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Full-Text Articles in Mechanical Engineering

Mushy Zone Equilibrium Solidification Of A Semitransparent Layer Subject To Radiative And Convective Cooling, Chengcai Yao, Benjamin Chung, Guo-Xiang Wang May 2015

Mushy Zone Equilibrium Solidification Of A Semitransparent Layer Subject To Radiative And Convective Cooling, Chengcai Yao, Benjamin Chung, Guo-Xiang Wang

Dr. Guo-Xiang Wang

Equilibrium solidification in a semitransparent planar layer is studied using an isothermal mushy zone model. The layer is made up of a pure material being emitting, absorbing and isotropically scattering and is subject to radiative and convective cooling. The model involves solving simultaneously the transient energy equation and the radiation transport equation. An implicit finite volume scheme is employed to solve the energy equation, with the discrete ordinate method being used to deal with the radiation transport. A systematical parametric study is performed and the effects of various materials optical properties and processing conditions are investigated. It is found that ...


Effects Of Particle's Off-Axis Position, Shape, Orientation And Entry Position On Resistance Changes Of Micro Coulter Counting Devices, Zhenpeng Qin, Jiang Zhe, Guo-Xiang Wang Apr 2015

Effects Of Particle's Off-Axis Position, Shape, Orientation And Entry Position On Resistance Changes Of Micro Coulter Counting Devices, Zhenpeng Qin, Jiang Zhe, Guo-Xiang Wang

Dr. Guo-Xiang Wang

With the recent advance in micro/nano-fabrication technology, micro Coulter counters have been widely used in detecting and characterizing micro- and nanoscale objects. In this paper, the electrical resistance change during translocation of a non-conducting particle through a channel is studied numerically. The numerical results are validated by proven analytical results available in the literature. The effects of particle's off-axis position, shape and orientation, and entry position are studied for particles with a large dynamic range. From the numerical results, a new fitted correlation is proposed that can accurately predict the resistance change caused by off-axis spherical particles regardless ...


A Two-Temperature Model For Selective Photothermolysis Laser Treatment Of Port Wine Stains, D. Li, Guo-Xiang Wang, Y. He, K. Kelly, W. Wu, Y. Wang, Z. Ying Apr 2015

A Two-Temperature Model For Selective Photothermolysis Laser Treatment Of Port Wine Stains, D. Li, Guo-Xiang Wang, Y. He, K. Kelly, W. Wu, Y. Wang, Z. Ying

Dr. Guo-Xiang Wang

Selective photothermolysis is the basic principle for laser treatment of vascular malformations such as port wine stain birthmarks (PWS). During cutaneous laser surgery, blood inside blood vessels is heated due to selective absorption of laser energy, while the surrounding normal tissue is spared. As a result, the blood and the surrounding tissue experience a local thermodynamic non-equilibrium condition. Traditionally, the PWS laser treatment process was simulated by a discrete-blood-vessel model that simplifies blood vessels into parallel cylinders buried in a multi-layer skin model. In this paper, PWS skin is treated as a porous medium made of tissue matrix and blood ...


Rapid Transient Explosive Boiling Of Binary Mixture Under Pulsed-Laser Irradiation, Xiu-Lan Huai, Dengying Liu, Zhaoyi Dong, Renxi Jin, Guo-Xiang Wang Apr 2015

Rapid Transient Explosive Boiling Of Binary Mixture Under Pulsed-Laser Irradiation, Xiu-Lan Huai, Dengying Liu, Zhaoyi Dong, Renxi Jin, Guo-Xiang Wang

Dr. Guo-Xiang Wang

Rapid transient explosive boiling of mixed ethanol and acetone of different volume fractions were investigated experimentally. The temperature of the metal film surface irradiated by a pulse laser was measured by a fast-response measurement system with a platinum film resistor. The behaviors of bubbles, including their formation, growth, departure and floating-up, were observed and captured by a microscope camera system. It was found that bubble nucleation temperature depends strongly on the heating rate. Some special characteristics different from those of conventional boiling were revealed, and the factors affecting explosive boiling were studied.


