The relationship between thermal history and microstructure in spray-deposited tin-lead alloys

1991 ◽  
Vol 6 (7) ◽  
pp. 1433-1454 ◽  
Author(s):  
B.P. Bewlay ◽  
B. Cantor
Keyword(s):  
Heat Transfer ◽  
Grain Size ◽  
Thermal History ◽  
Numerical Models ◽  
Spray Deposition ◽  
Microstructural Analysis ◽  
Flow Rate Ratio ◽  
Flow Rates ◽  
Substrate Interface ◽  
Spray Deposit

Gas-atomized spray deposition involves the creation of a spray of droplets by a gas atomizer and the consolidation and solidification of these droplets on a substrate. The present paper describes an investigation of the fundamental characteristics of heat transfer and solidification during spray deposition. Spray deposition was used to manufacture Sn-15 and 38 wt. % Pb preforms using atomizer-substrate distances of 180 and 360 mm, gas flow rates of 2.5 and 3.4 g/s, and melt flow rates of 61 and 35 g/s. Analytical and numerical models were developed to predict the thermal history of the spray deposit for a range of deposit-substrate heat transfer coefficients. A deposit-substrate heat transfer coefficient of ∼104 W m−2 K−1 was determined by comparing measured and calculated spray-deposit thermal histories both during and after spray deposition. Microstructural analysis of transverse sections of the spray deposits revealed maximum values of spray-deposit density and cell/grain size at specific distances from the deposit-substrate interface. The distance between the density and cell/grain-size maxima and the deposit-substrate interface increased from 0.9 to 10 mm for Sn–15 wt. % Pb and from 2.6 to 11.3 mm for Sn–38 wt. % Pb as the atomizer-substrate distance was increased from 180 to 360 mm and the melt to gas mass flow rate ratio was decreased from 24 to 10. The origin of these microstructural features is described in terms of heat transfer during spray deposition.

Analysis of the Temperature Evolution during Lined Pipe Welding

2014 ◽  
Vol 1016 ◽  
pp. 753-757 ◽  
Author(s):  
Obeid Obeid ◽  
Giulio Alfano ◽  
Hamid Bahai
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Heat Source ◽  
Thermal History ◽  
Numerical Models ◽  
Welding Process ◽  
Gta Welding ◽  
Element Analysis ◽  
Pipe Welding ◽  
Mn Steel

A numerical analysis of thermal phenomena occurring during lined-pipe welding is presented in this paper. Numerical models of surfaces and volumetric heat sources were used to predict the time evolution of the temperature field both in a corrosion-resistance-alloy (CRA) liner, made of SUS304 stainless steel (SS), and for the single-pass girth welding of a carbon-manganese (C-Mn) steel pipe. Using the finite-element code ABAQUS, three-dimensional non-liner heat-transfer analyses was carried out to simulate the gas-tungsten-arc (GTA) welding process used in liner welding and the metal-inert-gas (MIG) welding process consumed in C-Mn steel backing welding. FORTRAN user subroutines were coded to implement the movable welding heat source and heat transfer coefficient models. The thermal history was numerically computed at locations where circumferential angles from the welding start/atop position are 90°, 180° and 270° with respect to axial distances from the weld centerline (WC). Keywords: Finite element analysis FEA, CRA Liner, C-Mn steel backing, Heat source, Thermal history.

Enhanced Spray Cooling Using Micropillar Arrays: A Systematic Study

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Sankar Muthukrishnan ◽  
Vinod Srinivasan
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Flow Rate Ratio ◽  
Textured Surfaces ◽  
Continuous Increase ◽  
Flow Rates ◽  
Pillar Diameter ◽  
Liquid Mass Flow Rate ◽  
Micropillar Arrays

