Comparative Study on Performance of Regenerator for Miniature Pulse Tube Cryocooler with Metal Matrix Materials at Ultra High Frequencies

A Miniature Pulse Tube Cryocooler (MPTC) is the first selection for the cooling of IR sensors, infrared detectors, etc. in space technology. The regenerator is one of the key components to operate an MPTC at high efficiency. The objective of this study is to explore the possibilities of the different matrices as regenerator filler materials for MPTC operating at ultra-high frequencies. REGEN 3.3 is one of the best software available for the design and optimization of cryocooler regenerators. We have used REGEN 3.3 for numerical simulations of the three different regenerator matrix materials viz. stainless steel wire mesh screen (SS 635#), brass wire mesh screen (500#) and copper wire mesh screen (500#) at the hot end and cold end temperatures of 300[Formula: see text]K and 80[Formula: see text]K for COP, cooling power, total power losses and pressure losses, at an ultra-high frequency of 100[Formula: see text]Hz and 200[Formula: see text]Hz. The simulation results depict that the regenerator using stainless steel mesh screen shows better results than that of the brass mesh screen and copper mesh screen at 100[Formula: see text]Hz. However, the performance of brass mesh screen and copper mesh screen performs better than the stainless steel at 200[Formula: see text]Hz. Therefore, the proposed matrix materials can be used as regenerator materials for the MPTC at ultra-high frequencies with better performances.

Preparation and Application of Superhydrophobic Copper Mesh by Chemical Etching and In-situ Growth

Oily sewage and floating oil in the ocean post a huge threat to the ecological environment, therefore, developing an efficient separation for oil/water mixtures is an urgent need. Currently, superhydrophobic materials exhibit excellent oil/water separation ability. In this study, a superhydrophobic copper mesh prepared by the chemical etching method and the in-situ growth method and the performance evaluation are introduced. The oxide layer on the surface of the copper mesh is first removed by pickling, and then immersed in FeCl3 solution for chemical etching to make the surface rough, stearic acid (SA) is used for in-situ growth to reduce the surface energy, a superhydrophobic oil-water separation copper mesh is obtained. The water contact angle (WCA) of the copper mesh is more than 160°. The copper mesh is chemically stable and can effectively adsorb floating oil and separate the oil-water mixture. After several oil-water separation experiments, the oil-water separation efficiency can still be above 98%. The effects of the concentration of FeCl3 and SA on the contact angle and oil-water separation efficiency are investigated, the results show that when the concentration of FeCl3 is 2% and SA is 1.5%, the WCA and oil-water separation efficiency are the largest. The research used a simple and environmentally friendly method to prepare the oil-water separation copper mesh, which has important application significance for water quality restoration.

Structured Copper Mesh for Efficient Oil-Water Separation Processed by Picosecond Laser Combined With Chemical Treatment or Thermal Oxidation

Oil-water separation has great practical significance, and can be used to help cope with growing oily industrial sewage discharge or marine oil spills, avoiding water pollution. Smart artificial super-wettable materials used for oil-water separation have aroused enormous interest because of their advantages of energy efficiency and applicability across a wide range of industrial processes. Herein, we report a highly efficient, simple method for oil-water separation using copper mesh fabricated by picosecond laser processing combined with chemical treatment or thermal oxidation. After laser processing, the surfaces of copper mesh show superhydrophilicity (hydrophilicity) and underwater superoleophobicity, which can be used to separate water from oil. While, for the samples after laser and chemical treatment or laser treatment combined with thermal oxidation, the surfaces become superhydrophobic (hydrophobic) and underwater superoleophilic, which can separate oil from water. Moreover, these three kinds of super-wettability meshes show high separation efficiency, achieving more than 99% seperation. Furthermore, the as-prepared mesh can be used for various oil-water mixture separation, such as edible oil, kerosene, diesel, and so on. Thus, this work will provide insights for controllable oil-water separation, and will also be beneficial to the study of microfluidic devices, and smart filters.

In Situ Fenton Triggered PDA Coating Copper Mesh with Underwater Superoleophobic Property for Oily Wastewater Pretreatment

The issue of oily wastewater treatment has become a worldwide challenge due to increasing industrial oily wastewater and frequent oil spill accidents. As an integral part of practical sewage treatment, pretreatment is conducted to remove inorganic particles, floating oil, and some emulsified oil, and to pave the way for post-treatment. Here, we report a facile fabricated, hydrostable, and rapid underwater-formed superoleophobic copper mesh with polydopamine (PDA) coating for efficient oily wastewater pre-treatment. Unlike with traditional technologies, using the interface phenomenon to solve the problem of oil/water mixture separation provided a new approach for the low energy input pretreatment process. The PDA coating formed by the in situ Fenton method not only rapidly constructs a protection layer for the etched hierarchical micro-size particles on mesh and results in enhanced hydrophilicity, but also exhibits high uniformity and enhanced stability in acid/alkali medium. Benefiting from the above processes, a very high flux of 25 L m−2 s−1 and high separation efficiency of 99.0% toward various oil/water mixtures were achieved, revealing excellent prospects for practical usage. Therefore, this new approach offered insight into the development of a cost-effective and functional method for efficient pretreatment of oily wastewater.