O3













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Coefficient of Thermal Diffusivity of...

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