Heat-Transfer Dynamics During Cryogen Spray Cooling Of Substrate At Different Initial Temperatures, Jia Wangcun, Aguilar Guillermo, Guo-Xiang Wang, Nelson Stewart Apr 2015

Heat-Transfer Dynamics During Cryogen Spray Cooling Of Substrate At Different Initial Temperatures, Jia Wangcun, Aguilar Guillermo, Guo-Xiang Wang, Nelson Stewart

Dr. Guo-Xiang Wang

Cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during laser dermatologic therapy. However, the dominant mechanisms of heat transfer during the transient cooling process are incompletely understood. The objective of this study is to elucidate the physics of CSC by measuring the effect of initial substrate temperature (T0) on cooling dynamics. Cryogen was delivered by a straight-tube nozzle onto a skin phantom. A fast-response thermocouple was used to record the phantom temperature changes before, during and after the cryogen spray. Surface heat fluxes (q'') and heat-transfer coefficients (h) were computed using an inverse heat conduction ...


Effect Of Spurt Duration On The Heat Transfer Dynamics During Cryogen Spray Cooling, Aguilar Guillermo, Guo-Xiang Wang, J. Nelson Apr 2015

Effect Of Spurt Duration On The Heat Transfer Dynamics During Cryogen Spray Cooling, Aguilar Guillermo, Guo-Xiang Wang, J. Nelson

Dr. Guo-Xiang Wang

Although cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during laser dermatologic surgery, optimization of the current cooling approach is needed to permit the safe use of higher light doses, which should improve the therapeutic outcome in many patients. The objective of this study was to measure the effect of spurt duration (Δt) on the heat transfer dynamics during CSC using a model skin phantom. A fast-response temperature sensor was constructed to record the changes in surface temperature during CSC. Temperature measurements as a function of Δt at two nozzle-to-skin distances (z = 50 and 20 ...


Multi-Phase Flow And Heat Transfer Of A Micro-Pump Thermally Driven By A Multi-Output Pulse Laser, Xiu-Lan Huai, Zhi-Wei Tang, Guo-Xiang Wang Apr 2015

Multi-Phase Flow And Heat Transfer Of A Micro-Pump Thermally Driven By A Multi-Output Pulse Laser, Xiu-Lan Huai, Zhi-Wei Tang, Guo-Xiang Wang

Dr. Guo-Xiang Wang

We present an experimental study of multi-phase flow and heat transfer in a micro-tube induced by a multi-output pulse laser. Extensive flow and heat transfer measurements and visualization experiments have been carried out to characterize the micro-pump behaviour under various conditions. The experiments reveal extremely unsteady and complex flow patterns in the micro tube with the flow closely related with generation and collapse of bubbles. It is found that the flow rates are controlled by the heating and condensation conditions within the tube. The laser pulse duration, pulse interval and output-power as well as the tube diameter all show a ...


Microscopic Explosive Boiling Induced By A Pulsed-Laser Irradiation, Xiulan Huai, Guo-Xiang Wang, Renxi Jin, Tienan Yin, Yu Zou Apr 2015

Microscopic Explosive Boiling Induced By A Pulsed-Laser Irradiation, Xiulan Huai, Guo-Xiang Wang, Renxi Jin, Tienan Yin, Yu Zou

Dr. Guo-Xiang Wang

This paper presents an experimental study of microscopic explosive boiling introduced by a pulsed laser. The violent explosive boiling was observed in the liquid film, and the vapor bubbles together with liquid droplets were expelled from the platinum film. It is found that the apparent bubble nucleation temperature is a strong function of the heating rate. The pressure signal appears as continuous oscillation and is intensified as laser power density increases.


