1 / 35

Foreword

Foreword. Incorporation of a heat storage capability in the temperature control system of an electronic module having a variable heat dissipation rate will allow for a smaller, less-power-consuming module cooler and better temperature stabilization.

adamdaniel
Download Presentation

Foreword

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Foreword • Incorporation of a heat storage capability in the temperature control system of an electronic module having a variable heat dissipation rate will allow for a smaller, less-power-consuming module cooler and better temperature stabilization. • Materials formulated to undergo phase transition at key temperatures can provide this load-leveling capability via the latent heat effect.

  2. qout” qin” [w/cm2] 1 cm Heat Storage Surface 6% (Vol) Metalized PCM composite. qin = 6 W/cm2 qont = 3 W/cm2

  3. Objective Develop tools to evaluate the thermal response characteristics of hybrid coolers charged with phase change materials (PCM)

  4. Overview • Examples • PCM Options  “dry” PCM • Hybrid Cooler Design Concepts • Heat Transfer Performance Model • Model Calibration Experiments • Parametric Study of Cooler Response • Cooler Figure of Merit

  5. ExamplesofCurrentTechnology

  6. Wearable and Handheld Electronics

  7. PCM Options • Non-metallics have low thermal conductivity (thermal diffusivity). • S-L PCM’s  liquid containment problems (provision for volume expansion) • Salt Hydrates absorb water (they are also corrosive) • Metallics  mass penalty

  8. PCM Options • Solid - Solid Materials • Organic Compounds, Metallic Oxides, Encapsulated S-L PCM’s • Latent heat comparable to S-L PCM’s • Packaging is easier • Performance insensitive to cooler orientation or g-loading

  9. Solid - Solid PCM-based Heat Exchangers • Passive Heat Storage Mechanisms (all) • High-Performance (thermally conductive solids or high-heat-flux convection and radiation surfaces) through metalization. • Near Ambient Operating Temperatures, -30oC - +188oC (0oC - 100 oC). • Inexpensive Net-Shape Manufacture Resulting in Complex Heat Exchanger Shapes • Aerospace environment (operation is independent of ambient pressure or system orientation). • Heat exchangers that are Insensitive to Load Variations

  10. COOLANT C B A Heat Source Design Concepts“dry” PCM Hybrid Coolers A, C = Metalized Storage Volumes B = Heat Exchange Volume

  11. AIR FAN HEAT EXCHANGER METALIZED PCM q’’(t) Digital Electronics Application

  12. Electronics LRU

  13. SEM-E Module

  14. SEM-E FTM

  15. Hybrid Sem-E FTMSteady Performance Offset strip-fin vs hybrid (porous) design. P.R. = hybrid/offset Coolant = PAO. 6% (vol) Metalized PCM heat exchanger surface.

  16. Hybrid Sem-E Unsteady Load PAO flow rate = 2.5 #m/min Nominal load = 1000 watt Load factor = 1.5, Duty cycle = 30%

  17. Figure of Merit

  18. s H Hpcm D b W Prototype Hybrid Cooler 15 fins H = W = D  50 mm, Hpcm  25 mm ( 40 gm PCM) PCM: sp. gr.  1, htr  200 j/cc, Ttr  80- 90oC, Ttr  1- 8oC

  19. (UAs)n [T – Tamb] qn(t) s/2 t/2 Dx b Hpcm H 0 x m4 m5 m6 qn(t) Tamb m0 m1 m2 m3 Heat Transfer Model(half-fin model)

  20. DSC - Latent Heat

  21. Heat Transfer ModelPCM Heat Capacity

  22. Heat Transfer ModelCalibration • Hybrid Cooler • Base heater • Base Temperature measurement • Insulation (~ 3% loss) • Procedure • Steady State @ To Ttr • Establishes (UAs) • Record transient with q  qinit

  23. Digital Electronics Application Cont.

  24. Heat Transfer ModelCalibration Ttr = 83oC, Ttr = 6oC, q1/qinit= 2 C” = 45 watt/m2oC gives “best fit” of base temp. response.

  25. Parametric StudyStabilization/Recovery Times C” = 45 watt/m2oC, Ttr = 83oC, Ttr = 6oC q1/qinit = 1.5 q2/qinit = 0.5

  26. Parametric StudyHeating Rate C” = 45 watt/m2oC, Ttr = 83oC, Ttr = 6oC • Increase in q1/qinit results in: • increased operating temperature • decreased ts • little impact on tr

  27. Parametric StudyPCM Conductance Ttr = 83oC, Ttr = 6oC Increase in C” results in: reduced operating temperature relative to Ttr reduction in ts and tr

  28. Parametric StudyTransition Temp Interval C” = 45 watt/m2oC, Ttr = 83oC Increase in the transition temperature interval, Ttr results in poor temperature control.

  29. Dimensional AnalysisHeating “The temperature stabilization time (ts) is inversely proportional to the incremental change in input power: (q1-qinit) Dimensional Analysis: Where s is a characteristic of the system

  30. Dimensional AnalysisCooling “The temperature recovery time (tr) is inversely proportional to the decrement in input power below qinit, (q2-qinit) Dimensional Analysis: Where r is a characteristic of the system

  31. Hybrid Figure of Merit C” = 20 watt/m2oC, Ttr = 81oC, Ttr = 1oC s = r = 17 min The hybrid cooler’s figure of merit,  can (in principal) be measured with a single experiment.

  32. Conclusions • Incorporation of a “dry” PCM allows for a simple, rugged design. • A simple performance model based on lumped-mass elements contains essential system characteristics. • Semi-empirical • The transient response of the hybrid cooler can be characterized by 

More Related