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Richard Wirtz, Shuo Peng and Alan Fuchs Mechanical Engineering Department

A POLYMER BASED THERMAL ENERGY STORAGE COMPOSITE FOR TEMPERATURE CONTROL OF SENSORS AND ELECTRONICS TED-AJ03-359. Richard Wirtz, Shuo Peng and Alan Fuchs Mechanical Engineering Department University of Nevada, Reno March 17, 2003 Research sponsored by Intel Corp

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Richard Wirtz, Shuo Peng and Alan Fuchs Mechanical Engineering Department

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  1. A POLYMER BASED THERMAL ENERGY STORAGE COMPOSITE FOR TEMPERATURE CONTROL OF SENSORS AND ELECTRONICSTED-AJ03-359 Richard Wirtz, Shuo Peng and Alan Fuchs Mechanical Engineering Department University of Nevada, Reno March 17, 2003 Research sponsored by Intel Corp Systems Technology, Hillsboro OR AJTEC 2003

  2. MOTIVATION • Heat storage via phase transition is an effective temperature control strategy • Variable power or on/off systems • Short duration missions • Dry PCM TES-system • Operation is g-load & orientation insensitive • Simple packaging • Solid/Liquid PCM + immobilizating agent Dry PCM • SEBS/paraffin AJTEC 2003

  3. OUTLINE SEBS/Paraffin TES Composite • Formulation • Hermeticity & Stability • Thermophysical Properties Implementation as TES-system • Laminate Structures • Thermal Response Modeling • Benchmark Experiments AJTEC 2003

  4. DRY PHASE CHANGE MATERIAL ALTERNATIVES • Solid state transition • Pentaglycerine/neopentaglycol • S/L PCM encapsulation • Microencapsulated paraffin • S/L PCM + immobilization agent • Paraffin + SEBS SEBS = styrene ethylene butadiene styrene block copolymer AJTEC 2003

  5. 63mm square x 2mm thick SEBS/paraffin TES composite on 1mm aluminum heat spreader plate. The sample has an approximate 1000 joule capacity. PARAFFIN/SEBS COMPOSITE FORMULATION • SEBS pellets melted into molten paraffin under N2 • Cast in mold • Solidified samples coated via dipping in 50/50 SEBS/toluene solution AJTEC 2003

  6. 20% SEBS 50% SEBS PARAFFIN/SEBS COMPOSITE: HERMITICITY SEBS/n-hexacosane (tech grade), Ttr = 58C Gravimetric testing: 2200 hrs at 80C with no significant mass loss (TSEBS,tr = 120C ) AJTEC 2003

  7. 50% SEBS 20% SEBS PARAFFIN/SEBS COMPOSITE: STABILITY Thex,tr = 58C, TSEBS,tr = 120C Phase transition volume expansion = 13% Some paraffin leakage observed after 360 (40C-80C-40C) cycles AJTEC 2003

  8. PARAFFIN/SEBS COMPOSITE PROPERTIES hv,  measured [Peng, 2003] AJTEC 2003

  9. ro Thermal Interface 4q1 ts+ tc 2P Spreader Plate TES Volume LAMINATE STRUCTURE: CONFIGURATION I • Components • TES-volume • Heat spreader plates • Thermal Interfaces (TI) linked to electronics 4 laminates shown Physical model: heat conducted from the TI radially outward along heat spreader plates and then in z to TES-volume AJTEC 2003

  10. Thermal Interface 2to TI Fin Spreader Plate 4q1 tc+ ts TES Volume 2P LAMINATE STRUCTURE: CONFIGURATION II Physical model: heat conducted along the TI-fin, then radially inward in the plane of the heat spreader plates and then in  z direction to TES-volume AJTEC 2003

  11. q1 Rk = 1 Spreader Plate TES Volume Rk = 370 Red: T > Tt Blue: T < Tt THERMAL RESPONSE: PHYSICAL MODEL Finite element solution of transient phase transition interface. Configuration II • Rkr << 1 • TI  PCM, No spreader plate functionality • Rkr >> 1 • TI  Plates  PCM AJTEC 2003

  12. re ro q1 ts r Ts(r,) Tt tc (r,) z THERMAL RESPONSE MODELRKR >> 1 Configuration I Centrally located TI of radius ro, Annular disk heat spreader plate of thickness ts, and outer radius re Annular disk TES-composite of thickness tc, and volumetric latent heat hv. Assumptions () only: heat flow in the conductive disk is 1-D transient (r-direction); heat flow in the paraffin-disk is 1-D transient (z-direction). Sensible heat capacity is negligible compared to the latent heat capacity of the paraffin-disk. AJTEC 2003

  13. Configuration II Configuration I 1   0.5 0 0 0.5 1 0 0.5 1 r/re r/re /ref 0.5 0.1 1.0 UNIFORM : HEAT SPREADER TEMP DIST • Configuration II: Better thermal control? • Temperature distribution more uniform • T-grad at TI smaller AJTEC 2003

  14. tc/P=0.1 to/P = ro/P=0.1 Solid – Config. I Dash – Config. II 0.008 Rk = 50 Rk = 100 0.004 Rk = 300 0 0 0.2 0.4 0.6 0.8 1 TI TEMP.RESPONSE . • TI TEMPERATURE RESPONSE IS  EQUAL • Config I: small peripheral surface area • Config II: T-drop in TI-fin AJTEC 2003

  15. T - Tt [C] THERMAL RESPONSE MODEL VERIFICATION Z Rkr = 114 R Foil heater Copper dish 80/20 Paraffin/SEBS composite AJTEC 2003

  16. Spreader edge Spreader ctr. Composite (z = tc) r = 2.5” r = 2.0” r = 1.0” r = 0 Red – Vertical Blk - Horizontal T-Ttr [ºC] Time [sec] Vertical and horizontal orientation temperature response. EFFECT OF ORIENTATION ON THERMAL RESPONSE NEGLIGIBLE EFFECT AT 1-G AJTEC 2003

  17. CONCLUSIONS • SEBS/Paraffin Composite • SEBS immobilizes liquid paraffin (1-g) • SEBS coating is hermetic • Low cycle stability, O(300) • Accommodates transition sp. volume change (13%) • Hydrophobicity mechanism • Large Rk transient response model • Benchmarked • TES-system laminate configuration • Config I & II: essentially equivalent AJTEC 2003

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