Thermodynamics problem, calculate energy transfer?

In summary, the amount of energy transfer by work from the steam on the piston during the process is 2590 kJ.
  • #1
kawf
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Homework Statement



A mass of 5 kg of steam is contained within a piston cylinder assembly. The steam undergoes an expansion from its initial state with e1 = 3000 kJ/kg to its final state with e2 = 2500 kJ/kg. During the process there is a heat transfer of 80 kJ to the steam. Also, a paddle wheel transfers 10 kJ of work to the steam. Calculate the amount of energy transfer by work from the steam on the piston during the process.

Homework Equations



dE = del Q - del W

The Attempt at a Solution



Would this be correct?
W = del Q - dE
= (80kJ + 10kJ) - (2500 kJ/kg - 3000 kJ/kg)
W = 590 kJ

I don't believe this is correct but it's all I have been able to come up with so far. Any guidance is appreciated
 
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  • #2
Determining ΔE
[tex]\Delta \hat{E} = 2500 \frac{kJ}{kg} - 3000 \frac{kJ}{kg} = -500 \frac{kJ}{kg}[/tex]
[tex]\Delta E = 5 \ kg \left( - 500 \frac{kJ}{kg} \right) = -2500 \ kJ[/tex]
Now, applying an energy balance on the cylinder (1st Law of Thermodynamics)
[tex]\Delta E = Q + W_s - W[/tex]
Where Ws is the work input by the paddle wheel and W is the work output on the piston. Finally
[tex]W = Q + W_s - \Delta E = 80 \ kJ + 10 \ kJ - (-2500 \ kJ) = 2590 \ kJ[/tex]
 

1. What is thermodynamics?

Thermodynamics is the branch of physics that deals with the study of the relationships between heat, energy, and work. It explains how energy is transferred between different forms and how it affects the properties of matter.

2. What is energy transfer?

Energy transfer is the movement of energy from one system to another. In thermodynamics, energy transfer can occur through heat, work, or a combination of both.

3. How do you calculate energy transfer in a thermodynamics problem?

To calculate energy transfer, you need to know the initial and final states of the system, as well as the amount of heat and work involved. The energy transfer can be calculated using the first law of thermodynamics, which states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system.

4. What are the different types of energy transfer in thermodynamics?

The two main types of energy transfer in thermodynamics are heat and work. Heat is the transfer of thermal energy from a hotter object to a colder object, while work is the transfer of energy due to a force acting on an object.

5. Can energy transfer be reversed in a thermodynamic process?

Yes, energy transfer can be reversed in a thermodynamic process. This is known as a reversible process, where the system returns to its initial state after the process is completed. In contrast, an irreversible process involves a permanent change in the system and cannot be reversed.

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