Change of temperature in disc brakes

[Davieslad]

Homework Statement

Basically I've got a brake system which i have designed, and i need to calculate if the brake fluid will overheat if the vehicle brakes from its top speed to a halt, and if so at what speed (or how long after braking commences) they will overheat

Brake force = 13000N
Distance = 2500m
Brake rotor radius =0.2m
Brake rotor Surface area (for all 4)= 2.11m^2
Mass of (all 4) rotors = 32kg
Specific heat capacity of the rotor = 1400JKg/K
heat transfer coefficient = 0.5

Homework Equations

w=Q=f.d
Q=mc(T-T)
Q=hA(T-T)

The Attempt at a Solution

Ive made a simulink model using the above formulae, but I am getting the brakes heating up by about 1000 degrees per second, and them cooling by about 0.2 degrees, so I am fairly certain I've made a balls up somewhere.

Can anyone enlighten me as to a good way of solving this?

Cheers

Ed

 

[anathema]

Dear Ed,

Thank you for sharing your brake system design and calculations with us. It seems like you have put a lot of thought and effort into your design and I appreciate your attention to detail. I can offer some suggestions for how to approach this problem and hopefully help you find a solution.

Firstly, it is important to understand the factors that contribute to brake fluid overheating. These include the brake force, distance traveled, and the specific heat capacity and heat transfer coefficient of the brake rotor. It is also important to consider the ambient temperature and any other external factors that may affect the brake system's performance.

Next, I would recommend using the equations you have listed to calculate the amount of heat generated during braking and the rate of heat transfer. It is important to consider the entire system, including all four rotors, as they will all contribute to the overall heat generated. Additionally, the heat transfer coefficient will play a significant role in determining the rate at which the brakes will cool down.

Once you have calculated the heat generated and heat transfer rate, you can use these values to determine the temperature increase of the brake fluid over time. This can be done using the equation Q=mc(T-T), where Q is the heat generated, m is the mass of the brake fluid, c is the specific heat capacity of the brake fluid, and T is the temperature increase over time. This will give you an idea of how quickly the brake fluid will heat up and at what point it may reach a critical temperature.

It is also important to consider the cooling mechanism of your brake system. This could include air flow, cooling fins, or other methods of dissipating heat. By incorporating this into your calculations, you can get a more accurate estimate of the brake fluid's temperature during braking.

I would also recommend conducting some experiments or simulations to validate your calculations and ensure that your brake system is performing as expected. This will give you a better understanding of any potential issues and allow you to make necessary adjustments to your design.

I hope this helps guide you in finding a solution for your brake system. Keep in mind that there are many variables that can affect the performance of your brakes, so it may require some trial and error to find the optimal design. Good luck with your project!

 

[nlightner]

I understand your concern about the potential overheating of the brake system. It is important to consider the change of temperature in disc brakes because high temperatures can affect the performance and safety of the vehicle.

Based on the information provided, I suggest considering the following factors in your analysis:

1. Braking efficiency: The efficiency of the brake system plays a crucial role in determining the amount of heat generated. If the brake system is not efficient, it will require more force to stop the vehicle, resulting in higher temperatures.

2. Material properties: The specific heat capacity and heat transfer coefficient of the brake rotor are important parameters to consider in your calculations. These properties determine how much heat the rotor can absorb and how quickly it can dissipate the heat.

3. Speed and distance: As the vehicle brakes from its top speed to a halt, the distance and time of braking will also affect the temperature change. The longer the distance or the higher the speed, the more heat will be generated.

4. Cooling system: It is important to consider the effectiveness of the cooling system in your brake design. If the cooling system is not efficient, it may not be able to dissipate the heat generated during braking, leading to overheating.

In addition to your calculations, I suggest conducting experiments to validate your results. This will help you identify any potential errors in your model and make necessary adjustments. It is also important to continuously monitor the temperature of the brake system during testing to ensure it stays within safe limits.

Overall, I recommend a thorough analysis of all the above factors to accurately predict the change of temperature in disc brakes and ensure the safety and performance of the vehicle.