A New Model Of Selective Photothermolysis To Aid Laser Treatment Of Port Wine Stains, Dong Li, Ya-Ling He, Guo-Xiang Wang, Yong-Xian Wang, Zhao-Xia Ying Apr 2015

A New Model Of Selective Photothermolysis To Aid Laser Treatment Of Port Wine Stains, Dong Li, Ya-Ling He, Guo-Xiang Wang, Yong-Xian Wang, Zhao-Xia Ying

Dr. Guo-Xiang Wang

Pulsed dye lasers equipped with cryogen spray cooling (CSC) are now widely used to treat vascular malformation such as port wine stains (PWSs). This paper presents a new integrated model that can quantitatively simulate the cooling of the skin and the heating of the targeted blood vessels in PWSs during laser treatment. The new model is based on the classical homogeneous multi-layer skin model that treats PWS-containing dermis as a mixture of dermal tissue and homogeneously distributed blood. Light propagation in skin and PWSs is simulated by a Monte-Carlo method, which provides accurate description of the light scattering and absorption ...


Numerical Simulations Of The Discontinuous Progression Of Cerebral Aneurysms Based On Fluid-Structure Interactions Study, Xiao-Qi Ma, Yue-She Wang, Fang-Ju Yu, Guo-Xiang Wang Apr 2015

Numerical Simulations Of The Discontinuous Progression Of Cerebral Aneurysms Based On Fluid-Structure Interactions Study, Xiao-Qi Ma, Yue-She Wang, Fang-Ju Yu, Guo-Xiang Wang

Dr. Guo-Xiang Wang

Investigations into the characteristics of hemodynamics will provide a better understanding of the pathology of cerebral aneurysms for clinicians. In this work, a steady state discontinuous-growth model of the cerebral aneurysms was proposed. With the assumption of the fluid-structure interaction between the wall of blood vessel and blood, a fluid-structure coupling numerical simulation for this model was built using software ANSYS and CFX. The simulation results showed that as the aneurysm volume increased, a blood flow vortex came forth, the vortex region became asymptotically larger, and eddy density became gradually stronger in it. After the emergence of the vortex region ...


Prediction Of Evaporation Heat Transfer Coefficient Based On Gas-Liquid Two-Phase Annular Flow Regime In Horizontal Microfin Tubes,, Yueshe Wang, Yanling Wang, Guo-Xiang Wang, Hiroshi Honda Apr 2015

Prediction Of Evaporation Heat Transfer Coefficient Based On Gas-Liquid Two-Phase Annular Flow Regime In Horizontal Microfin Tubes,, Yueshe Wang, Yanling Wang, Guo-Xiang Wang, Hiroshi Honda

Dr. Guo-Xiang Wang

A physical model of gas–liquid two-phase annular flow regime is presented for predicting the enhanced evaporation heat transfer characteristics in horizontal microfin tubes. The model is based on the equivalence of a periodical distortion of the disturbance wave in the substrate layer. Corresponding to the stratified flow model proposed previously by authors, the dimensionless quantity Fr0 = G/[gdeρv(ρlρv)]0.5 may be used as a measure for determining the applicability of the present theoretical model, which was used to restrict the transition boundary between the stratified-wavy flow and the annular/intermittent ...


Understanding The Heat Transfer And Solidification Plasma-Sprayed Yttria-Stabilized Zirconia Coatings, Guo-Xiang Wang, R. Goswami, S. Sampath, V. Prasad Apr 2015

Understanding The Heat Transfer And Solidification Plasma-Sprayed Yttria-Stabilized Zirconia Coatings, Guo-Xiang Wang, R. Goswami, S. Sampath, V. Prasad

Dr. Guo-Xiang Wang

A variety of microstructures have been observed in plasma-sprayed yttria-partially stabilized zirconia (YSZ) thermal barrier coatings. Control of the coating microstructures requires a good understanding of the heat transfer and solidification during the process. This article presents a quantitative analysis of heat transfer and solidification of plasma-sprayed YSZ splats. The analysis is based on a simple heat transfer and solidification model that solves a one-dimensional moving boundary problem with consideration of melt undercooling prior to solidification and nonequilibrium crystalline growth kinetics at the moving interface. The solidification morphology is first assumed to be planar, and the stability of the planar ...


