Anomalously enhanced thermal performance of micro heat pipes coated with heterogeneous superwettable graphene nanostructures

Remarkable Thermal Performance Enhancement of Micro Heat Pipes with Graphene-Nanoplatelet Nano-Wicks

“…In Equation (2), is the applied heat load which is calculated based on the principle of energy conservation, whereby the heat dissipated from the condenser section is equal to the net heat transfer across the cooling device. The effective length is given by [ 7 , 29 ] and A c is the cross-sectional area of the microchannel.…”

“…Micro and nano-porous materials are commonly used to improve the surface wettability through methods such as sintering metal particles and nanoparticle deposition. Carbon nanomaterials such as graphene oxide (GO) [ 23 , 24 , 25 , 26 ], graphene nanoplatelets (GNPs) [ 19 , 20 , 21 , 27 , 28 , 29 ] and carbon nanotubes (CNTs) [ 30 , 31 , 32 , 33 , 34 ] are commonly used to improve the surface wettability. While the underlying principles are yet to be determined, the improved efficiency is generally attributed to the increase in heat-transfer surface area, improved surface wettability and capillary wicking due to the nanostructures [ 35 ].…”

“…The ultrafast water permeation property of graphene-based materials has been extensively utilized in various applications, such as desalination [ 36 , 37 , 38 , 39 ], nanofiltration [ 40 , 41 , 42 , 43 ] and phase-change heat transfer [ 9 , 15 , 29 ] systems. Among the carbon nanomaterials, the GNPs are found to exhibit the most superior ultrafast water permeation property [ 44 , 45 , 46 ].…”

“…While graphene nanostructures increase the heat-transfer surface area significantly, a larger nucleation site density, increased bubble frequency and smaller bubble diameter can be obtained. This ultrafast water transport property of graphene serves a dual purpose: enhancing the circulation rate of water via a nanocapillary effect and inducing the film-wise evaporation due to the formation of ultrathin water film [ 7 , 29 ].…”

“…By constructing the GNP nano-wicks in the MHP, the heat-transfer rate can be enhanced significantly as the GNPs encourage film-wise evaporation and water circulation due to its ultrafast water permeation property, as depicted in Figure 1 . While there are several studies highlighting the utilization of GNPs in conventional heat pipes [ 55 , 56 , 57 , 58 ], only a handful of studies have utilized this property of GNPs to enhance the thermal performance of MHPs by fully coating the microchannels with GNPs [ 7 , 29 ], achieving excellent enhancement. Most of these studies [ 56 , 57 , 58 ] applied the graphene-based nanofluids as working fluids in the heat pipes where the performance enhancement was not apparent as the enhancement is mainly dependent on the limited deposition of graphene nanoparticles on the pipe wall.…”