Abstract The role of contact-line evaporation on spray impingement heat transfer is systematically studied by spraying de-ionized water on silicon substrates with micropillar arrays. The height, the pillar diameter, and the spacing of the micropillar array were varied from 5 to 50 μm while keeping the porosity constant at 0.75. An air-assisted nozzle was used to create a liquid spray with a Sauter mean diameter (SMD) of ∼22 to 42 μm depending on flow conditions. Most test runs were conducted at a water flow rate of 30 ml/min and an air-liquid mass flow rate ratio of ∼0.57. The results show a continuous increase in the critical heat flux (CHF) as the pillar diameter is decreased. The effects of pillar height are nonmonotonic, with CHF and peak heat transfer coefficient attaining a maximum as the height-to-diameter ratio approaches unity. Values of CHF as high as 830 W/cm2 were achieved, along with cooling efficiencies of 49%. The effect of liquid flow rates and air-flow rates were also investigated independently using textured surfaces.

A Study on Evolution of Splat Radius and Temperature in Thermal Spray Process

2018 ◽  
Author(s):  
Manpreet Dash ◽  
Sangharsh Kumar ◽  
Partha Pratim Bandyopadhyay ◽  
Anandaroop Bhattacharya
Keyword(s):  
Heat Transfer ◽  
Thermal Spray ◽  
Molten Metal ◽  
Spray Deposition ◽  
Substrate Surface ◽  
Metal Droplet ◽  
Droplet Impingement ◽  
Impact Process ◽  
The Impact ◽  
Maximum Spreading

The impact process of a molten metal droplet impinging on a solid substrate surface is encountered in several technological applications such as ink-jet printing, spray cooling, coating processes, spray deposition of metal alloys, thermal spray coatings, manufacturing processes and fabrication and in industrial applications concerning thermal spray processes. Deposition of a molten material or metal in form of a droplet on a substrate surface by propelling it towards it forms the core of the spraying process. During the impact process, the molten metal droplet spreads radially and simultaneously starts losing heat due to heat transfer to the substrate surface. The associated heat transfer influences impingement behavior. The physics of droplet impingement is not only related to the fluid dynamics, but also to the respective interfacial properties of solid and liquid. For most applications, maximum spreading diameter of the splat is considered to be an important factor for droplet impingement on solid surfaces. In the present study, we have developed a model for droplet impingement based on energy conservation principle to predict the maximum spreading radius and the radius as a function of time. Further, we have used the radius as a function of time in the heat transfer equations and to study the evolution of splat-temperature and predict the spreading factor and the spreading time and mathematically correlate them to the spraying parameters and material properties.

Numerical Modeling of Heat Transfer and Pressure Losses for Uncooled Gas Turbine Blade Tip: Effect of Tip Clearance and Tip Geometry

2007 ◽  
Author(s):  
Lamyaa A. El-Gabry
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Gas Turbine ◽  
Computational Study ◽  
Numerical Models ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Pressure Losses ◽  
Blade Tip ◽  
Exit Mach Number

A computational study has been performed to predict the heat transfer distribution on the blade tip surface for a representative gas turbine first stage blade. CFD predictions of blade tip heat transfer are compared to test measurements taken in a linear cascade, when available. The blade geometry has an inlet Mach number of 0.3 and an exit Mach number of 0.75, pressure ratio of 1.5, exit Reynolds number based on axial chord of 2.57×106, and total turning of 110 deg. Three blade tip configurations were considered; they are flat tip, a full perimeter squealer, and an offset squealer where the rim is offset to the interior of the tip perimeter. These three tip geometries were modeled at three tip clearances of 1.25, 2.0, and 2.75% of blade span. The tip heat transfer results of the numerical models agree fairly well with the data and are comparable to other CFD predictions in the open literature.

Analysis of Heat Transfer through PVC Window Profile Reinforced with Ti6Al4V Alloy

2016 ◽  
Vol 687 ◽  
pp. 236-242 ◽  
Author(s):  
Piotr Lacki ◽  
Judyta Różycka ◽  
Marcin Rogoziński
Keyword(s):  
Heat Transfer ◽  
Titanium Alloy ◽  
Thermal Insulation ◽  
Numerical Models ◽  
Characteristic Temperature ◽  
Permanent Deformation ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Ti6al4v Titanium Alloy ◽  
Characteristic Points

