Week 10 - Simulating Combustion of Natural Gas.

Aim:-
Perform the heat transfer analysis using ANSYS-Fluent software for the cylindrical
Lithium ion Battery with heat generation boundary condition. Create an enclosure and
use air as the working fluid for cooling the battery back system (4 x 2). Take air inlet
temperature as 300 K and gap between the batteries as 2 mm.
Property of the Lithium-ion Battery
Density = 2700 kg/m3
Specific heat = 900 J/kg.K
Thermal Conductivity = 7.14 W/m.K
Heat Generation per battery = 10 W
Size of the Battery = 18 mm diameter and 65 mm height.
Expected results:
• Explain why battery cooling is needed. And give a brief description about various
techniques for battery cooling.
• Perform Mesh independent study for any one case and based on your judgment
use the more suitable model for further cases.
• Run the simulation by varying the velocity of air as 3, 5 and 10m/sec and discuss
the results.
• Find out the maximum temperature and heat transfer coefficient obtained by the
battery.
• Based on the results and on your judgment, select one case (3, 5 or 10 m/s) and
vary the space between the batteries as 2, 4 and 6 mm, then discuss the results.
• Prove that the simulation has achieved convergence with appropriate images and
plots (Velocity and temperature contour plots on the cut planes).
• Create the animation to observe the temperature distribution and velocity vector.
• Summarize the results in tabulation/ graphical form.
• Identify potential hotspots on the model.
• State the inferences based on the result

Objective:- Simulation for 4*2 battery arrangment.

Theroy:-

BTMS:- BTMS sends for battery thermal management system.

The rise of renewable power generation in the current energy market has created an immense potential for different forms of energy storage. At the forefront of these storage technologies are the lithium batteries as they are lightweight with high energy density. The characteristics of Lithium batteries have made them attractive both for stationary and automotive applications. However, despite their promising future, there are major hindrances with regards to a battery system e.g. safety concerns, cost, limited calendar life, and temperature related issues. Temperature has a large effect on the safety, lifetime and performance of Li-ion batteries. The optimum operating range for these batteries is 15-35⁰C [1] otherwise the performance and lifespan will be reduced and furthermore hazardous incidents such as thermal runaway might occur. In addition, temperature difference among cells and modules in a battery pack must be controlled, else it will impact the operation and aging of the battery. Thus, an effective battery thermal management system is necessary to dissipate the heat generated inside the batteries.Moreover, in low-temperature scenarios, heating is required to ensure the best performance.

Li-ion batteries
Li-ion batteries consist of lithium in the positive electrode and electrolyte where lithium ions move from positive to negative electrode during charging and vice versa during discharge. What gives leverage to lithium-ion batteries compared to other battery technologies is their volumetric and mass energy density. This feature makes lithium-ion batteries very attractive for different applications, especially the automotive industry where the energy density is critical. Lithium Batteries are manufactured in three different form factors namely cylindrical, prismaticand pouch. In cylindrical cells, the layers are rolled and put into a cylindrical can Figure 1. The advantage of this cell format is mechanical stability and ease of manufacturing. Prismatic cell Figure 12 is wrapped in packages for thinner design demands. They are mainly found in electronic devices such as mobile phones. Pouch cells have the most efficient packaging by eliminating the metal enclosure and allow stacking.

BTMS:- the inappropriate battery temperature will have a negative impact on the performance, lifetime and safety of the batteries. Therefore, a BTMS is required for every battery system. The primary duty of a BTMS is to keep the batteries in the optimum temperature range and maintain an even temperature distribution in the battery pack. Afterward, other factors such as weight, size, reliability and the cost must be taken into consideration based on the application of the battery packs

1. air cooling

Air is the most conventional way for cooling and has been used widely in various industries. Due to low heat capacity and low thermal conductivity, air might not seem to be a good cooling

2. liquid cooling

Liquid coolants have several advantages compared to air. Liquid cooling is more compact thanair without sacrificing any cooling capacity. Liquid coolants can be 3500 times more efficient

2.1 Direct Liquid cooling

2.2 Indirect liquid cooling

3. phase change material(pcm)

in this type of cooling we uses wax o any phase changing material to observe heat from the battery and to relaease this heat to the surroundings.

CFD:-Computational fluid dynamics or CFD is the analysis of systems involving fluid flow, heat transfer and associated phenomena such as chemical reactions by means of computer-based simulation.

Practical application in current scenario

• aerodynamics of aircraft and vehicles: lift and drag
  • hydrodynamics of ships
  • power plant: combustion in internal combustion engines and gas
  turbines
  • turbomachinery: flows inside rotating passages, diffusers etc.
  • electrical and electronic engineering: cooling of equipment including
  microcircuits
  • chemical process engineering: mixing and separation, polymer moulding
  • external and internal environment of buildings: wind loading and
  heating/ventilation
  • marine engineering: loads on off-shore structures
  • environmental engineering: distribution of pollutants and effluents
  • hydrology and oceanography: flows in rivers, estuaries, oceans
  • meteorology: weather prediction
  • biomedical engineering: blood flows through arteries and veins

CFD Work Flow:- CFD codes are structured around the numerical algorithms that can tackle fluid flow problems. In order to provide easy access to their solving power all commercial CFD packages include sophisticated user interfaces to input problem parameters and to examine the results

Its threee step process
(i) a pre-processor

involves defination of geometry, grid generation, selection of phenomenon that need to model

(ii) a solver

intergration of governing equation, discretisation and solution

(iii) a post-processor

ploting of contour, graphs and making movies.

