Flow boiling instabilities in microchannels and their promising solutions – A review

Flow boiling enhancement of structured microchannels with micro pin fins

A review on flow boiling enhancement and fabrication of enhanced microchannels of microchannel heat sinks

The intensifying heat flux demands of concentrator photovoltaics requires innovation beyond conventional passive air cooling. Passive cooling is cost effective, reliable and does not consume power. Flat lens arrangements should allow large passive heat sinks to cool at solar concentrations of up to 2000 suns to 4000 suns (1 sun = 1000 W/m2). However, as solar concentrations increase so will the necessity of active cooling. The competitiveness of active cooling is enhanced by the capacity to harvest otherwise wasted thermal energy. Pairing with phase change materials presents an opportunity to stabilise the intermittent generation of solar thermal energy. Active microchannel cooling is a strong candidate for meeting the escalating heat flux demands of concentrator photovoltaics. For meeting short term-heat flux demands, established single phase microchannel cooling is most practical. Manifold microchannels yield superior performance to single layered microchannels, although they are more difficult to manufacture. For meeting long term heat flux demands, integration of boiling flows is promising. Jet impingement onto porous microstructures demonstrates effective mitigation of flow instabilities. Future studies should apply microchannel cooling directly to concentrator photovoltaics, particularly two-phase systems. They should also test microchannel cooling over larger heater areas and consider manufacturability of heat sinks. Novel directions should also be explored, such as alteration of typically rectangular and straight manifold microchannels or use of micro-valves to suppress boiling instabilities. Incipient cooling methods, including vortex shedding, ionic jet impingement, slug flow and shear driven gas flow, may also warrant further investigations.

Microchannel cooling of concentrator photovoltaics: A review

Effect of a micro heat sink geometric design on thermo-hydraulic performance: A review

Experimental study and optimization of pin fin shapes in flow boiling of micro pin fin heat sinks

A comparative study of flow boiling performance in reentrant copper microchannels and reentrant porous microchannels with multi-scale rough surface

The invention provides a panel heat pipe with an embedded porous wick and a manufacturing method thereof The panel heat pipe comprises an upper metal cover plate, a lower metal cover plate, and a closed cavity is formed between the upper metal cover plate and the lower metal cover plate in a welded and sealed mode The cavity is filled with liquid working media The inner surface of the cavity is divided into an evaporation face and a condensation face The condensation face and the evaporation face are paved with a thin-layer porous wick structure formed by sintering metal powder particles Sintering porous columns with inner grooves which are distributed in an array mode are machined on the evaporation face Porous protrusions matched with the inner grooves are machined in the condensation face The sintering porous columns and the porous protrusions are in close fit to form an embedded porous structure column A working medium backflow channel is formed in the embedded porous structure column According to the panel heat pipe, the capillary pressure is improved, the working medium backflow speed is remarkably increased, vapor-liquid two-phase separation is achieved, and the heat transfer performance is greatly improved; meanwhile, the embedded wick plays a supporting column role, and panel heat pipe inward sinking or crack deformation or other problems are effectively avoided

Panel heat pipe with embedded porous wick and manufacturing method thereof

The invention discloses a heat-tube composite liquid absorption core and a preparation method for the same. The heat-tube composite liquid absorption core is of a tubular structure, and comprises a metal outer sleeve and a metal porous flow channel, wherein the outer wall of the metal porous flow channel is in close fit with the inner wall of the metal outer sleeve; the metal porous flow channel is formed by carrying out solid-phase sintering on metal powder particles with particle sizes of 40-180 microns, the surface and the interior of the metal porous flow channel are provided with porous pore structures with an average pore diameter of 10-100 microns, and the inner wall surface of the metal porous flow channel is uniformly distributed with 20-60 liquid absorption grooves with lengths which are the same as the axial length of the metal porous flow channel along the peripheral direction thereof; each of the liquid absorption grooves comprises an embedded groove body and a slit, and the embedded groove body is communicated with the cavity of the metal porous flow channel through the slit. The heat-tube composite liquid absorption core disclosed by the invention is simple in manufacturing process and low in production cost, and capable of effectively making up the defects of a single groove or a sintering liquid absorption core, increasing a capillary pressure, reducing a liquid backflow resistance and increasing a permeability; meanwhile, the liquid absorption grooves are capable of effectively weakening the reverse shearing of steam flowing for liquid flowing, thus greatly improving the heat transfer performance of a heat tube.

Heat-tube composite liquid absorption core and preparation method for same

The utility model provides a flat heat pipe with an embedded type porous wick. The flat heat pipe includes an upper metal cover plate and a lower metal cover plate, wherein a closed cavity is formed between the upper and lower metal cover plates by welding, and the cavity is filled with liquid working medium; the inner surface of the cavity is divided into an evaporating surface and a condensing surface; thin porous wick structures formed by sintering metal powder particles are arranged on both the condensing surface and the evaporating surface, sintered porous columns with inward concave grooves and arranged in an array are formed in the evaporating surface, and porous bulges matched with the inward grooves are formed in the condensing surface; the porous bulges and the inward concave grooves are tightly fit to form an embedded type porous structure, and a working medium backflow channel is formed in the embedded type porous structure. The flat heat pipe improves capillary pressure, significantly picks up the backflow velocity of the working medium, achieves separation of gas phase and liquid phase, and greatly improves heat transfer performance; meanwhile, the embedded type porous wick plays a role of a support column, thus effectively avoiding the problems that the flat heat pipe sinks inward, cracks or deforms.

Zeng Tao

Papers

Experimental study and optimization of pin fin shapes in flow boiling of micro pin fin heat sinks

A comparative study of flow boiling performance in reentrant copper microchannels and reentrant porous microchannels with multi-scale rough surface

Panel heat pipe with embedded porous wick and manufacturing method thereof

Heat-tube composite liquid absorption core and preparation method for same

Flat heat pipe with embedded type porous wick