@Article{BertoldoJrVlasGenaGued:2015:DyTeMe,
author = "Bertoldo Junior, Jorge and Vlassov, Valeri Vladimirovich and
Genaro, Gino and Guedes, Ulisses Thadeu Vieira",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and {Instituto Nacional de Pesquisas
Espaciais (INPE)}",
title = "Dynamic test method to determine the capillary limit of axially
grooved heat pipes",
journal = "Experimental Thermal and Fluid Science",
year = "2015",
volume = "60",
pages = "290--298",
keywords = "Dynamic test method, capillary limit, axially grooved heat pipe.",
abstract = "The usual experimental method to detect heat pipe capillary limit
under different inclinations includes submitting the pipe to a
certain tilt and increasing the heat load at the evaporator zone
until a sudden rise in temperature at this region (dry out) is
observed. According to this method, for each heat load dwell
imposed to the pipe, either the dry out phenomenon is detected or
steady state temperature is achieved. The complete test is time
consuming and the precision of the heat load detection needed to
induce the dry out depends on the power step utilized. In
addition, sometimes the dry out is difficult to detect accurately
in axially grooved heat pipes due to the fact of the liquid phase
is distributed in a non-homogeneous way at the evaporator zone. In
fact, the grooves at the top of the heat pipe tend to dry faster.
At the lower grooves of the evaporator forms a buildup of working
fluid (puddle) due to gravitational effects and thus needing a
higher heat flux to cause the drying. The dynamic method proposed
in this paper to detect dry out in heat pipes consists in applying
a given heat load on the heat pipe, which is initially kept in a
horizontal position on a rotary table equipped with motor with
reducer gearbox and digital inclinometer. After steady state is
reached on the heat pipe, which is leveled horizontally, the table
is driven causing the pipe to adverse tilt slowly until the dry
out occurs. Once dry out initiates, the axial gravity force
component, which is permanently increasing due to table rotation,
provokes the liquid phase accelerated retreating from the
evaporator, including the puddle liquid excess. It assists the
fast overheating onset in the dried zone that in its turn allows a
very clear detection of the dry out event by a temperature sensor.
The pipe is then placed back in the horizontal position. The
proposed test method besides requiring less time to obtain the
capillary limit curve, permits to detect in a more precision way
the exact time when the dry out occurs. The capillary limits
obtained from this method were compared against those obtained
from conventional methods for ammonia two-core axially-grooved
heat pipe. The results show that dynamic test method can be
adopted as an effective alternative to determine capillary limit
for axially grooved heat pipes.",
doi = "10.1016/j.expthermflusci.2014.10.002",
url = "http://dx.doi.org/10.1016/j.expthermflusci.2014.10.002",
issn = "0894-1777",
language = "en",
targetfile = "dynamic test.pdf",
urlaccessdate = "04 maio 2024"
}