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An OHP consists of a capillary sized tube and a refrigerant.

Oscillating (Pulsating) Heat Pipes. An OHP consists of a capillary sized tube and a refrigerant. Most OHPs are formed in closed serpentine loops with multiple turns, but OHPs can operate in other configurations Closed End (serpentine but not looped) Open End

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An OHP consists of a capillary sized tube and a refrigerant.

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  1. Oscillating (Pulsating) Heat Pipes • An OHP consists of a capillary sized tube and a refrigerant. • Most OHPs are formed in closed serpentine loops with multiple turns, but OHPs can operate in other configurations • Closed End (serpentine but not looped) • Open End • The tube is evacuated then partially filled with the working fluid • Capillary forces create a natural separation of liquid slugs and vapor plugs. Khandekar ‘04

  2. Operating Regimes Static Slug/Plug distribution, generation of small bubbles at high temps. similar to nucleate boiling Critical Heat Flux Oscillatory slug/plug flow develops in individual loops Heat flux ‘Stable’ oscillations develop, amplitudes increase with increasing heat flux, and oscillations in multiple tubes come into phase with one another -direction is arbitrary and periodically changes (more so with lower heat flux) -local oscillations superimposed on system oscillation Annular flow develops in fluid traveling from the evaporator to condenser • References • Khandekar, S., 2004, “Thermo-hydrodynamics of Closed Loop Pulsating Heat Pipes,” Institut fur Kernenergetik und EnergiesystemederUniversitat Stuttgart. • Ma., H. B., Borgmeyer, B., Cheng, P., Zhang, Y., 2008, “Heat Transport Capability in an Oscillating Heat Pipe,” Journal of Heat Transfer, 130(8), pp. 81501-1-7. • Borgmeyer, B., 2005, “Theoretical Analysis and Experimental Investigation of A Pulsating Heat Pipe for Electronics Cooling,” Master’s Thesis, University of Missouri-Columbia.

  3. Modeling • OHP modeling has focused on the “simpler” slug/plug flow regime • Multiple modeling approaches have been tried • Chaos • Continuity, Momentum & Energy • Spring-Mass-Damper • Non-Dimensional Analysis • Artificial Neural Networks • Our model has its roots in the spring-mass-damper models presented by Ma, Borgmeyer, et al.2,3 • EES/MATLAB based thermo-hydrodynamic model of an OHP operating in slug-plug flow. Evaporator Adiabatic Region Condenser . Q Tc Vapor Plug Liquid Slug

  4. The OHP Advantage and Project Goals • Advantages • OHPs are simpler/lighter than other two-phase heat transfer devices • No wick • No additional fluid reservoir • OHPs may be more robust? • Dry-out problems, while not extensively studied, do not appear to be a major problem…OHPs may be able to handle higher heat fluxes (convective heat transfer vs. phase change) • May be used as a thermal switch • Disadvantages • Lower effective conductance than Capillary Pumped Loops and Loop Heat Pipes Project Objective: Further the development of the technology/understanding required for successful implementation of an OHP in spacecraft thermal control applications. Approach: theoretical and experimental Deliverable: OHP design guidelines and a physics-based, but semi-empirical, model suitable for design

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