scholarly journals A Review of the Boiling Curve with Reference to Steel Quenching

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 974
Author(s):  
Manuel de J. Barrena-Rodríguez ◽  
Francisco A. Acosta-González ◽  
María M. Téllez-Rosas
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Conduction ◽  
Solid Phase ◽  
Current Knowledge ◽  
Fluid Velocity ◽  
Boiling Curve ◽  
Technical Literature ◽  
Modeling Accuracy

This review presents an analysis and discussion about heat transfer phenomena during quenching solid steel from high temperatures. It is shown a description of the boiling curve and the most used methods to characterize heat transfer when using liquid quenchants. The present work points out and criticizes important aspects that are frequently poorly attended in the technical literature about determination and use of the boiling curve and/or the respective heat transfer coefficient for modeling solid phase transformations in metals. Points to review include: effect of initial workpiece temperature on the boiling curve, fluid velocity specification to correlate with heat flux, and the importance of coupling between heat conduction in the workpiece and convection boiling to determine the wall heat flux. Finally, research opportunities in this field are suggested to improve current knowledge and extend quenching modeling accuracy to complex workpieces.

scholarly journals Numerical Study on Regenerative Cooling Characteristics of Kerosene Scramjets

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xuan Jin ◽  
Chibing Shen ◽  
Xianyu Wu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Velocity ◽  
Regenerative Cooling ◽  
Outlet Pressure

The use of kerosene-based regenerative cooling for scramjet has been found widespread attention due to its inherent nature of high energy utilization efficiency and good thermal protection performance. In order to provide a reference for the later design and experiments, three-dimensional turbulence simulations and sensitivity analysis were performed to determine the effects of three operating mode parameters, heat flux, mass flow rate, and outlet pressure, on the regenerative cooling characteristics of kerosene scramjets. A single rectangular-shaped channel for regenerative cooling was assumed. The RNG k-ε turbulence model and kerosene cracking mechanism with single-step global reaction were applied for the supercritical-pressure heat transfer of kerosene flows in the channel. Conclusions can be drawn that as the kerosene temperature rises along the channel, the decrease of fluid density and viscosity contributes to increasing the fluid velocity and heat transfer. When the kerosene temperature is close to the pseudocritical temperature, the pyrolysis reaction results into the rapid increase of fluid velocity. However, the heat transfer deterioration occurs as the specific heat and thermal conductivity experience their turning points. The higher heat flux leads to lower heat transfer coefficient, and the latter stops rising when the wall temperature reaches the pseudocritical temperature. The same rising trend of the heat transfer coefficient is observed under different outlet pressures, but the heat transfer deterioration occurs earlier at smaller outlet pressure for the reason that the corresponding pseudocritical temperature decreases. The heat transfer coefficient increases significantly along with the rise of the mass flow rate, which is mainly attributable to the increase of Reynolds number. Quantitative results indicate that as the main influence factors, the heat flux and mass flow rate are respectively negatively and positively relative to the intensification of heat transfer, but outlet pressure always has little effects on cooling performance.

Application of Inverse Heat Conduction Method and Method of Lines in Spray Cooling of Heated Surface

2016 ◽  
Author(s):  
Ramin Soujoudi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Conduction ◽  
Transfer Coefficient ◽  
Heated Surface ◽  
Method Of Lines ◽  
Spray Cooling ◽  
Approximation Technique ◽  
Inverse Heat Conduction

This paper investigates application of Method of Lines (MOL) and Inverse Heat Conduction techniques in spray cooling process. A flat face of a heated cylinder is cooled by using a nozzle spray and using room temperature water as a cooling fluid. The numerical analysis is done using MOL to estimate exposed surface temperature, surface heat flux, and convection heat transfer coefficient [3],[4]. Since there is no exact solution to verify the approximation result, for the verification purpose and accuracy of the result, the numerical result from this study is compared to other approximation results with experimental research done by Chen-Lee and Qiao-Chandra [1]. The results illustrate that disparity between the outcome of MOL and the one generated by Chen and Lee’s raw data is very insignificant throughout the whole time domain. This discrepancy between these two estimated results proves that MOL is a very reliable approximation technique compared to other finite element methods which require a finer mesh size and significant amount of calculations[2],[5]. However, comparing the results obtained through MOL with Qiao and Chandra shows that the difference between the estimated heat transfer coefficient and estimated heat flux converges rapidly for the short times of 0 < t < 60, but as the time passes, the MOL approximation results diverge slowly until it reaches its maximum value at ninety seconds, and the variance remains almost constant for the rest of the time period.

scholarly journals Analysis of temperature distribution in a pipe with inner mineral deposit

2014 ◽  
Vol 35 (2) ◽  
pp. 37-49
Author(s):  
Magda Joachimiak ◽  
Michał Ciałkowski ◽  
Jarosław Bartoszewicz
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Conduction ◽  
Temperature Distribution ◽  
Mineral Deposit ◽  
Mineral Deposits ◽  
Heat Conduction Coefficient ◽  
Temperature Distributions

