The present industry demand of high heat transfer capability, coupled with relatively cheap and increasingly small components, leads to the evolution of novel two-phase passive devices. Many ongoing efforts are devoted to satisfy the more and more severe requests of miniaturization coming especially from the electronic word. As relatively new and promising members of the wickless heat pipes family, the pulsating heat pipes, with their higher effective thermal conductivity with respect to the conventional two-phase devices, are the optimum candidate suitable for micro-scale cooling. The downsizing, however, could have various problems, principally linked to the associated high pressure drops, but a limited number of experiments are present in literature describing the performance of micro-PHP and none reports comparison between micro and standard PHPs. Therefore a novel one-dimensional lumped parameter numerical model for the transient thermo-hydraulic simulation of a PHP is proposed. It consists of a two-phase separated flow model applicable to a confined operating regime, meaning that capillary slug flow is assumed a priori. A complete set of balance differential equations accounts for thermal and fluid-dynamic phenomena. The originality of this numerical tool lays in the suppression of the standard assumption of saturated vapor plugs as well as in the consequent embedding of heterogeneous and homogeneous phase changes. The numerical tool has been verified by simulating the thermal-hydraulic behavior of a planar, copper tube PHP (I.D./O.D. 1.1mm/2.0mm) partially filled with FC-72 in modified gravity conditions (0g, 1g and 2g). This simulated configuration was tested experimentally both on ground (normal gravity), on the ESA-ESTEC Large Diameter Centrifuge (hyper-gravity) and during the 58th ESA parabolic flight campaign (micro-gravity). Comparisons with these operating conditions are provided. Moreover, simulations of a micro-PHP (I.D./O.D. 0.5mm/0.9mm) have been carried out for different gravity levels to predict the influence of such a small diameter on the whole PHP thermal performances.
Toward a design of a micro pulsating heat pipe
MAMELI, MAURO;FILIPPESCHI, SAURO;
2014-01-01
Abstract
The present industry demand of high heat transfer capability, coupled with relatively cheap and increasingly small components, leads to the evolution of novel two-phase passive devices. Many ongoing efforts are devoted to satisfy the more and more severe requests of miniaturization coming especially from the electronic word. As relatively new and promising members of the wickless heat pipes family, the pulsating heat pipes, with their higher effective thermal conductivity with respect to the conventional two-phase devices, are the optimum candidate suitable for micro-scale cooling. The downsizing, however, could have various problems, principally linked to the associated high pressure drops, but a limited number of experiments are present in literature describing the performance of micro-PHP and none reports comparison between micro and standard PHPs. Therefore a novel one-dimensional lumped parameter numerical model for the transient thermo-hydraulic simulation of a PHP is proposed. It consists of a two-phase separated flow model applicable to a confined operating regime, meaning that capillary slug flow is assumed a priori. A complete set of balance differential equations accounts for thermal and fluid-dynamic phenomena. The originality of this numerical tool lays in the suppression of the standard assumption of saturated vapor plugs as well as in the consequent embedding of heterogeneous and homogeneous phase changes. The numerical tool has been verified by simulating the thermal-hydraulic behavior of a planar, copper tube PHP (I.D./O.D. 1.1mm/2.0mm) partially filled with FC-72 in modified gravity conditions (0g, 1g and 2g). This simulated configuration was tested experimentally both on ground (normal gravity), on the ESA-ESTEC Large Diameter Centrifuge (hyper-gravity) and during the 58th ESA parabolic flight campaign (micro-gravity). Comparisons with these operating conditions are provided. Moreover, simulations of a micro-PHP (I.D./O.D. 0.5mm/0.9mm) have been carried out for different gravity levels to predict the influence of such a small diameter on the whole PHP thermal performances.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
