Thermal Characterisation of Micro Flat Aluminium Heat Pipe Arrays by Varying Working Fluid and Inclination Angle

Abstract

Featured Application: solar collector; solar thermal system; thermal energy storage system; heat exchanger.Abstract: A micro heat pipe array is desirable owing to its high heat transfer capacity, compact size, and high surface-volume ratio compared with conventional heat pipes. In this study, micro flat aluminium heat pipe arrays (MF-AHPA) were developed and systematically characterised by varying working fluid and inclination angle. Three MF-AHPAs with different working fluids, i.e., acetone, cyclopentane, and n-hexane, were fabricated. The acetone MF-AHPA achieved the best thermal performance. The underlying mechanism is the small flow viscous friction and small shearing force of liquid vapour. Additionally, the experimental results show a strong dependence of MF-AHPAs' thermal resistance on the orientation due to the gravitational effect on axial liquid distribution. Finally, a criterion is proposed to determine the optimal inclination angle of the MF-AHPA. In the present study, a volumetric fraction (α a,c ) of 74 ± 7% has been shown to well predict an optimal inclination angle of the MF-AHPAs with various working fluids and heat loads.

Gradient-Pattern Micro-Grooved Wicks Fabricated by the Ultraviolet Nanosecond Laser Method and Their Enhanced Capillary Performance

“…The high aspect ratio is attributed to the extremely high energy density of the laser (25.46 J/cm 2 ). As a result, the depth-to-width ratio of the grooves fabricated in this study (~3.4 in Figure 4 a) is significantly greater than that of the grooves produced through traditional extrusion molding (~1.28) [ 41 ] or high-speed spinning methods (~1.25) [ 42 ]. From another point of view, the laser-caused material addition method (such as laser-induced electrodeposition) [ 43 ] is an effective way to enhance surface capillary performance.…”

Sustainable dropwise condensation enabled ultraefficient heat pipes

“…In inclined groove-structured heat pipes, the thickness of the liquid film developed in the adiabatic region could reach ~50 μm. [30][31][32] This liquid film could insulate the vapor flow from direct contact with the metal surface and hence, affect the measurement of the outside surface temperature. The temperature derived for the vapor would be less than the assumed vapor temperature inside the heat pipe, leading to an overpredicted R e .…”

“…In the 1D model, we assumed there was no heat exchange through the wall in the adiabatic region, and the measured wall temperature was equal to the saturated steam temperature inside the heat pipe. In inclined groove‐structured heat pipes, the thickness of the liquid film developed in the adiabatic region could reach $$\unicode{x0007E}$$50 $${\rm{\mu }}\phantom{\rule{}{0ex}}{\rm{m}}$$ 30–32 . This liquid film could insulate the vapor flow from direct contact with the metal surface and hence, affect the measurement of the outside surface temperature.…”

Design and Thermal Performance of Ultra-Thin Flat Plate Heat Pipes with Composite Wick for Electronic Cooling

“…The flat plate heat pipe (FPHP) is a potential heat transfer device due to its excellent thermal performance and reliability [2] . It has been widely used in communication products, spacecraft, and industrial products to eliminate local hot spots and provide temperature uniformity [3,4] . However, the new generation of consumer electronics with lighter and thinner designs leaves a narrow space for thermal control components [5] .…”