In solving fluid flow problems we need to be aware that the underlyingphysics is complex and the results generated by a CFD code are at best asgood as the physics (and chemistry) embedded in it and at worst as good asits operator with CFD

Solving and Modeling Approch:-

There are no way present to understand and analyse the effeciveness of the mixiing tee model.

1. analytical approch

2. simulation approch

3. experimental approch

using analytical approch and experimental approch is time consuming and high cost senario. this could be eliminated by using simulation approch in which we can analyse the system with the actual codition we are intrested in.

To do this we are using ansys fluent solver

we are using fluid flow analysis using Fluent solver because we are interested in the total effectiveness of the fluid in the mechnical tee model, here we are using two different models to analyse the effectiveness of the mixing of fluid.

Approch we are using.

1. We need to open Ansys workbench

2. Choose the Appropiate Solver

3. Assign Appropiate name

4. Choose geometry and select new spaceclaim model.

5. Load the appropiate file

6. Implement the geometrical operation

7. Apply the mesh and provide name selection

8. Choose setup, select the appropiate model

9. Initalisation and running the simulation

10. Result making i.e. countour plots graphs

1. Opening Ansys workbench

2. Choose the Appropiate Solver

1. choose default mesh length as 3 mm and 5mm respectively

2. Now Create inflation layer

3. Now give name selection.

6. Setup:-

Settings

Solver	Steady State
Energy Equation	On
Model	k-omega sst
Inlet	Inlet
Outlet	Pressure Outlet
Material_(Fluid)	Air, Alluminium lithium(user defined)
Cell Zone Condition	lithium, alluminium

cases and inputs:-

Sr No	Mesh Length in mm	Gap in mm	Velocity in m/s
1	3	2	3
2	3	2	5
3	3	2	6
4	3	4	3
5	3	6	3
6	5	2	3

Results:-

# Keeping mesh length and gap constant and varrying the velocity.

1. residuals

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 2 velocity 5	Mesh length 3, gap 2 velocity 10

2. temprature

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 2 velocity 5	Mesh length 3, gap 2 velocity 10

3. htc

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 2 velocity 5	Mesh length 3, gap 2 velocity 10

4. temprature contour

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 2 velocity 5	Mesh length 3, gap 2 velocity 10

5. velocity contour

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 2 velocity 5	Mesh length 3, gap 2 velocity 10

6. result ss

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 2 velocity 5	Mesh length 3, gap 2 velocity 10

# Keeping velocity and mesh length constant and varrying the gap .

1. residual

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 4 velocity 3	Mesh length 3, gap 6 velocity 3

2. temprature

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 4 velocity 3	Mesh length 3, gap 6 velocity 3

3. htc

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 4 velocity 3	Mesh length 3, gap 6 velocity 3

4. temprature contour

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 4 velocity 3	Mesh length 3, gap 6 velocity 3

5. velocity contour

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 4 velocity 3	Mesh length 3, gap 6 velocity 3

6. result ss

Mesh length 3, gap 2 velocity 3	Mesh length 3, gap 4 velocity 3	Mesh length 3, gap 6 velocity 3

# mesh independent study

1. residual

Mesh length 3, gap 6 velocity 3	Mesh length 5, gap 6 velocity 3

2. temprature

Mesh length 3, gap 6 velocity 3	Mesh length 5, gap 6 velocity 3

3. htc

Mesh length 3, gap 6 velocity 3	Mesh length 5, gap 6 velocity 3

4. temprature countor

Mesh length 3, gap 6 velocity 3	Mesh length 5, gap 6 velocity 3

5. velocity countor

Mesh length 3, gap 6 velocity 3	Mesh length 5, gap 6 velocity 3

6. result

Mesh length 3, gap 6 velocity 3	Mesh length 5, gap 6 velocity 3

# transient

We have also performed the transient case study for the gap value of 4mm and velocity, 10 m/s to
visualise the change in temperature w.r.t. time.

Conclusion:-

1. higher will the veloity of air higher will be the heat rejected from the battery.

	3m/s	5m/s	10m/s
htc(W/m^2Kk	35.35	47.81	69.31
average temp(k)	358.82	339.65	322.88
maximum(k)	381.54	352.90	329.35
minimum(k)	35.35	322.38	324.86

2. larger wiill the gap between battery cell higher will be the heat rejected from the battery.

	2mm	4mm	6mm
htc(W/m^2Kk	35.35	41.38	42.911
average temp(k)	358.82	347.27	345.12
maximum(k)	381.54	359.06	356.21
minimum(k)	355.35	330.80	329.71

we can see that from battery gap from 2 to 4 mm we can see a large changes but when we compare 4 and 6mm there is no such variation observed.

we cannot increase gap between battery more because it will increase the space as well as battery weight.

3. when we perform mesh independent study we always found good result with finner mesh

Refrences

https://cfdflowengineering.com/battery-cooling-techniques-in-electric-vehicle