This requires the use of additional reinforcement in order to prevent excessive or permanent deformation of PVC windows. In the paper particular attention was devoted to space located in a corrosive environment exposed to chemical agents. For this purpose, proposed to change the previously used steel profiles reinforcements made of Ti6Al4V titanium alloy corrosion-resistant in the air, at sea and many types of industrial atmosphere. Analysis of the thermal insulation properties of PVC windows with additional reinforcement of profile Ti6Al4V titanium alloy was performed. PVC window set in a layer of thermal insulation was analyzed. Research was conducted using Finite Element Analysis. Numerical models and thermal calculations were made in the program ADINA, assuming appropriate material parameters. The constant internal temperature of 20 ̊ and an outer-20 ̊ was assumed. The course of temperature distribution in baffle in time 24 hours and graphs of characteristic points was obtained. The time of in which followed the steady flow of heat, as well as the course of isotherm of characteristic temperature in the baffle was determined. On the basis of numerical analysis obtained vector distribution of heat flux q [W/m2] and was determined heat transfer coefficients U [W/m2K] for the whole window with titanium reinforcement . All results were compared with the model of PVC windows reinforced with steel profile.

A large grain size perovskite thin film with a dense structure for planar heterojunction solar cells via spray deposition under ambient conditions

RSC Advances ◽  
2015 ◽  
Vol 5 (74) ◽  
pp. 60562-60569 ◽  
Author(s):  
Zhurong Liang ◽  
Shaohong Zhang ◽  
Xueqing Xu ◽  
Nan Wang ◽  
Junxia Wang ◽  
...  
Keyword(s):  
Grain Size ◽  
Surface Coverage ◽  
Spray Deposition ◽  
Deposition Process ◽  
Ambient Conditions ◽  
High Quality ◽  
Dense Structure ◽  
Heterojunction Solar Cells ◽  
Planar Heterojunction Solar Cells ◽  
Planar Heterojunction

A facile spray deposition process was developed to prepare high-quality perovskite films with full surface coverage and large grain size.

Thermal Analysis for Cryosurgery of Nodular Basal Cell Carcinoma

2006 ◽  
Author(s):  
Feng Sun ◽  
G. Aguilar ◽  
K. M. Kelly ◽  
G.-X. Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cell Carcinoma ◽  
Convective Heat Transfer ◽  
Cooling Rate ◽  
Convective Heat ◽  
Thermal History ◽  
Convective Heat Transfer Coefficient ◽  
Target Tissue

Basel cell carcinoma (BCC) is the most common human skin malignancy. Its incidence has increased significantly in Australia, Europe and North America over the past decade. A number of modalities are currently used for treatment of BCC, including cryosurgery which offers a potential for high cure rate, low cost, minimal bleeding and good cosmetic effect. However, cryosurgery is not used frequently for BCC because no current method exists to design adequate treatment parameters. We present a numerical analysis on the thermal history of the target tissue during cryosurgery of a nodular BCC using liquid nitrogen (LN2) spray. The model uses Pennes equation to describe the heat transfer within the target tissue. A convective thermal boundary is used to describe the heat interaction between the tissue and LN2, and the apparent heat capacity method is applied to address the tissue phase change process. A parametric study is conducted on the convective heat transfer coefficient (hs: 104~106 W/m2·K), cooling site area (rs/R0: 0.5~1.0) and spray time (t: 0~30 sec.), with the objective to understand the thermal history during tissue freezing, including lethal temperature (-50 °C) and cooling rate (CR). Results demonstrate that propagation of the lethal isotherm is sensitive to the convective heat transfer coefficient, hs, with a range of 104~5×104 W/m2·K. Increasing the cooling site area can significantly enhance cooling efficiency, producing dramatic increase in the amount of tissue encompassed by the lethal isotherm. The cooling rate (CR) shows a highly dynamic distribution during the cooling process: the highest CR drops quickly from 140 °C/sec. (t=0.5 sec.) to 20 °C/sec. (t=5 sec.). The highest CR is initially located close to the cooling site but moves toward the inside of the tissue as treatment proceeds. The model presented herein provides a simulation tool for treatment planning of cryosurgery using LN2 spray, in which the protocol parameters, e.g. cooling site area and spray time, can be determined for an optimal outcome. The quantitative predictions on the propagation of lethal isotherm and the distribution of CR should help to optimize cryosurgery efficacy.

