scholarly journals GAM-HEAT: A computer code to compute heat transfer in complex enclosures. Revision 2

1992 ◽  
Author(s):  
R.E. Cooper ◽  
J.R. Taylor
Keyword(s):  
Heat Transfer ◽  
Computer Code

A Computational Study of the Interaction of Melting Soil With Moisture Transport in the Native Soil

1998 ◽  
Author(s):  
Will Schreiber ◽  
John Kuo
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Moisture Transport ◽  
Moving Boundary ◽  
Computational Study ◽  
Fluid Motion ◽  
Computer Code ◽  
General Purpose ◽  
Simple Method ◽  
Porous Soil

Abstract The current paper describes a computer model designed to analyze the moisture transport in the unmelted, porous soil neighboring a convecting melt. The time-dependent fluid and heat flow in the soil melt is simulated implicitly using the SIMPLE method generalized to predict viscous fluid motion and heat transfer on boundary-fitted, non-orthogonal coordinates which adapt with time. TOUGH2, a general-purpose computer code for multiphase fluid and heat flow developed by K. Pruess at Lawrence Berkekey Laboratory, has been modified for use on time-adaptive, boundary-fitted coordinates to predict heat transfer, moisture and air transport, and pressure distribution in the porous, unmelted soil. The soil melt model is coupled with the modified TOUGH2 model via an interface (moving boundary) whose shape is determined implicitly with the progression of time. The computer model’s utility is demonstrated in the present study with a special two-dimensional study. A soil initially at 20°C and partially-saturated with either a 0.2 or 0.5 relative liquid saturation is contained in a box two meters wide by ten meters high with impermeable bottom and sides. The upper surface of the soil is exposed to a 20°C atmosphere to which vapor and air can escape. Computation begins when the soil, which melts at 1700°C, is heated from one side (maintained at constant temperatures ranging from 1700°C to 4000°C). Heat from the hot wall causes the melt to circulate in such a way that the melt interface grows more rapidly at the top of the box than at the bottom. As the upper portion of the melt approaches the impermeable wall it creates a bottle neck for moisture release from the soil’s lower regions. The pressure history of the trapped moisture is examined as a means for predicting the potential for moisture penetration into the melt. The melt’s interface movement and moisture transport in the unmelted, porous soil are also examined.

scholarly journals Effect of the size of graded baffles on the performance of channel heat exchangers

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 767-775 ◽  
Author(s):  
Djamel Sahel ◽  
Houari Ameur ◽  
Touhami Baki
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchangers ◽  
Computer Code ◽  
Channel Length ◽  
Heat Transfer Characteristics ◽  
Enhancement Of Heat Transfer ◽  
Transfer Rates ◽  
Flow And Heat Transfer ◽  
Friction Factors

The baffling technique is well-known for its efficiency in terms of enhancement of heat transfer rates throught channels. However, the baffles insert is accompanied by an increase in the friction factor. This issue remains a great challenge for the designers of heat exchangers. To overcome this issue, we suggest in the present paper a new design of baffles which is here called graded baffle-design. The baffles have an up- or down-graded height along the channel length. This geometry is characterized by two ratios: up-graded baffle ratio and down-graded baffle ratio which are varied from 0-0.08. For a range of Reynolds number varying from 104 to 2 ? 104, the turbulent flow and heat transfer characteristics of a heat exchanger channel are numerically studied by the computer code FLUENT. The obtained results revealed an enhancement in the thermohydraulic performance offered by the new suggested design. For the channel with a down-graded baffle ratio equal to 0.08, the friction factors decreased by 4-8%

scholarly journals Prediction of Unshrouded Rotor Blade Tip Heat Transfer

1995 ◽  
Author(s):  
A. A. Ameri ◽  
E. Steinthorsson
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Stokes Equations ◽  
Space Shuttle ◽  
Suction Side ◽  
Computer Code ◽  
Turbine Rotor ◽  
High Rate ◽  
Blade Surface ◽  
Blade Tip

The rate of heat transfer on the tip of a turbine rotor blade and on the blade surface in the vicinity of the tip, was successfully predicted. The computations were performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations using an efficient multigrid method. The case considered for the present calculations was the SSME (Space Shuttle Main Engine) high pressure fuel side turbine. The predictions of the blade tip heat transfer agreed reasonably well with the experimental measurements using the present level of grid refinement. On the tip surface, regions with high rate of heat transfer was found to exist close to the pressure side and suction side edges. Enhancement of the heat transfer was also observed on the blade surface near the tip. Further comparison of the predictions was performed with results obtained from correlations based on fully developed channel flow.

