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Research Goals
Research Goals
Construct and prove a bench-scale experimental apparatus for testing evaporative cooling device performance, including characterizing selected membranes for evaporative cooling.
Experimental testing of prototyped nanoporous membrane evaporator under forced and passive loading of working fluid, and program thermocouple & pressure sensor data retrieval and analysis using Labview & NI DAQmx.
Develop computational models for evaluating device thermal performance.
Schematic of nanoporous membrane evaporator
Picture of nanoporous membrane evaporator
The nanoporous membrane evaporator functions passively by capillary forces
The nanoporous membrane evaporator functions passively by capillary forces
Small pores generate large capillary forces (~2γ/rpore) which can passively transport liquid over large distances
Thin liquid films within pores give high heat transfer coefficients
Evaporative cooling benefits from water’s high heat of vaporization
Work interrelated with MIT/BellLabs work on the DARPA's ICEOOL Project (> 1000 W/cm2)
Preliminary modeling and experimental testing of membrane prototype
Preliminary modeling and experimental testing of membrane prototype
Measured temperature changes for different configurations, including:
Calculating background loss to ambient (no fluid flow)
Determining heat dissipation with fluid flow (eg. Estimate cooling in terms of thermal resistance [C/W])
Comparison against numerical simulations:
Conduction model from copper block through silicon to nanoporous membrane
Membrane evaporation was modeled via heat transfer coefficient (h ~ 2 x 105 W/m2K at Tvapor = 50 oC):
q'' = h x (Tmem - Tvapor)
Preliminary experimental and simulation results are in semi-quantitative agreement
Proposed next steps to improve experimental apparatus
Proposed next steps to improve experimental apparatus
Installing pressure transducer upstream of the device to monitor inlet saturation conditions
Studying a wider range of flow rate conditions through bypass (ie. where low flow rates will mimic a passive system)
Testing at different evaporation (saturation) conditions for a more rigorous comparison to computational model
Modifying flow loop to implement passive technique relying solely on capillary forces, without pumping
Redesigning the experimental device to use a membrane material with greater thermal conductivity
Note: published information and released material is generally limited due to its propriety and confidential nature. The scientific and technical information disclosed has been approved for release by Bell Laboratories, Nokia (formerly Alcatel-Lucent, Bell Laboratories). Images courtesy of Bell Laboratories, Nokia.
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