Numerical Analysis Of Cold Injury Of Skin In Cryogen Spray Cooling For Laser Dermatologic Surgery, Dong Li, Bin Chen, Wen-Juan Wu, Ya-Ling He, Lin Xing, Guo-Xiang Wang Apr 2015

Numerical Analysis Of Cold Injury Of Skin In Cryogen Spray Cooling For Laser Dermatologic Surgery, Dong Li, Bin Chen, Wen-Juan Wu, Ya-Ling He, Lin Xing, Guo-Xiang Wang

Dr. Guo-Xiang Wang

In laser dermatologic surgery, cryogen spray cooling (CSC) is used to avoid unwanted thermal damage such as scars from skin burning due to the melanin absorption of the laser beam. As the cryogen is fully atomized from the nozzle, temperature of the droplets can quickly drop below -60 oC because of evaporation. Such low temperature may lead to cold injury of skin. Therefore, spray cooling process should be accurately controlled during clinical practice to achieve sufficient protection and avoid cold injury. This study presents a numerical analysis for cold injury of skin in cryogen spray cooling for dermatologic laser surgery ...


An Investigation Of Nanoparticles Addition On Solidification Kinetics And Microstructure Development Of Tin–Lead Solder, D. Lin, S. Liu, T. Guo, Guo-Xiang Wang, T. Srivatsan, M. Petraroli Apr 2015

An Investigation Of Nanoparticles Addition On Solidification Kinetics And Microstructure Development Of Tin–Lead Solder, D. Lin, S. Liu, T. Guo, Guo-Xiang Wang, T. Srivatsan, M. Petraroli

Dr. Guo-Xiang Wang

High strength solders can be engineered by adding trace amounts of nanopowders into solder paste. An experimental study was conducted for a better understanding of the solidification kinetics and microstructure development of such nano-composite tin–lead solders. The composite solder pastes were prepared by mechanically mixing nanopowders of either copper or TiO2 with tin–lead powders (tens of microns in size). Solidification experiments of the composite solders were performed in an aluminum crucible with temperature variation during cooling and solidification being measured. For the titanium dioxide (TiO2) nanopowders-reinforced composite solders, the test data reveals the occurrence of melt ...


A Study Aimed At Characterizing The Interfacial Structure In A Tin-Silver Solder On Nickel-Coated Copper Plate During Aging, D. C. Lin, R. Kovacevic, T. S. Srivatsan, Guo-Xiang Wang Apr 2015

A Study Aimed At Characterizing The Interfacial Structure In A Tin-Silver Solder On Nickel-Coated Copper Plate During Aging, D. C. Lin, R. Kovacevic, T. S. Srivatsan, Guo-Xiang Wang

Dr. Guo-Xiang Wang

This paper highlights the interfacial structure of tin-silver (Sn-3·5Ag) solder on nickel-coated copper pads during aging performance studies at a temperature of 150°C for up to 96 h. Experimental results revealed the as-solidified solder bump made from using the lead-free solder (Sn-3·5Ag) exhibited or showed a thin layer of the tin-nickel-copper intermetallic compound (IMC) at the solder/substrate interface. This includes a sub-layer having a planar structure immediately adjacent to the Ni-coating and a blocky structure on the inside of the solder. Aging performance studies revealed the thickness of both the IMC layer and the sub-layer, having ...


Evaluation Of Evaporation Models For Single Moving Droplet With A High Evaporation Rate, Zhou Zhifu, Guo-Xiang Wang, Chen Bin, Guo Liejin, Wang Yueshe Apr 2015

Evaluation Of Evaporation Models For Single Moving Droplet With A High Evaporation Rate, Zhou Zhifu, Guo-Xiang Wang, Chen Bin, Guo Liejin, Wang Yueshe

Dr. Guo-Xiang Wang

Evaporation of a moving liquid droplet in atmosphere is a common phenomenon with wide engineering applications. Theoretical models that consider mass, momentum, and energy transfer between the droplet and the surrounding gas have been well documented in the literature to predict the variation of the velocity, the size, and the temperature of a moving droplet. Carefully designed experiments of a single evaporating droplet subject to gas flow have also been conducted to provide the first hand data for model comparison. The objective of this paper is to evaluate existing evaporation models with high evaporation rate. A literature review is present ...


