scholarly journals Hypergravity-assisted chemical liquid deposition of nano-granular film on the inner surface of a quartz tube

2018 ◽  
Vol 5 (9) ◽  
pp. 180722 ◽  
Author(s):  
Y. K. Shen ◽  
X. Q. He ◽  
X. Gu ◽  
Z. Liu ◽  
Z. H. He
Keyword(s):  
Flow Boiling ◽  
Cost Effective ◽  
Optical Transmittance ◽  
Deposition Process ◽  
Heating Process ◽  
Two Phase ◽  
Forming Mechanism ◽  
Chemical Liquid Deposition ◽  
Liquid Deposition ◽  
Quartz Tubes

Transparent tubes with functions of heating and temperature measurement are badly required in the visualization investigation of two-phase flows and flow-boiling heat transfer. In order to prepare such a tube, we introduced a cost-effective and energy-efficient procedure of hypergravity-assisted chemical liquid deposition (HACLD) to produce transparent and conductive silver (Ag) films on the inner surfaces of quartz tubes, typically 50 mm in length and 8 mm in inner diameter with a set-up that was designed and built for this purpose. Precursors of organometallic Ag precursor solutions were prepared by dissolving silver citrate and 1,2-diaminopropane in 2-methoxyethanol with required concentration for the chemical liquid deposition process. Semitransparent and conductive Ag films formed inside the required quartz tubes under specific heating process in hypergravity. One of the films was about 47 nm in thickness, 23 Ω per square sheet resistance, and 30% optical transmittance. This attempt may pave a way for the understanding of the film forming mechanism in hypergravity, and the development of a film preparation technology of HACLD.

A Cost-Effective Modeling Approach for Simulating Phase Change and Flow Boiling in Microchannels

2015 ◽  
Author(s):  
Zhenhai Pan ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Phase Change ◽  
Volume Fraction ◽  
Flow Boiling ◽  
Thin Liquid Film ◽  
Cost Effective ◽  
Source Terms ◽  
Time Step ◽  
Two Phase

High-fidelity simulation of flow boiling in microchannels remains a challenging problem, but the increasing interest in applications of microscale two-phase transport highlight its importance. In this paper, a volume of fluid (VOF)-based flow boiling model is proposed with computational expense-saving features that enable cost-effective simulation of two-phase flow and heat transfer in realistic geometries. The vapor and liquid phases are distinguished using a color function which represents the local volume fraction of the tracked phase. Mass conservation is satisfied by solving the transport equations for both phases with a finite-volume approach. In order to predict phase change at the liquid-vapor interface, evaporative heat and mass source terms are calculated using a novel, saturated-interface-volume phase change model that fixes the interface at the saturation temperature at each time step to achieve stability. Numerical oscillation of the evaporation source terms is thus eliminated and a non-iterative time advancement scheme can be adopted to reduce computational cost. The reference frame is set to move with the vapor slug to artificially increase the local velocity magnitude in the thin liquid film region in the relative frame, which reduces the influence of numerical errors resulting from calculation of the surface tension force, and thus suppresses the development of spurious currents. This allows use of non-uniform meshes that can efficiently resolve high-aspect-ratio geometries and flow features and significantly reduces the overall numerical expense. The proposed model is used to simulate the growth of a vapor bubble in a heated 2D axisymmetric microchannel. The bubble motion, bubble growth rate, liquid film thickness, and local heat transfer coefficient along the wall are compared against previous numerical studies.

Chemical liquid deposition process for microstructure fabrication

2005 ◽  
Vol 26 (8) ◽  
pp. 670-679 ◽  
Author(s):  
Jack G. Zhou ◽  
Anthony Addison ◽  
Zongyan He ◽  
Feng Wang
Keyword(s):  
Deposition Process ◽  
Microstructure Fabrication ◽  
Chemical Liquid Deposition ◽  
Liquid Deposition

Formation of Cf/C Composites with SiC Concentration Gradient on the Surface by SHCLD Technique

2007 ◽  
Vol 353-358 ◽  
pp. 1310-1313
Author(s):  
Guang Li Chen ◽  
Hao Ran Geng ◽  
Jun Hua Chen ◽  
Hui Li ◽  
Zhong Quan Guo
Keyword(s):  
Concentration Gradient ◽  
Deposition Process ◽  
Conventional Technique ◽  
Mechanical Tests ◽  
Gradient Layer ◽  
System Pressure ◽  
Chemical Liquid Deposition ◽  
Deposition Processes ◽  
Liquid Deposition ◽  
Different Thickness

Adopting two-step deposition processes, SiC concentration gradient layer on the surface of Cf/C composites were prepared via Self-heating Chemical Liquid Deposition (SHRCLD) technique. In second deposition process, carbon and SiC were codepositted from pure kerosene and TEOS. The temperature of deposition was 1000°C~1200°C and the system pressure was 0.1MPa. Different thickness of gradient layers would be attained via adjusting the proportion of TEOS in procurer and controlling deposition time. Oxidation resistance, and mechanical tests were investigated, and the microstructure was observed under SEM. Results showed that the flexural strength of the composites was 123.7 MPa. The antioxidation temperature of Cf/C composites with the gradient layer is up to 800°C in air. The process of SHCLD technique is simple and easy to be controlled, and the deposition rate is faster than other conventional technique.

scholarly journals Experimental Investigation and Prediction on Pressure Drop during Flow Boiling in Horizontal Microchannels

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 510
Author(s):  
Yan Huang ◽  
Bifen Shu ◽  
Shengnan Zhou ◽  
Qi Shi
Keyword(s):  
Pressure Drop ◽  
Flow Model ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Separated Flow ◽  
Heat Fluxes ◽  
Phase Flow ◽  
Vapor Quality ◽  
Two Phase ◽  
Gas Flux

In this paper, two-phase pressure drop data were obtained for boiling in horizontal rectangular microchannels with a hydraulic diameter of 0.55 mm for R-134a over mass velocities from 790 to 1122, heat fluxes from 0 to 31.08 kW/m2 and vapor qualities from 0 to 0.25. The experimental results show that the Chisholm parameter in the separated flow model relies heavily on the vapor quality, especially in the low vapor quality region (from 0 to 0.1), where the two-phase flow pattern is mainly bubbly and slug flow. Then, the measured pressure drop data are compared with those from six separated flow models. Based on the comparison result, the superficial gas flux is introduced in this paper to consider the comprehensive influence of mass velocity and vapor quality on two-phase flow pressure drop, and a new equation for the Chisholm parameter in the separated flow model is proposed as a function of the superficial gas flux . The mean absolute error (MAE ) of the new flow correlation is 16.82%, which is significantly lower than the other correlations. Moreover, the applicability of the new expression has been verified by the experimental data in other literatures.

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