scholarly journals Heat flow and heat transfer coefficient during crystallization under the pressure

2018 ◽  
Vol 157 ◽  
pp. 02036
Author(s):  
Richard Pastirčák ◽  
Ján Ščury ◽  
Tomáš Fecura
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Solidification Process ◽  
Metal Mold ◽  
Transfer Coefficients ◽  
Microstructure Modeling ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Solidification Processes ◽  
Precise Prediction

Estimation of the heat flow at the metal-mold interface is necessary for accurate simulation of the solidification processes. For the numerical simulation, a precise prediction of boundary conditions is required to determine the temperature distribution during solidification, porosity nucleation, microstructure development, and residual stresses. Determination of the heat transfer coefficients at the metal-mold interface is a critical aspect for simulation of the solidification process and the microstructure modeling of the castings. For crystallization under the pressure and for thin-walled castings, HTC evaluation is important due to the very limited freezing time.

scholarly journals Heat Transfer and Fluid Dynamics Measurements in the Expansion Space of a Stirling Cycle Engine

2006 ◽  
Author(s):  
Nan Jiang ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
High Efficiency ◽  
Stirling Engine ◽  
Transfer Coefficients ◽  
Head Region ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Engine Design ◽  
Region Flow ◽  
Design Calculations

The heater (or acceptor) of a Stirling engine, where most of the thermal energy is accepted into the engine by heat transfer, is the hottest part of the engine. Almost as hot is the adjacent expansion space of the engine. In the expansion space, the flow is oscillatory, impinging on a two-dimensional concavely-curved surface. Knowing the heat transfer on the inside surface of the engine head is critical to the engine design for efficiency and reliability. However, the flow in this region is not well understood and support is required to develop the CFD codes needed to design modern Stirling engines of high efficiency and power output. The present project is to experimentally investigate the flow and heat transfer in the heater head region. Flow fields and heat transfer coefficients are measured to characterize the oscillatory flow as well as to supply experimental validation for the CFD Stirling engine design codes. Presented also is a discussion of how these results might be used for heater head and acceptor region design calculations.

Metal–mold heat transfer coefficients during horizontal and vertical Unsteady-State solidification of Al–Cu and Sn–Pb Alloys

2004 ◽  
Vol 12 (3) ◽  
pp. 279-296 ◽  
Author(s):  
Carlos A. Santos ◽  
Cláudio A. Siqueira ◽  
Amauri Garcia ◽  
José M.V. Quaresma ◽  
Jaime A. Spim
Keyword(s):  
Heat Transfer ◽  
Unsteady State ◽  
Metal Mold ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The Effect of Entrance Configuration on Local Heat-transfer Coefficients in Subsonic Diffusers

1972 ◽  
Vol 94 (4) ◽  
pp. 355-359 ◽  
Author(s):  
E. O. Stoffel ◽  
J. R. Welty
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Transfer Equations ◽  
Subsonic Diffuser

The effects of square and reentrant entrances on flow regimes (no “appreciable” separation, large transitory stall, and fully developed two-dimensional stall) and local heat-transfer coefficients were determined with air flowing through a symmetrical, plane-wall, two-dimensional subsonic diffuser with one of the diverging walls heated and maintained isothermal. Flow and heat-transfer studies were made for the following ranges: 2θ = 0 to 45 deg, L/W = 6 to 18, and Rextut = 4 × 104 to 3 × 105. Results indicated that 2θ, L/W, and entrance configuration greatly affected the flow regime and heat transfer. Equations relating Um′ to Ut, Ur to Ut, and equations of the type Nu = C Pr0.6Rex0.8 are presented. For the configurations tested, heat-transfer rates were greater for reentrant than for square entrances.

Heat Transfer in Stepped Labyrinth Seals

1988 ◽  
Vol 110 (1) ◽  
pp. 63-69 ◽  
Author(s):  
S. Wittig ◽  
K. Jacobsen ◽  
U. Schelling ◽  
S. Kim
Keyword(s):  
Heat Transfer ◽  
Wall Friction ◽  
Leakage Flow ◽  
Test Rig ◽  
Transfer Coefficients ◽  
Labyrinth Seals ◽  
Finite Element Program ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Element Program

Leakage flow and heat transfer of scaled-up stepped labyrinth seals were investigated experimentally and numerically. The experiments were conducted in a test rig under steady conditions. For different geometries and pressure ratios a finite element program was used to determine the temperature distribution and subsequently the heat transfer coefficients. In verifying the experimental results, the flow field of the seals was calculated numerically by a finite difference program. Heat transfer coefficients were derived utilizing the well-known analogies between heat transfer and wall friction.

Liquid-Vapor Oscillating Flow and Heat Transfer in a U-Shaped Minichannel With Internal Wick Structure

2009 ◽  
Author(s):  
Jiajun Xu ◽  
Yuwen Zhang ◽  
H. B. Ma
Keyword(s):  
Heat Transfer ◽  
Oscillatory Flow ◽  
Oscillating Flow ◽  
Transfer Coefficients ◽  
Oscillating Heat Pipe ◽  
Heat Transfer Coefficients ◽  
Evaporation And Condensation ◽  
Flow And Heat Transfer ◽  
Wick Structure ◽  
Liquid Vapor

Liquid-vapor oscillating flow and heat transfer in a vertically placed oscillating heat pipe (OHP) with a sintered particle wick structure inside are analyzed in this paper. The evaporation and condensation heat transfer coefficients are obtained by solving the microfilm evaporation and condensation on the sintered particles. The sensible heat transfer between the liquid slug and the channel wall are obtained by analytical solution or empirical correlations, depending on whether the liquid flow is laminar or turbulent. The effects of the maximum evaporation and condensation angles on the oscillatory flow, as well as sensible and latent heat transfer are analyzed.

Nanofluid Heat and Mass Transfer in a Deformable and Peristaltic Pump

2019 ◽  
Vol 8 (8) ◽  
pp. 1632-1639
Author(s):  
Aamir Ali ◽  
Y. Ali ◽  
D.N. Khan Marwat ◽  
M. Awais
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Surface Deformation ◽  
Wave Number ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Diffusion Parameters ◽  
Peristaltic Movement

Flow heat and mass transfer in a deformable channel of peristaltically moving walls is investigated in this paper. Moreover, the channel is filled with nanofluids. The purpose of this study is to examine the combined effects of surface deformation and peristaltic movement of the walls on the nanofluid flow in a channel. We have considered the effects of nanofluid in the peristaltically deformable porous channel whose walls are contracting or expanding in the normal direction. Nanofluids have been used to enhance the thermo-physical properties of fluids such as thermal diffusivity, thermal conductivity and convective heat transfer coefficients on flow and heat transfer. The analytic solution of the problem have been presented. We have analyzed the effects of different involved parameters such as Reynolds number, surface deformation parameter, Prandtl number, wave number, Brownian and thermophoretic diffusion parameters and Schmidt number on the velocity profile, the temperature profile, pressure distribution and the concentration profile with the help of graphs. The results are shown graphically and discussed physically. It is observed that the deformation increases the axial velocity and temperature of the fluid.

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