Leakage Flow Investigations on a Through-Wall Crack Related to Thermal Fatigue of Nuclear Power Plant Piping

2017 ◽  
Author(s):  
Stefan Schmid ◽  
Rudi Kulenovic ◽  
Eckart Laurien
Keyword(s):  
Experimental Data ◽  
Nuclear Power ◽  
Numerical Models ◽  
Measurement Techniques ◽  
Experimental Investigations ◽  
Leakage Flow ◽  
Test Rig ◽  
Reduced Pressure ◽  
Flow Rates ◽  
Set Up

For the validation of empirical models to calculate leakage flow rates in through-wall cracks of piping, reliable experimental data are essential. In this context, the Leakage Flow (LF) test rig was built up at the IKE for measurements of leakage flow rates with reduced pressure (maximum 1 MPA) and temperature (maximum 170 °C) compared to real plant conditions. The design of the test rig enables experimental investigations of through-wall cracks with different geometries and orientations by means of circular blank sheets with integrated cracks which are installed in the tubular test section of the test rig. In the paper, the experimental LF set-up and used measurement techniques are explained in detail. Furthermore, first leakage flow measurement results for one through-wall crack geometry and different imposed fluid pressures at ambient temperature conditions are presented and discussed. As an additional aspect the experimental data are used for the determination of the flow resistance of the investigated leak channel. Finally, the experimental results are compared with numerical results of WinLeck calculations to prove specifically in WinLeck implemented numerical models.

Study of the Size Effects and Friction Conditions in Microextrusion—Part II: Size Effect in Dynamic Friction for Brass-Steel Pairs

2007 ◽  
Vol 129 (4) ◽  
pp. 677-689 ◽  
Author(s):  
Lapo F. Mori ◽  
Neil Krishnan ◽  
Jian Cao ◽  
Horacio D. Espinosa
Keyword(s):  
Grain Size ◽  
Friction Coefficient ◽  
Size Effect ◽  
Contact Pressure ◽  
Size Effects ◽  
Numerical Models ◽  
Kolsky Bar ◽  
Experimental Results ◽  
Material Response ◽  
Dynamic Coefficients

In this paper, the results of experiments conducted to investigate the friction coefficient existing at a brass-steel interface are presented. The research discussed here is the second of a two-part study on the size effects in friction conditions that exist during microextrusion. In the regime of dimensions of the order of a few hundred microns, these size effects tend to play a significant role in affecting the characteristics of microforming processes. Experimental results presented in the previous companion paper have already shown that the friction conditions obtained from comparisons of experimental results and numerical models show a size effect related to the overall dimensions of the extruded part, assuming material response is homogeneous. Another interesting observation was made when extrusion experiments were performed to produce submillimeter sized pins. It was noted that pins fabricated from large grain-size material (211μm) showed a tendency to curve, whereas those fabricated from billets having a small grain size (32μm), did not show this tendency. In order to further investigate these phenomena, it was necessary to segregate the individual influences of material response and interfacial behavior on the microextrusion process, and therefore, a series of frictional experiments was conducted using a stored-energy Kolsky bar. The advantage of the Kolsky bar method is that it provides a direct measurement of the existing interfacial conditions and does not depend on material deformation behavior like other methods to measure friction. The method also provides both static and dynamic coefficients of friction, and these values could prove relevant for microextrusion tests performed at high strain rates. Tests were conducted using brass samples of a small grain size (32μm) and a large grain size (211μm) at low contact pressure (22MPa) and high contact pressure (250MPa) to see whether there was any change in the friction conditions due to these parameters. Another parameter that was varied was the area of contact. Static and dynamic coefficients of friction are reported for all the cases. The main conclusion of these experiments was that the friction coefficient did not show any significant dependence on the material grain size, interface pressure, or area of contact.

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