Caihua Liang

Sprayable superhydrophobic nano-chains coating with continuous self-jumping of dew and melting frost

Spontaneous movement of condensed matter provides a new insight to efficiently improve condensation heat transfer on superhydrophobic surface. However, very few reports have shown the jumping behaviors on the sprayable superhydrophobic coatings. Here, we developed a sprayable silica nano-porous coating assembled by fluorinated nano-chains to survey the condensates’ dynamics. The dewdrops were continuously removed by self- and/or trigger-propelling motion due to abundant nano-pores from random multilayer stacking of nano-chains. In comparison, the dewdrops just could be slipped under the gravity effect on lack of nano-pores coatings stacked by silica nano-spheres and nano-aggregates. More interestingly, the spontaneous jumping effect also occurred on micro-scale frost crystals under the defrosting process on nano-chains coating surfaces. Different from self-jumping of dewdrops motion, the propelling force of frost crystals were provided by a sudden increase of the pressure under the frost crystal.

Frosting Behavior of Superhydrophobic Nanoarrays under Ultralow Temperature

Retarding and preventing frost formation at ultralow temperature has an increasing importance due to a wide range of applications of ultralow fluids in aerospace and industrial facilities. Recent efforts for developing antifrosting surfaces have been mostly devoted to utilizing lotus-leaf-inspired superhydrophobic surfaces. Whether the antifrosting performance of the superhydrophobic surface is still effective under ultralow temperature has not been elucidated clearly. Here, we investigated the frosting behavior of fabricated superhydrophobic ZnO nanoarrays under different temperature and different environment. The surface showed excellent performance in anticondensation and antifrosting when the surface temperature was approximately -20 °C. Although the frosting event inevitably occurs on all surfaces when the temperature is decreased from -50 to -150 °C, the frost accumulation on the superhydrophobic surfaces is always less than that on the untreated surfaces. Interestingly, the frost layer detaches from the surface within a short time and keeps the surface dry in the very beginning of the defrosting process. Further, there is no frost formation on the surface at -20 °C during 10 min testing when blowing compressed air and spraying methanol together or spraying methanol individually. It can reduce the height of the frost layer and increases the density when spraying methanol at -150 °C. Furthermore, the frost crystals on the top surface can been blown away due to the low adhesion of ice or frost. It provides a basic idea for solving the frosting problem under ultralow temperature while combined with other defrosting methods.

Influence of Blocking Flow on Flow Characteristic of Electronic Expansion Valve

We study series of flow regime of the refrigerant in electronic expansion valve and make analysis on the flash evaporation and the cavitation erosion phenomenon. Our result shows that the flow of refrigerant in electronic expansion valve is blocking flow. We present the influence of blocking flow on flow rate characteristic of electronic expansion valve and analyze the flow characteristic. We developed a sample machine to conduct some experiments on the valve under the experimental working condition, and the results of the experiments shows that the particular flow rate characteristic of the electronic expansion valve under experimental condition, and found the flow is blocking flow. We present the curves of the flow rate versus the open degree of the valve. The curves expose that there is a linear relationship between the flow rate and the open degree of the valve if the open degree is under a certain value. When the open degree is above this value, it will not present the linear relationship any longer,...