Flow Pattern and Heat Transfer in a Closed Rotating Annulus

1994 ◽  
Vol 116 (3) ◽  
pp. 542-547 ◽  
Author(s):  
D. Bohn ◽  
G. H. Dibelius ◽  
E. Deuker ◽  
R. Emunds
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Side Wall ◽  
Computer Code ◽  
Turbine Rotor ◽  
Base Case ◽  
Convection Flow ◽  
Coriolis Forces ◽  
R Ratio ◽  
Temperature Levels

The prediction of the temperature distribution in a gas turbine rotor containing gasfilled closed cavities, for example between two disks, has to account for the heat transfer conditions encountered inside these cavities. In an entirely closed annulus no forced convection is present, but a strong natural convection flow occurs induced by a nonuniform density distribution in the centrifugal force field. A computer code has been developed and applied to a rotating annulus with square cross section as a base case. The co-axial heat flux from one side wall to the other was modeled assuming constant temperature distribution at each wall but at different temperature levels. Additionally the inner and outer walls were assumed to be adiabatic. The code was first verified for the annulus approaching the plane square cavity in the gravitational field, i.e., the ratio of the radius r over the distance h between outer and inner cylindrical wall was set very large. The results obtained agree with De Vahl Davis’ benchmark solution. By reducing the inner radius to zero, the results could be compared with Chew’s computation of a closed rotating cylinder, and again good agreement was found. Parametric studies were carried out varying the Grashof number Gr, the rotational Reynolds number Re, and the r/h ratio, i.e., the curvature of the annulus. A decrease of this ratio at constant Gr and Re number results in a decrease of heat transfer due to the Coriolis forces attenuating the relative gas velocity. The same effect can be obtained by increasing the Re number with the h/r ratio and the Gr number being constant. By inserting radial walls into the cavity the influence of the Coriolis forces is reduced, resulting in an increase of heat transfer.

Analysis of a Convection Loop for GFR Post-LOCA Decay Heat Removal

2004 ◽  
Author(s):  
Wesley C. Williams ◽  
Pavel Hejzlar ◽  
Pradip Saha
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Flow Regime ◽  
Natural Circulation ◽  
Heat Removal ◽  
Computer Code ◽  
Steady State Analysis ◽  
Decay Heat ◽  
Cooling Loops ◽  
State Analysis

A computer code (LOCA-COLA) has been developed at MIT for steady state analysis of convective heat transfer loops. In this work, it is used to investigate an external convection loop for decay heat removal of a post-LOCA GFR. The major finding is that natural circulation cooling of the GFR is feasible under certain circumstances. Both helium and CO2 cooled system components are found to operate in the mixed convection regime, the effects of which are noticeable as heat transfer enhancement or degradation. It is found that CO2 outperforms helium under identical natural circulation conditions. Decay heat removal is found to have a quadratic dependence on pressure in the laminar flow regime and linear dependence in the turbulent flow regime. Other parametric studies have been performed as well. In conclusion, convection cooling loops are a credible means for GFR decay heat removal and LOCA-COLA is an effective tool for steady state analysis of cooling loops.

Numerical Modeling of Heat Transfer and Phase Transition in Programming the Ovonic Unified Memory Cells

2005 ◽  
Author(s):  
Evan Small ◽  
Sadegh M. Sadeghipour ◽  
Mehdi Asheghi
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Diffusion Equation ◽  
Dynamic Range ◽  
Semiconductor Device ◽  
Computer Code ◽  
Drift Diffusion ◽  
Thermally Induced ◽  
Design And Optimization ◽  
Phase Prediction

An Ovonic Unified Memory (OUM) cell is a semiconductor device that stores data by a thermally induced phase transition between polycrystalline (set) and amorphous (reset) states in a thin film of chalcogenide alloy. The small volume of active media acts as a programmable resistor switching between a high (amorphous) and low (crystalline) resistance state. The change in the film resistivity (>40X dynamic range) caused by this rapid, reversible structural change is measured to detect the state of the cell (set or reset) for read out. OUM can benefit from a simulator capable of predicting the electrical, thermal, and crystallization behavior for design and optimization, particularly at the present stage of the development. This paper reports on the efforts being made to prepare such a numerical simulator, using an existing finite element computer code as the source for thermal and electrical modeling, and a custom crystallization code for phase prediction. Heat generation in the device is by Joule heating and is achieved by passage of the electric current, which is obtained from the electrical simulation. This result appears in the heat source term of the heat transfer equation that is solved for thermal modeling. As the first attempt the Ohmic current-voltage relation was implemented successfully to simulate set and reset in a two dimensional model of OUM. Solution of the drift-diffusion equation is now underway to capture the semiconductor behavior of the I-V curve. A good progress is made however, still more works needs to be done to fully implement the drift diffusion equation.

scholarly journals Impingement/Effusion Cooling: The Influence of the Number of Impingement Holes and Pressure Loss on the Heat Transfer Coefficient

1989 ◽  
Author(s):  
A. M. Al Dabagh ◽  
G. E. Andrews ◽  
R. A. A. Abdul Husain ◽  
C. I. Husain ◽  
A. Nazari ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Pressure Loss ◽  
Computer Code ◽  
Relative Pressure ◽  
Impingement Jet ◽  
Small Influence ◽  
Internal Aerodynamics ◽  
The Heat Transfer Coefficient

Measurements of the overall heat transfer coefficient within an impingement/effusion cooled wall are presented. The FLUENT CFD computer code has been applied to the internal aerodynamics to demonstrate the importance of the internal recirculation in the impingement gap. This generates a convective heat transfer to the impingement jet and measurements of this heat transfer plate coefficient are presented that show it to be approximately a half of the impingement/effusion heat transfer coefficient. The influence of the relative pressure loss or X/D between the impingement and effusion was investigated, for an effusion X/D of 4.67 and a Z of 8 mm, and shown to be only significant at high G where a reduction in h of 20% occurred. Increasing the number of holes, N, in the impingement/effusion array at a constant Z of 8 mm reduced h by 20%, mainly due to the higher Z/D for the smaller holes at high N. Reduced numbers of impingement holes relative to the effusion holes, in a ratio of 1 to 4, were shown to have a small influence on h with a maximum reduction in h of 20% at high G and a negligible effect at low G.

