How Does Heat Affect the Motion of a DIY Stirling Engine's Wheel?

[Isolde Wilde]

hello,
I had made an DIY alpha type Stirling engine for my physics project and now I have to write an report about the relationship between the heat given to the engine and the motion of the wheel.

I had searched a lot about Stirling engines and I learned about work, energy, efficiency, thermodynamics and rotational motion but I don't know which of this I should use to find the relationship of the heat given and the motion of the wheel.

can you please help me about which formulas I should use for my report
thank you

 

[Andrew Mason]

hello,
I had made an DIY alpha type Stirling engine for my physics project and now I have to write an report about the relationship between the heat given to the engine and the motion of the wheel.

I had searched a lot about Stirling engines and I learned about work, energy, efficiency, thermodynamics and rotational motion but I don't know which of this I should use to find the relationship of the heat given and the motion of the wheel.

can you please help me about which formulas I should use for my report
thank you

Hi Isolde. Welcome to PF!

The relationship between the heat delivered to the engine (Q_h) and the work done by the engine (W) is given by the efficiency (η):

η = W/Q_h

This will always be less than the Carnot engine efficiency (η_C = 1-Tc/Th where Th and Tc are temperatures of the hot and cold reservoirs that the engine operates between). This page may help you determine that efficiency. Good luck with your project!

AM

 

[CWatters]

Was your Stirling engine driving a load or just a flywheel? Ideally you would connect it to a load and measure the torque and rpm it produced so you can work out the output power. Then you can calculate the efficiency.

 

[Isolde Wilde]

Was your Stirling engine driving a load or just a flywheel? Ideally you would connect it to a load and measure the torque and rpm it produced so you can work out the output power. Then you can calculate the efficiency.

it has a flywheel but I didn't get what you said about torque, is there a formula for that?
thank you

 

[Isolde Wilde]

and I have to make different measurements and I have to use a graph to analyze the work but which graphs should I use?
thanks again

 

[CWatters]

it has a flywheel but I didn't get what you said about torque, is there a formula for that?
thank you

If it was only turning a flywheel then the only load on the engine is that due to air resistance and friction, so the efficiency is effectively zero.

If you connect the output to a brake or similar load then the power going into the load is given by...

Output Power = torque * angular velocity

You need to measure the angular velocity and torque. Angular velocity can be measured using an optical rpm meter and some calculations. Torque can be measured a number of ways one of which is to use a beam balance.

 

[Isolde Wilde]

If it was only turning a flywheel then the only load on the engine is that due to air resistance and friction, so the efficiency is effectively zero.

If you connect the output to a brake or similar load then the power going into the load is given by...

Output Power = torque * angular velocity

You need to measure the angular velocity and torque. Angular velocity can be measured using an optical rpm meter and some calculations. Torque can be measured a number of ways one of which is to use a beam balance.

Would it be right if I use torque and angular velocity to find the output power and use the slope of the p vs v diagram for the input power and find the efficiency using those two?