Abstract The paper presents the results of calculations related to determination of temperature distributions in a steel pipe of a heat exchanger taking into account inner mineral deposits. Calculations have been carried out for silicate-based scale being characterized by a low heat transfer coefficient. Deposits of the lowest values of heat conduction coefficient are particularly impactful on the strength of thermally loaded elements. In the analysis the location of the thermocouple and the imperfection of its installation were taken into account. The paper presents the influence of determination accuracy of the heat flux on the pipe external wall on temperature distribution. The influence of the heat flux disturbance value on the thickness of deposit has also been analyzed.

scholarly journals Experimental Determination of the Heat Transfer Coefficient of Real Cooled Geometry Using Linear Regression Method

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 180
Author(s):  
Asif Ali ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
Bruno Facchini
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Linear Regression ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
External Surface ◽  
Internal Surface ◽  
Regression Method ◽  
Thermal Transient

The scope of this work was to develop a technique based on the regression method and apply it on a real cooled geometry for measuring its internal heat transfer distribution. The proposed methodology is based upon an already available literature approach. For implementation of the methodology, the geometry is initially heated to a known steady temperature, followed by thermal transient, induced by injection of ambient air to its internal cooling system. During the thermal transient, external surface temperature of the geometry is recorded with the help of infrared camera. Then, a numerical procedure based upon a series of transient finite element analyses of the geometry is applied by using the obtained experimental data. The total test duration is divided into time steps, during which the heat flux on the internal surface is iteratively updated to target the measured external surface temperature. The final procured heat flux and internal surface temperature data of each time step is used to find the convective heat transfer coefficient via linear regression. This methodology is successfully implemented on three geometries: a circular duct, a blade with U-bend internal channel, and a cooled high pressure vane of real engine, with the help of a test rig developed at the University of Florence, Italy. The results are compared with the ones retrieved with similar approach available in the open literature, and the pros and cons of both methodologies are discussed in detail for each geometry.

scholarly journals Darcy-Brinkman free convection about a wedge and a cone subjected to a mixed thermal boundary condition

1992 ◽  
Vol 15 (4) ◽  
pp. 789-794 ◽  
Author(s):  
G. Ramanaiah ◽  
V. Kumaran
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Porous Medium ◽  
Heat Transfer Coefficient ◽  
Free Convection ◽  
Transformation Group ◽  
Darcy Number ◽  
Thermal Boundary Condition ◽  
High Porosity

The Darcy-Brinkman free convection near a wedge and a cone in a porous medium with high porosity has been considered. The surfaces are subjected to a mixed thermal boundary condition characterized by a parameterm;m=0,1,∞correspond to the cases of prescribed temperature, prescribed heat flux and prescribed heat transfer coefficient respectively. It is shown that the solutions for differentmare dependent and a transformation group has been found, through which one can get solution for anymprovided solution for a particular value ofmis known. The effects of Darcy number on skin friction and rate of heat transfer are analyzed.

Observations of the Critical Heat Flux Process During Pool Boiling of FC-72

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
J. Jung ◽  
S. J. Kim ◽  
J. Kim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
High Heat ◽  
Line Length ◽  
Boiling Curve ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Ir Camera

Experimental work was undertaken to investigate the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface. The wetted area fraction (WF), the contact line length density (CLD), the frequency between dryout events, the lifetime of the dry patches, the speed of the advancing and receding contact lines, the dry patch size distribution on the surface, and the heat transfer from the liquid-covered areas were measured throughout the boiling curve. Quantitative analysis of this data at high heat flux and transition through CHF revealed that the boiling curve can simply be obtained by weighting the heat flux from the liquid-covered areas by WF. CHF mechanisms proposed in the literature were evaluated against the observations.

Numerical Simulation of Convective Heat Transfer in a Spark Ignition Engine

2008 ◽  
Author(s):  
Arash Mohammadi ◽  
Seyed Ali Jazayeri ◽  
Masoud Ziabasharhagh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Combustion Chamber ◽  
Spark Ignition Engine ◽  
Cylinder Wall ◽  
Single Cylinder Engine ◽  
Crank Angle ◽  
Exhaust Valves

A computational fluid dynamics code is applied to simulate fluid flow and combustion in a four-stroke single cylinder engine with flat combustion chamber geometry. Heat flux and heat transfer coefficient on the cylinder head, cylinder wall, piston, intake and exhaust valves are determined. Result for a certain condition is compared for total heat transfer coefficient of the cylinder engine with available correlation proposed by experimental measurement in the literature and close agreement is observed. It is observed that the value of heat flux and heat transfer coefficient varies considerably in different positions of the combustion chamber, but the trend with crank angle is almost the same.

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