RT Journal Article
ID 273cd72b3a6d279c
A1 Gully, P. 
A1 Bonnet, F. 
A1 Nikolayev, Vadim S.
A1 Luchier, Nicolas
A1 Tran, T. Q. 
T1 EVALUATION OF THE VAPOR THERMODYNAMIC STATE IN PHP
JF Heat Pipe Science and Technology, An International Journal
JO HPST
YR 2014
FD 0000-00-00
VO 5
IS 1-4
SP 369
OP 376
K1 pulsating heat pipe
K1 vapor temperature measurement
AB Pulsating Heat Pipe (PHP) is a recently invented kind of thermal link of high thermal performance. The heat is transferred due to self-sustained oscillations of vapor bubbles and liquid plugs in a unique capillary tube which links the hot and cold sources in several turns or branches. Increasingly strong efforts are devoted to PHP simulation models which need to be experimentally assessed. Recent models show the importance of the thermodynamic state of the vapor bulk. Indeed it may deviate from the saturation
conditions due to vapor transient compression/expansion. This study aims at measuring and calculating the vapor state in a horizontal single branch PHP which allows generating oscillations of a liquid meniscus in a capillary tube with one open end, at which the pressure is imposed. The experimental setup uses oxygen at cryogenic temperatures which reduces as much as possible the radiation losses of both sensors (microscopic thermocouple) used for the direct vapor temperature measurement and of the whole PHP. We present here the simultaneous experimental measurements of the vapor pressure and temperature. The data are compared
to the theoretical modeling obtained within the film evaporation/condensation model of PHP [Das et al.,
2010]. The model is extended to account for the thermal gradient along and across the tube walls formed
because of the poor heat conductivity of its material. The vapor is found superheated, which demonstrates the
relevance of the model. The vapor temperature oscillates around the evaporator temperature. The heat transfer between the vapor and the dry evaporator wall explains this result. The corresponding heat transfer coefficient is calculated using DNS. The comparison shows an agreement between the experiment and the model.

PB Begell House
LK https://www.dl.begellhouse.com/journals/4b0844fc3a2ef17f,18c058f17ecbe0d2,273cd72b3a6d279c.html