Parametric Study of Phase Change Suspension Flow in Microchannels

2003 ◽  
Author(s):  
Y. L. Hao ◽  
Y.-X. Tao
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Phase Change ◽  
Flow Condition ◽  
Computer Code ◽  
Cfd Modeling ◽  
Transfer Coefficients ◽  
Circular Duct ◽  
Heat Transfer Coefficients ◽  
Melting Region

A continuum model is applied to the numerical simulation of the laminar hydrodynamic and heat-transfer characteristics of suspension with phase change material (PCM) particles in a microchannel. The analytical/numerical formulation based on CFD modeling technique, and the computer code is developed. Local wall-to-suspension heat transfer coefficients are calculated by the simultaneous solution of the conservation of mass, momentum and thermal energy equations. By providing detailed information on the local behavior of the wall-to-suspension heat transfer coefficients, preliminary calculations expose that there exists a particle-depleted layer next to the wall under the laminar flow condition. It plays an important role on the heat transfer between the suspension and the wall under the laminar flow condition. The heat transfer coefficient increases and reaches a peak value in the melting region. The benefits on the enhancement of heat transfer and the reduction of wall temperature and mean temperature by employing the MCPCM particle are mainly in the melting region. The preliminary results agree very well with the experimental observations and measurement on the flow and heat transfer of microencapsulated PCM slurry in circular duct. It interprets the observation in the literature where heat transfer between the suspension and the wall is weaker in non-melting region and melted region than that between the pure fluid and the wall for laminar flow conditions.

A New Numerical Procedure for Coupling Radiation in Participating Media With Other Modes of Heat Transfer

2005 ◽  
Vol 127 (9) ◽  
pp. 1037-1045 ◽  
Author(s):  
Sandip Mazumder
Keyword(s):  
Heat Transfer ◽  
Energy Equation ◽  
Numerical Procedure ◽  
Computer Code ◽  
Point Of View ◽  
Stability And Convergence ◽  
Participating Media ◽  
Solution Approach ◽  
Coupling Approach ◽  
Coupled Solution

Traditionally, radiation in participating media is coupled to other modes of heat transfer using an iterative procedure in which the overall energy equation (EE) and the radiative transfer equation (RTE) are solved sequentially and repeatedly until both equations converge. Although this explicit coupling approach is convenient from the point of view of computer code development, it is not necessarily the best approach for stability and convergence. A new numerical procedure is presented in which the EE and RTE are implicitly coupled and solved simultaneously, rather than as segregated equations. Depending on the average optical thickness of the medium, it is found that the coupled solution approach results in convergence that is between 2–100 times faster than the segregated solution approach. Several examples in one- and two-dimensional media, both gray and nongray, are presented to corroborate this claim.

Validation of the Isis-3D Computer Code for Simulating Large Pool Fires Under a Variety of Wind Conditions

2003 ◽  
Author(s):  
Miles Greiner ◽  
Ahti Sou-Anttila
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Temperature Response ◽  
Diffuse Radiation ◽  
Computer Code ◽  
Time Dependent ◽  
Fuel Vapor ◽  
View Factor ◽  
Pool Fires ◽  
Fuel Evaporation

The Isis-3D computational fluid dynamics/radiation heat transfer code was developed to simulate heat transfer from large fires. It models liquid fuel evaporation, fuel vapor and oxygen transport, chemical reaction and heat release, soot and intermediate species formation/destruction, diffuse radiation within the fire, and view factor radiation from the fire edge to nearby objects and the surroundings. Reaction rate and soot radiation parameters in Isis-3D have been selected based on experimental data. One-dimensional transient conduction modules calculate the response of simple objects engulfed in and near the flames. In this work, Isis-3D calculations were performed to simulate the conditions of three experiments that measured the temperature response of a 4.66-m-diameter culvert pipe located at the leeward edge of 18.9-m and 9.45-m diameter pool fires in crosswinds with average speeds of 2.0, 4.6 and 9.5 m/s. The measured wind conditions were used to formulate time-dependent velocity boundary conditions for a rectangular Isis-3D domain with 16,500 nodes. Isis-3D accurately calculated characteristics of the time-dependent temperature distributions in all three experiments. Accelerated simulations were also performed in which the pipe specific heat was reduced compared to the measured value by a factor of four. This artificially increased the speed at which the pipe temperature rose and allowed the simulated fire duration to be reduced by a factor of four. A 700 sec fire with moderately unsteady wind conditions was accurately simulated in 10 hours on a 2.4 GHz LINUX workstation with 0.5 GB of RAM.

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