Analysis of modular composite heat pipes

Abstract

Thermal management requirements are becoming progressively more challenging as computing density increases due to the scaling down of electronic components. Improved thermal management schemes are necessary in power-dense systems to prevent thermal failure caused by excessive thermal cycling, optical misalignment, or exposure of instruments to environmental temperature extremes. To handle the extreme heat flux requirements of modern electronics (∼1 kW/cm2), two-phase heat transfer devices are used due to the high latent heat of phase change leading to well-managed temperature excursions during high heat dissipation events. To improve specific performance, manufacturing cost, and thermo-mechanical properties, we have developed a composite heat pipe model that utilizes differing materials for the adiabatic and evaporator/condenser sections. These composite heat pipes can be fabricated and installed for a fraction of the cost, while allowing for almost limitless customization, while maximizing specific heat transfer performance. We developed a comprehensive thermal-hydraulic model of the composite heat pipe performance that accounts for the pressure driven flow of the vaporized working fluid, the pressure drop over the length of the wick, and the thermal resistances governed by the wall, wick, liquid, and vapor. We used the model to show that the composite heat pipe has the potential for identical effective thermal conductivity when compared to its all metal counterpart, with drastic improvement (≈1000%) in specific performance. Furthermore, we use the model to perform sensitivity analysis and parametric multi-objective design optimization with respect to specific performance maximization and cost minimization. Our work not only presents a comprehensive model of composite heat pipe thermal-hydraulic performance, but offers a design platform for the development of next generation thermal dissipation devices that reduce cost and weight, and maximize manufacturability and implementation flexibility through modular design and integration schemes conducive to additive manufacturing techniques such as 3D printing.