Challenge

Week 6 - CHT Analysis on a Graphics card

BB Bharath Kumar16 Mar 2022

Aim: To perform CHT analysis on Graphics card.

Objectives:

Perform Simulations by varying the velocity from 1 to 5 m/s for a minimum of 3 values.
Find the Max Temperature and Heat Transfer Coefficient of the system
Prove Convergence of the simulation by using plots and graphs.
Identify hotspots on the object.

Theory:

CHT stands for Conjugate Heat Transfer Analysis. This type of analysis allows for simulation of heat transfer between Solids and Fluids by an interchange of thermal energy at its interfaces.

CHT analysis is used to create simulations of heat exchangers, cooling of electronic equipment and general-purpose air-conditioning devices

They are also used in determining the outcomes of

Heat Transfer coefficient Analysis
Heat Flux analysis
CFD Thermal Analysis
Temperature Distribution Analysis

There are three contributions to heat transmission due to fluid motion:

Convective Contribution:The dominance of conduction and convection changes depending on the fluid's characteristics and its flow zone.

Viscous Effects:The viscosity generates heat as a result of the fluid flow. Because of its small magnitude, this impact is frequently overlooked, but it should be considered in high-velocity scenarios.

Density Effects: When density and temperature are linked, the domain will have various densities at different points depending on the temperature distribution. This difference in density can result in compression, which creates heat.

After computers became widely used, the modern conjugate convective heat transfer model was developed to replace the empirical relation of proportionality of heat flux to temperature difference with the heat transfer coefficient, which had been the only tool in theoretical heat convection since Newton's time. The heat transfer between a body and a fluid running over or inside it as a result of the contact of two objects is described by this model, which is based on a rigorously mathematically defined issue. Each object's physical processes and governing equation solutions are addressed individually in two subdomains. The distributions of temperature and heat flux along the body–flow interface are provided by matching conditions for these solutions at the interface, obviating the necessity for a heat transfer coefficient. Furthermore, it is possible to compute it using these facts.

Geometry Setup:

The downloaded geometry is edited in Spaceclaim
The option 'Share' is used to attain conformal mesh between the components.
Share topology is to be enabled so that the necessary information can be transferred between the cell-zones.

Mesh Setup:

All the components are to named, so it is easy to setup in Fluent.
Body sizing is to be applied to each and every named selection to obtain proper meshing.
Baseline mesh is generated, which is to have hundred thousand elements to have an accurate solution.
After mesh is setup, exit 'Meshing' to open Fluent.

Enclosure.

Graphic card setup.

Base.

Processor.

Fins.

Fluent Setup:

This experiment is conducted on Fluent.

Setting up Physics for CHT analysis on Fluent.

Steady-state, Pressure based Solver.
Absolute velocity.
Energy equations are used
Viscous K-omega Model is used.

Materials:

Materials for each named selection is shown in the dialog box below.

Name	Density (kg/m^3)	Specific Heat(J/kg-K)	Thermal Conductivity(W/m-K)
Copper	8978	381	387.86
Silica	2328	710	150
Steel	8050	502	16.27

Air is used used as fluid medium.

Density:1.225 kg/m^3

Viscosity: 1.7894e-05 kg/ms

Setting Up Source Terms:

In this case, Processor is a source of heat. So, we have to assign a value of heat generated by the processor through 'Source terms' option.
to setup source terms, Go to Cell-zone conditions-processor and enable source terms.

Step-1: Baseline Mesh:

Velocity: 1m/s

Mesh:

Enclosure: 3.9mm

Fins: 2 mm

Processor: 1.5 mm

Base: 2 mm