Heat Transport Characteristics in a Miniature Flat Heat Pipe With Wire Core Wicks

Abstract

A mathematical model predicting the heat transport capability in a miniature flat heat pipe (FHP) with a wired wick structure was developed to analytically determine its maximum heat transport rate including the capillary limit. The effects of gravity on the profile of the thin-film-evaporation region and the distribution of the heat flux along a curved surface were investigated. The heat transfer characteristics of the thin-film evaporation on the curved surface were also analyzed and compared with that on a flat surface. Combining the analysis on the thin-film-condensation heat transfer in the condenser, the model can be used to predict the total temperature drop between the evaporator and condenser in the FHP. In order to verify the model, an experimental investigation was conducted. The theoretical results predicted by the model agree well with the experimental data for the heat transfer process occurring in the FHP with the wired wick structure. Results of the investigation will assist in the optimum design of the curved-surface wicks to enlarge the thin-film-evaporation region and a better understanding of heat transfer mechanisms in heat pipes.

Effects of superheat and temperature-dependent thermophysical properties on evaporating thin liquid films in microchannels

“…where K 1 is the curvature at the thicker end of the meniscus and L is the thin film length, which is determined by the cutoff condition [9,15,27] …”

“…Although Eq. (15) is actually only appropriate for non-polar liquids, many authors [6][7][8]16,19,23,27] have applied this equation to water films. Hence, the forces due to the dipole and induced dipole interactions for polar liquids are neglected in the present analysis [16].…”

“…Hence, the forces due to the dipole and induced dipole interactions for polar liquids are neglected in the present analysis [16]. Since the water is assumed to completely wet the wall, the dispersion constant is about 10 À19 J [8,27]. Combining Eqs.…”

Evaporation heat transfer characteristics of a grooved heat pipe with micro-trapezoidal grooves

“…When the heat load is low, there exist two thin film regions, i.e., C-C, D-D zones, and due to the groove symmetry, the C-C thin film region is the same as the D-D thin film region. But when the heat load reaches the maximum heat load, in which the thin film thickness of point B (d B ) is equal to d 0 , a new thin film region B-B [4,9] will be formed. Because there is no vapor-solid interface in the B-B thin film region, the contact angle in this region should be equal to zero.…”

“…Previous investigations [6,7] show that when the heat flux level added on the thin film region increases, the contact angle increases resulting in a decrease of the evaporating heat transfer coefficient, which presents a limitation of heat transport capability in a high heat flux heat pipe [8]. Recently, Jiao et al [9,10] developed a model focusing on the curved surface effect on the thin film profiles and heat flux distributions in the evaporator of a flat heat pipe.…”