Application of Microencapsulated Phase change material Slurry with ...

Progresses of Thermal EnergyStorage Using MicroencapsulatedPCM Slurry for Low EnergyBuilding ApplicationsXichun Wang a , Jianlei Niu a+ , Yi li b , Yinping Zhang ca. Department of Building Service Engineering, The Hong Kong Polytechnic Universityb. Institute of Textiles and Clothing, The Hong Kong Polytechnic Universityc. Department of Building Science, Tsinghua University+Corresponding author: bejlniu@polyu.edu.hk

Outline• Motivation• Properties of MPCM slurry• Heat transfer behaviors• Applications of MPCM slurry• Conclusions

Energy Consumption in theBuilding Sector• Worldwide, 1/3 of the energyresources consumed for buildingheating and cooling• An issue of combating globalwarming

Low-energy building usingthermal energy storage (TES)1. CoolingTower2. Sky RadiatorTES3. Night-timeOff-peak electricityA/CReduced Electric Power

Technical problems toovercome in PCM applicationsProblemsSolutionsSuitable melting temperatureIncongruent meltingMaterial developmentSupercoolingLiquid/solid phaseVolume changeLow thermal conductivityMicro-encapsulation( PCM particlesMicro-encapsulatedwith thin plastic shells )

Micro-encapsulated phase changematerial (MPCM) slurry• Being composed of conventionalsingle-phase fluid (e.g. water, oil,etc) and suspended MPCMparticles, a solid-liquid slurry.• MPCM particles:• 10 μm (1/10 of our hair diameter):• PCM inside• 0.3 μm thick shell of synthetic resin231

Micro-encapsulated PCM(C 16 H 33 ) slurrySEM image

DSC results of microencapsulatedhexadecane (C 16 H 34 )

Viscosity measurements (PaarPhysica 300 Rheometer)2520ExperimentsVandRelative viscosity ( - )1510500 5 10 15 20 25 30Concentration (%)

Schematic diagram of heattransfer test rigAmmeter3KVA powertransformerAutotransformerInsulatingTransformer220 VVoltmeterFlange 8 T-type thermocouplesT 0.1 0.18 0.18 0.18 0.18 0.18 0.18 0.18 0.1TFlangeData acquisitionsystemstirrerHeat transfer test section1.46 mΔPDifferential pressure transducerBypassFlowmeterValveTPTP5 LMPCM slurry loopValveTPGlycol solutionloopT PRefrigeratorSlurry reservoirPumpValveFlow meterPlate Heat exchangerPump

T lb ,T lw [ o C]Local heat transfer behaviors of MPCMslurry (laminar flow)4030201002500Q=292.7WWallPure waterMPCMRegion I Region II Region IIIl0 50 100 150 200 250 300 350hx [W/m 2o C]2000150010005000Churchill and Ozone (1973)MPCM slurry(water)0 50 100 150 200 250 300 350x/Dw p = 0.158, Re lb =1196-1170, m = 4.95 g/s

Local heat transfer behaviors of MPCMslurry (Turbulent flow)Tbx, Twx [ o C]hx [W/m 2o C]30252015105Q=802.8WPure waterWallMPCM slurryRegion I Region II Region III0 50 100 150 200 250 300 35070006500MPCM slurry60005500500045004000Choi and cho (1995)(water)350030000 50 100 150 200 250 300 350x/Dw p = 0.05, Re lb =2320-3068, m = 16.4 g/s

Correlation equation(laminar flow)Nupredicted141312111098+10%-10%( )0.4593 0.4836 −0.1277Num = 0.8148Rem PrmSte ⎡ L1+L2/ D⎤−⎣ ⎦Ste =C q R kp, b w d/bw ΔHρ / ρp m p b0.3059766 7 8 9 10 11 12 13 14Nu experimental

Correlation equation(Turbulent flow)605550( ) ⎤−( )−4 0.7733 2.7941 0.31590..333 −2.4349m= 4.8527× 10 Rem Prm⎡1+2/m/wNu Ste ⎣ L L D⎦μ μ45Nu predicted403530+10%-10%25201515 25 35 45 55Nu experimental

Schematic diagram of CC withMPCM slurry storageExhaustHeat recovery unit (optional)Ceiling panelOutsideAirHumidifierPreheat coilCooling coilReheat coilfanfanpumpRoomRadiatorCondenserCompressorEvaporatorMPCM slurryStorage tank

Load shifting of CC runningwith MPCM slurryPower demand (W)12001000800600400200PumpChiller for tankFanChiller for AHUJuly 1501 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Time (Hours)MPCM slurry1200Power demand [W]10008006004002000PumpChiller for cold waterFanChiller for AHU1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Time (Hours)water

Yearly energy consumption ofthree systemsThermal energy Chiller (kW.h) Fan Pump Totalstorage medium* water/slurry AHU (kW.h) (kW.h) (kW.h)— 377 614 154 23 1167MPCM slurry (18 o C) 377 614 154 4 1148Ice storage (0 o C) 1801 0 154 25 1980*Note: COP of chiller is 4.0 for MPCM slurry storage and 2.2 forice storage.

Annual energy costs of threesystems18001600WaterMPCM slurryIce storageAnnual energy cost (HK$)1400120010008006004001 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3Ratio daytime/nighttime Electricity tariff ( - )

Demonstrative CC system

Conclusions• The Hexadecane (C 16 H 34 )is chosen asmicrocapsule core material due to higher latentheat and lower supercooling.• The viscosity data measured fit well with classicalmodels.• The heat transfer was enhanced significantly dueto the presence of MPCM particles.• Two correlations for the design of heatexchangers with MPCM slurry• CC with MPCM slurry storage offers the loadshifting, peak load shaving, energy saving as wellas economic benefit.

Acknowledgement• The commitment of the project team isappreciated: Prof. Li yi, Song Qingwen at ITCin The Hong Kong PolyU, and• Prof. Zhang Yinping and his team at TsinghuaUniversity• RGC and ITF funding support

QUESTIONS ?