Heat transfer behavior during water spray quenching of 7xxx aluminum alloy plates

2021 ◽  
pp. 1-36
Author(s):  
Ning Fan ◽  
Baiqing Xiong ◽  
Zhihui Li ◽  
Yanan Li ◽  
Xiwu Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Nucleate Boiling ◽  
Spray Parameters ◽  
Spray Distance ◽  
Heat Transfer Behavior ◽  
Quenching Process ◽  
Transfer Behavior

Abstract The desired microstructure and mechanical properties of heat treatable 7xxx aluminum alloy can be achieved after spray quenching by controlling spray parameters. However, heat transfer behavior between specimen and quenchant is transient and complicated in quenching process. In this paper, a spray quenching system was utilized to quench for 7xxx aluminum alloy. The influence of spray parameters, including spray pressure and spray distance, on heat transfer behavior was examined and discussed. Heat flux and heat transfer coefficient were calculated by iterative method. The results indicated that the aluminum alloy experienced transition boiling, nucleate boiling and convection cooling regimes during spray quenching process. Heat transfer capability firstly increased and then decreased with the increasing of spray pressure or spray distance. A function of local heat transfer coefficient which is variable in specimen surface temperature, spray parameters and spatial location was constructed. Residual stress of 7xxx aluminum alloy plates was increased firstly and then slightly differed with the increase of volumetric flux.

Heat transfer coefficients for quenching process simulation

2004 ◽  
Vol 120 ◽  
pp. 269-276
Author(s):  
M. Maniruzzaman ◽  
R. D. Sisson
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Process Simulation ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Quenching Process

Quenching heat treatment in a liquid medium is a very complex heat transfer process. Heat extraction from the part surface occurs through several different heat transfer mechanisms in distinct temperature ranges, namely, film boiling, partial film boiling (i.e. transition), nucleate boiling and convection. The maximum heat transfer occurs during the nucleate boiling stage. Experimental study shows that, the effective surface heat transfer coefficient varies more than two orders of magnitude with the temperature during the quenching. For quenching process simulation, accurate prediction of the time-temperature history and microstructure evolution within the part largely depends on the accuracy of the boundary condition supplied. The heat transfer coefficient is the most important boundary condition for process simulation. This study focuses on creating a database of heat transfer coefficients for various liquid quenchant-metallic alloy combinations through experimentation using three different quench probes. This database is a web-based tool for use in quench process simulation. It provides at-a-glance information for quick and easy analysis and sets the stage for a Decision Support System (DSS) and Data Mining for heat-treating process.

Numerical Validation of Heat Transfer Characteristics for Shower Head Film Cooled Turbine Vane

2012 ◽  
Author(s):  
Reddaiah Vishnumolakala ◽  
Jong S. Liu ◽  
Sridhar Murari ◽  
Ramakumar Bommisetty
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Free Stream ◽  
Cooling Systems ◽  
Free Stream Turbulence ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Exit Mach Number

In modern gas turbines, film cooling is one of the widely used external cooling techniques for turbine vanes and blades. The turbine airfoil leading edge, which is highly loaded thermally, is currently protected from the hot gas by film cooling schemes, so called showerhead cooling. Flow field in film cooling is very complex and detailed knowledge of heat transfer rates and metal temperatures are required while designing these cooling systems. Computational Fluid Dynamics (CFD) is gaining popularity for modeling these complex cooling systems. However, the application of CFD depends on its accuracy and reliability. This requires the CFD code to be validated with laboratory measurements to ensure its predictive capacity. In this regard, a project has been taken to validate the commercially available CFD code for predicting the blade heat transfer characteristics with shower head film cooling. The validation is accomplished with the test results of Ames [5]. C3X vanes were used for their four vane cascade test facility. The showerhead array used consists of 5 rows of 20° spanwise slanted holes. Experiments were carried out with lower (1%) and higher (12%) turbulence intensities. Results of metal temperatures and heat transfer coefficients were reported. The objective of this study is to validate and calibrate a commercially available CFD code, against the available test data [5] and to understand the relationship between complex flow fields and heat transfer behavior. STAR-CCM+ is used for model generation, mesh generation and solution. Polyhedral elements with prism layers around the wall surfaces are generated. Three turbulence models, Durbin’s v2f model, Menter SST and SST transition models are explored in this study. Simulations are performed for two turbulence intensities available. Typical flow parameters such as blade surface heat transfer coefficient (HTC), surface temperatures and the location of flow transition are compared. Results were compared for two typical cascade exit Mach number conditions such as 0.2 and 0.7, which represents subsonic and transonic conditions respectively. Except in suction side transition region, numerically simulated heat transfer coefficient and Stanton number matched well with test data. Vane wall temperature contours were presented to understand the heat transfer behavior. The heat transfer behavior was numerically investigated for realistic exit Mach numbers. Sensitivity study for two inlet free stream turbulence intensities and three inlet free stream turbulence length scales are performed for realistic exit Mach number and reported heat transfer coefficient and Stanton number.