A Three-Temperature Model Of Selective Photothermolysis For Laser Treatment Of Port Wine Stain Containing Large Malformed Blood Vessels, D. Li, Guo-Xiang Wang, Y. He, W. Wu, B. Chen Apr 2015

A Three-Temperature Model Of Selective Photothermolysis For Laser Treatment Of Port Wine Stain Containing Large Malformed Blood Vessels, D. Li, Guo-Xiang Wang, Y. He, W. Wu, B. Chen

Dr. Guo-Xiang Wang

As congenital vascular malformations, port wine stain (PWS) is composed of ectatic venular capillary blood vessels buried within healthy dermis. In clinic, pulsed dye laser (PDL) in visible band (e.g. 585 nm) together with cryogen spray cooling (CSC) have become the golden standard for treatment of PWS. However, due to the limited energy deposition of the PDL in blood, large blood vessels are likely to survive from the laser irradiation. As a result, complete clearance of the lesions is rarely achieved. Assuming the local thermal non-equilibrium in skin tissue during the laser surgery, a three-temperature model is proposed to ...


Multi-Scale Modeling Of Tissue Freezing During Cryogen Spray Cooling With R134a, R407c And R404a, D. Li, B. Chen, W. Wu, Guo-Xiang Wang, Y. He Apr 2015

Multi-Scale Modeling Of Tissue Freezing During Cryogen Spray Cooling With R134a, R407c And R404a, D. Li, B. Chen, W. Wu, Guo-Xiang Wang, Y. He

Dr. Guo-Xiang Wang

In laser dermatologic surgery, cryogen spray cooling (CSC) has been proved to be an efficient cooling technique to avoid thermal damage from skin burning due to the light energy absorption by melanin in epidermis. R134a is now the only cooling agent in commercial laser and has been proved to be effective for light pigmented skin. R407c and R404a could provide better cooling effect for darkly pigmented skin than R134a because both of them have much lower boiling point. In order to investigate the potential cold injury mechanism prior to the further clinic use, this paper presents a multi-scale model to ...


Single-And Multi-Hole Baffles-A Heat Transfer And Fluid Flow Control For Hydrothermal Growth, Edward Evans, Hongmin Li, Guo-Xiang Wang Apr 2015

Single-And Multi-Hole Baffles-A Heat Transfer And Fluid Flow Control For Hydrothermal Growth, Edward Evans, Hongmin Li, Guo-Xiang Wang

Dr. Guo-Xiang Wang

Hydrothermal solution growth is an important technique to grow high-quality single crystals. An autoclave, a closed cylindrical low-carbon steel vessel, is used to grow the large size crystals. A baffle located at the median height divides an autoclave into two chambers. Previous numerical studies indicate that the buoyancy-driven flow within an autoclave is very sensitive to the temperatures on the wall established by the heating. Baffles are required to establish the conditions for growth of high quality single crystals. This paper presents a numerical study of the effects of various baffles on the fluid flow and temperature fields in an ...


The Influence Of Nano-Particles On Microstructural Development At The Interface Of Sn3.5ag-Solder And Cu-Substrate, D. Lin, T. Srivatsan, Guo-Xiang Wang Apr 2015

The Influence Of Nano-Particles On Microstructural Development At The Interface Of Sn3.5ag-Solder And Cu-Substrate, D. Lin, T. Srivatsan, Guo-Xiang Wang

Dr. Guo-Xiang Wang

Preliminary experimental results have shown that an unexpected large needle-like phase Ag3Sn grows from the solder/substrate interface and large polygon-like Sn-Cu intermetallic compounds are present in the region, which is close to the interface when using lead-free binary Sn3.5Ag solder alloy. This paper summarises the efforts made to prevent the formation of these deleterious phases. An addition of 0.25 wt% of either copper nano-particles or nickel nano-particles was found to effectively avoid the formation of large Ag3Sn phase and to modify the solder matrix through a random dispersion of the in-situ intermetallic compounds Cu6Sn5 or Sn4Ni3. The ...


