Effects of Temperature and Heat Transfer on Shock Train Structures inside Constant-Area Isolators

Author(s):  
Kuo-Cheng Lin ◽  
Chung-Jen Tam ◽  
Dean Eklund ◽  
Kevin Jackson ◽  
Thomas Jackson
2010 ◽  
Vol 132 (11) ◽  
Author(s):  
A. Arikoglu ◽  
G. Komurgoz ◽  
I. Ozkol ◽  
A. Y. Gunes

The present work examines the effects of temperature and velocity jump conditions on heat transfer, fluid flow, and entropy generation. As the physical model, the axially symmetrical steady flow of a Newtonian ambient fluid over a single rotating disk is chosen. The related nonlinear governing equations for flow and thermal fields are reduced to ordinary differential equations by applying so-called classical approach, which was first introduced by von Karman. Instead of a numerical method, a recently developed popular semi numerical-analytical technique; differential transform method is employed to solve the reduced governing equations under the assumptions of velocity and thermal jump conditions on the disk surface. The combined effects of the velocity slip and temperature jump on the thermal and flow fields are investigated in great detail for different values of the nondimensional field parameters. In order to evaluate the efficiency of such rotating fluidic system, the entropy generation equation is derived and nondimensionalized. Additionally, special attention has been given to entropy generation, its characteristic and dependency on various parameters, i.e., group parameter, Kn and Re numbers, etc. It is observed that thermal and velocity jump strongly reduce the magnitude of entropy generation throughout the flow domain. As a result, the efficiency of the related physical system increases. A noticeable objective of this study is to give an open form solution of nonlinear field equations. The reduced recurative form of the governing equations presented gives the reader an opportunity to see the solution in open series form.


Author(s):  
Matt Goodro ◽  
Jongmyung Park ◽  
Phil Ligrani ◽  
Mike Fox ◽  
Hee-Koo Moon

Considered are the effects of temperature ratio on the heat transfer from an array of jets impinging on a flat plate. At constant Reynolds number of 18000, and constant Mach number of 0.2, different ratios of target plate temperature to jet temperature are employed. The spacing between holes in the streamwise direction X is 8D, and the spanwise spacing between holes in a given streamwise row Y is also 8D. The target plate is located 3D away from the impingement hole exits. Experimental results show that local, line-averaged, and spatially-averaged Nusselt numbers decrease as the Tw/Tj temperature ratio increases. This is believed to be due to the effects of temperature-dependent fluid properties, as they affect local and global turbulent transport in the flow field created by the array of impinging jets. The effect of temperature ratio on crossflow-to-jet mass velocity ratio and discharge coefficients are also examined.


Author(s):  
Ivan Otic

Abstract One important issue in understanding and modeling of turbulent heat transfer is the behavior of fluctuating temperature close to the wall. Common engineering computational approach assumes constant heat flux boundary condition on heated walls. In the present paper constant heat flux boundary condition was assumed and effects of temperature fluctuations are investigated using large eddy simulations (LES) approach. A series of large eddy simulations for two geometries is performed: First, forced convection in channels and second, forced convection over a backward facing step. LES simulation data is statistically analyzed and compared with results of direct numerical simulations (DNS) from the literature which apply three cases of heat flux boundary conditions: 1. ideal heat flux boundary condition, 2. non-ideal heat flux boundary condition, 3. conjugate heat transfer boundary condition. For low Prandtl number flows LES results show that, despite very good agreement for velocities and mean temperature, predictions of temperature fluctuations may have strong deficiencies if simplified boundary conditions are applied.


1972 ◽  
Vol 94 (1) ◽  
pp. 169-179 ◽  
Author(s):  
E. K. Levy ◽  
G. A. Brown

The performance of a condensing ejector depends on the interactions occurring between the liquid and vapor streams in the mixing section. Axial static and liquid-vapor stagnation pressure profiles were measured in a constant-area mixing section using steam and water over a limited range of inlet vapor conditions and a wide range of inlet liquid velocities. Three flow regimes were identified based on inlet liquid velocity. Complete vapor condensation due to a “condensation shock” occurred only in the High Inlet Liquid Velocity Regime. The presence of supersonic vapor flow was found to be a necessary but not a sufficient condition for the existence of the “condensation shock.” In addition, breakup of the liquid jet was found to play an important role in the mixing section processes. A quasi one-dimensional analytical model of the annular liquid-vapor flow patterns occurring in the upstream portion of the mixing section was formulated. Though it was not possible to predict sufficiently accurately the interfacial heat transfer rates from any currently available analyses or data, interfacial heat transfer coefficients of approximately 100 Btu/sec ft2 deg F were found to produce good agreement between the experimentally measured and computed analytical axial static pressure variations. These values compare favorably with other data on the heat transfer rates to turbulent water jets with condensation.


2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Matt Goodro ◽  
Jongmyung Park ◽  
Phil Ligrani ◽  
Mike Fox ◽  
Hee-Koo Moon

This paper consider the effects of temperature ratio on the heat transfer from an array of jets impinging on a flat plate. At a constant Reynolds number of 18,000 and a constant Mach number of 0.2, different ratios of target plate temperature to jet temperature are employed. The spacing between holes in the streamwise direction X is 8D, and the spanwise spacing between holes in a given streamwise row Y is also 8D. The target plate is located 3D away from the impingement hole exits. Experimental results show that local, line-averaged, and spatially averaged Nusselt numbers decrease as the Twa∕Tj temperature ratio increases. This is believed to be due to the effects of temperature-dependent fluid properties, as they affect local and global turbulent transport in the flow field created by the array of impinging jets. The effect of temperature ratio on crossflow-to-jet mass velocity ratio and discharge coefficients is also examined.


2017 ◽  
Vol 39 (5) ◽  
pp. 41-47 ◽  
Author(s):  
E. N. Zotov ◽  
A. A. Moskalenko A.A. ◽  
O. V. Rasumtseva ◽  
L. M. Protsenko

Existing methods for determining the characteristics of the nonstationary heat transfer process (temperature field, heat transfer coefficient, heat flux density, surface temperature) are considered and analyzed when cooling silver spherical and cylindrical thermo-probes. New analytical solutions are proposed using a special program IQLab, which increase the accuracy of calculations when testing the cooling capacity of various liquids. The results of the calculations are compared with the experimental data.  


2000 ◽  
Author(s):  
Yuwen Zhang ◽  
Amir Faghri

Abstract Condensation in a capillary grooved structure is investigated using the Volume of Fluid (VOF) model. The governing equations are written in a generalized form and are applicable to both liquid and vapor phases. Condensation on the fin top and at the meniscus is modeled by introducing additional source terms in the continuity, VOF, and energy equations. The effects of temperature drop, contact angle, surface tension, and fin thickness on the condensation heat transfer are investigated.


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