Experimental Investigation of Convective Heat Transfer in Circulating Water System

2012 ◽  
Vol 457-458 ◽  
pp. 439-444
Author(s):  
Shao Bo Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Effective Thermal Conductivity ◽  
Convective Heat ◽  
Particle Sizes ◽  
Heat Transfer Behavior ◽  
Transfer Behavior

The laminar convective heat transfer behavior of CuO nanoparticle dispersions in water with three different particle sizes (23 nm, 51 nm, and 76 nm) is investigated experimentally in a flow loop with constant heat flux. The main purpose of this study is to evaluate the effect of particle size on convective heat transfer in laminar region. The experimental results show that the suspended nanoparticles remarkably increase the convective heat transfer coefficient of the base fluid, and the nanofluid with 23nm particles shows higher heat transfer coefficient than nanofluids containing the other two particle sizes about 10% under the same Re. Based on the effective medium approximation and the fractal theory, the effective thermal conductivity of suspension is obtained. It is shown that if the new effective thermal conductivity correlation of the nanofluids is used in calculating the Prandtl and Nusselt numbers, the new correlation accurately reproduces the convective heat transfer behavior in tubes.

6063 Aluminum Alloy Online Quenching Surface Heat Transfer Coefficient and the Temperature Field Simulation

2013 ◽  
Vol 446-447 ◽  
pp. 146-150
Author(s):  
Hui Wang ◽  
Hai Bo Yang
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Temperature Field ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Jet Impact ◽  
Quenching Process ◽  
6063 Aluminum Alloy

For the 6063 aluminum alloy spray quenching process, respectively establish finite element model of upper, lower nozzle jet impact and water area and meshing in the Gambit. Import into fluent software for cooling numerical simulation, getting the upper and lower nozzle’s pressure contours , velocity contours , heat transfer coefficient curve and water area’s velocity contours and heat transfer coefficient curves. Analysis the various contours and the heat transfer coefficient along the aluminum plate surface radial distribution: upper nozzle’s heat transfer intensity is not in stationary point and near its both sides; Lower nozzle’s contours and heat transfer coefficient has a certain similarity with the upper nozzle, but the maximum heat transfer intensity is at stagnation point; Water area‘s heat transfer coefficient fall faster at the entrance and maintained at a constant value finally. Put heat transfer coefficient as a boundary condition into the ansys software to simulate the three dimensional temperature field of quenching process and analysis the temperature field contours in different time: the biggest speed is 36°C/s during the process of quenching, appearing in the high temperature range, namely deformation sensitive areas, therefore it most likely to occur deformation at the beginning of the quenching profiles.

Heat transfer coefficients for quenching process simulation

2004 ◽  
Vol 120 ◽  
pp. 521-528
Author(s):  
M. Maniruzzaman ◽  
R. D. Sisson
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Process Simulation ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Quenching Process

Quenching heat treatment in a liquid medium is a very complex heat transfer process. Heat extraction from the part surface occurs through several different heat transfer mechanisms in distinct temperature ranges, namely, film boiling, partial film boiling (i.e. transition), nucleate boiling and convection. The maximum heat transfer occurs during the nucleate boiling stage. Experimental study shows that, the effective surface heat transfer coefficient varies more than two orders of magnitude with the temperature during the quenching. For quenching process simulation, accurate prediction of the time-temperature history and microstructure evolution within the part largely depends on the accuracy of the boundary condition supplied. The heat transfer coefficient is the most important boundary condition for process simulation. This study focuses on creating a database of heat transfer coefficients for various liquid quenchant-metallic alloy combinations through experimentation using three different quench probes. This database is a web-based tool for use in quench process simulation. It provides at-a-glance information for quick and easy analysis and sets the stage for a Decision Support System (DSS) and Data Mining for heat-treating process.