Multi-Phase Flow And Drying Characteristics In A Semi-Circular Impinging Stream Dryer, X. Huai, X. Peng, Guo-Xiang Wang, D. Liu Apr 2015

Multi-Phase Flow And Drying Characteristics In A Semi-Circular Impinging Stream Dryer, X. Huai, X. Peng, Guo-Xiang Wang, D. Liu

Dr. Guo-Xiang Wang

A physical model was proposed to describe granular material drying in a semi-circular impinging stream dryer, and the multi-phase flow characteristics as well as the heat and mass transfer were numerically investigated. Specially, the influence of various factors (inlet air temperature, mass flow-rate ratio, initial moisture content etc.) on drying process was inspected. The results indicate that constant drying rate period does not exist in a semi-circular impinging stream dryer. Appropriate curvature radius, flow-rate ratio, air velocity and higher inlet air temperature should be chosen for improving the drying performance, and decreasing the energy consumption and operation cost. The numerical ...


Microstructural Development In A Rapidly Cooled Eutectic Sn–3.5% Ag Solder Reinforced With Copper Powder, D. Lin, T. Srivatsan, Guo-Xiang Wang, R. Kovacevic Apr 2015

Microstructural Development In A Rapidly Cooled Eutectic Sn–3.5% Ag Solder Reinforced With Copper Powder, D. Lin, T. Srivatsan, Guo-Xiang Wang, R. Kovacevic

Dr. Guo-Xiang Wang

Experiments using eutectic Sn–3.5% Ag solder paste were conducted with the objective of examining the conjoint influence of copper particles addition and rapid cooling on microstructural development. The composite solder mixture was made by thoroughly mixing a pre-weighed amount of copper particles with a commercial Sn–3.5% Ag solder paste. The experiments were quite similar to the heating and cooling cycle of an industrial reflow soldering process. Heating of the samples was conducted in a furnace whose temperature was carefully controlled. The cooling process was conducted on a chilled aluminum block through which coolant was circulated at ...


Synthesis And Characterization Of Nano-Composite Lead-Free Solder, D. Lin, C. Kuo, T. Srivatsan, M. Petraroli, Guo-Xiang Wang Apr 2015

Synthesis And Characterization Of Nano-Composite Lead-Free Solder, D. Lin, C. Kuo, T. Srivatsan, M. Petraroli, Guo-Xiang Wang

Dr. Guo-Xiang Wang

A series of experiments conducted on a lead-free eutectic solder (Sn-3.5%Ag) have shown that addition of trace amounts of nanometer-sized particles does have an influence on mechanical properties of materials. In this study, three different types of nanoparticles (copper, nickel and iron) were chosen as the reinforcing candidate. For each particulate reinforcement the reflow process was performed under identical cooling conditions. Addition of trace amounts of nano-particles alters the kinetics governing solidification of the composite solder paste while concurrently exerting an influence on microstructural development, particularly the formation and presence of second phases in the solidified end product ...


Numerical Prediction Of The Intracellular Ice Formation Zone During Cryosurgery On A Nodular Basal Cell Carcinoma Using Liquid Nitrogen Spray, F. Sun, L. Martinez-Suastegui, Guo-Xiang Wang, G. Aguilar Apr 2015

Numerical Prediction Of The Intracellular Ice Formation Zone During Cryosurgery On A Nodular Basal Cell Carcinoma Using Liquid Nitrogen Spray, F. Sun, L. Martinez-Suastegui, Guo-Xiang Wang, G. Aguilar

Dr. Guo-Xiang Wang

Cryosurgery is a surgical technique that employs freezing to destroy target tumor tissue. While the main objective during a cryosurgical procedure is to ensure tissue destruction within the cryolesion, the greatest challenge is how to spare the surrounding healthy tissues from cryoablation. In this work, a historical review of the field of cryosurgery is presented followed by a theoretical study where a mathematical model is developed for cryosurgery on a basal cell carcinoma (BCC) using liquid nitrogen (LN2) spray. The model takes into consideration the anatomic structure of skin tissue and the irregular geometry of BCC. In particular, a ...


