Spreading and evaporation of droplets at their free falling on a heated copper surface

With an increase in the productivity of power equipment and the miniaturization of its components, the use of traditional thermal management systems becomes insufficient. There is a need to develop drip heat removal systems, based on phase transition effects. Cooling with small volumes of liquids is a promising technology for microfluidic devices or evaporation chambers, which are self-regulating systems isolated from the external environment. However, the heat removal during evaporation of droplets into a limited volume is a difficult task due to the temperature difference in the cooling device and the concentration of water vapor that is unsteady in time depending on the mass of the evaporated liquid. This paper presents the results of an experimental study of the distilled water microdrops’ (5-25 μl) evaporation on an aluminum alloy AMg6 with the temperatures of 298-353 K in an isolated chamber (70 × 70 × 30 mm3) in the presence of heat supply to its lower part. Based on the analysis of shadow images, the changes in the geometric dimensions of evaporating drops were established. They included the increase in the contact diameter, engagement of the contact line due to nano roughening and chemical composition inhomogeneous on the surface (90-95% of the total evaporation time) of the alloy and a decrease in the contact diameter. The surface temperature and droplet volume did not affect the sequence of changes in the geometric dimensions of the droplets. It was found that the droplet volume has a significant effect on the evaporation time at relatively low substrate temperatures. The results of the analysis of droplet evaporation rates and hygrometer readings have shown that reservoirs with salt solutions can be used in isolated chambers to control the concentration of water vapor. The water droplets evaporation time was determined. The analysis of the time dependences of the evaporation rate has revealed that upon the evaporation of droplets in an isolated chamber under the conditions of the present experiment, the air was not saturated with water vapor. The latter did not affect the evaporation rate.

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Self-assembled monolayers of novel imidazole derivative on copper surface for anticorrosion protection in neutral medium

Journal of Adhesion Science and Technology ◽

10.1080/01694243.2021.1895571 ◽

2021 ◽

pp. 1-22

Author(s):

Periyasamy Durainatarajan ◽

Mallaiah Prabakaran ◽

Subbaratnam Ramesh

Keyword(s):

Copper Surface ◽

Imidazole Derivative ◽

Self Assembled Monolayers ◽

Neutral Medium ◽

Anticorrosion Protection ◽

Assembled Monolayers ◽

Self Assembled

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Multi-Camera Based Setup for Geometrical Measurement of Free-Falling Molten Glass Gob

Sensors ◽

10.3390/s21041041 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1041

Author(s):

Mazhar Hussain ◽

Mattias O’Nils ◽

Jan Lundgren

Keyword(s):

Free Fall ◽

Frame Rate ◽

Geometrical Parameters ◽

Contactless Method ◽

Molten Material ◽

Dynamic Changes ◽

Direct Measurements ◽

Molten Materials ◽

Free Falling

High temperatures complicate the direct measurements needed for continuous characterization of the properties of molten materials such as glass. However, the assumption that geometrical changes when the molten material is in free-fall can be correlated with material characteristics such as viscosity opens the door to a highly accurate contactless method characterizing small dynamic changes. This paper proposes multi-camera setup to achieve accuracy close to the segmentation error associated with the resolution of the images. The experimental setup presented shows that the geometrical parameters can be characterized dynamically through the whole free-fall process at a frame rate of 600 frames per second. The results achieved show the proposed multi-camera setup is suitable for estimating the length of free-falling molten objects.

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Improved Copper–Epoxy Adhesion by Laser Micro- and Nano-Structuring of Copper Surface for Thermal Applications

Polymers ◽

10.3390/polym13111721 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1721

Author(s):

Mario Mora ◽

Hippolyte Amaveda ◽

Luis Porta-Velilla ◽

Germán F. de la Fuente ◽

Elena Martínez ◽

...

Keyword(s):

Thermal Conductivity ◽

Bonding Strength ◽

Copper Surface ◽

Heat Sinks ◽

Electrical Insulation ◽

Cryogenic Temperatures ◽

Shear Tests ◽

Patterned Structures ◽

Different Temperatures ◽

Mechanical Tensile

The objective of this work is the enhancement of metal-to-metal bonding to provide high thermal conductivity together with electrical insulation, to be used as heat sinks at room and cryogenic temperatures. High thermal conductive metal (copper) and epoxy resin (Stycast 2850FT) were used in this study, with the latter also providing the required electrical insulation. The copper surface was irradiated with laser to induce micro- and nano-patterned structures that result in an improvement of the adhesion between the epoxy and the copper. Thus, copper-to-copper bonding strength was characterized by means of mechanical tensile shear tests. The effect of the laser processing on the thermal conductivity properties of the Cu/epoxy/Cu joint at different temperatures, from 10 to 300 K, is also reported. Using adequate laser parameters, it is possible to obtain high bonding strength values limited by cohesive epoxy fracture, together with good thermal conductivity at ambient and cryogenic temperatures.

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