dry-outs two different kinds can occur in gravity-assist heat pipes with capillary flow. An exess of hydrostatic driving force can lead to a receding of the menisci into the capillary structure and an 'azimuthal dry-out' characterized by a concentration of the circumference of the heat pipe. The azimuthal dry-out most likely occurs during start-up and disappears at higher heat fluxes. It can be prevented by using a graded capillary structure or a homogeneous capillary structure with a static capillary rise, which exeeds the highest point of the evaporator. A lack of hydrostatic driving force, on the other hand, leads to an 'axial dryout', which is characterized by a lack of axial liquid pool at the bottom, the reaching of the axial dry-out limit in the capillary flow mode will manifest itself as the beginning of a pool transfer and an eventual transition to a new stationary state with mixed capillary- and free flow. The basic equation for the axial dry-out is derived and resoved for a simple case. The role of inertia forces and entrainment is pointed out.
The dry-out limits of gravity- assist heat pipes with capillary flow
Austrocknungsgrenze fuer schwerkraftbetriebene Waermeleitrohre mit Kapillarstroemung
1978
8 Seiten, 5 Bilder, 8 Quellen
Conference paper
English
Entrainment limits in heat pipes
AIAA | 1978
|Entrainment Limits in Heat Pipes
AIAA | 1979
|