Challenge

Week 6 - CHT Analysis on a Graphics card

RRahul Kumar26 Aug 2021

CHT Analysis on a Graphics card

Aim

Perform a steady-state conjugate heat transfer analysis on a model of a graphics card. You can use appropriate materials of your choice for the simulation.

Conjugate heat transfer analysis on a graphics card

Problem statement:

Perform a steady-state conjugate heat transfer analysis on a model of a graphics card. You can use appropriate materials of your choice for the simulation. Make sure to properly define the correct solid and fluid zones. Refer the video for further clarification and the model is provided below the video.

Run the simulation for a best possible mesh with a combination of coarse and refined mesh in different regions. Explain the reason for choosing the particular mesh settings.

Objectives:

Run the simulation by varying the velocity from 1m/sec to 5m/sec for at least 3 velocities and discuss the results.

Find out the maximum temperature and heat transfer coefficient attained by the processor.
Prove that the simulation has achieved convergence with appropriate images and plots.
Identify potential hotspots on the model.

Theory:

Conjugate heat transfer:

The Conjugate Heat Transfer (CHT) analysis type allows for the simulation of heat transfer between solid and fluid domains by exchanging thermal energy at the interfaces between them. Typical applications of this analysis type exist as, but are not limited to, the simulation of heat exchangers, cooling of electronic equipment, and general-purpose cooling and heating systems.

Examples:

HVAC, Heat Exchanger, Tank, Internal Combustion Engine, Heat Sink, Boiler, Reactor, Heat Pipe, Turbocharger.

Heat Transfer in a Solid - Conduction: Diffusion of heat due to temperature gradients in solids. A measure of the amount of conduction for a given gradient is heat conductivity. Conduction is described by Fourier’s law defining the conductive heat flux, q, proportional to the temperature gradient

Heat Transfer in a Fluid - Convection: When heat is carried away by moving fluid. The flow can either be caused by external influences, forced convection or by buoyancy forces, natural convection.

Due to the fluid motion, there are three contributions to the heat transfer:

Convective contribution: Depending on the properties of the fluid and its region of flow, the domination of conduction and convection varies.

Viscous effects: Due to the fluid flow, the viscosity creates heat. This effect is often neglected due to its negligible value but should be taken into account for high-velocity cases.

Density effects: When the density becomes related to the temperature, the domain will have different densities at different locations based on the temperature distribution. This variation in density can cause the compression which in-turn generates the heat.

The contemporary conjugate convective heat transfer model was developed after computers came into wide use in order to substitute the empirical relation of proportionality of heat flux to temperature difference with heat transfer coefficient which was the only tool in theoretical heat convection since the times of Newton. This model, based on a strictly mathematically stated problem, describes the heat transfer between a body and a fluid flowing over or inside it as a result of the interaction of two objects. The physical processes and solutions of the governing equations are considered separately for each object in two subdomains. Matching conditions for these solutions at the interface provide the distributions of temperature and heat flux along the body–flow interface, eliminating the need for a heat transfer coefficient. Moreover, it may be calculated using these data.

Applications:

Starting from simple examples in the 1960s, the conjugate heat transfer methods have become a more powerful tool for modeling and investigating natural phenomena and engineering systems in different areas ranging from aerospace and nuclear reactors to thermal goods treatment and food processing, from complex procedures in medicine to atmosphere/ocean thermal interaction in meteorology, and from relatively simple units to multistage, nonlinear processes. A detailed review of more than 100 examples of conjugate modeling selected from a list of 200 early and modern publications shows that conjugate methods are now used extensively in a wide range of applications. That also is confirmed by numerous results published after this book appearance (2009) that one may see, for example, at the Web of Science. The applications in specific areas of conjugate heat transfer at periodic boundary conditions and in exchanger ducts are considered in two recent books.

Geometry setup:

Use Space claim to edit the geometry of the downloaded model of the graphics card which is in the enclosure.

Click on share prep to view any edges in interference so that conformal mesh can be achieved between different components.

Share topology has to be enabled between the different components so that necessary information can be shared between different zones of the mesh.

Mesh setup:

Before generating a base mesh, let's name the different components of the graphic card so it is easier to find them while setting up fluent.

Base, processor and fins are basic name selections which will help us in the simulation.

Click generate mesh to create a base mesh, body sizing can be applied for the 3 solid components.

after creating body sizing for the 3 components, generate mesh as that it is considered as a base mesh having near about 0.5 million elements which help us in finding accurate solutions.