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

• Isolde Wilde
In summary, the conversation discusses the relationship between the heat given to a DIY alpha type Stirling engine and the motion of the wheel. The efficiency of the engine is mentioned, which is calculated by dividing the work done by the heat given. It is also suggested to connect the engine to a load in order to accurately measure its torque and angular velocity, which can then be used to calculate the output power. Additionally, the use of a graph to analyze the work is mentioned, with suggestions for measuring input power and calculating efficiency.
Isolde Wilde
New user has been reminded to use the Homework Help Template when starting schoolwork threads at the PF
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

Last edited by a moderator:
Isolde Wilde said:
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 (Qh) and the work done by the engine (W) is given by the efficiency (η):

η = W/Qh

This will always be less than the Carnot engine efficiency (ηC = 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

Last edited:
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.

CWatters said:
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

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

Isolde Wilde said:
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.

CWatters said:
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?

## 1. What is a Stirling engine?

A Stirling engine is a type of heat engine that operates by cyclic compression and expansion of air or other gas at different temperature levels. It was invented in the 19th century by Robert Stirling and is known for its high efficiency and low noise levels.

## 2. Why should I build a DIY Stirling engine?

Building a DIY Stirling engine is a fun and educational project that can teach you about thermodynamics, mechanics, and engineering principles. It can also be a cost-effective way to experiment with different designs and materials.

## 3. What materials are needed to build a DIY Stirling engine?

The materials needed for a DIY Stirling engine project can vary depending on the design and size of the engine. However, some common materials include aluminum cans, glass or plastic bottles, copper tubing, steel rods, and a heat source such as a candle or hot water.

## 4. How does a Stirling engine work?

A Stirling engine works by using the expansion and contraction of a gas, such as air, to convert heat energy into mechanical work. The engine has a hot side and a cold side, and as the gas moves between the two sides, it expands and contracts, causing a piston or displacer to move and generate power.

## 5. Are DIY Stirling engines practical for everyday use?

While DIY Stirling engines can be used to power small devices, they are not practical for everyday use as they are not as efficient as other types of engines. However, they can be used for educational purposes, as a hobby, or as a backup power source in emergency situations.

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