Difference between revisions of "Tut Small Study on Conjugate Heat Transfer"

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(Initial and Boundary Conditions)
(Results for the Two Regions Case)
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[[Image:ttt2.png|thumb|Figure 3: Temperature and velocity fields]]
 
[[Image:ttt2.png|thumb|Figure 3: Temperature and velocity fields]]
 
Although the case is laminar, the velocity field has not reached yet a stationary state.
 
Although the case is laminar, the velocity field has not reached yet a stationary state.
 +
Figure 3 left, shows the temperature distribution in the whole field (solid and fluid). It can be noticed a smooth variation at the interface between the solid and fluid domain, represented with a black line. The inlet velocity vectors are shown too.
 +
Figure 3 right, is a representation of the velocity field in the fluid domain and the temperature field in the solid domain. Although the temperature field is more evenly distributed, the velocity is highly unsteady.

Revision as of 12:23, 8 December 2006

1 heatTransfer

1.1 Problem setup

The problem studied is a hot air flow injected into a container coupled with the heat transfer from the flow to and into the container walls. Numerically, at the end, this will be solved in a Large Eddy Simulation framework, with a one equation transport model for the subgrid turbulent kinetic energy.

2 Complete Solution

The first approach was to take into account both domains, and to solve two different sets of equations:

2.1 Compressible fluid flow


\frac{\partial\rho}{\partial t}+\nabla\cdot\rho U=0


\frac{\partial\rho U}{\partial t}+\nabla\cdot\phi U-\nabla\cdot\mu\nabla U=-\nabla p


\frac{\partial\rho h}{\partial t}+\nabla\cdot\phi h=0

2.2 Heat conduction in the solid domain


\frac{\partial T}{\partial t}+k\cdot\Delta T=0

The written solver is called conjHeat, and is based on two other existing OpenFOAM solvers, namely rhoTurbFoam and laplacianFoam (still I have to mention this is a slightly modified version from the one written by Daniele Panara). The sources are accesible through the following link: file sources. The test case consists in a solid can (see Figure 1b), in which a hot fluid (700 K) is injected with 0.1m/s through a small area (green face in Figure 1). The exterior wall surface of the can is kept at a constant temperature of 300 K.

Figure 1: Solid and fluid domains

The case considered here case files is laminar so no turbulence models or subgrid scale models are involved, however the solver is able to compute turbulent flows too (RANS). Thus, the initial values needed to be set are: temperature, velocity, and pressure.

2.3 Initial and Boundary Conditions

For an easier localization, the boundaries are shown in Figure 2:
Figure 2: Boundary Conditions Sketch

The temperature conditions for the fluid domain are set as following: a uniform internal temperature field is set at 700 K as initial value inside the fluid domain; a fixed value of 700 K is set for the fluid interface boundary; temperature at inlet is kept constant at 700 K; at the outlet a zero gradient boundary condition is set for the temperature. In the solid region, the following temperature boundary conditions are set: 600 K uniform internal field as initial condition; 300 K at the walls; zero temperature gradient at the solid surface. The velocity conditions are set only for the fluid domain: a uniform internal velocity field is set at (0, 0, 0.1) m/s as initial value; 0 m/s at the fluid interface; 0.1 m/s at the inlet; zero gradient at the outlet The pressure conditions are set also only for the fluid domain: a uniform internal pressure field is set at 100000 Pa; zero gradient at the fluid interface; zero gradient at inlet; 99990 Pa at outlet. The fluid domain is considered to be filled with air, while the solid domain has a thermal conductivity of 202.5 kg*m/s3/K and a thermal diffusivity of 2.407e-5 m2/s.

2.4 Results for the Two Regions Case

The case was computed for 20 seconds of flow time, and the results are presented in Figure 3.

Figure 3: Temperature and velocity fields

Although the case is laminar, the velocity field has not reached yet a stationary state. Figure 3 left, shows the temperature distribution in the whole field (solid and fluid). It can be noticed a smooth variation at the interface between the solid and fluid domain, represented with a black line. The inlet velocity vectors are shown too. Figure 3 right, is a representation of the velocity field in the fluid domain and the temperature field in the solid domain. Although the temperature field is more evenly distributed, the velocity is highly unsteady.