Heat Transfer Behavior of the Boundary Layer Near Surfaces in Annular Flow of High Capacity Canned Motor Pump

2016 ◽  
Author(s):  
Shengde Wang ◽  
Guohu Luo ◽  
Hong Shen ◽  
Zhenqiang Yao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Annular Flow ◽  
High Capacity ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Canned Motor ◽  
The Heat Transfer Coefficient

As significant fluid machinery, canned motor pumps are widely applied in industrial field. The typical characteristic of canned motor pump is that the fluid comes into the narrow gap and affects the performance of canned motor. The coolant flow in the narrow annular gap between rotor and stator cans belongs to Taylor-Couette-Poiseuille flow which has been investigated for a long time while the thermal design is a key function of internal narrow gap annular flow of canned motor. However, the temperature distribution prediction of canned motor deviates from the experiments, especially in the high-capacity canned motor due to the large shear rate of fluid and eddy-current loss of motor’s can. According to the researcher’s work, the significant work lies in the heat transfer coefficient that different researchers give various numerical prediction and experimental measurement. It brings big challenge in thermal design of high-capacity canned motor pump. In this paper, the author focuses on the reason why the heat transfer coefficient is remarkably lower than that other’s forecast. In this paper, the heat transfer behavior of the boundary layer near surfaces in the annular flow is investigated by using the commercial fluid dynamic (CFD) method. Firstly, the Naiver-Stocks (N-S) equations and energy conservation equation are employed for modeling the flow and heat transfer behavior, and the k-ω turbulent model is used for solving the flow control equations. Secondly, the fluid domain is described by a simplified geometrical model: two concentric cylinders with finite gap length. Thirdly, numerical approach is used to analyze the subject with tools of Solidworks, ICEM CFD and Ansys Fluent. Two parameters are analyzed in the research, namely the rotating speed and the wall heat flux, without considering the fluid viscous dissipation and thermal contact resistance. Numerical simulation results indicate that Taylor vortex exists in the flow regime, and the temperature distribution is affected by both the rotating speed and the wall heat flux, named thermal barrier effect under large heat flux condition. The thermal barrier effect lies in that the temperature gradient of interface decreases compared to the peak value of temperature gradient near the surface, so that the heat transfer coefficient is reduced remarkably. This effect leads to the temperature prediction deviates from the experiment measurement.

A Loop Thermosyphon With Hydrophobic Spots Evaporator Surface

2018 ◽  
Author(s):  
Hongbin He ◽  
Biao Shen ◽  
Sumitomo Hidaka ◽  
Koji Takahashi ◽  
Yasuyuki Takata
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Nucleate Boiling ◽  
Working Fluid ◽  
Immersion Method ◽  
Two Phase ◽  
Coating Materials ◽  
High Heat Transfer ◽  
Coated Surface

Heat transfer characteristic of a closed two-phase thermosyphon with enhanced boiling surface is studied and compared with that of a copper mirror surface. Two-phase cooling improves heat transfer coefficient (HTC) a lot compared to single-phase liquid cooling. The evaporator surfaces, coated with a pattern of hydrophobic circle spots (non-electroplating Ni-PTFE, 0.5∼2 mm in diameter and 1.5–3 mm in pitch) on Cu substrates, achieve very high heat transfer coefficient and lower the incipience temperature overshoot using water as the working fluid. Sub-atmospheric boiling on the hydrophobic spot-coated surface shows a much better heat transfer performance. Tests with heat loads (30 W to 260 W) reveals the coated surfaces enhance nucleate boiling performance by increasing the bubbles nucleation sites density. Hydrophobic circle spots coated surface with diameter 1 mm, pitch 1.5 mm achieves the maximal heat transfer enhancement with the minimum boiling thermal resistance as low as 0.03 K/W. The comparison of three evaporator surfaces with same spot parameters but different coating materials is carried out experimentally. Ni-PTFE coated surface with immersion method performs the optimal performance of the thermosyphon.

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