Finding the work done by a Stirling Cycle

In summary, when working with an ideal Stirling Cycle engine, W = - ∫pdV gives you theoretical work. For each process, there are specific formulas that apply depending on the situation.
  • #1
TheBigDig
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1. Given the following p-V diagram of an ideal Stirling Cycle, determine the theoretical values of W12, Q12, W34 and Q34 in terms of T1, T2, V1, V2, n (the number of moles) and R (the universal gas constant). Determine the total theoretical p-V work W12341 for the full cycle.2. dU = dQ-Pdv3. I've only just started thermodynamics recently, so my grasp on it is still very weak. I've tried finding W12 using W = -∫pdV but I'm not really sure how that gives me theoretical work. I think I'm supposed to end up with some sort of numerical answer for the final part to compare it with an actual p-V work value and find the efficiency of the Stirling Engine.
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  • #2
TheBigDig said:
I've tried finding W12 using W = -∫pdV but I'm not really sure how that gives me theoretical work.
When you write W12 = - ∫p dV, both p and V are changing from 1 to 2. How about replacing p with something else using the ideal gas law?
 
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  • #3
The working fluid in an ideal Stirling cycle engine goes through four processes :

Compression at constant temperature .
Heat addition at constant volume .
Expansion at constant temperature .
Heat removal at constant volume .

Can you identify the four processes on your diagrams ?

What formulas apply to each process ?

Reading material :

Stirling Cycle
Constant temperature process
Constant volume process
 
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  • #4
Nidum said:
The working fluid in an ideal Stirling cycle engine goes through four processes :

Compression at constant temperature .
Heat addition at constant volume .
Expansion at constant temperature .
Heat removal at constant volume .

Can you identify the four processes on your diagrams ?

What formulas apply to each process ?

Reading material :

Stirling Cycle
Constant temperature process
Constant volume process
Oh thank you! Your response was very illuminating. I hope you don't mind but I'd just like to check I've got this right:
For Isothermal Expansion : W = nRTln[Vf/Vi]
For Isothermal Compression: W = - nRTln[Vf/Vi]
For Heat Addition: Q = nCvΔT
For Heat Removal: Q = - nCvΔT
 

1. What is a Stirling Cycle?

A Stirling Cycle is a thermodynamic cycle that involves the transfer of heat to and from a working fluid, causing it to expand and contract, which in turn produces mechanical work. It is often used in Stirling engines to convert heat energy into mechanical energy.

2. How is work calculated in a Stirling Cycle?

The work done by a Stirling Cycle is calculated by finding the difference between the heat input and heat output of the cycle. This can be represented by the formula W = Qh - Qc, where W is work, Qh is the heat input, and Qc is the heat output.

3. What factors affect the work output of a Stirling Cycle?

The work output of a Stirling Cycle is influenced by several factors, including the temperature difference between the hot and cold reservoirs, the type of working fluid used, and the design and efficiency of the Stirling engine or device.

4. How does the efficiency of a Stirling Cycle compare to other thermodynamic cycles?

The efficiency of a Stirling Cycle is typically lower than other thermodynamic cycles, such as the Carnot Cycle. This is due to the inherent losses in the Stirling engine, such as friction and heat transfer losses. However, Stirling engines can be designed to have high efficiencies, making them a viable alternative to other types of engines.

5. What are some real-world applications of the Stirling Cycle?

The Stirling Cycle has a variety of practical applications, including power generation, cooling and refrigeration, and solar energy conversion. Stirling engines are also used in some types of cryocoolers, which are used to cool materials to extremely low temperatures for scientific and industrial purposes.

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