75 research outputs found
Numerical Simulation of a Capillary Pulsating Heat Pipe in Various Gravity Conditions
In the last two decades a new concept of capillary heat pipe without wick structures, commonly known as Pulsating Heat Pipe (PHP), entered the domain of the two-phase passive heat transfer devices. The thermal-hydraulic behavior of this mini-channel with alternate heating and cooling zones, evacuated and partially filled with a working fluid, mainly depends on the interplay between phase change phenomena, capillary and gravity, if present, which may assist or damp the fluid motion. Numerous are the attempts to simulate PHPs complex behavior, but only a few of them are capable of complete thermal-hydraulic simulations; in addition, none is able to predict the effects of various gravity levels. Nevertheless, validated numerical simulations can constitute useful tools to complete and support experimental studies, and to help the design of new and better performing PHPs. Thus, a novel lumped parameters numerical code for the transient thermo-hydraulic simulation of PHPs has been developed and validated. It consists of a two-phase separated flow model where capillary slug flow is assumed a priori. A complete set of balance differential equations accounts for homogeneous and heterogeneous phase-changes, as well as thermal and fluid-dynamic phenomena. This novel model shows a very good quantitative and qualitative prediction capability not only when computing the correct measured equivalent thermal resistance, but even when reproducing the experimental trend of temperature when transient conditions are applied. This paper presents the comparison between numerical and experimental data, for a copper PHP (I.D./O.D. 1.1mm/2.0mm) filled with FC-72 tested experimentally in micro-gravity (58th Parabolic Flight Campaign), and hyper-gravity conditions (ESA SYT!2013 Programme
Towards a Numerical Simulation of a Closed Loop Pulsating Heat Pipe in Different Gravity Environments
Non equilibrium lumped parameter model for Pulsating Heat Pipes:validation in normal and hyper-gravity conditions
Effects of variable accelerations on a PHP-based cooling system
A PHP is a passive, wickless heat transfer device consisting of a capillary loop, evacuated and partially filled with a working fluid, with alternated heating and cooling zones. The PHP light structure (4kg/m2), flexibility and moderately high heat transfer capability (30W/cm2) are interesting for automotive cooling applications. During their motion, vehicles withstand different speeding-up, which may influence the PHP behavior. The braking and the turning accelerations are the most critical reaching over ±1g for passenger cars, more for sport cars. Therefore, numerical simulations have been carried out to analyze the performances of a stand-alone PHP-based cooling system under transient accelerations
Sensitivity Analysis of a Capillary Pulsating Heat Pipe: Influence of the Tube Characteristics
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