Understanding The Influence Of Copper Nanoparticles On Thermal Characteristics And Microstructural Development Of A Tin-Silver Solder, D. Lin, T. Srivatsan, Guo-Xiang Wang, R. Kovacevic Apr 2015

Understanding The Influence Of Copper Nanoparticles On Thermal Characteristics And Microstructural Development Of A Tin-Silver Solder, D. Lin, T. Srivatsan, Guo-Xiang Wang, R. Kovacevic

Dr. Guo-Xiang Wang

This paper presents and discusses issues relevant to solidification of a chosen lead-free solder, the eutectic Sn-3.5%Ag, and its composite counterparts. Direct temperature recordings for the no-clean solder paste during the simulated reflow process revealed a significant amount of undercooling to occur prior to the initiation of solidification of the eutectic Sn-3.5%Ag solder, which is 6.5 °C, and for the composite counterparts, it is dependent on the percentage of copper nanopowder. Temperature recordings revealed the same temperature level of 221 °C for both melting (from solid to liquid) and final solidification (after recalescence) of the ...


Three-Dimensional Flow Of Solution In An Industry-Size Hydrothermal Autoclave Subjected To Non-Uniform Heating Effects Of A Baffle On Flow And Temperature Separation, Hongmin Li, Guo-Xiang Wang, Edward Evans Apr 2015

Three-Dimensional Flow Of Solution In An Industry-Size Hydrothermal Autoclave Subjected To Non-Uniform Heating Effects Of A Baffle On Flow And Temperature Separation, Hongmin Li, Guo-Xiang Wang, Edward Evans

Dr. Guo-Xiang Wang

Hydrothermal growth takes place in a closed cylindrical container called an autoclave. Natural convection flow of an aqueous solution at a high temperature and a high pressure carries the nutrient. The high temperature growth condition and the natural convection flow are maintained by two independently controlled electrical heaters on the outside of the autoclave. In practice, the heating is circumferentially non-uniform. Many theoretical and numerical studies, however, assume axially symmetric heating conditions. This paper presents a numerical analysis of the three-dimensional heat transfer and fluid flow with a non-uniform heating condition. The analysis is based on an industry-size autoclave with ...


An Experimental Study On Pulsed Spray Cooling With Refrigerant R-404a In Laser Surgery, Zhifu Zhou, Bin Chen, Yueshe Wang, Liejin Guo, Guo-Xiang Wang Apr 2015

An Experimental Study On Pulsed Spray Cooling With Refrigerant R-404a In Laser Surgery, Zhifu Zhou, Bin Chen, Yueshe Wang, Liejin Guo, Guo-Xiang Wang

Dr. Guo-Xiang Wang

With a low boiling point (−45.5 °C at 1 atm) and high volatility, cryogen R-404a has the potential to replace current R-134a (−26.1 °C at 1 atm) for improved therapeutic outcome of dark skins in cutaneous laser treatment. This paper presents an experimental study on pulse spray cooling with cryogen R-404a including the spray characteristics and the resulting dynamic cooling of a solid surface. The spray system includes a special designed pressure nozzle (with the tube diameter less than 1 mm) that is connected to a fast response electric valve which can open or close within 5 ms ...


An Experimental Study On The Spray And Thermal Characteristics Of R134a Two-Phase Flashing Spray, Zhou Zhifu, Wu Weitao, Chen Bin, Guo-Xiang Wang, Guo Liejin Apr 2015

An Experimental Study On The Spray And Thermal Characteristics Of R134a Two-Phase Flashing Spray, Zhou Zhifu, Wu Weitao, Chen Bin, Guo-Xiang Wang, Guo Liejin

Dr. Guo-Xiang Wang

Flashing spray of volatile liquids is a common phenomenon observed in many industrial applications such as fuel injection of engines, accidental release of flammable and toxic pressure-liquefied gases, failure of a vessel or pipe in the form of a small hole in chemical industry, and cryogenic spray cooling in laser dermatology, etc. In flashing spray, the volatile liquid is depressurized rapidly at the exit of a nozzle (or a hole in a vessel) and becomes superheated. Such superheated liquid (in the form of either a jet or droplets) will lead to explosive atomization with fine droplet and a short spray ...